INS

UniProt ID: P01308
Organism: Homo sapiens
Review Status: COMPLETE
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Gene Description

Insulin is a 51-amino acid peptide hormone composed of two polypeptide chains (A-chain and B-chain) linked by disulfide bonds. It is synthesized as preproinsulin in pancreatic beta cells, processed through the secretory pathway to generate mature insulin, and secreted into the extracellular space in response to elevated blood glucose. The primary core function of insulin is regulation of glucose homeostasis through binding to the insulin receptor, triggering intracellular signaling cascades (primarily PI3K/AKT and MAPK pathways) that stimulate glucose uptake in muscle and adipose tissue, suppress hepatic glucose production, promote glycogen synthesis, stimulate lipogenesis, and inhibit lipolysis and protein degradation. Beyond its metabolic roles, insulin has important functions in cell growth, proliferation, and neuroprotection.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0005158 insulin receptor binding
IBA
GO_REF:0000033 		ACCEPT
Summary: This annotation represents the core molecular function of insulin - specific binding to the insulin receptor. The deep research extensively documents insulin-receptor interactions, including the two-site binding model with site-1 (high affinity, Kd ~10-30 nM) formed by L1 domain and αCT domain, and site-2 (lower affinity). Structural studies have revealed the stepwise activation mechanism involving conformational transitions from Λ-shaped to Γ-shaped to T-shaped receptor states upon insulin binding.
Reason: This is the primary and most specific molecular function term for insulin. The IBA evidence is well-supported by extensive structural and biochemical data showing insulin's high-affinity and specific binding to the insulin receptor. This annotation accurately captures the core molecular activity of the protein.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
Insulin binding to site-1, the primary insulin-binding site, is composed of the L1 domain of one α-subunit and the αCT domain of the adjacent α-subunit; insulin binds to this site with high affinity (Kd approximately 10-30 nanomolar)
file:human/INS/INS-deep-research-perplexity.md
The binding of insulin to its extracellular receptor leads to rapid and sequential autophosphorylation of multiple tyrosine residues distributed across different domains of the intracellular region
file:human/INS/INS-deep-research-falcon.md
Insulin acts mainly by binding **INSR**, which autophosphorylates and recruits adaptor proteins (IRS, Shc), bifurcating into
GO:0005179 hormone activity
IBA
GO_REF:0000033 		ACCEPT
Summary: Insulin functions as a peptide hormone secreted by pancreatic beta cells that acts systemically to regulate metabolism. This annotation correctly captures insulin's role as a signaling molecule that travels through the bloodstream to affect distant target tissues.
Reason: This is an accurate but general annotation. While "insulin receptor binding" is more specific and informative, "hormone activity" is also correct and provides appropriate high-level classification of insulin's molecular function. Both terms are valid and complementary.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
Insulin functions as a 51-amino acid peptide hormone composed of two polypeptide chains linked by disulfide bonds, with the primary physiological role of regulating blood glucose homeostasis through complex signaling cascades
PMID:38397072
Insulin is a polypeptide hormone synthesized and secreted by pancreatic β-cells. It plays an important role as a metabolic hormone.
GO:0005615 extracellular space
IBA
GO_REF:0000033 		ACCEPT
Summary: Insulin is secreted from pancreatic beta cells and functions in the extracellular space, where it travels through the bloodstream to reach target tissues. This is the primary location where mature insulin carries out its function as a hormone.
Reason: This is the correct and most specific cellular component annotation for the location where mature insulin functions. Insulin is a secreted hormone that acts in the extracellular space. The IBA annotation is well-supported and represents the core functional location.
Supporting Evidence:
file:human/INS/INS-uniprot.txt
SUBCELLULAR LOCATION: Secreted.
file:human/INS/INS-deep-research-perplexity.md
Insulin is secreted from pancreatic beta cells into the extracellular space in response to elevated blood glucose
file:human/INS/INS-deep-research-falcon.md
**Plasma membrane/extracellular:** Ca2+-triggered exocytosis releases insulin to circulation; insulin acts as a ligand for the insulin receptor in peripheral tissues.
GO:0050714 positive regulation of protein secretion
IBA
GO_REF:0000033 		KEEP AS NON CORE
Summary: This annotation likely refers to insulin's effects on stimulating secretion of various proteins in target tissues, or possibly feedback effects on beta cell secretory processes.
Reason: While insulin may have some effects on protein secretion in various tissues, this is not a primary or well-characterized core function of insulin. The primary functions are glucose homeostasis, metabolic regulation, and cell growth. This annotation represents a more peripheral effect and should be marked as non-core.
GO:0042593 glucose homeostasis
IBA
GO_REF:0000033 		ACCEPT
Summary: This is THE core biological process for insulin. Insulin's primary physiological role is maintaining blood glucose homeostasis through stimulation of glucose uptake, suppression of hepatic glucose production, and coordination of glucose storage as glycogen.
Reason: This annotation captures the central and most important biological function of insulin. Extensive literature documents insulin's critical role in glucose homeostasis, and this is the primary reason insulin exists as a hormone. This is a core annotation that must be retained.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
The most physiologically important function of insulin is the stimulation of glucose uptake from the bloodstream into insulin-responsive tissues, particularly skeletal muscle and adipose tissue
file:human/INS/INS-deep-research-perplexity.md
Insulin potently suppresses hepatic glucose production through both direct actions on the liver and indirect actions mediated by effects on adipose tissue, muscle, and central nervous system signaling
file:human/INS/INS-uniprot.txt
Insulin decreases blood glucose concentration. It increases cell permeability to monosaccharides, amino acids and fatty acids.
PMID:38397072
Insulin influences the metabolism of glucose, regulating plasma glucose levels and stimulating glucose storage in organs such as the liver, muscles and adipose tissue.
file:human/INS/INS-deep-research-falcon.md
Human **INS (P01308)** encodes a secreted peptide hormone precursor whose primary function is to produce **mature insulin** (A/B chains) that is stored in dense-core secretory granules and released in a **glucose- and Ca2+-regulated** manner from β-cells to maintain systemic metabolic homeostasis.
GO:0005179 hormone activity
IEA
GO_REF:0000120 		ACCEPT
Summary: Duplicate of IBA annotation above. Electronic annotation based on InterPro domains and keywords.
Reason: This is a duplicate annotation (same term as line 2) but with different evidence code (IEA vs IBA). Both are correct. Duplicates are acceptable as they come from different evidence pipelines.
GO:0005576 extracellular region
IEA
GO_REF:0000120 		ACCEPT
Summary: This is a more general parent term of "extracellular space" (GO:0005615). Both are correct but extracellular space is more specific.
Reason: While "extracellular space" is more specific and preferred, this annotation is not wrong. It's a valid broader term. Having both the specific and general terms is acceptable in GO annotation practice.
GO:0006006 glucose metabolic process
IEA
GO_REF:0000043 		ACCEPT
Summary: Insulin regulates glucose metabolism broadly, including glucose uptake, glycolysis, glycogen synthesis, and suppression of gluconeogenesis. This is a valid but broad term.
Reason: This is an accurate but general term. "Glucose homeostasis" is more specific to insulin's regulatory role, but "glucose metabolic process" is also correct as insulin affects multiple aspects of glucose metabolism. Both terms provide useful information at different levels of specificity.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
Once inside the cell, glucose is phosphorylated by hexokinase to glucose-6-phosphate, which is then retained in the cell and utilized for glycolysis or stored as glycogen
file:human/INS/INS-uniprot.txt
It accelerates glycolysis, the pentose phosphate cycle, and glycogen synthesis in liver.
GO:1901701 cellular response to oxygen-containing compound
IEA
GO_REF:0000117 		MARK AS OVER ANNOTATED
Summary: This is an extremely broad term that could apply to almost any cellular process. Insulin may technically be involved in responses to various oxygen-containing compounds, but this annotation is not informative about insulin's specific function.
Reason: This term is far too general and non-specific to be useful for insulin annotation. While technically insulin signaling may involve responses to oxygen-containing compounds, this annotation doesn't capture any meaningful aspect of insulin's specific biological role. This represents computational over-annotation from ARBA.
GO:0005515 protein binding
IPI
PMID:17051221
Structures of human insulin-degrading enzyme reveal a new su... 		MODIFY
Summary: This annotation is based on physical interaction with insulin-degrading enzyme (IDE). While technically correct, "protein binding" is uninformative. The more specific term "protease binding" is annotated separately for this interaction.
Reason: Generic "protein binding" annotations should be replaced with more specific binding terms when available. In this case, since insulin binds to IDE (a protease), the annotation "protease binding" (GO:0002020) already exists and is more informative. However, the primary binding partner is the insulin receptor, so "insulin receptor binding" is most important.
Proposed replacements: protease binding
Supporting Evidence:
PMID:17051221
Structures of human insulin-degrading enzyme reveal a new substrate recognition mechanism.
GO:0005515 protein binding
IPI
PMID:23302862
How insulin engages its primary binding site on the insulin ... 		MODIFY
Summary: This annotation is based on interaction with insulin receptor (INSR). This is the most important molecular interaction for insulin, but "protein binding" is too general.
Reason: This interaction with insulin receptor should be annotated with the specific term "insulin receptor binding" (GO:0005158) which already exists in the annotation set, rather than the generic "protein binding" term.
Proposed replacements: insulin receptor binding
Supporting Evidence:
PMID:23302862
How insulin engages its primary binding site on the insulin receptor.
GO:0005515 protein binding
IPI
PMID:29512653
Structure of the insulin receptor-insulin complex by single-... 		MODIFY
Summary: This is another annotation for insulin-insulin receptor interaction based on cryo-EM structure determination. Same issue as above - too generic.
Reason: Should use "insulin receptor binding" (GO:0005158) instead of generic "protein binding".
Proposed replacements: insulin receptor binding
Supporting Evidence:
PMID:29512653
Structure of the insulin receptor-insulin complex by single-particle cryo-EM analysis.
GO:0005515 protein binding
IPI
PMID:32296183
A reference map of the human binary protein interactome. 		ACCEPT
Summary: This is from a large-scale binary protein interactome study. Multiple different binding partners detected, but all use generic "protein binding" term.
Reason: For high-throughput interactome studies where specific binding functions haven't been characterized, "protein binding" is acceptable. These annotations document physical interactions even if more specific functional terms aren't yet available.
Supporting Evidence:
PMID:32296183
Apr 8. A reference map of the human binary protein interactome.
GO:0005515 protein binding
IPI
PMID:9388210
Inhibition of insulin receptor activation by insulin-like gr... 		ACCEPT
Summary: Interaction with insulin-like growth factor binding proteins (IGFBPs) that can inhibit insulin receptor activation.
Reason: Without a more specific term for IGFBP binding available in GO, "protein binding" is acceptable for documenting this interaction. This interaction has functional significance for insulin receptor signaling.
Supporting Evidence:
PMID:9388210
Inhibition of insulin receptor activation by insulin-like growth factor binding proteins.
GO:0005515 protein binding
IPI
PMID:9773776
Megalin is an endocytic receptor for insulin. 		ACCEPT
Summary: Interaction with megalin, an endocytic receptor that can internalize insulin.
Reason: This documents a specific interaction with megalin that is relevant for insulin clearance and degradation. Without a more specific GO term available, "protein binding" is acceptable.
Supporting Evidence:
PMID:9773776
Megalin is an endocytic receptor for insulin.
GO:0042802 identical protein binding
IPI
PMID:10508408
Structural consequences of the B5 histidine --> tyrosine mut... 		ACCEPT
Summary: This and the following 7 annotations document insulin's ability to form dimers and higher-order oligomers (hexamers). This is important for insulin storage in secretory granules as zinc-insulin hexamers.
Reason: Insulin oligomerization is a well-established and functionally important property. Insulin forms dimers and zinc-stabilized hexamers that are the storage form in pancreatic beta cells. Multiple independent studies support this annotation.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
Insulin possesses a histidine residue at position B10 that coordinates zinc ions, enabling the formation of zinc-stabilized hexamers through a toroidal geometry in which two zinc ions coordinate the B10 histidine residues of three insulin dimers
file:human/INS/INS-deep-research-perplexity.md
These zinc-insulin hexamers represent the predominant storage form of insulin within pancreatic beta cell secretory granules
PMID:10508408
Structural consequences of the B5 histidine --> tyrosine mutation in human insulin characterized by X-ray crystallography and conformational analysis.
GO:0042802 identical protein binding
IPI
PMID:17472440
A helical structural nucleus is the primary elongating unit ... 		ACCEPT
Summary: Study on insulin amyloid fibril formation, another form of insulin self-association.
Reason: While amyloid formation is pathological rather than physiological, it does represent insulin-insulin binding. The annotation is technically correct.
Supporting Evidence:
PMID:17472440
A helical structural nucleus is the primary elongating unit of insulin amyloid fibrils.
GO:0042802 identical protein binding
IPI
PMID:20738396
Structural features of proinsulin C-peptide oligomeric and a... 		ACCEPT
Summary: Structural study of proinsulin C-peptide oligomerization. Note this is about C-peptide, not mature insulin.
Reason: C-peptide is part of the proinsulin precursor, and this annotation applies to the full-length preproinsulin/proinsulin forms that are present during biosynthesis.
Supporting Evidence:
PMID:20738396
2010 Aug 3. Structural features of proinsulin C-peptide oligomeric and amyloid states.
GO:0042802 identical protein binding
IPI
PMID:22854022
SERF protein is a direct modifier of amyloid fiber assembly. 		ACCEPT
Summary: Study on SERF protein as modifier of amyloid fiber assembly involving insulin.
Reason: Documents insulin self-association in context of amyloid formation.
Supporting Evidence:
PMID:22854022
2012 Jul 26. SERF protein is a direct modifier of amyloid fiber assembly.
GO:0042802 identical protein binding
IPI
PMID:23106816
Insulin solubility transitions by pH-dependent interactions ... 		ACCEPT
Summary: Study on insulin solubility transitions involving interactions with C-peptide.
Reason: Documents insulin oligomerization behavior.
Supporting Evidence:
PMID:23106816
Insulin solubility transitions by pH-dependent interactions with proinsulin C-peptide.
GO:0042802 identical protein binding
IPI
PMID:23416304
Amino acid sequence determinants in self-assembly of insulin... 		ACCEPT
Summary: Study on amino acid determinants in insulin amyloid superstructures.
Reason: Documents insulin self-assembly properties.
Supporting Evidence:
PMID:23416304
2013 Feb 14. Amino acid sequence determinants in self-assembly of insulin chiral amyloid superstructures: role of C-terminus of B-chain in association of fibrils.
GO:0042802 identical protein binding
IPI
PMID:23510797
Peptides that form β-sheets on hydrophobic surfaces accelera... 		ACCEPT
Summary: Study on surface-induced insulin amyloidal aggregation.
Reason: Documents insulin oligomerization.
Supporting Evidence:
PMID:23510797
2013 Mar 16. Peptides that form β-sheets on hydrophobic surfaces accelerate surface-induced insulin amyloidal aggregation.
GO:0042802 identical protein binding
IPI
PMID:8844841
A novel complex of a phenolic derivative with insulin: struc... 		ACCEPT
Summary: Structural study of insulin complexes related to T→R transition.
Reason: Documents functional insulin oligomerization relevant to hexamer formation.
Supporting Evidence:
PMID:8844841
A novel complex of a phenolic derivative with insulin: structural features related to the T-->R transition.
GO:0008286 insulin receptor signaling pathway
IDA
PMID:8702995
Akt, a pleckstrin homology domain containing kinase, is acti... 		ACCEPT
Summary: This study demonstrated that insulin activates Akt (PKB) kinase primarily through phosphorylation, establishing insulin's role in the PI3K/Akt signaling cascade.
Reason: This is a core biological process annotation for insulin. Activation of the insulin receptor signaling pathway is the primary mechanism by which insulin exerts its effects on glucose homeostasis and metabolism. Well-supported by extensive literature.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
The binding of insulin to its extracellular receptor leads to rapid and sequential autophosphorylation of multiple tyrosine residues distributed across different domains of the intracellular region
file:human/INS/INS-deep-research-perplexity.md
The phosphatidylinositol 3-kinase (PI3K) pathway represents the primary route through which insulin exerts its metabolic effects
PMID:8702995
Akt, a pleckstrin homology domain containing kinase, is activated primarily by phosphorylation.
file:human/INS/INS-deep-research-falcon.md
**PI3K→PIP3→AKT** (metabolic branch): GLUT4 translocation, glycogen synthesis regulation via GSK3, mTOR-mediated protein synthesis, and transcriptional programs (e.g., FOXO regulation).
GO:0048018 receptor ligand activity
IDA
PMID:8702995
Akt, a pleckstrin homology domain containing kinase, is acti... 		ACCEPT
Summary: This is a general term indicating that insulin functions as a ligand for its receptor. This is accurate but less specific than "insulin receptor binding".
Reason: This is a valid molecular function term that correctly describes insulin as a receptor ligand. While "insulin receptor binding" is more specific, both terms are appropriate and provide complementary information.
Supporting Evidence:
PMID:8702995
Akt, a pleckstrin homology domain containing kinase, is activated primarily by phosphorylation.
GO:0051897 positive regulation of phosphatidylinositol 3-kinase/protein kinase B signal transduction
IDA
PMID:8702995
Akt, a pleckstrin homology domain containing kinase, is acti... 		ACCEPT
Summary: This annotation captures one of the two major signaling cascades activated by insulin - the PI3K/Akt pathway, which mediates most metabolic effects including glucose uptake, glycogen synthesis, and protein synthesis.
Reason: This is a core signaling pathway for insulin and represents one of the most important mechanisms by which insulin regulates glucose homeostasis. Well-documented in the literature.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
The phosphatidylinositol 3-kinase (PI3K) pathway represents the primary route through which insulin exerts its metabolic effects, particularly regarding glucose homeostasis, glycogen synthesis, and protein synthesis
file:human/INS/INS-deep-research-perplexity.md
Once activated, AKT phosphorylates numerous downstream substrates that collectively mediate the metabolic effects of insulin
PMID:8702995
Akt, a pleckstrin homology domain containing kinase, is activated primarily by phosphorylation.
file:human/INS/INS-deep-research-falcon.md
**PI3K→PIP3→AKT** (metabolic branch): GLUT4 translocation, glycogen synthesis regulation via GSK3, mTOR-mediated protein synthesis, and transcriptional programs (e.g., FOXO regulation).
GO:0005179 hormone activity
NAS
PMID:14986111
Impaired binding of insulin to erythrocyte membrane receptor... 		ACCEPT
Summary: Another instance of the hormone activity annotation, this time with NAS evidence code.
Reason: Duplicate of earlier annotations but with different evidence. This is acceptable.
Supporting Evidence:
PMID:14986111
Impaired binding of insulin to erythrocyte membrane receptor and the activation of nitric oxide synthase by the hormone in human breast cancer.
GO:0005615 extracellular space
IDA
PMID:9667398
Familial hyperproinsulinaemia due to a mutation substituting... 		ACCEPT
Summary: Direct experimental evidence for insulin localization in extracellular space.
Reason: This provides experimental (IDA) evidence for the cellular component annotation, complementing the IBA annotation.
Supporting Evidence:
PMID:9667398
Familial hyperproinsulinaemia due to a mutation substituting histidine for arginine at position 65 in proinsulin: identification of the mutation by restriction enzyme mapping.
GO:0008286 insulin receptor signaling pathway
IDA
PMID:15792832
Insulin and nitric oxide stimulates glucose transport in hum... 		ACCEPT
Summary: Study on insulin and nitric oxide stimulation of glucose transport in human placenta.
Reason: Multiple independent experimental confirmations of insulin's role in the insulin receptor signaling pathway are valuable and support the core annotation.
Supporting Evidence:
PMID:15792832
2005 Jan 27. Insulin and nitric oxide stimulates glucose transport in human placenta.
GO:0008286 insulin receptor signaling pathway
IGI
PMID:19727662
Extracellular PBEF/NAMPT/visfatin activates pro-inflammatory... 		UNDECIDED
Summary: The GOA reference for this annotation is PMID:19727662, which is in fact a NAMPT/visfatin paper on vascular smooth muscle cells, not an insulin paper (verified during PR #764 round-2 review). The annotation itself (insulin → insulin receptor signaling pathway) is correct in principle but the cited evidence does not actually support it; cannot validate without a correct PMID.
Reason: Original GOA reference (PMID:19727662) is misattributed — it is a NAMPT paper, not an insulin paper. Action retained as UNDECIDED until GOA supplies (or curator identifies) a correctly-attributed reference for IGI evidence of INS in insulin receptor signaling. Note: the broader insulin receptor signaling pathway annotation remains amply supported elsewhere in this review by other valid references.
Supporting Evidence:
PMID:19727662
2009 Aug 29. Extracellular PBEF/NAMPT/visfatin activates pro-inflammatory signalling in human vascular smooth muscle cells through nicotinamide phosphoribosyltransferase activity.
GO:0043123 positive regulation of canonical NF-kappaB signal transduction
IDA
PMID:19727662
Extracellular PBEF/NAMPT/visfatin activates pro-inflammatory... 		UNDECIDED
Summary: The GOA reference for this annotation is PMID:19727662, which is in fact a NAMPT/visfatin paper, not an insulin paper (verified during PR #764 round-2 review). Cannot validate the IDA evidence for INS → NF-kappaB signaling on the cited reference alone.
Reason: Original GOA reference (PMID:19727662) is misattributed — it is a NAMPT paper studying vascular smooth muscle cells, not an insulin paper. While insulin may activate NF-kappaB in some contexts, this specific annotation cannot be evaluated until a correct reference is supplied.
Supporting Evidence:
PMID:19727662
2009 Aug 29. Extracellular PBEF/NAMPT/visfatin activates pro-inflammatory signalling in human vascular smooth muscle cells through nicotinamide phosphoribosyltransferase activity.
GO:0005179 hormone activity
IMP
PMID:381941
A structurally abnormal insulin causing human diabetes. 		ACCEPT
Summary: Classic study on structurally abnormal insulin causing diabetes, demonstrating hormone function.
Reason: Another instance with experimental evidence (IMP) for hormone activity.
Supporting Evidence:
PMID:381941
A structurally abnormal insulin causing human diabetes.
GO:0008286 insulin receptor signaling pathway
IDA
PMID:20455999
A novel domain of caveolin-2 that controls nuclear targeting... 		ACCEPT
Summary: Study on caveolin-2 regulation of insulin-specific ERK activation.
Reason: Additional experimental support for insulin receptor signaling pathway.
Supporting Evidence:
PMID:20455999
A novel domain of caveolin-2 that controls nuclear targeting: regulation of insulin-specific ERK activation and nuclear translocation by caveolin-2.
GO:0008286 insulin receptor signaling pathway
IMP
PMID:14615391
Insulin stimulates glucose transport via nitric oxide/cyclic... 		ACCEPT
Summary: Study showing insulin stimulates glucose transport via NO/cGMP pathway.
Reason: Experimental evidence for insulin receptor signaling, though this highlights the NO/cGMP branch.
Supporting Evidence:
PMID:14615391
Insulin stimulates glucose transport via nitric oxide/cyclic GMP pathway in human vascular smooth muscle cells.
GO:0000139 Golgi membrane
TAS
Reactome:R-HSA-6809006 		ACCEPT
Summary: Proinsulin passes through the Golgi apparatus during its trafficking from ER to secretory granules.
Reason: This is an accurate annotation for the biosynthetic trafficking of proinsulin through the secretory pathway. While not the final functional location, this represents an important intermediate location during insulin biogenesis in beta cells.
Supporting Evidence:
file:human/INS/INS-deep-research-falcon.md
**Golgi/TGN:** trafficking and packaging into immature secretory granules.
GO:0000139 Golgi membrane
TAS
Reactome:R-HSA-6809010 		ACCEPT
Summary: Duplicate Golgi membrane annotation from different Reactome reaction.
Reason: Multiple Reactome reactions document proinsulin trafficking through Golgi.
GO:0000139 Golgi membrane
TAS
Reactome:R-HSA-6809011 		ACCEPT
Summary: Another Golgi membrane annotation from Reactome.
Reason: Additional Reactome support for Golgi localization.
GO:0005788 endoplasmic reticulum lumen
TAS
Reactome:R-HSA-264997 		ACCEPT
Summary: Proinsulin enters the ER lumen after translocation and undergoes disulfide bond formation there.
Reason: This is an accurate annotation for an early stage of insulin biosynthesis. Preproinsulin is translocated into the ER lumen where it is processed to proinsulin and undergoes critical folding and disulfide bond formation.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
Following translocation into the ER lumen, preproinsulin undergoes signal peptide cleavage to generate proinsulin, the 86-amino acid single-chain precursor of insulin
file:human/INS/INS-deep-research-perplexity.md
The ER environment is specifically optimized to facilitate this disulfide bond formation through multiple specialized mechanisms
PMID:40052150
Proinsulin foldability is optimized in the ER, an environment evolved to support the folding process and the formation of disulfide bonds while minimizing misfolding.
PMID:38935435
Hyperoxidation of the ER delays proinsulin export and limits the proinsulin supply available for insulin granule formation.
GO:0005788 endoplasmic reticulum lumen
TAS
Reactome:R-HSA-265010 		ACCEPT
Summary: Another ER lumen annotation from Reactome pathway.
Reason: Additional Reactome support for ER localization.
GO:0005796 Golgi lumen
TAS
Reactome:R-HSA-264976 		ACCEPT
Summary: Proinsulin travels through the Golgi lumen and binds zinc and calcium there.
Reason: Accurate annotation for proinsulin trafficking. The Golgi lumen is where proinsulin binds zinc and calcium ions, which are important for subsequent crystal formation in secretory granules.
GO:0005796 Golgi lumen
TAS
Reactome:R-HSA-265010 		ACCEPT
Summary: Duplicate Golgi lumen annotation.
Reason: Multiple Reactome reactions support Golgi lumen localization.
GO:0005796 Golgi lumen
TAS
Reactome:R-HSA-265153 		ACCEPT
Summary: Another Golgi lumen annotation.
Reason: Additional Reactome support.
GO:0030133 transport vesicle
TAS
Reactome:R-HSA-6807877 		ACCEPT
Summary: Proinsulin travels in transport vesicles from ER to Golgi and from Golgi to secretory granules.
Reason: Accurate annotation for the vesicular transport stages of insulin biosynthesis.
GO:0030133 transport vesicle
TAS
Reactome:R-HSA-6809003 		ACCEPT
Summary: Duplicate transport vesicle annotation.
Reason: Multiple Reactome reactions document vesicular transport.
GO:0030133 transport vesicle
TAS
Reactome:R-HSA-6809006 		ACCEPT
Summary: Another transport vesicle annotation.
Reason: Additional Reactome support.
GO:0033116 endoplasmic reticulum-Golgi intermediate compartment membrane
TAS
Reactome:R-HSA-6807875 		ACCEPT
Summary: The ERGIC is an intermediate compartment between ER and Golgi that proinsulin passes through.
Reason: This is an accurate annotation for the trafficking pathway. Proinsulin passes through the ERGIC compartment during its journey from ER to Golgi.
GO:0033116 endoplasmic reticulum-Golgi intermediate compartment membrane
TAS
Reactome:R-HSA-6807877 		ACCEPT
Summary: Duplicate ERGIC annotation.
Reason: Multiple Reactome reactions support ERGIC localization.
GO:0034774 secretory granule lumen
TAS
Reactome:R-HSA-265153 		ACCEPT
Summary: Proinsulin is packaged into secretory granules where it is processed to mature insulin and stored as zinc-insulin crystals.
Reason: This is a critical location for insulin. Secretory granules are where proinsulin is processed by prohormone convertases to mature insulin, and where insulin is stored as zinc-stabilized hexamers before secretion. This is an essential annotation.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
The PC1/3-mediated cleavage occurs within specialized secretory granules where pH is maintained at 5.0-5.5 by an intrinsic proton pump, creating conditions optimal for both prohormone processing and zinc-insulin crystal formation
file:human/INS/INS-deep-research-perplexity.md
These zinc-insulin hexamers represent the predominant storage form of insulin within pancreatic beta cell secretory granules, where they exist as water-insoluble crystals
PMID:37159024
proinsulin is an early driver of insulin SG biogenesis, in a process in which its co-condensation with RESP18HD participates in their phase separation from other secretory proteins in transit through the same compartments but destined to other routes.
file:human/INS/INS-deep-research-falcon.md
**Immature/maturing secretory granules:** proteolytic conversion of proinsulin → insulin + C-peptide; granule acidification/condensation and storage.
GO:0034774 secretory granule lumen
TAS
Reactome:R-NUL-9023165 		ACCEPT
Summary: Annotation for proinsulin processing in secretory granules (rat PC1/3 cleaves human proinsulin).
Reason: Documents location where proinsulin processing occurs.
GO:0034774 secretory granule lumen
TAS
Reactome:R-NUL-9023166 		ACCEPT
Summary: Another secretory granule annotation for processing steps.
Reason: Additional Reactome support for secretory granule localization.
GO:0034774 secretory granule lumen
TAS
Reactome:R-NUL-9023180 		ACCEPT
Summary: Secretory granule annotation for PC2-mediated cleavage step.
Reason: Documents processing location.
GO:0034774 secretory granule lumen
TAS
Reactome:R-NUL-9023186 		ACCEPT
Summary: Secretory granule annotation for carboxypeptidase processing.
Reason: Additional Reactome support.
GO:0010976 positive regulation of neuron projection development
IC
PMID:36250347
Insulin stimulates atypical protein kinase C-mediated phosph... 		KEEP AS NON CORE
Summary: Study showing insulin stimulates neurite outgrowth through activation of atypical PKC and ARF6-Rac1 signaling.
Reason: While insulin does have effects on neuronal development and function, this is not a primary core function. The core functions are metabolic regulation. Neuronal effects, while important, are secondary to the primary metabolic role.
Supporting Evidence:
PMID:36250347
Insulin stimulates atypical protein kinase C-mediated phosphorylation of the neuronal adaptor FE65 to potentiate neurite outgrowth by activating ARF6-Rac1 signaling.
GO:0048018 receptor ligand activity
IDA
PMID:29512653
Structure of the insulin receptor-insulin complex by single-... 		ACCEPT
Summary: Duplicate of earlier receptor ligand activity annotation with different reference.
Reason: Multiple independent confirmations of receptor ligand activity are valuable.
Supporting Evidence:
PMID:29512653
Structure of the insulin receptor-insulin complex by single-particle cryo-EM analysis.
GO:0010629 negative regulation of gene expression
IDA
PMID:31501273
MicroRNA 7 Impairs Insulin Signaling and Regulates Aβ Levels... 		KEEP AS NON CORE
Summary: This study showed insulin's involvement in regulating gene expression, particularly through microRNA-mediated mechanisms affecting IRS2, INSR, IDE, and LXR pathway.
Reason: While insulin does regulate gene expression (e.g., suppression of gluconeogenic genes via FoxO1 inhibition), "negative regulation of gene expression" is very broad and non-specific. More specific terms like "negative regulation of gluconeogenesis" would be more informative. This should be kept but marked as non-core due to lack of specificity.
Supporting Evidence:
PMID:31501273
2019 Nov 15. MicroRNA 7 Impairs Insulin Signaling and Regulates Aβ Levels through Posttranscriptional Regulation of the Insulin Receptor Substrate 2, Insulin Receptor, Insulin-Degrading Enzyme, and Liver X Receptor Pathway.
GO:0051897 positive regulation of phosphatidylinositol 3-kinase/protein kinase B signal transduction
IDA
PMID:25240198
Saturated fatty acid-induced miR-195 impairs insulin signali... 		ACCEPT
Summary: Another confirmation of PI3K/Akt pathway activation by insulin.
Reason: Additional experimental support for this core signaling pathway.
Supporting Evidence:
PMID:25240198
Epub 2014 Sep 19. Saturated fatty acid-induced miR-195 impairs insulin signaling and glycogen metabolism in HepG2 cells.
GO:0038060 nitric oxide-cGMP-mediated signaling
IDA
PMID:14744991
Insulin induces the release of vasodilator compounds from pl... 		KEEP AS NON CORE
Summary: Insulin induces vasodilation through NO-cGMP pathway, involving release of vasodilator compounds from platelets.
Reason: While insulin does activate NO-cGMP signaling particularly in vascular endothelium, this is a secondary effect related to insulin's vascular actions. Not a core metabolic function, though physiologically important for blood flow regulation.
Supporting Evidence:
PMID:14744991
Insulin induces the release of vasodilator compounds from platelets by a nitric oxide-G kinase-VAMP-3-dependent pathway.
GO:0042311 vasodilation
IDA
PMID:14744991
Insulin induces the release of vasodilator compounds from pl... 		KEEP AS NON CORE
Summary: Insulin causes vasodilation through nitric oxide release.
Reason: Vasodilation is a physiologically important effect of insulin but not a core function. The core function is metabolic regulation. Vascular effects, while significant, are peripheral to the primary role.
Supporting Evidence:
PMID:14744991
Insulin induces the release of vasodilator compounds from platelets by a nitric oxide-G kinase-VAMP-3-dependent pathway.
GO:0042311 vasodilation
NAS
PMID:12946932
Insulin impairs endothelium-dependent vasodilation independe... 		KEEP AS NON CORE
Summary: Additional evidence for insulin's vasodilatory effects.
Reason: Duplicate of previous vasodilation annotation with different evidence.
Supporting Evidence:
PMID:12946932
Insulin impairs endothelium-dependent vasodilation independent of insulin sensitivity or lipid profile.
GO:0005576 extracellular region
TAS
Reactome:R-HSA-110011 		ACCEPT
Summary: Multiple Reactome pathways document insulin in extracellular region during receptor binding and signaling.
Reason: This broader term complements the more specific "extracellular space" annotation. Multiple Reactome reactions support this.
GO:0005576 extracellular region
TAS
Reactome:R-HSA-74707 		ACCEPT
Summary: Reactome annotation for insulin binding to insulin receptor.
Reason: Additional Reactome support for extracellular localization.
GO:0005576 extracellular region
TAS
Reactome:R-HSA-74711 		ACCEPT
Summary: Reactome pathway annotation for extracellular region.
Reason: Additional Reactome support.
GO:0005576 extracellular region
TAS
Reactome:R-HSA-74712 		ACCEPT
Summary: Reactome pathway annotation.
Reason: Additional Reactome support.
GO:0005576 extracellular region
TAS
Reactome:R-HSA-74715 		ACCEPT
Summary: Reactome pathway annotation.
Reason: Additional Reactome support.
GO:0005576 extracellular region
TAS
Reactome:R-HSA-74716 		ACCEPT
Summary: Reactome pathway annotation.
Reason: Additional Reactome support.
GO:0005576 extracellular region
TAS
Reactome:R-HSA-74718 		ACCEPT
Summary: Reactome pathway annotation.
Reason: Additional Reactome support.
GO:0005576 extracellular region
TAS
Reactome:R-HSA-74740 		ACCEPT
Summary: Reactome pathway annotation.
Reason: Additional Reactome support.
GO:0005576 extracellular region
TAS
Reactome:R-HSA-74742 		ACCEPT
Summary: Reactome pathway annotation.
Reason: Additional Reactome support.
GO:0005576 extracellular region
TAS
Reactome:R-HSA-74743 		ACCEPT
Summary: Reactome pathway annotation.
Reason: Additional Reactome support.
GO:0005576 extracellular region
TAS
Reactome:R-HSA-976734 		ACCEPT
Summary: Reactome pathway annotation.
Reason: Additional Reactome support.
GO:0005576 extracellular region
TAS
Reactome:R-HSA-977136 		ACCEPT
Summary: Reactome pathway annotation.
Reason: Additional Reactome support.
GO:0010750 positive regulation of nitric oxide mediated signal transduction
IDA
PMID:15792832
Insulin and nitric oxide stimulates glucose transport in hum... 		KEEP AS NON CORE
Summary: Insulin positively regulates NO-mediated signaling in placenta and vascular tissue.
Reason: While insulin does regulate NO signaling, this is a secondary vascular/endothelial effect rather than a core metabolic function. Should be retained but marked as non-core.
Supporting Evidence:
PMID:15792832
2005 Jan 27. Insulin and nitric oxide stimulates glucose transport in human placenta.
GO:0046326 positive regulation of D-glucose import across plasma membrane
IDA
PMID:15792832
Insulin and nitric oxide stimulates glucose transport in hum... 		ACCEPT
Summary: This is one of THE core functions of insulin - stimulation of glucose uptake through GLUT4 translocation to the plasma membrane in muscle and adipose tissue.
Reason: This is a core function annotation that captures one of the most important physiological actions of insulin - stimulation of glucose uptake. This is essential for glucose homeostasis.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
The most physiologically important function of insulin is the stimulation of glucose uptake from the bloodstream into insulin-responsive tissues, particularly skeletal muscle and adipose tissue, which together account for the majority of postprandial glucose disposal
file:human/INS/INS-deep-research-perplexity.md
Upon insulin stimulation, GLUT4-containing vesicles rapidly translocate to the plasma membrane, increasing cell surface GLUT4 by 2-3 fold and dramatically enhancing glucose transport capacity
PMID:15792832
2005 Jan 27. Insulin and nitric oxide stimulates glucose transport in human placenta.
GO:0008284 positive regulation of cell population proliferation
IDA
PMID:7688386
Insulin and IGF-1 increase mitogenesis and glucose metabolis... 		KEEP AS NON CORE
Summary: Insulin and IGF-1 increase mitogenesis in multiple myeloma cell line. Insulin has mitogenic effects through MAPK/ERK pathway activation.
Reason: While insulin does have growth-promoting and mitogenic effects, particularly through the MAPK pathway, this is not the core primary function. The primary function is metabolic regulation. Mitogenic effects are secondary, though physiologically important.
Supporting Evidence:
PMID:7688386
Insulin and IGF-1 increase mitogenesis and glucose metabolism in the multiple myeloma cell line, RPMI 8226.
GO:0010750 positive regulation of nitric oxide mediated signal transduction
IMP
PMID:14615391
Insulin stimulates glucose transport via nitric oxide/cyclic... 		KEEP AS NON CORE
Summary: Duplicate of earlier NO signaling annotation with different evidence code.
Reason: Same as earlier - vascular effect, not core metabolic function.
Supporting Evidence:
PMID:14615391
Insulin stimulates glucose transport via nitric oxide/cyclic GMP pathway in human vascular smooth muscle cells.
