{"gene":"SH2B1","run_date":"2026-06-10T07:46:31","timeline":{"discoveries":[{"year":2005,"finding":"SH2B1 (SH2-B) is an endogenous enhancer of leptin sensitivity: genetic deletion in mice severely impairs leptin-stimulated hypothalamic JAK2 activation and STAT3/IRS2 phosphorylation, resulting in hyperphagia and obesity. Overexpression of SH2-B counteracted PTP1B-mediated inhibition of leptin signaling in cultured cells.","method":"SH2-B knockout mouse model; in vitro overexpression/PTP1B competition assay; hypothalamic signaling readouts","journal":"Cell metabolism","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined cellular phenotype, replicated across multiple signaling readouts, independently corroborated by subsequent studies","pmids":["16098827"],"is_preprint":false},{"year":2004,"finding":"SH2-B promotes activation of the PI3-kinase pathway downstream of leptin by directly binding IRS1 and IRS2 (via its PH and SH2 domains) and mediating formation of a JAK2/SH2-B/IRS1(or IRS2) tertiary complex, dramatically enhancing leptin-stimulated tyrosine phosphorylation of IRS1/IRS2 and subsequent Akt activation. Deletion of SH2-B gene impaired this phosphorylation in MEFs.","method":"Co-immunoprecipitation; in vitro binding; HEK293 overexpression; MEF knockout rescue; SH2-B domain mutants","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (in vitro binding, Co-IP, KO MEF rescue, domain mutants), replicated by subsequent work","pmids":["15316008"],"is_preprint":false},{"year":2004,"finding":"SH2-B is a physiological enhancer of insulin receptor activation: systemic deletion of SH2-B impairs insulin receptor activation and signaling (IRS1/IRS2 phosphorylation, PI3K/Akt, ERK1/2) in liver, muscle, and fat. SH2-B directly enhanced autophosphorylation of insulin receptor and tyrosine phosphorylation of IRS1/IRS2 in an SH2 domain-dependent manner in cultured cells.","method":"SH2-B knockout mouse; in vitro kinase assay; cultured cell overexpression with domain mutants","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vivo KO with tissue-specific signaling readouts plus in vitro kinase assay with domain mutants","pmids":["15314154"],"is_preprint":false},{"year":2004,"finding":"JAK2 autophosphorylation on Tyr813 is the critical docking site for the SH2 domain of SH2-Bbeta; phosphorylation of Tyr813 is required for SH2-Bbeta to bind JAK2 and to enhance JAK2 activity and STAT5B activation. The homologous Tyr785 in JAK3 similarly mediates SH2-Bbeta binding and is autophosphorylated in response to IL-2.","method":"2D phosphopeptide mapping; phosphospecific antibody; JAK2 Tyr813 mutants; in vitro kinase assays; Co-IP","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — 2D phosphopeptide mapping plus mutagenesis plus functional kinase assay, all in one study","pmids":["15121872"],"is_preprint":false},{"year":2007,"finding":"SH2B1 regulates leptin/JAK2 signaling by two mechanisms: (1) constitutive binding via non-SH2 domain regions to non-phosphorylated JAK2 inhibits basal JAK2 activity; (2) leptin-stimulated phosphorylation of JAK2 Tyr813 recruits the SH2 domain of SH2B1, which then enhances JAK2 activity. Additionally, SH2B1-IRS1 interaction (independent of Tyr813) facilitates IRS1 phosphorylation by recruiting IRS1 to JAK2.","method":"Co-immunoprecipitation; JAK2 Y813F mutants; overexpression in cells; domain deletion mutants","journal":"Molecular endocrinology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal domain-mapping with multiple SH2B1 and JAK2 mutants, consistent with prior structural/biochemical data","pmids":["17565041"],"is_preprint":false},{"year":2007,"finding":"Neuron-specific expression of SH2B1beta (using transgenic rescue of SH2B1 knockout mice) is sufficient to correct metabolic disorders including leptin resistance, hyperphagia, obesity, hyperglycemia, and insulin resistance, demonstrating that neuronal SH2B1 is the critical site for whole-body energy and glucose homeostasis.","method":"Neuron-specific transgenic rescue of SH2B1 knockout mice (SH2B1TgKO); metabolic phenotyping; hypothalamic JAK2/leptin signaling readouts","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic rescue experiment in vivo with tissue-specific transgene, multiple metabolic and signaling endpoints","pmids":["17235396"],"is_preprint":false},{"year":2009,"finding":"Peripheral SH2B1 enhances insulin sensitivity by two mechanisms: (1) directly stimulating insulin receptor catalytic activity (the SH2 domain is required and sufficient); (2) binding IRS-1 and IRS-2 and protecting them from tyrosine dephosphorylation. Deletion of peripheral SH2B1 in TgKO mice markedly worsens high-fat diet-induced insulin resistance.","method":"Tissue-specific KO (TgKO) mice; in vitro insulin receptor kinase assay with purified SH2B1; in vitro dephosphorylation assay; domain deletion mutants; Co-IP","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro reconstituted kinase assay plus dephosphorylation assay plus in vivo tissue-specific KO, multiple orthogonal methods","pmids":["19542202"],"is_preprint":false},{"year":1999,"finding":"SH2-Bbeta is required for NGF-induced neuronal differentiation: it binds to TrkA in an SH2 domain-dependent manner (NGF stimulates binding; SH2-Bbeta R555E mutant cannot bind), and overexpression of SH2-Bbeta enhances NGF-induced neurite outgrowth while dominant-negative R555E blocks it. SH2-Bbeta is tyrosyl-phosphorylated in response to NGF.","method":"GST pulldown; Co-IP in PC12 cells; GFP-fusion protein overexpression; neurite outgrowth assay; dominant-negative mutant","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP plus GST pulldown plus dominant-negative and gain-of-function experiments with functional readout","pmids":["10187854"],"is_preprint":false},{"year":2001,"finding":"SH2-B and APS exist as homopentamers and/or heteropentamers in cells (independent of Trk activation), mediated by the N-terminal multimerization domain. The N-terminal multimerization domain is required for SH2-B to enhance TrkA autophosphorylation magnitude and duration following NGF, and for TrkA/SH2-B-mediated morphological differentiation of PC12 cells.","method":"Gel filtration/native PAGE (multimerization); structure-function analysis with deletion mutants; overexpression in PC12 cells; TrkA autophosphorylation assay","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — biochemical demonstration of pentameric state plus domain deletion mutants with functional readouts","pmids":["11238898"],"is_preprint":false},{"year":2005,"finding":"Human SH2-B homodimerizes via a unique N-terminal dimerization domain; dimerization brings two JAK2 molecules into proximity for transactivation. At low SH2-B levels, dimerization activates JAK2 by forming JAK2-(SH2-B)2-JAK2 heterotetramers; at high levels, kinase activation is blocked. SH2-B and APS also heterodimerize.","method":"Yeast two-hybrid; cellular transfection; in vitro binding; JAK2 kinase activity assays with varying SH2-B concentrations","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — yeast two-hybrid plus cellular co-transfection plus kinase assays; mechanistic model validated across multiple assays in one study","pmids":["15767667"],"is_preprint":false},{"year":2006,"finding":"Crystal structure (2.35 Å) of the SH2 domain of SH2-B in complex with a phosphopeptide from JAK2 pTyr813 reveals canonical SH2 domain-phosphopeptide binding with specific recognition of Glu at +1 and a hydrophobic residue at +3. Biochemical comparison shows SH2-B SH2 domain binds JAK2 preferentially (monomeric state) while APS SH2 domain has higher affinity for the insulin receptor (dimeric state).","method":"X-ray crystallography (2.35 Å); in vitro binding assays comparing SH2-B and APS SH2 domains","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with biochemical validation in a single rigorous study","pmids":["16824542"],"is_preprint":false},{"year":2006,"finding":"SH2-Bbeta binds JAK2 at multiple sites; binding to pTyr813 is essential for APS (and SH2-Bbeta) to enhance active JAK2. Binding to a pTyr813-independent site on JAK2 inhibits JAK2. SH2-Bbeta-induced increases in JAK2 activity require only the SH2 domain and only one SH2-Bbeta bound to a JAK2 dimer. Residues 809-811 in JAK2 are critical for a regulatory region required for SH2-Bbeta activation.","method":"JAK2 truncation and point mutants; in vitro kinase assays; domain deletion analysis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — extensive mutagenesis of both SH2-Bbeta and JAK2 combined with kinase activity assays","pmids":["16914724"],"is_preprint":false},{"year":2001,"finding":"SH2-Bbeta specifically activates JAK2 but not JAK1 or JAK3 when overexpressed. APS negatively regulates JAK2 and JAK1. Endogenous APS is tyrosyl-phosphorylated in response to GH and interferon-gamma. Both SH2-Bbeta and APS bind all three JAKs, but their regulatory roles on JAK activity are distinct.","method":"Overexpression in cells; JAK1/2/3 kinase activity assays; endogenous tyrosyl-phosphorylation detection; 3T3-F442A adipocytes","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple kinase isoforms tested with functional assays in a single study, no independent replication reported","pmids":["11751854"],"is_preprint":false},{"year":1999,"finding":"NGF stimulates phosphorylation of SH2-B on multiple serine/threonine residues via kinases downstream of MEK/ERK (ERK1/2 phosphorylate SH2-Bbeta on Ser96 in vitro); MEK inhibitor PD98059 dramatically reduces NGF-promoted serine/threonine phosphorylation. An intact SH2 domain (but not Ser96 alone) is required for full NGF-stimulated serine/threonine phosphorylation.","method":"In vitro kinase assay with ERK1/2; MEK inhibitor PD98059; phosphatase treatment; SH2-Bbeta point mutants (S96A, R555E)","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — in vitro kinase assay identifies Ser96 plus pharmacological and genetic validation in cells, single lab","pmids":["10473609"],"is_preprint":false},{"year":1999,"finding":"SH2-B (SH2-Bgamma isoform) interacts specifically with the insulin receptor, requiring phosphorylation of Tyr1146 in the activation loop triple-tyrosine motif of the IR kinase domain.","method":"In vitro binding with phosphopeptides and IR kinase domain; alternative splice variant characterization","journal":"Mammalian genome","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phosphorylation-site requirement mapped by in vitro binding with defined phosphopeptides, single lab","pmids":["10594240"],"is_preprint":false},{"year":2002,"finding":"SH2-Bbeta interacts with FGFR3 via its SH2 domain; two FGFR3 phosphotyrosines (Tyr724 and Tyr760) are required for optimal SH2 domain binding. SH2-Bbeta is tyrosyl-phosphorylated by activated FGFR3. Overexpression of SH2-Bbeta increases FGFR3-stimulated STAT5 phosphorylation and nuclear translocation.","method":"Yeast two-hybrid; Co-IP; FGFR3 mutants (N540K, K650E); STAT5 phosphorylation/localization assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid plus Co-IP plus functional STAT5 readout in a single study, single lab","pmids":["11827956"],"is_preprint":false},{"year":2000,"finding":"SH2-Bbeta is required for GH-induced actin reorganization (membrane ruffling and pinocytosis) in 3T3-F442A cells. SH2-Bbeta co-localizes with F-actin in GH-induced membrane ruffles. This function requires the SH2 domain and N-terminal regions but is discrete from SH2-Bbeta's role as a JAK2 kinase activator.","method":"Cell fractionation; confocal microscopy; overexpression of wild-type and mutant SH2-Bbeta; ruffling and pinocytosis assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization by confocal plus functional actin readout with multiple domain mutants, single lab","pmids":["10777618"],"is_preprint":false},{"year":2004,"finding":"SH2-Bbeta undergoes constitutive nucleocytoplasmic