{"gene":"IRS2","run_date":"2026-04-28T18:06:54","timeline":{"discoveries":[{"year":1995,"finding":"IRS-2 (originally called 4PS) was identified as a second IRS-signaling protein that acts as an interface between signaling proteins with SH2 domains and the receptors for insulin, IGF-1, and several interleukins (IL-4, IL-9, IL-13). It contains a conserved N-terminal pleckstrin-homology domain and phosphotyrosine-binding domain.","method":"Protein purification and cloning from myeloid progenitor cells; sequence alignment with IRS-1","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 — original cloning and purification, foundational discovery replicated across labs","pmids":["7675087"],"is_preprint":false},{"year":1995,"finding":"IRS-2 (4PS) is the primary alternative substrate of the insulin receptor in IRS-1-deficient mice. Following insulin stimulation, IRS-2 is phosphorylated, binds the p85 subunit of PI 3-kinase activating it, and associates with Grb2 in liver and muscle.","method":"Immunoprecipitation, immunoblotting, and PI 3-kinase assays using specific antibodies in IRS-1-deficient mice; immunodepletion experiments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — reciprocal immunoprecipitation, PI3K activity assays, immunodepletion in vivo","pmids":["7559579"],"is_preprint":false},{"year":1997,"finding":"Serine/threonine phosphorylation of IRS-2 (induced by TNFα, sphingomyelinase, or chronic insulin) impairs its interaction with the juxtamembrane domain of the insulin receptor (amino acids 943-984), thereby inhibiting insulin-induced tyrosine phosphorylation of IRS-2 and propagation of the insulin signal.","method":"In vitro binding assays using His6-fusion peptides of IR domains; treatment of Fao cells with TNFα and alkaline phosphatase reversal experiments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro binding reconstitution with mutagenic and enzymatic (phosphatase) validation","pmids":["9368067"],"is_preprint":false},{"year":1997,"finding":"IRS-1 and IRS-2 undergo differential tyrosine phosphorylation and downstream signaling during insulin or IL-4 stimulation. IRS-2 predominates in hematopoietic cells; IRS-1 predominates in adipocytes. Distinct phosphorylation patterns during receptor interaction determine signaling specificity.","method":"Interaction with recombinant SH2 domain fusion proteins; differential expression analysis in cell lines","journal":"Molecular endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple cell types examined, SH2-domain pull-downs, single lab","pmids":["9013772"],"is_preprint":false},{"year":1997,"finding":"IRS-1 and IRS-2 are not functionally interchangeable for IGF-1-stimulated mitogenesis despite both activating PI 3-kinase. IRS-1 (but not IRS-2) is required for cell cycle progression (S-phase entry), while IRS-2 overexpression can restore PI 3-kinase activation and immediate-early gene expression to the same degree as IRS-1.","method":"Retroviral gene transduction into IRS-1-deficient cells; mitogenesis, PI 3-kinase, and immediate-early gene assays","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — reconstitution by retroviral expression with multiple orthogonal functional readouts","pmids":["9032279"],"is_preprint":false},{"year":1998,"finding":"IRS-2 is differentially compartmentalized relative to IRS-1 in adipocytes: IRS-2 is concentrated 2-fold more in cytosol than in intracellular membranes (IM), whereas IRS-1 is enriched in IM. Insulin-stimulated tyrosine phosphorylation of IRS-2 occurs mainly in IM despite its cytosolic localization. After insulin stimulation, both IRS-1 and IRS-2 translocate from IM to cytosol. IRS-2-mediated PI 3-kinase signaling is more transient than IRS-1-mediated signaling.","method":"Subcellular fractionation, immunoblotting, in vitro reconstitution assay in 3T3-L1 adipocytes","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — subcellular fractionation combined with in vitro reconstitution assay; multiple time-point kinetics","pmids":["9565570"],"is_preprint":false},{"year":1998,"finding":"In fetal brown adipocytes, both IRS-1 and IRS-2 associate with p85α and activate PI 3-kinase in response to insulin/IGF-1, but only IRS-1 (not IRS-2) associates with Grb2 and links to the Ras-MAPK pathway, as shown by pull-down with GST-Grb2-SH2 and competition with a phosphopeptide containing pTyr895.","method":"GST-SH2 domain pull-down experiments, immunoprecipitation, phosphopeptide competition assays in fetal brown adipocytes","journal":"Molecular endocrinology","confidence":"High","confidence_rationale":"Tier 1-2 — GST pull-down with SH2 domains plus phosphopeptide competition defining the molecular basis for differential signaling","pmids":["9605931"],"is_preprint":false},{"year":1999,"finding":"Irs-2 coordinates Igf-1 receptor-mediated beta-cell development and peripheral insulin signaling in vivo. Irs-2 has the major role in beta-cell development and compensation for peripheral insulin resistance; intercross with Igf1r heterozygotes revealed that Igf-1 receptors promote beta-cell development through the Irs-2 signaling pathway.","method":"Genetic intercross of Irs1+/- and Irs2+/- mice; intercross with Igf1r+/- mice; metabolic phenotyping","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis in multiple mouse models with defined phenotypic readouts","pmids":["10471495"],"is_preprint":false},{"year":2000,"finding":"Chronic hyperinsulinemia downregulates IRS-2 mRNA in liver, producing insulin resistance in gluconeogenesis. Despite IRS-2 deficiency, insulin continues to stimulate SREBP-1c production, establishing a 'mixed' insulin resistance/sensitivity that aggravates hyperinsulinemia.","method":"Analysis of lipodystrophic and ob/ob mouse livers; mRNA expression and signaling pathway analysis","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 — two independent mouse models, replicated mechanistic finding","pmids":["10949029"],"is_preprint":false},{"year":2000,"finding":"Deletion of IRS-2 causes female infertility due to small, anovulatory ovaries and reduced pituitary gonadotrophs, demonstrating IRS-2 integrates reproductive and energy homeostasis signals.","method":"Irs2 knockout mouse phenotypic analysis including hormonal measurements, pituitary size, and ovarian histology","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 — clean KO with specific reproductive phenotypic readouts including tissue morphology and hormone levels","pmids":["11014193"],"is_preprint":false},{"year":2001,"finding":"IRS-2 mediates IGF-I-stimulated breast cancer cell migration in metastatic variants; antisense reduction of IRS-2 diminishes IGF-mediated motility and anchorage-independent growth, defining IRS-2 as a positive regulator of breast cancer cell motility.","method":"Antisense IRS-2 transfection, IGF-I stimulation, migration and anchorage-independent growth assays","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 — loss-of-function with specific cellular phenotype, single lab","pmids":["11704861"],"is_preprint":false},{"year":2001,"finding":"IRS-1 and IRS-2 together are essential for adipocyte differentiation. Double-knockout of IRS-1 and IRS-2 completely abolishes adipocyte differentiation, PI 3-kinase activity during differentiation, and expression of C/EBPα and PPARγ.","method":"Mouse embryonic fibroblasts with four genotypes (WT, IRS-1-/-, IRS-2-/-, double KO); adipocyte differentiation assays, PI 3-kinase activity, gene expression","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — clean double KO with multiple orthogonal readouts, validated in vivo in newborn mice","pmids":["11259600"],"is_preprint":false},{"year":2002,"finding":"SOCS1 and SOCS3 bind IRS-1 and IRS-2 and promote their ubiquitin-mediated degradation via the elongin BC ubiquitin-ligase complex. Mutations in the SOCS box of SOCS1 abrogate interaction with elongin BC without affecting IRS binding, and eliminate ubiquitination/degradation of IRS proteins.","method":"Co-immunoprecipitation of endogenous and recombinant proteins; ubiquitination assays; SOCS box mutants; adenoviral expression in mouse liver","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, domain mutagenesis, in vivo adenoviral validation, multiple cell types","pmids":["12228220"],"is_preprint":false},{"year":2002,"finding":"Pdx1 expression is reduced in islets from Irs2-/- mice before diabetes onset. Transgenic overexpression of Pdx1 restores beta-cell mass and function in Irs2-/- mice, preventing diabetes, demonstrating IRS-2 signaling is required for maintaining Pdx1 expression in beta-cells.","method":"Irs2-/- mouse islet analysis; Pdx1 transgenic rescue; genetic epistasis with Pdx1 haploinsufficiency","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — bidirectional genetic epistasis, loss and gain of