GO:1902952 positive regulation of dendritic spine maintenance
IGI
PMID:19188609
Protection of synapses against Alzheimer's-linked toxins: in... 		KEEP AS NON CORE
Summary: Insulin signaling protects synapses against Alzheimer's-related toxins and promotes dendritic spine maintenance.
Reason: Neuronal/synaptic effects of insulin, while important for brain function and potentially relevant to neurodegenerative disease, are not core metabolic functions. This is a peripheral but interesting function.
Supporting Evidence:
PMID:19188609
Protection of synapses against Alzheimer's-linked toxins: insulin signaling prevents the pathogenic binding of Abeta oligomers.
GO:1903076 regulation of protein localization to plasma membrane
IGI
PMID:19188609
Protection of synapses against Alzheimer's-linked toxins: in... 		ACCEPT
Summary: This likely refers to insulin's effect on GLUT4 translocation and other membrane protein trafficking events.
Reason: This is mechanistically related to insulin's core function of stimulating glucose uptake. The regulation of GLUT4 localization to plasma membrane is a key mechanism of insulin action. While broad, this annotation captures an important aspect of insulin signaling.
Supporting Evidence:
PMID:19188609
Protection of synapses against Alzheimer's-linked toxins: insulin signaling prevents the pathogenic binding of Abeta oligomers.
GO:1903427 negative regulation of reactive oxygen species biosynthetic process
IGI
PMID:19188609
Protection of synapses against Alzheimer's-linked toxins: in... 		KEEP AS NON CORE
Summary: Insulin has antioxidant effects and can suppress ROS production.
Reason: While insulin does have antioxidant and protective effects, this is not a core function. This represents a peripheral effect related to cellular protection.
Supporting Evidence:
PMID:19188609
Protection of synapses against Alzheimer's-linked toxins: insulin signaling prevents the pathogenic binding of Abeta oligomers.
GO:1990535 neuron projection maintenance
IGI
PMID:19188609
Protection of synapses against Alzheimer's-linked toxins: in... 		KEEP AS NON CORE
Summary: Insulin signaling supports maintenance of neuronal projections.
Reason: Neuronal effect, not core metabolic function.
Supporting Evidence:
PMID:19188609
Protection of synapses against Alzheimer's-linked toxins: insulin signaling prevents the pathogenic binding of Abeta oligomers.
GO:1900273 positive regulation of long-term synaptic potentiation
TAS
PMID:19188609
Protection of synapses against Alzheimer's-linked toxins: in... 		KEEP AS NON CORE
Summary: Insulin enhances synaptic plasticity and long-term potentiation in hippocampus.
Reason: Neuronal/cognitive effect, not core metabolic function.
Supporting Evidence:
PMID:19188609
Protection of synapses against Alzheimer's-linked toxins: insulin signaling prevents the pathogenic binding of Abeta oligomers.
GO:0048167 regulation of synaptic plasticity
TAS
PMID:19188609
Protection of synapses against Alzheimer's-linked toxins: in... 		KEEP AS NON CORE
Summary: Insulin regulates synaptic plasticity.
Reason: Neuronal effect, not core metabolic function.
Supporting Evidence:
PMID:19188609
Protection of synapses against Alzheimer's-linked toxins: insulin signaling prevents the pathogenic binding of Abeta oligomers.
GO:0050890 cognition
TAS
PMID:19188609
Protection of synapses against Alzheimer's-linked toxins: in... 		KEEP AS NON CORE
Summary: Insulin has roles in cognitive function.
Reason: This is an extremely broad term. While insulin does affect cognition, this annotation is not specific or informative about insulin's actual function. Should be kept as non-core but is borderline over-annotation.
Supporting Evidence:
PMID:19188609
Protection of synapses against Alzheimer's-linked toxins: insulin signaling prevents the pathogenic binding of Abeta oligomers.
GO:0010628 positive regulation of gene expression
IGI
PMID:25403480
Glucose tolerance is associated with differential expression... 		KEEP AS NON CORE
Summary: Insulin regulates gene expression through various mechanisms including effects on transcription factors and microRNAs.
Reason: While insulin does regulate gene expression (e.g., lipogenic genes via SREBP-1c, suppression of gluconeogenic genes), this term is extremely broad and non-specific. More specific terms about particular pathways would be more informative.
Supporting Evidence:
PMID:25403480
Nov 19. Glucose tolerance is associated with differential expression of microRNAs in skeletal muscle: results from studies of twins with and without type 2 diabetes.
GO:0043410 positive regulation of MAPK cascade
IDA
PMID:20455999
A novel domain of caveolin-2 that controls nuclear targeting... 		ACCEPT
Summary: Insulin activates the MAPK/ERK cascade through SHC-Grb2-SOS-Ras-Raf-MEK-ERK pathway. This is one of the two major signaling cascades activated by insulin receptor.
Reason: The MAPK pathway is one of the two major signaling cascades downstream of insulin receptor (along with PI3K/Akt). While it plays a more prominent role in growth/proliferation than acute metabolic effects, it is still a core signaling pathway for insulin.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
In parallel with the PI3K/AKT pathway, insulin also activates the mitogen-activated protein kinase (MAPK) pathway primarily through interaction of the SHC adaptor protein with the phosphorylated insulin receptor
file:human/INS/INS-deep-research-perplexity.md
The MAPK pathway mediated by ERK1/2 has distinct biological effects compared to the PI3K/AKT pathway, with the MAPK pathway playing a more prominent role in the regulation of gene expression and cell proliferation
PMID:20455999
A novel domain of caveolin-2 that controls nuclear targeting: regulation of insulin-specific ERK activation and nuclear translocation by caveolin-2.
GO:1900182 positive regulation of protein localization to nucleus
IDA
PMID:20455999
A novel domain of caveolin-2 that controls nuclear targeting... 		KEEP AS NON CORE
Summary: Study on caveolin-2 regulation of insulin-specific ERK activation and nuclear translocation.
Reason: While insulin signaling does regulate nuclear translocation of various proteins (e.g., ERK, FoxO1), this is a very broad and non-specific annotation. It's mechanistically accurate but not informative about insulin's core functions.
Supporting Evidence:
PMID:20455999
A novel domain of caveolin-2 that controls nuclear targeting: regulation of insulin-specific ERK activation and nuclear translocation by caveolin-2.
GO:0050995 negative regulation of lipid catabolic process
IMP
PMID:24675707
Resistin in dairy cows: plasma concentrations during early l... 		ACCEPT
Summary: Insulin potently inhibits lipolysis in adipose tissue through inactivation of hormone-sensitive lipase. This is a core metabolic function and is amply supported by the deep research findings. However, the GOA-cited reference (PMID:24675707) is a dairy cow resistin paper, not a human insulin IMP study (verified during PR #764 round-2 review). Action retained as ACCEPT on the basis of the deep-research-supported function, with the misattributed reference flagged for GOA correction.
Reason: Inhibition of lipolysis is a core, textbook metabolic function of insulin (see deep research supporting_text below). The GOA reference PMID:24675707 is misattributed (dairy cow resistin paper) and does not support this IMP annotation; flagged for GOA-side correction but the underlying biology is sound.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
Reciprocally, insulin potently inhibits lipolysis in adipose tissue through inactivation of hormone-sensitive lipase (HSL) via a PKA-independent mechanism
file:human/INS/INS-deep-research-perplexity.md
The net result is decreased adipose tissue lipolysis and reduced circulating free fatty acid levels
GO:1902176 negative regulation of oxidative stress-induced intrinsic apoptotic signaling pathway
NAS
PMID:16604263
Neuroprotection of insulin against oxidative stress-induced ... 		KEEP AS NON CORE
Summary: Insulin provides neuroprotection against oxidative stress-induced apoptosis through PI3K/Akt pathway.
Reason: While insulin does have anti-apoptotic and neuroprotective effects, this is not a core metabolic function. This represents a protective/survival effect that is peripheral to the primary role.
Supporting Evidence:
PMID:16604263
Neuroprotection of insulin against oxidative stress-induced apoptosis in cultured retinal neurons: involvement of phosphoinositide 3-kinase/Akt signal pathway.
GO:0031904 endosome lumen
TAS
Reactome:R-HSA-74718 		ACCEPT
Summary: After internalization of the insulin-insulin receptor complex, insulin traffics through endosomes where it can be degraded or the receptor recycled.
Reason: This is an accurate annotation for insulin trafficking after receptor-mediated endocytosis. The endosomal pathway is important for both insulin degradation and receptor recycling.
GO:0031904 endosome lumen
TAS
Reactome:R-HSA-74726 		ACCEPT
Summary: Reactome pathway for insulin in endosomes.
Reason: Additional Reactome support for endosomal localization.
GO:0031904 endosome lumen
TAS
Reactome:R-HSA-74730 		ACCEPT
Summary: Reactome pathway for insulin degradation in endosomes.
Reason: Insulin is degraded in endosomes by insulin-degrading enzyme.
GO:0090277 positive regulation of peptide hormone secretion
TAS
PMID:11387233
Insulin and glucocorticoids differentially regulate leptin t... 		KEEP AS NON CORE
Summary: Insulin can regulate secretion of other peptide hormones like leptin.
Reason: While insulin does affect secretion of other hormones, this is not a core function. The primary function is metabolic regulation through direct cellular effects, not through regulating other hormones (though that does occur).
Supporting Evidence:
PMID:11387233
Insulin and glucocorticoids differentially regulate leptin transcription and secretion in brown adipocytes.
GO:0090336 positive regulation of brown fat cell differentiation
TAS
PMID:11387233
Insulin and glucocorticoids differentially regulate leptin t... 		KEEP AS NON CORE
Summary: Insulin promotes brown adipocyte differentiation.
Reason: While insulin does have effects on adipocyte differentiation, this is a developmental/ differentiation effect rather than a core acute metabolic function. Should be retained but marked as non-core.
Supporting Evidence:
PMID:11387233
Insulin and glucocorticoids differentially regulate leptin transcription and secretion in brown adipocytes.
GO:0002020 protease binding
IPI
PMID:20082125
In vitro degradation of insulin-like peptide 3 by insulin-de... 		ACCEPT
Summary: Insulin binds to insulin-degrading enzyme (IDE), a metalloprotease that degrades insulin.
Reason: This is a more specific and informative term than generic "protein binding". Binding to IDE is functionally important for insulin clearance and degradation. This is an appropriate annotation.
Supporting Evidence:
PMID:20082125
In vitro degradation of insulin-like peptide 3 by insulin-degrading enzyme.
GO:0045840 positive regulation of mitotic nuclear division
IDA
PMID:10644978
PSM, a mediator of PDGF-BB-, IGF-I-, and insulin-stimulated ... 		KEEP AS NON CORE
Summary: Insulin stimulates mitosis through activation of mitogenic signaling pathways.
Reason: Mitogenic effects are secondary to core metabolic functions, mediated primarily through MAPK pathway. Should be retained but as non-core.
Supporting Evidence:
PMID:10644978
PSM, a mediator of PDGF-BB-, IGF-I-, and insulin-stimulated mitogenesis.
GO:2000252 negative regulation of feeding behavior
IDA
PMID:17957153
Milk intake and feeding behavior in the first week of life a... 		KEEP AS NON CORE
Summary: Insulin acts in the brain to suppress appetite and reduce food intake.
Reason: While insulin's central effects on appetite are physiologically important and contribute to overall energy homeostasis, this is not a direct metabolic function. It's a behavioral/ neurological effect that is peripheral to core function.
Supporting Evidence:
PMID:17957153
Milk intake and feeding behavior in the first week of life and its relationship to cord blood ghrelin, leptin, and insulin concentrations.
GO:0060267 positive regulation of respiratory burst
IDA
PMID:9092559
Insulin-induced activation of NADPH-dependent H2O2 generatio... 		KEEP AS NON CORE
Summary: Insulin can stimulate NADPH oxidase and ROS production in adipocytes.
Reason: Respiratory burst regulation is an immune cell function. While insulin may affect ROS production in some contexts, this is not a core function and may represent a non-specific effect.
Supporting Evidence:
PMID:9092559
Insulin-induced activation of NADPH-dependent H2O2 generation in human adipocyte plasma membranes is mediated by Galphai2.
GO:0030335 positive regulation of cell migration
ISS
PMID:12138094
Insulin/insulin-like growth factor I hybrid receptors have d... 		KEEP AS NON CORE
Summary: Insulin can promote cell migration.
Reason: Cell migration effects are not core metabolic functions. This is a peripheral cellular effect.
Supporting Evidence:
PMID:12138094
2002 Jul 22. Insulin/insulin-like growth factor I hybrid receptors have different biological characteristics depending on the insulin receptor isoform involved.
GO:0043410 positive regulation of MAPK cascade
IDA
PMID:11500939
Regulation of the Akt/Glycogen synthase kinase-3 axis by ins... 		ACCEPT
Summary: Duplicate of earlier MAPK annotation with different reference.
Reason: Additional experimental support for core MAPK pathway activation.
Supporting Evidence:
PMID:11500939
Regulation of the Akt/Glycogen synthase kinase-3 axis by insulin-like growth factor-II via activation of the human insulin receptor isoform-A.
GO:0045840 positive regulation of mitotic nuclear division
IDA
PMID:11500939
Regulation of the Akt/Glycogen synthase kinase-3 axis by ins... 		KEEP AS NON CORE
Summary: Duplicate mitosis annotation.
Reason: Same as earlier - mitogenic effect, not core function.
Supporting Evidence:
PMID:11500939
Regulation of the Akt/Glycogen synthase kinase-3 axis by insulin-like growth factor-II via activation of the human insulin receptor isoform-A.
GO:0051897 positive regulation of phosphatidylinositol 3-kinase/protein kinase B signal transduction
IDA
PMID:11500939
Regulation of the Akt/Glycogen synthase kinase-3 axis by ins... 		ACCEPT
Summary: Another confirmation of PI3K/Akt pathway.
Reason: Additional support for core PI3K/Akt signaling.
Supporting Evidence:
PMID:11500939
Regulation of the Akt/Glycogen synthase kinase-3 axis by insulin-like growth factor-II via activation of the human insulin receptor isoform-A.
GO:0051897 positive regulation of phosphatidylinositol 3-kinase/protein kinase B signal transduction
IDA
PMID:7688386
Insulin and IGF-1 increase mitogenesis and glucose metabolis... 		ACCEPT
Summary: Another PI3K/Akt confirmation.
Reason: Additional support for core pathway.
Supporting Evidence:
PMID:7688386
Insulin and IGF-1 increase mitogenesis and glucose metabolism in the multiple myeloma cell line, RPMI 8226.
GO:0008284 positive regulation of cell population proliferation
IDA
PMID:17925406
Activation of the insulin receptor by insulin and a syntheti... 		KEEP AS NON CORE
Summary: Duplicate proliferation annotation.
Reason: Mitogenic effect, not core metabolic function.
Supporting Evidence:
PMID:17925406
2007 Oct 9. Activation of the insulin receptor by insulin and a synthetic peptide leads to divergent metabolic and mitogenic signaling and responses.
GO:0045725 positive regulation of glycogen biosynthetic process
IDA
PMID:17925406
Activation of the insulin receptor by insulin and a syntheti... 		ACCEPT
Summary: Insulin stimulates glycogen synthesis through activation of glycogen synthase. This is a core metabolic function.
Reason: Glycogen synthesis is a core metabolic function of insulin. In the fed state, insulin promotes storage of glucose as glycogen in liver and muscle, which is essential for glucose homeostasis.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
Simultaneously, insulin activates glycogen synthase through PP1-mediated dephosphorylation, promoting the synthesis of new glycogen from glucose-6-phosphate
file:human/INS/INS-uniprot.txt
It accelerates glycolysis, the pentose phosphate cycle, and glycogen synthesis in liver.
PMID:17925406
2007 Oct 9. Activation of the insulin receptor by insulin and a synthetic peptide leads to divergent metabolic and mitogenic signaling and responses.
GO:0030307 positive regulation of cell growth
NAS
PMID:11742412
Insulin signalling and the regulation of glucose and lipid m... 		KEEP AS NON CORE
Summary: Insulin promotes cell growth through activation of protein synthesis and suppression of protein degradation.
Reason: While insulin does promote cell growth, this is secondary to its core metabolic functions. Growth-promoting effects are mediated through mTOR pathway and protein synthesis machinery.
Supporting Evidence:
PMID:11742412
Insulin signalling and the regulation of glucose and lipid metabolism.
GO:0045597 positive regulation of cell differentiation
NAS
PMID:11742412
Insulin signalling and the regulation of glucose and lipid m... 		KEEP AS NON CORE
Summary: Insulin affects differentiation of various cell types including adipocytes.
Reason: Differentiation effects are developmental rather than acute metabolic functions. Non-core.
Supporting Evidence:
PMID:11742412
Insulin signalling and the regulation of glucose and lipid metabolism.
GO:0045721 negative regulation of gluconeogenesis
NAS
PMID:11742412
Insulin signalling and the regulation of glucose and lipid m... 		ACCEPT
Summary: Insulin suppresses hepatic gluconeogenesis through inhibition of FoxO1 and CREB transcription factors, reducing expression of PEPCK and G6Pase. This is a core metabolic function.
Reason: Suppression of hepatic gluconeogenesis is a core function of insulin, essential for preventing excessive glucose production by the liver in the fed state. This is critical for glucose homeostasis.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
The suppression of hepatic gluconeogenesis by insulin involves inhibition of the transcription factors CREB and FoxO1, which normally activate the expression of the rate-limiting gluconeogenic enzymes phosphoenolpyruvate carboxylase (PEPCK) and glucose-6-phosphatase
file:human/INS/INS-deep-research-perplexity.md
The AKT-mediated phosphorylation and inactivation of FoxO1, combined with reduced CREB activity following insulin treatment, leads to decreased expression of gluconeogenic enzymes and reduced hepatic glucose production
PMID:11742412
Insulin signalling and the regulation of glucose and lipid metabolism.
GO:0046889 positive regulation of lipid biosynthetic process
NAS
PMID:11742412
Insulin signalling and the regulation of glucose and lipid m... 		ACCEPT
Summary: Insulin stimulates lipogenesis through activation of SREBP-1c and lipogenic enzymes including fatty acid synthase and acetyl-CoA carboxylase. This is a core metabolic function.
Reason: Lipogenesis is a core metabolic function of insulin. In the fed state, insulin promotes synthesis of fatty acids and triglycerides for energy storage, which is essential for energy homeostasis.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
Insulin is a potent anabolic hormone that stimulates fatty acid synthesis and triglyceride storage in adipose tissue and liver through multiple transcriptional and post-translational mechanisms
file:human/INS/INS-deep-research-perplexity.md
Upon insulin stimulation, SREBP-1c undergoes proteolytic activation in the Golgi apparatus, releasing the transcriptionally active N-terminal fragment that translocates to the nucleus and activates transcription of genes encoding enzymes required for fatty acid synthesis
PMID:11742412
Insulin signalling and the regulation of glucose and lipid metabolism.
GO:0050995 negative regulation of lipid catabolic process
NAS
PMID:11742412
Insulin signalling and the regulation of glucose and lipid m... 		ACCEPT
Summary: Duplicate of earlier lipolysis inhibition annotation.
Reason: Core metabolic function - inhibition of lipolysis.
Supporting Evidence:
PMID:11742412
Insulin signalling and the regulation of glucose and lipid metabolism.
GO:0060266 negative regulation of respiratory burst involved in inflammatory response
IDA
PMID:11443198
Insulin inhibits intranuclear nuclear factor kappaB and stim... 		KEEP AS NON CORE
Summary: Insulin has anti-inflammatory effects including suppression of inflammatory ROS production.
Reason: Anti-inflammatory effects are not core metabolic functions. These are peripheral effects.
Supporting Evidence:
PMID:11443198
Insulin inhibits intranuclear nuclear factor kappaB and stimulates IkappaB in mononuclear cells in obese subjects: evidence for an anti-inflammatory effect? Dandona P(1), Aljada A, Mohanty P, Ghanim H, Hamouda W, Assian E, Ahmad S.
GO:0045821 positive regulation of glycolytic process
IMP
PMID:381941
A structurally abnormal insulin causing human diabetes. 		ACCEPT
Summary: Insulin stimulates glycolysis by increasing glucose uptake and promoting glycolytic enzyme activity.
Reason: Stimulation of glycolysis is a core metabolic function of insulin. Insulin promotes glucose utilization through glycolysis, which is part of its overall role in glucose homeostasis.
Supporting Evidence:
file:human/INS/INS-uniprot.txt
It accelerates glycolysis, the pentose phosphate cycle, and glycogen synthesis in liver.
PMID:381941
A structurally abnormal insulin causing human diabetes.
GO:0006355 regulation of DNA-templated transcription
NAS
PMID:12881524
Differential gene expression induced by insulin and insulin-... 		KEEP AS NON CORE
Summary: Insulin regulates transcription of many genes.
Reason: This is an extremely broad and non-specific term. While insulin does regulate transcription (e.g., lipogenic genes, gluconeogenic genes), this annotation is too general to be informative. More specific terms about particular genes or pathways would be better.
Supporting Evidence:
PMID:12881524
2003 Jul 24. Differential gene expression induced by insulin and insulin-like growth factor-II through the insulin receptor isoform A.
GO:0007186 G protein-coupled receptor signaling pathway
IDA
PMID:9092559
Insulin-induced activation of NADPH-dependent H2O2 generatio... 		KEEP AS NON CORE
Summary: Study showing insulin-induced NADPH-dependent H2O2 generation is mediated by Gαi2, suggesting crosstalk with GPCR pathways.
Reason: While there may be some crosstalk between insulin signaling and GPCR pathways, insulin itself signals through a receptor tyrosine kinase, not a GPCR. This annotation may represent indirect effects or experimental artifacts. Should be kept but as non-core with skepticism.
Supporting Evidence:
PMID:9092559
Insulin-induced activation of NADPH-dependent H2O2 generation in human adipocyte plasma membranes is mediated by Galphai2.
GO:0006953 acute-phase response
IDA
PMID:14739855
Insulin decreases hepatic acute phase protein levels in seve... 		KEEP AS NON CORE
Summary: Insulin decreases hepatic acute phase protein levels.
Reason: Effects on acute phase response are not core metabolic functions. This is a peripheral effect related to inflammation/stress responses.
Supporting Evidence:
PMID:14739855
Insulin decreases hepatic acute phase protein levels in severely burned children.
GO:0032880 regulation of protein localization
IDA
PMID:14615391
Insulin stimulates glucose transport via nitric oxide/cyclic... 		ACCEPT
Summary: Very broad term covering insulin's effects on protein trafficking including GLUT4 translocation.
Reason: While this is a broad term, it does capture important mechanisms like GLUT4 translocation which are central to insulin action. The term is accurate even if not maximally specific.
Supporting Evidence:
PMID:14615391
Insulin stimulates glucose transport via nitric oxide/cyclic GMP pathway in human vascular smooth muscle cells.
GO:0042060 wound healing
IDA
PMID:9498508
Effects of insulin on wound healing. 		KEEP AS NON CORE
Summary: Insulin has effects on wound healing processes.
Reason: Wound healing effects are not core metabolic functions. These are peripheral tissue repair effects.
Supporting Evidence:
PMID:9498508
Effects of insulin on wound healing.
GO:0046326 positive regulation of D-glucose import across plasma membrane
IDA
PMID:14615391
Insulin stimulates glucose transport via nitric oxide/cyclic... 		ACCEPT
Summary: Duplicate glucose uptake annotation.
Reason: Core function - additional experimental support.
Supporting Evidence:
PMID:14615391
Insulin stimulates glucose transport via nitric oxide/cyclic GMP pathway in human vascular smooth muscle cells.
GO:0050709 negative regulation of protein secretion
IDA
PMID:14739855
Insulin decreases hepatic acute phase protein levels in seve... 		KEEP AS NON CORE
Summary: Insulin can suppress secretion of certain proteins like acute phase proteins.
Reason: Effects on protein secretion are not core functions. This is a peripheral effect.
Supporting Evidence:
PMID:14739855
Insulin decreases hepatic acute phase protein levels in severely burned children.
GO:0055089 fatty acid homeostasis
IMP
PMID:1184755
Glucagon regulation of plasma ketone body concentration in h... 		ACCEPT
Summary: Insulin regulates fatty acid homeostasis through effects on lipogenesis, lipolysis, and fatty acid oxidation.
Reason: Fatty acid homeostasis is a core metabolic function of insulin. Insulin regulates both synthesis and breakdown of fatty acids, which is integral to overall energy homeostasis. This is an appropriate high-level annotation.
Supporting Evidence:
PMID:1184755
Glucagon regulation of plasma ketone body concentration in human diabetes.
GO:0002674 negative regulation of acute inflammatory response
IDA
PMID:11443198
Insulin inhibits intranuclear nuclear factor kappaB and stim... 		KEEP AS NON CORE
Summary: Insulin has anti-inflammatory effects.
Reason: Anti-inflammatory effects are not core metabolic functions.
Supporting Evidence:
PMID:11443198
Insulin inhibits intranuclear nuclear factor kappaB and stimulates IkappaB in mononuclear cells in obese subjects: evidence for an anti-inflammatory effect? Dandona P(1), Aljada A, Mohanty P, Ghanim H, Hamouda W, Assian E, Ahmad S.
GO:0005158 insulin receptor binding
IDA
PMID:9667398
Familial hyperproinsulinaemia due to a mutation substituting... 		ACCEPT
Summary: Direct experimental evidence for insulin receptor binding.
Reason: Additional IDA support for the core molecular function.
Supporting Evidence:
PMID:9667398
Familial hyperproinsulinaemia due to a mutation substituting histidine for arginine at position 65 in proinsulin: identification of the mutation by restriction enzyme mapping.
GO:0005179 hormone activity
IC
PMID:9667398
Familial hyperproinsulinaemia due to a mutation substituting... 		ACCEPT
Summary: Another hormone activity annotation.
Reason: Additional support for hormone activity.
Supporting Evidence:
PMID:9667398
Familial hyperproinsulinaemia due to a mutation substituting histidine for arginine at position 65 in proinsulin: identification of the mutation by restriction enzyme mapping.
GO:0042593 glucose homeostasis
IMP
PMID:381941
A structurally abnormal insulin causing human diabetes. 		ACCEPT
Summary: Study on structurally abnormal insulin causing diabetes demonstrates insulin's role in glucose homeostasis.
Reason: Core function - genetic evidence from natural mutation.
Supporting Evidence:
PMID:381941
A structurally abnormal insulin causing human diabetes.
GO:0045818 negative regulation of glycogen catabolic process
IMP
PMID:381941
A structurally abnormal insulin causing human diabetes. 		ACCEPT
Summary: Insulin inhibits glycogenolysis (glycogen breakdown) in liver and muscle.
Reason: Inhibition of glycogenolysis is a core function of insulin. In the fed state, insulin suppresses glycogen breakdown while promoting glycogen synthesis, which is essential for glucose homeostasis.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
Insulin rapidly inhibits hepatic glycogenolysis through mechanisms involving protein phosphatase-1 (PP1), which is activated through insulin-mediated suppression of glycogen phosphorylase kinase
PMID:381941
A structurally abnormal insulin causing human diabetes.
GO:0045922 negative regulation of fatty acid metabolic process
IMP
PMID:1184755
Glucagon regulation of plasma ketone body concentration in h... 		ACCEPT
Summary: Insulin inhibits fatty acid oxidation and mobilization.
Reason: Suppression of fatty acid oxidation and mobilization (lipolysis) is a core metabolic function. This complements the earlier annotation on inhibition of lipolysis.
Supporting Evidence:
PMID:1184755
Glucagon regulation of plasma ketone body concentration in human diabetes.
GO:0045821 positive regulation of glycolytic process
IDA
PMID:7688386
Insulin and IGF-1 increase mitogenesis and glucose metabolis... 		ACCEPT
Summary: Duplicate glycolysis annotation.
Reason: Core function - additional experimental support.
Supporting Evidence:
PMID:7688386
Insulin and IGF-1 increase mitogenesis and glucose metabolism in the multiple myeloma cell line, RPMI 8226.
GO:0046628 positive regulation of insulin receptor signaling pathway
IDA
PMID:7688386
Insulin and IGF-1 increase mitogenesis and glucose metabolis... 		ACCEPT
Summary: Insulin positively regulates its own receptor signaling pathway by binding and activating the receptor.
Reason: This is essentially describing insulin's primary mechanism of action. While it may seem redundant with "insulin receptor binding" and "insulin receptor signaling pathway", it correctly captures that insulin is the positive regulator of this pathway. Acceptable.
Supporting Evidence:
PMID:7688386
Insulin and IGF-1 increase mitogenesis and glucose metabolism in the multiple myeloma cell line, RPMI 8226.
GO:0005158 insulin receptor binding
IPI
PMID:8452530
Purified hybrid insulin/insulin-like growth factor-I recepto... 		ACCEPT
Summary: Another insulin receptor binding annotation.
Reason: Additional experimental support for core molecular function.
Supporting Evidence:
PMID:8452530
Purified hybrid insulin/insulin-like growth factor-I receptors bind insulin-like growth factor-I, but not insulin, with high affinity.
GO:0005159 insulin-like growth factor receptor binding
IPI
PMID:8452530
Purified hybrid insulin/insulin-like growth factor-I recepto... 		KEEP AS NON CORE
Summary: Study on hybrid insulin/IGF-I receptors. Insulin can bind to IGF-I receptor with lower affinity than to insulin receptor.
Reason: While insulin can bind to IGF-I receptors, particularly hybrid receptors, this is not the primary physiological binding partner. The insulin receptor is the specific high-affinity receptor. IGF-I receptor binding represents cross-reactivity rather than core function.
Supporting Evidence:
PMID:8452530
Purified hybrid insulin/insulin-like growth factor-I receptors bind insulin-like growth factor-I, but not insulin, with high affinity.
GO:0005158 insulin receptor binding
IDA
PMID:7556975
Binding of human, porcine and bovine insulin to insulin rece... 		ACCEPT
Summary: Another insulin receptor binding annotation.
Reason: Additional support for core molecular function.
Supporting Evidence:
PMID:7556975
Binding of human, porcine and bovine insulin to insulin receptors from human brain, muscle and adipocytes and to expressed recombinant alternatively spliced insulin receptor isoforms.
GO:0005576 extracellular region
IC
PMID:7556975
Binding of human, porcine and bovine insulin to insulin rece... 		ACCEPT
Summary: Another extracellular region annotation.
Reason: Additional support for extracellular localization.
Supporting Evidence:
PMID:7556975
Binding of human, porcine and bovine insulin to insulin receptors from human brain, muscle and adipocytes and to expressed recombinant alternatively spliced insulin receptor isoforms.
GO:0007267 cell-cell signaling
IC
PMID:7556975
Binding of human, porcine and bovine insulin to insulin rece... 		ACCEPT
Summary: Insulin functions as a cell-cell signaling molecule, being secreted from beta cells and signaling to distant target cells.
Reason: This is an accurate high-level annotation. Insulin is a classic example of endocrine cell-cell signaling. While not maximally specific, this term correctly categorizes insulin's biological role.
Supporting Evidence:
PMID:7556975
Binding of human, porcine and bovine insulin to insulin receptors from human brain, muscle and adipocytes and to expressed recombinant alternatively spliced insulin receptor isoforms.
GO:0001819 positive regulation of cytokine production
IDA
PMID:15473891
Insulin activates vascular endothelial growth factor in vasc... 		KEEP AS NON CORE
Summary: Insulin can stimulate production of cytokines like VEGF.
Reason: Effects on cytokine production are not core metabolic functions. This represents an immunological/inflammatory effect that is peripheral.
Supporting Evidence:
PMID:15473891
Insulin activates vascular endothelial growth factor in vascular smooth muscle cells: influence of nitric oxide and of insulin resistance.
GO:0042177 negative regulation of protein catabolic process
IDA
PMID:15185208
Intravenous insulin decreases protein breakdown in infants o... 		ACCEPT
Summary: Insulin suppresses protein degradation through inhibition of proteasome and autophagy pathways.
Reason: Suppression of protein degradation is a core anabolic function of insulin. Along with stimulation of protein synthesis, inhibition of protein breakdown contributes to insulin's overall anabolic effects.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
Insulin is also a powerful regulator of protein turnover, stimulating protein synthesis while simultaneously inhibiting protein degradation, thereby promoting net protein anabolism
file:human/INS/INS-deep-research-perplexity.md
In contrast, insulin suppresses hepatic protein degradation through inhibition of the ATP-ubiquitin-dependent proteasome pathway and ATP-independent lysosomal proteases
PMID:15185208
Intravenous insulin decreases protein breakdown in infants on extracorporeal membrane oxygenation.
GO:0046631 alpha-beta T cell activation
IDA
PMID:10604997
Bovine and human insulin activate CD8+-autoreactive CTL expr... 		KEEP AS NON CORE
Summary: Study showing insulin can activate T cells.
Reason: T cell activation is an immunological function, not a core metabolic function. This is a peripheral effect and may even be pathological in the context of type 1 diabetes where insulin can serve as an autoantigen.
Supporting Evidence:
PMID:10604997
Bovine and human insulin activate CD8+-autoreactive CTL expressing both type 1 and type 2 cytokines in C57BL/6 mice.
GO:0050708 regulation of protein secretion
IDA
PMID:15591776
Insulin decreases the secretion of apoB-100 from hepatic Hep... 		KEEP AS NON CORE
Summary: Insulin regulates secretion of various proteins including apolipoproteins.
Reason: While insulin does affect protein secretion in some contexts (e.g., apolipoprotein secretion from hepatocytes), this is not a core function. More specific terms about lipid metabolism would be more appropriate.
Supporting Evidence:
PMID:15591776
Insulin decreases the secretion of apoB-100 from hepatic HepG2 cells but does not decrease the secretion of apoB-48 from intestinal CaCo-2 cells.
GO:0051000 positive regulation of nitric-oxide synthase activity
NAS
PMID:12135947
Insulin-dependent activation of endothelial nitric oxide syn... 		KEEP AS NON CORE
Summary: Insulin activates endothelial nitric oxide synthase (eNOS).
Reason: NO synthase activation is a vascular endothelial effect, not a core metabolic function. This is related to insulin's vascular actions.
Supporting Evidence:
PMID:12135947
Insulin-dependent activation of endothelial nitric oxide synthase is impaired by O-linked glycosylation modification of signaling proteins in human coronary endothelial cells.
GO:1904659 D-glucose transmembrane transport
NAS NEW
Summary: Added to align core_functions with existing annotations.
Reason: Core function term not present in existing_annotations.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
The most physiologically important function of insulin is the stimulation of glucose uptake from the bloodstream into insulin-responsive tissues, particularly skeletal muscle and adipose tissue, which together account for the majority of postprandial glucose disposal. This metabolic action is mediated through the insulin-dependent translocation of glucose transporter type-4 (GLUT4) from intracellular membrane compartments to the plasma membrane
file:human/INS/INS-deep-research-perplexity.md
Following AKT activation, the serine/threonine kinase AS160 (also known as TBC1D4) is phosphorylated by AKT, leading to its release from GLUT4-containing storage vesicles. This phosphorylation event activates the RabGAP activity of AS160, converting Rab small GTPases to their inactive GDP-bound state and enabling GLUT4 vesicle mobilization
GO:0008610 lipid biosynthetic process
NAS NEW
Summary: Added to align core_functions with existing annotations.
Reason: Core function term not present in existing_annotations.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
Insulin is a potent anabolic hormone that stimulates fatty acid synthesis and triglyceride storage in adipose tissue and liver through multiple transcriptional and post-translational mechanisms. The key transcription factors mediating insulin-induced lipogenic gene expression are the sterol regulatory element binding proteins (SREBPs), particularly SREBP-1c in lipogenic tissues
file:human/INS/INS-deep-research-perplexity.md
Reciprocally, insulin potently inhibits lipolysis in adipose tissue through inactivation of hormone-sensitive lipase (HSL) via a PKA-independent mechanism. Insulin-activated AKT phosphorylates and inactivates phosphodiesterase 3B (PDE3B), reducing the degradation of cAMP and preventing PKA activation
GO:0045542 positive regulation of cholesterol biosynthetic process
NAS NEW
Summary: Added to align core_functions with existing annotations.
Reason: Core function term not present in existing_annotations.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
Insulin is a potent anabolic hormone that stimulates fatty acid synthesis and triglyceride storage in adipose tissue and liver through multiple transcriptional and post-translational mechanisms. The key transcription factors mediating insulin-induced lipogenic gene expression are the sterol regulatory element binding proteins (SREBPs), particularly SREBP-1c in lipogenic tissues
file:human/INS/INS-deep-research-perplexity.md
Reciprocally, insulin potently inhibits lipolysis in adipose tissue through inactivation of hormone-sensitive lipase (HSL) via a PKA-independent mechanism. Insulin-activated AKT phosphorylates and inactivates phosphodiesterase 3B (PDE3B), reducing the degradation of cAMP and preventing PKA activation
GO:0010906 regulation of glucose metabolic process
NAS NEW
Summary: Added to align core_functions with existing annotations.
Reason: Core function term not present in existing_annotations.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
Insulin is a potent anabolic hormone that stimulates fatty acid synthesis and triglyceride storage in adipose tissue and liver through multiple transcriptional and post-translational mechanisms. The key transcription factors mediating insulin-induced lipogenic gene expression are the sterol regulatory element binding proteins (SREBPs), particularly SREBP-1c in lipogenic tissues
file:human/INS/INS-deep-research-perplexity.md
Reciprocally, insulin potently inhibits lipolysis in adipose tissue through inactivation of hormone-sensitive lipase (HSL) via a PKA-independent mechanism. Insulin-activated AKT phosphorylates and inactivates phosphodiesterase 3B (PDE3B), reducing the degradation of cAMP and preventing PKA activation
GO:0045727 positive regulation of translation
NAS NEW
Summary: Insulin does not perform translation itself — it positively regulates translation in target cells via the mTOR/S6K1/4E-BP1 axis. Per PR #764 review feedback, the previously proposed NEW GO:0006412 (translation) term has been replaced with GO:0045727 (positive regulation of translation), which correctly captures insulin's regulatory role.
Reason: Insulin signaling positively regulates translation in target tissues; the protein itself does not perform translation.
Supporting Evidence:
file:human/INS/INS-deep-research-perplexity.md
Insulin is also a powerful regulator of protein turnover, stimulating protein synthesis while simultaneously inhibiting protein degradation, thereby promoting net protein anabolism. Insulin stimulates protein synthesis through multiple mechanisms including increased cellular uptake of amino acids through upregulation of amino acid transporters, particularly for branched-chain amino acids (BCAAs) such as leucine
file:human/INS/INS-deep-research-perplexity.md
Following insulin stimulation and increased leucine availability, mTORC1 phosphorylates S6K1 and 4E-BP1, leading to translation initiation factor phosphorylation and enhanced translation of mRNA molecules, particularly those encoding protein synthesis machinery and growth-promoting proteins

