id: Q9V719
gene_symbol: Sin1
product_type: PROTEIN
status: IN_PROGRESS
taxon:
  id: NCBITaxon:7227
  label: Drosophila melanogaster
description: >-
  dSin1 (Stress-activated MAP kinase-interacting protein 1) is an essential, conserved subunit of
  the TOR complex 2 (TORC2) in Drosophila melanogaster. It functions as a scaffold/adapter protein
  required for TORC2 complex assembly, stability, and kinase activity. The primary molecular function
  of dSin1 within TORC2 is to facilitate the phosphorylation of AGC family kinases, particularly
  Akt/PKB at its hydrophobic motif site (S505 in Drosophila), thereby enabling downstream signaling
  for cell growth, metabolism, and survival. dSin1 contains a CRIM domain that recruits AGC kinase
  substrates and a PH-like domain that mediates membrane localization via phosphoinositide binding.
  Loss of dSin1 reduces body and organ size primarily through decreased cell number, and this
  phenotype is rescued by FoxO reduction, establishing the dSin1-TORC2-Akt-FoxO growth axis.
  Unlike mammalian Sin1, Drosophila dSin1 does not appear to mediate stress-induced JNK activation.
existing_annotations:
- term:
    id: GO:0031932
    label: TORC2 complex
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      dSin1 is a core structural component of the TORC2 complex in Drosophila. This is strongly
      supported by phylogenetic analysis (IBA) and confirmed by experimental evidence showing
      that Sin1 is required for TORC2 complex formation and integrity (PMID:17043309).
    action: ACCEPT
    reason: >-
      The annotation is well-supported. Sin1/Avo1 is an evolutionarily conserved essential
      component of TORC2 across eukaryotes. In Drosophila, knockdown of Sin1 disrupts the
      interaction between Rictor and mTOR (PMID:17043309). This represents a core function
      of the protein.
    supported_by:
      - reference_id: PMID:17043309
        supporting_text: "Sin1 is an essential component of TORC2 but not of TORC1, and functions similarly to Rictor, the defining member of TORC2, in complex formation and kinase activity."

- term:
    id: GO:0038203
    label: TORC2 signaling
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      dSin1 is required for TORC2-mediated signaling, particularly for Akt phosphorylation
      and downstream effects on growth and metabolism. This is the core biological process
      in which Sin1 functions.
    action: ACCEPT
    reason: >-
      As an essential TORC2 component, dSin1 is required for TORC2 signaling output. This
      is directly demonstrated in Drosophila where sin1 mutants show strongly reduced Akt
      hydrophobic motif phosphorylation (PMID:17369395, PMID:17043309). The IBA annotation
      is appropriate and represents a core function.
    supported_by:
      - reference_id: PMID:17369395
        supporting_text: "Mutants removing critical TORC2 components, rictor and sin1, strongly reduced AKT hydrophobic motif (HM) phosphorylation and AKT activity"
      - reference_id: PMID:17043309
        supporting_text: "Knockdown of Sin1decreases Akt phosphorylation in both Drosophila and mammalian cells and diminishes Akt function in vivo."

- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      Cytoplasmic localization is consistent with TORC2 function. The complex localizes
      to various membrane compartments and cytoplasm where it can access its substrates.
    action: ACCEPT
    reason: >-
      While a more specific localization (plasma membrane) is also annotated, cytoplasm
      is a valid broader term. TORC2 pools exist at various membrane and cytoplasmic
      locations. The IBA annotation is acceptable.
    supported_by:
      - reference_id: GO_REF:0000033
        supporting_text: "Phylogenetic inference based on ancestral reconstruction"

- term:
    id: GO:0005546
    label: phosphatidylinositol-4,5-bisphosphate binding
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      dSin1 contains a PH-like domain that mediates membrane association via phosphoinositide
      binding. This domain is conserved across the SIN1 family and is important for TORC2
      membrane recruitment and substrate access.
    action: ACCEPT
    reason: >-
      The PH domain of Sin1 family proteins is well-characterized for phosphoinositide
      binding. This binding contributes to membrane localization of TORC2 and is a direct
      molecular function. UniProt annotates a SIN1-type PH domain (aa 395-545) in dSin1.
      Deep research (Sin1-deep-research-falcon.md) confirms the PH domain mediates membrane
      interactions.
    supported_by:
      - reference_id: file:DROME/Sin1/Sin1-deep-research-falcon.md
        supporting_text: "PH domain: membrane/phosphoinositide binding; CRIM: acidic protrusion that recruits AGC substrates"

- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      TORC2 (including Sin1) localizes to the plasma membrane via PH domain-phosphoinositide
      interactions. This localization is important for accessing membrane-proximal substrates
      like Akt.
    action: ACCEPT
    reason: >-
      Plasma membrane localization of TORC2 is well-established in mammalian studies and
      is consistent with the PH domain function of Sin1. This is where TORC2 phosphorylates
      membrane-recruited Akt. Deep research confirms mTORC2/Sin1 pools exist at plasma membrane.
    supported_by:
      - reference_id: file:DROME/Sin1/Sin1-deep-research-falcon.md
        supporting_text: "mTORC2/Sin1 pools reported at plasma membrane, mitochondria-associated membranes, endosomes and vesicles"

- term:
    id: GO:0006915
    label: apoptotic process
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: >-
      This annotation derives from UniProtKB keyword mapping (Apoptosis keyword). However,
      this represents a significant SIGNALING OVER-EXTENSION. Sin1 functions in TORC2
      signaling, which activates Akt, which can phosphorylate pro-apoptotic proteins like
      Bad. This creates an indirect, multi-step connection to apoptosis regulation.
      dSin1 is NOT directly involved in apoptotic machinery - it is a TORC2 signaling
      component that is many steps removed from actual apoptosis.
    action: REMOVE
    reason: >-
      This is a classic case of pathway over-extension annotation. The chain is:
      Sin1 -> TORC2 assembly -> Akt phosphorylation -> Akt activation -> (many downstream
      targets including) -> Bad phosphorylation -> (potential) apoptosis inhibition.
      Sin1 does not directly participate in apoptotic processes. Its actual function is
      as a TORC2 subunit enabling Akt phosphorylation. The apoptosis connection is an
      indirect downstream consequence that could be 4-5 enzymatic steps removed.
      Drosophila-specific studies on dSin1 (Charette 2008 dissertation, cited in deep research)
      demonstrate that its primary phenotype is reduced growth via decreased cell number
      (Akt-FoxO axis), not altered apoptosis. Annotating Sin1 to apoptosis would be like
      annotating every upstream signaling component to every downstream phenotypic outcome.
      The TORC2 signaling annotation (GO:0038203) appropriately captures Sin1's actual
      biological role.

- term:
    id: GO:0031932
    label: TORC2 complex
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: >-
      Redundant with IBA annotation but from automated multi-method inference. Sin1 is
      unquestionably a TORC2 component.
    action: ACCEPT
    reason: >-
      Correct annotation. Duplicates are acceptable when different evidence sources
      independently support the same conclusion.
    supported_by:
      - reference_id: PMID:17043309
        supporting_text: "Sin1 is an essential component of TORC2 but not of TORC1"

- term:
    id: GO:0038203
    label: TORC2 signaling
  evidence_type: NAS
  original_reference_id: PMID:22493059
  review:
    summary: >-
      This publication (LST8 regulates cell growth via TORC2) discusses TORC2 signaling
      in Drosophila and shows that TORC2 regulates cell growth. Sin1 is referenced as
      a TORC2 component.
    action: ACCEPT
    reason: >-
      While NAS is a weaker evidence code, the annotation is correct and consistent
      with the core function of Sin1. The publication studies TORC2 function in
      Drosophila using genetic approaches.
    supported_by:
      - reference_id: PMID:22493059
        supporting_text: "we show that TORC2 regulates cell growth cell autonomously"

- term:
    id: GO:0043539
    label: protein serine/threonine kinase activator activity
  evidence_type: IMP
  original_reference_id: PMID:17369395
  review:
    summary: >-
      Sin1 functions as part of TORC2 to enable Akt phosphorylation and activation.
      As a scaffold/adapter, Sin1 contributes to kinase activation by facilitating
      substrate recognition and phosphorylation by the TOR kinase.
    action: ACCEPT
    reason: >-
      This annotation captures Sin1's molecular function well. Within TORC2, Sin1 acts
      as a substrate adapter that recognizes and binds AGC family kinases (particularly
      Akt) for phosphorylation by TOR. The CRIM domain of Sin1 is specifically implicated
      in AGC substrate recruitment. The experimental evidence from PMID:17369395 shows
      that sin1 mutants have reduced Akt phosphorylation and activity.
    supported_by:
      - reference_id: PMID:17369395
        supporting_text: "Mutants removing critical TORC2 components, rictor and sin1, strongly reduced AKT hydrophobic motif (HM) phosphorylation and AKT activity"
      - reference_id: PMID:17043309
        supporting_text: "Sin1 is required for TORC2 kinase activity in vitro"