shuttling; a nuclear export sequence (amino acids 224-233) is required for cytoplasmic/plasma membrane access. Nuclear export-defective SH2-Bbeta (L231A/L233A) accumulates in the nucleus and loses the ability to enhance NGF-induced neurite outgrowth, without altering ERK1/2 phosphorylation, indicating cytoplasmic/plasma membrane localization is required for its pro-differentiation function.","method":"Leptomycin B nuclear export inhibitor; truncation/point mutants with NES deletion; confocal imaging of GFP-SH2-Bbeta; stable PC12 cell lines; neurite outgrowth assay","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — pharmacological plus genetic disruption of NES with functional consequence, clear localization-function link demonstrated","pmids":["15082760"],"is_preprint":false},{"year":2003,"finding":"SH2-Bbeta positively regulates NGF-mediated activation of the Akt/Forkhead pathway: PC12 cells overexpressing SH2-Bbeta show enhanced and prolonged NGF-induced Akt phosphorylation (Ser473) and activity, and increased phosphorylation of GSK-3 and FKHR/FOXO. Dominant-negative R555E blocks NGF-induced redistribution of FKHR to the cytoplasm and Akt activation.","method":"Stable PC12 cell overexpression; Akt kinase activity assay; immunolocalization of FKHR; SH2 domain mutant (R555E)","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain- and loss-of-function with functional downstream pathway readouts, single lab","pmids":["14565960"],"is_preprint":false},{"year":2007,"finding":"SH2B2beta, a novel SH2B2 isoform lacking an SH2 domain, forms heterodimers with SH2B1 and SH2B2alpha (demonstrated by GST pulldown and Co-IP). SH2B2beta markedly attenuates SH2B1-promoted JAK2 activation and IRS-1 phosphorylation by JAK2, acting as an endogenous inhibitor of SH2B1.","method":"GST fusion protein pulldown; Co-IP; JAK2 kinase activation assay; IRS-1 phosphorylation assay","journal":"Endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal pulldown and Co-IP plus functional kinase/phosphorylation readouts in a single study","pmids":["17204555"],"is_preprint":false},{"year":2010,"finding":"SH2B1 in neuronal SH2B1 deletion mice (LepR neuron-specific Sh2b1 deletion) abrogates leptin-stimulated sympathetic nerve activation and impairs BAT thermogenic programs, revealing an SH2B1/SNS/BAT/thermogenesis axis. Hypothalamic overexpression of human SH2B1 has opposite effects (increased SNS activity, thermogenesis) and protects against diet-induced obesity.","method":"LepR neuron-specific Sh2b1 KO; adeno-associated virus-mediated hypothalamic overexpression; sympathetic nerve recording; BAT thermogenesis assays; metabolic phenotyping","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — tissue-specific KO and overexpression with direct SNS recording and thermogenesis readouts","pmids":["32251290"],"is_preprint":false},{"year":2010,"finding":"The SH2 domain of neuronal SH2B1 is required for maintenance of normal body weight and glucose metabolism in vivo: SH2 domain-defective (R555E) or SH2 domain-alone (DeltaN503) transgenes fail to rescue obesity/insulin resistance in SH2B1 null mice. Neuron-specific expression of R555E in wild-type mice promotes obesity and insulin resistance (dominant negative).","method":"Neuron-specific transgenic rescue with SH2-domain mutants; metabolic phenotyping","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo domain-mutant transgenic rescue with clear dominant-negative effect, multiple mutants tested","pmids":["20484460"],"is_preprint":false},{"year":2013,"finding":"SH2B1 in pancreatic beta-cells promotes beta-cell survival and proliferation via the PI3K/Akt pathway: knockdown attenuates insulin/IGF-1-stimulated PI3K/Akt activation and increases apoptosis; pancreas-specific SH2B1 KO on HFD leads to increased beta-cell apoptosis, decreased beta-cell mass, impaired insulin secretion, and exacerbated glucose intolerance.","method":"INS-1 cell knockdown/overexpression; pancreas-specific KO mice (PKO); streptozotocin challenge; beta-cell mass/apoptosis/proliferation assays; HFD metabolic phenotyping","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 / Strong — tissue-specific KO plus in vitro gain/loss-of-function with multiple cellular endpoints","pmids":["24150605"],"is_preprint":false},{"year":2013,"finding":"SH2B1 in beta-cells promotes insulin gene expression and glucose-stimulated insulin secretion at least in part by enhancing JAK2 activation of the insulin promoter and increasing Pdx1 expression and its recruitment to the insulin promoter.","method":"INS-1 cell knockdown/overexpression; insulin promoter-luciferase assay; Pdx1 chromatin immunoprecipitation; islet insulin content measurement","journal":"Molecular endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus promoter-reporter plus gain/loss-of-function in beta-cells, single lab","pmids":["24645678"],"is_preprint":false},{"year":2012,"finding":"SH2B1beta associates with the erythropoietin receptor (EPO-R) at pTyr343 and pTyr401 via its SH2 domain (pYXXL motif), as shown by COLT screening and Co-IP. In hematopoietic cells, SH2B1beta preferentially associates with EPO-R over JAK2. Constitutive SH2B1-EPO-R association is needed for optimal SH2-dependent recruitment. In the absence of SH2B1, EPO-R downstream signaling is enhanced, indicating SH2B1 is a negative regulator of EPO signaling.","method":"COLT screening; Co-IP; in vitro mixing; domain-dependency experiments; SH2B1 knockdown with EPO signaling readouts","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — COLT plus Co-IP plus loss-of-function signaling readout in single study","pmids":["22669948"],"is_preprint":false},{"year":2007,"finding":"SH2-B promotes adipocyte differentiation by enhancing insulin/IGF-I receptor-Akt-Foxo1 signaling, leading to increased PPARgamma mRNA levels. SH2-B deficient MEFs show reduced adipogenesis and PPARgamma levels in response to insulin; this upregulation of PPARgamma is blocked by PI3K inhibition but not MEK inhibition.","method":"SH2-B KO MEFs; 3T3-L1 retroviral overexpression; adipogenesis assays; PI3K/MEK inhibitors; PPARgamma mRNA/protein measurement; Akt and FKHR/Foxo1 phosphorylation assays","journal":"Molecular endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO MEF plus overexpression in 3T3-L1 plus pharmacological pathway dissection, single lab","pmids":["17312274"],"is_preprint":false},{"year":2013,"finding":"In Drosophila, Lnk (SH2B ortholog) acts upstream of PI3K at the same level as Chico (IRS), downstream of InR. FRET analysis reveals in vivo binding among InR, Chico, and Lnk. Lnk ensures Chico plasma membrane localization (via both Chico PH domain and Lnk interaction) and recruits an intracellular InR fragment to the membrane, providing a fail-safe mechanism for IIS activation.","method":"Genetic epistasis in Drosophila; FRET analysis in vivo; membrane localization assays; double mutant analysis","journal":"Cell communication and signaling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — FRET plus genetic epistasis and membrane localization, single lab, ortholog study","pmids":["23590848"],"is_preprint":false},{"year":2009,"finding":"Drosophila Lnk (SH2B ortholog) acts in the IIS pathway downstream of InR and upstream of PI3K, in parallel to the IRS ortholog Chico. Lnk and Chico double mutants are synthetically lethal, indicating partially redundant functions. Loss of Lnk function also extends lifespan and improves stress survival via effects on both IIS and Ras/MAPK pathways.","method":"Drosophila genetic epistasis; PIP3 reporter localization; PKB phosphorylation assay; double mutant synthetic lethality","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with signaling readouts, double mutant lethality, ortholog study","pmids":["19680438"],"is_preprint":false},{"year":2008,"finding":"PSM/SH2B1 splice variants (gamma > delta > alpha > beta) directly potentiate Src tyrosine kinase catalytic activity (increasing Vmax and decreasing Km for ATP) and are Src substrates. SH2B1 and Src co-immunoprecipitate. SH2B1 domain-specific peptide mimetics (SH2 or PH domains) inhibit Src activity and Src-mediated STAT3s activation and phenotypic cell transformation.","method":"Co-IP with Src; in vitro kinase assay (Vmax/Km determination); herbimycin inhibitor; dominant-negative peptide mimetics; STAT3 phosphorylation assay; transformation assay","journal":"Journal of cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — in vitro kinase parameters plus Co-IP plus domain inhibitor experiments, single lab","pmids":["18247337"],"is_preprint":false},{"year":2013,"finding":"SH2B1 promotes beta-cell mass by preventing IRS2 ubiquitination: 4E-BP2 deletion induces translation of SH2B1, which forms a complex with IRS2 and JAK2 that prevents IRS2 ubiquitination, thereby increasing IRS2 levels, Akt signaling, and beta-cell proliferation and survival.","method":"4E-BP2 KO mice; Co-IP of SH2B1/IRS2/JAK2 complex; IRS2 ubiquitination assay; beta-cell mass/proliferation/survival assays","journal":"Diabetes","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP demonstrating ternary complex plus ubiquitination assay plus in vivo genetic model, single lab","pmids":["27217487"],"is_preprint":false},{"year":2015,"finding":"SH2B1 interacts with IRSp53 via its N-terminal proline-rich domains in hippocampal neurons. SH2B1-IRSp53 complexes co-localize at the plasma membrane and in the Triton X-100-insoluble fraction. Overexpressing both SH2B1beta and IRSp53 significantly enhances filopodium formation, neurite outgrowth, and branching.","method":"Co-IP in hippocampal neurons and 293T cells; confocal co-localization; subcellular fractionation; overexpression assays; filopodium/neurite quantification","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus fractionation plus functional filopodium/neurite readouts in neurons, single lab","pmids":["25586189"],"is_preprint":false},{"year":2013,"finding":"SH2B1 promotes BDNF-induced neurite outgrowth in PC12/TrkB cells by enhancing MEK-ERK1/2 and PI3K-AKT signaling. SH2B1beta also enhances BDNF-stimulated STAT3 phosphorylation on Ser727. The SH2 domain and tyrosine phosphorylation of SH2B1beta are required for these BDNF signaling effects.","method":"Stable PC12 (TrkB) cell overexpression; kinase inhibitor experiments; SH2 domain and phosphorylation mutants; neurite outgrowth assay; western blotting","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain/loss-of-function with domain mutants and pathway inhibitors, single lab","pmids":["24260264"],"is_preprint":false},{"year":2018,"finding":"The unique C-terminal alpha tail of SH2B1alpha inhibits SH2B1 functions (nuclear cycling, NGF-mediated neurite outgrowth, TrkA autophosphorylation, Akt and PLC-gamma phosphorylation) via TrkA-mediated phosphorylation of Tyr753 in the alpha tail. Mutation Y753F restores these functions. SH2B1alpha also inhibits SH2B1beta-mediated neurite outgrowth in a Tyr753-dependent manner.","method":"PC12 cell overexpression; TrkA co-expression; Tyr753Phe mutant analysis; Akt/PLC-gamma phosphorylation assays; neurite outgrowth quantification","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis plus functional readouts identifying isoform-specific phospho-regulation, single lab","pmids":["29229648"],"is_preprint":false},{"year":2022,"finding":"SH2B1 promotes phosphorylation of cytohesin-2 at Tyr381 in Schwann cells, which is required for cytohesin-2 Arf6 GEF activity and peripheral nervous system myelination. Schwann cell-specific loss of SH2B1 reduces cytohesin-2 Tyr381 phosphorylation and myelin thickness in sciatic nerve. PTP4A1 dephosphorylates the same site, acting antagonistically to SH2B1.","method":"Schwann cell-specific SH2B1 knockdown mice; cytohesin-2 Y381F knockin mice; Arf6 activity assay; myelin thickness measurement; HEK293T co-expression with