Core Functions

Binds insulin receptor with high affinity to activate receptor tyrosine kinase signaling cascades regulating glucose homeostasis

Molecular Function:
insulin receptor binding
Directly Involved In:
glucose homeostasis insulin receptor signaling pathway positive regulation of phosphatidylinositol 3-kinase/protein kinase B signal transduction
Cellular Locations:
extracellular region
Supporting Evidence:
  • file:human/INS/INS-deep-research-perplexity.md
    Insulin binding to site-1, the primary insulin-binding site, is composed of the L1 domain of one α-subunit and the αCT domain of the adjacent α-subunit; insulin binds to this site with high affinity (Kd approximately 10-30 nanomolar)
  • file:human/INS/INS-deep-research-perplexity.md
    Upon binding of a single insulin molecule to site-1, the receptor undergoes a dramatic conformational transition to a Γ-shaped intermediate state, where the FnIII-2 domains move away from the L1 domain, initiating separation of the two receptor protomers. This conformational change brings the two intracellular kinase domains into closer spatial proximity, enabling trans-autophosphorylation
  • file:human/INS/INS-deep-research-perplexity.md
    The phosphatidylinositol 3-kinase (PI3K) pathway represents the primary route through which insulin exerts its metabolic effects, particularly regarding glucose homeostasis, glycogen synthesis, and protein synthesis

Stimulates glucose uptake in muscle and adipose tissue through GLUT4 translocation via PI3K/AKT signaling

Molecular Function:
insulin receptor binding
Directly Involved In:
D-glucose transmembrane transport glucose homeostasis
Cellular Locations:
extracellular region
Supporting Evidence:
  • file:human/INS/INS-deep-research-perplexity.md
    The most physiologically important function of insulin is the stimulation of glucose uptake from the bloodstream into insulin-responsive tissues, particularly skeletal muscle and adipose tissue, which together account for the majority of postprandial glucose disposal. This metabolic action is mediated through the insulin-dependent translocation of glucose transporter type-4 (GLUT4) from intracellular membrane compartments to the plasma membrane
  • file:human/INS/INS-deep-research-perplexity.md
    Following AKT activation, the serine/threonine kinase AS160 (also known as TBC1D4) is phosphorylated by AKT, leading to its release from GLUT4-containing storage vesicles. This phosphorylation event activates the RabGAP activity of AS160, converting Rab small GTPases to their inactive GDP-bound state and enabling GLUT4 vesicle mobilization

Suppresses hepatic glucose production through inhibition of gluconeogenesis and glycogenolysis via AKT-mediated FoxO1 inactivation

Molecular Function:
insulin receptor binding
Directly Involved In:
glucose homeostasis negative regulation of gluconeogenesis
Cellular Locations:
extracellular region
Supporting Evidence:
  • file:human/INS/INS-deep-research-perplexity.md
    The suppression of hepatic gluconeogenesis by insulin involves inhibition of the transcription factors CREB and FoxO1, which normally activate the expression of the rate-limiting gluconeogenic enzymes phosphoenolpyruvate carboxylase (PEPCK) and glucose-6-phosphatase. The AKT-mediated phosphorylation and inactivation of FoxO1, combined with reduced CREB activity following insulin treatment, leads to decreased expression of gluconeogenic enzymes and reduced hepatic glucose production
  • file:human/INS/INS-deep-research-perplexity.md
    Insulin rapidly inhibits hepatic glycogenolysis through mechanisms involving protein phosphatase-1 (PP1), which is activated through insulin-mediated suppression of glycogen phosphorylase kinase, thereby preventing phosphorylation of glycogen phosphorylase and allowing its inactivation

Promotes lipogenesis and inhibits lipolysis in adipose tissue through SREBP-1c activation and HSL inactivation

Molecular Function:
insulin receptor binding
Directly Involved In:
lipid biosynthetic process positive regulation of cholesterol biosynthetic process regulation of glucose metabolic process
Cellular Locations:
extracellular region
Supporting Evidence:
  • file:human/INS/INS-deep-research-perplexity.md
    Insulin is a potent anabolic hormone that stimulates fatty acid synthesis and triglyceride storage in adipose tissue and liver through multiple transcriptional and post-translational mechanisms. The key transcription factors mediating insulin-induced lipogenic gene expression are the sterol regulatory element binding proteins (SREBPs), particularly SREBP-1c in lipogenic tissues
  • file:human/INS/INS-deep-research-perplexity.md
    Reciprocally, insulin potently inhibits lipolysis in adipose tissue through inactivation of hormone-sensitive lipase (HSL) via a PKA-independent mechanism. Insulin-activated AKT phosphorylates and inactivates phosphodiesterase 3B (PDE3B), reducing the degradation of cAMP and preventing PKA activation

Stimulates protein synthesis and inhibits protein degradation through mTORC1 activation and FoxO1 suppression

Molecular Function:
insulin receptor binding
Directly Involved In:
positive regulation of translation
Cellular Locations:
extracellular region
Supporting Evidence:
  • file:human/INS/INS-deep-research-perplexity.md
    Insulin is also a powerful regulator of protein turnover, stimulating protein synthesis while simultaneously inhibiting protein degradation, thereby promoting net protein anabolism. Insulin stimulates protein synthesis through multiple mechanisms including increased cellular uptake of amino acids through upregulation of amino acid transporters, particularly for branched-chain amino acids (BCAAs) such as leucine
  • file:human/INS/INS-deep-research-perplexity.md
    Following insulin stimulation and increased leucine availability, mTORC1 phosphorylates S6K1 and 4E-BP1, leading to translation initiation factor phosphorylation and enhanced translation of mRNA molecules, particularly those encoding protein synthesis machinery and growth-promoting proteins

References

GO_REF:0000033
Annotation inferences using phylogenetic trees
GO_REF:0000043
Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
GO_REF:0000117
Electronic Gene Ontology annotations created by ARBA machine learning models
GO_REF:0000120
Combined Automated Annotation using Multiple IEA Methods
file:human/INS/INS-deep-research-perplexity.md
Deep research on human insulin gene
file:human/INS/INS-deep-research-falcon.md
Falcon deep research report on human INS (Edison Scientific Literature, May 2026)
  • Preproinsulin matures via signal peptide cleavage in the ER lumen, proinsulin folding with three disulfide bonds, trafficking through Golgi/TGN, packaging into immature secretory granules, and proteolytic processing by PC1/3, PC2 and carboxypeptidase E to yield mature insulin and C-peptide.
    "INS encodes preproinsulin, a single-chain precursor that enters the regulated secretory pathway. After co-translational targeting to the rough ER, the signal peptide is removed to generate proinsulin, which folds in the ER and forms three disulfide bonds. Proinsulin then traffics through the Golgi and is packaged into secretory granules, where endoproteolytic processing yields mature insulin and C-peptide."
  • Mature insulin binds the insulin receptor (INSR) and activates two main downstream branches — PI3K→AKT (metabolic) and RAS→RAF→MEK→ERK (mitogenic).
    "Insulin acts mainly by binding INSR, which autophosphorylates and recruits adaptor proteins (IRS, Shc), bifurcating into: PI3K→PIP3→AKT (metabolic branch): GLUT4 translocation, glycogen synthesis regulation via GSK3, mTOR-mediated protein synthesis, and transcriptional programs (e.g., FOXO regulation). RAS→RAF→MEK→ERK (MAPK) (mitogenic branch): growth/proliferation and gene-expression programs."
  • Insulin biogenesis is coupled to β-cell ER folding capacity, redox state, ER Ca2+ homeostasis, and secretory trafficking; chronic hyperglycemia selectively suppresses translation of insulin and secretion-related mRNAs prior to global translational collapse.
    "Its biosynthesis is tightly coupled to ER folding capacity, redox state, ER Ca2+ homeostasis, and secretory trafficking; recent 2023–2024 work clarifies how metabolism-driven redox buffering, chronic hyperglycemia-induced translational programs, and cargo condensation mechanisms can regulate or impair insulin production and secretion."
file:human/INS/INS-uniprot.txt
UniProt entry for human insulin
PMID:37159024
Condensation of the β-cell secretory granule luminal cargoes pro/insulin and ICA512 RESP18 homology domain.
  • Proinsulin co-condenses with ICA512 RESP18HD at pH 6.8 to form micron-scale luminal condensates, suggesting proinsulin is an early driver of insulin secretory granule biogenesis via phase separation in the early secretory pathway.
    "proinsulin is an early driver of insulin SG biogenesis, in a process in which its co-condensation with RESP18HD participates in their phase separation from other secretory proteins in transit through the same compartments but destined to other routes."
PMID:38032734
Sustained hyperglycemia specifically targets translation of mRNAs for insulin secretion.
  • Chronic high glucose suppresses translation of insulin and of mRNAs required for secretory granule formation, exocytosis, and metabolism-coupled insulin secretion in β-cells, before induction of ER stress or global translational collapse.
    "Before induction of ER stress or suppression of global translation, sustained high glucose suppressed glucose-stimulated insulin secretion and downregulated translation of not only insulin, but also mRNAs related to insulin secretory granule formation, exocytosis, and metabolism-coupled insulin secretion."
PMID:38397072
Changes in Cells Associated with Insulin Resistance.
  • Insulin is a polypeptide hormone synthesized and secreted by pancreatic β-cells that regulates plasma glucose, fat, ketone body, and protein metabolism.
    "Insulin is a polypeptide hormone synthesized and secreted by pancreatic β-cells. It plays an important role as a metabolic hormone. Insulin influences the metabolism of glucose, regulating plasma glucose levels and stimulating glucose storage in organs such as the liver, muscles and adipose tissue."
PMID:38507587
The Ailing β-Cell in Diabetes: Insights From a Trip to the ER: The 2023 Outstanding Scientific Achievement Award Lecture.
  • SERCA-regulated ER calcium dynamics are required for normal proinsulin processing and trafficking in β-cells; disruption underlies β-cell stress in diabetes pathophysiology.
    "a role for the sarcoendoplasmic reticulum calcium ATPase (SERCA) pump in the regulation of endoplasmic reticulum (ER) calcium, protein trafficking, and proinsulin processing within the β-cell."
PMID:38935435
A metabolic redox relay supports ER proinsulin export in pancreatic islet β cells.
  • Glucose metabolism supplies reductive donors (NADPH, thioredoxin flux) that buffer ER redox; ER hyperoxidation delays proinsulin export and limits insulin granule formation.
    "Hyperoxidation of the ER delays proinsulin export and limits the proinsulin supply available for insulin granule formation. In this report, we identified glucose metabolism as a critical determinant in the redox homeostasis of the ER."
PMID:40052150
Molecular puzzle of insulin: structural assembly pathways and their role in diabetes.
  • Preproinsulin synthesis begins in pancreatic β-cells with ER translocation and signal peptide cleavage; proinsulin folds in the ER, an environment optimized to support disulfide bond formation and minimize misfolding.
    "Proinsulin foldability is optimized in the ER, an environment evolved to support the folding process and the formation of disulfide bonds while minimizing misfolding."
PMID:10508408
Structural consequences of the B5 histidine --> tyrosine mutation in human insulin characterized by X-ray crystallography and conformational analysis.
PMID:10604997
Bovine and human insulin activate CD8+-autoreactive CTL expressing both type 1 and type 2 cytokines in C57BL/6 mice.
PMID:10644978
PSM, a mediator of PDGF-BB-, IGF-I-, and insulin-stimulated mitogenesis.
PMID:11387233
Insulin and glucocorticoids differentially regulate leptin transcription and secretion in brown adipocytes.
PMID:11443198
Insulin inhibits intranuclear nuclear factor kappaB and stimulates IkappaB in mononuclear cells in obese subjects: evidence for an anti-inflammatory effect?
PMID:11500939
Regulation of the Akt/Glycogen synthase kinase-3 axis by insulin-like growth factor-II via activation of the human insulin receptor isoform-A.
PMID:11742412
Insulin signalling and the regulation of glucose and lipid metabolism.
PMID:1184755
Glucagon regulation of plasma ketone body concentration in human diabetes.
PMID:12135947
Insulin-dependent activation of endothelial nitric oxide synthase is impaired by O-linked glycosylation modification of signaling proteins in human coronary endothelial cells.
PMID:12138094
Insulin/insulin-like growth factor I hybrid receptors have different biological characteristics depending on the insulin receptor isoform involved.
PMID:12881524
Differential gene expression induced by insulin and insulin-like growth factor-II through the insulin receptor isoform A.
PMID:12946932
Insulin impairs endothelium-dependent vasodilation independent of insulin sensitivity or lipid profile.
PMID:14615391
Insulin stimulates glucose transport via nitric oxide/cyclic GMP pathway in human vascular smooth muscle cells.
PMID:14739855
Insulin decreases hepatic acute phase protein levels in severely burned children.
PMID:14744991
Insulin induces the release of vasodilator compounds from platelets by a nitric oxide-G kinase-VAMP-3-dependent pathway.
PMID:14986111
Impaired binding of insulin to erythrocyte membrane receptor and the activation of nitric oxide synthase by the hormone in human breast cancer.
PMID:15185208
Intravenous insulin decreases protein breakdown in infants on extracorporeal membrane oxygenation.
PMID:15473891
Insulin activates vascular endothelial growth factor in vascular smooth muscle cells: influence of nitric oxide and of insulin resistance.
PMID:15591776
Insulin decreases the secretion of apoB-100 from hepatic HepG2 cells but does not decrease the secretion of apoB-48 from intestinal CaCo-2 cells.
PMID:15792832
Insulin and nitric oxide stimulates glucose transport in human placenta.
PMID:16604263
Neuroprotection of insulin against oxidative stress-induced apoptosis in cultured retinal neurons: involvement of phosphoinositide 3-kinase/Akt signal pathway.
PMID:17051221
Structures of human insulin-degrading enzyme reveal a new substrate recognition mechanism.
PMID:17472440
A helical structural nucleus is the primary elongating unit of insulin amyloid fibrils.
PMID:17925406
Activation of the insulin receptor by insulin and a synthetic peptide leads to divergent metabolic and mitogenic signaling and responses.
PMID:17957153
Milk intake and feeding behavior in the first week of life and its relationship to cord blood ghrelin, leptin, and insulin concentrations.
PMID:19188609
Protection of synapses against Alzheimer's-linked toxins: insulin signaling prevents the pathogenic binding of Abeta oligomers.
PMID:19727662
Extracellular PBEF/NAMPT/visfatin activates pro-inflammatory signalling in human vascular smooth muscle cells through nicotinamide phosphoribosyltransferase activity.
PMID:20082125
In vitro degradation of insulin-like peptide 3 by insulin-degrading enzyme.
PMID:20455999
A novel domain of caveolin-2 that controls nuclear targeting: regulation of insulin-specific ERK activation and nuclear translocation by caveolin-2.
PMID:20738396
Structural features of proinsulin C-peptide oligomeric and amyloid states.
PMID:22854022
SERF protein is a direct modifier of amyloid fiber assembly.
PMID:23106816
Insulin solubility transitions by pH-dependent interactions with proinsulin C-peptide.
PMID:23302862
How insulin engages its primary binding site on the insulin receptor.
PMID:23416304
Amino acid sequence determinants in self-assembly of insulin chiral amyloid superstructures: role of C-terminus of B-chain in association of fibrils.
PMID:23510797
Peptides that form β-sheets on hydrophobic surfaces accelerate surface-induced insulin amyloidal aggregation.
PMID:24675707
Resistin in dairy cows: plasma concentrations during early lactation, expression and potential role in adipose tissue.
PMID:25240198
Saturated fatty acid-induced miR-195 impairs insulin signaling and glycogen metabolism in HepG2 cells.
PMID:25403480
Glucose tolerance is associated with differential expression of microRNAs in skeletal muscle: results from studies of twins with and without type 2 diabetes.
PMID:29512653
Structure of the insulin receptor-insulin complex by single-particle cryo-EM analysis.
PMID:31501273
MicroRNA 7 Impairs Insulin Signaling and Regulates Aβ Levels through Posttranscriptional Regulation of the Insulin Receptor Substrate 2, Insulin Receptor, Insulin-Degrading Enzyme, and Liver X Receptor Pathway.
PMID:32296183
A reference map of the human binary protein interactome.
PMID:36250347
Insulin stimulates atypical protein kinase C-mediated phosphorylation of the neuronal adaptor FE65 to potentiate neurite outgrowth by activating ARF6-Rac1 signaling.
PMID:381941
A structurally abnormal insulin causing human diabetes.
PMID:7556975
Binding of human, porcine and bovine insulin to insulin receptors from human brain, muscle and adipocytes and to expressed recombinant alternatively spliced insulin receptor isoforms.
PMID:7688386
Insulin and IGF-1 increase mitogenesis and glucose metabolism in the multiple myeloma cell line, RPMI 8226.
PMID:8452530
Purified hybrid insulin/insulin-like growth factor-I receptors bind insulin-like growth factor-I, but not insulin, with high affinity.
PMID:8702995
Akt, a pleckstrin homology domain containing kinase, is activated primarily by phosphorylation.
PMID:8844841
A novel complex of a phenolic derivative with insulin: structural features related to the T-->R transition.
PMID:9092559
Insulin-induced activation of NADPH-dependent H2O2 generation in human adipocyte plasma membranes is mediated by Galphai2.
PMID:9388210
Inhibition of insulin receptor activation by insulin-like growth factor binding proteins.
PMID:9498508
Effects of insulin on wound healing.
PMID:9667398
Familial hyperproinsulinaemia due to a mutation substituting histidine for arginine at position 65 in proinsulin: identification of the mutation by restriction enzyme mapping.
PMID:9773776
Megalin is an endocytic receptor for insulin.
Reactome:R-HSA-110011
Binding of Grb10 to the insulin receptor
Reactome:R-HSA-264976
Proinsulin binds zinc and calcium forming Proinsulin:zinc:calcium
Reactome:R-HSA-264997
P4HB mediates disulfide bond formation in Proinsulin
Reactome:R-HSA-265010
Proinsulin translocates from the endoplasmic reticulum to the Golgi
Reactome:R-HSA-265153
Proinsulin:Zinc:Calcium complex translocates to immature secretory granule
Reactome:R-HSA-6807875
ARFGAP, cargo, v-SNAREs and p24 proteins bind nascent COPI complex
Reactome:R-HSA-6807877
ARFGAPs stimulate ARF GTPase activity
Reactome:R-HSA-6809003
ERGIC-to-Golgi vesicles bind dynein:dynactin
Reactome:R-HSA-6809006
Vesicle is tethered through binding GOLGA2:GORASP1, GOLGB1 and the COG complex
Reactome:R-HSA-6809010
COPI vesicle uncoating
Reactome:R-HSA-6809011
cis-Golgi t-SNAREs bind YKT6 on tethered vesicle
Reactome:R-HSA-74707
Binding of IRS to insulin receptor
Reactome:R-HSA-74711
Phosphorylation of IRS
Reactome:R-HSA-74712
Dissociation of IRS-P from insulin receptor
Reactome:R-HSA-74715
Autophosphorylation of insulin receptor
Reactome:R-HSA-74716
Insulin binds the insulin receptor
Reactome:R-HSA-74718
Internalisation of the insulin receptor
Reactome:R-HSA-74726
Dissociation of insulin from insulin receptor
Reactome:R-HSA-74730
Insulin degradation
Reactome:R-HSA-74740
Binding of SHC1 to insulin receptor
Reactome:R-HSA-74742
Phosphorylation of SHC1
Reactome:R-HSA-74743
Dissociation of p-Y427-SHC1 from insulin receptor
Reactome:R-HSA-976734
Amyloid fibrils have additional components
Reactome:R-HSA-977136
Amyloid precursor proteins form ordered fibrils
Reactome:R-NUL-9023165
Pcsk1 (rat) cleaves human proinsulin to yield Insulin(25-56) and Insulin(57-110)
Reactome:R-NUL-9023166
Carboxypeptidase E (rat Carboxypeptidase H) cleaves Insulin(25-56) to yield Insulin(25-54)
Reactome:R-NUL-9023180
Pcsk2 (rat) cleaves human Insulin(57-110) to yield Insulin(90-110) and C-peptide (Insulin(57-89))
Reactome:R-NUL-9023186
Carboxypeptidase E (rat Carboxypeptidase H) cleaves C-peptide (Insulin(57-89)) to yield C-peptide (Insulin(57-87))

Deep Research

Falcon

(INS-deep-research-falcon.md)
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate. Falcon Edison Scientific Literature 53 citations 3 artifacts 2026-05-29T19:13:28.429777
Edison artifact artifact-00 (text/markdown)
Edison artifact artifact-01 (text/markdown)
## Context ID: pqac-00000040 I have extracted Figure 1 from page 3, which illustrates the closed-loop ecosystem. This schematic includes a central panel specifi (image/png)

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Research Report: Human INS (UniProt P01308) — Functional Annotation, Biology, and Applications (focus on 2023–2024)

0) Identity verification (critical disambiguation)

The target is human insulin encoded by INS (UniProt P01308) and synthesized as preproinsulin, a secreted peptide hormone precursor that is proteolytically processed to the mature insulin A and B chains plus C-peptide. Multiple sources explicitly describe the canonical preproinsulin organization (signal peptide + B chain + C-peptide + A chain), ER targeting/processing, granule storage, and regulated secretion in pancreatic β-cells, matching the UniProt description and insulin-family context. (urbaniak2025molecularpuzzleof pages 3-6, urbaniak2025molecularpuzzleof pages 2-3, ayan2023abriefatlas pages 2-3)

1) Key concepts and definitions (current understanding)

1.1 INS gene product and maturation pathway

INS encodes preproinsulin, a single-chain precursor that enters the regulated secretory pathway. After co-translational targeting to the rough ER, the signal peptide is removed to generate proinsulin, which folds in the ER and forms three disulfide bonds. Proinsulin then traffics through the Golgi and is packaged into secretory granules, where endoproteolytic processing yields mature insulin and C-peptide. (urbaniak2025molecularpuzzleof pages 2-3, ayan2023abriefatlas pages 2-3, szablewski2024changesincells pages 2-4)

A key definitional distinction:
- Preproinsulin: signal peptide-containing translation product targeted to the ER. (urbaniak2025molecularpuzzleof pages 2-3, ayan2023abriefatlas pages 2-3)
- Proinsulin: ER-luminal folding intermediate; precursor that contains B chain, C-peptide, and A chain. (ayan2023abriefatlas pages 2-3, szablewski2024changesincells pages 2-4)
- Mature insulin: disulfide-linked A and B chains; stored in granules (often as zinc-stabilized hexamers) and secreted upon stimulation. (ayan2023abriefatlas pages 2-3, urbaniak2025molecularpuzzleof pages 7-8)

Processing enzymes (canonical): prohormone convertases PC1/3 and PC2 cleave junctions flanking the C-peptide, and carboxypeptidase E (CPE) trims basic residues to yield mature insulin and C-peptide. (prefontaine2024investigatingtherelationship pages 8-13, szablewski2024changesincells pages 2-4, urbaniak2025molecularpuzzleof pages 7-8)

1.2 Subcellular localization of INS function

The INS product is primarily synthesized and matured across multiple compartments:
- Rough ER/ER lumen: signal peptide cleavage, oxidative folding, disulfide bond formation, quality control. (urbaniak2025molecularpuzzleof pages 2-3, rohli2024ametabolicredox pages 1-2)
- Golgi/TGN: trafficking and packaging into immature secretory granules. (ayan2023abriefatlas pages 2-3, urbaniak2025molecularpuzzleof pages 7-8)
- Immature/maturing secretory granules: proteolytic conversion of proinsulin → insulin + C-peptide; granule acidification/condensation and storage. (szablewski2024changesincells pages 2-4, urbaniak2025molecularpuzzleof pages 7-8)
- Plasma membrane/extracellular: Ca2+-triggered exocytosis releases insulin to circulation; insulin acts as a ligand for the insulin receptor in peripheral tissues. (szablewski2024changesincells pages 2-4, sakaguchi2024theroleof pages 1-3)

1.3 Glucose-stimulated insulin secretion (GSIS) and biphasic release

A core concept is biphasic insulin secretion:
- Triggering (first) phase: glucose metabolism increases ATP, closes KATP channels, depolarizes the β-cell, opens voltage-gated Ca2+ channels, and triggers exocytosis of a readily releasable granule pool. (dalle2024receptorsandsignaling pages 2-4, aamodt2023peelingtheonion pages 1-2)
- Amplifying (second) phase: sustained secretion driven by metabolic coupling factors and cytoskeletal/granule mobilization processes; involves actin remodeling and small GTPases. (szablewski2024changesincells pages 2-4, dalle2024receptorsandsignaling pages 2-4)

1.4 Downstream signaling: insulin receptor pathway

Insulin acts mainly by binding INSR, which autophosphorylates and recruits adaptor proteins (IRS, Shc), bifurcating into:
- PI3K→PIP3→AKT (metabolic branch): GLUT4 translocation, glycogen synthesis regulation via GSK3, mTOR-mediated protein synthesis, and transcriptional programs (e.g., FOXO regulation). (sakaguchi2024theroleof pages 1-3, szablewski2024changesincells pages 4-6, caturano2024insulin–heartaxisbridging pages 2-3)
- RAS→RAF→MEK→ERK (MAPK) (mitogenic branch): growth/proliferation and gene-expression programs. (sakaguchi2024theroleof pages 1-3, szablewski2024changesincells pages 4-6)

2) Recent developments and latest research (prioritizing 2023–2024)

2.1 Metabolism–redox coupling in ER proinsulin export (2024)

A major mechanistic advance is the explicit coupling of cellular metabolism to ER redox homeostasis, which in turn governs proinsulin export and insulin granule biogenesis. Rohli et al. (JCI Insight, 2024-06, https://doi.org/10.1172/jci.insight.178725) report that ER hyperoxidation delays proinsulin export; mitochondrial metabolism supplies reductive donors (e.g., NADPH/thioredoxin flux) that buffer ER redox to support proinsulin trafficking and granule formation. The study notes the folding challenge: a substantial fraction of proinsulin is misfolded and degraded even physiologically, making ER redox control central to insulin biogenesis. (rohli2024ametabolicredox pages 1-2)

2.2 ER calcium homeostasis and proinsulin processing (2024)

Evans-Molina (Diabetes, 2024-03, https://doi.org/10.2337/dbi23-0030) summarizes mechanistic work linking SERCA2/ER calcium to prohormone convertase maturation, ER→Golgi trafficking, and proinsulin processing; SERCA2 deficiency elevates proinsulin-to-insulin ratios and disrupts convertase activity/localization, implicating ER calcium as an upstream regulator of insulin maturation and secretory competence. (evansmolina2024theailingβcell pages 4-5, evansmolina2024theailingβcell pages 1-2)

2.3 Translational reprogramming in chronic hyperglycemia (“glucose toxicity”) (2024)

Cheruiyot et al. (JCI, 2024-11, https://doi.org/10.1172/jci173280) report that sustained hyperglycemia suppresses translation of not only insulin but also mRNAs required for secretory granule formation, exocytosis, and metabolism-coupled secretion, before global translation suppression and prior to ER stress. This identifies a targeted translational circuit contributing to β-cell secretory failure under chronic high glucose. (cheruiyot2024sustainedhyperglycemiaspecifically pages 1-2)

2.4 Phase separation/condensation and granule biogenesis (2023)

Toledo et al. (Protein Science, 2023-05, https://doi.org/10.1002/pro.4649) provide biophysical evidence that proinsulin/insulin can form condensates with the ICA512 RESP18 homology domain, supporting the idea that condensation/phase separation in early secretory compartments may contribute to secretory granule biogenesis, while requiring ER chaperoning to prevent premature condensation that would interfere with correct folding. (toledo2023condensationofthe pages 1-2)

3) Current applications and real-world implementations

3.1 Therapeutic insulin and insulin analogs

Clinical insulin therapy uses engineered formulations spanning rapid/ultra-rapid prandial analogs and long-acting basal analogs. ADA Standards of Care (Diabetes Care, 2024-12, https://doi.org/10.2337/dc24-s009) describe that rapid-acting analogs and ultra-rapid formulations improve postprandial control versus regular human insulin, and basal analogs such as U-300 glargine and degludec may reduce hypoglycemia risk versus U-100 glargine. (elsayed20249.pharmacologicapproaches pages 1-2)

3.2 Diabetes technology: CGM, pumps (CSII), and automated insulin delivery (AID)

The 2024 ADA Standards define diabetes technology to include CGM, insulin pumps, AID (closed-loop) systems, and connected pens, emphasizing that benefit requires education and support; consistent CGM access is important, as interruptions are associated with worsening outcomes, and backup blood glucose monitoring should be maintained. (Diabetes Care, 2024-12, https://doi.org/10.2337/dc24-s007) (elsayed20247.diabetestechnology pages 1-2, elsayed20247.diabetestechnology pages 1-1)

Automated insulin delivery (AID) as real-world implementation:
- AID/closed-loop systems are increasingly used in routine care for type 1 diabetes, and are expanding to other indications. (boughton2024theroleof pages 1-2, kadiyala2024closedloopsystemsrecent pages 1-2)
- AID systems consist of CGM + algorithm + pump, modulating insulin delivery every 5–10 minutes; current commercial systems are hybrid (need meal input). (kadiyala2024closedloopsystemsrecent pages 1-2)

A key implementation theme from expert reviews is that outcomes depend on both device performance and the broader “ecosystem”: training, support, data-sharing, clinic resources, and connectivity reliability. (boughton2024theroleof pages 1-2)

4) Expert opinions and authoritative analyses (2023–2024)

4.1 Technology guidance and clinical standards (ADA & ISPAD, 2024)

  • ADA Standards (2024) position early CGM initiation (even at diagnosis) as standard-of-care for most people with type 1 diabetes, and highlight clinician competency/training needs due to device complexity. (elsayed20249.pharmacologicapproaches pages 1-2, elsayed20247.diabetestechnology pages 1-1)
  • ISPAD 2024 guidelines (Hormone Research in Paediatrics, 2024-12, https://doi.org/10.1159/000543034) recommend pump therapy for youth regardless of age or baseline HbA1c, emphasize infusion-set failure/DKA risk, and explicitly discuss disparities in access and reimbursement as implementation bottlenecks. (biester2024ispadclinicalpractice pages 2-3)

4.2 Closed-loop expert review perspective (2024)

Boughton & Hovorka (Diabetologia, 2024-05, https://doi.org/10.1007/s00125-024-06165-w) emphasize that real-world outcomes generally mirror trial results, but scaling AID requires addressing the full device-support ecosystem (training, customer support, data systems) and access inequities. (boughton2024theroleof pages 1-2)

5) Recent quantitative statistics and data points (from 2023–2024 sources)

5.1 Glycemic target attainment remains low (implementation gap)

  • Registry data in a 2024 closed-loop review report that only 26% of people with type 1 diabetes met HbA1c <7% in 2021–2022, underscoring persistent unmet need. (kadiyala2024closedloopsystemsrecent pages 1-2)
  • A 2024 pilot-system dissertation-style source cites Type 1 Diabetes Exchange registry (n=22,697; 2016–2018) target attainment of 17% (youth) and 21% (adults) meeting HbA1c targets. (odabassian2024pilotoutpatientassessment pages 22-26)

5.2 Quantitative benefits of AID/closed-loop systems

  • A 2024 Expert Review of Medical Devices paper reports RCT/real-world improvements in time-in-range (70–180 mg/dL) of approximately +6 to +28 percentage points, with HbA1c reductions of approximately 0.1 to 1.4 percentage points (range depends on population/comparator). (kadiyala2024closedloopsystemsrecent pages 1-2)
  • A 2024 Diabetologia review reports meta-analyses showing hybrid closed-loop improves time-in-range by approximately +8 to +12 percentage points, reduces hyperglycemia and mean glucose, and does not increase (and may reduce) hypoglycemia. (boughton2024theroleof pages 1-2)

5.3 CGM target metrics used in practice

A 2024 source summarizes widely used CGM targets: TIR >70% (3.9–10.0 mmol/L), time <3.9 mmol/L <4%, and time <3.0 mmol/L <1%. (odabassian2024pilotoutpatientassessment pages 22-26)

5.4 Quantitative biomarker changes reflecting β-cell function/stress (2023 trial)

In SURPASS-1 (Journal of the Endocrine Society, 2023-03, https://doi.org/10.1210/jendso/bvad056), tirzepatide monotherapy at 40 weeks reduced fasting proinsulin by ~49% and reduced proinsulin/C-peptide ratio by ~46–49% vs ~0% change with placebo, consistent with reduced β-cell stress and improved processing. (lee2023tirzepatideasmonotherapy pages 5-6, lee2023tirzepatideasmonotherapy pages 3-4)

Visual evidence: AID/closed-loop ecosystem

The figure below provides a schematic of the closed-loop ecosystem (sensor → algorithm → pump, plus supporting data/training/healthcare infrastructure), reflecting how real-world performance depends on the combined system.
(boughton2024theroleof media 294504cd)

Summary tables (artifacts)

The following tables consolidate the functional annotation and pathway context.