- term:
    id: GO:0045887
    label: positive regulation of synaptic assembly at neuromuscular junction
  evidence_type: IMP
  original_reference_id: PMID:22319582
  review:
    summary: >-
      In a Drosophila tuberous sclerosis model, Rheb overexpression causes synapse
      overgrowth at neuromuscular junctions. This overgrowth was rescued by reducing
      TORC2 components (sin1, rictor) but not TORC1 components, suggesting TORC2
      promotes synapse growth.
    action: KEEP_AS_NON_CORE
    reason: >-
      While this annotation has experimental support, it represents a downstream
      phenotypic consequence of TORC2 signaling in a specific disease model context
      (tuberous sclerosis) rather than a core function of Sin1. The study shows
      that Sin1 reduction rescues Rheb-mediated synapse overgrowth, indicating
      TORC2 is required for this phenotype. However, synapse assembly regulation
      is a secondary outcome of TORC2-Akt signaling, not a direct molecular function
      of Sin1. Core functions are TORC2 complex membership and signaling.
    supported_by:
      - reference_id: PMID:22319582
        supporting_text: "Rheb-mediated synapse overgrowth was not rescued by knockdown of TorC1 signaling, however it was rescued by loss of the TorC2 components sin1 and rictor."

- term:
    id: GO:0045887
    label: positive regulation of synaptic assembly at neuromuscular junction
  evidence_type: IGI
  original_reference_id: PMID:22319582
  review:
    summary: >-
      Same annotation as above with genetic interaction evidence. The study shows
      Sin1 genetically interacts with the Rheb/TSC pathway in synapse development.
    action: KEEP_AS_NON_CORE
    reason: >-
      Valid genetic interaction evidence but represents a context-dependent developmental
      phenotype rather than core function. Mark as non-core since it is downstream of
      the primary TORC2 signaling role.
    supported_by:
      - reference_id: PMID:22319582
        supporting_text: "synapse overgrowth was only suppressed by reducing the function of Tor complex 2 (TorC2) components (Rictor, Sin1)"

- term:
    id: GO:0031932
    label: TORC2 complex
  evidence_type: IGI
  original_reference_id: PMID:17043309
  review:
    summary: >-
      Genetic interaction evidence supports Sin1 as a TORC2 component. Sin1 knockdown
      disrupts Rictor-mTOR interaction, demonstrating genetic/physical interaction
      within the complex.
    action: ACCEPT
    reason: >-
      Strong experimental evidence. The paper demonstrates that Sin1 is required for
      TORC2 complex integrity through genetic and biochemical approaches.
    supported_by:
      - reference_id: PMID:17043309
        supporting_text: "It also disrupts the interaction between Rictor and mTOR"

- term:
    id: GO:0032869
    label: cellular response to insulin stimulus
  evidence_type: IMP
  original_reference_id: PMID:17043309
  review:
    summary: >-
      TORC2/Sin1 is required for insulin-stimulated Akt phosphorylation. This is a
      well-established upstream role of TORC2 in the insulin signaling pathway.
    action: ACCEPT
    reason: >-
      This annotation is appropriate. TORC2 is activated downstream of insulin/growth
      factor signaling and is required for full Akt activation in response to insulin.
      Sin1 is essential for this response as a TORC2 component.
    supported_by:
      - reference_id: PMID:17043309
        supporting_text: "Knockdown of Sin1decreases Akt phosphorylation in both Drosophila and mammalian cells and diminishes Akt function in vivo"

- term:
    id: GO:0032869
    label: cellular response to insulin stimulus
  evidence_type: IMP
  original_reference_id: PMID:17369395
  review:
    summary: >-
      Additional experimental evidence for Sin1 role in insulin response via TORC2-Akt
      signaling in Drosophila.
    action: ACCEPT
    reason: >-
      Consistent with PMID:17043309. The Drosophila sin1 mutants show impaired Akt
      phosphorylation, which is downstream of insulin/PI3K signaling.
    supported_by:
      - reference_id: PMID:17369395
        supporting_text: "Mutants removing critical TORC2 components, rictor and sin1, strongly reduced AKT hydrophobic motif (HM) phosphorylation and AKT activity"