function","pmids":["11994408"],"is_preprint":false},{"year":2002,"finding":"IRS-2 and Stat6 cooperate in IL-4-induced T cell proliferation and Th2 differentiation. IRS-2 deficiency compromises IL-4-induced proliferation (through co-regulation of p27kip1) and Th2 cytokine secretion, but both Stat6 and IRS-2 are dispensable for IL-4-induced survival.","method":"T cells from Stat6-/-, Irs2-/-, and double-deficient mice; proliferation, cytokine secretion, and apoptosis assays","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis in primary lymphocytes, multiple functional readouts","pmids":["11739727"],"is_preprint":false},{"year":2003,"finding":"cAMP promotes pancreatic beta-cell survival via CREB-mediated transcriptional induction of IRS2. CREB directly targets the IRS2 promoter in vivo; IRS2 induction by cAMP enhances Akt activation in response to insulin/IGF-1.","method":"A-CREB dominant-negative transgenic mice; chromatin immunoprecipitation; cAMP/IRS2/Akt signaling assays in islets","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 — transgenic loss-of-function, ChIP showing direct promoter binding, downstream signaling validation","pmids":["12842910"],"is_preprint":false},{"year":2005,"finding":"Hepatic IRS-1 is linked preferentially to glucose homeostasis (gluconeogenesis suppression) while IRS-2 is linked to lipid metabolism (SREBP-1c/fatty acid synthase regulation) in liver. Combined knockdown causes defective Akt activation and Foxo1 phosphorylation with systemic insulin resistance.","method":"Adenovirus-mediated shRNA knockdown of IRS-1, IRS-2, or both in mouse liver; gene expression, metabolic, and signaling analyses","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — in vivo isoform-specific knockdown with complementary functional readouts","pmids":["15711641"],"is_preprint":false},{"year":2005,"finding":"TFE3 (a bHLH transcription factor) directly transactivates IRS-2 expression via E-box elements in the IRS-2 promoter, leading to enhanced Akt signaling and reduced plasma glucose.","method":"Expression cloning; adenoviral TFE3 expression in hepatocytes and in vivo; IRS-2 promoter analysis","journal":"Nature medicine","confidence":"High","confidence_rationale":"Tier 2 — expression cloning plus in vivo validation plus promoter analysis, multiple diabetes models","pmids":["16327801"],"is_preprint":false},{"year":2005,"finding":"Exendin-4 (GLP-1 receptor agonist) increases cAMP in beta cells, which promotes IRS-2 expression and Akt phosphorylation. Long-term beta-cell mass expansion by Ex4 requires IRS-2 signaling, as Ex4 fails to arrest beta-cell loss in Irs2-/- mice.","method":"cAMP measurement, IRS-2 expression, Akt phosphorylation in human islets and Min6 cells; Ex4 treatment of Irs2-/- mice","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — mechanism defined in vitro validated in Irs2 KO mice in vivo","pmids":["16272563"],"is_preprint":false},{"year":2005,"finding":"Deletion of both hepatic Irs1 and Irs2 abolishes Akt-FoxO1 pathway signaling in liver, causing hyperglycemia and upregulation of gluconeogenic genes (Pck1, G6pc, Ppargc1). Irs2 alone or Irs1 alone in liver is sufficient to maintain near-normal glucose homeostasis.","method":"Liver-specific Irs2 knockout (LKO) on Irs1-/- background; signaling pathway analysis, gene expression profiling","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — conditional double KO with comprehensive signaling and gene expression analysis","pmids":["16374520"],"is_preprint":false},{"year":2006,"finding":"IRS-2 is a substrate of the TrkA receptor and the TRK-T1 oncogene. IRS-2 tyrosine phosphorylation by TrkA/TRK-T1 leads to recruitment of p85-PI3K, SHP-2, and Grb2 and increased PI 3-kinase activity. Direct interaction between TRK and IRS-2 was demonstrated by yeast two-hybrid.","method":"Co-immunoprecipitation, PI 3-kinase activity assays, yeast two-hybrid","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 2 — yeast two-hybrid for direct interaction plus Co-IP and functional assays","pmids":["11147812"],"is_preprint":false},{"year":2006,"finding":"FoxO1 and IRS-2 form a reciprocal stability circuit: Irs2 signaling promotes FoxO1 nuclear exclusion and degradation; loss of Irs2 increases FoxO1 stability. Conversely, FoxO1 transcription drives IRS-2 expression. Rapamycin inhibits Irs2 degradation and causes persistent FoxO1 degradation.","method":"Mouse embryo fibroblasts from Irs1-/- and Irs2-/- mice; protein stability assays; rapamycin treatment; PI 3-kinase and Akt activation measurements","journal":"Molecular endocrinology","confidence":"High","confidence_rationale":"Tier 2 — multiple genetic backgrounds, pharmacological validation, bidirectional regulation demonstrated","pmids":["16916938"],"is_preprint":false},{"year":2006,"finding":"IRS-2 expression in pancreatic beta-cells is specifically regulated by glucose at the transcriptional level in a dose-dependent, Ca2+-dependent manner. Glucose-induced IRS-2 upregulation correlates with increased IRS-2 tyrosine phosphorylation and Akt activation, promoting beta-cell survival.","method":"IRS-2 mRNA/protein expression kinetics in isolated rat islets; glucose dose-response; intracellular Ca2+ inhibition experiments; Akt phosphorylation assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — primary beta cells, pharmacological dissection of Ca2+ requirement, multiple readouts","pmids":["16574657"],"is_preprint":false},{"year":2006,"finding":"IRS-2 overexpression in mammary gland causes progressive hyperplasia and tumorigenesis. IRSs bind β-catenin in vitro and in vivo, and IRS-2 overexpression causes constitutive phosphorylation and mammary tumors with squamous differentiation consistent with β-catenin pathway activation.","method":"Transgenic mice with mammary-specific IRS-1 or IRS-2 overexpression; Co-IP of β-catenin with IRS proteins in vitro and in vivo","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — transgenic in vivo tumorigenesis plus Co-IP demonstrating β-catenin interaction","pmids":["17030631"],"is_preprint":false},{"year":2006,"finding":"The IRS2-Akt signaling pathway in VTA dopamine neurons is downregulated by chronic morphine, mediating the decrease in dopamine cell size and diminishing morphine reward (conditioned place preference). Viral-mediated manipulation of IRS2-Akt in VTA established causal roles.","method":"Viral-mediated gene transfer to rat VTA; conditioned place preference; dopamine cell morphometry; chronic morphine pellet administration","journal":"Nature neuroscience","confidence":"High","confidence_rationale":"Tier 2 — viral gain/loss of function in specific brain region with defined behavioral and cellular readouts","pmids":["17143271"],"is_preprint":false},{"year":2007,"finding":"Brain-specific Irs2 knockout in mice extends lifespan up to 18%, reduces meal-induced hypothalamic oxidative stress (stable SOD2), and maintains greater glucose oxidation, identifying brain IRS2 as a regulator of longevity and nutrient homeostasis.","method":"Brain-specific Irs2 conditional knockout mice; lifespan measurement; metabolic cage studies; hypothalamic SOD2 measurement","journal":"Science","confidence":"High","confidence_rationale":"Tier 2 — tissue-specific KO with quantitative lifespan and metabolic phenotype","pmids":["17641201"],"is_preprint":false},{"year":2008,"finding":"Phosphotyrosine interactome mapping of IRS-2 identified phosphorylation-specific interaction partners for multiple tyrosine sites, including shared partners with IRS-1 and several differential interactors. IRS-2 shows different combinatorial phosphorylation effects and differential binding of SHP2 compared to IRS-1.","method":"SILAC-based quantitative interaction proteomics with phosphorylated vs. non-phosphorylated bait peptides","journal":"Molecular & cellular proteomics","confidence":"High","confidence_rationale":"Tier 2 — comprehensive MS-based phosphotyrosine interactome with quantitative SILAC","pmids":["19001411"],"is_preprint":false},{"year":2008,"finding":"IRS-2 deficiency impairs appropriate timing of myelination in vivo; IRS-2-/- mice show reduced myelin protein expression at postnatal day 10. Compensatory IRS-1 upregulation and increased IGF-1R signaling occur in IRS-2-/- brains, demonstrating IGF-1R/IRS-2 signals are critical for myelination timing.","method":"IRS-2-/- mice; myelin protein expression by Western blot/immunostaining; cerebral myelin isolation; compensatory IRS-1 analysis","journal":"Journal of neurochemistry","confidence":"High","confidence_rationale":"Tier 2 — clean KO with specific developmental phenotype and compensation mechanism identified","pmids":["18717815"],"is_preprint":false},{"year":2009,"finding":"Deletion of Irs2 in APP transgenic mice reduces amyloid-β deposition, increases transthyretin (an Aβ-binding