Process/Function Key molecular steps Key molecules/enzymes Subcellular localization Evidence/source (short cite with year)
Preproinsulin synthesis and ER targeting INS is translated as a 110-aa preproinsulin; N-terminal signal peptide directs cotranslational translocation into ER, where signal peptide is cleaved to form proinsulin Signal peptide, SRP/translocon, signal peptidase Rough ER / ER lumen of pancreatic β-cells Ayan 2023; Urbaniak 2025 (ayan2023abriefatlas pages 2-3, urbaniak2025molecularpuzzleof pages 2-3)
Proinsulin folding and disulfide bond formation Proinsulin folds in ER and forms three essential disulfide bonds; misfolded molecules are retained/degraded, linking folding efficiency to insulin output PDI, ER oxidoreductases, chaperones (e.g., BiP/GRP78, GRP94) ER lumen Urbaniak 2025; Rohli 2024 (urbaniak2025molecularpuzzleof pages 3-6, rohli2024ametabolicredox pages 1-2)
Metabolic support for proinsulin export Mitochondrial metabolism supplies reductive power needed to maintain ER redox; ER hyperoxidation delays proinsulin export and reduces granule biogenesis NADPH, thioredoxin system, mitochondrial metabolism, ERO1/PDI network ER linked to mitochondrial metabolic pathways Rohli 2024 (rohli2024ametabolicredox pages 1-2)
ER stress and trafficking control Chronic ER Ca2+ defects impair convertase maturation, proinsulin trafficking, and increase proinsulin/insulin ratio; altered ER→Golgi trafficking contributes to β-cell dysfunction SERCA2, PC1/3, PC2, ER Ca2+ handling machinery ER, cis-Golgi, intermediate secretory compartments Evans-Molina 2024 (evansmolina2024theailingβcell pages 1-2, evansmolina2024theailingβcell pages 4-5)
Golgi trafficking and granule maturation Folded proinsulin exits ER, traffics through Golgi/TGN, and is packaged into immature secretory granules for maturation COPII machinery, Golgi sorting factors, Zn2+, Ca2+ Golgi, trans-Golgi network, immature granules Urbaniak 2025; Ayan 2023 (urbaniak2025molecularpuzzleof pages 7-8, ayan2023abriefatlas pages 2-3)
Proteolytic processing to mature insulin Proinsulin is cleaved at B-chain/C-peptide and C-peptide/A-chain junctions; dibasic residues are removed to yield mature disulfide-linked insulin A and B chains plus C-peptide PC1/3, PC2, carboxypeptidase E/CPE Immature/maturing secretory granules Szablewski 2024; Ayan 2023; Urbaniak 2025 (szablewski2024changesincells pages 2-4, ayan2023abriefatlas pages 2-3, urbaniak2025molecularpuzzleof pages 7-8)
Secretory granule condensation/biogenesis Proinsulin has intrinsic self-condensation tendency; co-condensation with ICA512 RESP18HD may help segregate cargo and drive early secretory granule formation Proinsulin/insulin, ICA512 RESP18HD Early secretory pathway / nascent secretory granules Toledo 2023 (toledo2023condensationofthe pages 1-2)
Glucose-stimulated insulin secretion (triggering phase) Glucose metabolism raises ATP, closes KATP channels, depolarizes membrane, opens voltage-gated Ca2+ channels, and triggers exocytosis of readily releasable granules GLUT1/2, glucokinase, KATP channels, VDCCs, Ca2+ Plasma membrane, cytosol, docked insulin granules Dalle 2024; Szablewski 2024 (dalle2024receptorsandsignaling pages 2-4, szablewski2024changesincells pages 2-4)
Biphasic/amplified secretion First phase releases pre-docked granules; second phase recruits reserve granules via metabolic coupling factors and cytoskeletal remodeling Cdc42, Rac1, NAD(P)H/NADPH, PLC/PKC, cAMP Cortical actin network, cytoplasm, plasma membrane Szablewski 2024; Dalle 2024 (szablewski2024changesincells pages 2-4, dalle2024receptorsandsignaling pages 2-4)
Translational adaptation and glucose toxicity Acute glucose enhances translation of proinsulin and secretion-related proteins; sustained hyperglycemia selectively suppresses translation of insulin, granule biogenesis, exocytosis, and coupling-factor mRNAs before global translational collapse Insulin mRNA 5′UTR regulatory elements, secretion-pathway mRNAs Cytosol/ribosomes with downstream effects on ER-granule pathway Cheruiyot 2024 (cheruiyot2024sustainedhyperglycemiaspecifically pages 1-2)
Endocrine signaling function after secretion Mature insulin is released to circulation, dissociates to active monomers, binds insulin receptor, and activates metabolic and mitogenic signaling pathways Insulin, INSR, IRS proteins, PI3K-AKT, MAPK Extracellular space; target-cell plasma membrane and cytosol Ayan 2023; Dalle 2024 (ayan2023abriefatlas pages 2-3, sakaguchi2024theroleof pages 1-3)

Table: This table summarizes the core functional annotation of human INS/insulin from biosynthesis through secretion and downstream signaling. It integrates recent mechanistic and review evidence across subcellular compartments, highlighting the molecules and enzymes most relevant to precise functional interpretation.

Step Key molecules Cellular location Main functional outputs Key evidence (source, year)
Ligand binding and receptor activation Insulin, insulin receptor (INSR) α2β2 heterotetramer, receptor Tyr1158/Tyr1162/Tyr1163 autophosphorylation sites Plasma membrane Initiates insulin signaling by activating the receptor’s intrinsic tyrosine kinase and creating docking sites for adaptor proteins Sakaguchi 2024; Szablewski 2024; Caturano 2024 (sakaguchi2024theroleof pages 1-3, szablewski2024changesincells pages 2-4, caturano2024insulin–heartaxisbridging pages 2-3)
Adaptor recruitment IRS1/IRS2, Shc, PTB/PH domains, NPEpY972 receptor motif Inner leaflet of plasma membrane / receptor-proximal cytosol Couples activated INSR to downstream metabolic and mitogenic pathways Sakaguchi 2024; Szablewski 2024 (sakaguchi2024theroleof pages 1-3, szablewski2024changesincells pages 2-4)
PI3K activation and PIP3 generation IRS proteins, PI3K p85/p110, PIP2, PIP3 Plasma membrane / cytosolic membrane interface Establishes the main metabolic signaling branch and recruits PDK1/AKT machinery Sakaguchi 2024; Szablewski 2024; Caturano 2024 (sakaguchi2024theroleof pages 1-3, szablewski2024changesincells pages 4-6, caturano2024insulin–heartaxisbridging pages 2-3)
AKT activation PIP3, PDK1, AKT/PKB, mTORC2 Plasma membrane then cytosol Central integration node for glucose uptake, glycogen synthesis, lipogenesis, protein synthesis, and survival signaling Sakaguchi 2024; Caturano 2024 (sakaguchi2024theroleof pages 1-3, caturano2024insulin–heartaxisbridging pages 2-3)
Glucose transporter trafficking AKT, GLUT4 vesicles, atypical PKC Cytosol to plasma membrane in muscle/adipose cells Increases cellular glucose uptake by translocating GLUT4 to the cell surface Szablewski 2024; Caturano 2024; Sakaguchi 2024 (szablewski2024changesincells pages 4-6, caturano2024insulin–heartaxisbridging pages 5-7, sakaguchi2024theroleof pages 1-3)
Glycogen synthesis control AKT, GSK3, glycogen synthase Cytosol Promotes glycogen synthesis by inhibiting GSK3 and relieving inhibition of glycogen synthase Szablewski 2024; Caturano 2024; Sakaguchi 2024 (szablewski2024changesincells pages 4-6, caturano2024insulin–heartaxisbridging pages 2-3, sakaguchi2024theroleof pages 1-3)
Protein synthesis and anabolic signaling AKT, TSC2, PRAS40, Rheb, mTORC1, 4E-BP1, p70S6K Cytosol / lysosomal-mTOR signaling compartments Stimulates protein synthesis, cell growth, and anabolic metabolism Caturano 2024; Sakaguchi 2024; Szablewski 2024 (caturano2024insulin–heartaxisbridging pages 2-3, sakaguchi2024theroleof pages 1-3, szablewski2024changesincells pages 4-6)
Transcriptional regulation of fasting/feeding programs AKT, FOXO transcription factors, SREBPs Cytosol and nucleus Suppresses FOXO-driven gluconeogenic gene expression and promotes lipogenic/anabolic gene programs during feeding Sakaguchi 2024; Szablewski 2024 (sakaguchi2024theroleof pages 1-3, szablewski2024changesincells pages 4-6)
MAPK mitogenic branch Shc, Grb2, SOS, Ras, Raf, MEK, ERK/MAPK Plasma membrane to cytosol to nucleus Drives growth, proliferation, differentiation, and gene-expression responses distinct from the core metabolic branch Sakaguchi 2024; Szablewski 2024; Caturano 2024 (sakaguchi2024theroleof pages 1-3, szablewski2024changesincells pages 4-6, caturano2024insulin–heartaxisbridging pages 5-7)
Tissue-level physiological outputs INSR-B (metabolic isoform), PI3K-AKT branch, MAPK branch, eNOS/NO in heart Whole-body target tissues including liver, muscle, adipose tissue, and heart Coordinates glucose disposal, reduced hepatic gluconeogenesis, glycogen and lipid storage, protein anabolism, and in cardiomyocytes supports substrate utilization and survival signaling Szablewski 2024; Caturano 2024 (szablewski2024changesincells pages 4-6, caturano2024insulin–heartaxisbridging pages 2-3)
Negative feedback / insulin resistance nodes Serine-phosphorylated IRS, reduced INSR content/activity, mTORC1-GRB10 feedback Plasma membrane and cytosol Weakens IRS–PI3K coupling, blunts GLUT4 translocation and glycogen synthesis, and contributes to insulin resistance Caturano 2024; Szablewski 2024 (caturano2024insulin–heartaxisbridging pages 5-7, szablewski2024changesincells pages 6-7)

Table: This table summarizes the major steps of insulin receptor signaling downstream of INS-encoded insulin, linking key molecules and cellular locations to metabolic and mitogenic outputs. It is useful for functional annotation because it connects secreted insulin to its principal target-cell mechanisms and physiological effects.

Conclusions (functional annotation synthesis)

Human INS (P01308) encodes a secreted peptide hormone precursor whose primary function is to produce mature insulin (A/B chains) that is stored in dense-core secretory granules and released in a glucose- and Ca2+-regulated manner from β-cells to maintain systemic metabolic homeostasis. Its biosynthesis is tightly coupled to ER folding capacity, redox state, ER Ca2+ homeostasis, and secretory trafficking; recent 2023–2024 work clarifies how metabolism-driven redox buffering, chronic hyperglycemia-induced translational programs, and cargo condensation mechanisms can regulate or impair insulin production and secretion. (ayan2023abriefatlas pages 2-3, szablewski2024changesincells pages 2-4, rohli2024ametabolicredox pages 1-2, evansmolina2024theailingβcell pages 4-5, cheruiyot2024sustainedhyperglycemiaspecifically pages 1-2, toledo2023condensationofthe pages 1-2)

URLs and publication dates for key 2023–2024 sources cited

  • Ayan & Demirci. Current Diabetes Reviews (2023-06). https://doi.org/10.2174/1573399819666220610150342 (ayan2023abriefatlas pages 2-3)
  • Aamodt & Powers. J Clin Invest (2023-04). https://doi.org/10.1172/jci169718 (aamodt2023peelingtheonion pages 1-2)
  • Toledo et al. Protein Science (2023-05). https://doi.org/10.1002/pro.4649 (toledo2023condensationofthe pages 1-2)
  • Lee et al. J Endocrine Society (2023-03). https://doi.org/10.1210/jendso/bvad056 (lee2023tirzepatideasmonotherapy pages 5-6)
  • Szablewski. Int J Mol Sci (2024-02). https://doi.org/10.3390/ijms25042397 (szablewski2024changesincells pages 2-4)
  • Dalle & Abderrahmani. Cells (2024-07). https://doi.org/10.3390/cells13151244 (dalle2024receptorsandsignaling pages 2-4)
  • Sakaguchi. Endocrine Journal (2024-07). https://doi.org/10.1507/endocrj.ej24-0205 (sakaguchi2024theroleof pages 1-3)
  • Caturano et al. Int J Mol Sci (2024-07). https://doi.org/10.3390/ijms25158369 (caturano2024insulin–heartaxisbridging pages 2-3)
  • Evans-Molina. Diabetes (2024-03). https://doi.org/10.2337/dbi23-0030 (evansmolina2024theailingβcell pages 4-5)
  • Rohli et al. JCI Insight (2024-06). https://doi.org/10.1172/jci.insight.178725 (rohli2024ametabolicredox pages 1-2)
  • Cheruiyot et al. J Clin Invest (2024-11). https://doi.org/10.1172/jci173280 (cheruiyot2024sustainedhyperglycemiaspecifically pages 1-2)
  • Boughton & Hovorka. Diabetologia (2024-05). https://doi.org/10.1007/s00125-024-06165-w (boughton2024theroleof pages 1-2)
  • Kadiyala et al. Expert Rev Med Devices (2024-10). https://doi.org/10.1080/17434440.2024.2406901 (kadiyala2024closedloopsystemsrecent pages 1-2)
  • ADA Standards: Diabetes Technology. Diabetes Care (2024-12). https://doi.org/10.2337/dc24-s007 (elsayed20247.diabetestechnology pages 1-1)
  • ADA Standards: Pharmacologic Approaches. Diabetes Care (2024-12). https://doi.org/10.2337/dc24-s009 (elsayed20249.pharmacologicapproaches pages 1-2)
  • ISPAD Guidelines: Insulin Delivery. Hormone Research in Paediatrics (2024-12). https://doi.org/10.1159/000543034 (biester2024ispadclinicalpractice pages 2-3)

References

  1. (urbaniak2025molecularpuzzleof pages 3-6): Edyta Urbaniak, Sara Henry, Maciej Lalowski, and Malgorzata Borowiak. Molecular puzzle of insulin: structural assembly pathways and their role in diabetes. Frontiers in Cell and Developmental Biology, Feb 2025. URL: https://doi.org/10.3389/fcell.2025.1502469, doi:10.3389/fcell.2025.1502469. This article has 4 citations.

  2. (urbaniak2025molecularpuzzleof pages 2-3): Edyta Urbaniak, Sara Henry, Maciej Lalowski, and Malgorzata Borowiak. Molecular puzzle of insulin: structural assembly pathways and their role in diabetes. Frontiers in Cell and Developmental Biology, Feb 2025. URL: https://doi.org/10.3389/fcell.2025.1502469, doi:10.3389/fcell.2025.1502469. This article has 4 citations.

  3. (ayan2023abriefatlas pages 2-3): Esra Ayan and H. Demirci. A brief atlas of insulin. Current diabetes reviews, Jun 2023. URL: https://doi.org/10.2174/1573399819666220610150342, doi:10.2174/1573399819666220610150342. This article has 18 citations.

  4. (szablewski2024changesincells pages 2-4): Leszek Szablewski. Changes in cells associated with insulin resistance. International Journal of Molecular Sciences, 25:2397, Feb 2024. URL: https://doi.org/10.3390/ijms25042397, doi:10.3390/ijms25042397. This article has 76 citations.

  5. (urbaniak2025molecularpuzzleof pages 7-8): Edyta Urbaniak, Sara Henry, Maciej Lalowski, and Malgorzata Borowiak. Molecular puzzle of insulin: structural assembly pathways and their role in diabetes. Frontiers in Cell and Developmental Biology, Feb 2025. URL: https://doi.org/10.3389/fcell.2025.1502469, doi:10.3389/fcell.2025.1502469. This article has 4 citations.

  6. (prefontaine2024investigatingtherelationship pages 8-13): C Préfontaine. Investigating the relationship between insulin processing and senescence in β-cells. Unknown journal, 2024.

  7. (rohli2024ametabolicredox pages 1-2): Kristen E. Rohli, Nicole J. Stubbe, Emily M. Walker, Gemma L. Pearson, Scott A. Soleimanpour, and Samuel B. Stephens. A metabolic redox relay supports er proinsulin export in pancreatic islet β cells. JCI Insight, Jun 2024. URL: https://doi.org/10.1172/jci.insight.178725, doi:10.1172/jci.insight.178725. This article has 14 citations and is from a domain leading peer-reviewed journal.

  8. (sakaguchi2024theroleof pages 1-3): Masaji Sakaguchi. The role of insulin signaling with foxo and foxk transcription factors. Endocrine Journal, 71:939-944, Jul 2024. URL: https://doi.org/10.1507/endocrj.ej24-0205, doi:10.1507/endocrj.ej24-0205. This article has 12 citations and is from a peer-reviewed journal.

  9. (dalle2024receptorsandsignaling pages 2-4): Stéphane Dalle and Amar Abderrahmani. Receptors and signaling pathways controlling beta-cell function and survival as targets for anti-diabetic therapeutic strategies. Cells, 13:1244, Jul 2024. URL: https://doi.org/10.3390/cells13151244, doi:10.3390/cells13151244. This article has 18 citations.

  10. (aamodt2023peelingtheonion pages 1-2): Kristie I. Aamodt and Alvin C. Powers. Peeling the onion: another layer in the regulation of insulin secretion. The Journal of clinical investigation, Apr 2023. URL: https://doi.org/10.1172/jci169718, doi:10.1172/jci169718. This article has 3 citations.

  11. (szablewski2024changesincells pages 4-6): Leszek Szablewski. Changes in cells associated with insulin resistance. International Journal of Molecular Sciences, 25:2397, Feb 2024. URL: https://doi.org/10.3390/ijms25042397, doi:10.3390/ijms25042397. This article has 76 citations.

  12. (caturano2024insulin–heartaxisbridging pages 2-3): Alfredo Caturano, Raffaele Galiero, Erica Vetrano, Celestino Sardu, Luca Rinaldi, Vincenzo Russo, Marcellino Monda, Raffaele Marfella, and Ferdinando Carlo Sasso. Insulin–heart axis: bridging physiology to insulin resistance. International Journal of Molecular Sciences, 25:8369, Jul 2024. URL: https://doi.org/10.3390/ijms25158369, doi:10.3390/ijms25158369. This article has 46 citations.

  13. (evansmolina2024theailingβcell pages 4-5): Carmella Evans-Molina. The ailing β-cell in diabetes: insights from a trip to the er: the 2023 outstanding scientific achievement award lecture. Diabetes, 73 4:545-553, Mar 2024. URL: https://doi.org/10.2337/dbi23-0030, doi:10.2337/dbi23-0030. This article has 8 citations and is from a highest quality peer-reviewed journal.

  14. (evansmolina2024theailingβcell pages 1-2): Carmella Evans-Molina. The ailing β-cell in diabetes: insights from a trip to the er: the 2023 outstanding scientific achievement award lecture. Diabetes, 73 4:545-553, Mar 2024. URL: https://doi.org/10.2337/dbi23-0030, doi:10.2337/dbi23-0030. This article has 8 citations and is from a highest quality peer-reviewed journal.

  15. (cheruiyot2024sustainedhyperglycemiaspecifically pages 1-2): Abigael Cheruiyot, Jennifer Hollister-Lock, Brooke Sullivan, Hui Pan, Jonathan M. Dreyfuss, Susan Bonner-Weir, and Jean E. Schaffer. Sustained hyperglycemia specifically targets translation of mrnas for insulin secretion. The Journal of Clinical Investigation, Nov 2024. URL: https://doi.org/10.1172/jci173280, doi:10.1172/jci173280. This article has 18 citations.

  16. (toledo2023condensationofthe pages 1-2): Pamela L. Toledo, Diego S. Vazquez, Alejo R. Gianotti, Milagros B. Abate, Carolin Wegbrod, Juha M. Torkko, Michele Solimena, and Mario R. Ermácora. Condensation of the β‐cell secretory granule luminal cargoes pro/insulin and ica512 resp18 homology domain. Protein Science, May 2023. URL: https://doi.org/10.1002/pro.4649, doi:10.1002/pro.4649. This article has 9 citations and is from a peer-reviewed journal.

  17. (elsayed20249.pharmacologicapproaches pages 1-2): Nuha A. ElSayed, G. Aleppo, Raveendhara R. Bannuru, Dennis Bruemmer, B. Collins, Laya Ekhlaspour, Jason L. Gaglia, Marisa E. Hilliard, Eric L. Johnson, K. Khunti, Ildiko Lingvay, Glenn Matfin, Rozalina G. McCoy, M. L. Perry, Scott J. Pilla, Sarit Polsky, P. Prahalad, R. Pratley, Alissa R. Segal, J. Seley, Robert C. Stanton, and Robert A. Gabbay. 9. pharmacologic approaches to glycemic treatment: standards of care in diabetes-2024. Diabetes care, 47 Suppl 1:S158-S178, Dec 2024. URL: https://doi.org/10.2337/dc24-s009, doi:10.2337/dc24-s009. This article has 541 citations and is from a highest quality peer-reviewed journal.

  18. (elsayed20247.diabetestechnology pages 1-2): Nuha A. ElSayed, G. Aleppo, Raveendhara R. Bannuru, Dennis Bruemmer, B. Collins, Laya Ekhlaspour, Marisa E. Hilliard, Eric L. Johnson, K. Khunti, Ildiko Lingvay, Glenn Matfin, Rozalina G. McCoy, M. L. Perry, Scott J. Pilla, Sarit Polsky, P. Prahalad, R. Pratley, Alissa R. Segal, J. Seley, Robert C. Stanton, and Robert A. Gabbay. 7. diabetes technology: standards of care in diabetes-2024. Diabetes care, 47 Suppl 1:S126-S144, Dec 2024. URL: https://doi.org/10.2337/dc24-s007, doi:10.2337/dc24-s007. This article has 203 citations and is from a highest quality peer-reviewed journal.

  19. (elsayed20247.diabetestechnology pages 1-1): Nuha A. ElSayed, G. Aleppo, Raveendhara R. Bannuru, Dennis Bruemmer, B. Collins, Laya Ekhlaspour, Marisa E. Hilliard, Eric L. Johnson, K. Khunti, Ildiko Lingvay, Glenn Matfin, Rozalina G. McCoy, M. L. Perry, Scott J. Pilla, Sarit Polsky, P. Prahalad, R. Pratley, Alissa R. Segal, J. Seley, Robert C. Stanton, and Robert A. Gabbay. 7. diabetes technology: standards of care in diabetes-2024. Diabetes care, 47 Suppl 1:S126-S144, Dec 2024. URL: https://doi.org/10.2337/dc24-s007, doi:10.2337/dc24-s007. This article has 203 citations and is from a highest quality peer-reviewed journal.

  20. (boughton2024theroleof pages 1-2): Charlotte K. Boughton and Roman Hovorka. The role of automated insulin delivery technology in diabetes. Diabetologia, 67:2034-2044, May 2024. URL: https://doi.org/10.1007/s00125-024-06165-w, doi:10.1007/s00125-024-06165-w. This article has 54 citations and is from a highest quality peer-reviewed journal.

  21. (kadiyala2024closedloopsystemsrecent pages 1-2): Nithya Kadiyala, Roman Hovorka, and Charlotte K. Boughton. Closed-loop systems: recent advancements and lived experiences. Expert Review of Medical Devices, 21:927-941, Oct 2024. URL: https://doi.org/10.1080/17434440.2024.2406901, doi:10.1080/17434440.2024.2406901. This article has 22 citations and is from a peer-reviewed journal.

  22. (biester2024ispadclinicalpractice pages 2-3): Torben Biester, Cari Berget, Charlotte Boughton, Laura Cudizio, Laya Ekhlaspour, Marisa E. Hilliard, Leenatha Reddy, Suzanne Sap Ngo Um, Melissa Schoelwer, Jennifer L. Sherr, and Klemen Dovc. Ispad clinical practice consensus guidelines 2024: diabetes technologies: insulin delivery. Hormone research in paediatrics, 97:1-34, Dec 2024. URL: https://doi.org/10.1159/000543034, doi:10.1159/000543034. This article has 24 citations and is from a peer-reviewed journal.

  23. (odabassian2024pilotoutpatientassessment pages 22-26): M Odabassian. Pilot outpatient assessment of a fully closed-loop dual-hormone (insulin and pramlintide) artificial pancreas system. Unknown journal, 2024.

  24. (lee2023tirzepatideasmonotherapy pages 5-6): Clare J Lee, Huzhang Mao, Vivian T Thieu, Laura Fernández Landó, and Melissa K Thomas. Tirzepatide as monotherapy improved markers of beta-cell function and insulin sensitivity in type 2 diabetes (surpass-1). Journal of the Endocrine Society, Mar 2023. URL: https://doi.org/10.1210/jendso/bvad056, doi:10.1210/jendso/bvad056. This article has 43 citations and is from a peer-reviewed journal.

  25. (lee2023tirzepatideasmonotherapy pages 3-4): Clare J Lee, Huzhang Mao, Vivian T Thieu, Laura Fernández Landó, and Melissa K Thomas. Tirzepatide as monotherapy improved markers of beta-cell function and insulin sensitivity in type 2 diabetes (surpass-1). Journal of the Endocrine Society, Mar 2023. URL: https://doi.org/10.1210/jendso/bvad056, doi:10.1210/jendso/bvad056. This article has 43 citations and is from a peer-reviewed journal.

  26. (boughton2024theroleof media 294504cd): Charlotte K. Boughton and Roman Hovorka. The role of automated insulin delivery technology in diabetes. Diabetologia, 67:2034-2044, May 2024. URL: https://doi.org/10.1007/s00125-024-06165-w, doi:10.1007/s00125-024-06165-w. This article has 54 citations and is from a highest quality peer-reviewed journal.

  27. (caturano2024insulin–heartaxisbridging pages 5-7): Alfredo Caturano, Raffaele Galiero, Erica Vetrano, Celestino Sardu, Luca Rinaldi, Vincenzo Russo, Marcellino Monda, Raffaele Marfella, and Ferdinando Carlo Sasso. Insulin–heart axis: bridging physiology to insulin resistance. International Journal of Molecular Sciences, 25:8369, Jul 2024. URL: https://doi.org/10.3390/ijms25158369, doi:10.3390/ijms25158369. This article has 46 citations.

  28. (szablewski2024changesincells pages 6-7): Leszek Szablewski. Changes in cells associated with insulin resistance. International Journal of Molecular Sciences, 25:2397, Feb 2024. URL: https://doi.org/10.3390/ijms25042397, doi:10.3390/ijms25042397. This article has 76 citations.

Artifacts

Citations

  1. rohli2024ametabolicredox pages 1-2
  2. cheruiyot2024sustainedhyperglycemiaspecifically pages 1-2
  3. toledo2023condensationofthe pages 1-2
  4. kadiyala2024closedloopsystemsrecent pages 1-2
  5. boughton2024theroleof pages 1-2
  6. biester2024ispadclinicalpractice pages 2-3
  7. odabassian2024pilotoutpatientassessment pages 22-26
  8. ayan2023abriefatlas pages 2-3
  9. aamodt2023peelingtheonion pages 1-2
  10. lee2023tirzepatideasmonotherapy pages 5-6
  11. szablewski2024changesincells pages 2-4
  12. dalle2024receptorsandsignaling pages 2-4
  13. sakaguchi2024theroleof pages 1-3
  14. urbaniak2025molecularpuzzleof pages 3-6
  15. urbaniak2025molecularpuzzleof pages 2-3
  16. urbaniak2025molecularpuzzleof pages 7-8
  17. prefontaine2024investigatingtherelationship pages 8-13
  18. szablewski2024changesincells pages 4-6
  19. lee2023tirzepatideasmonotherapy pages 3-4
  20. szablewski2024changesincells pages 6-7
  21. https://doi.org/10.1172/jci.insight.178725
  22. https://doi.org/10.2337/dbi23-0030
  23. https://doi.org/10.1172/jci173280
  24. https://doi.org/10.1002/pro.4649
  25. https://doi.org/10.2337/dc24-s009
  26. https://doi.org/10.2337/dc24-s007
  27. https://doi.org/10.1159/000543034
  28. https://doi.org/10.1007/s00125-024-06165-w
  29. https://doi.org/10.1210/jendso/bvad056
  30. https://doi.org/10.2174/1573399819666220610150342
  31. https://doi.org/10.1172/jci169718
  32. https://doi.org/10.3390/ijms25042397
  33. https://doi.org/10.3390/cells13151244
  34. https://doi.org/10.1507/endocrj.ej24-0205
  35. https://doi.org/10.3390/ijms25158369
  36. https://doi.org/10.1080/17434440.2024.2406901
  37. https://doi.org/10.3389/fcell.2025.1502469,
  38. https://doi.org/10.2174/1573399819666220610150342,
  39. https://doi.org/10.3390/ijms25042397,
  40. https://doi.org/10.1172/jci.insight.178725,
  41. https://doi.org/10.1507/endocrj.ej24-0205,
  42. https://doi.org/10.3390/cells13151244,
  43. https://doi.org/10.1172/jci169718,
  44. https://doi.org/10.3390/ijms25158369,
  45. https://doi.org/10.2337/dbi23-0030,
  46. https://doi.org/10.1172/jci173280,
  47. https://doi.org/10.1002/pro.4649,
  48. https://doi.org/10.2337/dc24-s009,
  49. https://doi.org/10.2337/dc24-s007,
  50. https://doi.org/10.1007/s00125-024-06165-w,
  51. https://doi.org/10.1080/17434440.2024.2406901,
  52. https://doi.org/10.1159/000543034,
  53. https://doi.org/10.1210/jendso/bvad056,

Perplexity

(INS-deep-research-perplexity.md)
Comprehensive Analysis of the Human Insulin Gene (INS) and Its Protein Product: Structure, Synthesis, Signaling, and Metabolic Functions Perplexity sonar-deep-research 54 citations 2025-11-15T15:59:15.781020

Comprehensive Analysis of the Human Insulin Gene (INS) and Its Protein Product: Structure, Synthesis, Signaling, and Metabolic Functions

This comprehensive report synthesizes current knowledge regarding the human insulin gene (INS, UniProt: P01308) and its encoded protein product, one of the most thoroughly characterized and clinically significant hormones in human physiology. Insulin functions as a 51-amino acid peptide hormone composed of two polypeptide chains linked by disulfide bonds, with the primary physiological role of regulating blood glucose homeostasis through complex signaling cascades that influence glucose uptake, glycogen synthesis, lipogenesis, and protein synthesis across multiple tissues[1][2][3]. The hormone is synthesized as a single-chain precursor molecule in pancreatic beta cells and undergoes sophisticated post-translational processing involving multiple proteolytic cleavage events to generate the mature, active form. Beyond its canonical role in glucose metabolism, insulin activates pleiotropic signaling pathways that regulate cell growth, proliferation, and differentiation through distinct intracellular cascades. Recent structural and mechanistic studies have revealed that insulin receptor activation proceeds through a stepwise conformational transition mechanism involving initial ligand binding followed by complex autophosphorylation events, providing molecular insights into both normal physiology and pathological states such as diabetes mellitus. This report provides an integrated analysis of insulin gene organization, protein biosynthesis, three-dimensional structure, receptor interactions, downstream signaling mechanisms, tissue-specific metabolic effects, and the molecular basis of insulin resistance and monogenic forms of diabetes resulting from INS gene mutations.

Protein Structure and Molecular Architecture of Insulin

Primary and Secondary Structure Organization

The mature human insulin protein is composed of 51 amino acid residues organized into two distinct polypeptide chains designated the A-chain and B-chain, which are covalently linked through disulfide bonds rather than a peptide backbone[9][12]. The A-chain consists of 21 amino acid residues, while the B-chain contains 30 residues, with molecular mass of approximately 5808 Daltons[9]. Three disulfide bonds maintain the structural integrity of the mature protein: two interchain disulfide bonds connect the A and B chains at positions A7-B7 and A20-B19, while a third intrachain disulfide bond exists within the A-chain between cysteine residues at positions A6 and A11[9][12]. These disulfide bonds are evolutionarily conserved across the insulin/insulin-like growth factor superfamily and represent a defining structural feature essential for biological activity and stability[2][12].

The three-dimensional structure of insulin reveals a compact, globular configuration with distinct secondary structural elements distributed between the two chains[9]. The A-chain exhibits two α-helical regions spanning residues A1-A8 and A12-A19, which are oriented in an antiparallel arrangement[9]. In contrast, the B-chain contains a central α-helix covering residues B9-B19, flanked on both sides by the interchain disulfide bonds, while two β-sheet structures exist at positions B7-B10 and B20-B23[9]. This architecture creates a highly ordered protein structure stabilized by multiple hydrogen bonding networks and the disulfide bond framework, enabling insulin to form higher-order oligomeric assemblies through protein-protein interactions. The specific amino acid composition and spatial organization of the A and B chains create two major binding epitopes that interact with the insulin receptor in a cooperative manner[16][26].

Zinc Coordination and Oligomeric Assembly

An important but frequently overlooked aspect of insulin structure involves the coordination of divalent zinc ions, which play critical roles in both storage and bioactivity of the hormone. Insulin possesses a histidine residue at position B10 that coordinates zinc ions, enabling the formation of zinc-stabilized hexamers through a toroidal geometry in which two zinc ions coordinate the B10 histidine residues of three insulin dimers[32][35][45]. These zinc-insulin hexamers represent the predominant storage form of insulin within pancreatic beta cell secretory granules, where they exist as water-insoluble crystals that can contain up to 100 millimolar concentrations of insulin[31]. The hexameric assembly is further stabilized by additional interactions involving other histidine residues and glutamic acid residues distributed across multiple insulin molecules within the complex[32][45].

Recent single-molecule studies have revealed that insulin oligomerization occurs through multiple competing assembly pathways depending on the solution concentration and presence of chemical additives[45]. At nanomolar concentrations mimicking physiological secretion, insulin assembly primarily proceeds through monomeric addition to growing oligomeric species, although dimeric and tetrameric addition pathways also exist[45]. At higher concentrations resembling pharmaceutical insulin formulations, the assembly pathway shifts toward dimer-mediated hexamer formation due to increased dimer-to-monomer ratio[45]. The composition of the oligomeric species at any given concentration can be predicted from kinetic rate constants and has important implications for insulin absorption kinetics: monomeric insulin is absorbed rapidly within 5-10 minutes of subcutaneous injection, dimers are absorbed over 20-30 minutes, while hexamers require 1-2 hours for absorption and must first dissociate into monomers to become physiologically active[48].

Evolutionary Conservation and Species Variation

The amino acid sequence of insulin has been highly conserved throughout vertebrate evolution, reflecting strong selective pressure to maintain biological function[2]. Human insulin differs from porcine insulin only at position B30, where human insulin possesses threonine while porcine insulin contains alanine[44]. This minimal difference explains why porcine insulin was historically used to treat insulin-dependent diabetic patients before recombinant human insulin could be produced in large quantities through recombinant DNA technologies[9]. The conservation of the disulfide bond pattern across all vertebrate insulin homologs demonstrates the evolutionary importance of the cysteine residues and their specific geometric arrangement[2]. Some species, such as guinea pig and hagfish, possess insulin molecules lacking histidine at position B10 and therefore do not form zinc-stabilized hexameric crystals; nevertheless, these species maintain normal glucose homeostasis, indicating that while zinc coordination and crystallization enhance insulin storage efficiency, they are not absolutely required for basal insulin function[35].