- term:
    id: GO:0038203
    label: TORC2 signaling
  evidence_type: IGI
  original_reference_id: PMID:17043309
  review:
    summary: >-
      Genetic evidence from Sin1 knockdown demonstrates its essential role in TORC2
      signaling pathway output.
    action: ACCEPT
    reason: >-
      Core function annotation supported by strong experimental evidence showing
      Sin1 is required for TORC2 kinase activity.
    supported_by:
      - reference_id: PMID:17043309
        supporting_text: "Sin1 is required for TORC2 kinase activity in vitro"

- term:
    id: GO:0046628
    label: positive regulation of insulin receptor signaling pathway
  evidence_type: IMP
  original_reference_id: PMID:17043309
  review:
    summary: >-
      Sin1/TORC2 positively regulates insulin signaling by enabling Akt phosphorylation,
      which is a key node in the insulin receptor signaling cascade.
    action: ACCEPT
    reason: >-
      TORC2-mediated Akt phosphorylation is an integral part of the insulin receptor
      signaling pathway. Sin1 is required for this step. The annotation appropriately
      captures this regulatory role.
    supported_by:
      - reference_id: PMID:17043309
        supporting_text: "Knockdown of Sin1decreases Akt phosphorylation in both Drosophila and mammalian cells and diminishes Akt function in vivo"

- term:
    id: GO:0046628
    label: positive regulation of insulin receptor signaling pathway
  evidence_type: IMP
  original_reference_id: PMID:17369395
  review:
    summary: >-
      Drosophila genetic evidence confirms Sin1's role in insulin pathway regulation
      through TORC2-Akt signaling.
    action: ACCEPT
    reason: >-
      Consistent evidence from Drosophila sin1 mutants showing reduced Akt activity
      and impaired insulin pathway signaling.
    supported_by:
      - reference_id: PMID:17369395
        supporting_text: "loss of TORC2 activity strongly inhibited hyperplasia caused by elevated pathway activity, as in mutants of the tumor suppressor PTEN"

- term:
    id: GO:0051897
    label: positive regulation of phosphatidylinositol 3-kinase/protein kinase B signal transduction
  evidence_type: IMP
  original_reference_id: PMID:17043309
  review:
    summary: >-
      Sin1/TORC2 is essential for Akt/PKB phosphorylation at the hydrophobic motif,
      which is required for full Akt activation downstream of PI3K signaling.
    action: ACCEPT
    reason: >-
      This is a core function of Sin1 as part of TORC2. The complex directly
      phosphorylates Akt at S473 (mammalian)/S505 (Drosophila), which is essential
      for full kinase activation.
    supported_by:
      - reference_id: PMID:17043309
        supporting_text: "Sin1 together with Rictor are key components of mTORC2 and play an essential role in Akt phosphorylation and signaling"

- term:
    id: GO:0051897
    label: positive regulation of phosphatidylinositol 3-kinase/protein kinase B signal transduction
  evidence_type: IMP
  original_reference_id: PMID:17369395
  review:
    summary: >-
      Drosophila sin1 mutants show strongly reduced Akt phosphorylation and activity,
      demonstrating Sin1's positive regulatory role in PI3K/Akt signaling.
    action: ACCEPT
    reason: >-
      Core function annotation. The Drosophila in vivo evidence clearly shows
      Sin1 is required for Akt activation.
    supported_by:
      - reference_id: PMID:17369395
        supporting_text: "Mutants removing critical TORC2 components, rictor and sin1, strongly reduced AKT hydrophobic motif (HM) phosphorylation and AKT activity, but showed only minor growth impairment"

- term:
    id: GO:0034063
    label: stress granule assembly
  evidence_type: IMP
  original_reference_id: PMID:26054799
  review:
    summary: >-
      TORC2 (including Sin1) is required for stress granule formation under heat stress
      in Drosophila. Sin1 mutants are heat sensitive and fail to properly form stress
      granules.
    action: KEEP_AS_NON_CORE
    reason: >-
      This is a validated Drosophila-specific phenotype showing TORC2 mediates the
      heat stress response through stress granule formation. However, this appears
      to be a downstream consequence of TORC2-Akt signaling rather than a direct
      molecular function of Sin1. The stress granule phenotype is mediated through
      Akt phosphorylation. Mark as non-core since it is a context-dependent (heat
      stress) phenotypic outcome rather than the primary signaling function.
    supported_by:
      - reference_id: PMID:26054799
        supporting_text: "Rictor and Sin1 homozygous mutants are heat sensitive"