clearance protein), and rescues behavioral deficits, while increasing tau phosphorylation (reduced tau-phosphatase PP2A despite inhibited GSK-3). This reveals divergent effects of IRS2 on amyloid vs. tau pathology.","method":"Genetic cross of Tg2576 APP mice with Irs2-/- mice; amyloid plaque quantification; tau phosphorylation; transthyretin and PP2A/GSK-3 analysis; behavioral testing","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with multiple biochemical and behavioral readouts","pmids":["19523444"],"is_preprint":false},{"year":2009,"finding":"In IRS2-/- mice, hepatic PTP1B expression and its association with the insulin receptor are increased. Double knockout of IRS2 and PTP1B restores IRS1-mediated PI 3-kinase/Akt/Foxo1 signaling in liver, improving glucose tolerance. PTP1B determines insulin receptor phosphorylation state and interplay between IRS1 and IRS2.","method":"IRS2-/-/PTP1B-/- double-knockout mice; hepatic insulin signaling analysis; isolated hepatocyte experiments; resveratrol pharmacological inhibition","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 — genetic and pharmacological epistasis, mechanistic pathway delineation","pmids":["20028942"],"is_preprint":false},{"year":2010,"finding":"IRS-2 is phosphorylated at Ser675 by mTOR and at Ser907 by ERK1/2 following insulin stimulation. Ser675 phosphorylation accelerates IRS-2 protein degradation (mTOR-mediated negative feedback); Ser907 phosphorylation does not impair Grb2 association but affects adjacent Tyr911 phosphorylation.","method":"Monoclonal phosphosite-specific antibodies; siRNA knockdown of ERK1/2 and mTOR; Ala mutant IRS-2 expression in HEK293 cells; protein half-life measurement","journal":"American journal of physiology. Endocrinology and metabolism","confidence":"High","confidence_rationale":"Tier 1 — site-specific mutagenesis, siRNA knockdown of individual kinases, phosphosite-specific antibody validation","pmids":["21098738"],"is_preprint":false},{"year":2011,"finding":"IRS-2 deficiency impairs NMDA receptor-dependent LTP in hippocampus. During LTP induction, IRS2 is tyrosine-phosphorylated. In Irs2-/- mice, tetanus stimulation fails to activate Fyn, AKT, and MAPK, and NMDA receptor activation is defective, despite normal NR2A, NR2B, and PSD95 expression.","method":"Hippocampal slice electrophysiology (LTP recordings); Western blot for Fyn/AKT/MAPK phosphorylation; IRS2 phosphorylation during LTP in control mice","journal":"Cerebral cortex","confidence":"High","confidence_rationale":"Tier 2 — clean KO with specific electrophysiological and biochemical readouts, IRS2 phosphorylation measured during LTP","pmids":["21955917"],"is_preprint":false},{"year":2011,"finding":"Increasing Irs2 levels in brains of R6/2 Huntington disease mice worsens neuronal oxidative stress and mitochondrial dysfunction; reducing Irs2 improves motor performance, extends lifespan, and increases nuclear FoxO1 and autophagy. Thus IRS2 signaling modulates HD progression through FoxO1-dependent autophagy.","method":"Genetic modulation of Irs2 in R6/2 mice; FoxO1 localization; autophagosome counting; oxidative stress and mitochondrial function assays","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — bidirectional genetic modulation with multiple mechanistic readouts","pmids":["21926467"],"is_preprint":false},{"year":2012,"finding":"Cardiac-specific deletion of IRS1 and IRS2 causes dilated cardiomyopathy with reduced Akt→FoxO1 signaling, cardiac apoptosis, and fibrosis. Hyperinsulinemia reduces IRS1/2 in cardiomyocytes via p38α MAPK activation, identifying p38α as a mediator of cardiac insulin resistance.","method":"Heart-specific IRS1/2 double-knockout mice; neonatal cardiomyocyte experiments with chronic insulin exposure; p38 inhibition","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 — organ-specific KO with molecular mechanism via p38α identified in primary cells and in vivo","pmids":["24159000"],"is_preprint":false},{"year":2013,"finding":"IRS2 is phosphorylated during caffeine-induced LTP (CAF LTP) in hippocampal CA1 in a Ca2+-dependent manner. Akt phosphorylation during CAF LTP is defective in Irs2-/- mice, demonstrating TrkB-IRS2-PI3K signaling is required for this form of synaptic plasticity.","method":"Hippocampal slice recordings; IRS2 phosphorylation measurement; Irs2-/- mice; Ca2+ chelation experiments","journal":"Addiction biology","confidence":"Medium","confidence_rationale":"Tier 2 — clean KO with electrophysiology and biochemical validation, single lab","pmids":["27457910"],"is_preprint":false},{"year":2013,"finding":"IRS2 is a major substrate and signaling node downstream of oncogenic ALK in neuroblastoma. ALK TKI treatment reduces IRS2 recruitment to ALK and IRS2 tyrosine phosphorylation. IRS2 links ALK to the Akt-FoxO3 survival axis; siRNA depletion of IRS2 or ALK reduces Akt/FoxO3 phosphorylation and cell viability.","method":"Integrated proximal proteomics (ALK interactome, phosphotyrosine interactome, phosphoproteome); siRNA depletion; ALK TKI treatment","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 2 — comprehensive MS-based interactome plus siRNA loss-of-function, multiple readouts","pmids":["30459283"],"is_preprint":false},{"year":2013,"finding":"HIF-2α directly or indirectly induces IRS-2 expression in liver, sensitizing hepatic insulin signaling. Liver IRS-2 is both necessary and sufficient to mediate HIF-2α and VEGF inhibitor effects on glucose tolerance and hepatic insulin signaling including gluconeogenic gene suppression.","method":"Liver-specific constitutive HIF-2α activation; IRS-2 knockout rescue experiments; VEGF inhibitor treatment in diabetic mice","journal":"Nature medicine","confidence":"High","confidence_rationale":"Tier 2 — constitutive activation and genetic epistasis demonstrating IRS2 is necessary and sufficient","pmids":["24037094"],"is_preprint":false},{"year":2014,"finding":"Insulin stimulates GRK2 recruitment to β2AR via IRS2, inducing β2AR phosphorylation at GRK sites (Ser355/356) and receptor internalization. IRS2 deletion disrupts the IR-GRK2 complex, attenuates β2AR phosphorylation and internalization, and abrogates insulin's counter-regulation of βAR signaling in cardiomyocytes.","method":"Co-immunoprecipitation of IR-GRK2 complex; IRS2 KO cardiomyocytes; β2AR phosphorylation and internalization assays; cAMP-PKA activity measurements","journal":"Cellular signalling","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP with functional KO validation, multiple readouts","pmids":["25460042"],"is_preprint":false},{"year":2015,"finding":"Nedd4 is an E3 ubiquitin ligase for IRS-2 that monoubiquitinates IRS-2, promoting its association with Epsin1 and recruitment to the plasma membrane. Membrane recruitment enhances IGF-1 receptor-induced IRS-2 tyrosine phosphorylation and downstream signaling and mitogenesis.","method":"Co-IP; ubiquitination assays; Nedd4 overexpression; Epsin1 binding assays; zebrafish embryo growth experiments; prostate cancer cell proliferation","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — E3 ligase identification with Co-IP, ubiquitination assays, in vivo zebrafish validation","pmids":["25879670"],"is_preprint":false},{"year":2015,"finding":"FSH specifically induces IRS-2 expression in granulosa cells via the cAMP pathway and SP1 transcription factor binding to IRS-2 promoter SP1 sites. FSH stimulates SP1 nuclear translocation and IRS-2 promoter binding. IRS-2 mediates FSH-stimulated PI3K activity, Akt phosphorylation, GLUT4 translocation and glucose uptake in granulosa cells.","method":"IRS-2 promoter analysis; siRNA knockdown; chromatin immunoprecipitation; SP1 nuclear translocation imaging; GLUT4 translocation assay","journal":"Cellular signalling","confidence":"High","confidence_rationale":"Tier 2 — promoter analysis with ChIP, siRNA knockdown, multiple downstream functional readouts","pmids":["26388164"],"is_preprint":false},{"year":2016,"finding":"JAK2V617F (oncogenic JAK2) directly binds IRS2 in MPN cells; IRS2 silencing decreases STAT5 phosphorylation, reduces viability and increases apoptosis in JAK2V617F cells but not JAK2WT cells, demonstrating IRS2 as a binding partner and survival node specific to mutant JAK2 signaling.","method":"Co-immunoprecipitation of JAK2/IRS2; siRNA silencing; viability and apoptosis assays in MPN cell lines and primary patient samples","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP plus siRNA functional validation in cell lines and primary samples","pmids":["26755644"],"is_preprint":false},{"year":2018,"finding":"YAP/TAZ transcriptional activity in liver upregulates IRS2 expression, amplifying AKT signaling. Knockout of IRS2 by AAV-Cas9 represses liver tumorigenesis in Pten-/-/Sav1-/- mice, placing IRS2 downstream of Hippo/YAP-TAZ signaling as a driver of