PTP4A1","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo Schwann cell-specific KD plus knockin phospho-mutant mice plus Arf6 activity assay plus antagonistic phosphatase identification","pmids":["35077201"],"is_preprint":false},{"year":2022,"finding":"SH2B1delta is the predominant brain-specific isoform that localizes primarily to nucleoli (driven by two highly basic regions unique to delta), with some at plasma membrane/nucleus. All four SH2B1 isoforms rescue decreased neurite complexity in Sh2b1 KO neurons; SH2B1delta also increases total neurite length and BDNF-induced expression of Egr1, Arc and FosL1. Human obesity variants in SH2B1delta alter neurite branching, linking nucleolar function to neurobehavioral phenotypes.","method":"Primary hippocampal neuron KO rescue with individual isoforms; confocal localization; deletion/mutation of basic regions; BDNF-induced gene expression assay; neurite complexity quantification","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO neuron isoform rescue plus domain deletion for nucleolar targeting plus functional gene expression readouts, single lab","pmids":["35019135"],"is_preprint":false},{"year":2022,"finding":"SH2B1 promotes PLIN4 lysosomal degradation by binding to HSC70, facilitating HSC70-mediated PLIN4 recognition and lysosomal translocation, thereby suppressing lipid peroxidation and protecting against neurodegeneration in an MPTP Parkinson's disease mouse model.","method":"Co-IP (SH2B1-HSC70); Sh2b1 KO and neuron-specific Sh2b1 overexpression mice; AAV-HSC70 rescue; PLIN4 lysosomal translocation assay; lipid peroxidation measurement; behavioral assays","journal":"Redox biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus in vivo rescue experiments establishing SH2B1-HSC70-PLIN4 axis, single lab","pmids":["35390677"],"is_preprint":false},{"year":2016,"finding":"SH2B1 modulates chromatin state during myogenesis: it interacts with histone H1 and is required for removal of histone H1 from active transcription sites, enabling H3K4me3 induction and H3K9me3 reduction at IGF2 and MYOG promoters/enhancers. SH2B1 knockdown delays chromatin condensation and decreases myotube formation. SH2B1 is also required for MyoD occupancy at IGF2 and MYOG enhancer/promoter regions.","method":"SH2B1 knockdown in myoblasts; Co-IP with histone H1; chromatin immunoprecipitation (H3K4me3, H3K9me3, MyoD); myotube formation assay","journal":"Biochimica et biophysica acta. Gene regulatory mechanisms","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with histones plus ChIP-based histone modification and TF occupancy analysis in differentiation context, single lab","pmids":["28039048"],"is_preprint":false},{"year":2023,"finding":"Selective deletion of Sh2b1 in hippocampal inhibitory (but not excitatory) neurons impairs working memory, short-term object recognition, and behavioral flexibility in mice. Sh2b1 deletion in these neurons leads to aberrantly enhanced ERK signaling; pharmacological ERK inhibition reverses the behavioral impairment, placing hippocampal SH2B1 as a negative regulator of ERK in inhibitory neurons controlling fluid intelligence.","method":"Cell-type-specific Sh2b1 KO (inhibitory vs. excitatory neurons); behavioral battery; single-cell RNA/protein profiling; ERK inhibitor pharmacological rescue","journal":"Research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-type-specific KO with pharmacological rescue establishing ERK signaling mechanism, single study","pmids":["38434247"],"is_preprint":false},{"year":2019,"finding":"The PH domain of SH2B1 is crucial for energy balance: a two-amino acid deletion (ΔPR, residues 317-318) in the PH domain causes obesity and insulin resistance beyond that attributable to adiposity in mice. A human variant P322S/+ causes late-onset glucose intolerance. The PH domain is thus required for full SH2B1 metabolic function in vivo.","method":"SH2B1 PH domain knockin mouse models (P322S, ΔPR); metabolic phenotyping; glucose/insulin tolerance tests","journal":"Diabetes","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo knockin mouse models with PH domain mutations and detailed metabolic phenotyping, single lab","pmids":["31439647"],"is_preprint":false},{"year":2017,"finding":"The SH2 domain of SH2B1 recognizes diverse phosphopeptides (from JAK2 pTyr813, insulin receptor, IRS-1/2) with distinct thermodynamic signatures. Key residues K575 and R578 play distinct roles in binding chemically disparate ligands (+3 hydrophobic vs. +1 acidic). High-resolution structure of the SH2B1 SH2 domain reveals conformationally plastic loops enabling recognition of dissimilar ligands.","method":"X-ray crystallography (high-resolution); isothermal titration calorimetry; site-directed mutagenesis of SH2 domain residues","journal":"Proteins","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure plus thermodynamic binding measurements plus mutagenesis in one study","pmids":["29127727"],"is_preprint":false},{"year":2020,"finding":"Deletion of brain-specific SH2B1alpha and SH2B1delta isoforms (αδKO mice) decreases food intake and protects from weight gain on standard and high-fat diets, with adiposity-dependent improvement in glucose homeostasis. This lean phenotype does not require enhanced leptin sensitivity (αδKO mice show normal leptin sensitivity), suggesting the alpha/delta isoforms regulate energy balance via a leptin-independent mechanism.","method":"SH2B1 alpha/delta brain-specific KO mice; metabolic phenotyping; leptin sensitivity assays","journal":"Diabetes","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — isoform-specific KO with metabolic and leptin sensitivity phenotyping, single lab","pmids":["33214137"],"is_preprint":false},{"year":2015,"finding":"SH2B1 is a positive mediator of pathological cardiac hypertrophy: cardiac-specific overexpression of SH2B1 exacerbates pressure overload-induced hypertrophy, fibrosis, and dysfunction, while SH2B1 KO produces the opposite phenotype. The pro-hypertrophic effects are mediated through activation of the JAK2/STAT3 signaling cascade; pharmacological JAK2 inactivation rescues abnormalities in SH2B1-overexpressing transgenic mice.","method":"Cardiac-specific SH2B1 transgenic mice; global SH2B1 KO rat; aortic banding model; JAK2 inhibitor rescue; JAK2/STAT3 signaling assays","journal":"Cardiovascular research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain- and loss-of-function in vivo plus pharmacological pathway rescue, single lab","pmids":["26077624"],"is_preprint":false},{"year":2013,"finding":"Hepatic SH2B1 adult-onset deletion attenuates HFD-induced hepatic steatosis by decreasing DGAT2 expression and increasing ATGL expression. Deletion of liver SH2B1 in SH2B2 null mice attenuates VLDL secretion. However, hepatic SH2B1 is not required for normal insulin sensitivity or glucose metabolism.","method":"Hepatocyte-specific SH2B1 KO mice (HKO); adult-onset liver deletion; DGAT2/ATGL expression; VLDL secretion assay; metabolic phenotyping","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — tissue-specific KO with lipid metabolism enzyme and VLDL secretion readouts, single lab","pmids":["24358267"],"is_preprint":false},{"year":2018,"finding":"Neural deletion of Sh2b1 decreases brain weight and causes pathological reactive aggression in mice. Brain-specific restoration of Sh2b1 normalizes brain size and reverses aggression and aberrant activation of amygdala/periaqueductal gray circuits. At the molecular level, Sh2b1 enhances neurotrophin-stimulated neuronal differentiation and protects against oxidative stress-induced neuronal death.","method":"Brain-specific Sh2b1 KO; AAV-mediated restoration; resident-intruder assay; c-fos immunoreactivity; neuronal differentiation and survival assays","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — brain-specific KO with brain-specific rescue plus circuit activation mapping, single lab","pmids":["29180441"],"is_preprint":false}],"current_model":"SH2B1 is a multifunctional adaptor protein that enhances signaling by JAK2, insulin receptor, TrkA/B, FGFR3, and EPO-R: its SH2 domain docks at phospho-Tyr813 of JAK2 (and equivalent sites on other kinases) to stimulate kinase activity, while its N-terminal dimerization domain mediates homo/heterodimerization that enables JAK2 transactivation; its PH domain is required for full metabolic function; it recruits IRS1/IRS2 into JAK2 complexes to amplify PI3K/Akt signaling and protects IRS proteins from dephosphorylation; it undergoes constitutive nucleocytoplasmic shuttling necessary for its pro-neuronal differentiation function; in the hypothalamus, neuronal SH2B1 is essential for leptin sensitivity, sympathetic nervous system activation, BAT thermogenesis, and energy balance, while peripheral SH2B1 in beta-cells, muscle, liver, and adipose tissue regulates insulin sensitivity, beta-cell survival, lipid metabolism, and VLDL secretion; additionally, SH2B1 interacts with IRSp53 to promote filopodium formation and neurite outgrowth, binds HSC70 to facilitate lysosomal PLIN4 degradation in neurons, maintains cytohesin-2 Tyr381 phosphorylation in Schwann cells to support myelination, and modulates chromatin state (histone H1 displacement, H3K4me3/H3K9me3 changes) and MyoD occupancy during myogenesis."},"narrative":{"mechanistic_narrative":"SH2B1 is a multidomain adaptor protein that amplifies signaling from receptor and cytoplasmic tyrosine kinases to govern energy balance, glucose homeostasis, and neuronal differentiation [PMID:16098827, PMID:15314154, PMID:10187854]. Its SH2 domain docks at a defined phosphotyrosine on its kinase targets — JAK2 pTyr813, recognized through canonical SH2-phosphopeptide contacts that select for Glu at +1 and a hydrophobic residue at +3 [PMID:15121872, PMID:16824542] — and this engagement stimulates kinase activity, whereas a separate pTyr813-independent contact on non-phosphorylated JAK2 holds basal activity in check, giving SH2B1 bidirectional control [PMID:17565041, PMID:16914724]. An N-terminal dimerization domain drives homo- and heterodimerization that juxtaposes two JAK2 molecules for transactivation [PMID:15767667], and the same SH2 module enhances the insulin receptor, TrkA, FGFR3, and EPO-R, with SH2B1 acting as a positive regulator of insulin and neurotrophin receptors but a negative regulator of EPO-R [PMID:15314154, PMID:10187854, PMID:11827956, PMID:22669948]. Downstream of leptin and insulin, SH2B1 recruits IRS1 and IRS2 into JAK2/receptor complexes and protects them from dephosphorylation, thereby amplifying PI3K/Akt output [PMID:15316008, PMID:19542202]. In the central nervous system, neuronal SH2B1 is the critical site for whole-body energy and glucose homeostasis: neuron-specific transgenic rescue corrects the obesity and insulin resistance of SH2B1-null mice in an SH2-domain-dependent manner [PMID:17235396, PMID:20484460], and hypothalamic SH2B1 drives leptin-stimulated sympathetic activation and brown adipose thermogenesis [PMID:32251290]. The PH domain is independently required for full metabolic function in vivo [PMID:31439647]. Beyond metabolism, SH2B1 promotes neurite outgrowth and filopodium formation through partners including IRSp53 [PMID:25586189], requires constitutive nucleocytoplasmic shuttling for its pro-differentiation activity [PMID:15082760], supports peripheral myelination by maintaining cytohesin-2 Tyr381 phosphorylation in Schwann cells [PMID:35077201], facilitates HSC70-dependent lysosomal degradation of PLIN4 to limit lipid peroxidation [PMID:35390677], and modulates chromatin state and MyoD occupancy during myogenesis [PMID:28039048]. Distinct isoforms diverge functionally, with the brain-enriched SH2B1delta localizing to nucleoli [PMID:35019135] and the alpha/delta isoforms regulating food intake through a leptin-independent route [PMID:33214137].","teleology":[{"year":1999,"claim":"Established