- term:
    id: GO:0019901
    label: protein kinase binding
  evidence_type: ISS
  original_reference_id: GO_REF:0000024
  review:
    summary: >-
      Sin1 binds to protein kinases, particularly Akt/PKB and TOR/mTOR, as part of
      its scaffold function in TORC2. This is inferred from sequence similarity to
      characterized orthologs.
    action: MODIFY
    reason: >-
      While technically correct (Sin1 does bind protein kinases), this term is too
      vague and uninformative. A more specific term describing Sin1's adapter/scaffold
      function in presenting substrates to TOR kinase would be preferable. The
      annotation GO:0043539 (protein serine/threonine kinase activator activity)
      better captures the molecular function.
    proposed_replacement_terms:
      - id: GO:0043539
        label: protein serine/threonine kinase activator activity

- term:
    id: GO:0048813
    label: dendrite morphogenesis
  evidence_type: IMP
  original_reference_id: PMID:19875983
  review:
    summary: >-
      In Drosophila class IV dendritic arborization neurons, Sin1 and other TORC2
      components are required for dendritic tiling. Sin1 mutants show inappropriate
      overlap of dendritic fields, similar to trc mutants. TORC2 phosphorylates
      the NDR kinase Tricornered to regulate dendritic tiling.
    action: KEEP_AS_NON_CORE
    reason: >-
      This is experimentally validated in Drosophila neurons but represents a
      tissue-specific developmental outcome of TORC2-mediated Trc phosphorylation.
      The study shows TORC2 is essential for Trc phosphorylation, which then
      controls dendritic tiling. This is a downstream phenotype of TORC2 signaling
      in a specific neuronal context rather than a core molecular function.
      The core function (TORC2 signaling, kinase activator activity) is what
      enables this phenotype.
    supported_by:
      - reference_id: PMID:19875983
        supporting_text: "Sin1, Rictor, and target of rapamycin (TOR), components of the TOR complex 2 (TORC2), are required for dendritic tiling of class IV da neurons"

references:
- id: GO_REF:0000024
  title: Manual transfer of experimentally-verified manual GO annotation data to orthologs
    by curator judgment of sequence similarity
  findings: []
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings:
    - statement: IBA annotations for TORC2 complex, TORC2 signaling, cytoplasm, plasma membrane, and PIP2 binding are phylogenetically inferred from characterized SIN1 family orthologs
- id: GO_REF:0000043
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
  findings:
    - statement: The apoptosis annotation derives from UniProtKB keyword mapping but represents an over-annotation - Sin1 is not directly involved in apoptosis
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:17043309
  title: Identification of Sin1 as an essential TORC2 component required for complex
    formation and kinase activity.
  findings:
    - statement: Sin1 is essential for TORC2 complex formation, stability, and kinase activity
      supporting_text: "Sin1 is an essential component of TORC2 but not of TORC1, and functions similarly to Rictor, the defining member of TORC2, in complex formation and kinase activity"
    - statement: Sin1 knockdown reduces Akt phosphorylation in Drosophila cells and in vivo
      supporting_text: "Knockdown of Sin1decreases Akt phosphorylation in both Drosophila and mammalian cells and diminishes Akt function in vivo"
    - statement: Sin1 is required for Rictor-mTOR interaction
      supporting_text: "It also disrupts the interaction between Rictor and mTOR"
- id: PMID:17369395
  title: 'Re-evaluating AKT regulation: role of TOR complex 2 in tissue growth.'
  findings:
    - statement: Drosophila sin1 mutants show strongly reduced Akt hydrophobic motif phosphorylation
      supporting_text: "Mutants removing critical TORC2 components, rictor and sin1, strongly reduced AKT hydrophobic motif (HM) phosphorylation and AKT activity"
    - statement: Despite reduced Akt activity, sin1 mutants show only minor growth impairment under normal conditions
      supporting_text: "showed only minor growth impairment"
    - statement: TORC2 acts as a rheostat amplifying Akt signaling at high pathway activity
      supporting_text: "TORC2 acts as a rheostat to broaden the range of AKT signaling at the high end of its range"
- id: PMID:19875983
  title: The target of rapamycin complex 2 controls dendritic tiling of Drosophila
    sensory neurons through the Tricornered kinase signalling pathway.
  findings:
    - statement: Sin1, Rictor, and TOR (TORC2 components) are required for dendritic tiling in class IV da neurons
      supporting_text: "Sin1, Rictor, and target of rapamycin (TOR), components of the TOR complex 2 (TORC2), are required for dendritic tiling of class IV da neurons"
    - statement: TORC2 phosphorylates Tricornered (NDR kinase) to regulate tiling
      supporting_text: "TORC2 is essential for Trc phosphorylation"
- id: PMID:22319582
  title: Diet and energy-sensing inputs affect TorC1-mediated axon misrouting but
    not TorC2-directed synapse growth in a Drosophila model of tuberous sclerosis.
  findings:
    - statement: Rheb-mediated synapse overgrowth is rescued by loss of sin1 and rictor (TORC2) but not TORC1 components
      supporting_text: "Rheb-mediated synapse overgrowth was not rescued by knockdown of TorC1 signaling, however it was rescued by loss of the TorC2 components sin1 and rictor"
    - statement: TORC2 directs synapse growth independently of TORC1
      supporting_text: "synapse overgrowth was only suppressed by reducing the function of Tor complex 2 (TorC2) components"
- id: PMID:22493059
  title: LST8 regulates cell growth via target-of-rapamycin complex 2 (TORC2).
  findings:
    - statement: TORC2 regulates cell growth cell-autonomously in Drosophila
      supporting_text: "we show that TORC2 regulates cell growth cell autonomously"
- id: PMID:26054799
  title: TORC2 mediates the heat stress response in Drosophila by promoting the formation
    of stress granules.
  findings:
    - statement: Sin1 and Rictor mutants are heat sensitive
      supporting_text: "Rictor and Sin1 homozygous mutants are heat sensitive"
    - statement: TORC2 is required for stress granule formation under heat stress
      supporting_text: "TORC2 is specifically required for stress granule formation under heat stress"
    - statement: S505 Akt phosphorylation is absent in Sin1 mutants
      supporting_text: "S505 phosphorylation was nearly absent in Sin1 mutants"
- id: file:DROME/Sin1/Sin1-deep-research-falcon.md
  title: Deep research summary for dSin1 function and TORC2 signaling
  findings:
    - statement: Sin1 PH domain mediates membrane/phosphoinositide binding for TORC2 localization
      supporting_text: "PH domain: membrane/phosphoinositide binding; CRIM: acidic protrusion that recruits AGC substrates"
    - statement: mTORC2/Sin1 pools exist at plasma membrane and other membrane compartments
      supporting_text: "mTORC2/Sin1 pools reported at plasma membrane, mitochondria-associated membranes, endosomes and vesicles"

