Insulin-stimulated GLUT4 glucose uptake — AKT2 inhibition of the TBC1D4/TBC1D1 Rab GAPs, RAB10 or RAB8A/RAB13 activation, motor-driven GLUT4 storage vesicle movement, cortical actin remodelling, STX4-SNAP23-VAMP2 fusion and SLC2A4 glucose transport; AKT2/TBC1D4/TBC1D1/RAB10/DENND4C/RAB8A/RAB13/KIF5B/MYO5A/MYO1C/RAC1/PAK1/STX4/SNAP23/VAMP2/STXBP3/STXBP4/SLC2A4

In fat cells and in skeletal and cardiac muscle, insulin raises glucose uptake by moving the facilitative glucose transporter GLUT4 (SLC2A4) from intracellular stores to the cell surface. In the unstimulated cell most GLUT4 sits in small GLUT4 storage vesicles (GSVs, the insulin-responsive compartment) that are retained inside the cell. Insulin receptor signalling through IRS proteins and class I PI3K activates the kinase AKT2. AKT2 phosphorylates the Rab GTPase-activating proteins TBC1D4 (AS160) and its paralogue TBC1D1, which suppresses their GAP activity toward GSV Rabs. The GTP-bound Rab that results is RAB10 in adipocytes, loaded by the exchange factor DENND4C, and RAB8A and RAB13 in muscle cells. Active Rabs, together with kinesin-1 (KIF5B) on microtubules and the myosins MYO5A (itself an AKT2 substrate) and MYO1C on cortical actin, carry GSVs to the cell periphery. In muscle, insulin also activates RAC1, which through PAK1 and the ARP2/3 complex remodels the cortical actin meshwork beneath the plasma membrane, a cycle of actin branching and cofilin-mediated severing that is needed for GLUT4 to reach the surface. GSVs then fuse with the plasma membrane through a SNARE complex of the vesicle SNARE VAMP2 with the plasma membrane SNAREs syntaxin-4 (STX4) and SNAP23, regulated by the syntaxin-4-binding proteins Munc18c (STXBP3) and Synip (STXBP4); AKT2 phosphorylation of Synip releases it from syntaxin-4. GLUT4 inserted into the plasma membrane then transports D-glucose down its gradient into the cell. Defects at several of these steps (AKT2 mutations, truncating TBC1D4 variants, reduced syntaxin-4) cause insulin resistance.

MODULE:glut4_insulin_stimulated_glucose_uptakeDRAFTCONCRETESignaling Pathwaymodules/glut4_insulin_stimulated_glucose_uptake.yaml

glucose import in response to insulin stimulusGO:0044381

PW:0000639

insulin responsive facilitative sugar transporter mediated glucose transport pathway

The module boundary follows the RGD Pathway Ontology term and its diagram. The diagram draws Akt2 negatively affecting Tbc1d4 and Stxbp4; Tbc1d4 negatively affecting its Rab targets, which positively affect Rabs at GSVs; Lnpep associated with Tbc1d4; Stx4 associated with and inhibited by Stxbp4; Limk1 negatively affecting Cfl1; Cfl1 and the Arp2/3 complex positively affecting actin cycling; Rac1 positively affecting Rac1 effectors; and Rhoq, Trip10, Gapvd1 and Rab31 as a negative-regulator branch acting on Slc2a4. The record text adds the GSV Rabs (Rab2a, 4a, 5a, 8a, 10, 11a, 13, 14), their GEFs (Dennd4 proteins, Rab3ip, Dennd1c), the kinesins and myosins, the Rac1 GEFs, and the Vamp2-Stx4-Snap23 fusion complex with Stxbp3. Derived through projects/RGD_PATHWAY_ONTOLOGY (pathways/PW_0000639.yaml).

GO:0044381

glucose import in response to insulin stimulus

The GO mapping recorded for PW:0000639 in the project's module seeds (skos:closeMatch, curated). It is the module's process concept.

gomodel:63d320cd00001536

FBXL19-mediated degradation of RAC1 (Human)

The project's best-overlap GO-CAM for PW:0000639 (overlap 2 genes, AKT1 and RAC1). It models AKT1 phosphorylation of RAC1 leading to FBXL19-mediated RAC1 degradation in cell migration and does not concern glucose uptake. Only its RAC1 GTPase activity node matches an annoton here (gene and MF), and that link is recorded on the RAC1 annoton.

gomodel:613aae0000000885

PTPRM role in glucose transport activity through inhibition of CTNND1 (Human)

Human GO-CAM in which SLC2A4 enables D-glucose transmembrane transporter activity (GO:0055056) in the plasma membrane, part of D-glucose transmembrane transport, positively regulated by the palmitoyltransferase ZDHHC7. The SLC2A4 node is linked to the transporter annoton.