that SH2-Bbeta is a kinase-engaging adaptor in neurotrophin signaling, the first link to neuronal differentiation, answering whether it physically and functionally couples to an activated receptor tyrosine kinase.","evidence":"GST pulldown, Co-IP, and dominant-negative R555E in NGF-stimulated PC12 cells with neurite outgrowth readout","pmids":["10187854"],"confidence":"High","gaps":["Did not define the JAK2 docking site or quantify direct kinase stimulation","Mechanism of how binding enhances outgrowth left open"]},{"year":1999,"claim":"Showed that SH2B1 engagement is not limited to neurotrophin receptors by mapping its insulin receptor interaction to an activation-loop phosphotyrosine, broadening the receptor repertoire.","evidence":"In vitro binding with IR kinase domain phosphopeptides; splice-variant (gamma) characterization","pmids":["10594240"],"confidence":"Medium","gaps":["No cellular or in vivo confirmation in this study","Functional consequence for IR signaling not yet tested"]},{"year":2001,"claim":"Defined the N-terminal multimerization domain as a structural requirement for kinase enhancement and revealed isoform/paralog selectivity, answering how SH2B proteins might assemble functional units.","evidence":"Gel filtration/native PAGE for pentamer state plus deletion mutants with TrkA autophosphorylation; JAK1/2/3 isoform-selective kinase assays","pmids":["11238898","11751854"],"confidence":"Medium","gaps":["Stoichiometry at endogenous levels unresolved","Distinct regulatory roles of SH2B1 vs APS on JAKs mechanistically unexplained"]},{"year":2004,"claim":"Identified JAK2 pTyr813 as the SH2 docking site and the JAK2/SH2B1/IRS tertiary complex as the mechanism amplifying PI3K/Akt, converting an adaptor observation into a defined molecular circuit.","evidence":"2D phosphopeptide mapping and JAK2 Y813 mutants; Co-IP, in vitro binding, and KO MEF rescue for IRS1/2 recruitment; tissue-specific KO insulin receptor readouts","pmids":["15121872","15316008","15314154"],"confidence":"High","gaps":["How SH2 docking allosterically increases kinase activity not resolved at atomic level","Relative contributions across receptors in vivo not separated"]},{"year":2005,"claim":"Connected the molecular adaptor function to physiology by showing SH2B1 is an endogenous enhancer of leptin sensitivity, and that dimerization transactivates JAK2 — explaining how loss causes obesity.","evidence":"SH2-B knockout mice with hypothalamic JAK2/STAT3/IRS2 readouts and PTP1B competition; yeast two-hybrid and concentration-dependent JAK2 kinase assays","pmids":["16098827","15767667"],"confidence":"High","gaps":["Cell type within hypothalamus not yet pinpointed","Biphasic concentration dependence of activation not validated in vivo"]},{"year":2006,"claim":"Provided structural and mutational definition of the SH2-pTyr813 interface and the dual positive/negative regulation of JAK2, resolving how one adaptor both inhibits basal and enhances activated kinase.","evidence":"2.35 A crystal structure of SH2 domain with JAK2 pTyr813 peptide; JAK2 truncation/point mutants in kinase assays; biochemical SH2B1 vs APS specificity","pmids":["16824542","16914724"],"confidence":"High","gaps":["Structure of full-length protein or kinase complex not determined","Conformational basis of inhibitory contact not visualized"]},{"year":2007,"claim":"Localized the metabolically essential pool of SH2B1 to neurons via genetic rescue, and dissected the two-mode JAK2 regulation in cells, establishing where and how SH2B1 controls energy balance.","evidence":"Neuron-specific transgenic rescue of KO mice with metabolic phenotyping; JAK2 Y813F and SH2B1 domain mutants by Co-IP; SH2B2beta inhibitory isoform pulldowns","pmids":["17235396","17565041","17204555"],"confidence":"High","gaps":["Specific neuronal population not defined","Endogenous role of inhibitory SH2B2beta isoform in vivo untested"]},{"year":2009,"claim":"Separated the peripheral, insulin-sensitizing arm of SH2B1 function and showed direct stimulation of the insulin receptor plus protection of IRS proteins from phosphatases, refining the in vivo division of labor.","evidence":"Tissue-specific TgKO mice on high-fat diet; reconstituted in vitro IR kinase and dephosphorylation assays with purified SH2B1 and domain mutants","pmids":["19542202"],"confidence":"High","gaps":["Phosphatases protected against not identified","Relative weight of central vs peripheral contribution to glucose control not quantified"]},{"year":2010,"claim":"Defined the downstream physiological circuit (SNS/BAT/thermogenesis) and showed the SH2 domain is required in vivo, linking the molecular docking mechanism to whole-organism thermogenic output.","evidence":"LepR-neuron-specific KO and hypothalamic AAV overexpression with sympathetic nerve recording; SH2-domain mutant (R555E) transgenic rescue and dominant-negative metabolic phenotyping","pmids":["32251290","20484460"],"confidence":"High","gaps":["Molecular targets coupling neuronal SH2B1 to SNS output not identified","How dominant-negative R555E acts at endogenous loci unclear"]},{"year":2013,"claim":"Extended SH2B1 function to beta-cell survival, insulin secretion, and lipid/VLDL metabolism, and identified an IRS2 stabilization mechanism, broadening its metabolic mechanism beyond signal amplification.","evidence":"Pancreas- and hepatocyte-specific KO mice; INS-1 knockdown/overexpression; insulin promoter-luciferase and Pdx1 ChIP; SH2B1/IRS2/JAK2 complex Co-IP and IRS2 ubiquitination assay; Drosophila Lnk epistasis and FRET","pmids":["24150605","24645678","24358267","27217487","23590848"],"confidence":"Medium","gaps":["Ubiquitin ligase acting on IRS2 not identified","Tissue-specific mechanisms not unified into a single model"]},{"year":2018,"claim":"Resolved domain- and isoform-specific control of SH2B1, including the inhibitory alpha tail and PH domain requirement, explaining how splice variants tune adaptor output.","evidence":"Tyr753 alpha-tail mutant analysis in PC12 cells; PH-domain knockin mice (P322S, deltaPR) with metabolic phenotyping; high-resolution SH2 structure with ITC","pmids":["29229648","31439647","29127727"],"confidence":"Medium","gaps":["PH domain ligand/lipid specificity not defined","How conformational plasticity selects ligands in cells untested"]},{"year":2022,"claim":"Uncovered kinase-independent and non-metabolic mechanisms — Schwann cell myelination via cytohesin-2 phosphorylation, HSC70-dependent PLIN4 degradation, and nucleolar isoform targeting — expanding SH2B1 beyond receptor signaling.","evidence":"Schwann cell-specific KD and cytohesin-2 Y381F knockin mice with Arf6 assays; SH2B1-HSC70 Co-IP and PLIN4 lysosomal/MPTP models; isoform rescue in KO neurons with nucleolar localization mapping","pmids":["35077201","35390677","35019135"],"confidence":"High","gaps":["How SH2B1 directs cytohesin-2 phosphorylation mechanistically unclear","Function of nucleolar SH2B1delta localization not defined"]},{"year":2023,"claim":"Demonstrated cell-type-specific behavioral roles, with hippocampal inhibitory-neuron SH2B1 acting as a negative ERK regulator controlling cognition, refining context-dependent signaling outputs.","evidence":"Cell-type-specific Sh2b1 KO with behavioral battery, single-cell profiling, and ERK-inhibitor pharmacological rescue","pmids":["38434247"],"confidence":"Medium","gaps":["Direct molecular substrate linking SH2B1 to ERK suppression unidentified","Reconciliation with SH2B1's positive role on ERK in neurotrophin signaling unresolved"]},{"year":null,"claim":"How SH2B1 isoform composition, domain conformation, and ligand selection are integrated to produce opposite (activating vs inhibitory) outputs across tissues and receptors remains the central open question.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No full-length structure showing both activating and inhibitory contacts simultaneously","Switch determining positive vs negative kinase regulation in vivo undefined","Direct substrates/effectors for non-canonical roles (chromatin, nucleolus) not mapped"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,4,6,7,30]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[3,4,6,11,24]},{"term_id":"GO:0042393","term_label":"histone binding","supporting_discovery_ids":[36]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[16,17,30]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[17,34]},{"term_id":"GO:0005730","term_label":"nucleolus","supporting_discovery_ids":[34]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[17]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,2,3,7]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[5,6,22,42]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[7,30,33,43]}],"complexes":[],"partners":["JAK2","IRS1","IRS2","TRKA","FGFR3","EPOR","IRSP53","HSPA8"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NRF2","full_name":"SH2B adapter protein 1","aliases":["Pro-rich, PH and SH2 domain-containing signaling mediator","PSM","SH2 domain-containing protein 1B"],"length_aa":756,"mass_kda":79.4,"function":"Adapter protein for several members of the tyrosine kinase receptor family. Involved in multiple signaling pathways mediated by Janus kinase (JAK) and receptor tyrosine kinases, including the receptors of insulin (INS), insulin-like growth factor 1 (IGF1), nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), platelet-derived growth factor (PDGF) and fibroblast growth factors (FGFs). In growth hormone (GH) signaling, autophosphorylated ('Tyr-813') JAK2 recruits SH2B1, which in turn is phosphorylated by JAK2 on tyrosine residues. These phosphotyrosines form potential binding sites for other signaling proteins. GH also promotes serine/threonine phosphorylation of SH2B1 and these phosphorylated residues may serve to recruit other proteins to the GHR-JAK2-SH2B1 complexes, such as RAC1. In leptin (LEP) signaling, binds to and potentiates the activation of JAK2 by globally enhancing downstream pathways. In response to leptin, binds simultaneously to both, JAK2 and IRS1 or IRS2, thus mediating formation of a complex of JAK2, SH2B1 and IRS1 or IRS2. Mediates tyrosine phosphorylation of IRS1 and IRS2, resulting in activation of the PI 3-kinase pathway. Acts as a positive regulator of NGF-mediated activation of the Akt/Forkhead pathway; prolongs NGF-induced phosphorylation of AKT1 on 'Ser-473' and AKT1 enzymatic activity. Enhances the kinase activity of the cytokine receptor-associated tyrosine kinase JAK2 and of other receptor tyrosine kinases, such as FGFR3 and NTRK1. For JAK2, the mechanism seems to involve dimerization of both, SH2B1 and JAK2. Enhances RET phosphorylation and kinase activity. Isoforms seem to be differentially involved in IGF1 and PDGF-induced mitogenesis (By similarity)","subcellular_location":"Cytoplasm; Membrane; Nucleus","url":"https://www.uniprot.org/uniprotkb/Q9NRF2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SH2B1","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CALM1","stoichiometry":0.2},{"gene":"CALM2","stoichiometry":0.2},{"gene":"CALM3","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/SH2B1","total_profiled":1310},"omim":[{"mim_id":"615835","title":"CHROMOSOME 16 INVERSION, 0.45-MB","url":"https://www.omim.org/entry/615835"},{"mim_id":"613444","title":"CHROMOSOME 16p11.2 DELETION SYNDROME, 220-KB","url":"https://www.omim.org/entry/613444"},{"mim_id":"608937","title":"SH2B ADAPTOR PROTEIN 1; SH2B1","url":"https://www.omim.org/entry/608937"},{"mim_id":"606641","title":"BODY MASS INDEX QUANTITATIVE TRAIT LOCUS 1; BMIQ1","url":"https://www.omim.org/entry/606641"},{"mim_id":"601665","title":"OBESITY","url":"https://www.omim.org/entry/601665"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Centriolar satellite","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/SH2B1"},"hgnc":{"alias_symbol":["FLJ30542","SH2B"],"prev_symbol":[]},"alphafold":{"accession":"Q9NRF2","domains":[{"cath_id":"2.30.29.30","chopping":"249-254_286-375","consensus_level":"medium","plddt":87.5948,"start":249,"end":375},{"cath_id":"3.30.505.10","chopping":"523-623","consensus_level":"high","plddt":88.1534,"start":523,"end":623},{"cath_id":"1.10.287","chopping":"29-78","consensus_level":"high","plddt":92.4128,"start":29,"end":78}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NRF2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NRF2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NRF2-F1-predicted_aligned_error_v6.png","plddt_mean":57.28},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SH2B1","jax_strain_url":"https://www.jax.org/strain/search?query=SH2B1"},"sequence":{"accession":"Q9NRF2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NRF2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NRF2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NRF2"}},"corpus_meta":[{"pmid":"16098827","id":"PMC_16098827","title":"Identification 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Overexpression of SH2-B counteracted PTP1B-mediated inhibition of leptin signaling in cultured cells.