hepatocellular carcinoma.","method":"Genetic mouse models (Pten/Sav1 double KO); AAV-Cas9 IRS2 knockout; IRS2 expression correlation with YAP/TAZ in human HCC","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — in vivo genetic epistasis with AAV-Cas9 and multiple mouse models","pmids":["29400692"],"is_preprint":false},{"year":2018,"finding":"Hyperinsulinemia downregulates macrophage IRS2 expression via the insulin receptor, impairing the IL-4/IRS2/Akt pathway and M2a-subtype macrophage activation. This impairment stabilizes the FoxO1/HDAC3/NCoR1 corepressor complex and leads to systemic insulin resistance under high-fat diet.","method":"Myeloid cell-specific Irs2 and IR knockout mice; macrophage activation assays; FoxO1/HDAC3/NCoR1 complex analysis","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — cell-type-specific KO, molecular complex identified, in vivo metabolic validation","pmids":["30451856"],"is_preprint":false},{"year":2019,"finding":"PGC1A drives IRS2 expression downstream of glucagon/cAMP/CREB signaling in hepatocytes while simultaneously reducing IRS1 expression, controlling the IRS1:IRS2 ratio during fasting. PGC1A-induced IRS2 is essential for insulin-mediated suppression of gluconeogenesis.","method":"Gain- and loss-of-function models in primary hepatocytes; protein and gene expression; ex vivo glucose production; in vivo PGC1A overexpression","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — bidirectional gain/loss of function, CREB dependence shown, multiple functional readouts","pmids":["30770439"],"is_preprint":false},{"year":2021,"finding":"IRS-2 is recruited into mutant huntingtin (mHTT) aggregates in pancreatic beta-cells, reducing PI3K/AKT/FoxO1 pathway activation and impairing glucose-stimulated insulin secretion and cell proliferation. Insulin treatment inhibits mHTT aggregation and restores PI3K/AKT/FoxO1 signaling.","method":"NIT-1 cells expressing N-terminal mHTT (160Q); co-localization of IRS-2 with mHTT aggregates; PI3K/AKT/FoxO1 signaling assays; insulin rescue experiments","journal":"Journal of molecular neuroscience","confidence":"Medium","confidence_rationale":"Tier 3 — single lab, cell line model, co-localization without direct Co-IP validation","pmids":["34331233"],"is_preprint":false},{"year":2022,"finding":"IRS2-PI3K signaling stabilizes MYC in breast cancer stem cells by inhibiting GSK3β, suppressing MYC phosphorylation at Thr58, and reducing proteasomal degradation of MYC. A T58A-Myc mutant rescues CSC function in Irs2-/- cells.","method":"IRS2 knockout in breast cancer cells; GSK3β activity assays; MYC phosphorylation at Thr58; T58A-Myc mutant rescue; stem cell functional assays","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1-2 — mutagenesis rescue (T58A-Myc), biochemical pathway dissection, GSK3β link established","pmids":["36476848"],"is_preprint":false}],"current_model":"IRS2 is a cytoplasmic scaffold/adaptor protein phosphorylated on tyrosine by the insulin receptor (and IGF-1R, cytokine receptors, ALK, TrkA) at the juxtamembrane domain, whereupon it recruits and activates PI3K (p85/p110α), leading to Akt activation and downstream regulation of FoxO1, mTOR, GSK3β, and MYC; its activity is positively modulated by Nedd4-mediated monoubiquitination (membrane recruitment), CREB/TFE3/FoxO3a/HIF-2α/PGC1A-driven transcription, and cAMP/GLP-1 signaling, while it is negatively regulated by serine phosphorylation via ERK1/2 (Ser907), mTOR (Ser675), and other feedback kinases causing degradation, and by SOCS1/3-elongin BC-mediated ubiquitin-proteasomal degradation; tissue-specifically, IRS2 is the dominant adaptor for beta-cell survival and proliferation, hepatic gluconeogenesis suppression, VTA dopamine neuron morphology, hippocampal LTP, macrophage M2a polarization, female reproduction, and myelination timing."},"narrative":{"teleology":[{"year":1995,"claim":"Identification of IRS-2 as a second insulin receptor substrate with PH and PTB domains established that insulin/IGF-1/cytokine signaling operates through a family of adaptor proteins rather than solely through IRS-1.","evidence":"Protein purification and cloning from myeloid progenitor cells; reciprocal IP and PI3K assays in IRS-1-deficient mice","pmids":["7675087","7559579"],"confidence":"High","gaps":["Three-dimensional structure of full-length IRS-2 undetermined","Relative stoichiometry of IRS-1 vs IRS-2 at the insulin receptor not quantified"]},{"year":1997,"claim":"Demonstration that serine/threonine phosphorylation of IRS-2 blocks its binding to the insulin receptor juxtamembrane domain revealed the molecular basis of TNFα- and chronic-insulin-induced insulin resistance at the IRS-2 level.","evidence":"In vitro binding assays with His6-tagged IR domains; TNFα treatment and alkaline phosphatase reversal in Fao cells","pmids":["9368067"],"confidence":"High","gaps":["Specific serine residues mediating TNFα-induced inhibition not mapped in this study","Kinase(s) responsible for inhibitory serine phosphorylation not identified here"]},{"year":1997,"claim":"Showing that IRS-1 and IRS-2 are not functionally interchangeable for IGF-1-driven mitogenesis — IRS-2 restores PI3K but not cell cycle progression — defined substrate-specific signaling outputs.","evidence":"Retroviral reconstitution in IRS-1-deficient cells; SH2-domain pull-downs across cell types","pmids":["9032279","9013772"],"confidence":"High","gaps":["Molecular determinant on IRS-1 that uniquely drives S-phase entry not identified","Differential phosphosite usage between IRS-1 and IRS-2 not fully mapped"]},{"year":1998,"claim":"Subcellular fractionation revealed that IRS-2 is predominantly cytosolic yet phosphorylated at intracellular membranes, with more transient PI3K signaling than IRS-1, establishing compartmentalization as a mechanism for signaling specificity.","evidence":"Subcellular fractionation and in vitro reconstitution in 3T3-L1 adipocytes; GST-SH2 pull-downs in brown adipocytes","pmids":["9565570","9605931"],"confidence":"High","gaps":["Mechanism driving IRS-2 membrane translocation not determined","Whether compartmentalization differs across cell types not systematically tested"]},{"year":1999,"claim":"Genetic epistasis in Irs2-haploinsufficient and Igf1r-haploinsufficient mice proved IRS-2 is the dominant adaptor coordinating IGF-1R-mediated β-cell development and compensation for insulin resistance, distinguishing its role from IRS-1.","evidence":"Intercross of Irs1+/-, Irs2+/-, and Igf1r+/- mice with metabolic phenotyping","pmids":["10471495"],"confidence":"High","gaps":["IRS-2-specific downstream transcriptional programs in β-cells not characterized","Whether IRS-2 is required cell-autonomously in β-cells not yet resolved at this stage"]},{"year":2000,"claim":"Discovery that IRS-2 knockout causes female infertility (anovulatory ovaries, reduced gonadotrophs) and that hepatic IRS-2 is transcriptionally downregulated by hyperinsulinemia broadened IRS-2 biology beyond metabolism to reproduction and established a 'mixed resistance' model in liver.","evidence":"Irs2 knockout reproductive phenotyping; mRNA analysis in lipodystrophic and ob/ob mouse livers","pmids":["11014193","10949029"],"confidence":"High","gaps":["Mechanism of IRS-2 transcriptional repression by chronic insulin not identified","Cell-autonomous role in pituitary gonadotrophs vs. ovarian cells not dissected"]},{"year":2002,"claim":"Identification of SOCS1/3–elongin BC as the E3 ligase complex mediating IRS-2 ubiquitin-proteasomal degradation, and demonstration that IRS-2 sustains Pdx1 expression in β-cells (rescued by Pdx1 transgene), defined both a key negative regulator and a critical transcriptional target of IRS-2 signaling.","evidence":"SOCS box mutagenesis and ubiquitination assays; Irs2-/-/Pdx1-transgenic genetic rescue; IL-4/T cell functional assays in Irs2-/- mice","pmids":["12228220","11994408","11739727"],"confidence":"High","gaps":["Specific lysine residues on IRS-2 targeted by SOCS-mediated ubiquitination not mapped","Whether SOCS-mediated degradation is the dominant pathway in β-cells not tested"]},{"year":2003,"claim":"ChIP-validated CREB binding to the IRS2 promoter established a cAMP→CREB→IRS2→Akt feed-forward circuit that explained how incretin signaling promotes β-cell survival.","evidence":"A-CREB dominant-negative transgenic mice; chromatin immunoprecipitation of IRS2 promoter; cAMP-IRS2-Akt signaling in islets","pmids":["12842910"],"confidence":"High","gaps":["Other transcription factors co-operating with CREB at the IRS2 promoter not identified","Epigenetic regulation of IRS2 promoter not addressed"]},{"year":2005,"claim":"Isoform-specific hepatic knockdown and liver-specific double knockouts established that IRS-1 and IRS-2 have partially non-overlapping hepatic roles — IRS-2 linked