core_functions:
  - description: >-
      dSin1 is an essential structural subunit of the TOR complex 2 (TORC2). It is required
      for complex assembly, stability, and integrity. Without Sin1, the Rictor-mTOR interaction
      is disrupted and TORC2 cannot form properly.
    molecular_function:
      id: GO:0043539
      label: protein serine/threonine kinase activator activity
    in_complex:
      id: GO:0031932
      label: TORC2 complex
    directly_involved_in:
      - id: GO:0038203
        label: TORC2 signaling
    locations:
      - id: GO:0005886
        label: plasma membrane

  - description: >-
      Within TORC2, dSin1 functions as a substrate adapter that recognizes and binds AGC
      family kinases (particularly Akt/PKB) for phosphorylation by the TOR kinase catalytic
      subunit. The CRIM domain mediates substrate recruitment while the PH domain contributes
      to membrane localization where substrates are accessed.
    molecular_function:
      id: GO:0005546
      label: phosphatidylinositol-4,5-bisphosphate binding
    in_complex:
      id: GO:0031932
      label: TORC2 complex
    directly_involved_in:
      - id: GO:0051897
        label: positive regulation of phosphatidylinositol 3-kinase/protein kinase B signal transduction
    locations:
      - id: GO:0005886
        label: plasma membrane

proposed_new_terms: []

suggested_questions:
  - question: Does dSin1 regulate any TORC2 substrates beyond Akt in Drosophila? In mammals, TORC2 phosphorylates multiple AGC kinases including PKC and SGK family members. The extent to which dSin1/TORC2 regulates these substrates in Drosophila has not been systematically characterized.
  - question: What is the mechanism by which TORC2/Sin1 promotes stress granule assembly? PMID:26054799 shows Sin1 mutants fail to form stress granules under heat stress, but the molecular mechanism connecting TORC2-Akt signaling to stress granule formation is not fully elucidated.

suggested_experiments:
  - description: Phosphoproteomics to identify dSin1-dependent TORC2 substrates. This would systematically identify AGC kinases and other substrates regulated by dSin1-containing TORC2 in Drosophila tissues.
  - description: Structure-function analysis of dSin1 CRIM and PH domains to determine the specific contributions of each domain to substrate recognition and membrane localization in Drosophila.