\",\n      \"method\": \"SH2-B knockout mouse model; in vitro overexpression/PTP1B competition assay; hypothalamic signaling readouts\",\n      \"journal\": \"Cell metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined cellular phenotype, replicated across multiple signaling readouts, independently corroborated by subsequent studies\",\n      \"pmids\": [\"16098827\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"SH2-B promotes activation of the PI3-kinase pathway downstream of leptin by directly binding IRS1 and IRS2 (via its PH and SH2 domains) and mediating formation of a JAK2/SH2-B/IRS1(or IRS2) tertiary complex, dramatically enhancing leptin-stimulated tyrosine phosphorylation of IRS1/IRS2 and subsequent Akt activation. Deletion of SH2-B gene impaired this phosphorylation in MEFs.\",\n      \"method\": \"Co-immunoprecipitation; in vitro binding; HEK293 overexpression; MEF knockout rescue; SH2-B domain mutants\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (in vitro binding, Co-IP, KO MEF rescue, domain mutants), replicated by subsequent work\",\n      \"pmids\": [\"15316008\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"SH2-B is a physiological enhancer of insulin receptor activation: systemic deletion of SH2-B impairs insulin receptor activation and signaling (IRS1/IRS2 phosphorylation, PI3K/Akt, ERK1/2) in liver, muscle, and fat. SH2-B directly enhanced autophosphorylation of insulin receptor and tyrosine phosphorylation of IRS1/IRS2 in an SH2 domain-dependent manner in cultured cells.\",\n      \"method\": \"SH2-B knockout mouse; in vitro kinase assay; cultured cell overexpression with domain mutants\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vivo KO with tissue-specific signaling readouts plus in vitro kinase assay with domain mutants\",\n      \"pmids\": [\"15314154\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"JAK2 autophosphorylation on Tyr813 is the critical docking site for the SH2 domain of SH2-Bbeta; phosphorylation of Tyr813 is required for SH2-Bbeta to bind JAK2 and to enhance JAK2 activity and STAT5B activation. The homologous Tyr785 in JAK3 similarly mediates SH2-Bbeta binding and is autophosphorylated in response to IL-2.\",\n      \"method\": \"2D phosphopeptide mapping; phosphospecific antibody; JAK2 Tyr813 mutants; in vitro kinase assays; Co-IP\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — 2D phosphopeptide mapping plus mutagenesis plus functional kinase assay, all in one study\",\n      \"pmids\": [\"15121872\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"SH2B1 regulates leptin/JAK2 signaling by two mechanisms: (1) constitutive binding via non-SH2 domain regions to non-phosphorylated JAK2 inhibits basal JAK2 activity; (2) leptin-stimulated phosphorylation of JAK2 Tyr813 recruits the SH2 domain of SH2B1, which then enhances JAK2 activity. Additionally, SH2B1-IRS1 interaction (independent of Tyr813) facilitates IRS1 phosphorylation by recruiting IRS1 to JAK2.\",\n      \"method\": \"Co-immunoprecipitation; JAK2 Y813F mutants; overexpression in cells; domain deletion mutants\",\n      \"journal\": \"Molecular endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal domain-mapping with multiple SH2B1 and JAK2 mutants, consistent with prior structural/biochemical data\",\n      \"pmids\": [\"17565041\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Neuron-specific expression of SH2B1beta (using transgenic rescue of SH2B1 knockout mice) is sufficient to correct metabolic disorders including leptin resistance, hyperphagia, obesity, hyperglycemia, and insulin resistance, demonstrating that neuronal SH2B1 is the critical site for whole-body energy and glucose homeostasis.\",\n      \"method\": \"Neuron-specific transgenic rescue of SH2B1 knockout mice (SH2B1TgKO); metabolic phenotyping; hypothalamic JAK2/leptin signaling readouts\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic rescue experiment in vivo with tissue-specific transgene, multiple metabolic and signaling endpoints\",\n      \"pmids\": [\"17235396\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Peripheral SH2B1 enhances insulin sensitivity by two mechanisms: (1) directly stimulating insulin receptor catalytic activity (the SH2 domain is required and sufficient); (2) binding IRS-1 and IRS-2 and protecting them from tyrosine dephosphorylation. Deletion of peripheral SH2B1 in TgKO mice markedly worsens high-fat diet-induced insulin resistance.\",\n      \"method\": \"Tissue-specific KO (TgKO) mice; in vitro insulin receptor kinase assay with purified SH2B1; in vitro dephosphorylation assay; domain deletion mutants; Co-IP\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro reconstituted kinase assay plus dephosphorylation assay plus in vivo tissue-specific KO, multiple orthogonal methods\",\n      \"pmids\": [\"19542202\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"SH2-Bbeta is required for NGF-induced neuronal differentiation: it binds to TrkA in an SH2 domain-dependent manner (NGF stimulates binding; SH2-Bbeta R555E mutant cannot bind), and overexpression of SH2-Bbeta enhances NGF-induced neurite outgrowth while dominant-negative R555E blocks it. SH2-Bbeta is tyrosyl-phosphorylated in response to NGF.\",\n      \"method\": \"GST pulldown; Co-IP in PC12 cells; GFP-fusion protein overexpression; neurite outgrowth assay; dominant-negative mutant\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP plus GST pulldown plus dominant-negative and gain-of-function experiments with functional readout\",\n      \"pmids\": [\"10187854\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"SH2-B and APS exist as homopentamers and/or heteropentamers in cells (independent of Trk activation), mediated by the N-terminal multimerization domain. The N-terminal multimerization domain is required for SH2-B to enhance TrkA autophosphorylation magnitude and duration following NGF, and for TrkA/SH2-B-mediated morphological differentiation of PC12 cells.\",\n      \"method\": \"Gel filtration/native PAGE (multimerization); structure-function analysis with deletion mutants; overexpression in PC12 cells; TrkA autophosphorylation assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — biochemical demonstration of pentameric state plus domain deletion mutants with functional readouts\",\n      \"pmids\": [\"11238898\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Human SH2-B homodimerizes via a unique N-terminal dimerization domain; dimerization brings two JAK2 molecules into proximity for transactivation. At low SH2-B levels, dimerization activates JAK2 by forming JAK2-(SH2-B)2-JAK2 heterotetramers; at high levels, kinase activation is blocked. SH2-B and APS also heterodimerize.\",\n      \"method\": \"Yeast two-hybrid; cellular transfection; in vitro binding; JAK2 kinase activity assays with varying SH2-B concentrations\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — yeast two-hybrid plus cellular co-transfection plus kinase assays; mechanistic model validated across multiple assays in one study\",\n      \"pmids\": [\"15767667\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Crystal structure (2.35 Å) of the SH2 domain of SH2-B in complex with a phosphopeptide from JAK2 pTyr813 reveals canonical SH2 domain-phosphopeptide binding with specific recognition of Glu at +1 and a hydrophobic residue at +3. Biochemical comparison shows SH2-B SH2 domain binds JAK2 preferentially (monomeric state) while APS SH2 domain has higher affinity for the insulin receptor (dimeric state).\",\n      \"method\": \"X-ray crystallography (2.35 Å); in vitro binding assays comparing SH2-B and APS SH2 domains\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with biochemical validation in a single rigorous study\",\n      \"pmids\": [\"16824542\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"SH2-Bbeta binds JAK2 at multiple sites; binding to pTyr813 is essential for APS (and SH2-Bbeta) to enhance active JAK2. Binding to a pTyr813-independent site on JAK2 inhibits JAK2. SH2-Bbeta-induced increases in JAK2 activity require only the SH2 domain and only one SH2-Bbeta bound to a JAK2 dimer. Residues 809-811 in JAK2 are critical for a regulatory region required for SH2-Bbeta activation.\",\n      \"method\": \"JAK2 truncation and point mutants; in vitro kinase assays; domain deletion analysis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — extensive mutagenesis of both SH2-Bbeta and JAK2 combined with kinase activity assays\",\n      \"pmids\": [\"16914724\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"SH2-Bbeta specifically activates JAK2 but not JAK1 or JAK3 when overexpressed. APS negatively regulates JAK2 and JAK1. Endogenous APS is tyrosyl-phosphorylated in response to GH and interferon-gamma. Both SH2-Bbeta and APS bind all three JAKs, but their regulatory roles on JAK activity are distinct.\",\n      \"method\": \"Overexpression in cells; JAK1/2/3 kinase activity assays; endogenous tyrosyl-phosphorylation detection; 3T3-F442A adipocytes\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple kinase isoforms tested with functional assays in a single study, no independent replication reported\",\n      \"pmids\": [\"11751854\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"NGF stimulates phosphorylation of SH2-B on multiple serine/threonine residues via kinases downstream of MEK/ERK (ERK1/2 phosphorylate SH2-Bbeta on Ser96 in vitro); MEK inhibitor PD98059 dramatically reduces NGF-promoted serine/threonine phosphorylation. An intact SH2 domain (but not Ser96 alone) is required for full NGF-stimulated serine/threonine phosphorylation.\",\n      \"method\": \"In vitro kinase assay with ERK1/2; MEK inhibitor PD98059; phosphatase treatment; SH2-Bbeta point mutants (S96A, R555E)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro kinase assay identifies Ser96 plus pharmacological and genetic validation in cells, single lab\",\n      \"pmids\": [\"10473609\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"SH2-B (SH2-Bgamma isoform) interacts specifically with the insulin receptor, requiring phosphorylation of Tyr1146 in the activation loop triple-tyrosine motif of the IR kinase domain.\",\n      \"method\": \"In vitro binding with phosphopeptides and IR kinase domain; alternative splice variant characterization\",\n      \"journal\": \"Mammalian genome\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phosphorylation-site requirement mapped by in vitro binding with defined phosphopeptides, single lab\",\n      \"pmids\": [\"10594240\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"SH2-Bbeta interacts with FGFR3 via its SH2 domain; two FGFR3 phosphotyrosines (Tyr724 and Tyr760) are required for optimal SH2 domain binding. SH2-Bbeta is tyrosyl-phosphorylated by activated FGFR3. Overexpression of SH2-Bbeta increases FGFR3-stimulated STAT5 phosphorylation and nuclear translocation.