to SREBP-1c/lipogenesis, IRS-1 to gluconeogenesis suppression — with combined loss abolishing Akt–FoxO1 signaling. TFE3 and GLP-1/exendin-4 were identified as positive transcriptional and hormonal regulators of IRS-2.","evidence":"Adenoviral shRNA knockdown in liver; liver-specific Irs2 KO on Irs1-/- background; TFE3 adenoviral expression; exendin-4 treatment in Irs2-/- mice and human islets","pmids":["15711641","16374520","16327801","16272563"],"confidence":"High","gaps":["Whether TFE3 regulation of IRS-2 operates in extrahepatic tissues not tested","Mechanistic basis for IRS-2-specific lipogenic gene regulation not fully delineated"]},{"year":2006,"claim":"IRS-2 was shown to regulate diverse biological contexts: β-catenin-driven mammary tumorigenesis upon overexpression, VTA dopamine neuron size and morphine reward via Akt, glucose-dependent transcriptional induction in β-cells, and a reciprocal stability circuit with FoxO1.","evidence":"Mammary-specific IRS-2 transgenic mice and β-catenin Co-IP; viral IRS2/Akt manipulation in rat VTA with behavioral assays; glucose dose-response in isolated islets; Irs2-/- MEFs with rapamycin and FoxO1 stability assays","pmids":["17030631","17143271","16574657","16916938"],"confidence":"High","gaps":["Structural basis for IRS-2/β-catenin interaction unknown","Whether FoxO1–IRS-2 reciprocal circuit operates in all IRS-2-expressing tissues not tested"]},{"year":2007,"claim":"Brain-specific Irs2 deletion extended lifespan by ~18% and reduced hypothalamic oxidative stress, establishing CNS IRS-2 signaling as a determinant of organismal aging.","evidence":"Brain-specific Irs2 conditional KO mice; lifespan measurement; metabolic cage studies; SOD2 analysis","pmids":["17641201"],"confidence":"High","gaps":["Specific neuronal populations mediating lifespan effect not identified","Whether caloric restriction and IRS-2 reduction share a common mechanism not tested"]},{"year":2008,"claim":"SILAC-based phosphotyrosine interactome mapping of IRS-2 revealed site-specific interaction partners and combinatorial phosphorylation effects, while IRS-2 was shown to be required for proper myelination timing via IGF-1R signaling.","evidence":"SILAC quantitative MS with phosphopeptide baits; Irs2-/- mouse myelin protein analysis at P10","pmids":["19001411","18717815"],"confidence":"High","gaps":["Which tyrosine sites are critical for myelination signaling not identified","Oligodendrocyte-autonomous requirement for IRS-2 not demonstrated"]},{"year":2010,"claim":"Mapping mTOR-dependent Ser675 phosphorylation as a degradation signal and ERK1/2-dependent Ser907 phosphorylation as a modulator of adjacent Tyr911 defined the molecular logic of negative feedback serine phosphorylation on IRS-2.","evidence":"Phosphosite-specific monoclonal antibodies; Ala mutants; siRNA knockdown of ERK1/2 and mTOR; protein half-life in HEK293 cells","pmids":["21098738"],"confidence":"High","gaps":["Full catalog of inhibitory serine phosphorylation sites on IRS-2 not complete","In vivo significance of Ser675 and Ser907 not tested in animal models"]},{"year":2011,"claim":"IRS-2 was found to be tyrosine-phosphorylated during hippocampal LTP induction and required for NMDA receptor-dependent Fyn/Akt/MAPK activation, and separately, reducing brain IRS-2 in Huntington disease mice improved motor function via FoxO1-dependent autophagy, revealing bidirectional roles in neuronal plasticity and neurodegeneration.","evidence":"Hippocampal slice LTP recordings in Irs2-/- mice; genetic modulation of Irs2 in R6/2 HD mice with autophagosome quantification","pmids":["21955917","21926467"],"confidence":"High","gaps":["Upstream kinase phosphorylating IRS-2 during LTP not identified","Whether IRS-2 reduction benefits other polyglutamine diseases not tested"]},{"year":2013,"claim":"IRS-2 was placed downstream of ALK as a signaling node in neuroblastoma and downstream of HIF-2α in liver, expanding the receptor and transcriptional inputs that converge on IRS-2.","evidence":"Integrated proximal proteomics and siRNA in neuroblastoma cells; liver-specific HIF-2α activation with IRS-2 KO rescue","pmids":["30459283","24037094"],"confidence":"High","gaps":["Whether ALK directly phosphorylates IRS-2 or acts via an intermediary kinase not resolved","Mechanism by which HIF-2α induces IRS-2 (direct vs. indirect) not fully determined"]},{"year":2015,"claim":"Nedd4 was identified as an E3 ligase that monoubiquitinates IRS-2, promoting Epsin1-dependent plasma membrane recruitment and enhanced IGF-1R signaling — the first positive ubiquitination event on IRS-2. Separately, FSH was shown to induce IRS-2 via SP1 in granulosa cells linking IRS-2 to ovarian physiology.","evidence":"Co-IP, ubiquitination assays, Epsin1 binding, zebrafish validation; IRS-2 promoter ChIP for SP1, siRNA knockdown in granulosa cells","pmids":["25879670","26388164"],"confidence":"High","gaps":["Specific lysine(s) on IRS-2 monoubiquitinated by Nedd4 not mapped","Whether Nedd4-mediated membrane recruitment occurs in β-cells or neurons not tested"]},{"year":2018,"claim":"YAP/TAZ-driven IRS2 transcription was shown to amplify Akt signaling and drive hepatocellular carcinoma, while hyperinsulinemia-mediated IRS-2 downregulation in macrophages impaired M2a polarization through FoxO1/HDAC3/NCoR1 stabilization, extending IRS-2 biology to Hippo pathway oncogenesis and innate immune regulation.","evidence":"Pten/Sav1 double KO mice with AAV-Cas9 IRS2 knockout; myeloid-specific Irs2 and IR KO mice; macrophage activation assays","pmids":["29400692","30451856"],"confidence":"High","gaps":["Direct YAP/TAZ binding to IRS2 promoter not shown by ChIP","Whether M2a polarization defect contributes to human metabolic disease not established"]},{"year":2019,"claim":"PGC1A was identified as a fasting-induced transcriptional driver of IRS2 (while suppressing IRS1), establishing the IRS1:IRS2 ratio as a regulated variable that primes the liver for insulin-mediated gluconeogenic suppression upon refeeding.","evidence":"Gain- and loss-of-function in primary hepatocytes; ex vivo glucose production; in vivo PGC1A overexpression","pmids":["30770439"],"confidence":"High","gaps":["Whether PGC1A regulation of IRS2 extends to muscle or brain not tested","Co-activator complex used by PGC1A at the IRS2 locus not identified"]},{"year":2022,"claim":"IRS2-PI3K signaling was shown to stabilize MYC in breast cancer stem cells by inhibiting GSK3β-mediated Thr58 phosphorylation and proteasomal degradation, as proven by T58A-Myc rescue in Irs2-null cells, establishing a direct IRS2–GSK3β–MYC oncogenic axis.","evidence":"IRS2 KO in breast cancer cells; GSK3β activity; MYC Thr58 phosphorylation; T58A-Myc mutant rescue; stem cell functional assays","pmids":["36476848"],"confidence":"High","gaps":["Whether this axis operates in non-breast cancers not tested","Contribution of IRS-1 to MYC stabilization not evaluated"]},{"year":null,"claim":"Key unresolved questions include the full-length structure of IRS-2, the complete catalog of regulatory serine/threonine phosphorylation sites and their kinases, the tissue-specific mechanisms controlling the IRS-1:IRS-2 ratio, and the structural basis for differential SH2-domain recruitment relative to IRS-1.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution structure of IRS-2","Complete serine phosphorylation code not mapped","Tissue-specific transcriptional regulation not comprehensively defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,1,5,20,35]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[4,16,45]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[5]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[38]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,2,15,30,35,38]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[8,16,19,43]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[10,23,35,41,45]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[14,42]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[7,9,27]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[24,31]}],"complexes":[],"partners":["PIK3R1","GRB2","NEDD4","SOCS1","SOCS3","CTNNB1","ALK","GRK2"],"other_free_text":[]},"mechanistic_narrative":"IRS2 is a cytoplasmic adaptor protein that transduces signals from insulin, IGF-1, cytokine, and receptor tyrosine kinase receptors to the PI3K–Akt axis, thereby governing glucose homeostasis, cell survival, proliferation, and differentiation across multiple tissues. Upon receptor activation, IRS2 is tyrosine-phosphorylated and recruits the p85 subunit of PI3K, activating Akt and downstream effectors including FoxO1, GSK3β, and mTOR; its activity is positively regulated by CREB-, TFE3-, HIF-2α-, PGC1A-, YAP/TAZ-, and SP1-driven transcription, cAMP/GLP-1 signaling, and Nedd4-mediated monoubiquitination that promotes membrane recruitment, while it is negatively regulated by serine phosphorylation (mTOR at Ser675, ERK1/2 at Ser907) triggering degradation and by SOCS1/3–elongin BC-mediated ubiquitin-proteasomal destruction [PMID:7675087, PMID:7559579, PMID:9368067, PMID:12228220, PMID:21098738, PMID:25879670, PMID:12842910, PMID:16327801, PMID:24037094, PMID:29400692]. IRS2 is the dominant adaptor for pancreatic β-cell survival and Pdx1 maintenance, hepatic suppression of gluconeogenesis via the Akt–FoxO1 pathway, VTA dopamine neuron morphology, hippocampal LTP, myelination timing, macrophage M2a polarization, and female fertility [PMID:10471495, PMID:11994408, PMID:15711641, PMID:16374520, PMID:17143271, PMID:21955917, PMID:18717815, PMID:30451856, PMID:11014193]. In cancer contexts, IRS2 stabilizes MYC by inhibiting GSK3β-mediated Thr58 phosphorylation in breast cancer stem cells, mediates ALK-driven Akt–FoxO3 survival signaling in neuroblastoma, and functions as a YAP/TAZ effector promoting hepatocellular carcinoma [PMID:36476848, PMID:30459283, PMID:29400692]."