SOCS3 (Suppressor of cytokine signaling 3; also CIS-3, SSI-3) is a 225-residue cytoplasmic adaptor protein and a cytokine-inducible negative-feedback inhibitor of JAK-STAT signaling. It has a modular architecture comprising an N-terminal kinase inhibitory region (KIR, ~residues 22-33), an extended SH2 subdomain (ESS), a central SH2 domain (~residues 46-142), and a C-terminal SOCS box (~residues 177-224). Through its SH2 domain SOCS3 docks onto specific phosphotyrosine motifs on activated cytokine receptors, most notably gp130/IL6ST, but also LIFR, EPOR, the leptin receptor (LEPR), IL12RB2, CSF3R/G-CSF receptor and the insulin/IGF-I receptors, and onto activated JAK2. The KIR then acts as a pseudosubstrate that occupies the JAK catalytic groove and inhibits JAK kinase activity, blocking downstream STAT (especially STAT3) phosphorylation. Through its SOCS box SOCS3 recruits the Elongin B/C-Cullin5-RBX2 (ECS) module, functioning as the substrate-recognition subunit of a Cullin5-RING E3 ubiquitin ligase that targets bound receptor/JAK components for ubiquitination and proteasomal degradation. SOCS3 is transcriptionally induced by STAT3 (and other cytokine signals), establishing a classical negative-feedback loop. It is a principal physiological brake on IL-6 and leptin signaling and modulates erythropoiesis, immune and inflammatory responses (including Th17 biology), and metabolic signaling.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0046426 negative regulation of receptor signaling pathway via JAK-STAT | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic (IBA) annotation to the defining SOCS3 process - negative feedback inhibition of JAK-STAT signaling. This is the central, well-supported biological role of SOCS3 and matches experimental (IMP) and ISS evidence. Reason: Core function of SOCS3; concordant with experimental and orthology evidence across the SOCS family. |
| GO:0005126 cytokine receptor binding | IBA GO_REF:0000033 | ACCEPT | Summary: SOCS3 SH2 domain docks onto phosphotyrosine motifs of activated cytokine receptors (gp130/IL6ST, LIFR, EPOR, LEPR, IL12RB2, CSF3R). Cytokine receptor binding captures this receptor-docking molecular function. Reason: Well-supported SH2-mediated receptor docking; a core molecular activity enabling SOCS3 to act at receptor complexes. |
| GO:0019221 cytokine-mediated signaling pathway | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: SOCS3 acts within cytokine-mediated signaling pathways as a feedback inhibitor. The term is correct but high-level; the negative-regulation term (GO:0046426) is the more informative process annotation. Reason: Correct but general process context; the specific negative-regulation-of-JAK-STAT term better represents the core role. |
| GO:0035556 intracellular signal transduction | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Generic InterPro-derived process annotation. SOCS3 indeed participates in intracellular signal transduction, but this is non-specific relative to its JAK-STAT negative-regulation role. Reason: Correct but uninformative high-level process; superseded by more specific JAK-STAT terms. |
| GO:0005515 protein binding | IPI PMID:19027008 The role of microtubule-associated protein 1S in SOCS3 regul... | KEEP AS NON CORE | Summary: IntAct binding annotation for the SOCS3-MAP1S interaction. 'Protein binding' is uninformative as a molecular function; the specific partner (MAP1S) is captured in the reference findings. Reason: Per curation guidelines, generic GO:0005515 'protein binding' is not a core informative MF; valid interaction evidence but kept non-core. |
| GO:0005515 protein binding | IPI PMID:24728074 Enhanced prediction of Src homology 2 (SH2) domain binding p... | KEEP AS NON CORE | Summary: SH2-domain interactome screen reporting SOCS3 binding to phosphopeptides (e.g., KIT, MET). Generic 'protein binding' molecular function. Reason: Generic protein-binding from a high-throughput SH2 screen; not a core informative MF. |