PMID:12637568

Insulin-stimulated phosphorylation of a Rab GTPase-activating protein regulates GLUT4 translocation.

AKT phosphorylation of AS160 (TBC1D4) inactivates its Rab GAP function, the switch that couples insulin signalling to GLUT4 translocation.

These findings strongly indicate that insulin-stimulated phosphorylation of AS160 is required for GLUT4 translocation and that this phosphorylation signals translocation through inactivation of the Rab GAP function.

PMID:21454697

Insulin-stimulated GLUT4 protein translocation in adipocytes requires the Rab10 guanine nucleotide exchange factor Dennd4C.

The adipocyte pathway in outline, from TBC1D4 phosphorylation to GLUT4 vesicle fusion.

Insulin-elicited phosphorylation of the GTPase-activating protein TBC1D4 (AS160) suppresses its activity toward Rab10 and thereby leads to an increase in the GTP-bound form of Rab10, which in turn triggers movement of vesicles containing GLUT4 to the plasma membrane and their fusion with the membrane.

PMID:15494023

Analysis of insulin signalling by RNAi-based gene silencing.

siRNA screen in adipocytes: AKT2, not AKT1, is the AKT isoform that carries the signal to GLUT4, and depletion of the CAP, CrkII and Cbl components of the TC10 arm did not reduce insulin signalling to GLUT4 (boundary decisions 1 and 4).

These results show that Akt2/PKBbeta is the key downstream intermediate within the phosphoinositide 3-kinase pathway linked to insulin action on GLUT4 in cultured adipocytes

PMID:11309621

Insulin-stimulated GLUT4 translocation requires the CAP-dependent activation of TC10.

The original description of the PI3K-independent CAP-Cbl-CrkII-C3G-TC10 arm, recorded as context and as a knowledge gap rather than as a part (boundary decision 4).

The TC10 pathway functions in parallel with PI(3)K to stimulate fully GLUT4 translocation in response to insulin.

PMID:20410133

Insulin-regulated aminopeptidase is a key regulator of GLUT4 trafficking by controlling the sorting of GLUT4 from endosomes to specialized insulin-regulated vesicles.

IRAP (LNPEP) is GSV cargo that also sorts GLUT4 into GSVs in the basal state; it does not recruit AS160 to GSVs. Recorded as context, not as a part (boundary decision 3).

In sum, we show that IRAP is both cargo and a key regulator of the insulin-regulated pathway.