Biosynthesis and Post-Translational Processing of Insulin

Initial Synthesis and Translocation into the Endoplasmic Reticulum

Insulin synthesis within pancreatic beta cells is initiated from a precursor molecule designated preproinsulin, a single polypeptide chain of 110 amino acids that is the immediate product of translation from insulin mRNA[7][9]. The synthesis begins in the cytosol but is rapidly redirected to the rough endoplasmic reticulum (RER) through recognition of an N-terminal signal peptide comprising 24 hydrophobic residues that constitute the signal sequence[7][44]. This signal peptide directs the nascent preproinsulin chain to the ER membrane through interaction with the signal recognition particle, enabling co-translational translocation into the lumen of the RER[7]. The translocation process is surprisingly inefficient, with recent studies demonstrating that approximately 5-15% of newly synthesized preproinsulin molecules fail to translocate across the ER membrane during the initial 10-minute synthesis period, relying instead on post-translational translocation mechanisms[7]. The signal peptide is cleaved by a signal peptidase located on the lumenal surface of the RER membrane, yielding proinsulin as the immediate product of signal sequence removal[7][12][44].

The efficiency of preproinsulin translocation is influenced by expression levels of the translocon-associated protein (TRAP) complex, whose components are upregulated in response to glucose stimulation in pancreatic beta cell lines[7]. A genetic polymorphism in the TRAPα gene has been associated with both type 2 diabetes and gestational diabetes, suggesting that variations in translocation efficiency may contribute to altered insulin secretion capacity in these disease states[7]. The translocation process must be completed efficiently to prevent accumulation of misfolded preproinsulin in the cytosol, where it would trigger cellular stress responses and potentially undergo degradation through the proteasome pathway[7].

Proinsulin Folding and Disulfide Bond Formation

Following translocation into the ER lumen, preproinsulin undergoes signal peptide cleavage to generate proinsulin, the 86-amino acid single-chain precursor of insulin[12][44]. Proinsulin then embarks upon a complex folding pathway that involves formation of the three disulfide bonds that define the mature insulin structure[2][7]. The ER environment is specifically optimized to facilitate this disulfide bond formation through multiple specialized mechanisms, including high local concentrations of oxidoreductase enzymes such as protein disulfide isomerases and the overall oxidative atmosphere of the ER compartment[7]. The process of proinsulin folding is tightly coupled to disulfide bond pairing, and studies using nuclear magnetic resonance spectroscopy have revealed that the folding pathway proceeds through specific disulfide bonding intermediates rather than forming all three bonds simultaneously[2][7].

Significant evolutionary pressures have shaped the primary sequence of proinsulin to optimize its "foldability," the intrinsic propensity of the protein to fold correctly to the native conformation[7]. These evolutionary pressures are distinct from those governing the ultimate biological activity of the mature insulin molecule, reflecting the different functional requirements of the precursor versus the mature hormone[7]. A pancreatic beta cell is capable of synthesizing approximately 6000 preproinsulin molecules per second, representing an enormous translational load[7]. Even in the basal state without external stimulation, pancreatic beta cells experience significant endoplasmic reticulum stress as measured by markers such as spliced XBP1 protein, suggesting that the high biosynthetic rate of proinsulin pushes the ER protein folding machinery to near maximal capacity[7]. Following feeding, insulin biosynthesis increases further, and in metabolic states characterized by insulin resistance such as pregnancy or obesity, beta cells upregulate proinsulin synthesis even more dramatically to compensate for the reduced peripheral insulin sensitivity[7].

The vast storage pool of older insulin and C-peptide in mature secretory granules is considerably larger than the daily production of newly synthesized insulin, yet evidence indicates a "relative preference" for the release of newly synthesized insulin, particularly during the extended second-phase insulin secretion response[7]. This finding underscores the physiological importance of maintaining adequate proinsulin biosynthesis capacity and the precise regulation of biosynthetic pathway dynamics, as beta cell homeostasis critically depends upon both the biosynthetic pathway that generates new insulin and the granule turnover processes that maintain the releasable insulin pool[7].

Proteolytic Processing and Generation of Mature Insulin

The conversion of proinsulin to mature insulin occurs through the sequential action of specialized endoproteases and an exopeptidase that cleave the connecting C-domain peptide from between the A and B chains[10][12][44]. The C-domain, which links the B-chain to the A-chain in the proinsulin molecule, consists of approximately 30-35 amino acid residues flanked at each end by dibasic residue pairs (Arg-Arg and Lys-Arg)[12][44]. Two prohormone convertases designated PC1/3 (prohormone convertase 1/3) and PC2 (prohormone convertase 2) mediate the primary endoproteolytic cleavage events, with the relative contribution of each enzyme to proinsulin processing having been the subject of considerable investigation[10][12].

Historically, the prevailing model proposed that PC1/3 first cleaves proinsulin at the B-chain-C-peptide junction, generating an intermediate des-64,65 proinsulin product, which is then preferentially cleaved by PC2 at the C-peptide-A-chain junction to yield mature insulin[10][12]. However, recent evidence from human pancreatic islets has challenged this model. Immunofluorescence studies using validated antibodies revealed that PC2 protein is essentially undetectable in human beta cells, with PC2 mRNA signal localized almost exclusively to alpha cells and glucagon-producing cells rather than insulin-producing beta cells[10]. In contrast, PC1/3 is robustly expressed within human beta cells. Biochemical pulse-chase experiments in human islets demonstrated that despite pharmacological and molecular inhibition of PC2 function through multiple approaches including temperature blockade, brefeldin A, chloroquine, and specific protease inhibitors, human beta cells retained full capacity to process proinsulin to mature insulin[10]. Conversely, selective suppression of PC1/3 activity completely blocked proinsulin processing in human beta cells[10].

These findings establish that human proinsulin processing is mediated primarily or exclusively by PC1/3 without requiring PC2, representing a significant revision to the long-standing model based on rodent studies[10]. This species difference has important implications for understanding both normal insulin biosynthesis and disease mechanisms, as mutations affecting PC1/3 but not PC2 would be expected to impair insulin processing in humans, yet potential PC2 mutations might have little impact on insulin production. The PC1/3-mediated cleavage occurs within specialized secretory granules where pH is maintained at 5.0-5.5 by an intrinsic proton pump, creating conditions optimal for both prohormone processing and zinc-insulin crystal formation[12][57].

Following the endoproteolytic cleavage by PC1/3, the dibasic residues remaining at the junctions are removed by a carboxypeptidase B-like exopeptidase activity, generating the final mature insulin A and B chains with the correct terminal amino acid sequences[12][44]. The excised C-peptide, which lacks the dibasic residues, remains in the secretory granule along with insulin but is released into the circulation as an equimolar product of insulin secretion, serving as a useful clinical marker of endogenous insulin secretion[12]. The efficiency of proinsulin conversion to insulin within granules varies with physiological state and metabolic demand, and dysregulation of proinsulin processing has been implicated in the pathogenesis of both type 1 and type 2 diabetes mellitus[10].

Insulin Receptor Structure and Ligand Binding Mechanisms

Insulin Receptor Molecular Architecture

The insulin receptor (IR) is a transmembrane receptor tyrosine kinase that exists as a covalent homodimer composed of two α-subunits and two β-subunits linked by disulfide bonds, forming an (αβ)₂ quaternary structure[3][26]. The α-subunits are entirely extracellular and contain the ligand-binding domains, while the β-subunits are transmembrane proteins composed of an extracellular domain, a single transmembrane helix, and extensive intracellular domains harboring the catalytic tyrosine kinase activity[3][13][16]. The extracellular region of the α-subunit contains multiple functional domains including two leucine-rich globular domains designated L1 (residues 1-120) and L2 (residues 211-428) separated by a cysteine-rich region[13][26]. Additionally, the α-subunit contains two fibronectin type III (FnIII) domains and an α-helical C-terminal domain (αCT) that undergo critical conformational changes during receptor activation[16][26].

Alternative splicing of exon 11 in the insulin receptor gene creates two receptor isoforms, designated IR-A and IR-B, which differ by 12 amino acids in the αCT domain length[16][43]. These isoforms display different biological properties, with IR-B being the predominant form in most metabolic tissues such as liver, muscle, and adipose tissue, while IR-A is more abundant in certain tissues including the brain and is expressed at higher levels during fetal development[26]. The insulin receptor kinase domain shares approximately 84% sequence homology with the insulin-like growth factor-1 receptor (IGF-1R) kinase domain, while the overall sequence homology between IR and IGF-1R ranges from 41-84% depending on the specific domain analyzed[13][26].

Insulin-Binding Sites and Receptor Activation Mechanism

Biochemical and structural studies have established that insulin binds to the insulin receptor through two distinct binding sites designated site-1 and site-2, which have markedly different binding affinities[16][26][46]. Site-1, the primary insulin-binding site, is composed of the L1 domain of one α-subunit and the αCT domain of the adjacent α-subunit; insulin binds to this site with high affinity (Kd approximately 10-30 nanomolar)[16]. Site-2 is a secondary binding site that is composed primarily of the FnIII-1 domain and has much weaker affinity (Kd approximately 400 nanomolar)[16]. Insulin binding to site-2 occurs only at excessive insulin concentrations above 100 nanomolar, which exceeds physiological conditions where circulating insulin levels typically range from low picomolar to nanomolar concentrations[16].

Structural studies have revealed that the insulin receptor exists in distinct conformational states that change dramatically upon insulin binding[16][46]. In the unliganded state, the insulin receptor adopts a "Λ-shaped" auto-inhibited conformation in which the two receptor α-subunits are held in close proximity through extensive inter-protomer interactions that keep the receptor in a signaling-incompetent state[46]. Upon binding of a single insulin molecule to site-1, the receptor undergoes a dramatic conformational transition to a "Γ-shaped" intermediate state, where the FnIII-2 domains move away from the L1 domain, initiating separation of the two receptor protomers[16][46]. This conformational change brings the two intracellular kinase domains into closer spatial proximity, enabling trans-autophosphorylation whereby one kinase domain phosphorylates tyrosine residues on the other kinase domain[43][46].

When multiple insulin molecules bind, the receptor transitions to a fully activated "T-shaped" conformation with both kinase domains held in optimal alignment for maximal kinase activity[16][46]. The structural transitions between the Λ, Γ, and T conformations are mediated by mechanical rearrangement of the α-helical C-terminal (αCT) domains, which are linked by a disulfide bond at position C683[16]. The upshift of one αCT domain from a four-turn α-helix in the apo state to a seven-turn helix in the active state forces the opposite αCT domain downward due to their disulfide linkage, resulting in a coordinated conformational change that propagates from the extracellular binding domains to the transmembrane regions and ultimately to the intracellular kinase domains[16][46].

Insulin Signaling Cascades and Intracellular Signal Transduction

Initial Receptor Autophosphorylation Events

The binding of insulin to its extracellular receptor leads to rapid and sequential autophosphorylation of multiple tyrosine residues distributed across different domains of the intracellular region[43]. The first step in insulin receptor activation involves trans-autophosphorylation of tyrosine residues in three distinct intracellular regions: the juxtamembrane (JM) domain, the kinase domain activation loop, and the C-terminal (CT) domain[43]. Specifically, three tyrosine residues in the kinase domain activation loop (Tyr1146, Tyr1150, and Tyr1151 using IR isoform A numbering) are phosphorylated in a sequential manner, with phosphorylation of Tyr1150 occurring first, followed by Tyr1148 and Tyr1151[43]. These phosphorylation events are critical because in the inactive receptor, the unphosphorylated activation loop is inserted into the catalytic site of the kinase domain, physically blocking substrate and ATP from accessing the active site[43]. Following insulin-binding-induced phosphorylation, the activated loop is released from the catalytic site, dramatically increasing kinase activity by permitting substrate and ATP to interact with the kinase[43][46].

Additional autophosphorylation events occur at Tyr953 and Tyr960 in the JM domain, and at Tyr1316 and Tyr1322 in the CT domain[43][46]. Among these sites, the phosphorylated Tyr960 (designated pY960) is of particular functional importance, as it functions as an NPXY motif that serves as a docking site for the phosphotyrosine-binding (PTB) domains of insulin receptor substrates (IRS) proteins and Src homology 2 domain-containing transforming protein (SHC)[43][46]. This phosphorylation creates a recruitment platform for downstream signaling effectors, allowing direct physical interaction between the phosphorylated insulin receptor and key adaptor proteins that initiate the downstream signaling cascades[43].

The Phosphatidylinositol 3-Kinase and AKT Signaling Pathway

The phosphatidylinositol 3-kinase (PI3K) pathway represents the primary route through which insulin exerts its metabolic effects, particularly regarding glucose homeostasis, glycogen synthesis, and protein synthesis[3][6][40]. The binding of phosphorylated IRS proteins (IRS-1 and IRS-2 being the predominant forms in most tissues) to the activated insulin receptor leads to phosphorylation of multiple tyrosine residues within the IRS proteins by the receptor kinase[3][6]. These phosphorylated IRS tyrosine residues then serve as docking sites for the regulatory subunit (p85) of PI3K, which contains SH2 domains that specifically recognize phosphotyrosine residues in the correct sequence context[3][6].

Recruitment of PI3K to the membrane leads to activation of the catalytic subunit (p110), which phosphorylates the lipid phosphatidylinositol 4,5-bisphosphate (PIP2) on the inner leaflet of the plasma membrane to generate phosphatidylinositol 3,4,5-trisphosphate (PIP3)[3][6]. The accumulation of PIP3 at the plasma membrane creates a docking site for proteins containing pleckstrin homology (PH) domains, including phosphoinositide-dependent protein kinase-1 (PDK1) and the serine/threonine kinase AKT (also known as protein kinase B or PKB)[3][6][40]. PDK1 phosphorylates and activates AKT at threonine 308 within the activation loop, while additional phosphorylation of AKT at serine 473 in the C-terminal hydrophobic motif by mTORC2 complex leads to maximal AKT activation[40].

Once activated, AKT phosphorylates numerous downstream substrates that collectively mediate the metabolic effects of insulin[40]. These substrates include glycogen synthase kinase-3 (GSK3), which is phosphorylated and inactivated, thereby allowing dephosphorylated and active glycogen synthase to catalyze glycogen synthesis[40]. AKT also phosphorylates and activates mTOR complex 1 (mTORC1), which stimulates protein synthesis through phosphorylation of ribosomal protein S6 kinase (S6K) and eIF4E-binding protein 1 (4E-BP1), relieving translational repression[40]. Additionally, AKT phosphorylates and inactivates forkhead box protein O1 (FoxO1), a transcription factor that normally activates genes involved in gluconeogenesis; phosphorylation of FoxO1 by AKT causes its cytoplasmic retention and proteasomal degradation, thereby suppressing hepatic glucose production[40][38].

The Mitogen-Activated Protein Kinase and ERK1/2 Signaling Pathway

In parallel with the PI3K/AKT pathway, insulin also activates the mitogen-activated protein kinase (MAPK) pathway primarily through interaction of the SHC adaptor protein with the phosphorylated insulin receptor[3][6]. SHC binding to the phosphorylated receptor leads to SHC phosphorylation by the receptor kinase, which then recruits the growth factor receptor-bound protein 2 (Grb2) adaptor protein in complex with the guanyl nucleotide exchange factor SOS[3][6]. This complex promotes GDP/GTP exchange on the small G protein Ras, leading to Ras activation and consequent activation of the Raf serine/threonine kinase[6]. Raf then phosphorylates and activates MEK1/2 (MAPK/ERK kinase), which phosphorylates and activates the extracellular signal-regulated kinases ERK1 and ERK2[6][40].

The MAPK pathway mediated by ERK1/2 has distinct biological effects compared to the PI3K/AKT pathway, with the MAPK pathway playing a more prominent role in the regulation of gene expression and cell proliferation rather than acute metabolic effects[3][6][40]. Phosphorylated ERK1/2 translocates to the nucleus and phosphorylates numerous transcription factors and chromatin regulators that alter the expression of genes involved in cell growth, differentiation, and proliferation[6]. The differential activation of the PI3K and MAPK pathways may depend on insulin concentration and the duration of receptor activation, with sustained insulin signaling producing more pronounced MAPK pathway activation[6].

Metabolic Functions of Insulin in Glucose Homeostasis

Stimulation of Glucose Uptake in Skeletal Muscle and Adipose Tissue

The most physiologically important function of insulin is the stimulation of glucose uptake from the bloodstream into insulin-responsive tissues, particularly skeletal muscle and adipose tissue, which together account for the majority of postprandial glucose disposal[5][8][22]. This metabolic action is mediated through the insulin-dependent translocation of glucose transporter type-4 (GLUT4) from intracellular membrane compartments to the plasma membrane, which is a critical control point for glucose homeostasis[8][19][22]. In the basal state without insulin stimulation, approximately 90% of GLUT4 resides in specialized intracellular vesicles and recycling endosomes, with only about 5% located at the plasma membrane[6][19][22]. Upon insulin stimulation, GLUT4-containing vesicles rapidly translocate to the plasma membrane, increasing cell surface GLUT4 by 2-3 fold and dramatically enhancing glucose transport capacity[6][19][22].

The GLUT4 translocation process is initiated by the PI3K/AKT signaling pathway downstream of insulin receptor activation[6][19][22]. Following AKT activation, the serine/threonine kinase AS160 (also known as TBC1D4) is phosphorylated by AKT, leading to its release from GLUT4-containing storage vesicles[22]. This phosphorylation event activates the RabGAP activity of AS160, converting Rab small GTPases to their inactive GDP-bound state and enabling GLUT4 vesicle mobilization[22]. Additionally, phosphorylation of TBC1D1 by AKT promotes GLUT4 trafficking through effects on the exocyst complex and actin cytoskeleton dynamics[22]. The coordinated action of these signaling molecules results in translocation of GLUT4 to the plasma membrane, t-tubules in muscle, and sarcolemmal membranes, where GLUT4 can mediate glucose transport[8][22].

The translocated GLUT4 facilitates glucose entry through ATP-independent facilitative diffusion with a Michaelis constant (Km) of approximately 5 millimolar, enabling steep gradients for rapid glucose clearance at physiological glucose concentrations[8][19][22]. Once inside the cell, glucose is phosphorylated by hexokinase to glucose-6-phosphate, which is then retained in the cell and utilized for glycolysis or stored as glycogen. In skeletal muscle, approximately 80% of postprandial glucose uptake is mediated through this GLUT4-dependent insulin-stimulated mechanism, underscoring the critical importance of this process for maintaining blood glucose homeostasis[8][22].

Hepatic Glucose Metabolism and Suppression of Hepatic Glucose Output

The liver plays a critical role in maintaining glucose homeostasis through its capacity to produce endogenous glucose via both glycogenolysis (breakdown of stored glycogen) and gluconeogenesis (synthesis of new glucose from precursors such as lactate, glycerol, and amino acids)[21][24]. Insulin potently suppresses hepatic glucose production through both direct actions on the liver and indirect actions mediated by effects on adipose tissue, muscle, and central nervous system signaling[21][24]. Direct hepatic insulin effects occur through insulin receptor activation in hepatocytes, leading to suppression of glycogenolysis and gluconeogenesis through multiple mechanisms[21][24].

Insulin rapidly inhibits hepatic glycogenolysis through mechanisms involving protein phosphatase-1 (PP1), which is activated through insulin-mediated suppression of glycogen phosphorylase kinase, thereby preventing phosphorylation of glycogen phosphorylase and allowing its inactivation[15][21]. Simultaneously, insulin activates glycogen synthase through PP1-mediated dephosphorylation, promoting the synthesis of new glycogen from glucose-6-phosphate[15][21]. These complementary effects result in a rapid net transition from glucose output to glucose storage in the liver in response to rising postprandial insulin levels[15][21].

The suppression of hepatic gluconeogenesis by insulin involves inhibition of the transcription factors CREB and FoxO1, which normally activate the expression of the rate-limiting gluconeogenic enzymes phosphoenolpyruvate carboxylase (PEPCK) and glucose-6-phosphatase[15][38][41]. The AKT-mediated phosphorylation and inactivation of FoxO1, combined with reduced CREB activity following insulin treatment, leads to decreased expression of gluconeogenic enzymes and reduced hepatic glucose production[15][38][41]. Additionally, an important indirect mechanism through which insulin suppresses hepatic glucose production involves inhibition of adipose tissue lipolysis, leading to decreased circulating free fatty acid and glycerol concentrations[14][21][24]. Since fatty acid oxidation in hepatocytes provides ATP and acetyl-CoA that drive gluconeogenesis, the reduction in hepatic fatty acid oxidation resulting from decreased NEFA availability represents a dominant mechanism by which systemic insulin indirectly suppresses hepatic glucose production[14][24].

Lipid and Protein Metabolism Regulated by Insulin

Stimulation of Fatty Acid and Triglyceride Synthesis

Insulin is a potent anabolic hormone that stimulates fatty acid synthesis and triglyceride storage in adipose tissue and liver through multiple transcriptional and post-translational mechanisms[15][18][50]. The key transcription factors mediating insulin-induced lipogenic gene expression are the sterol regulatory element binding proteins (SREBPs), particularly SREBP-1c in lipogenic tissues, along with upstream stimulatory factors (USF) and liver X receptors (LXRα)[18][50][53]. Insulin stimulates SREBP-1c expression through the mTOR pathway in a manner that does not require S6K1, indicating activation of mTOR substrates distinct from S6K1[18][50][53]. Upon insulin stimulation, SREBP-1c undergoes proteolytic activation in the Golgi apparatus, releasing the transcriptionally active N-terminal fragment that translocates to the nucleus and activates transcription of genes encoding enzymes required for fatty acid synthesis including fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC), stearoyl-CoA desaturase (SCD), and glycerol-3-phosphate acyltransferase[18][50][53].

The induced fatty acid synthesized in response to insulin is then esterified into triglycerides through sequential esterification reactions with glycerol-3-phosphate, generating triglyceride molecules that accumulate in the adipose tissue as energy storage or are exported from the liver as circulating VLDL particles[18][50]. This process is facilitated by insulin-induced suppression of the AMP-activated protein kinase (AMPK), which normally inhibits mTORC1 and acetyl-CoA carboxylase; suppression of AMPK by elevated glucose and insulin allows maximal activation of acetyl-CoA carboxylase and fatty acid synthesis[18][50].

Inhibition of Lipolysis and Regulation of Lipid Mobilization

Reciprocally, insulin potently inhibits lipolysis in adipose tissue through inactivation of hormone-sensitive lipase (HSL) via a PKA-independent mechanism[15]. Insulin-activated AKT phosphorylates and inactivates phosphodiesterase 3B (PDE3B), reducing the degradation of cAMP and preventing PKA activation[15]. Additionally, insulin signaling leads to dephosphorylation of HSL, which suppresses its catalytic activity and prevents the hydrolysis of stored triglycerides into free fatty acids and glycerol[15]. The net result is decreased adipose tissue lipolysis and reduced circulating free fatty acid levels, diminishing the substrate for hepatic ketone body synthesis and gluconeogenesis, while also allowing increased glucose uptake and lipid storage in adipose tissue in the fed state[15].

Effects on Protein Metabolism

Insulin is also a powerful regulator of protein turnover, stimulating protein synthesis while simultaneously inhibiting protein degradation, thereby promoting net protein anabolism[20][23]. Insulin stimulates protein synthesis through multiple mechanisms including increased cellular uptake of amino acids through upregulation of amino acid transporters, particularly for branched-chain amino acids (BCAAs) such as leucine[20]. Leucine is a particularly important signal for mTORC1 activation and protein synthesis initiation through its capacity to activate the Rag family of GTPases that recruit mTORC1 to the lysosomal membrane[20][23]. Following insulin stimulation and increased leucine availability, mTORC1 phosphorylates S6K1 and 4E-BP1, leading to translation initiation factor phosphorylation and enhanced translation of mRNA molecules, particularly those encoding protein synthesis machinery and growth-promoting proteins[20][23].

In contrast, insulin suppresses hepatic protein degradation through inhibition of the ATP-ubiquitin-dependent proteasome pathway and ATP-independent lysosomal proteases[15][20]. The mechanism involves AKT-mediated phosphorylation and inactivation of FoxO transcription factors, which normally activate genes encoding ubiquitin ligases and other proteolytic machinery[15][20]. In skeletal muscle, insulin stimulates protein synthesis and simultaneously inhibits protein degradation through effects on the same signaling pathways, promoting net muscle protein accumulation[20].

Tissue-Specific Insulin Actions and the Metabolic Effects Across Organ Systems

Central Nervous System Regulation of Energy Metabolism

Beyond its peripheral metabolic actions, insulin also acts within the central nervous system to regulate appetite, feeding behavior, and overall energy expenditure[39][42]. Insulin receptors are widely distributed throughout the hypothalamus and other brain regions involved in energy homeostasis regulation[42]. In the healthy metabolic state, insulin acts in an anorexigenic fashion, reducing appetite and food intake through mechanisms involving PI3K/AKT signaling in the hypothalamus and interconnected brain regions[39][42]. Chronic overfeeding with high-caloric diets rich in sugar and saturated fat leads to development of brain insulin resistance characterized by blunted responsiveness of feeding-related brain regions to insulin signaling despite persistent peripheral insulin resistance[39].

Recent studies have demonstrated that even short-term consumption of high-caloric diet (8 weeks of supplemental high-caloric foods in addition to regular diet) produces prolonged alterations in brain insulin responsiveness in the absence of significant changes in body weight or peripheral insulin sensitivity[39]. These alterations are particularly evident in the reward-processing brain regions including the midbrain and insular cortex, where augmented insulin responsiveness correlates with increased liver fat content[39]. Notably, the diminished insulin responsiveness in the hippocampus and fusiform gyrus outlasts the duration of high-caloric diet consumption, suggesting that diet-induced changes in brain insulin responsiveness may represent a precursor to the development of systemic insulin resistance[39].

Hepatic Lipid Accumulation and Multiorgan Insulin Resistance

The accumulation of intrahepatic triglycerides (IHTG) represents a central feature linking insulin resistance across multiple tissues[14]. In nondiabetic obese subjects, IHTG content is the best independent predictor of insulin action across liver, skeletal muscle, and adipose tissue, accounting for 34-44% of the variance in tissue-specific insulin sensitivity independent of body mass index and total percent body fat[14]. The association between elevated IHTG content and impaired hepatic insulin sensitivity, as reflected in reduced suppression of endogenous glucose production, involves multiple mechanisms including competition of lipid-derived signals (such as diacylglycerol and ceramides) with glucose-derived signals for IRS-1 binding capacity at the insulin receptor[14].

This metabolic crosstalk between hepatic lipid content and systemic insulin sensitivity illustrates the integrated nature of metabolic regulation, whereby defects in one tissue's insulin signaling capacity propagate to impair insulin action in other tissues through effects on circulating nutrient and lipid signals[14]. In this context, nonalcoholic fatty liver disease should be conceptualized not as an isolated hepatic pathology but rather as a manifestation of multiorgan insulin resistance affecting liver, muscle, and adipose tissue simultaneously[14].

Genetic Variants and Monogenic Forms of Diabetes Associated with INS Gene Mutations

Structural Consequences of Proinsulin Mutations

Dominant mutations in the insulin gene (INS) cause monogenic syndromes of diabetes mellitus, most prominently including permanent neonatal-onset diabetes (PNDM) due to toxic misfolding of proinsulin variants[12][27][30]. Seven distinct heterozygous mutations in the INS gene have been identified as causes of permanent neonatal diabetes, with the mutations resulting in defects in insulin protein folding and secretion that lead to endoplasmic reticulum stress and apoptosis of pancreatic beta cells[30]. When these mutant proinsulins are expressed in cell culture systems, they demonstrate impaired folding and secretion compared to wild-type proinsulin, and expression of the mutant forms is associated with increased Grp78 protein expression and XBP1 mRNA splicing, both markers of endoplasmic reticulum stress response[30].

The molecular mechanism by which proinsulin mutations cause diabetes involves generation of misfolded protein intermediates that accumulate in the ER lumen, triggering the unfolded protein response (UPR) and ultimately leading to beta cell apoptosis[30]. The critical disulfide bonds that stabilize insulin structure are often disrupted by amino acid substitutions that affect cysteine residues, and studies in the Akita and Munich mouse models that harbor cysteine mutations in the insulin gene have demonstrated that alterations in proinsulin disulfide bonding patterns severely impair insulin production and lead to diabetes[7][30].

Genetic Imprinting Effects on Neonatal Diabetes Severity

An unusual feature of monogenic INS mutations is that the disease phenotype is affected by whether the mutated allele is inherited from the mother or father, reflecting epigenetic phenomena known as genomic imprinting[27]. The INS gene locus undergoes parent-of-origin-specific methylation, resulting in selective silencing of either the maternal or paternal allele depending on its origin[27]. In the case of maternally inherited INS mutations, the normal paternal INS allele is expressed, whereas in paternally inherited mutations, the maternal INS allele is silenced, resulting in functional haploinsufficiency where only the single mutated paternal allele is expressed[27]. This results in considerably more severe phenotypes for paternally inherited mutations: children inheriting mutated INS alleles from their fathers develop neonatal diabetes at a median age of 2.5 months, while affected parents typically did not manifest diabetes until 84 months of age, demonstrating markedly earlier disease onset in children[27].

In contrast, the difference in age at diagnosis between children and parents was not statistically significant for maternally transmitted mutations, as the imprinting pattern ensures that the normal maternal allele is silenced regardless of whether the child inherits the mutation[27]. These imprinting-related differences in disease severity highlight the importance of allele dosage effects in the pathogenesis of monogenic diabetes, with the complete absence of functional insulin production (as occurs with paternal transmission) producing more severe neonatal diabetes than the situation in which a normal allele is functional[27].

Conclusion: Integration of Insulin Biology into a Comprehensive Framework

The insulin gene (INS) and its protein product represent one of the most thoroughly characterized and physiologically critical components of human metabolism. Insulin functions as a multifaceted signaling hormone that coordinates the anabolic and catabolic processes of the body in response to nutrient availability, serving as the primary signal of the fed state and governing energy storage, utilization, and expenditure[2][5][15]. The sophisticated mechanisms governing insulin biosynthesis, from preproinsulin synthesis and translocation through complex proteolytic processing generating mature insulin, have been refined through evolution to ensure reliable production of the massive quantities of insulin required for metabolic homeostasis[7][2].

The insulin receptor and its associated signaling cascade represent a model system for understanding receptor tyrosine kinase activation and signal transduction, with recent structural studies revealing the dynamic conformational transitions that convert the inactive receptor to a fully activated signaling-competent state[16][43][46]. The divergent downstream signaling pathways—particularly the PI3K/AKT and MAPK/ERK cascades—enable insulin to coordinately regulate acute metabolic processes such as glucose uptake and glycogen synthesis while simultaneously controlling long-term gene expression and cellular proliferation[3][6][40]. The tissue-specific effects of insulin reflect the differential expression of signaling proteins, receptor isoforms, and downstream effectors in distinct tissue compartments, enabling coordinate regulation of glucose utilization in muscle, hepatic glucose production and lipogenesis in liver, and lipid storage and NEFA release in adipose tissue[15][22][24].

Dysregulation of insulin secretion, insulin receptor signaling, or the post-receptor signaling cascades leads to the spectrum of metabolic diseases collectively termed diabetes mellitus, encompassing both type 1 diabetes resulting from loss of insulin-producing beta cells and type 2 diabetes characterized by insulin resistance and eventual beta cell failure[2][5][6]. Monogenic forms of diabetes resulting from INS gene mutations demonstrate the critical importance of insulin structure and production for maintaining beta cell viability and insulin secretion capacity[27][30]. Understanding the precise molecular mechanisms governing insulin synthesis, secretion, receptor binding, and intracellular signaling has opened new therapeutic avenues for diabetes treatment, including development of insulin receptor sensitizers, GLP-1 receptor agonists that enhance endogenous insulin secretion, and novel formulations of recombinant insulin with improved pharmacokinetics[5][48].

The complexity and elegance of insulin's mechanisms of action—from the intricate biosynthetic pathway that generates the hormone in pancreatic beta cells, through the stepwise conformational transitions of its receptor, to the multiple interconnected signaling cascades that coordinate metabolic responses across tissues—exemplify the sophistication of human physiology and provide a framework for understanding both normal metabolic homeostasis and the molecular basis of metabolic disease. Continued investigation of insulin biology at the molecular, cellular, and systems levels remains essential for developing improved therapeutic strategies for diabetes and obesity, which represent major global health challenges affecting over 450 million individuals worldwide[31].

Citations

  1. https://www.uniprot.org/uniprotkb/P01308/entry
  2. https://pubmed.ncbi.nlm.nih.gov/21204007/
  3. https://www.ncbi.nlm.nih.gov/books/NBK378978/
  4. https://www.ncbi.nlm.nih.gov/gene/3630
  5. https://www.cdc.gov/diabetes/about/insulin-resistance-type-2-diabetes.html
  6. https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2023.1226655/full
  7. https://pmc.ncbi.nlm.nih.gov/articles/PMC6463291/
  8. https://pmc.ncbi.nlm.nih.gov/articles/PMC2838661/
  9. https://en.wikipedia.org/wiki/Insulin
  10. https://diabetesjournals.org/diabetes/article/69/7/1451/39562/Revisiting-Proinsulin-Processing-Evidence-That
  11. https://febs.onlinelibrary.wiley.com/doi/full/10.1046/j.1432-1327.1999.00043.x
  12. https://www.ncbi.nlm.nih.gov/books/NBK279029/
  13. https://www.ncbi.nlm.nih.gov/books/NBK6192/
  14. https://pubmed.ncbi.nlm.nih.gov/18355813/
  15. https://www.ncbi.nlm.nih.gov/books/NBK525983/
  16. https://www.nature.com/articles/s12276-023-01101-1
  17. https://physoc.onlinelibrary.wiley.com/doi/10.14814/phy2.14607
  18. https://pmc.ncbi.nlm.nih.gov/articles/PMC3092640/
  19. https://pmc.ncbi.nlm.nih.gov/articles/PMC7672939/
  20. https://pmc.ncbi.nlm.nih.gov/articles/PMC10780923/
  21. https://diabetesjournals.org/diabetes/article/55/Supplement_2/S65/12042/The-Inhibitory-Effects-of-Insulin-on-Hepatic
  22. https://www.ncbi.nlm.nih.gov/books/NBK537322/
  23. https://diabetesjournals.org/diabetes/article/21/Supplement_2/447/8663/Effect-of-Insulin-on-Protein-Synthesis
  24. https://pmc.ncbi.nlm.nih.gov/articles/PMC5358484/
  25. https://diabetesjournals.org/diabetes/article/65/4/981/35131/Glucose-Induces-Mouse-Cell-Proliferation-via-IRS2
  26. https://diabetesjournals.org/care/article/34/1/e9/27610/Paternally-Inherited-Proinsulin-Mutations-May
  27. https://pmc.ncbi.nlm.nih.gov/articles/PMC1951771/
  28. https://www.nature.com/articles/ncomms14892
  29. https://pmc.ncbi.nlm.nih.gov/articles/PMC2350430/
  30. https://pmc.ncbi.nlm.nih.gov/articles/PMC5866358/
  31. https://pubs.acs.org/doi/10.1021/acs.cgd.1c01463
  32. https://pmc.ncbi.nlm.nih.gov/articles/PMC9450567/
  33. https://pmc.ncbi.nlm.nih.gov/articles/PMC5710702/
  34. https://pmc.ncbi.nlm.nih.gov/articles/PMC2736467/
  35. https://diabetesjournals.org/diabetes/article/73/3/412/153920/High-Doses-of-Exogenous-Glucagon-Stimulate-Insulin
  36. https://pmc.ncbi.nlm.nih.gov/articles/PMC7981362/
  37. https://pmc.ncbi.nlm.nih.gov/articles/PMC4133859/
  38. https://www.nature.com/articles/s42255-025-01226-9
  39. https://www.cellsignal.com/pathways/insulin-receptor-signaling-pathway
  40. https://pmc.ncbi.nlm.nih.gov/articles/PMC8233149/
  41. https://pubmed.ncbi.nlm.nih.gov/16933179/
  42. https://www.nature.com/articles/s42003-022-04386-6
  43. https://pmc.ncbi.nlm.nih.gov/articles/PMC10398885/
  44. https://pmc.ncbi.nlm.nih.gov/articles/PMC7716884/
  45. https://www.nature.com/articles/s41467-022-29722-6
  46. https://www.nature.com/articles/s41419-023-06154-8
  47. https://pmc.ncbi.nlm.nih.gov/articles/PMC9298385/
  48. https://pmc.ncbi.nlm.nih.gov/articles/PMC5923433/
  49. https://pmc.ncbi.nlm.nih.gov/articles/PMC5783513/
  50. https://www.nature.com/articles/s41467-023-41306-6
  51. https://pmc.ncbi.nlm.nih.gov/articles/PMC4020243/
  52. https://pmc.ncbi.nlm.nih.gov/articles/PMC2276387/
  53. https://www.nature.com/articles/s42255-023-00964-y
  54. https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0036989

📄 View Raw YAML

 
id: P01308
gene_symbol: INS
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: 'Insulin is a 51-amino acid peptide hormone composed of two polypeptide chains (A-chain and B-chain)

  linked by disulfide bonds. It is synthesized as preproinsulin in pancreatic beta cells, processed

  through the secretory pathway to generate mature insulin, and secreted into the extracellular space

  in response to elevated blood glucose. The primary core function of insulin is regulation of glucose

  homeostasis through binding to the insulin receptor, triggering intracellular signaling cascades

  (primarily PI3K/AKT and MAPK pathways) that stimulate glucose uptake in muscle and adipose tissue,

  suppress hepatic glucose production, promote glycogen synthesis, stimulate lipogenesis, and inhibit

  lipolysis and protein degradation. Beyond its metabolic roles, insulin has important functions in

  cell growth, proliferation, and neuroprotection.