\",\n      \"method\": \"Yeast two-hybrid; Co-IP; FGFR3 mutants (N540K, K650E); STAT5 phosphorylation/localization assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid plus Co-IP plus functional STAT5 readout in a single study, single lab\",\n      \"pmids\": [\"11827956\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"SH2-Bbeta is required for GH-induced actin reorganization (membrane ruffling and pinocytosis) in 3T3-F442A cells. SH2-Bbeta co-localizes with F-actin in GH-induced membrane ruffles. This function requires the SH2 domain and N-terminal regions but is discrete from SH2-Bbeta's role as a JAK2 kinase activator.\",\n      \"method\": \"Cell fractionation; confocal microscopy; overexpression of wild-type and mutant SH2-Bbeta; ruffling and pinocytosis assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization by confocal plus functional actin readout with multiple domain mutants, single lab\",\n      \"pmids\": [\"10777618\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"SH2-Bbeta undergoes constitutive nucleocytoplasmic shuttling; a nuclear export sequence (amino acids 224-233) is required for cytoplasmic/plasma membrane access. Nuclear export-defective SH2-Bbeta (L231A/L233A) accumulates in the nucleus and loses the ability to enhance NGF-induced neurite outgrowth, without altering ERK1/2 phosphorylation, indicating cytoplasmic/plasma membrane localization is required for its pro-differentiation function.\",\n      \"method\": \"Leptomycin B nuclear export inhibitor; truncation/point mutants with NES deletion; confocal imaging of GFP-SH2-Bbeta; stable PC12 cell lines; neurite outgrowth assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — pharmacological plus genetic disruption of NES with functional consequence, clear localization-function link demonstrated\",\n      \"pmids\": [\"15082760\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"SH2-Bbeta positively regulates NGF-mediated activation of the Akt/Forkhead pathway: PC12 cells overexpressing SH2-Bbeta show enhanced and prolonged NGF-induced Akt phosphorylation (Ser473) and activity, and increased phosphorylation of GSK-3 and FKHR/FOXO. Dominant-negative R555E blocks NGF-induced redistribution of FKHR to the cytoplasm and Akt activation.\",\n      \"method\": \"Stable PC12 cell overexpression; Akt kinase activity assay; immunolocalization of FKHR; SH2 domain mutant (R555E)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain- and loss-of-function with functional downstream pathway readouts, single lab\",\n      \"pmids\": [\"14565960\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"SH2B2beta, a novel SH2B2 isoform lacking an SH2 domain, forms heterodimers with SH2B1 and SH2B2alpha (demonstrated by GST pulldown and Co-IP). SH2B2beta markedly attenuates SH2B1-promoted JAK2 activation and IRS-1 phosphorylation by JAK2, acting as an endogenous inhibitor of SH2B1.\",\n      \"method\": \"GST fusion protein pulldown; Co-IP; JAK2 kinase activation assay; IRS-1 phosphorylation assay\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal pulldown and Co-IP plus functional kinase/phosphorylation readouts in a single study\",\n      \"pmids\": [\"17204555\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"SH2B1 in neuronal SH2B1 deletion mice (LepR neuron-specific Sh2b1 deletion) abrogates leptin-stimulated sympathetic nerve activation and impairs BAT thermogenic programs, revealing an SH2B1/SNS/BAT/thermogenesis axis. Hypothalamic overexpression of human SH2B1 has opposite effects (increased SNS activity, thermogenesis) and protects against diet-induced obesity.\",\n      \"method\": \"LepR neuron-specific Sh2b1 KO; adeno-associated virus-mediated hypothalamic overexpression; sympathetic nerve recording; BAT thermogenesis assays; metabolic phenotyping\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — tissue-specific KO and overexpression with direct SNS recording and thermogenesis readouts\",\n      \"pmids\": [\"32251290\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The SH2 domain of neuronal SH2B1 is required for maintenance of normal body weight and glucose metabolism in vivo: SH2 domain-defective (R555E) or SH2 domain-alone (DeltaN503) transgenes fail to rescue obesity/insulin resistance in SH2B1 null mice. Neuron-specific expression of R555E in wild-type mice promotes obesity and insulin resistance (dominant negative).\",\n      \"method\": \"Neuron-specific transgenic rescue with SH2-domain mutants; metabolic phenotyping\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo domain-mutant transgenic rescue with clear dominant-negative effect, multiple mutants tested\",\n      \"pmids\": [\"20484460\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"SH2B1 in pancreatic beta-cells promotes beta-cell survival and proliferation via the PI3K/Akt pathway: knockdown attenuates insulin/IGF-1-stimulated PI3K/Akt activation and increases apoptosis; pancreas-specific SH2B1 KO on HFD leads to increased beta-cell apoptosis, decreased beta-cell mass, impaired insulin secretion, and exacerbated glucose intolerance.\",\n      \"method\": \"INS-1 cell knockdown/overexpression; pancreas-specific KO mice (PKO); streptozotocin challenge; beta-cell mass/apoptosis/proliferation assays; HFD metabolic phenotyping\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — tissue-specific KO plus in vitro gain/loss-of-function with multiple cellular endpoints\",\n      \"pmids\": [\"24150605\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"SH2B1 in beta-cells promotes insulin gene expression and glucose-stimulated insulin secretion at least in part by enhancing JAK2 activation of the insulin promoter and increasing Pdx1 expression and its recruitment to the insulin promoter.\",\n      \"method\": \"INS-1 cell knockdown/overexpression; insulin promoter-luciferase assay; Pdx1 chromatin immunoprecipitation; islet insulin content measurement\",\n      \"journal\": \"Molecular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus promoter-reporter plus gain/loss-of-function in beta-cells, single lab\",\n      \"pmids\": [\"24645678\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"SH2B1beta associates with the erythropoietin receptor (EPO-R) at pTyr343 and pTyr401 via its SH2 domain (pYXXL motif), as shown by COLT screening and Co-IP. In hematopoietic cells, SH2B1beta preferentially associates with EPO-R over JAK2. Constitutive SH2B1-EPO-R association is needed for optimal SH2-dependent recruitment. In the absence of SH2B1, EPO-R downstream signaling is enhanced, indicating SH2B1 is a negative regulator of EPO signaling.\",\n      \"method\": \"COLT screening; Co-IP; in vitro mixing; domain-dependency experiments; SH2B1 knockdown with EPO signaling readouts\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — COLT plus Co-IP plus loss-of-function signaling readout in single study\",\n      \"pmids\": [\"22669948\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"SH2-B promotes adipocyte differentiation by enhancing insulin/IGF-I receptor-Akt-Foxo1 signaling, leading to increased PPARgamma mRNA levels. SH2-B deficient MEFs show reduced adipogenesis and PPARgamma levels in response to insulin; this upregulation of PPARgamma is blocked by PI3K inhibition but not MEK inhibition.\",\n      \"method\": \"SH2-B KO MEFs; 3T3-L1 retroviral overexpression; adipogenesis assays; PI3K/MEK inhibitors; PPARgamma mRNA/protein measurement; Akt and FKHR/Foxo1 phosphorylation assays\",\n      \"journal\": \"Molecular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO MEF plus overexpression in 3T3-L1 plus pharmacological pathway dissection, single lab\",\n      \"pmids\": [\"17312274\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"In Drosophila, Lnk (SH2B ortholog) acts upstream of PI3K at the same level as Chico (IRS), downstream of InR. FRET analysis reveals in vivo binding among InR, Chico, and Lnk. Lnk ensures Chico plasma membrane localization (via both Chico PH domain and Lnk interaction) and recruits an intracellular InR fragment to the membrane, providing a fail-safe mechanism for IIS activation.\",\n      \"method\": \"Genetic epistasis in Drosophila; FRET analysis in vivo; membrane localization assays; double mutant analysis\",\n      \"journal\": \"Cell communication and signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — FRET plus genetic epistasis and membrane localization, single lab, ortholog study\",\n      \"pmids\": [\"23590848\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Drosophila Lnk (SH2B ortholog) acts in the IIS pathway downstream of InR and upstream of PI3K, in parallel to the IRS ortholog Chico. Lnk and Chico double mutants are synthetically lethal, indicating partially redundant functions. Loss of Lnk function also extends lifespan and improves stress survival via effects on both IIS and Ras/MAPK pathways.\",\n      \"method\": \"Drosophila genetic epistasis; PIP3 reporter localization; PKB phosphorylation assay; double mutant synthetic lethality\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with signaling readouts, double mutant lethality, ortholog study\",\n      \"pmids\": [\"19680438\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PSM/SH2B1 splice variants (gamma > delta > alpha > beta) directly potentiate Src tyrosine kinase catalytic activity (increasing Vmax and decreasing Km for ATP) and are Src substrates. SH2B1 and Src co-immunoprecipitate. SH2B1 domain-specific peptide mimetics (SH2 or PH domains) inhibit Src activity and Src-mediated STAT3s activation and phenotypic cell transformation.\",\n      \"method\": \"Co-IP with Src; in vitro kinase assay (Vmax/Km determination); herbimycin inhibitor; dominant-negative peptide mimetics; STAT3 phosphorylation assay; transformation assay\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro kinase parameters plus Co-IP plus domain inhibitor experiments, single lab\",\n      \"pmids\": [\"18247337\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"SH2B1 promotes beta-cell mass by preventing IRS2 ubiquitination: 4E-BP2 deletion induces translation of SH2B1, which forms a complex with IRS2 and JAK2 that prevents IRS2 ubiquitination, thereby increasing IRS2 levels, Akt signaling, and beta-cell proliferation and survival.\",\n      \"method\": \"4E-BP2 KO mice; Co-IP of SH2B1/IRS2/JAK2 complex; IRS2 ubiquitination assay; beta-cell mass/proliferation/survival assays\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP demonstrating ternary complex plus ubiquitination assay plus in vivo genetic model, single lab\",\n      \"pmids\": [\"27217487\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"SH2B1 interacts with IRSp53 via its N-terminal proline-rich domains in hippocampal neurons. SH2B1-IRSp53 complexes co-localize at the plasma membrane and in the Triton X-100-insoluble fraction. Overexpressing both SH2B1beta and IRSp53 significantly enhances filopodium formation, neurite outgrowth, and branching.\",\n      \"method\": \"Co-IP in hippocampal neurons and 293T cells; confocal co-localization; subcellular fractionation; overexpression assays; filopodium/neurite quantification\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus fractionation plus functional filopodium/neurite readouts in neurons, single lab\",\n      \"pmids\": [\"25586189\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"SH2B1 promotes BDNF-induced neurite outgrowth in PC12/TrkB cells by enhancing MEK-ERK1/2 and PI3K-AKT signaling. SH2B1beta also enhances BDNF-stimulated STAT3 phosphorylation on Ser727. The SH2 domain and tyrosine phosphorylation of SH2B1beta are required for these BDNF signaling effects.