Derived from RGD PW:0000639 through the RGD_PATHWAY_ONTOLOGY project's diagram->module route. RGD curates 54 human genes. Modelled here (18): AKT2, TBC1D4, TBC1D1, RAB10, DENND4C, RAB8A, RAB13, KIF5B, MYO5A, MYO1C, RAC1, PAK1, the ARP2/3 complex (one family descriptor with ACTR2, ACTR3 and ARPC2 as representatives), STX4, SNAP23, VAMP2, STXBP3, STXBP4 and SLC2A4. The IR-IRS-PI3K-AKT steps are included by reference to insulin_receptor_signaling#akt_foxo_output, the AKT step of that module (PW:0000143 and PW:0000232 are mentioned here but not listed as evidence, since this module does not cover them). Molecular functions come from QuickGO experimental rows (October 2026) where they exist: SLC2A4 GO:0055056 (IDA), AKT2 and PAK1 GO:0004674 (IDA), RAB10, RAB8A, RAB13 and RAC1 GTPase activity GO:0003924 (IDA/EXP; core in the RAB8A review), DENND4C GO:0005085 (IDA), KIF5B GO:0008574 and MYO5A GO:0000146 (core in their reviews), ACTR2/ACTR3 GO:0005200 (IDA; core in the ARPC1B/ARPC4/ARPC5 reviews), SNAP23 GO:0005484 (IDA; core in the SNAP23 review), STXBP3 and STXBP4 syntaxin binding GO:0019905 (IPI). TBC1D4 and TBC1D1 GTPase activator activity GO:0005096, STX4 and VAMP2 GO:0005484 and MYO1C GO:0000146 rest on IBA rows plus the cited biochemistry, because no experimental MF row exists in human GOA. Comparator check (CLAUDE.md). QuickGO annotations to GO:0044381 in human, mouse and rat are carried only by SLC2A4, TRARG1, ZDHHC7, SLC27A1, SLC27A4 and SGCB. None of the trafficking machinery (TBC1D4, Rabs, motors, SNAREs) carries it; GO:0044381 is_a D-glucose import across plasma membrane, so it describes the transport event, which SLC2A4 performs. The term is therefore the module concept and is attached only to the SLC2A4 annoton; the other annotons carry functions, not this process. TRARG1 and ZDHHC7 (GLUT4 palmitoylation) are not on the RGD list and are left for a later revision. Boundary decisions. (1) AKT1 is excluded: AKT2 is the isoform required (PMID:15494023), and AKT2 has a direct annoton here with TBC1D4, TBC1D1, MYO5A and STXBP4 as substrates. (2) Of the eight GSV Rabs in the RGD text, RAB10 (adipocyte) and RAB8A/RAB13 (muscle) are modelled because they are the AS160 targets shown to be required for GLUT4 translocation (PMID:17403373, PMID:21041651); RAB2A and RAB14 are AS160 substrates in vitro (PMID:15971998) and RAB4A, RAB5A, RAB8B and RAB11A act in GLUT4 endosomal recycling, so they are context. DENND4C is modelled as the RAB10 GEF; DENND4A, DENND4B, RAB3IP (Rabin8) and DENND1C are other Rab GEFs named by RGD without GLUT4-specific loss-of-function data here. (3) LNPEP (IRAP) is excluded by the substrate-vs-participant rule: it is GSV cargo that co-translocates with GLUT4, and its aminopeptidase activity performs no step of insulin-stimulated glucose import; its cytoplasmic-tail role sorts GLUT4 into GSVs in the basal state (GSV biogenesis and retention), and it does not recruit AS160 (PMID:20410133). (4) The CAP (SORBS1)-CBL-CRK-RAPGEF1 (C3G)-RHOQ (TC10) arm is not a part. It was reported as a PI3K-independent requirement (PMID:11309621 but a later siRNA screen found depletion of CAP, CrkII and Cbl did not diminish insulin signalling to GLUT4 (PMID:15494023), so the arm is contested; it is recorded here and as a BIOLOGY knowledge gap. (5) The RHOQ-TRIP10-GAPVD1-RAB31 negative-regulator branch on the RGD diagram belongs to that same contested arm and is left out. (6) Cofilin (CFL1), LIMK1 and SSH1 tune actin dynamics downstream of RAC1/ARP2/3; the actin-remodelling part names RAC1, PAK1 and the ARP2/3 complex (the nucleator), with cofilin cycling described in prose. Other RGD genes not modelled: ARPC1A-5 and the remaining ACTR subunits are folded into the ARP2/3 family descriptor; BAIAP2, CYFIP1, IQGAP1, PREX1, PLEKHG4 and TIAM1 are RAC1 effectors/GEFs recorded as context; KIF3A is a second kinesin; MYO5B is a recycling myosin; SNAP23's partners are modelled, STXBP4 and STXBP3 included. (7) The fusion part follows the well-established STX4-SNAP23-VAMP2 SNARE with Munc18c (STXBP3) and Synip (STXBP4) regulation (PMID:10394363, PMID:11375421, PMID:15690082); AKT2 phosphorylation of Synip (STXBP4) on Ser99 releases it from syntaxin-4 (PMID:17336927). GO-CAM / GOA observations for upstream review. No single GO-CAM models insulin-stimulated GLUT4 translocation end to end; the project's best_gocam (gomodel:63d320cd00001536) is a RAC1 degradation model unrelated to glucose uptake, matching only on the RAC1 GTPase-activity node. TBC1D4, TBC1D1, STX4, VAMP2 and MYO1C lack experimental molecular-function rows in human GOA despite strong functional literature; these functions here rest on IBA plus the cited biochemistry. STXBP4 and STX4's only informative MF is syntaxin/SNAP-receptor binding.