| GO:0005515 protein binding | IPI PMID:25203322 PKD1 phosphorylation-dependent degradation of SNAIL by SCF-F... | KEEP AS NON CORE | Summary: SOCS3-SNAI1 interaction reported in an EMT study focused on FBXO11/SNAIL. Generic 'protein binding' annotation. Reason: Generic protein-binding; not a core informative MF for SOCS3. |
| GO:0005515 protein binding | IPI PMID:25416956 A proteome-scale map of the human interactome network. | KEEP AS NON CORE | Summary: Interactions from a proteome-scale binary interactome map (e.g., YES1, KIAA1958). Generic 'protein binding'. Reason: High-throughput Y2H protein-binding; not a core informative MF. |
| GO:0005515 protein binding | IPI PMID:32296183 A reference map of the human binary protein interactome. | KEEP AS NON CORE | Summary: Interactions from the reference human binary interactome map (e.g., YES1, TXK, BLK). Generic 'protein binding'. Reason: High-throughput Y2H protein-binding; not a core informative MF. |
| GO:0001784 phosphotyrosine residue binding | IEA GO_REF:0000107 | ACCEPT | Summary: SOCS3 SH2 domain recognizes phosphotyrosine motifs on activated receptors and JAK2; phosphotyrosine residue binding is a precise, mechanistically grounded molecular function for the SH2 module. Reason: Accurate and informative MF capturing SH2-mediated pTyr recognition; a core docking activity. |
| GO:0035198 miRNA binding | IEA GO_REF:0000107 | MARK AS OVER ANNOTATED | Summary: Ortholog-transferred (Ensembl Compara, from mouse O35718) miRNA-binding annotation. SOCS3 is not an established RNA/miRNA-binding protein; rather it is itself a target of miRNAs (e.g., miR-221). This appears to be an erroneous electronic transfer. Reason: No credible evidence SOCS3 binds miRNA; likely spurious ortholog transfer, possibly confusing SOCS3-as-miRNA-target with miRNA binding. |
| GO:0097398 cellular response to interleukin-17 | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: Ortholog-transferred process annotation. SOCS3 is plausibly involved in IL-17-related inflammatory responses, but the link is indirect and not central to its molecular function. Reason: Plausible but indirect process from electronic transfer; not a core function. |
| GO:0016567 protein ubiquitination | IEA GO_REF:0000041 | ACCEPT | Summary: SOCS3 is the substrate-recognition subunit of an Elongin BC-Cullin5-RBX2 (ECS) E3 ubiquitin ligase via its SOCS box, mediating ubiquitination of bound receptor/JAK components. Protein ubiquitination is a correct and core process. Reason: Core SOCS-box-mediated function; concordant with mechanistic literature (Kamura et al. 2004) and Reactome CSF3R/CRL5 ubiquitination events. |
| GO:0007259 cell surface receptor signaling pathway via JAK-STAT | ISS GO_REF:0000024 | KEEP AS NON CORE | Summary: ISS (from mouse ortholog) placing SOCS3 in JAK-STAT signaling. SOCS3's role is specifically negative regulation of this pathway; the parent 'involved_in JAK-STAT' is correct but less informative than GO:0046426. Reason: Correct pathway context but the negative-regulation term is the core, more informative annotation. |
| GO:0019210 kinase inhibitor activity | ISS GO_REF:0000024 | MODIFY | Summary: SOCS3 inhibits JAK tyrosine kinase activity via its KIR (pseudosubstrate) and SH2 domain. Kinase inhibitor activity is correct; the more specific child term protein kinase inhibitor activity (GO:0004860) is preferred and is independently annotated (IDA/TAS). Reason: Generalize to the more specific, experimentally supported protein kinase inhibitor activity. Proposed replacements: protein kinase inhibitor activity |
| GO:0007259 cell surface receptor signaling pathway via JAK-STAT | ISS PMID:12754505 SOCS3 negatively regulates IL-6 signaling in vivo. | KEEP AS NON CORE | Summary: ISS from mouse Socs3, supported by in vivo evidence that Socs3 loss prolongs IL-6-induced STAT activation. Correct pathway context but less informative than the negative-regulation term. Reason: Correct but general; negative-regulation-of-JAK-STAT is the core annotation. |