\",\n      \"method\": \"Stable PC12 (TrkB) cell overexpression; kinase inhibitor experiments; SH2 domain and phosphorylation mutants; neurite outgrowth assay; western blotting\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain/loss-of-function with domain mutants and pathway inhibitors, single lab\",\n      \"pmids\": [\"24260264\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The unique C-terminal alpha tail of SH2B1alpha inhibits SH2B1 functions (nuclear cycling, NGF-mediated neurite outgrowth, TrkA autophosphorylation, Akt and PLC-gamma phosphorylation) via TrkA-mediated phosphorylation of Tyr753 in the alpha tail. Mutation Y753F restores these functions. SH2B1alpha also inhibits SH2B1beta-mediated neurite outgrowth in a Tyr753-dependent manner.\",\n      \"method\": \"PC12 cell overexpression; TrkA co-expression; Tyr753Phe mutant analysis; Akt/PLC-gamma phosphorylation assays; neurite outgrowth quantification\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis plus functional readouts identifying isoform-specific phospho-regulation, single lab\",\n      \"pmids\": [\"29229648\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SH2B1 promotes phosphorylation of cytohesin-2 at Tyr381 in Schwann cells, which is required for cytohesin-2 Arf6 GEF activity and peripheral nervous system myelination. Schwann cell-specific loss of SH2B1 reduces cytohesin-2 Tyr381 phosphorylation and myelin thickness in sciatic nerve. PTP4A1 dephosphorylates the same site, acting antagonistically to SH2B1.\",\n      \"method\": \"Schwann cell-specific SH2B1 knockdown mice; cytohesin-2 Y381F knockin mice; Arf6 activity assay; myelin thickness measurement; HEK293T co-expression with PTP4A1\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo Schwann cell-specific KD plus knockin phospho-mutant mice plus Arf6 activity assay plus antagonistic phosphatase identification\",\n      \"pmids\": [\"35077201\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SH2B1delta is the predominant brain-specific isoform that localizes primarily to nucleoli (driven by two highly basic regions unique to delta), with some at plasma membrane/nucleus. All four SH2B1 isoforms rescue decreased neurite complexity in Sh2b1 KO neurons; SH2B1delta also increases total neurite length and BDNF-induced expression of Egr1, Arc and FosL1. Human obesity variants in SH2B1delta alter neurite branching, linking nucleolar function to neurobehavioral phenotypes.\",\n      \"method\": \"Primary hippocampal neuron KO rescue with individual isoforms; confocal localization; deletion/mutation of basic regions; BDNF-induced gene expression assay; neurite complexity quantification\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO neuron isoform rescue plus domain deletion for nucleolar targeting plus functional gene expression readouts, single lab\",\n      \"pmids\": [\"35019135\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SH2B1 promotes PLIN4 lysosomal degradation by binding to HSC70, facilitating HSC70-mediated PLIN4 recognition and lysosomal translocation, thereby suppressing lipid peroxidation and protecting against neurodegeneration in an MPTP Parkinson's disease mouse model.\",\n      \"method\": \"Co-IP (SH2B1-HSC70); Sh2b1 KO and neuron-specific Sh2b1 overexpression mice; AAV-HSC70 rescue; PLIN4 lysosomal translocation assay; lipid peroxidation measurement; behavioral assays\",\n      \"journal\": \"Redox biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus in vivo rescue experiments establishing SH2B1-HSC70-PLIN4 axis, single lab\",\n      \"pmids\": [\"35390677\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"SH2B1 modulates chromatin state during myogenesis: it interacts with histone H1 and is required for removal of histone H1 from active transcription sites, enabling H3K4me3 induction and H3K9me3 reduction at IGF2 and MYOG promoters/enhancers. SH2B1 knockdown delays chromatin condensation and decreases myotube formation. SH2B1 is also required for MyoD occupancy at IGF2 and MYOG enhancer/promoter regions.\",\n      \"method\": \"SH2B1 knockdown in myoblasts; Co-IP with histone H1; chromatin immunoprecipitation (H3K4me3, H3K9me3, MyoD); myotube formation assay\",\n      \"journal\": \"Biochimica et biophysica acta. Gene regulatory mechanisms\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with histones plus ChIP-based histone modification and TF occupancy analysis in differentiation context, single lab\",\n      \"pmids\": [\"28039048\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Selective deletion of Sh2b1 in hippocampal inhibitory (but not excitatory) neurons impairs working memory, short-term object recognition, and behavioral flexibility in mice. Sh2b1 deletion in these neurons leads to aberrantly enhanced ERK signaling; pharmacological ERK inhibition reverses the behavioral impairment, placing hippocampal SH2B1 as a negative regulator of ERK in inhibitory neurons controlling fluid intelligence.\",\n      \"method\": \"Cell-type-specific Sh2b1 KO (inhibitory vs. excitatory neurons); behavioral battery; single-cell RNA/protein profiling; ERK inhibitor pharmacological rescue\",\n      \"journal\": \"Research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-type-specific KO with pharmacological rescue establishing ERK signaling mechanism, single study\",\n      \"pmids\": [\"38434247\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The PH domain of SH2B1 is crucial for energy balance: a two-amino acid deletion (ΔPR, residues 317-318) in the PH domain causes obesity and insulin resistance beyond that attributable to adiposity in mice. A human variant P322S/+ causes late-onset glucose intolerance. The PH domain is thus required for full SH2B1 metabolic function in vivo.\",\n      \"method\": \"SH2B1 PH domain knockin mouse models (P322S, ΔPR); metabolic phenotyping; glucose/insulin tolerance tests\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo knockin mouse models with PH domain mutations and detailed metabolic phenotyping, single lab\",\n      \"pmids\": [\"31439647\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"The SH2 domain of SH2B1 recognizes diverse phosphopeptides (from JAK2 pTyr813, insulin receptor, IRS-1/2) with distinct thermodynamic signatures. Key residues K575 and R578 play distinct roles in binding chemically disparate ligands (+3 hydrophobic vs. +1 acidic). High-resolution structure of the SH2B1 SH2 domain reveals conformationally plastic loops enabling recognition of dissimilar ligands.\",\n      \"method\": \"X-ray crystallography (high-resolution); isothermal titration calorimetry; site-directed mutagenesis of SH2 domain residues\",\n      \"journal\": \"Proteins\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure plus thermodynamic binding measurements plus mutagenesis in one study\",\n      \"pmids\": [\"29127727\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Deletion of brain-specific SH2B1alpha and SH2B1delta isoforms (αδKO mice) decreases food intake and protects from weight gain on standard and high-fat diets, with adiposity-dependent improvement in glucose homeostasis. This lean phenotype does not require enhanced leptin sensitivity (αδKO mice show normal leptin sensitivity), suggesting the alpha/delta isoforms regulate energy balance via a leptin-independent mechanism.\",\n      \"method\": \"SH2B1 alpha/delta brain-specific KO mice; metabolic phenotyping; leptin sensitivity assays\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — isoform-specific KO with metabolic and leptin sensitivity phenotyping, single lab\",\n      \"pmids\": [\"33214137\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"SH2B1 is a positive mediator of pathological cardiac hypertrophy: cardiac-specific overexpression of SH2B1 exacerbates pressure overload-induced hypertrophy, fibrosis, and dysfunction, while SH2B1 KO produces the opposite phenotype. The pro-hypertrophic effects are mediated through activation of the JAK2/STAT3 signaling cascade; pharmacological JAK2 inactivation rescues abnormalities in SH2B1-overexpressing transgenic mice.\",\n      \"method\": \"Cardiac-specific SH2B1 transgenic mice; global SH2B1 KO rat; aortic banding model; JAK2 inhibitor rescue; JAK2/STAT3 signaling assays\",\n      \"journal\": \"Cardiovascular research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain- and loss-of-function in vivo plus pharmacological pathway rescue, single lab\",\n      \"pmids\": [\"26077624\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Hepatic SH2B1 adult-onset deletion attenuates HFD-induced hepatic steatosis by decreasing DGAT2 expression and increasing ATGL expression. Deletion of liver SH2B1 in SH2B2 null mice attenuates VLDL secretion. However, hepatic SH2B1 is not required for normal insulin sensitivity or glucose metabolism.\",\n      \"method\": \"Hepatocyte-specific SH2B1 KO mice (HKO); adult-onset liver deletion; DGAT2/ATGL expression; VLDL secretion assay; metabolic phenotyping\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — tissue-specific KO with lipid metabolism enzyme and VLDL secretion readouts, single lab\",\n      \"pmids\": [\"24358267\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Neural deletion of Sh2b1 decreases brain weight and causes pathological reactive aggression in mice. Brain-specific restoration of Sh2b1 normalizes brain size and reverses aggression and aberrant activation of amygdala/periaqueductal gray circuits. At the molecular level, Sh2b1 enhances neurotrophin-stimulated neuronal differentiation and protects against oxidative stress-induced neuronal death.\",\n      \"method\": \"Brain-specific Sh2b1 KO; AAV-mediated restoration; resident-intruder assay; c-fos immunoreactivity; neuronal differentiation and survival assays\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — brain-specific KO with brain-specific rescue plus circuit activation mapping, single lab\",\n      \"pmids\": [\"29180441\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SH2B1 is a multifunctional adaptor protein that enhances signaling by JAK2, insulin receptor, TrkA/B, FGFR3, and EPO-R: its SH2 domain docks at phospho-Tyr813 of JAK2 (and equivalent sites on other kinases) to stimulate kinase activity, while its N-terminal dimerization domain mediates homo/heterodimerization that enables JAK2 transactivation; its PH domain is required for full metabolic function; it recruits IRS1/IRS2 into JAK2 complexes to amplify PI3K/Akt signaling and protects IRS proteins from dephosphorylation; it undergoes constitutive nucleocytoplasmic shuttling necessary for its pro-neuronal differentiation function; in the hypothalamus, neuronal SH2B1 is essential for leptin sensitivity, sympathetic nervous system activation, BAT thermogenesis, and energy balance, while peripheral SH2B1 in beta-cells, muscle, liver, and adipose tissue regulates insulin sensitivity, beta-cell survival, lipid metabolism, and VLDL secretion; additionally, SH2B1 interacts with IRSp53 to promote filopodium formation and neurite outgrowth, binds HSC70 to facilitate lysosomal PLIN4 degradation in neurons, maintains cytohesin-2 Tyr381 phosphorylation in Schwann cells to support myelination, and modulates chromatin state (histone H1 displacement, H3K4me3/H3K9me3 changes) and MyoD occupancy during myogenesis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SH2B1 is a multidomain adaptor protein that amplifies signaling from receptor and cytoplasmic tyrosine kinases to govern energy balance, glucose homeostasis, and neuronal differentiation [#0, #2, #7]. Its SH2 domain docks at a defined phosphotyrosine on its kinase targets — JAK2 pTyr813, recognized through canonical SH2-phosphopeptide contacts that select for Glu at +1 and a hydrophobic residue at +3 [#3, #10] — and