},"prefetch_data":{"uniprot":{"accession":"Q9Y4H2","full_name":"Insulin receptor substrate 2","aliases":[],"length_aa":1338,"mass_kda":137.3,"function":"Signaling adapter protein that participates in the signal transduction from two prominent receptor tyrosine kinases, insulin receptor/INSR and insulin-like growth factor I receptor/IGF1R (PubMed:25879670). Plays therefore an important role in development, growth, glucose homeostasis as well as lipid metabolism (PubMed:24616100). Upon phosphorylation by the insulin receptor, functions as a signaling scaffold that propagates insulin action through binding to SH2 domain-containing proteins including the p85 regulatory subunit of PI3K, NCK1, NCK2, GRB2 or SHP2 (PubMed:15316008, PubMed:19109239). Recruitment of GRB2 leads to the activation of the guanine nucleotide exchange factor SOS1 which in turn triggers the Ras/Raf/MEK/MAPK signaling cascade (By similarity). Activation of the PI3K/AKT pathway is responsible for most of insulin metabolic effects in the cell, and the Ras/Raf/MEK/MAPK is involved in the regulation of gene expression and in cooperation with the PI3K pathway regulates cell growth and differentiation. Acts a positive regulator of the Wnt/beta-catenin signaling pathway through suppression of DVL2 autophagy-mediated degradation leading to cell proliferation (PubMed:24616100). Plays a role in cell cycle progression by promoting a robust spindle assembly checkpoint (SAC) during M-phase (PubMed:32554797). In macrophages, IL4-induced tyrosine phosphorylation of IRS2 leads to the recruitment and activation of phosphoinositide 3-kinase (PI3K) (PubMed:19109239)","subcellular_location":"Cytoplasm, cytosol","url":"https://www.uniprot.org/uniprotkb/Q9Y4H2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/IRS2","classification":"Not Classified","n_dependent_lines":376,"n_total_lines":1208,"dependency_fraction":0.31125827814569534},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/IRS2","total_profiled":1310},"omim":[{"mim_id":"615239","title":"MICRO RNA 7-1; MIR7-1","url":"https://www.omim.org/entry/615239"},{"mim_id":"612870","title":"PLECKSTRIN HOMOLOGY DOMAIN-INTERACTING PROTEIN; PHIP","url":"https://www.omim.org/entry/612870"},{"mim_id":"612465","title":"TBC1 DOMAIN FAMILY, MEMBER 4; TBC1D4","url":"https://www.omim.org/entry/612465"},{"mim_id":"611546","title":"ELONGATION OF VERY LONG CHAIN FATTY ACIDS-LIKE 6; ELOVL6","url":"https://www.omim.org/entry/611546"},{"mim_id":"609576","title":"ACYL-CoA DEHYDROGENASE, LONG-CHAIN; ACADL","url":"https://www.omim.org/entry/609576"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"},{"location":"Aggresome","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"bone marrow","ntpm":48.4}],"url":"https://www.proteinatlas.org/search/IRS2"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q9Y4H2","domains":[{"cath_id":"2.30.29.30","chopping":"30-55_70-149","consensus_level":"medium","plddt":89.699,"start":30,"end":149},{"cath_id":"2.30.29.30","chopping":"194-300","consensus_level":"medium","plddt":93.4726,"start":194,"end":300}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y4H2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y4H2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y4H2-F1-predicted_aligned_error_v6.png","plddt_mean":47.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=IRS2","jax_strain_url":"https://www.jax.org/strain/search?query=IRS2"},"sequence":{"accession":"Q9Y4H2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9Y4H2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9Y4H2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y4H2"}},"corpus_meta":[{"pmid":"22869320","id":"PMC_22869320","title":"Regulation of insulin sensitivity by serine/threonine phosphorylation of insulin receptor substrate proteins IRS1 and IRS2.","date":"2012","source":"Diabetologia","url":"https://pubmed.ncbi.nlm.nih.gov/22869320","citation_count":776,"is_preprint":false},{"pmid":"7675087","id":"PMC_7675087","title":"Role of IRS-2 in insulin and cytokine signalling.","date":"1995","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/7675087","citation_count":740,"is_preprint":false},{"pmid":"12228220","id":"PMC_12228220","title":"SOCS-1 and SOCS-3 block insulin signaling by ubiquitin-mediated degradation of IRS1 and IRS2.","date":"2002","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12228220","citation_count":700,"is_preprint":false},{"pmid":"10949029","id":"PMC_10949029","title":"Decreased IRS-2 and increased SREBP-1c lead to mixed insulin resistance and sensitivity in livers of lipodystrophic and ob/ob mice.","date":"2000","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/10949029","citation_count":626,"is_preprint":false},{"pmid":"12842910","id":"PMC_12842910","title":"cAMP promotes pancreatic beta-cell survival via CREB-mediated induction of IRS2.","date":"2003","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/12842910","citation_count":473,"is_preprint":false},{"pmid":"10471495","id":"PMC_10471495","title":"Irs-2 coordinates Igf-1 receptor-mediated beta-cell development and peripheral insulin signalling.","date":"1999","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/10471495","citation_count":452,"is_preprint":false},{"pmid":"17641201","id":"PMC_17641201","title":"Brain IRS2 signaling coordinates life span and nutrient homeostasis.","date":"2007","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/17641201","citation_count":436,"is_preprint":false},{"pmid":"9368067","id":"PMC_9368067","title":"A molecular basis for insulin resistance. 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Differential compartmentalization and trafficking of insulin receptor substrate (IRS)-1 and IRS-2.","date":"1998","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9565570","citation_count":151,"is_preprint":false},{"pmid":"29400692","id":"PMC_29400692","title":"Hippo-mediated suppression of IRS2/AKT signaling prevents hepatic steatosis and liver cancer.","date":"2018","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/29400692","citation_count":148,"is_preprint":false},{"pmid":"24159000","id":"PMC_24159000","title":"Myocardial loss of IRS1 and IRS2 causes heart failure and is controlled by p38α MAPK during insulin resistance.","date":"2013","source":"Diabetes","url":"https://pubmed.ncbi.nlm.nih.gov/24159000","citation_count":142,"is_preprint":false},{"pmid":"17374994","id":"PMC_17374994","title":"Oncogenic transformation by the signaling adaptor proteins insulin receptor substrate (IRS)-1 and 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protein that acts as an interface between signaling proteins with SH2 domains and the receptors for insulin, IGF-1, and several interleukins (IL-4, IL-9, IL-13). It contains a conserved N-terminal pleckstrin-homology domain and phosphotyrosine-binding domain.\",\n      \"method\": \"Protein purification and cloning from myeloid progenitor cells; sequence alignment with IRS-1\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — original cloning and purification, foundational discovery replicated across labs\",\n      \"pmids\": [\"7675087\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"IRS-2 (4PS) is the primary alternative substrate of the insulin receptor in IRS-1-deficient mice. Following insulin stimulation, IRS-2 is phosphorylated, binds the p85 subunit of PI 3-kinase activating it, and associates with Grb2 in liver and muscle.