9Nodes

6Parts

1Variant Sets

2Variants

19Annotons

6Connections

Derived QC

Recommended-field compliance

40.0% recommended fields populated

knowledge_gaps[0] · boundary (0/1)
knowledge_gaps[0] · status (0/1)
knowledge_gaps[0] · provenance (0/1)

Module deep research

✗ none found

No MODULE:glut4_insulin_stimulated_glucose_uptake deep-research report alongside the module YAML.

Leaf nodes lacking representative members

✓ every leaf node grounds to a representative protein.

Template conformance

✓ every declared conforms_to bundle matches its template motif.

Function consistency and core coverage

6 gene-function check(s) reflected in core functions · 0 conflict(s) · 16 evidence or coverage gap(s) (22 comparison(s))

Retained noncore functions are reported separately; they do not require promotion to core functions. Support from representative genes does not establish conservation across the whole family. Missing reviews or identifiers leave a claim unverified.

Annoton	Participant	Function	Assessment
akt2_kinase	AKT2 UniProtKB:P31751 Gene	protein serine/threonine kinase activity GO:0004674	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
tbc1d4_gap	TBC1D4 UniProtKB:O60343 Gene	GTPase activator activity GO:0005096	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
tbc1d1_gap	TBC1D1 UniProtKB:Q86TI0 Gene	GTPase activator activity GO:0005096	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
dennd4c_gef	DENND4C UniProtKB:Q5VZ89 Gene	guanyl-nucleotide exchange factor activity GO:0005085	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
rab10_gtpase	RAB10 UniProtKB:P61026 Gene	GTPase activity GO:0003924	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
rab8a_gtpase	RAB8A UniProtKB:P61006 Gene	GTPase activity GO:0003924	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
rab13_gtpase	RAB13 UniProtKB:P51153 Gene	GTPase activity GO:0003924	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
kif5b_motor	KIF5B UniProtKB:P33176 Gene	plus-end-directed microtubule motor activity GO:0008574	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
myo5a_motor	MYO5A UniProtKB:Q9Y4I1 Gene	microfilament motor activity GO:0000146	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
myo1c_motor	MYO1C UniProtKB:O00159 Gene	microfilament motor activity GO:0000146	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
rac1_gtpase	RAC1 UniProtKB:P63000 Gene	GTPase activity GO:0003924	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
pak1_kinase	PAK1 UniProtKB:Q13153 Gene	protein serine/threonine kinase activity GO:0004674	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
arp23_nucleator	ACTR2 (Arp2) UniProtKB:P61160 Family Representative	structural constituent of cytoskeleton GO:0005200	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
arp23_nucleator	ACTR3 (Arp3) UniProtKB:P61158 Family Representative	structural constituent of cytoskeleton GO:0005200	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
arp23_nucleator	ARPC2 (p34-ARC) UniProtKB:O15144 Family Representative	structural constituent of cytoskeleton GO:0005200	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
stx4_tsnare	STX4 UniProtKB:Q12846 Gene	SNAP receptor activity GO:0005484	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
snap23_tsnare	SNAP23 UniProtKB:O00161 Gene	SNAP receptor activity GO:0005484	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
vamp2_vsnare	VAMP2 UniProtKB:P63027 Gene	SNAP receptor activity GO:0005484	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
stxbp3_munc18c	STXBP3 UniProtKB:O00186 Gene	syntaxin binding GO:0019905	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
stxbp4_synip	STXBP4 UniProtKB:Q6ZWJ1 Gene	syntaxin binding GO:0019905	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
slc2a4_transporter	SLC2A4 (GLUT4) UniProtKB:P14672 Gene	D-glucose transmembrane transporter activity GO:0055056	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
arp23_nucleator	ARP2/3 actin-nucleating complex (seven subunits) Family	structural constituent of cytoskeleton GO:0005200	Family Id Missing The family has no identifier linking it to a curated family review.

Gene-review completeness (6/21 grounded genes reviewed)

4 complete review(s) · 2 with deep research · 15 missing review · 4 reviewed but lacking deep research