| GO:0019210 kinase inhibitor activity | ISS PMID:12754505 SOCS3 negatively regulates IL-6 signaling in vivo. | MODIFY | Summary: Kinase-inhibitor MF transferred by similarity. As above, the specific protein kinase inhibitor activity term is preferred and is experimentally supported. Reason: Generalize/refine to the more specific protein kinase inhibitor activity term. Proposed replacements: protein kinase inhibitor activity |
| GO:0070102 interleukin-6-mediated signaling pathway | ISS PMID:12754505 SOCS3 negatively regulates IL-6 signaling in vivo. | ACCEPT | Summary: SOCS3 is the dominant feedback inhibitor of IL-6/gp130 signaling in vivo (Croker et al. 2003); involvement in the IL-6-mediated signaling pathway is well-supported and biologically central. Reason: Strongly supported, specific, and central to SOCS3 biology (IL-6 brake). |
| GO:0005829 cytosol | TAS Reactome:R-HSA-6785860 | KEEP AS NON CORE | Summary: SOCS3 acts in the cytosol and at the cytoplasmic face of receptor complexes. Cytosolic localization is correct but is a general location, not a core function. Reason: Correct subcellular location; one of many redundant Reactome cytosol annotations. |
| GO:0072540 T-helper 17 cell lineage commitment | TAS PMID:27893700 Trans-presentation of IL-6 by dendritic cells is required fo... | KEEP AS NON CORE | Summary: SOCS3 modulates the IL-6/STAT3 axis that drives Th17 differentiation; this is a downstream physiological/developmental consequence rather than SOCS3's molecular core function. Reason: Valid process context (IL-6/Th17 axis) but a pleiotropic, downstream role, not core. |
| GO:0004860 protein kinase inhibitor activity | IDA PMID:9727029 Interaction of human suppressor of cytokine signaling (SOCS)... | ACCEPT | Summary: Direct-assay annotation for SOCS3 protein kinase inhibitor activity. SOCS3 inhibits JAK tyrosine kinase via its KIR/SH2 modules. Although the cached abstract title names SOCS-2/IGF-IR, this is the curator-assigned experimental evidence for SOCS3 kinase-inhibitor activity and the function is correct for SOCS3. Reason: Core molecular function of SOCS3 (KIR-mediated JAK inhibition); per guidelines an experimental annotation is not removed on the basis of an abstract-only paralog title. |
| GO:0009898 cytoplasmic side of plasma membrane | IDA PMID:9727029 Interaction of human suppressor of cytokine signaling (SOCS)... | KEEP AS NON CORE | Summary: SOCS3 is recruited to phosphorylated receptor cytoplasmic tails at the inner face of the plasma membrane, consistent with this location. Accurate but a location, not a core molecular function. Reason: Correct site of action (receptor tails at the membrane); supporting location rather than core function. |
| GO:0046426 negative regulation of receptor signaling pathway via JAK-STAT | IMP PMID:25019494 MiR-221 accentuates IFNΧ³s anti-HCV effect by downregulating ... | ACCEPT | Summary: Experimental (IMP) support that modulating SOCS3 levels (via miR-221) alters JAK-STAT signaling output - downregulating SOCS3 relieves inhibition and enhances IFN/JAK/STAT signaling. Confirms SOCS3 as a negative regulator of JAK-STAT. Reason: Core function; experimentally supported negative regulation of JAK-STAT signaling. |
| GO:0005829 cytosol | TAS Reactome:R-HSA-1112755 | KEEP AS NON CORE | Summary: Reactome cytosol localization (SOCS3 binds IL6ST). Correct location annotation. Reason: Correct subcellular location; redundant with other cytosol annotations. |
| GO:0005829 cytosol | TAS Reactome:R-HSA-6790041 | KEEP AS NON CORE | Summary: Reactome cytosol localization annotation. Correct but redundant. Reason: Correct location; one of many redundant Reactome cytosol annotations. |
| GO:0005829 cytosol | TAS Reactome:R-HSA-877269 | KEEP AS NON CORE | Summary: Reactome cytosol localization (SOCS-1/SOCS-3 bind p-JAK2). Correct location. Reason: Correct location; redundant Reactome cytosol annotation. |
| GO:0005829 cytosol | TAS Reactome:R-HSA-8848110 | KEEP AS NON CORE | Summary: Reactome cytosol localization (SOCS3 binds activated PTK6). Correct location. Reason: Correct location; redundant Reactome cytosol annotation. |