\",\n      \"method\": \"Immunoprecipitation, immunoblotting, and PI 3-kinase assays using specific antibodies in IRS-1-deficient mice; immunodepletion experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal immunoprecipitation, PI3K activity assays, immunodepletion in vivo\",\n      \"pmids\": [\"7559579\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Serine/threonine phosphorylation of IRS-2 (induced by TNFα, sphingomyelinase, or chronic insulin) impairs its interaction with the juxtamembrane domain of the insulin receptor (amino acids 943-984), thereby inhibiting insulin-induced tyrosine phosphorylation of IRS-2 and propagation of the insulin signal.\",\n      \"method\": \"In vitro binding assays using His6-fusion peptides of IR domains; treatment of Fao cells with TNFα and alkaline phosphatase reversal experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro binding reconstitution with mutagenic and enzymatic (phosphatase) validation\",\n      \"pmids\": [\"9368067\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"IRS-1 and IRS-2 undergo differential tyrosine phosphorylation and downstream signaling during insulin or IL-4 stimulation. IRS-2 predominates in hematopoietic cells; IRS-1 predominates in adipocytes. Distinct phosphorylation patterns during receptor interaction determine signaling specificity.\",\n      \"method\": \"Interaction with recombinant SH2 domain fusion proteins; differential expression analysis in cell lines\",\n      \"journal\": \"Molecular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple cell types examined, SH2-domain pull-downs, single lab\",\n      \"pmids\": [\"9013772\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"IRS-1 and IRS-2 are not functionally interchangeable for IGF-1-stimulated mitogenesis despite both activating PI 3-kinase. IRS-1 (but not IRS-2) is required for cell cycle progression (S-phase entry), while IRS-2 overexpression can restore PI 3-kinase activation and immediate-early gene expression to the same degree as IRS-1.\",\n      \"method\": \"Retroviral gene transduction into IRS-1-deficient cells; mitogenesis, PI 3-kinase, and immediate-early gene assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reconstitution by retroviral expression with multiple orthogonal functional readouts\",\n      \"pmids\": [\"9032279\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"IRS-2 is differentially compartmentalized relative to IRS-1 in adipocytes: IRS-2 is concentrated 2-fold more in cytosol than in intracellular membranes (IM), whereas IRS-1 is enriched in IM. Insulin-stimulated tyrosine phosphorylation of IRS-2 occurs mainly in IM despite its cytosolic localization. After insulin stimulation, both IRS-1 and IRS-2 translocate from IM to cytosol. IRS-2-mediated PI 3-kinase signaling is more transient than IRS-1-mediated signaling.\",\n      \"method\": \"Subcellular fractionation, immunoblotting, in vitro reconstitution assay in 3T3-L1 adipocytes\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — subcellular fractionation combined with in vitro reconstitution assay; multiple time-point kinetics\",\n      \"pmids\": [\"9565570\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"In fetal brown adipocytes, both IRS-1 and IRS-2 associate with p85α and activate PI 3-kinase in response to insulin/IGF-1, but only IRS-1 (not IRS-2) associates with Grb2 and links to the Ras-MAPK pathway, as shown by pull-down with GST-Grb2-SH2 and competition with a phosphopeptide containing pTyr895.\",\n      \"method\": \"GST-SH2 domain pull-down experiments, immunoprecipitation, phosphopeptide competition assays in fetal brown adipocytes\",\n      \"journal\": \"Molecular endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — GST pull-down with SH2 domains plus phosphopeptide competition defining the molecular basis for differential signaling\",\n      \"pmids\": [\"9605931\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Irs-2 coordinates Igf-1 receptor-mediated beta-cell development and peripheral insulin signaling in vivo. Irs-2 has the major role in beta-cell development and compensation for peripheral insulin resistance; intercross with Igf1r heterozygotes revealed that Igf-1 receptors promote beta-cell development through the Irs-2 signaling pathway.\",\n      \"method\": \"Genetic intercross of Irs1+/- and Irs2+/- mice; intercross with Igf1r+/- mice; metabolic phenotyping\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in multiple mouse models with defined phenotypic readouts\",\n      \"pmids\": [\"10471495\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Chronic hyperinsulinemia downregulates IRS-2 mRNA in liver, producing insulin resistance in gluconeogenesis. Despite IRS-2 deficiency, insulin continues to stimulate SREBP-1c production, establishing a 'mixed' insulin resistance/sensitivity that aggravates hyperinsulinemia.\",\n      \"method\": \"Analysis of lipodystrophic and ob/ob mouse livers; mRNA expression and signaling pathway analysis\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — two independent mouse models, replicated mechanistic finding\",\n      \"pmids\": [\"10949029\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Deletion of IRS-2 causes female infertility due to small, anovulatory ovaries and reduced pituitary gonadotrophs, demonstrating IRS-2 integrates reproductive and energy homeostasis signals.\",\n      \"method\": \"Irs2 knockout mouse phenotypic analysis including hormonal measurements, pituitary size, and ovarian histology\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with specific reproductive phenotypic readouts including tissue morphology and hormone levels\",\n      \"pmids\": [\"11014193\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"IRS-2 mediates IGF-I-stimulated breast cancer cell migration in metastatic variants; antisense reduction of IRS-2 diminishes IGF-mediated motility and anchorage-independent growth, defining IRS-2 as a positive regulator of breast cancer cell motility.\",\n      \"method\": \"Antisense IRS-2 transfection, IGF-I stimulation, migration and anchorage-independent growth assays\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function with specific cellular phenotype, single lab\",\n      \"pmids\": [\"11704861\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"IRS-1 and IRS-2 together are essential for adipocyte differentiation. Double-knockout of IRS-1 and IRS-2 completely abolishes adipocyte differentiation, PI 3-kinase activity during differentiation, and expression of C/EBPα and PPARγ.\",\n      \"method\": \"Mouse embryonic fibroblasts with four genotypes (WT, IRS-1-/-, IRS-2-/-, double KO); adipocyte differentiation assays, PI 3-kinase activity, gene expression\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean double KO with multiple orthogonal readouts, validated in vivo in newborn mice\",\n      \"pmids\": [\"11259600\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"SOCS1 and SOCS3 bind IRS-1 and IRS-2 and promote their ubiquitin-mediated degradation via the elongin BC ubiquitin-ligase complex. Mutations in the SOCS box of SOCS1 abrogate interaction with elongin BC without affecting IRS binding, and eliminate ubiquitination/degradation of IRS proteins.\",\n      \"method\": \"Co-immunoprecipitation of endogenous and recombinant proteins; ubiquitination assays; SOCS box mutants; adenoviral expression in mouse liver\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, domain mutagenesis, in vivo adenoviral validation, multiple cell types\",\n      \"pmids\": [\"12228220\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Pdx1 expression is reduced in islets from Irs2-/- mice before diabetes onset. Transgenic overexpression of Pdx1 restores beta-cell mass and function in Irs2-/- mice, preventing diabetes, demonstrating IRS-2 signaling is required for maintaining Pdx1 expression in beta-cells.\",\n      \"method\": \"Irs2-/- mouse islet analysis; Pdx1 transgenic rescue; genetic epistasis with Pdx1 haploinsufficiency\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — bidirectional genetic epistasis, loss and gain of function\",\n      \"pmids\": [\"11994408\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"IRS-2 and Stat6 cooperate in IL-4-induced T cell proliferation and Th2 differentiation. IRS-2 deficiency compromises IL-4-induced proliferation (through co-regulation of p27kip1) and Th2 cytokine secretion, but both Stat6 and IRS-2 are dispensable for IL-4-induced survival.\",\n      \"method\": \"T cells from Stat6-/-, Irs2-/-, and double-deficient mice; proliferation, cytokine secretion, and apoptosis assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in primary lymphocytes, multiple functional readouts\",\n      \"pmids\": [\"11739727\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"cAMP promotes pancreatic beta-cell survival via CREB-mediated transcriptional induction of IRS2. CREB directly targets the IRS2 promoter in vivo; IRS2 induction by cAMP enhances Akt activation in response to insulin/IGF-1.