Gene	Review	Complete	Deep research
AKT2 P31751	✓	88/92	✗
KIF5B P33176	✓	✓	✗
MYO5A Q9Y4I1	✓	✓	✓
MYO1C O00159	✗	—	—
STXBP3 O00186	✗	—	—
ARPC2 (p34-ARC) O15144	✗	—	—
TBC1D4 (AS160) O60343	✗	—	—
SLC2A4 (GLUT4) P14672	✗	—	—
RAB13 P51153	✗	—	—
RAB10 P61026	✗	—	—
ACTR3 (Arp3) P61158	✗	—	—
ACTR2 (Arp2) P61160	✗	—	—
VAMP2 P63027	✗	—	—
STX4 Q12846	✗	—	—
PAK1 Q13153	✗	—	—
DENND4C Q5VZ89	✗	—	—
STXBP4 (Synip) Q6ZWJ1	✗	—	—
TBC1D1 Q86TI0	✗	—	—
RAB8A P61006	✓	✓	✓
RAC1 P63000	✓	✓	✗
SNAP23 O00161	✓	72/73	✗

Tree

Insulin-stimulated GLUT4 glucose uptakeSignaling Pathwayglut4_insulin_stimulated_glucose_uptake

Parts
1. 1. Upstream insulin receptor, PI3K and AKT2 activation
2. AKT2 activation downstream of the insulin receptor and PI3K (by reference)insulin_akt2_activation
3. 2. AKT2 phosphorylation of the RabGAPs TBC1D4/TBC1D1 relieving GSV Rabs
4. AKT2 inactivation of TBC1D4/TBC1D1 and activation of RAB10 or RAB8A/RAB13Regulatory Steprabgap_rab_activation
  
  Annotons
  - AKT2 protein serine/threonine kinase activity Gene Product: AKT2
  - TBC1D4 (AS160) Rab GTPase-activating protein activity Gene Product: TBC1D4
  - TBC1D1 Rab GTPase-activating protein activity Gene Product: TBC1D1
  - DENND4C RAB10 guanine nucleotide exchange factor activity Gene Product: DENND4C
  Variants
  1. GSV Rab activated downstream of the RabGAPs by cell type (One Or More)
    
    RAB10 (adipocyte)Regulatory Steprab10_adipocyte
    
    Annotons
    
    RAB10 GTPase activity Gene Product: RAB10
    
    RAB8A and RAB13 (muscle)Regulatory Steprab8a_rab13_muscle
    
    Annotons
    
    RAB8A GTPase activity Gene Product: RAB8A
    
    RAB13 GTPase activity Gene Product: RAB13
5. 3. GLUT4 storage-vesicle movement along microtubules and actin
6. Motor-driven GLUT4 storage vesicle movement (KIF5B, MYO5A, MYO1C)Regulatory Stepgsv_movement
  
  Annotons
  - KIF5B microtubule motor activity Gene Product: KIF5B
  - MYO5A actin motor activity Gene Product: MYO5A
  - MYO1C actin motor activity Gene Product: MYO1C
7. 4. Muscle cortical actin remodelling (RAC1, PAK1, ARP2/3) optional
8. RAC1-PAK1-ARP2/3 cortical actin remodellingRegulatory Stepcortical_actin_remodelling
  
  Annotons
  - RAC1 GTPase activity Gene Product: RAC1
  - PAK1 protein serine/threonine kinase activity Gene Product: PAK1
  - ARP2/3 complex actin nucleation Family: ARP2/3 actin-nucleating complex (seven subunits)
9. 5. GLUT4 storage-vesicle docking and fusion at the plasma membrane
10. STX4-SNAP23-VAMP2 SNARE fusion with STXBP3/STXBP4 regulationRegulatory Stepsnare_fusion
  
  Annotons
  - STX4 SNAP receptor activity Gene Product: STX4
  - SNAP23 SNAP receptor activity Gene Product: SNAP23
  - VAMP2 SNAP receptor activity Gene Product: VAMP2
  - STXBP3 (Munc18c) syntaxin binding Gene Product: STXBP3
  - STXBP4 (Synip) syntaxin binding Gene Product: STXBP4
11. 6. GLUT4 glucose transport at the plasma membrane
12. SLC2A4 (GLUT4) D-glucose transmembrane transportTransport Stepglucose_transport
  
  Annotons
  - SLC2A4 D-glucose transmembrane transporter activity Gene Product: SLC2A4 (GLUT4)

Details

Context

Homo sapiensNCBITaxon:9606

insulin-responsive compartment (GLUT4 storage vesicle)GO:0032593 plasma membraneGO:0005886 cytosolGO:0005829

Insulin-stimulated GLUT4 glucose uptakeSignaling Pathwayglut4_insulin_stimulated_glucose_uptake

glucose import in response to insulin stimulusGO:0044381

Context

Homo sapiensNCBITaxon:9606

insulin-responsive compartment (GLUT4 storage vesicle)GO:0032593 plasma membraneGO:0005886 cytosolGO:0005829