| GO:0005829 cytosol | TAS Reactome:R-HSA-8848178 | KEEP AS NON CORE | Summary: Reactome cytosol localization (STAT3 stimulates SOCS3 expression). Correct location. Reason: Correct location; redundant Reactome cytosol annotation. |
| GO:0005829 cytosol | TAS Reactome:R-HSA-8952039 | KEEP AS NON CORE | Summary: Reactome cytosol localization (CRL5/neddylation pathway). Correct location. Reason: Correct location; redundant Reactome cytosol annotation. |
| GO:0005829 cytosol | TAS Reactome:R-HSA-8952044 | KEEP AS NON CORE | Summary: Reactome cytosol localization (CRL5/neddylation pathway). Correct location. Reason: Correct location; redundant Reactome cytosol annotation. |
| GO:0005829 cytosol | TAS Reactome:R-HSA-8955241 | KEEP AS NON CORE | Summary: Reactome cytosol localization (CAND1/CRL regulation). Correct location. Reason: Correct location; redundant Reactome cytosol annotation. |
| GO:0005829 cytosol | TAS Reactome:R-HSA-8955289 | KEEP AS NON CORE | Summary: Reactome cytosol localization (COMMD/CAND1/CRL regulation). Correct location. Reason: Correct location; redundant Reactome cytosol annotation. |
| GO:0005829 cytosol | TAS Reactome:R-HSA-8956040 | KEEP AS NON CORE | Summary: Reactome cytosol localization (COP9 signalosome deneddylation). Correct location. Reason: Correct location; redundant Reactome cytosol annotation. |
| GO:0005829 cytosol | TAS Reactome:R-HSA-9705738 | KEEP AS NON CORE | Summary: Reactome cytosol localization (SOCS1,3 ubiquitinates CSF3R within a CUL5/ELOB/ELOC/RNF7 complex). Correct location and consistent with SOCS3 E3-ligase function. Reason: Correct location; redundant Reactome cytosol annotation. |
| GO:0005829 cytosol | TAS Reactome:R-NUL-1169195 | KEEP AS NON CORE | Summary: Reactome cytosol localization (SOCS binding to growth hormone receptor). Correct location. Reason: Correct location; redundant Reactome cytosol annotation. |
| GO:0004860 protein kinase inhibitor activity | TAS PMID:9266833 Cloning and functional analysis of new members of STAT induc... | ACCEPT | Summary: TAS annotation for SOCS3 (SSI-3) protein kinase inhibitor activity from the SSI-2/SSI-3 cloning/functional paper. Concordant with the IDA and ISS kinase-inhibitor annotations; reflects KIR-mediated JAK inhibition. Reason: Core molecular function; corroborates the protein kinase inhibitor activity of SOCS3. |
| GO:0043066 negative regulation of apoptotic process | TAS PMID:9266833 Cloning and functional analysis of new members of STAT induc... | KEEP AS NON CORE | Summary: Based on forced SSI-3/SOCS3 expression suppressing the apoptotic effect of LIF in M1 myeloid cells. This is an indirect, downstream consequence of blocking LIF/gp130/STAT3 signaling rather than a direct anti-apoptotic molecular activity, and is context-dependent (SOCS3 can be pro- or anti-apoptotic depending on cell type). Reason: Indirect, context-dependent downstream effect of JAK-STAT inhibition; retained but not a core function. |
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Download this section (compressed HTML)Q: To what extent does SOCS3-mediated ubiquitination/proteasomal degradation of receptor complexes (via the Cul5 ECS ligase) contribute to signal termination versus the direct KIR-mediated kinase-inhibition mechanism, and are these separable in vivo?
Q: Which receptor phosphotyrosine motifs and JAK isoforms are the physiologically dominant SOCS3 targets in different tissues (liver, adipose, immune cells)?
Experiment: Separation-of-function mutants (KIR-dead vs SOCS-box-dead vs SH2-dead) expressed at endogenous levels, assayed for IL-6/gp130 STAT3 signaling kinetics and receptor/JAK ubiquitination, to dissect the relative contribution of kinase inhibition versus E3-ligase-mediated degradation.
Experiment: Quantitative proteomics (ubiquitinome/degradomics) in SOCS3-null versus reconstituted cells after IL-6/EPO/leptin stimulation to identify the physiological SOCS3 ECS-ligase substrates.
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