this engagement stimulates kinase activity, whereas a separate pTyr813-independent contact on non-phosphorylated JAK2 holds basal activity in check, giving SH2B1 bidirectional control [#4, #11]. An N-terminal dimerization domain drives homo- and heterodimerization that juxtaposes two JAK2 molecules for transactivation [#9], and the same SH2 module enhances the insulin receptor, TrkA, FGFR3, and EPO-R, with SH2B1 acting as a positive regulator of insulin and neurotrophin receptors but a negative regulator of EPO-R [#2, #7, #15, #24]. Downstream of leptin and insulin, SH2B1 recruits IRS1 and IRS2 into JAK2/receptor complexes and protects them from dephosphorylation, thereby amplifying PI3K/Akt output [#1, #6]. In the central nervous system, neuronal SH2B1 is the critical site for whole-body energy and glucose homeostasis: neuron-specific transgenic rescue corrects the obesity and insulin resistance of SH2B1-null mice in an SH2-domain-dependent manner [#5, #21], and hypothalamic SH2B1 drives leptin-stimulated sympathetic activation and brown adipose thermogenesis [#20]. The PH domain is independently required for full metabolic function in vivo [#38]. Beyond metabolism, SH2B1 promotes neurite outgrowth and filopodium formation through partners including IRSp53 [#30], requires constitutive nucleocytoplasmic shuttling for its pro-differentiation activity [#17], supports peripheral myelination by maintaining cytohesin-2 Tyr381 phosphorylation in Schwann cells [#33], facilitates HSC70-dependent lysosomal degradation of PLIN4 to limit lipid peroxidation [#35], and modulates chromatin state and MyoD occupancy during myogenesis [#36]. Distinct isoforms diverge functionally, with the brain-enriched SH2B1delta localizing to nucleoli [#34] and the alpha/delta isoforms regulating food intake through a leptin-independent route [#40].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Established that SH2-Bbeta is a kinase-engaging adaptor in neurotrophin signaling, the first link to neuronal differentiation, answering whether it physically and functionally couples to an activated receptor tyrosine kinase.\",\n      \"evidence\": \"GST pulldown, Co-IP, and dominant-negative R555E in NGF-stimulated PC12 cells with neurite outgrowth readout\",\n      \"pmids\": [\"10187854\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the JAK2 docking site or quantify direct kinase stimulation\", \"Mechanism of how binding enhances outgrowth left open\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Showed that SH2B1 engagement is not limited to neurotrophin receptors by mapping its insulin receptor interaction to an activation-loop phosphotyrosine, broadening the receptor repertoire.\",\n      \"evidence\": \"In vitro binding with IR kinase domain phosphopeptides; splice-variant (gamma) characterization\",\n      \"pmids\": [\"10594240\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No cellular or in vivo confirmation in this study\", \"Functional consequence for IR signaling not yet tested\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Defined the N-terminal multimerization domain as a structural requirement for kinase enhancement and revealed isoform/paralog selectivity, answering how SH2B proteins might assemble functional units.\",\n      \"evidence\": \"Gel filtration/native PAGE for pentamer state plus deletion mutants with TrkA autophosphorylation; JAK1/2/3 isoform-selective kinase assays\",\n      \"pmids\": [\"11238898\", \"11751854\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stoichiometry at endogenous levels unresolved\", \"Distinct regulatory roles of SH2B1 vs APS on JAKs mechanistically unexplained\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identified JAK2 pTyr813 as the SH2 docking site and the JAK2/SH2B1/IRS tertiary complex as the mechanism amplifying PI3K/Akt, converting an adaptor observation into a defined molecular circuit.\",\n      \"evidence\": \"2D phosphopeptide mapping and JAK2 Y813 mutants; Co-IP, in vitro binding, and KO MEF rescue for IRS1/2 recruitment; tissue-specific KO insulin receptor readouts\",\n      \"pmids\": [\"15121872\", \"15316008\", \"15314154\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How SH2 docking allosterically increases kinase activity not resolved at atomic level\", \"Relative contributions across receptors in vivo not separated\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Connected the molecular adaptor function to physiology by showing SH2B1 is an endogenous enhancer of leptin sensitivity, and that dimerization transactivates JAK2 — explaining how loss causes obesity.\",\n      \"evidence\": \"SH2-B knockout mice with hypothalamic JAK2/STAT3/IRS2 readouts and PTP1B competition; yeast two-hybrid and concentration-dependent JAK2 kinase assays\",\n      \"pmids\": [\"16098827\", \"15767667\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cell type within hypothalamus not yet pinpointed\", \"Biphasic concentration dependence of activation not validated in vivo\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Provided structural and mutational definition of the SH2-pTyr813 interface and the dual positive/negative regulation of JAK2, resolving how one adaptor both inhibits basal and enhances activated kinase.\",\n      \"evidence\": \"2.35 A crystal structure of SH2 domain with JAK2 pTyr813 peptide; JAK2 truncation/point mutants in kinase assays; biochemical SH2B1 vs APS specificity\",\n      \"pmids\": [\"16824542\", \"16914724\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of full-length protein or kinase complex not determined\", \"Conformational basis of inhibitory contact not visualized\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Localized the metabolically essential pool of SH2B1 to neurons via genetic rescue, and dissected the two-mode JAK2 regulation in cells, establishing where and how SH2B1 controls energy balance.\",\n      \"evidence\": \"Neuron-specific transgenic rescue of KO mice with metabolic phenotyping; JAK2 Y813F and SH2B1 domain mutants by Co-IP; SH2B2beta inhibitory isoform pulldowns\",\n      \"pmids\": [\"17235396\", \"17565041\", \"17204555\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific neuronal population not defined\", \"Endogenous role of inhibitory SH2B2beta isoform in vivo untested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Separated the peripheral, insulin-sensitizing arm of SH2B1 function and showed direct stimulation of the insulin receptor plus protection of IRS proteins from phosphatases, refining the in vivo division of labor.\",\n      \"evidence\": \"Tissue-specific TgKO mice on high-fat diet; reconstituted in vitro IR kinase and dephosphorylation assays with purified SH2B1 and domain mutants\",\n      \"pmids\": [\"19542202\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Phosphatases protected against not identified\", \"Relative weight of central vs peripheral contribution to glucose control not quantified\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defined the downstream physiological circuit (SNS/BAT/thermogenesis) and showed the SH2 domain is required in vivo, linking the molecular docking mechanism to whole-organism thermogenic output.\",\n      \"evidence\": \"LepR-neuron-specific KO and hypothalamic AAV overexpression with sympathetic nerve recording; SH2-domain mutant (R555E) transgenic rescue and dominant-negative metabolic phenotyping\",\n      \"pmids\": [\"32251290\", \"20484460\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular targets coupling neuronal SH2B1 to SNS output not identified\", \"How dominant-negative R555E acts at endogenous loci unclear\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Extended SH2B1 function to beta-cell survival, insulin secretion, and lipid/VLDL metabolism, and identified an IRS2 stabilization mechanism, broadening its metabolic mechanism beyond signal amplification.\",\n      \"evidence\": \"Pancreas- and hepatocyte-specific KO mice; INS-1 knockdown/overexpression; insulin promoter-luciferase and Pdx1 ChIP; SH2B1/IRS2/JAK2 complex Co-IP and IRS2 ubiquitination assay; Drosophila Lnk epistasis and FRET\",\n      \"pmids\": [\"24150605\", \"24645678\", \"24358267\", \"27217487\", \"23590848\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ubiquitin ligase acting on IRS2 not identified\", \"Tissue-specific mechanisms not unified into a single model\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Resolved domain- and isoform-specific control of SH2B1, including the inhibitory alpha tail and PH domain requirement, explaining how splice variants tune adaptor output.\",\n      \"evidence\": \"Tyr753 alpha-tail mutant analysis in PC12 cells; PH-domain knockin mice (P322S, deltaPR) with metabolic phenotyping; high-resolution SH2 structure with ITC\",\n      \"pmids\": [\"29229648\", \"31439647\", \"29127727\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"PH domain ligand/lipid specificity not defined\", \"How conformational plasticity selects ligands in cells untested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Uncovered kinase-independent and non-metabolic mechanisms — Schwann cell myelination via cytohesin-2 phosphorylation, HSC70-dependent PLIN4 degradation, and nucleolar isoform targeting — expanding SH2B1 beyond receptor signaling.\",\n      \"evidence\": \"Schwann cell-specific KD and cytohesin-2 Y381F knockin mice with Arf6 assays; SH2B1-HSC70 Co-IP and PLIN4 lysosomal/MPTP models; isoform rescue in KO neurons with nucleolar localization mapping\",\n      \"pmids\": [\"35077201\", \"35390677\", \"35019135\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How SH2B1 directs cytohesin-2 phosphorylation mechanistically unclear\", \"Function of nucleolar SH2B1delta localization not defined\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Demonstrated cell-type-specific behavioral roles, with hippocampal inhibitory-neuron SH2B1 acting as a negative ERK regulator controlling cognition, refining context-dependent signaling outputs.\",\n      \"evidence\": \"Cell-type-specific Sh2b1 KO with behavioral battery, single-cell profiling, and ERK-inhibitor pharmacological rescue\",\n      \"pmids\": [\"38434247\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct molecular substrate linking SH2B1 to ERK suppression unidentified\", \"Reconciliation with SH2B1's positive role on ERK in neurotrophin signaling unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How SH2B1 isoform composition, domain conformation, and ligand selection are integrated to produce opposite (activating vs inhibitory) outputs across tissues and receptors remains the central open question.\",\n      \"evidence\": null,\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No full-length structure showing both activating and inhibitory contacts simultaneously\", \"Switch determining positive vs negative kinase regulation in vivo undefined\", \"Direct substrates/effectors for non-canonical roles (chromatin, nucleolus) not mapped\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 4, 6, 7, 30]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [3, 4, 6, 11, 24]},\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [36]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [16, 17, 30]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [17, 34]},\n      {\"term_id\": \"GO:0005730\", \"supporting_discovery_ids\": [34]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [17]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 2, 3, 7]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [5, 6, 22, 42]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [7, 30, 33, 43]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"JAK2\", \"IRS1\", \"IRS2\", \"TrkA\", \"FGFR3\", \"EPOR\", \"IRSp53\", \"HSPA8\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}