Connections

insulin_akt2_activation -> rabgap_rab_activation Causes

Activated AKT2 phosphorylates and inactivates the TBC1D4/TBC1D1 Rab GAPs.

rabgap_rab_activation -> gsv_movement Positively Regulates

GTP-loaded GSV Rabs recruit the cytoskeletal motors that move GLUT4 vesicles.

insulin_akt2_activation -> cortical_actin_remodelling Positively Regulates

In muscle, insulin signalling (through RAC1, parallel to the AKT2-RabGAP axis) drives cortical actin remodelling needed for GLUT4 delivery.

gsv_movement -> snare_fusion Provides Input For

Motors deliver GSVs to the cell periphery, where they dock and fuse.

cortical_actin_remodelling -> snare_fusion Positively Regulates

Remodelled cortical actin supports GSV delivery and fusion at the muscle cell surface.

snare_fusion -> glucose_transport Provides Input For

SNARE fusion inserts GLUT4 into the plasma membrane, enabling glucose transport.

Part 1: Upstream insulin receptor, PI3K and AKT2 activation

AKT2 activation downstream of the insulin receptor and PI3K (by reference)insulin_akt2_activation

Insulin binding to the insulin receptor, IRS phosphorylation, class I PI3K recruitment and AKT activation, included by reference to the AKT output step of the insulin receptor signaling module. In this pathway the required AKT isoform is AKT2 (PMID:15494023); its targets relevant here (TBC1D4, TBC1D1, Synip/STXBP4, MYO5A) are modelled in the steps below.

Realized by module insulin_receptor_signaling#akt_foxo_output

PMID:15494023

AKT2, not AKT1, is the PI3K-pathway intermediate that signals to GLUT4 in adipocytes.

loss of Akt2/PKBbeta significantly attenuated GLUT4 regulation by insulin

Part 2: AKT2 phosphorylation of the RabGAPs TBC1D4/TBC1D1 relieving GSV Rabs

AKT2 inactivation of TBC1D4/TBC1D1 and activation of RAB10 or RAB8A/RAB13Regulatory Steprabgap_rab_activation

AKT2 phosphorylates the Rab GTPase-activating proteins TBC1D4 (AS160) and TBC1D1, suppressing their GAP activity toward GSV Rabs. The de-repressed Rab is loaded with GTP and triggers GLUT4 vesicle movement. Which Rab depends on cell type: RAB10 in adipocytes (GEF DENND4C) and RAB8A with RAB13 in muscle.

Annotons

AKT2 protein serine/threonine kinase activity

akt2_kinase

Participant: Gene Product: AKT2

Gene Product:

AKT2UniProtKB:P31751

Function

protein serine/threonine kinase activityGO:0004674

Targets: TBC1D4 (AS160)UniProtKB:O60343 TBC1D1UniProtKB:Q86TI0 STXBP4 (Synip)UniProtKB:Q6ZWJ1 MYO5AUniProtKB:Q9Y4I1

Locations

cytosolGO:0005829

The insulin-activated AKT isoform required for GLUT4 translocation; phosphorylates the RabGAPs and Synip to drive and de-repress the trafficking machinery.

PMID:12637568

AKT phosphorylation of AS160 (TBC1D4) is required for GLUT4 translocation and works by inactivating its Rab GAP function.

insulin-stimulated phosphorylation of AS160 is required for GLUT4 translocation and that this phosphorylation signals translocation through inactivation of the Rab GAP function

TBC1D4 (AS160) Rab GTPase-activating protein activity

tbc1d4_gap

Participant: Gene Product: TBC1D4

Gene Product:

TBC1D4UniProtKB:O60343

Function

GTPase activator activityGO:0005096

Targets: RAB10UniProtKB:P61026 RAB8AUniProtKB:P61006

Locations

cytosolGO:0005829

Rab GAP whose AKT2 phosphorylation switches off its activity toward GSV Rabs; the brake on basal GLUT4 retention. Its GAP domain is active against Rabs 2A, 8A, 10 and 14.

PMID:15971998

The AS160 GAP domain is active against Rab2A, Rab8A, Rab10 and Rab14, which are present in GLUT4 vesicles.

The GAP domain was active against Rabs 2A, 8A, 10 and 14.