  '
existing_annotations:
- term:
    id: GO:0005158
    label: insulin receptor binding
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: 'This annotation represents the core molecular function of insulin - specific binding to the

      insulin receptor. The deep research extensively documents insulin-receptor interactions,

      including the two-site binding model with site-1 (high affinity, Kd ~10-30 nM) formed by

      L1 domain and αCT domain, and site-2 (lower affinity). Structural studies have revealed

      the stepwise activation mechanism involving conformational transitions from Λ-shaped to

      Γ-shaped to T-shaped receptor states upon insulin binding.

      '
    action: ACCEPT
    reason: 'This is the primary and most specific molecular function term for insulin. The IBA evidence

      is well-supported by extensive structural and biochemical data showing insulin''s high-affinity

      and specific binding to the insulin receptor. This annotation accurately captures the core

      molecular activity of the protein.

      '
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Insulin binding to site-1, the primary insulin-binding site, is composed of the L1 domain of one α-subunit and the αCT domain of the adjacent α-subunit; insulin binds to this site with high affinity (Kd approximately 10-30 nanomolar)
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: The binding of insulin to its extracellular receptor leads to rapid and sequential autophosphorylation of multiple tyrosine residues distributed across different domains of the intracellular region
    - reference_id: file:human/INS/INS-deep-research-falcon.md
      supporting_text: 'Insulin acts mainly by binding **INSR**, which autophosphorylates and recruits adaptor proteins (IRS, Shc), bifurcating into'
- term:
    id: GO:0005179
    label: hormone activity
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: 'Insulin functions as a peptide hormone secreted by pancreatic beta cells that acts systemically

      to regulate metabolism. This annotation correctly captures insulin''s role as a signaling molecule

      that travels through the bloodstream to affect distant target tissues.

      '
    action: ACCEPT
    reason: 'This is an accurate but general annotation. While "insulin receptor binding" is more specific

      and informative, "hormone activity" is also correct and provides appropriate high-level

      classification of insulin''s molecular function. Both terms are valid and complementary.

      '
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Insulin functions as a 51-amino acid peptide hormone composed of two polypeptide chains linked by disulfide bonds, with the primary physiological role of regulating blood glucose homeostasis through complex signaling cascades
    - reference_id: PMID:38397072
      supporting_text: Insulin is a polypeptide hormone synthesized and secreted by pancreatic β-cells. It plays an important role as a metabolic hormone.
- term:
    id: GO:0005615
    label: extracellular space
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: 'Insulin is secreted from pancreatic beta cells and functions in the extracellular space,

      where it travels through the bloodstream to reach target tissues. This is the primary

      location where mature insulin carries out its function as a hormone.

      '
    action: ACCEPT
    reason: 'This is the correct and most specific cellular component annotation for the location where

      mature insulin functions. Insulin is a secreted hormone that acts in the extracellular space.

      The IBA annotation is well-supported and represents the core functional location.

      '
    supported_by:
    - reference_id: file:human/INS/INS-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Secreted.'
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Insulin is secreted from pancreatic beta cells into the extracellular space in response to elevated blood glucose
    - reference_id: file:human/INS/INS-deep-research-falcon.md
      supporting_text: '**Plasma membrane/extracellular:** Ca2+-triggered exocytosis releases insulin to circulation; insulin acts as a ligand for the insulin receptor in peripheral tissues.'
- term:
    id: GO:0050714
    label: positive regulation of protein secretion
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: 'This annotation likely refers to insulin''s effects on stimulating secretion of various proteins

      in target tissues, or possibly feedback effects on beta cell secretory processes.

      '
    action: KEEP_AS_NON_CORE
    reason: 'While insulin may have some effects on protein secretion in various tissues, this is not a

      primary or well-characterized core function of insulin. The primary functions are glucose

      homeostasis, metabolic regulation, and cell growth. This annotation represents a more

      peripheral effect and should be marked as non-core.

      '
- term:
    id: GO:0042593
    label: glucose homeostasis
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: 'This is THE core biological process for insulin. Insulin''s primary physiological role is

      maintaining blood glucose homeostasis through stimulation of glucose uptake, suppression of

      hepatic glucose production, and coordination of glucose storage as glycogen.

      '
    action: ACCEPT
    reason: 'This annotation captures the central and most important biological function of insulin.

      Extensive literature documents insulin''s critical role in glucose homeostasis, and this is

      the primary reason insulin exists as a hormone. This is a core annotation that must be retained.

      '
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: The most physiologically important function of insulin is the stimulation of glucose uptake from the bloodstream into insulin-responsive tissues, particularly skeletal muscle and adipose tissue
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Insulin potently suppresses hepatic glucose production through both direct actions on the liver and indirect actions mediated by effects on adipose tissue, muscle, and central nervous system signaling
    - reference_id: file:human/INS/INS-uniprot.txt
      supporting_text: Insulin decreases blood glucose concentration. It increases cell permeability to monosaccharides, amino acids and fatty acids.
    - reference_id: PMID:38397072
      supporting_text: Insulin influences the metabolism of glucose, regulating plasma glucose levels and stimulating glucose storage in organs such as the liver, muscles and adipose tissue.
    - reference_id: file:human/INS/INS-deep-research-falcon.md
      supporting_text: Human **INS (P01308)** encodes a secreted peptide hormone precursor whose primary function is to produce **mature insulin** (A/B chains) that is stored in dense-core secretory granules and released in a **glucose- and Ca2+-regulated** manner from β-cells to maintain systemic metabolic homeostasis.
- term:
    id: GO:0005179
    label: hormone activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: 'Duplicate of IBA annotation above. Electronic annotation based on InterPro domains and keywords.

      '
    action: ACCEPT
    reason: 'This is a duplicate annotation (same term as line 2) but with different evidence code (IEA vs IBA).

      Both are correct. Duplicates are acceptable as they come from different evidence pipelines.

      '
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: 'This is a more general parent term of "extracellular space" (GO:0005615). Both are correct

      but extracellular space is more specific.

      '
    action: ACCEPT
    reason: 'While "extracellular space" is more specific and preferred, this annotation is not wrong.

      It''s a valid broader term. Having both the specific and general terms is acceptable in GO

      annotation practice.

      '
- term:
    id: GO:0006006
    label: glucose metabolic process
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: 'Insulin regulates glucose metabolism broadly, including glucose uptake, glycolysis, glycogen

      synthesis, and suppression of gluconeogenesis. This is a valid but broad term.

      '
    action: ACCEPT
    reason: 'This is an accurate but general term. "Glucose homeostasis" is more specific to insulin''s

      regulatory role, but "glucose metabolic process" is also correct as insulin affects multiple

      aspects of glucose metabolism. Both terms provide useful information at different levels of

      specificity.

      '
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Once inside the cell, glucose is phosphorylated by hexokinase to glucose-6-phosphate, which is then retained in the cell and utilized for glycolysis or stored as glycogen
    - reference_id: file:human/INS/INS-uniprot.txt
      supporting_text: It accelerates glycolysis, the pentose phosphate cycle, and glycogen synthesis in liver.
- term:
    id: GO:1901701
    label: cellular response to oxygen-containing compound
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  review:
    summary: 'This is an extremely broad term that could apply to almost any cellular process. Insulin may

      technically be involved in responses to various oxygen-containing compounds, but this annotation

      is not informative about insulin''s specific function.

      '
    action: MARK_AS_OVER_ANNOTATED
    reason: 'This term is far too general and non-specific to be useful for insulin annotation. While

      technically insulin signaling may involve responses to oxygen-containing compounds, this

      annotation doesn''t capture any meaningful aspect of insulin''s specific biological role.

      This represents computational over-annotation from ARBA.

      '
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:17051221
  review:
    summary: 'This annotation is based on physical interaction with insulin-degrading enzyme (IDE). While

      technically correct, "protein binding" is uninformative. The more specific term "protease binding"

      is annotated separately for this interaction.

      '
    action: MODIFY
    reason: 'Generic "protein binding" annotations should be replaced with more specific binding terms when

      available. In this case, since insulin binds to IDE (a protease), the annotation "protease binding"

      (GO:0002020) already exists and is more informative. However, the primary binding partner is

      the insulin receptor, so "insulin receptor binding" is most important.

      '
    proposed_replacement_terms:
    - id: GO:0002020
      label: protease binding
    supported_by:
    - reference_id: PMID:17051221
      supporting_text: Structures of human insulin-degrading enzyme reveal a new substrate recognition mechanism.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:23302862
  review:
    summary: 'This annotation is based on interaction with insulin receptor (INSR). This is the most important

      molecular interaction for insulin, but "protein binding" is too general.

      '
    action: MODIFY
    reason: 'This interaction with insulin receptor should be annotated with the specific term "insulin

      receptor binding" (GO:0005158) which already exists in the annotation set, rather than the

      generic "protein binding" term.

      '
    proposed_replacement_terms:
    - id: GO:0005158
      label: insulin receptor binding
    supported_by:
    - reference_id: PMID:23302862
      supporting_text: How insulin engages its primary binding site on the insulin receptor.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:29512653
  review:
    summary: 'This is another annotation for insulin-insulin receptor interaction based on cryo-EM structure

      determination. Same issue as above - too generic.

      '
    action: MODIFY
    reason: 'Should use "insulin receptor binding" (GO:0005158) instead of generic "protein binding".

      '
    proposed_replacement_terms:
    - id: GO:0005158
      label: insulin receptor binding
    supported_by:
    - reference_id: PMID:29512653
      supporting_text: Structure of the insulin receptor-insulin complex by single-particle cryo-EM analysis.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:32296183
  review:
    summary: 'This is from a large-scale binary protein interactome study. Multiple different binding

      partners detected, but all use generic "protein binding" term.

      '
    action: ACCEPT
    reason: 'For high-throughput interactome studies where specific binding functions haven''t been

      characterized, "protein binding" is acceptable. These annotations document physical

      interactions even if more specific functional terms aren''t yet available.

      '
    supported_by:
    - reference_id: PMID:32296183
      supporting_text: Apr 8. A reference map of the human binary protein interactome.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:9388210
  review:
    summary: 'Interaction with insulin-like growth factor binding proteins (IGFBPs) that can inhibit

      insulin receptor activation.

      '
    action: ACCEPT
    reason: 'Without a more specific term for IGFBP binding available in GO, "protein binding" is acceptable

      for documenting this interaction. This interaction has functional significance for insulin

      receptor signaling.

      '
    supported_by:
    - reference_id: PMID:9388210
      supporting_text: Inhibition of insulin receptor activation by insulin-like growth factor binding proteins.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:9773776
  review:
    summary: 'Interaction with megalin, an endocytic receptor that can internalize insulin.

      '
    action: ACCEPT
    reason: 'This documents a specific interaction with megalin that is relevant for insulin clearance

      and degradation. Without a more specific GO term available, "protein binding" is acceptable.

      '
    supported_by:
    - reference_id: PMID:9773776
      supporting_text: Megalin is an endocytic receptor for insulin.
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:10508408
  review:
    summary: 'This and the following 7 annotations document insulin''s ability to form dimers and higher-order

      oligomers (hexamers). This is important for insulin storage in secretory granules as zinc-insulin

      hexamers.

      '
    action: ACCEPT
    reason: 'Insulin oligomerization is a well-established and functionally important property. Insulin

      forms dimers and zinc-stabilized hexamers that are the storage form in pancreatic beta cells.

      Multiple independent studies support this annotation.

      '
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Insulin possesses a histidine residue at position B10 that coordinates zinc ions, enabling the formation of zinc-stabilized hexamers through a toroidal geometry in which two zinc ions coordinate the B10 histidine residues of three insulin dimers
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: These zinc-insulin hexamers represent the predominant storage form of insulin within pancreatic beta cell secretory granules
    - reference_id: PMID:10508408
      supporting_text: Structural consequences of the B5 histidine --> tyrosine mutation in human insulin characterized by X-ray crystallography and conformational analysis.
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:17472440
  review:
    summary: 'Study on insulin amyloid fibril formation, another form of insulin self-association.

      '
    action: ACCEPT
    reason: 'While amyloid formation is pathological rather than physiological, it does represent

      insulin-insulin binding. The annotation is technically correct.

      '
    supported_by:
    - reference_id: PMID:17472440
      supporting_text: A helical structural nucleus is the primary elongating unit of insulin amyloid fibrils.
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:20738396
  review:
    summary: 'Structural study of proinsulin C-peptide oligomerization. Note this is about C-peptide,

      not mature insulin.

      '
    action: ACCEPT
    reason: 'C-peptide is part of the proinsulin precursor, and this annotation applies to the full-length

      preproinsulin/proinsulin forms that are present during biosynthesis.

      '
    supported_by:
    - reference_id: PMID:20738396
      supporting_text: 2010 Aug 3. Structural features of proinsulin C-peptide oligomeric and amyloid states.
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:22854022
  review:
    summary: 'Study on SERF protein as modifier of amyloid fiber assembly involving insulin.

      '
    action: ACCEPT
    reason: 'Documents insulin self-association in context of amyloid formation.

      '
    supported_by:
    - reference_id: PMID:22854022
      supporting_text: 2012 Jul 26. SERF protein is a direct modifier of amyloid fiber assembly.
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:23106816
  review:
    summary: 'Study on insulin solubility transitions involving interactions with C-peptide.

      '
    action: ACCEPT
    reason: 'Documents insulin oligomerization behavior.

      '
    supported_by:
    - reference_id: PMID:23106816
      supporting_text: Insulin solubility transitions by pH-dependent interactions with proinsulin C-peptide.
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:23416304
  review:
    summary: 'Study on amino acid determinants in insulin amyloid superstructures.

      '
    action: ACCEPT
    reason: 'Documents insulin self-assembly properties.

      '
    supported_by:
    - reference_id: PMID:23416304
      supporting_text: '2013 Feb 14. Amino acid sequence determinants in self-assembly of insulin chiral amyloid superstructures: role of C-terminus of B-chain in association of fibrils.'
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:23510797
  review:
    summary: 'Study on surface-induced insulin amyloidal aggregation.

      '
    action: ACCEPT
    reason: 'Documents insulin oligomerization.

      '
    supported_by:
    - reference_id: PMID:23510797
      supporting_text: 2013 Mar 16. Peptides that form β-sheets on hydrophobic surfaces accelerate surface-induced insulin amyloidal aggregation.
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:8844841
  review:
    summary: 'Structural study of insulin complexes related to T→R transition.

      '
    action: ACCEPT
    reason: 'Documents functional insulin oligomerization relevant to hexamer formation.

      '
    supported_by:
    - reference_id: PMID:8844841
      supporting_text: 'A novel complex of a phenolic derivative with insulin: structural features related to the T-->R transition.'
- term:
    id: GO:0008286
    label: insulin receptor signaling pathway
  evidence_type: IDA
  original_reference_id: PMID:8702995
  review:
    summary: 'This study demonstrated that insulin activates Akt (PKB) kinase primarily through phosphorylation,

      establishing insulin''s role in the PI3K/Akt signaling cascade.

      '
    action: ACCEPT
    reason: 'This is a core biological process annotation for insulin. Activation of the insulin receptor

      signaling pathway is the primary mechanism by which insulin exerts its effects on glucose

      homeostasis and metabolism. Well-supported by extensive literature.

      '
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: The binding of insulin to its extracellular receptor leads to rapid and sequential autophosphorylation of multiple tyrosine residues distributed across different domains of the intracellular region
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: The phosphatidylinositol 3-kinase (PI3K) pathway represents the primary route through which insulin exerts its metabolic effects
    - reference_id: PMID:8702995
      supporting_text: Akt, a pleckstrin homology domain containing kinase, is activated primarily by phosphorylation.
    - reference_id: file:human/INS/INS-deep-research-falcon.md
      supporting_text: '**PI3K→PIP3→AKT** (metabolic branch): GLUT4 translocation, glycogen synthesis regulation via GSK3, mTOR-mediated protein synthesis, and transcriptional programs (e.g., FOXO regulation).'
- term:
    id: GO:0048018
    label: receptor ligand activity
  evidence_type: IDA
  original_reference_id: PMID:8702995
  review:
    summary: 'This is a general term indicating that insulin functions as a ligand for its receptor. This is

      accurate but less specific than "insulin receptor binding".

      '
    action: ACCEPT
    reason: 'This is a valid molecular function term that correctly describes insulin as a receptor ligand.

      While "insulin receptor binding" is more specific, both terms are appropriate and provide

      complementary information.

      '
    supported_by:
    - reference_id: PMID:8702995
      supporting_text: Akt, a pleckstrin homology domain containing kinase, is activated primarily by phosphorylation.
- term:
    id: GO:0051897
    label: positive regulation of phosphatidylinositol 3-kinase/protein kinase B signal transduction
  evidence_type: IDA
  original_reference_id: PMID:8702995
  review:
    summary: 'This annotation captures one of the two major signaling cascades activated by insulin - the

      PI3K/Akt pathway, which mediates most metabolic effects including glucose uptake, glycogen

      synthesis, and protein synthesis.

      '
    action: ACCEPT
    reason: 'This is a core signaling pathway for insulin and represents one of the most important mechanisms

      by which insulin regulates glucose homeostasis. Well-documented in the literature.

      '
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: The phosphatidylinositol 3-kinase (PI3K) pathway represents the primary route through which insulin exerts its metabolic effects, particularly regarding glucose homeostasis, glycogen synthesis, and protein synthesis
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Once activated, AKT phosphorylates numerous downstream substrates that collectively mediate the metabolic effects of insulin
    - reference_id: PMID:8702995
      supporting_text: Akt, a pleckstrin homology domain containing kinase, is activated primarily by phosphorylation.
    - reference_id: file:human/INS/INS-deep-research-falcon.md
      supporting_text: '**PI3K→PIP3→AKT** (metabolic branch): GLUT4 translocation, glycogen synthesis regulation via GSK3, mTOR-mediated protein synthesis, and transcriptional programs (e.g., FOXO regulation).'
- term:
    id: GO:0005179
    label: hormone activity
  evidence_type: NAS
  original_reference_id: PMID:14986111
  review:
    summary: 'Another instance of the hormone activity annotation, this time with NAS evidence code.

      '
    action: ACCEPT
    reason: 'Duplicate of earlier annotations but with different evidence. This is acceptable.

      '
    supported_by:
    - reference_id: PMID:14986111
      supporting_text: Impaired binding of insulin to erythrocyte membrane receptor and the activation of nitric oxide synthase by the hormone in human breast cancer.
- term:
    id: GO:0005615
    label: extracellular space
  evidence_type: IDA
  original_reference_id: PMID:9667398
  review:
    summary: 'Direct experimental evidence for insulin localization in extracellular space.

      '
    action: ACCEPT
    reason: 'This provides experimental (IDA) evidence for the cellular component annotation, complementing

      the IBA annotation.

      '
    supported_by:
    - reference_id: PMID:9667398
      supporting_text: 'Familial hyperproinsulinaemia due to a mutation substituting histidine for arginine at position 65 in proinsulin: identification of the mutation by restriction enzyme mapping.'
- term:
    id: GO:0008286
    label: insulin receptor signaling pathway
  evidence_type: IDA
  original_reference_id: PMID:15792832
  review:
    summary: 'Study on insulin and nitric oxide stimulation of glucose transport in human placenta.

      '
    action: ACCEPT
    reason: 'Multiple independent experimental confirmations of insulin''s role in the insulin receptor

      signaling pathway are valuable and support the core annotation.

      '
    supported_by:
    - reference_id: PMID:15792832
      supporting_text: 2005 Jan 27. Insulin and nitric oxide stimulates glucose transport in human placenta.
- term:
    id: GO:0008286
    label: insulin receptor signaling pathway
  evidence_type: IGI
  original_reference_id: PMID:19727662
  review:
    summary: |
      The GOA reference for this annotation is PMID:19727662, which is in
      fact a NAMPT/visfatin paper on vascular smooth muscle cells, not an
      insulin paper (verified during PR #764 round-2 review). The
      annotation itself (insulin → insulin receptor signaling pathway) is
      correct in principle but the cited evidence does not actually
      support it; cannot validate without a correct PMID.
    action: UNDECIDED
    reason: |
      Original GOA reference (PMID:19727662) is misattributed — it is a
      NAMPT paper, not an insulin paper. Action retained as UNDECIDED
      until GOA supplies (or curator identifies) a correctly-attributed
      reference for IGI evidence of INS in insulin receptor signaling.
      Note: the broader insulin receptor signaling pathway annotation
      remains amply supported elsewhere in this review by other valid
      references.
    supported_by:
    - reference_id: PMID:19727662
      supporting_text: 2009 Aug 29. Extracellular PBEF/NAMPT/visfatin activates pro-inflammatory signalling in human vascular smooth muscle cells through nicotinamide phosphoribosyltransferase activity.
- term:
    id: GO:0043123
    label: positive regulation of canonical NF-kappaB signal transduction
  evidence_type: IDA
  original_reference_id: PMID:19727662
  review:
    summary: |
      The GOA reference for this annotation is PMID:19727662, which is
      in fact a NAMPT/visfatin paper, not an insulin paper (verified
      during PR #764 round-2 review). Cannot validate the IDA evidence
      for INS → NF-kappaB signaling on the cited reference alone.
    action: UNDECIDED
    reason: |
      Original GOA reference (PMID:19727662) is misattributed — it is a
      NAMPT paper studying vascular smooth muscle cells, not an insulin
      paper. While insulin may activate NF-kappaB in some contexts,
      this specific annotation cannot be evaluated until a correct
      reference is supplied.
    supported_by:
    - reference_id: PMID:19727662
      supporting_text: 2009 Aug 29. Extracellular PBEF/NAMPT/visfatin activates pro-inflammatory signalling in human vascular smooth muscle cells through nicotinamide phosphoribosyltransferase activity.
- term:
    id: GO:0005179
    label: hormone activity
  evidence_type: IMP
  original_reference_id: PMID:381941
  review:
    summary: 'Classic study on structurally abnormal insulin causing diabetes, demonstrating hormone function.

      '
    action: ACCEPT
    reason: 'Another instance with experimental evidence (IMP) for hormone activity.

      '
    supported_by:
    - reference_id: PMID:381941
      supporting_text: A structurally abnormal insulin causing human diabetes.
- term:
    id: GO:0008286
    label: insulin receptor signaling pathway
  evidence_type: IDA
  original_reference_id: PMID:20455999
  review:
    summary: 'Study on caveolin-2 regulation of insulin-specific ERK activation.

      '
    action: ACCEPT
    reason: 'Additional experimental support for insulin receptor signaling pathway.

      '
    supported_by:
    - reference_id: PMID:20455999
      supporting_text: 'A novel domain of caveolin-2 that controls nuclear targeting: regulation of insulin-specific ERK activation and nuclear translocation by caveolin-2.'
- term:
    id: GO:0008286
    label: insulin receptor signaling pathway
  evidence_type: IMP
  original_reference_id: PMID:14615391
  review:
    summary: 'Study showing insulin stimulates glucose transport via NO/cGMP pathway.

      '
    action: ACCEPT
    reason: 'Experimental evidence for insulin receptor signaling, though this highlights the NO/cGMP branch.

      '
    supported_by:
    - reference_id: PMID:14615391
      supporting_text: Insulin stimulates glucose transport via nitric oxide/cyclic GMP pathway in human vascular smooth muscle cells.
- term:
    id: GO:0000139
    label: Golgi membrane
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-6809006
  review:
    summary: 'Proinsulin passes through the Golgi apparatus during its trafficking from ER to secretory granules.

      '
    action: ACCEPT
    reason: 'This is an accurate annotation for the biosynthetic trafficking of proinsulin through the

      secretory pathway. While not the final functional location, this represents an important

      intermediate location during insulin biogenesis in beta cells.

      '
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-falcon.md
      supporting_text: '**Golgi/TGN:** trafficking and packaging into immature secretory granules.'
- term:
    id: GO:0000139
    label: Golgi membrane
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-6809010
  review:
    summary: 'Duplicate Golgi membrane annotation from different Reactome reaction.

      '
    action: ACCEPT
    reason: 'Multiple Reactome reactions document proinsulin trafficking through Golgi.

      '
- term:
    id: GO:0000139
    label: Golgi membrane
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-6809011
  review:
    summary: 'Another Golgi membrane annotation from Reactome.

      '
    action: ACCEPT
    reason: 'Additional Reactome support for Golgi localization.

      '
- term:
    id: GO:0005788
    label: endoplasmic reticulum lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-264997
  review:
    summary: 'Proinsulin enters the ER lumen after translocation and undergoes disulfide bond formation there.

      '
    action: ACCEPT
    reason: 'This is an accurate annotation for an early stage of insulin biosynthesis. Preproinsulin is

      translocated into the ER lumen where it is processed to proinsulin and undergoes critical

      folding and disulfide bond formation.

      '
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Following translocation into the ER lumen, preproinsulin undergoes signal peptide cleavage to generate proinsulin, the 86-amino acid single-chain precursor of insulin
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: The ER environment is specifically optimized to facilitate this disulfide bond formation through multiple specialized mechanisms
    - reference_id: PMID:40052150
      supporting_text: Proinsulin foldability is optimized in the ER, an environment evolved to support the folding process and the formation of disulfide bonds while minimizing misfolding.
    - reference_id: PMID:38935435
      supporting_text: Hyperoxidation of the ER delays proinsulin export and limits the proinsulin supply available for insulin granule formation.
- term:
    id: GO:0005788
    label: endoplasmic reticulum lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-265010
  review:
    summary: 'Another ER lumen annotation from Reactome pathway.

      '
    action: ACCEPT
    reason: 'Additional Reactome support for ER localization.

      '
- term:
    id: GO:0005796
    label: Golgi lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-264976
  review:
    summary: 'Proinsulin travels through the Golgi lumen and binds zinc and calcium there.

      '
    action: ACCEPT
    reason: 'Accurate annotation for proinsulin trafficking. The Golgi lumen is where proinsulin binds

      zinc and calcium ions, which are important for subsequent crystal formation in secretory granules.

      '
- term:
    id: GO:0005796
    label: Golgi lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-265010
  review:
    summary: 'Duplicate Golgi lumen annotation.

      '
    action: ACCEPT
    reason: 'Multiple Reactome reactions support Golgi lumen localization.

      '
- term:
    id: GO:0005796
    label: Golgi lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-265153
  review:
    summary: 'Another Golgi lumen annotation.

      '
    action: ACCEPT
    reason: 'Additional Reactome support.

      '
- term:
    id: GO:0030133
    label: transport vesicle
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-6807877
  review:
    summary: 'Proinsulin travels in transport vesicles from ER to Golgi and from Golgi to secretory granules.

      '
    action: ACCEPT
    reason: 'Accurate annotation for the vesicular transport stages of insulin biosynthesis.

      '
- term:
    id: GO:0030133
    label: transport vesicle
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-6809003
  review:
    summary: 'Duplicate transport vesicle annotation.

      '
    action: ACCEPT
    reason: 'Multiple Reactome reactions document vesicular transport.

      '
- term:
    id: GO:0030133
    label: transport vesicle
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-6809006
  review:
    summary: 'Another transport vesicle annotation.

      '
    action: ACCEPT
    reason: 'Additional Reactome support.

      '
- term:
    id: GO:0033116
    label: endoplasmic reticulum-Golgi intermediate compartment membrane
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-6807875
  review:
    summary: 'The ERGIC is an intermediate compartment between ER and Golgi that proinsulin passes through.

      '
    action: ACCEPT
    reason: 'This is an accurate annotation for the trafficking pathway. Proinsulin passes through the

      ERGIC compartment during its journey from ER to Golgi.

      '
- term:
    id: GO:0033116
    label: endoplasmic reticulum-Golgi intermediate compartment membrane
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-6807877
  review:
    summary: 'Duplicate ERGIC annotation.

      '
    action: ACCEPT
    reason: 'Multiple Reactome reactions support ERGIC localization.

      '
- term:
    id: GO:0034774
    label: secretory granule lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-265153
  review:
    summary: 'Proinsulin is packaged into secretory granules where it is processed to mature insulin and

      stored as zinc-insulin crystals.

      '
    action: ACCEPT
    reason: 'This is a critical location for insulin. Secretory granules are where proinsulin is processed

      by prohormone convertases to mature insulin, and where insulin is stored as zinc-stabilized

      hexamers before secretion. This is an essential annotation.

      '
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: The PC1/3-mediated cleavage occurs within specialized secretory granules where pH is maintained at 5.0-5.5 by an intrinsic proton pump, creating conditions optimal for both prohormone processing and zinc-insulin crystal formation
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: These zinc-insulin hexamers represent the predominant storage form of insulin within pancreatic beta cell secretory granules, where they exist as water-insoluble crystals
    - reference_id: PMID:37159024
      supporting_text: proinsulin is an early driver of insulin SG biogenesis, in a process in which its co-condensation with RESP18HD participates in their phase separation from other secretory proteins in transit through the same compartments but destined to other routes.
    - reference_id: file:human/INS/INS-deep-research-falcon.md
      supporting_text: '**Immature/maturing secretory granules:** proteolytic conversion of proinsulin → insulin + C-peptide; granule acidification/condensation and storage.'
- term:
    id: GO:0034774
    label: secretory granule lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-NUL-9023165
  review:
    summary: 'Annotation for proinsulin processing in secretory granules (rat PC1/3 cleaves human proinsulin).

      '
    action: ACCEPT
    reason: 'Documents location where proinsulin processing occurs.

      '
- term:
    id: GO:0034774
    label: secretory granule lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-NUL-9023166
  review:
    summary: 'Another secretory granule annotation for processing steps.

      '
    action: ACCEPT
    reason: 'Additional Reactome support for secretory granule localization.

      '
- term:
    id: GO:0034774
    label: secretory granule lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-NUL-9023180
  review:
    summary: 'Secretory granule annotation for PC2-mediated cleavage step.

      '
    action: ACCEPT
    reason: 'Documents processing location.

      '
- term:
    id: GO:0034774
    label: secretory granule lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-NUL-9023186
  review:
    summary: 'Secretory granule annotation for carboxypeptidase processing.

      '
    action: ACCEPT
    reason: 'Additional Reactome support.

      '
- term:
    id: GO:0010976
    label: positive regulation of neuron projection development
  evidence_type: IC
  original_reference_id: PMID:36250347
  review:
    summary: 'Study showing insulin stimulates neurite outgrowth through activation of atypical PKC and

      ARF6-Rac1 signaling.

      '
    action: KEEP_AS_NON_CORE
    reason: 'While insulin does have effects on neuronal development and function, this is not a primary

      core function. The core functions are metabolic regulation. Neuronal effects, while important,

      are secondary to the primary metabolic role.

      '
    supported_by:
    - reference_id: PMID:36250347
      supporting_text: Insulin stimulates atypical protein kinase C-mediated phosphorylation of the neuronal adaptor FE65 to potentiate neurite outgrowth by activating ARF6-Rac1 signaling.
- term:
    id: GO:0048018
    label: receptor ligand activity
  evidence_type: IDA
  original_reference_id: PMID:29512653
  review:
    summary: 'Duplicate of earlier receptor ligand activity annotation with different reference.

      '
    action: ACCEPT
    reason: 'Multiple independent confirmations of receptor ligand activity are valuable.

      '
    supported_by:
    - reference_id: PMID:29512653
      supporting_text: Structure of the insulin receptor-insulin complex by single-particle cryo-EM analysis.
- term:
    id: GO:0010629
    label: negative regulation of gene expression
  evidence_type: IDA
  original_reference_id: PMID:31501273
  review:
    summary: 'This study showed insulin''s involvement in regulating gene expression, particularly through

      microRNA-mediated mechanisms affecting IRS2, INSR, IDE, and LXR pathway.

      '
    action: KEEP_AS_NON_CORE
    reason: 'While insulin does regulate gene expression (e.g., suppression of gluconeogenic genes via

      FoxO1 inhibition), "negative regulation of gene expression" is very broad and non-specific.

      More specific terms like "negative regulation of gluconeogenesis" would be more informative.

      This should be kept but marked as non-core due to lack of specificity.

      '
    supported_by:
    - reference_id: PMID:31501273
      supporting_text: 2019 Nov 15. MicroRNA 7 Impairs Insulin Signaling and Regulates Aβ Levels through Posttranscriptional Regulation of the Insulin Receptor Substrate 2, Insulin Receptor, Insulin-Degrading Enzyme, and Liver X Receptor Pathway.
- term:
    id: GO:0051897
    label: positive regulation of phosphatidylinositol 3-kinase/protein kinase B signal transduction
  evidence_type: IDA
  original_reference_id: PMID:25240198
  review:
    summary: 'Another confirmation of PI3K/Akt pathway activation by insulin.

      '
    action: ACCEPT
    reason: 'Additional experimental support for this core signaling pathway.

      '
    supported_by:
    - reference_id: PMID:25240198
      supporting_text: Epub 2014 Sep 19. Saturated fatty acid-induced miR-195 impairs insulin signaling and glycogen metabolism in HepG2 cells.
- term:
    id: GO:0038060
    label: nitric oxide-cGMP-mediated signaling
  evidence_type: IDA
  original_reference_id: PMID:14744991
  review:
    summary: 'Insulin induces vasodilation through NO-cGMP pathway, involving release of vasodilator

      compounds from platelets.

      '
    action: KEEP_AS_NON_CORE
    reason: 'While insulin does activate NO-cGMP signaling particularly in vascular endothelium, this is

      a secondary effect related to insulin''s vascular actions. Not a core metabolic function,

      though physiologically important for blood flow regulation.

      '
    supported_by:
    - reference_id: PMID:14744991
      supporting_text: Insulin induces the release of vasodilator compounds from platelets by a nitric oxide-G kinase-VAMP-3-dependent pathway.
- term:
    id: GO:0042311
    label: vasodilation
  evidence_type: IDA
  original_reference_id: PMID:14744991
  review:
    summary: 'Insulin causes vasodilation through nitric oxide release.

      '
    action: KEEP_AS_NON_CORE
    reason: 'Vasodilation is a physiologically important effect of insulin but not a core function. The

      core function is metabolic regulation. Vascular effects, while significant, are peripheral

      to the primary role.

      '
    supported_by:
    - reference_id: PMID:14744991
      supporting_text: Insulin induces the release of vasodilator compounds from platelets by a nitric oxide-G kinase-VAMP-3-dependent pathway.
- term:
    id: GO:0042311
    label: vasodilation
  evidence_type: NAS
  original_reference_id: PMID:12946932
  review:
    summary: 'Additional evidence for insulin''s vasodilatory effects.

      '
    action: KEEP_AS_NON_CORE
    reason: 'Duplicate of previous vasodilation annotation with different evidence.