TBC1D1 Rab GTPase-activating protein activity

tbc1d1_gap

Participant: Gene Product: TBC1D1

Gene Product:

TBC1D1UniProtKB:Q86TI0

Function

GTPase activator activityGO:0005096

Locations

cytosolGO:0005829

TBC1D4 paralogue with the same Rab specificity; the predominant RabGAP in skeletal muscle, also an Akt substrate. Its R125W variant affects obesity susceptibility.

PMID:17274760

TBC1D1 has the same Rab specificity as AS160, is phosphorylated by insulin on a conserved Akt site, and its GAP activity controls GLUT4 translocation.

the Rab specificity of the Tbc1d1 GAP domain is identical with that of AS160

DENND4C RAB10 guanine nucleotide exchange factor activity

dennd4c_gef

Participant: Gene Product: DENND4C

Gene Product:

DENND4CUniProtKB:Q5VZ89

Function

guanyl-nucleotide exchange factor activityGO:0005085

Targets: RAB10UniProtKB:P61026

Locations

insulin-responsive compartment (GLUT4 storage vesicle)GO:0032593

The RAB10 GEF required for GLUT4 translocation in adipocytes; loads RAB10 with GTP once TBC1D4 is switched off. Found on isolated GLUT4 vesicles.

PMID:21454697

Dennd4C is the primary RAB10 GEF required for GLUT4 translocation in adipocytes.

The present study identifies Dennd4C, a recently described GEF for Rab10, as the primary GEF required for GLUT4 translocation.

Variant set: GSV Rab activated downstream of the RabGAPs by cell type (One Or More)

RAB10 is the required AS160 target in adipocytes; RAB8A and RAB13 are the required targets in muscle cells (RAB8A acting before RAB13). All are closely related Rab8 subfamily GTPases and AS160/TBC1D1 GAP substrates.

RAB10 (adipocyte)Regulatory Steprab10_adipocyte

Annotons

RAB10 GTPase activity

rab10_gtpase

Participant: Gene Product: RAB10

Gene Product:

RAB10UniProtKB:P61026

Function

GTPase activityGO:0003924

Locations

insulin-responsive compartment (GLUT4 storage vesicle)GO:0032593

The GTP-loaded GSV Rab that triggers GLUT4 vesicle movement and fusion in adipocytes; downstream target of AS160.

PMID:17403373

Rab10 is a downstream target of AS160 required for insulin-stimulated GLUT4 translocation in adipocytes.

Rab10 functions as a downstream target of AS160 in the insulin-signaling pathway that regulates GLUT4 translocation in adipocytes

RAB8A and RAB13 (muscle)Regulatory Steprab8a_rab13_muscle

Annotons

RAB8A GTPase activity

rab8a_gtpase

Participant: Gene Product: RAB8A

Gene Product:

RAB8AUniProtKB:P61006

Function

GTPase activityGO:0003924

Locations

cytosolGO:0005829

Insulin-activated GSV Rab in muscle, acting before RAB13.

PMID:21041651

Insulin activates Rab8A (and Rab13) and both regulate GLUT4 translocation in muscle cells, downstream of AS160.

insulin promotes GTP loading of Rab13 and Rab8A but not Rab10 in rat L6 muscle cells, Rab8A activation preceding that of Rab13

RAB13 GTPase activity

rab13_gtpase

Participant: Gene Product: RAB13

Gene Product:

RAB13UniProtKB:P51153

Function

GTPase activityGO:0003924

Locations

cell peripheryGO:0071944

Insulin-activated GSV Rab in muscle; its knockdown blocks the insulin-induced increase of surface GLUT4, rescued by RAB13 but not RAB8A.

PMID:21041651

Rab13 knockdown blocks the insulin-induced increase of surface GLUT4 in muscle cells.

cell peripheryGO:0071944

Myosin present on GLUT4 vesicles that functions in a PI3K-independent pathway moving GLUT4 vesicles to the plasma membrane; dominant-negative cargo domain blocks translocation.