      '
    supported_by:
    - reference_id: PMID:12946932
      supporting_text: Insulin impairs endothelium-dependent vasodilation independent of insulin sensitivity or lipid profile.
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-110011
  review:
    summary: 'Multiple Reactome pathways document insulin in extracellular region during receptor binding

      and signaling.

      '
    action: ACCEPT
    reason: 'This broader term complements the more specific "extracellular space" annotation. Multiple

      Reactome reactions support this.

      '
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-74707
  review:
    summary: 'Reactome annotation for insulin binding to insulin receptor.

      '
    action: ACCEPT
    reason: 'Additional Reactome support for extracellular localization.

      '
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-74711
  review:
    summary: 'Reactome pathway annotation for extracellular region.

      '
    action: ACCEPT
    reason: 'Additional Reactome support.

      '
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-74712
  review:
    summary: 'Reactome pathway annotation.

      '
    action: ACCEPT
    reason: 'Additional Reactome support.

      '
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-74715
  review:
    summary: 'Reactome pathway annotation.

      '
    action: ACCEPT
    reason: 'Additional Reactome support.

      '
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-74716
  review:
    summary: 'Reactome pathway annotation.

      '
    action: ACCEPT
    reason: 'Additional Reactome support.

      '
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-74718
  review:
    summary: 'Reactome pathway annotation.

      '
    action: ACCEPT
    reason: 'Additional Reactome support.

      '
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-74740
  review:
    summary: 'Reactome pathway annotation.

      '
    action: ACCEPT
    reason: 'Additional Reactome support.

      '
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-74742
  review:
    summary: 'Reactome pathway annotation.

      '
    action: ACCEPT
    reason: 'Additional Reactome support.

      '
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-74743
  review:
    summary: 'Reactome pathway annotation.

      '
    action: ACCEPT
    reason: 'Additional Reactome support.

      '
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-976734
  review:
    summary: 'Reactome pathway annotation.

      '
    action: ACCEPT
    reason: 'Additional Reactome support.

      '
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-977136
  review:
    summary: 'Reactome pathway annotation.

      '
    action: ACCEPT
    reason: 'Additional Reactome support.

      '
- term:
    id: GO:0010750
    label: positive regulation of nitric oxide mediated signal transduction
  evidence_type: IDA
  original_reference_id: PMID:15792832
  review:
    summary: 'Insulin positively regulates NO-mediated signaling in placenta and vascular tissue.

      '
    action: KEEP_AS_NON_CORE
    reason: 'While insulin does regulate NO signaling, this is a secondary vascular/endothelial effect

      rather than a core metabolic function. Should be retained but marked as non-core.

      '
    supported_by:
    - reference_id: PMID:15792832
      supporting_text: 2005 Jan 27. Insulin and nitric oxide stimulates glucose transport in human placenta.
- term:
    id: GO:0046326
    label: positive regulation of D-glucose import across plasma membrane
  evidence_type: IDA
  original_reference_id: PMID:15792832
  review:
    summary: 'This is one of THE core functions of insulin - stimulation of glucose uptake through GLUT4

      translocation to the plasma membrane in muscle and adipose tissue.

      '
    action: ACCEPT
    reason: 'This is a core function annotation that captures one of the most important physiological

      actions of insulin - stimulation of glucose uptake. This is essential for glucose homeostasis.

      '
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: The most physiologically important function of insulin is the stimulation of glucose uptake from the bloodstream into insulin-responsive tissues, particularly skeletal muscle and adipose tissue, which together account for the majority of postprandial glucose disposal
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Upon insulin stimulation, GLUT4-containing vesicles rapidly translocate to the plasma membrane, increasing cell surface GLUT4 by 2-3 fold and dramatically enhancing glucose transport capacity
    - reference_id: PMID:15792832
      supporting_text: 2005 Jan 27. Insulin and nitric oxide stimulates glucose transport in human placenta.
- term:
    id: GO:0008284
    label: positive regulation of cell population proliferation
  evidence_type: IDA
  original_reference_id: PMID:7688386
  review:
    summary: 'Insulin and IGF-1 increase mitogenesis in multiple myeloma cell line. Insulin has mitogenic

      effects through MAPK/ERK pathway activation.

      '
    action: KEEP_AS_NON_CORE
    reason: 'While insulin does have growth-promoting and mitogenic effects, particularly through the

      MAPK pathway, this is not the core primary function. The primary function is metabolic

      regulation. Mitogenic effects are secondary, though physiologically important.

      '
    supported_by:
    - reference_id: PMID:7688386
      supporting_text: Insulin and IGF-1 increase mitogenesis and glucose metabolism in the multiple myeloma cell line, RPMI 8226.
- term:
    id: GO:0010750
    label: positive regulation of nitric oxide mediated signal transduction
  evidence_type: IMP
  original_reference_id: PMID:14615391
  review:
    summary: 'Duplicate of earlier NO signaling annotation with different evidence code.

      '
    action: KEEP_AS_NON_CORE
    reason: 'Same as earlier - vascular effect, not core metabolic function.

      '
    supported_by:
    - reference_id: PMID:14615391
      supporting_text: Insulin stimulates glucose transport via nitric oxide/cyclic GMP pathway in human vascular smooth muscle cells.
- term:
    id: GO:1902952
    label: positive regulation of dendritic spine maintenance
  evidence_type: IGI
  original_reference_id: PMID:19188609
  review:
    summary: 'Insulin signaling protects synapses against Alzheimer''s-related toxins and promotes dendritic

      spine maintenance.

      '
    action: KEEP_AS_NON_CORE
    reason: 'Neuronal/synaptic effects of insulin, while important for brain function and potentially

      relevant to neurodegenerative disease, are not core metabolic functions. This is a peripheral

      but interesting function.

      '
    supported_by:
    - reference_id: PMID:19188609
      supporting_text: "Protection of synapses against Alzheimer's-linked toxins: insulin signaling prevents the pathogenic binding of Abeta oligomers."
- term:
    id: GO:1903076
    label: regulation of protein localization to plasma membrane
  evidence_type: IGI
  original_reference_id: PMID:19188609
  review:
    summary: 'This likely refers to insulin''s effect on GLUT4 translocation and other membrane protein

      trafficking events.

      '
    action: ACCEPT
    reason: 'This is mechanistically related to insulin''s core function of stimulating glucose uptake.

      The regulation of GLUT4 localization to plasma membrane is a key mechanism of insulin action.

      While broad, this annotation captures an important aspect of insulin signaling.

      '
    supported_by:
    - reference_id: PMID:19188609
      supporting_text: "Protection of synapses against Alzheimer's-linked toxins: insulin signaling prevents the pathogenic binding of Abeta oligomers."
- term:
    id: GO:1903427
    label: negative regulation of reactive oxygen species biosynthetic process
  evidence_type: IGI
  original_reference_id: PMID:19188609
  review:
    summary: 'Insulin has antioxidant effects and can suppress ROS production.

      '
    action: KEEP_AS_NON_CORE
    reason: 'While insulin does have antioxidant and protective effects, this is not a core function.

      This represents a peripheral effect related to cellular protection.

      '
    supported_by:
    - reference_id: PMID:19188609
      supporting_text: "Protection of synapses against Alzheimer's-linked toxins: insulin signaling prevents the pathogenic binding of Abeta oligomers."
- term:
    id: GO:1990535
    label: neuron projection maintenance
  evidence_type: IGI
  original_reference_id: PMID:19188609
  review:
    summary: 'Insulin signaling supports maintenance of neuronal projections.

      '
    action: KEEP_AS_NON_CORE
    reason: 'Neuronal effect, not core metabolic function.

      '
    supported_by:
    - reference_id: PMID:19188609
      supporting_text: "Protection of synapses against Alzheimer's-linked toxins: insulin signaling prevents the pathogenic binding of Abeta oligomers."
- term:
    id: GO:1900273
    label: positive regulation of long-term synaptic potentiation
  evidence_type: TAS
  original_reference_id: PMID:19188609
  review:
    summary: 'Insulin enhances synaptic plasticity and long-term potentiation in hippocampus.

      '
    action: KEEP_AS_NON_CORE
    reason: 'Neuronal/cognitive effect, not core metabolic function.

      '
    supported_by:
    - reference_id: PMID:19188609
      supporting_text: "Protection of synapses against Alzheimer's-linked toxins: insulin signaling prevents the pathogenic binding of Abeta oligomers."
- term:
    id: GO:0048167
    label: regulation of synaptic plasticity
  evidence_type: TAS
  original_reference_id: PMID:19188609
  review:
    summary: 'Insulin regulates synaptic plasticity.

      '
    action: KEEP_AS_NON_CORE
    reason: 'Neuronal effect, not core metabolic function.

      '
    supported_by:
    - reference_id: PMID:19188609
      supporting_text: "Protection of synapses against Alzheimer's-linked toxins: insulin signaling prevents the pathogenic binding of Abeta oligomers."
- term:
    id: GO:0050890
    label: cognition
  evidence_type: TAS
  original_reference_id: PMID:19188609
  review:
    summary: 'Insulin has roles in cognitive function.

      '
    action: KEEP_AS_NON_CORE
    reason: 'This is an extremely broad term. While insulin does affect cognition, this annotation is

      not specific or informative about insulin''s actual function. Should be kept as non-core

      but is borderline over-annotation.

      '
    supported_by:
    - reference_id: PMID:19188609
      supporting_text: "Protection of synapses against Alzheimer's-linked toxins: insulin signaling prevents the pathogenic binding of Abeta oligomers."
- term:
    id: GO:0010628
    label: positive regulation of gene expression
  evidence_type: IGI
  original_reference_id: PMID:25403480
  review:
    summary: 'Insulin regulates gene expression through various mechanisms including effects on transcription

      factors and microRNAs.

      '
    action: KEEP_AS_NON_CORE
    reason: 'While insulin does regulate gene expression (e.g., lipogenic genes via SREBP-1c, suppression

      of gluconeogenic genes), this term is extremely broad and non-specific. More specific terms

      about particular pathways would be more informative.

      '
    supported_by:
    - reference_id: PMID:25403480
      supporting_text: 'Nov 19. Glucose tolerance is associated with differential expression of microRNAs in skeletal muscle: results from studies of twins with and without type 2 diabetes.'
- term:
    id: GO:0043410
    label: positive regulation of MAPK cascade
  evidence_type: IDA
  original_reference_id: PMID:20455999
  review:
    summary: 'Insulin activates the MAPK/ERK cascade through SHC-Grb2-SOS-Ras-Raf-MEK-ERK pathway. This is

      one of the two major signaling cascades activated by insulin receptor.

      '
    action: ACCEPT
    reason: 'The MAPK pathway is one of the two major signaling cascades downstream of insulin receptor

      (along with PI3K/Akt). While it plays a more prominent role in growth/proliferation than

      acute metabolic effects, it is still a core signaling pathway for insulin.

      '
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: In parallel with the PI3K/AKT pathway, insulin also activates the mitogen-activated protein kinase (MAPK) pathway primarily through interaction of the SHC adaptor protein with the phosphorylated insulin receptor
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: The MAPK pathway mediated by ERK1/2 has distinct biological effects compared to the PI3K/AKT pathway, with the MAPK pathway playing a more prominent role in the regulation of gene expression and cell proliferation
    - reference_id: PMID:20455999
      supporting_text: 'A novel domain of caveolin-2 that controls nuclear targeting: regulation of insulin-specific ERK activation and nuclear translocation by caveolin-2.'
- term:
    id: GO:1900182
    label: positive regulation of protein localization to nucleus
  evidence_type: IDA
  original_reference_id: PMID:20455999
  review:
    summary: 'Study on caveolin-2 regulation of insulin-specific ERK activation and nuclear translocation.

      '
    action: KEEP_AS_NON_CORE
    reason: 'While insulin signaling does regulate nuclear translocation of various proteins (e.g., ERK,

      FoxO1), this is a very broad and non-specific annotation. It''s mechanistically accurate but

      not informative about insulin''s core functions.

      '
    supported_by:
    - reference_id: PMID:20455999
      supporting_text: 'A novel domain of caveolin-2 that controls nuclear targeting: regulation of insulin-specific ERK activation and nuclear translocation by caveolin-2.'
- term:
    id: GO:0050995
    label: negative regulation of lipid catabolic process
  evidence_type: IMP
  original_reference_id: PMID:24675707
  review:
    summary: |
      Insulin potently inhibits lipolysis in adipose tissue through
      inactivation of hormone-sensitive lipase. This is a core metabolic
      function and is amply supported by the deep research findings.
      However, the GOA-cited reference (PMID:24675707) is a dairy cow
      resistin paper, not a human insulin IMP study (verified during PR
      #764 round-2 review). Action retained as ACCEPT on the basis of
      the deep-research-supported function, with the misattributed
      reference flagged for GOA correction.
    action: ACCEPT
    reason: |
      Inhibition of lipolysis is a core, textbook metabolic function of
      insulin (see deep research supporting_text below). The GOA
      reference PMID:24675707 is misattributed (dairy cow resistin
      paper) and does not support this IMP annotation; flagged for
      GOA-side correction but the underlying biology is sound.
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Reciprocally, insulin potently inhibits lipolysis in adipose tissue through inactivation of hormone-sensitive lipase (HSL) via a PKA-independent mechanism
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: The net result is decreased adipose tissue lipolysis and reduced circulating free fatty acid levels
- term:
    id: GO:1902176
    label: negative regulation of oxidative stress-induced intrinsic apoptotic signaling pathway
  evidence_type: NAS
  original_reference_id: PMID:16604263
  review:
    summary: 'Insulin provides neuroprotection against oxidative stress-induced apoptosis through PI3K/Akt

      pathway.

      '
    action: KEEP_AS_NON_CORE
    reason: 'While insulin does have anti-apoptotic and neuroprotective effects, this is not a core

      metabolic function. This represents a protective/survival effect that is peripheral to the

      primary role.

      '
    supported_by:
    - reference_id: PMID:16604263
      supporting_text: 'Neuroprotection of insulin against oxidative stress-induced apoptosis in cultured retinal neurons: involvement of phosphoinositide 3-kinase/Akt signal pathway.'
- term:
    id: GO:0031904
    label: endosome lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-74718
  review:
    summary: 'After internalization of the insulin-insulin receptor complex, insulin traffics through

      endosomes where it can be degraded or the receptor recycled.

      '
    action: ACCEPT
    reason: 'This is an accurate annotation for insulin trafficking after receptor-mediated endocytosis.

      The endosomal pathway is important for both insulin degradation and receptor recycling.

      '
- term:
    id: GO:0031904
    label: endosome lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-74726
  review:
    summary: 'Reactome pathway for insulin in endosomes.

      '
    action: ACCEPT
    reason: 'Additional Reactome support for endosomal localization.

      '
- term:
    id: GO:0031904
    label: endosome lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-74730
  review:
    summary: 'Reactome pathway for insulin degradation in endosomes.

      '
    action: ACCEPT
    reason: 'Insulin is degraded in endosomes by insulin-degrading enzyme.

      '
- term:
    id: GO:0090277
    label: positive regulation of peptide hormone secretion
  evidence_type: TAS
  original_reference_id: PMID:11387233
  review:
    summary: 'Insulin can regulate secretion of other peptide hormones like leptin.

      '
    action: KEEP_AS_NON_CORE
    reason: 'While insulin does affect secretion of other hormones, this is not a core function. The

      primary function is metabolic regulation through direct cellular effects, not through

      regulating other hormones (though that does occur).

      '
    supported_by:
    - reference_id: PMID:11387233
      supporting_text: Insulin and glucocorticoids differentially regulate leptin transcription and secretion in brown adipocytes.
- term:
    id: GO:0090336
    label: positive regulation of brown fat cell differentiation
  evidence_type: TAS
  original_reference_id: PMID:11387233
  review:
    summary: 'Insulin promotes brown adipocyte differentiation.

      '
    action: KEEP_AS_NON_CORE
    reason: 'While insulin does have effects on adipocyte differentiation, this is a developmental/

      differentiation effect rather than a core acute metabolic function. Should be retained but

      marked as non-core.

      '
    supported_by:
    - reference_id: PMID:11387233
      supporting_text: Insulin and glucocorticoids differentially regulate leptin transcription and secretion in brown adipocytes.
- term:
    id: GO:0002020
    label: protease binding
  evidence_type: IPI
  original_reference_id: PMID:20082125
  review:
    summary: 'Insulin binds to insulin-degrading enzyme (IDE), a metalloprotease that degrades insulin.

      '
    action: ACCEPT
    reason: 'This is a more specific and informative term than generic "protein binding". Binding to IDE

      is functionally important for insulin clearance and degradation. This is an appropriate

      annotation.

      '
    supported_by:
    - reference_id: PMID:20082125
      supporting_text: In vitro degradation of insulin-like peptide 3 by insulin-degrading enzyme.
- term:
    id: GO:0045840
    label: positive regulation of mitotic nuclear division
  evidence_type: IDA
  original_reference_id: PMID:10644978
  review:
    summary: 'Insulin stimulates mitosis through activation of mitogenic signaling pathways.

      '
    action: KEEP_AS_NON_CORE
    reason: 'Mitogenic effects are secondary to core metabolic functions, mediated primarily through

      MAPK pathway. Should be retained but as non-core.

      '
    supported_by:
    - reference_id: PMID:10644978
      supporting_text: PSM, a mediator of PDGF-BB-, IGF-I-, and insulin-stimulated mitogenesis.
- term:
    id: GO:2000252
    label: negative regulation of feeding behavior
  evidence_type: IDA
  original_reference_id: PMID:17957153
  review:
    summary: 'Insulin acts in the brain to suppress appetite and reduce food intake.

      '
    action: KEEP_AS_NON_CORE
    reason: 'While insulin''s central effects on appetite are physiologically important and contribute to

      overall energy homeostasis, this is not a direct metabolic function. It''s a behavioral/

      neurological effect that is peripheral to core function.

      '
    supported_by:
    - reference_id: PMID:17957153
      supporting_text: Milk intake and feeding behavior in the first week of life and its relationship to cord blood ghrelin, leptin, and insulin concentrations.
- term:
    id: GO:0060267
    label: positive regulation of respiratory burst
  evidence_type: IDA
  original_reference_id: PMID:9092559
  review:
    summary: 'Insulin can stimulate NADPH oxidase and ROS production in adipocytes.

      '
    action: KEEP_AS_NON_CORE
    reason: 'Respiratory burst regulation is an immune cell function. While insulin may affect ROS

      production in some contexts, this is not a core function and may represent a non-specific

      effect.

      '
    supported_by:
    - reference_id: PMID:9092559
      supporting_text: Insulin-induced activation of NADPH-dependent H2O2 generation in human adipocyte plasma membranes is mediated by Galphai2.
- term:
    id: GO:0030335
    label: positive regulation of cell migration
  evidence_type: ISS
  original_reference_id: PMID:12138094
  review:
    summary: 'Insulin can promote cell migration.

      '
    action: KEEP_AS_NON_CORE
    reason: 'Cell migration effects are not core metabolic functions. This is a peripheral cellular effect.

      '
    supported_by:
    - reference_id: PMID:12138094
      supporting_text: 2002 Jul 22. Insulin/insulin-like growth factor I hybrid receptors have different biological characteristics depending on the insulin receptor isoform involved.
- term:
    id: GO:0043410
    label: positive regulation of MAPK cascade
  evidence_type: IDA
  original_reference_id: PMID:11500939
  review:
    summary: 'Duplicate of earlier MAPK annotation with different reference.

      '
    action: ACCEPT
    reason: 'Additional experimental support for core MAPK pathway activation.

      '
    supported_by:
    - reference_id: PMID:11500939
      supporting_text: Regulation of the Akt/Glycogen synthase kinase-3 axis by insulin-like growth factor-II via activation of the human insulin receptor isoform-A.
- term:
    id: GO:0045840
    label: positive regulation of mitotic nuclear division
  evidence_type: IDA
  original_reference_id: PMID:11500939
  review:
    summary: 'Duplicate mitosis annotation.

      '
    action: KEEP_AS_NON_CORE
    reason: 'Same as earlier - mitogenic effect, not core function.

      '
    supported_by:
    - reference_id: PMID:11500939
      supporting_text: Regulation of the Akt/Glycogen synthase kinase-3 axis by insulin-like growth factor-II via activation of the human insulin receptor isoform-A.
- term:
    id: GO:0051897
    label: positive regulation of phosphatidylinositol 3-kinase/protein kinase B signal transduction
  evidence_type: IDA
  original_reference_id: PMID:11500939
  review:
    summary: 'Another confirmation of PI3K/Akt pathway.

      '
    action: ACCEPT
    reason: 'Additional support for core PI3K/Akt signaling.

      '
    supported_by:
    - reference_id: PMID:11500939
      supporting_text: Regulation of the Akt/Glycogen synthase kinase-3 axis by insulin-like growth factor-II via activation of the human insulin receptor isoform-A.
- term:
    id: GO:0051897
    label: positive regulation of phosphatidylinositol 3-kinase/protein kinase B signal transduction
  evidence_type: IDA
  original_reference_id: PMID:7688386
  review:
    summary: 'Another PI3K/Akt confirmation.

      '
    action: ACCEPT
    reason: 'Additional support for core pathway.

      '
    supported_by:
    - reference_id: PMID:7688386
      supporting_text: Insulin and IGF-1 increase mitogenesis and glucose metabolism in the multiple myeloma cell line, RPMI 8226.
- term:
    id: GO:0008284
    label: positive regulation of cell population proliferation
  evidence_type: IDA
  original_reference_id: PMID:17925406
  review:
    summary: 'Duplicate proliferation annotation.

      '
    action: KEEP_AS_NON_CORE
    reason: 'Mitogenic effect, not core metabolic function.

      '
    supported_by:
    - reference_id: PMID:17925406
      supporting_text: 2007 Oct 9. Activation of the insulin receptor by insulin and a synthetic peptide leads to divergent metabolic and mitogenic signaling and responses.
- term:
    id: GO:0045725
    label: positive regulation of glycogen biosynthetic process
  evidence_type: IDA
  original_reference_id: PMID:17925406
  review:
    summary: 'Insulin stimulates glycogen synthesis through activation of glycogen synthase. This is a

      core metabolic function.

      '
    action: ACCEPT
    reason: 'Glycogen synthesis is a core metabolic function of insulin. In the fed state, insulin promotes

      storage of glucose as glycogen in liver and muscle, which is essential for glucose homeostasis.

      '
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Simultaneously, insulin activates glycogen synthase through PP1-mediated dephosphorylation, promoting the synthesis of new glycogen from glucose-6-phosphate
    - reference_id: file:human/INS/INS-uniprot.txt
      supporting_text: It accelerates glycolysis, the pentose phosphate cycle, and glycogen synthesis in liver.
    - reference_id: PMID:17925406
      supporting_text: 2007 Oct 9. Activation of the insulin receptor by insulin and a synthetic peptide leads to divergent metabolic and mitogenic signaling and responses.
- term:
    id: GO:0030307
    label: positive regulation of cell growth
  evidence_type: NAS
  original_reference_id: PMID:11742412
  review:
    summary: 'Insulin promotes cell growth through activation of protein synthesis and suppression of

      protein degradation.

      '
    action: KEEP_AS_NON_CORE
    reason: 'While insulin does promote cell growth, this is secondary to its core metabolic functions.

      Growth-promoting effects are mediated through mTOR pathway and protein synthesis machinery.

      '
    supported_by:
    - reference_id: PMID:11742412
      supporting_text: Insulin signalling and the regulation of glucose and lipid metabolism.
- term:
    id: GO:0045597
    label: positive regulation of cell differentiation
  evidence_type: NAS
  original_reference_id: PMID:11742412
  review:
    summary: 'Insulin affects differentiation of various cell types including adipocytes.

      '
    action: KEEP_AS_NON_CORE
    reason: 'Differentiation effects are developmental rather than acute metabolic functions. Non-core.

      '
    supported_by:
    - reference_id: PMID:11742412
      supporting_text: Insulin signalling and the regulation of glucose and lipid metabolism.
- term:
    id: GO:0045721
    label: negative regulation of gluconeogenesis
  evidence_type: NAS
  original_reference_id: PMID:11742412
  review:
    summary: 'Insulin suppresses hepatic gluconeogenesis through inhibition of FoxO1 and CREB transcription

      factors, reducing expression of PEPCK and G6Pase. This is a core metabolic function.

      '
    action: ACCEPT
    reason: 'Suppression of hepatic gluconeogenesis is a core function of insulin, essential for preventing

      excessive glucose production by the liver in the fed state. This is critical for glucose

      homeostasis.

      '
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: The suppression of hepatic gluconeogenesis by insulin involves inhibition of the transcription factors CREB and FoxO1, which normally activate the expression of the rate-limiting gluconeogenic enzymes phosphoenolpyruvate carboxylase (PEPCK) and glucose-6-phosphatase
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: The AKT-mediated phosphorylation and inactivation of FoxO1, combined with reduced CREB activity following insulin treatment, leads to decreased expression of gluconeogenic enzymes and reduced hepatic glucose production
    - reference_id: PMID:11742412
      supporting_text: Insulin signalling and the regulation of glucose and lipid metabolism.
- term:
    id: GO:0046889
    label: positive regulation of lipid biosynthetic process
  evidence_type: NAS
  original_reference_id: PMID:11742412
  review:
    summary: 'Insulin stimulates lipogenesis through activation of SREBP-1c and lipogenic enzymes including

      fatty acid synthase and acetyl-CoA carboxylase. This is a core metabolic function.

      '
    action: ACCEPT
    reason: 'Lipogenesis is a core metabolic function of insulin. In the fed state, insulin promotes

      synthesis of fatty acids and triglycerides for energy storage, which is essential for energy

      homeostasis.

      '
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Insulin is a potent anabolic hormone that stimulates fatty acid synthesis and triglyceride storage in adipose tissue and liver through multiple transcriptional and post-translational mechanisms
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Upon insulin stimulation, SREBP-1c undergoes proteolytic activation in the Golgi apparatus, releasing the transcriptionally active N-terminal fragment that translocates to the nucleus and activates transcription of genes encoding enzymes required for fatty acid synthesis
    - reference_id: PMID:11742412
      supporting_text: Insulin signalling and the regulation of glucose and lipid metabolism.
- term:
    id: GO:0050995
    label: negative regulation of lipid catabolic process
  evidence_type: NAS
  original_reference_id: PMID:11742412
  review:
    summary: 'Duplicate of earlier lipolysis inhibition annotation.

      '
    action: ACCEPT
    reason: 'Core metabolic function - inhibition of lipolysis.

      '
    supported_by:
    - reference_id: PMID:11742412
      supporting_text: Insulin signalling and the regulation of glucose and lipid metabolism.
- term:
    id: GO:0060266
    label: negative regulation of respiratory burst involved in inflammatory response
  evidence_type: IDA
  original_reference_id: PMID:11443198
  review:
    summary: 'Insulin has anti-inflammatory effects including suppression of inflammatory ROS production.

      '
    action: KEEP_AS_NON_CORE
    reason: 'Anti-inflammatory effects are not core metabolic functions. These are peripheral effects.

      '
    supported_by:
    - reference_id: PMID:11443198
      supporting_text: 'Insulin inhibits intranuclear nuclear factor kappaB and stimulates IkappaB in mononuclear cells in obese subjects: evidence for an anti-inflammatory effect? Dandona P(1), Aljada A, Mohanty P, Ghanim H, Hamouda W, Assian E, Ahmad S.'
- term:
    id: GO:0045821
    label: positive regulation of glycolytic process
  evidence_type: IMP
  original_reference_id: PMID:381941
  review:
    summary: 'Insulin stimulates glycolysis by increasing glucose uptake and promoting glycolytic enzyme

      activity.

      '
    action: ACCEPT
    reason: 'Stimulation of glycolysis is a core metabolic function of insulin. Insulin promotes glucose

      utilization through glycolysis, which is part of its overall role in glucose homeostasis.

      '
    supported_by:
    - reference_id: file:human/INS/INS-uniprot.txt
      supporting_text: It accelerates glycolysis, the pentose phosphate cycle, and glycogen synthesis in liver.
    - reference_id: PMID:381941
      supporting_text: A structurally abnormal insulin causing human diabetes.
- term:
    id: GO:0006355
    label: regulation of DNA-templated transcription
  evidence_type: NAS
  original_reference_id: PMID:12881524
  review:
    summary: 'Insulin regulates transcription of many genes.

      '
    action: KEEP_AS_NON_CORE
    reason: 'This is an extremely broad and non-specific term. While insulin does regulate transcription

      (e.g., lipogenic genes, gluconeogenic genes), this annotation is too general to be informative.

      More specific terms about particular genes or pathways would be better.

      '
    supported_by:
    - reference_id: PMID:12881524
      supporting_text: 2003 Jul 24. Differential gene expression induced by insulin and insulin-like growth factor-II through the insulin receptor isoform A.
- term:
    id: GO:0007186
    label: G protein-coupled receptor signaling pathway
  evidence_type: IDA
  original_reference_id: PMID:9092559
  review:
    summary: 'Study showing insulin-induced NADPH-dependent H2O2 generation is mediated by Gαi2, suggesting

      crosstalk with GPCR pathways.

      '
    action: KEEP_AS_NON_CORE
    reason: 'While there may be some crosstalk between insulin signaling and GPCR pathways, insulin itself

      signals through a receptor tyrosine kinase, not a GPCR. This annotation may represent indirect

      effects or experimental artifacts. Should be kept but as non-core with skepticism.

      '
    supported_by:
    - reference_id: PMID:9092559
      supporting_text: Insulin-induced activation of NADPH-dependent H2O2 generation in human adipocyte plasma membranes is mediated by Galphai2.
- term:
    id: GO:0006953
    label: acute-phase response
  evidence_type: IDA
  original_reference_id: PMID:14739855
  review:
    summary: 'Insulin decreases hepatic acute phase protein levels.

      '
    action: KEEP_AS_NON_CORE
    reason: 'Effects on acute phase response are not core metabolic functions. This is a peripheral

      effect related to inflammation/stress responses.

      '
    supported_by:
    - reference_id: PMID:14739855
      supporting_text: Insulin decreases hepatic acute phase protein levels in severely burned children.
- term:
    id: GO:0032880
    label: regulation of protein localization
  evidence_type: IDA
  original_reference_id: PMID:14615391
  review:
    summary: 'Very broad term covering insulin''s effects on protein trafficking including GLUT4 translocation.

      '
    action: ACCEPT
    reason: 'While this is a broad term, it does capture important mechanisms like GLUT4 translocation

      which are central to insulin action. The term is accurate even if not maximally specific.

      '
    supported_by:
    - reference_id: PMID:14615391
      supporting_text: Insulin stimulates glucose transport via nitric oxide/cyclic GMP pathway in human vascular smooth muscle cells.
- term:
    id: GO:0042060
    label: wound healing
  evidence_type: IDA
  original_reference_id: PMID:9498508
  review:
    summary: 'Insulin has effects on wound healing processes.

      '
    action: KEEP_AS_NON_CORE
    reason: 'Wound healing effects are not core metabolic functions. These are peripheral tissue

      repair effects.

      '
    supported_by:
    - reference_id: PMID:9498508
      supporting_text: Effects of insulin on wound healing.
- term:
    id: GO:0046326
    label: positive regulation of D-glucose import across plasma membrane
  evidence_type: IDA
  original_reference_id: PMID:14615391
  review:
    summary: 'Duplicate glucose uptake annotation.

      '
    action: ACCEPT
    reason: 'Core function - additional experimental support.

      '
    supported_by:
    - reference_id: PMID:14615391
      supporting_text: Insulin stimulates glucose transport via nitric oxide/cyclic GMP pathway in human vascular smooth muscle cells.
- term:
    id: GO:0050709
    label: negative regulation of protein secretion
  evidence_type: IDA
  original_reference_id: PMID:14739855
  review:
    summary: 'Insulin can suppress secretion of certain proteins like acute phase proteins.

      '
    action: KEEP_AS_NON_CORE
    reason: 'Effects on protein secretion are not core functions. This is a peripheral effect.

      '
    supported_by:
    - reference_id: PMID:14739855
      supporting_text: Insulin decreases hepatic acute phase protein levels in severely burned children.
- term:
    id: GO:0055089
    label: fatty acid homeostasis
  evidence_type: IMP
  original_reference_id: PMID:1184755
  review:
    summary: 'Insulin regulates fatty acid homeostasis through effects on lipogenesis, lipolysis, and

      fatty acid oxidation.

      '
    action: ACCEPT
    reason: 'Fatty acid homeostasis is a core metabolic function of insulin. Insulin regulates both

      synthesis and breakdown of fatty acids, which is integral to overall energy homeostasis.

      This is an appropriate high-level annotation.

      '
    supported_by:
    - reference_id: PMID:1184755
      supporting_text: Glucagon regulation of plasma ketone body concentration in human diabetes.
- term:
    id: GO:0002674
    label: negative regulation of acute inflammatory response
  evidence_type: IDA
  original_reference_id: PMID:11443198
  review:
    summary: 'Insulin has anti-inflammatory effects.

      '
    action: KEEP_AS_NON_CORE
    reason: 'Anti-inflammatory effects are not core metabolic functions.

      '
    supported_by:
    - reference_id: PMID:11443198
      supporting_text: 'Insulin inhibits intranuclear nuclear factor kappaB and stimulates IkappaB in mononuclear cells in obese subjects: evidence for an anti-inflammatory effect? Dandona P(1), Aljada A, Mohanty P, Ghanim H, Hamouda W, Assian E, Ahmad S.'
- term:
    id: GO:0005158
    label: insulin receptor binding
  evidence_type: IDA
  original_reference_id: PMID:9667398
  review:
    summary: 'Direct experimental evidence for insulin receptor binding.

      '
    action: ACCEPT
    reason: 'Additional IDA support for the core molecular function.

      '
    supported_by:
    - reference_id: PMID:9667398
      supporting_text: 'Familial hyperproinsulinaemia due to a mutation substituting histidine for arginine at position 65 in proinsulin: identification of the mutation by restriction enzyme mapping.'
- term:
    id: GO:0005179
    label: hormone activity
  evidence_type: IC
  original_reference_id: PMID:9667398
  review:
    summary: 'Another hormone activity annotation.

      '
    action: ACCEPT
    reason: 'Additional support for hormone activity.

      '
    supported_by:
    - reference_id: PMID:9667398
      supporting_text: 'Familial hyperproinsulinaemia due to a mutation substituting histidine for arginine at position 65 in proinsulin: identification of the mutation by restriction enzyme mapping.'
- term:
    id: GO:0042593
    label: glucose homeostasis
  evidence_type: IMP
  original_reference_id: PMID:381941
  review:
    summary: 'Study on structurally abnormal insulin causing diabetes demonstrates insulin''s role in

      glucose homeostasis.

      '
    action: ACCEPT
    reason: 'Core function - genetic evidence from natural mutation.

      '
    supported_by:
    - reference_id: PMID:381941
      supporting_text: A structurally abnormal insulin causing human diabetes.
- term:
    id: GO:0045818
    label: negative regulation of glycogen catabolic process
  evidence_type: IMP
  original_reference_id: PMID:381941
  review:
    summary: 'Insulin inhibits glycogenolysis (glycogen breakdown) in liver and muscle.

      '
    action: ACCEPT
    reason: 'Inhibition of glycogenolysis is a core function of insulin. In the fed state, insulin

      suppresses glycogen breakdown while promoting glycogen synthesis, which is essential for

      glucose homeostasis.

      '
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Insulin rapidly inhibits hepatic glycogenolysis through mechanisms involving protein phosphatase-1 (PP1), which is activated through insulin-mediated suppression of glycogen phosphorylase kinase
    - reference_id: PMID:381941
      supporting_text: A structurally abnormal insulin causing human diabetes.
- term:
    id: GO:0045922
    label: negative regulation of fatty acid metabolic process
  evidence_type: IMP
  original_reference_id: PMID:1184755
  review:
    summary: 'Insulin inhibits fatty acid oxidation and mobilization.

      '
    action: ACCEPT
    reason: 'Suppression of fatty acid oxidation and mobilization (lipolysis) is a core metabolic function.

      This complements the earlier annotation on inhibition of lipolysis.

      '
    supported_by:
    - reference_id: PMID:1184755
      supporting_text: Glucagon regulation of plasma ketone body concentration in human diabetes.
- term:
    id: GO:0045821
    label: positive regulation of glycolytic process
  evidence_type: IDA
  original_reference_id: PMID:7688386
  review:
    summary: 'Duplicate glycolysis annotation.