PMID:12490950

Myo1c functions in a PI3K-independent insulin pathway controlling movement of GLUT4 vesicles to the plasma membrane.

myosin Myo1c functions in a PI(3)K-independent insulin signalling pathway that controls the movement of intracellular GLUT4-containing vesicles to the plasma membrane

Part 4: Muscle cortical actin remodelling (RAC1, PAK1, ARP2/3) (optional)

RAC1-PAK1-ARP2/3 cortical actin remodellingRegulatory Stepcortical_actin_remodelling

In muscle, insulin activates RAC1, which through PAK1 and the ARP2/3 actin-branching complex remodels the cortical actin meshwork beneath the plasma membrane. A dynamic cycle of ARP2/3-driven branching and cofilin (CFL1)-mediated severing — cofilin being dephosphorylated by slingshot (SSH1) and rephosphorylated by LIMK1 — is required for GLUT4 to reach the cell surface. Optional because this cortical-actin arm is prominent in muscle and dispensable for the core RabGAP-Rab-SNARE axis in adipocytes.

Annotons

RAC1 GTPase activity

rac1_gtpase

Participant: Gene Product: RAC1

Gene Product:

RAC1UniProtKB:P63000

Function

GTPase activityGO:0003924

Locations

cell peripheryGO:0071944

Insulin-activated Rho GTPase required for insulin-stimulated glucose uptake in skeletal muscle; dysregulated in insulin-resistant muscle.

PMID:23423567

Rac1 is required for insulin-stimulated glucose uptake in mouse and human skeletal muscle and is dysregulated in insulin resistance.

Rac1 is a regulator of insulin-stimulated glucose uptake and a novel candidate involved in skeletal muscle insulin resistance

PAK1 protein serine/threonine kinase activity

pak1_kinase

Participant: Gene Product: PAK1

Gene Product:

PAK1UniProtKB:Q13153

Function

protein serine/threonine kinase activityGO:0004674

Locations

cell peripheryGO:0071944

RAC1 effector kinase; insulin-stimulated PAK1 (Thr423) phosphorylation is reduced in insulin-resistant muscle, linking RAC1 to cortical actin remodelling.

PMID:23423567

PAK is a downstream target of Rac1 whose insulin-stimulated activation is reduced in insulin-resistant muscle.

insulin-stimulated PAK activation was decreased in both acute insulin-resistant (intralipid infusion) and chronic insulin-resistant states (obesity and diabetes)

ARP2/3 complex actin nucleation

arp23_nucleator

Participant: Family: ARP2/3 actin-nucleating complex (seven subunits)

Family:

ARP2/3 actin-nucleating complex (seven subunits)

Representative Members: ACTR2 (Arp2)UniProtKB:P61160 ACTR3 (Arp3)UniProtKB:P61158 ARPC2 (p34-ARC)UniProtKB:O15144

Function

structural constituent of cytoskeletonGO:0005200

Locations

cell peripheryGO:0071944

The actin-branching nucleator downstream of Rac1; silencing Arp3 or the p34 subunit abrogates insulin-induced cortical actin remodelling and impairs GLUT4 translocation.

PMID:20739464

Arp2/3, downstream of Rac, drives cortical actin polymerization required for GLUT4 translocation to the muscle cell surface.

plasma membraneGO:0005886

Syntaxin-4-binding protein (Synip) that restrains fusion in the basal state; AKT2 phosphorylation on Ser99 triggers its dissociation from syntaxin-4 to permit GLUT4 translocation.

PMID:17336927

Synip Ser99 phosphorylation (an Akt2 site) is required for insulin-stimulated syntaxin-4 dissociation and GLUT4 translocation.

Synip serine 99 phosphorylation required for insulin-stimulated Glut4 translocation

Part 6: GLUT4 glucose transport at the plasma membrane

SLC2A4 (GLUT4) D-glucose transmembrane transportTransport Stepglucose_transport

GLUT4 (SLC2A4) inserted into the plasma membrane transports D-glucose down its concentration gradient into the cell, the end step that produces insulin-stimulated glucose uptake.

Annotons

SLC2A4 D-glucose transmembrane transporter activity

slc2a4_transporter

Participant: Gene Product: SLC2A4 (GLUT4)

Gene Product:

SLC2A4 (GLUT4)UniProtKB:P14672

Function

D-glucose transmembrane transporter activityGO:0055056

Processes

glucose import in response to insulin stimulusGO:0044381

Locations

plasma membraneGO:0005886

The insulin-responsive facilitative glucose transporter whose arrival at the plasma membrane raises glucose uptake.

PMID:25004245

GLUT4 transports glucose; its cell-surface amount sets the rate of glucose uptake in human adipocytes.

regulation of cellular trafficking of the glucose transporter 4 (GLUT4)