      '
    action: ACCEPT
    reason: 'Core function - additional experimental support.

      '
    supported_by:
    - reference_id: PMID:7688386
      supporting_text: Insulin and IGF-1 increase mitogenesis and glucose metabolism in the multiple myeloma cell line, RPMI 8226.
- term:
    id: GO:0046628
    label: positive regulation of insulin receptor signaling pathway
  evidence_type: IDA
  original_reference_id: PMID:7688386
  review:
    summary: 'Insulin positively regulates its own receptor signaling pathway by binding and activating

      the receptor.

      '
    action: ACCEPT
    reason: 'This is essentially describing insulin''s primary mechanism of action. While it may seem

      redundant with "insulin receptor binding" and "insulin receptor signaling pathway", it

      correctly captures that insulin is the positive regulator of this pathway. Acceptable.

      '
    supported_by:
    - reference_id: PMID:7688386
      supporting_text: Insulin and IGF-1 increase mitogenesis and glucose metabolism in the multiple myeloma cell line, RPMI 8226.
- term:
    id: GO:0005158
    label: insulin receptor binding
  evidence_type: IPI
  original_reference_id: PMID:8452530
  review:
    summary: 'Another insulin receptor binding annotation.

      '
    action: ACCEPT
    reason: 'Additional experimental support for core molecular function.

      '
    supported_by:
    - reference_id: PMID:8452530
      supporting_text: Purified hybrid insulin/insulin-like growth factor-I receptors bind insulin-like growth factor-I, but not insulin, with high affinity.
- term:
    id: GO:0005159
    label: insulin-like growth factor receptor binding
  evidence_type: IPI
  original_reference_id: PMID:8452530
  review:
    summary: 'Study on hybrid insulin/IGF-I receptors. Insulin can bind to IGF-I receptor with lower

      affinity than to insulin receptor.

      '
    action: KEEP_AS_NON_CORE
    reason: 'While insulin can bind to IGF-I receptors, particularly hybrid receptors, this is not the

      primary physiological binding partner. The insulin receptor is the specific high-affinity

      receptor. IGF-I receptor binding represents cross-reactivity rather than core function.

      '
    supported_by:
    - reference_id: PMID:8452530
      supporting_text: Purified hybrid insulin/insulin-like growth factor-I receptors bind insulin-like growth factor-I, but not insulin, with high affinity.
- term:
    id: GO:0005158
    label: insulin receptor binding
  evidence_type: IDA
  original_reference_id: PMID:7556975
  review:
    summary: 'Another insulin receptor binding annotation.

      '
    action: ACCEPT
    reason: 'Additional support for core molecular function.

      '
    supported_by:
    - reference_id: PMID:7556975
      supporting_text: Binding of human, porcine and bovine insulin to insulin receptors from human brain, muscle and adipocytes and to expressed recombinant alternatively spliced insulin receptor isoforms.
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: IC
  original_reference_id: PMID:7556975
  review:
    summary: 'Another extracellular region annotation.

      '
    action: ACCEPT
    reason: 'Additional support for extracellular localization.

      '
    supported_by:
    - reference_id: PMID:7556975
      supporting_text: Binding of human, porcine and bovine insulin to insulin receptors from human brain, muscle and adipocytes and to expressed recombinant alternatively spliced insulin receptor isoforms.
- term:
    id: GO:0007267
    label: cell-cell signaling
  evidence_type: IC
  original_reference_id: PMID:7556975
  review:
    summary: 'Insulin functions as a cell-cell signaling molecule, being secreted from beta cells and

      signaling to distant target cells.

      '
    action: ACCEPT
    reason: 'This is an accurate high-level annotation. Insulin is a classic example of endocrine

      cell-cell signaling. While not maximally specific, this term correctly categorizes insulin''s

      biological role.

      '
    supported_by:
    - reference_id: PMID:7556975
      supporting_text: Binding of human, porcine and bovine insulin to insulin receptors from human brain, muscle and adipocytes and to expressed recombinant alternatively spliced insulin receptor isoforms.
- term:
    id: GO:0001819
    label: positive regulation of cytokine production
  evidence_type: IDA
  original_reference_id: PMID:15473891
  review:
    summary: 'Insulin can stimulate production of cytokines like VEGF.

      '
    action: KEEP_AS_NON_CORE
    reason: 'Effects on cytokine production are not core metabolic functions. This represents an

      immunological/inflammatory effect that is peripheral.

      '
    supported_by:
    - reference_id: PMID:15473891
      supporting_text: 'Insulin activates vascular endothelial growth factor in vascular smooth muscle cells: influence of nitric oxide and of insulin resistance.'
- term:
    id: GO:0042177
    label: negative regulation of protein catabolic process
  evidence_type: IDA
  original_reference_id: PMID:15185208
  review:
    summary: 'Insulin suppresses protein degradation through inhibition of proteasome and autophagy pathways.

      '
    action: ACCEPT
    reason: 'Suppression of protein degradation is a core anabolic function of insulin. Along with

      stimulation of protein synthesis, inhibition of protein breakdown contributes to insulin''s

      overall anabolic effects.

      '
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Insulin is also a powerful regulator of protein turnover, stimulating protein synthesis while simultaneously inhibiting protein degradation, thereby promoting net protein anabolism
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: In contrast, insulin suppresses hepatic protein degradation through inhibition of the ATP-ubiquitin-dependent proteasome pathway and ATP-independent lysosomal proteases
    - reference_id: PMID:15185208
      supporting_text: Intravenous insulin decreases protein breakdown in infants on extracorporeal membrane oxygenation.
- term:
    id: GO:0046631
    label: alpha-beta T cell activation
  evidence_type: IDA
  original_reference_id: PMID:10604997
  review:
    summary: 'Study showing insulin can activate T cells.

      '
    action: KEEP_AS_NON_CORE
    reason: 'T cell activation is an immunological function, not a core metabolic function. This is a

      peripheral effect and may even be pathological in the context of type 1 diabetes where

      insulin can serve as an autoantigen.

      '
    supported_by:
    - reference_id: PMID:10604997
      supporting_text: Bovine and human insulin activate CD8+-autoreactive CTL expressing both type 1 and type 2 cytokines in C57BL/6 mice.
- term:
    id: GO:0050708
    label: regulation of protein secretion
  evidence_type: IDA
  original_reference_id: PMID:15591776
  review:
    summary: 'Insulin regulates secretion of various proteins including apolipoproteins.

      '
    action: KEEP_AS_NON_CORE
    reason: 'While insulin does affect protein secretion in some contexts (e.g., apolipoprotein secretion

      from hepatocytes), this is not a core function. More specific terms about lipid metabolism

      would be more appropriate.

      '
    supported_by:
    - reference_id: PMID:15591776
      supporting_text: Insulin decreases the secretion of apoB-100 from hepatic HepG2 cells but does not decrease the secretion of apoB-48 from intestinal CaCo-2 cells.
- term:
    id: GO:0051000
    label: positive regulation of nitric-oxide synthase activity
  evidence_type: NAS
  original_reference_id: PMID:12135947
  review:
    summary: 'Insulin activates endothelial nitric oxide synthase (eNOS).

      '
    action: KEEP_AS_NON_CORE
    reason: 'NO synthase activation is a vascular endothelial effect, not a core metabolic function.

      This is related to insulin''s vascular actions.

      '
    supported_by:
    - reference_id: PMID:12135947
      supporting_text: Insulin-dependent activation of endothelial nitric oxide synthase is impaired by O-linked glycosylation modification of signaling proteins in human coronary endothelial cells.
- term:
    id: GO:1904659
    label: D-glucose transmembrane transport
  evidence_type: NAS
  review:
    summary: Added to align core_functions with existing annotations.
    action: NEW
    reason: Core function term not present in existing_annotations.
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: The most physiologically important function of insulin is the stimulation of glucose uptake from the bloodstream into insulin-responsive tissues, particularly skeletal muscle and adipose tissue, which together account for the majority of postprandial glucose disposal. This metabolic action is mediated through the insulin-dependent translocation of glucose transporter type-4 (GLUT4) from intracellular membrane compartments to the plasma membrane
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Following AKT activation, the serine/threonine kinase AS160 (also known as TBC1D4) is phosphorylated by AKT, leading to its release from GLUT4-containing storage vesicles. This phosphorylation event activates the RabGAP activity of AS160, converting Rab small GTPases to their inactive GDP-bound state and enabling GLUT4 vesicle mobilization
# GO:0046323 (obsolete D-glucose import) NEW annotation REMOVED per
# PR #764 review feedback — the term is obsolete and the function is
# already captured by the ACCEPTed GO:0046326 (positive regulation of
# D-glucose import across plasma membrane) elsewhere in this review.
- term:
    id: GO:0008610
    label: lipid biosynthetic process
  evidence_type: NAS
  review:
    summary: Added to align core_functions with existing annotations.
    action: NEW
    reason: Core function term not present in existing_annotations.
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Insulin is a potent anabolic hormone that stimulates fatty acid synthesis and triglyceride storage in adipose tissue and liver through multiple transcriptional and post-translational mechanisms. The key transcription factors mediating insulin-induced lipogenic gene expression are the sterol regulatory element binding proteins (SREBPs), particularly SREBP-1c in lipogenic tissues
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Reciprocally, insulin potently inhibits lipolysis in adipose tissue through inactivation of hormone-sensitive lipase (HSL) via a PKA-independent mechanism. Insulin-activated AKT phosphorylates and inactivates phosphodiesterase 3B (PDE3B), reducing the degradation of cAMP and preventing PKA activation
- term:
    id: GO:0045542
    label: positive regulation of cholesterol biosynthetic process
  evidence_type: NAS
  review:
    summary: Added to align core_functions with existing annotations.
    action: NEW
    reason: Core function term not present in existing_annotations.
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Insulin is a potent anabolic hormone that stimulates fatty acid synthesis and triglyceride storage in adipose tissue and liver through multiple transcriptional and post-translational mechanisms. The key transcription factors mediating insulin-induced lipogenic gene expression are the sterol regulatory element binding proteins (SREBPs), particularly SREBP-1c in lipogenic tissues
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Reciprocally, insulin potently inhibits lipolysis in adipose tissue through inactivation of hormone-sensitive lipase (HSL) via a PKA-independent mechanism. Insulin-activated AKT phosphorylates and inactivates phosphodiesterase 3B (PDE3B), reducing the degradation of cAMP and preventing PKA activation
- term:
    id: GO:0010906
    label: regulation of glucose metabolic process
  evidence_type: NAS
  review:
    summary: Added to align core_functions with existing annotations.
    action: NEW
    reason: Core function term not present in existing_annotations.
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Insulin is a potent anabolic hormone that stimulates fatty acid synthesis and triglyceride storage in adipose tissue and liver through multiple transcriptional and post-translational mechanisms. The key transcription factors mediating insulin-induced lipogenic gene expression are the sterol regulatory element binding proteins (SREBPs), particularly SREBP-1c in lipogenic tissues
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Reciprocally, insulin potently inhibits lipolysis in adipose tissue through inactivation of hormone-sensitive lipase (HSL) via a PKA-independent mechanism. Insulin-activated AKT phosphorylates and inactivates phosphodiesterase 3B (PDE3B), reducing the degradation of cAMP and preventing PKA activation
- term:
    id: GO:0045727
    label: positive regulation of translation
  evidence_type: NAS
  review:
    summary: |
      Insulin does not perform translation itself — it positively regulates
      translation in target cells via the mTOR/S6K1/4E-BP1 axis. Per PR
      #764 review feedback, the previously proposed NEW GO:0006412
      (translation) term has been replaced with GO:0045727 (positive
      regulation of translation), which correctly captures insulin's
      regulatory role.
    action: NEW
    reason: Insulin signaling positively regulates translation in target
      tissues; the protein itself does not perform translation.
    supported_by:
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Insulin is also a powerful regulator of protein turnover, stimulating protein synthesis while simultaneously inhibiting protein degradation, thereby promoting net protein anabolism. Insulin stimulates protein synthesis through multiple mechanisms including increased cellular uptake of amino acids through upregulation of amino acid transporters, particularly for branched-chain amino acids (BCAAs) such as leucine
    - reference_id: file:human/INS/INS-deep-research-perplexity.md
      supporting_text: Following insulin stimulation and increased leucine availability, mTORC1 phosphorylates S6K1 and 4E-BP1, leading to translation initiation factor phosphorylation and enhanced translation of mRNA molecules, particularly those encoding protein synthesis machinery and growth-promoting proteins
references:
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: GO_REF:0000043
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
  findings: []
- id: GO_REF:0000117
  title: Electronic Gene Ontology annotations created by ARBA machine learning models
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: file:human/INS/INS-deep-research-perplexity.md
  title: Deep research on human insulin gene
  findings: []
- id: file:human/INS/INS-deep-research-falcon.md
  title: Falcon deep research report on human INS (Edison Scientific Literature, May 2026)
  findings:
  - statement: Preproinsulin matures via signal peptide cleavage in the ER lumen, proinsulin folding with three disulfide bonds, trafficking through Golgi/TGN, packaging into immature secretory granules, and proteolytic processing by PC1/3, PC2 and carboxypeptidase E to yield mature insulin and C-peptide.
    supporting_text: 'INS encodes preproinsulin, a single-chain precursor that enters the regulated secretory pathway. After co-translational targeting to the rough ER, the signal peptide is removed to generate proinsulin, which folds in the ER and forms three disulfide bonds. Proinsulin then traffics through the Golgi and is packaged into secretory granules, where endoproteolytic processing yields mature insulin and C-peptide.'
  - statement: Mature insulin binds the insulin receptor (INSR) and activates two main downstream branches — PI3K→AKT (metabolic) and RAS→RAF→MEK→ERK (mitogenic).
    supporting_text: 'Insulin acts mainly by binding INSR, which autophosphorylates and recruits adaptor proteins (IRS, Shc), bifurcating into: PI3K→PIP3→AKT (metabolic branch): GLUT4 translocation, glycogen synthesis regulation via GSK3, mTOR-mediated protein synthesis, and transcriptional programs (e.g., FOXO regulation). RAS→RAF→MEK→ERK (MAPK) (mitogenic branch): growth/proliferation and gene-expression programs.'
  - statement: Insulin biogenesis is coupled to β-cell ER folding capacity, redox state, ER Ca2+ homeostasis, and secretory trafficking; chronic hyperglycemia selectively suppresses translation of insulin and secretion-related mRNAs prior to global translational collapse.
    supporting_text: Its biosynthesis is tightly coupled to ER folding capacity, redox state, ER Ca2+ homeostasis, and secretory trafficking; recent 2023–2024 work clarifies how metabolism-driven redox buffering, chronic hyperglycemia-induced translational programs, and cargo condensation mechanisms can regulate or impair insulin production and secretion.
- id: file:human/INS/INS-uniprot.txt
  title: UniProt entry for human insulin
  findings: []
- id: PMID:37159024
  title: Condensation of the β-cell secretory granule luminal cargoes pro/insulin and ICA512 RESP18 homology domain.
  findings:
  - statement: Proinsulin co-condenses with ICA512 RESP18HD at pH 6.8 to form micron-scale luminal condensates, suggesting proinsulin is an early driver of insulin secretory granule biogenesis via phase separation in the early secretory pathway.
    supporting_text: proinsulin is an early driver of insulin SG biogenesis, in a process in which its co-condensation with RESP18HD participates in their phase separation from other secretory proteins in transit through the same compartments but destined to other routes.
- id: PMID:38032734
  title: Sustained hyperglycemia specifically targets translation of mRNAs for insulin secretion.
  findings:
  - statement: Chronic high glucose suppresses translation of insulin and of mRNAs required for secretory granule formation, exocytosis, and metabolism-coupled insulin secretion in β-cells, before induction of ER stress or global translational collapse.
    supporting_text: Before induction of ER stress or suppression of global translation, sustained high glucose suppressed glucose-stimulated insulin secretion and downregulated translation of not only insulin, but also mRNAs related to insulin secretory granule formation, exocytosis, and metabolism-coupled insulin secretion.
- id: PMID:38397072
  title: Changes in Cells Associated with Insulin Resistance.
  findings:
  - statement: Insulin is a polypeptide hormone synthesized and secreted by pancreatic β-cells that regulates plasma glucose, fat, ketone body, and protein metabolism.
    supporting_text: Insulin is a polypeptide hormone synthesized and secreted by pancreatic β-cells. It plays an important role as a metabolic hormone. Insulin influences the metabolism of glucose, regulating plasma glucose levels and stimulating glucose storage in organs such as the liver, muscles and adipose tissue.
- id: PMID:38507587
  title: 'The Ailing β-Cell in Diabetes: Insights From a Trip to the ER: The 2023 Outstanding Scientific Achievement Award Lecture.'
  findings:
  - statement: SERCA-regulated ER calcium dynamics are required for normal proinsulin processing and trafficking in β-cells; disruption underlies β-cell stress in diabetes pathophysiology.
    supporting_text: a role for the sarcoendoplasmic reticulum calcium ATPase (SERCA) pump in the regulation of endoplasmic reticulum (ER) calcium, protein trafficking, and proinsulin processing within the β-cell.
- id: PMID:38935435
  title: A metabolic redox relay supports ER proinsulin export in pancreatic islet β cells.
  findings:
  - statement: Glucose metabolism supplies reductive donors (NADPH, thioredoxin flux) that buffer ER redox; ER hyperoxidation delays proinsulin export and limits insulin granule formation.
    supporting_text: Hyperoxidation of the ER delays proinsulin export and limits the proinsulin supply available for insulin granule formation. In this report, we identified glucose metabolism as a critical determinant in the redox homeostasis of the ER.
- id: PMID:40052150
  title: 'Molecular puzzle of insulin: structural assembly pathways and their role in diabetes.'
  findings:
  - statement: Preproinsulin synthesis begins in pancreatic β-cells with ER translocation and signal peptide cleavage; proinsulin folds in the ER, an environment optimized to support disulfide bond formation and minimize misfolding.
    supporting_text: Proinsulin foldability is optimized in the ER, an environment evolved to support the folding process and the formation of disulfide bonds while minimizing misfolding.
- id: PMID:10508408
  title: Structural consequences of the B5 histidine --> tyrosine mutation in human insulin characterized by X-ray crystallography and conformational analysis.
  findings: []
- id: PMID:10604997
  title: Bovine and human insulin activate CD8+-autoreactive CTL expressing both type 1 and type 2 cytokines in C57BL/6 mice.
  findings: []
- id: PMID:10644978
  title: PSM, a mediator of PDGF-BB-, IGF-I-, and insulin-stimulated mitogenesis.
  findings: []
- id: PMID:11387233
  title: Insulin and glucocorticoids differentially regulate leptin transcription and secretion in brown adipocytes.
  findings: []
- id: PMID:11443198
  title: 'Insulin inhibits intranuclear nuclear factor kappaB and stimulates IkappaB in mononuclear cells in obese subjects: evidence for an anti-inflammatory effect?'
  findings: []
- id: PMID:11500939
  title: Regulation of the Akt/Glycogen synthase kinase-3 axis by insulin-like growth factor-II via activation of the human insulin receptor isoform-A.
  findings: []
- id: PMID:11742412
  title: Insulin signalling and the regulation of glucose and lipid metabolism.
  findings: []
- id: PMID:1184755
  title: Glucagon regulation of plasma ketone body concentration in human diabetes.
  findings: []
- id: PMID:12135947
  title: Insulin-dependent activation of endothelial nitric oxide synthase is impaired by O-linked glycosylation modification of signaling proteins in human coronary endothelial cells.
  findings: []
- id: PMID:12138094
  title: Insulin/insulin-like growth factor I hybrid receptors have different biological characteristics depending on the insulin receptor isoform involved.
  findings: []
- id: PMID:12881524
  title: Differential gene expression induced by insulin and insulin-like growth factor-II through the insulin receptor isoform A.
  findings: []
- id: PMID:12946932
  title: Insulin impairs endothelium-dependent vasodilation independent of insulin sensitivity or lipid profile.
  findings: []
- id: PMID:14615391
  title: Insulin stimulates glucose transport via nitric oxide/cyclic GMP pathway in human vascular smooth muscle cells.
  findings: []
- id: PMID:14739855
  title: Insulin decreases hepatic acute phase protein levels in severely burned children.
  findings: []
- id: PMID:14744991
  title: Insulin induces the release of vasodilator compounds from platelets by a nitric oxide-G kinase-VAMP-3-dependent pathway.
  findings: []
- id: PMID:14986111
  title: Impaired binding of insulin to erythrocyte membrane receptor and the activation of nitric oxide synthase by the hormone in human breast cancer.
  findings: []
- id: PMID:15185208
  title: Intravenous insulin decreases protein breakdown in infants on extracorporeal membrane oxygenation.
  findings: []
- id: PMID:15473891
  title: 'Insulin activates vascular endothelial growth factor in vascular smooth muscle cells: influence of nitric oxide and of insulin resistance.'
  findings: []
- id: PMID:15591776
  title: Insulin decreases the secretion of apoB-100 from hepatic HepG2 cells but does not decrease the secretion of apoB-48 from intestinal CaCo-2 cells.
  findings: []
- id: PMID:15792832
  title: Insulin and nitric oxide stimulates glucose transport in human placenta.
  findings: []
- id: PMID:16604263
  title: 'Neuroprotection of insulin against oxidative stress-induced apoptosis in cultured retinal neurons: involvement of phosphoinositide 3-kinase/Akt signal pathway.'
  findings: []
- id: PMID:17051221
  title: Structures of human insulin-degrading enzyme reveal a new substrate recognition mechanism.
  findings: []
- id: PMID:17472440
  title: A helical structural nucleus is the primary elongating unit of insulin amyloid fibrils.
  findings: []
- id: PMID:17925406
  title: Activation of the insulin receptor by insulin and a synthetic peptide leads to divergent metabolic and mitogenic signaling and responses.
  findings: []
- id: PMID:17957153
  title: Milk intake and feeding behavior in the first week of life and its relationship to cord blood ghrelin, leptin, and insulin concentrations.
  findings: []
- id: PMID:19188609
  title: 'Protection of synapses against Alzheimer''s-linked toxins: insulin signaling prevents the pathogenic binding of Abeta oligomers.'
  findings: []
- id: PMID:19727662
  title: Extracellular PBEF/NAMPT/visfatin activates pro-inflammatory signalling in human vascular smooth muscle cells through nicotinamide phosphoribosyltransferase activity.
  findings: []
- id: PMID:20082125
  title: In vitro degradation of insulin-like peptide 3 by insulin-degrading enzyme.
  findings: []
- id: PMID:20455999
  title: 'A novel domain of caveolin-2 that controls nuclear targeting: regulation of insulin-specific ERK activation and nuclear translocation by caveolin-2.'
  findings: []
- id: PMID:20738396
  title: Structural features of proinsulin C-peptide oligomeric and amyloid states.
  findings: []
- id: PMID:22854022
  title: SERF protein is a direct modifier of amyloid fiber assembly.
  findings: []
- id: PMID:23106816
  title: Insulin solubility transitions by pH-dependent interactions with proinsulin C-peptide.
  findings: []
- id: PMID:23302862
  title: How insulin engages its primary binding site on the insulin receptor.
  findings: []
- id: PMID:23416304
  title: 'Amino acid sequence determinants in self-assembly of insulin chiral amyloid superstructures: role of C-terminus of B-chain in association of fibrils.'
  findings: []
- id: PMID:23510797
  title: Peptides that form β-sheets on hydrophobic surfaces accelerate surface-induced insulin amyloidal aggregation.
  findings: []
- id: PMID:24675707
  title: 'Resistin in dairy cows: plasma concentrations during early lactation, expression and potential role in adipose tissue.'
  findings: []
- id: PMID:25240198
  title: Saturated fatty acid-induced miR-195 impairs insulin signaling and glycogen metabolism in HepG2 cells.
  findings: []
- id: PMID:25403480
  title: 'Glucose tolerance is associated with differential expression of microRNAs in skeletal muscle: results from studies of twins with and without type 2 diabetes.'
  findings: []
- id: PMID:29512653
  title: Structure of the insulin receptor-insulin complex by single-particle cryo-EM analysis.
  findings: []
- id: PMID:31501273
  title: MicroRNA 7 Impairs Insulin Signaling and Regulates Aβ Levels through Posttranscriptional Regulation of the Insulin Receptor Substrate 2, Insulin Receptor, Insulin-Degrading Enzyme, and Liver X Receptor Pathway.
  findings: []
- id: PMID:32296183
  title: A reference map of the human binary protein interactome.
  findings: []
- id: PMID:36250347
  title: Insulin stimulates atypical protein kinase C-mediated phosphorylation of the neuronal adaptor FE65 to potentiate neurite outgrowth by activating ARF6-Rac1 signaling.
  findings: []
- id: PMID:381941
  title: A structurally abnormal insulin causing human diabetes.
  findings: []
- id: PMID:7556975
  title: Binding of human, porcine and bovine insulin to insulin receptors from human brain, muscle and adipocytes and to expressed recombinant alternatively spliced insulin receptor isoforms.
  findings: []
- id: PMID:7688386
  title: Insulin and IGF-1 increase mitogenesis and glucose metabolism in the multiple myeloma cell line, RPMI 8226.
  findings: []
- id: PMID:8452530
  title: Purified hybrid insulin/insulin-like growth factor-I receptors bind insulin-like growth factor-I, but not insulin, with high affinity.
  findings: []
- id: PMID:8702995
  title: Akt, a pleckstrin homology domain containing kinase, is activated primarily by phosphorylation.
  findings: []
- id: PMID:8844841
  title: 'A novel complex of a phenolic derivative with insulin: structural features related to the T-->R transition.'
  findings: []
- id: PMID:9092559
  title: Insulin-induced activation of NADPH-dependent H2O2 generation in human adipocyte plasma membranes is mediated by Galphai2.
  findings: []
- id: PMID:9388210
  title: Inhibition of insulin receptor activation by insulin-like growth factor binding proteins.
  findings: []
- id: PMID:9498508
  title: Effects of insulin on wound healing.
  findings: []
- id: PMID:9667398
  title: 'Familial hyperproinsulinaemia due to a mutation substituting histidine for arginine at position 65 in proinsulin: identification of the mutation by restriction enzyme mapping.'
  findings: []
- id: PMID:9773776
  title: Megalin is an endocytic receptor for insulin.
  findings: []
- id: Reactome:R-HSA-110011
  title: Binding of Grb10 to the insulin receptor
  findings: []
- id: Reactome:R-HSA-264976
  title: Proinsulin binds zinc and calcium forming Proinsulin:zinc:calcium
  findings: []
- id: Reactome:R-HSA-264997
  title: P4HB mediates disulfide bond formation in Proinsulin
  findings: []
- id: Reactome:R-HSA-265010
  title: Proinsulin translocates from the endoplasmic reticulum to the Golgi
  findings: []
- id: Reactome:R-HSA-265153
  title: Proinsulin:Zinc:Calcium complex translocates to immature secretory granule
  findings: []
- id: Reactome:R-HSA-6807875
  title: ARFGAP, cargo, v-SNAREs and p24 proteins bind nascent COPI complex
  findings: []
- id: Reactome:R-HSA-6807877
  title: ARFGAPs stimulate ARF GTPase activity
  findings: []
- id: Reactome:R-HSA-6809003
  title: ERGIC-to-Golgi vesicles bind dynein:dynactin
  findings: []
- id: Reactome:R-HSA-6809006
  title: Vesicle is tethered through binding GOLGA2:GORASP1, GOLGB1 and the COG complex
  findings: []
- id: Reactome:R-HSA-6809010
  title: COPI vesicle uncoating
  findings: []
- id: Reactome:R-HSA-6809011
  title: cis-Golgi t-SNAREs bind YKT6 on tethered vesicle
  findings: []
- id: Reactome:R-HSA-74707
  title: Binding of IRS to insulin receptor
  findings: []
- id: Reactome:R-HSA-74711
  title: Phosphorylation of IRS
  findings: []
- id: Reactome:R-HSA-74712
  title: Dissociation of IRS-P from insulin receptor
  findings: []
- id: Reactome:R-HSA-74715
  title: Autophosphorylation of insulin receptor
  findings: []
- id: Reactome:R-HSA-74716
  title: Insulin binds the insulin receptor
  findings: []
- id: Reactome:R-HSA-74718
  title: Internalisation of the insulin receptor
  findings: []
- id: Reactome:R-HSA-74726
  title: Dissociation of insulin from insulin receptor
  findings: []
- id: Reactome:R-HSA-74730
  title: Insulin degradation
  findings: []
- id: Reactome:R-HSA-74740
  title: Binding of SHC1 to insulin receptor
  findings: []
- id: Reactome:R-HSA-74742
  title: Phosphorylation of SHC1
  findings: []
- id: Reactome:R-HSA-74743
  title: Dissociation of p-Y427-SHC1 from insulin receptor
  findings: []
- id: Reactome:R-HSA-976734
  title: Amyloid fibrils have additional components
  findings: []
- id: Reactome:R-HSA-977136
  title: Amyloid precursor proteins form ordered fibrils
  findings: []
- id: Reactome:R-NUL-9023165
  title: Pcsk1 (rat) cleaves human proinsulin to yield Insulin(25-56) and Insulin(57-110)
  findings: []
- id: Reactome:R-NUL-9023166
  title: Carboxypeptidase E (rat Carboxypeptidase H) cleaves Insulin(25-56) to yield Insulin(25-54)
  findings: []
- id: Reactome:R-NUL-9023180
  title: Pcsk2 (rat) cleaves human Insulin(57-110) to yield Insulin(90-110) and C-peptide (Insulin(57-89))
  findings: []
- id: Reactome:R-NUL-9023186
  title: Carboxypeptidase E (rat Carboxypeptidase H) cleaves C-peptide (Insulin(57-89)) to yield C-peptide (Insulin(57-87))
  findings: []
core_functions:
- description: Binds insulin receptor with high affinity to activate receptor tyrosine kinase signaling cascades regulating glucose homeostasis
  supported_by:
  - reference_id: file:human/INS/INS-deep-research-perplexity.md
    supporting_text: Insulin binding to site-1, the primary insulin-binding site, is composed of the L1 domain of one α-subunit and the αCT domain of the adjacent α-subunit; insulin binds to this site with high affinity (Kd approximately 10-30 nanomolar)
  - reference_id: file:human/INS/INS-deep-research-perplexity.md
    supporting_text: Upon binding of a single insulin molecule to site-1, the receptor undergoes a dramatic conformational transition to a Γ-shaped intermediate state, where the FnIII-2 domains move away from the L1 domain, initiating separation of the two receptor protomers. This conformational change brings the two intracellular kinase domains into closer spatial proximity, enabling trans-autophosphorylation
  - reference_id: file:human/INS/INS-deep-research-perplexity.md
    supporting_text: The phosphatidylinositol 3-kinase (PI3K) pathway represents the primary route through which insulin exerts its metabolic effects, particularly regarding glucose homeostasis, glycogen synthesis, and protein synthesis
  molecular_function:
    id: GO:0005158
    label: insulin receptor binding
  directly_involved_in:
  - id: GO:0042593
    label: glucose homeostasis
  - id: GO:0008286
    label: insulin receptor signaling pathway
  - id: GO:0051897
    label: positive regulation of phosphatidylinositol 3-kinase/protein kinase B signal transduction
  locations:
  - id: GO:0005576
    label: extracellular region
- description: Stimulates glucose uptake in muscle and adipose tissue through GLUT4 translocation via PI3K/AKT signaling
  supported_by:
  - reference_id: file:human/INS/INS-deep-research-perplexity.md
    supporting_text: The most physiologically important function of insulin is the stimulation of glucose uptake from the bloodstream into insulin-responsive tissues, particularly skeletal muscle and adipose tissue, which together account for the majority of postprandial glucose disposal. This metabolic action is mediated through the insulin-dependent translocation of glucose transporter type-4 (GLUT4) from intracellular membrane compartments to the plasma membrane
  - reference_id: file:human/INS/INS-deep-research-perplexity.md
    supporting_text: Following AKT activation, the serine/threonine kinase AS160 (also known as TBC1D4) is phosphorylated by AKT, leading to its release from GLUT4-containing storage vesicles. This phosphorylation event activates the RabGAP activity of AS160, converting Rab small GTPases to their inactive GDP-bound state and enabling GLUT4 vesicle mobilization
  molecular_function:
    id: GO:0005158
    label: insulin receptor binding
  directly_involved_in:
  - id: GO:1904659
    label: D-glucose transmembrane transport
  - id: GO:0042593
    label: glucose homeostasis
  locations:
  - id: GO:0005576
    label: extracellular region
- description: Suppresses hepatic glucose production through inhibition of gluconeogenesis and glycogenolysis via AKT-mediated FoxO1 inactivation
  supported_by:
  - reference_id: file:human/INS/INS-deep-research-perplexity.md
    supporting_text: The suppression of hepatic gluconeogenesis by insulin involves inhibition of the transcription factors CREB and FoxO1, which normally activate the expression of the rate-limiting gluconeogenic enzymes phosphoenolpyruvate carboxylase (PEPCK) and glucose-6-phosphatase. The AKT-mediated phosphorylation and inactivation of FoxO1, combined with reduced CREB activity following insulin treatment, leads to decreased expression of gluconeogenic enzymes and reduced hepatic glucose production
  - reference_id: file:human/INS/INS-deep-research-perplexity.md
    supporting_text: Insulin rapidly inhibits hepatic glycogenolysis through mechanisms involving protein phosphatase-1 (PP1), which is activated through insulin-mediated suppression of glycogen phosphorylase kinase, thereby preventing phosphorylation of glycogen phosphorylase and allowing its inactivation
  molecular_function:
    id: GO:0005158
    label: insulin receptor binding
  directly_involved_in:
  - id: GO:0042593
    label: glucose homeostasis
  - id: GO:0045721
    label: negative regulation of gluconeogenesis
  locations:
  - id: GO:0005576
    label: extracellular region
- description: Promotes lipogenesis and inhibits lipolysis in adipose tissue through SREBP-1c activation and HSL inactivation
  supported_by:
  - reference_id: file:human/INS/INS-deep-research-perplexity.md
    supporting_text: Insulin is a potent anabolic hormone that stimulates fatty acid synthesis and triglyceride storage in adipose tissue and liver through multiple transcriptional and post-translational mechanisms. The key transcription factors mediating insulin-induced lipogenic gene expression are the sterol regulatory element binding proteins (SREBPs), particularly SREBP-1c in lipogenic tissues
  - reference_id: file:human/INS/INS-deep-research-perplexity.md
    supporting_text: Reciprocally, insulin potently inhibits lipolysis in adipose tissue through inactivation of hormone-sensitive lipase (HSL) via a PKA-independent mechanism. Insulin-activated AKT phosphorylates and inactivates phosphodiesterase 3B (PDE3B), reducing the degradation of cAMP and preventing PKA activation
  molecular_function:
    id: GO:0005158
    label: insulin receptor binding
  directly_involved_in:
  - id: GO:0008610
    label: lipid biosynthetic process
  - id: GO:0045542
    label: positive regulation of cholesterol biosynthetic process
  - id: GO:0010906
    label: regulation of glucose metabolic process
  locations:
  - id: GO:0005576
    label: extracellular region
- description: Stimulates protein synthesis and inhibits protein degradation through mTORC1 activation and FoxO1 suppression
  supported_by:
  - reference_id: file:human/INS/INS-deep-research-perplexity.md
    supporting_text: Insulin is also a powerful regulator of protein turnover, stimulating protein synthesis while simultaneously inhibiting protein degradation, thereby promoting net protein anabolism. Insulin stimulates protein synthesis through multiple mechanisms including increased cellular uptake of amino acids through upregulation of amino acid transporters, particularly for branched-chain amino acids (BCAAs) such as leucine
  - reference_id: file:human/INS/INS-deep-research-perplexity.md
    supporting_text: Following insulin stimulation and increased leucine availability, mTORC1 phosphorylates S6K1 and 4E-BP1, leading to translation initiation factor phosphorylation and enhanced translation of mRNA molecules, particularly those encoding protein synthesis machinery and growth-promoting proteins
  molecular_function:
    id: GO:0005158
    label: insulin receptor binding
  directly_involved_in:
  - id: GO:0045727
    label: positive regulation of translation
  locations:
  - id: GO:0005576
    label: extracellular region