\",\n      \"method\": \"A-CREB dominant-negative transgenic mice; chromatin immunoprecipitation; cAMP/IRS2/Akt signaling assays in islets\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — transgenic loss-of-function, ChIP showing direct promoter binding, downstream signaling validation\",\n      \"pmids\": [\"12842910\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Hepatic IRS-1 is linked preferentially to glucose homeostasis (gluconeogenesis suppression) while IRS-2 is linked to lipid metabolism (SREBP-1c/fatty acid synthase regulation) in liver. Combined knockdown causes defective Akt activation and Foxo1 phosphorylation with systemic insulin resistance.\",\n      \"method\": \"Adenovirus-mediated shRNA knockdown of IRS-1, IRS-2, or both in mouse liver; gene expression, metabolic, and signaling analyses\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo isoform-specific knockdown with complementary functional readouts\",\n      \"pmids\": [\"15711641\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"TFE3 (a bHLH transcription factor) directly transactivates IRS-2 expression via E-box elements in the IRS-2 promoter, leading to enhanced Akt signaling and reduced plasma glucose.\",\n      \"method\": \"Expression cloning; adenoviral TFE3 expression in hepatocytes and in vivo; IRS-2 promoter analysis\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — expression cloning plus in vivo validation plus promoter analysis, multiple diabetes models\",\n      \"pmids\": [\"16327801\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Exendin-4 (GLP-1 receptor agonist) increases cAMP in beta cells, which promotes IRS-2 expression and Akt phosphorylation. Long-term beta-cell mass expansion by Ex4 requires IRS-2 signaling, as Ex4 fails to arrest beta-cell loss in Irs2-/- mice.\",\n      \"method\": \"cAMP measurement, IRS-2 expression, Akt phosphorylation in human islets and Min6 cells; Ex4 treatment of Irs2-/- mice\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — mechanism defined in vitro validated in Irs2 KO mice in vivo\",\n      \"pmids\": [\"16272563\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Deletion of both hepatic Irs1 and Irs2 abolishes Akt-FoxO1 pathway signaling in liver, causing hyperglycemia and upregulation of gluconeogenic genes (Pck1, G6pc, Ppargc1). Irs2 alone or Irs1 alone in liver is sufficient to maintain near-normal glucose homeostasis.\",\n      \"method\": \"Liver-specific Irs2 knockout (LKO) on Irs1-/- background; signaling pathway analysis, gene expression profiling\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — conditional double KO with comprehensive signaling and gene expression analysis\",\n      \"pmids\": [\"16374520\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"IRS-2 is a substrate of the TrkA receptor and the TRK-T1 oncogene. IRS-2 tyrosine phosphorylation by TrkA/TRK-T1 leads to recruitment of p85-PI3K, SHP-2, and Grb2 and increased PI 3-kinase activity. Direct interaction between TRK and IRS-2 was demonstrated by yeast two-hybrid.\",\n      \"method\": \"Co-immunoprecipitation, PI 3-kinase activity assays, yeast two-hybrid\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — yeast two-hybrid for direct interaction plus Co-IP and functional assays\",\n      \"pmids\": [\"11147812\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"FoxO1 and IRS-2 form a reciprocal stability circuit: Irs2 signaling promotes FoxO1 nuclear exclusion and degradation; loss of Irs2 increases FoxO1 stability. Conversely, FoxO1 transcription drives IRS-2 expression. Rapamycin inhibits Irs2 degradation and causes persistent FoxO1 degradation.\",\n      \"method\": \"Mouse embryo fibroblasts from Irs1-/- and Irs2-/- mice; protein stability assays; rapamycin treatment; PI 3-kinase and Akt activation measurements\",\n      \"journal\": \"Molecular endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple genetic backgrounds, pharmacological validation, bidirectional regulation demonstrated\",\n      \"pmids\": [\"16916938\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"IRS-2 expression in pancreatic beta-cells is specifically regulated by glucose at the transcriptional level in a dose-dependent, Ca2+-dependent manner. Glucose-induced IRS-2 upregulation correlates with increased IRS-2 tyrosine phosphorylation and Akt activation, promoting beta-cell survival.\",\n      \"method\": \"IRS-2 mRNA/protein expression kinetics in isolated rat islets; glucose dose-response; intracellular Ca2+ inhibition experiments; Akt phosphorylation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — primary beta cells, pharmacological dissection of Ca2+ requirement, multiple readouts\",\n      \"pmids\": [\"16574657\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"IRS-2 overexpression in mammary gland causes progressive hyperplasia and tumorigenesis. IRSs bind β-catenin in vitro and in vivo, and IRS-2 overexpression causes constitutive phosphorylation and mammary tumors with squamous differentiation consistent with β-catenin pathway activation.\",\n      \"method\": \"Transgenic mice with mammary-specific IRS-1 or IRS-2 overexpression; Co-IP of β-catenin with IRS proteins in vitro and in vivo\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — transgenic in vivo tumorigenesis plus Co-IP demonstrating β-catenin interaction\",\n      \"pmids\": [\"17030631\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The IRS2-Akt signaling pathway in VTA dopamine neurons is downregulated by chronic morphine, mediating the decrease in dopamine cell size and diminishing morphine reward (conditioned place preference). Viral-mediated manipulation of IRS2-Akt in VTA established causal roles.\",\n      \"method\": \"Viral-mediated gene transfer to rat VTA; conditioned place preference; dopamine cell morphometry; chronic morphine pellet administration\",\n      \"journal\": \"Nature neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — viral gain/loss of function in specific brain region with defined behavioral and cellular readouts\",\n      \"pmids\": [\"17143271\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Brain-specific Irs2 knockout in mice extends lifespan up to 18%, reduces meal-induced hypothalamic oxidative stress (stable SOD2), and maintains greater glucose oxidation, identifying brain IRS2 as a regulator of longevity and nutrient homeostasis.\",\n      \"method\": \"Brain-specific Irs2 conditional knockout mice; lifespan measurement; metabolic cage studies; hypothalamic SOD2 measurement\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — tissue-specific KO with quantitative lifespan and metabolic phenotype\",\n      \"pmids\": [\"17641201\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Phosphotyrosine interactome mapping of IRS-2 identified phosphorylation-specific interaction partners for multiple tyrosine sites, including shared partners with IRS-1 and several differential interactors. IRS-2 shows different combinatorial phosphorylation effects and differential binding of SHP2 compared to IRS-1.\",\n      \"method\": \"SILAC-based quantitative interaction proteomics with phosphorylated vs. non-phosphorylated bait peptides\",\n      \"journal\": \"Molecular & cellular proteomics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — comprehensive MS-based phosphotyrosine interactome with quantitative SILAC\",\n      \"pmids\": [\"19001411\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"IRS-2 deficiency impairs appropriate timing of myelination in vivo; IRS-2-/- mice show reduced myelin protein expression at postnatal day 10. Compensatory IRS-1 upregulation and increased IGF-1R signaling occur in IRS-2-/- brains, demonstrating IGF-1R/IRS-2 signals are critical for myelination timing.\",\n      \"method\": \"IRS-2-/- mice; myelin protein expression by Western blot/immunostaining; cerebral myelin isolation; compensatory IRS-1 analysis\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with specific developmental phenotype and compensation mechanism identified\",\n      \"pmids\": [\"18717815\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Deletion of Irs2 in APP transgenic mice reduces amyloid-β deposition, increases transthyretin (an Aβ-binding clearance protein), and rescues behavioral deficits, while increasing tau phosphorylation (reduced tau-phosphatase PP2A despite inhibited GSK-3). This reveals divergent effects of IRS2 on amyloid vs. tau pathology.\",\n      \"method\": \"Genetic cross of Tg2576 APP mice with Irs2-/- mice; amyloid plaque quantification; tau phosphorylation; transthyretin and PP2A/GSK-3 analysis; behavioral testing\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with multiple biochemical and behavioral readouts\",\n      \"pmids\": [\"19523444\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"In IRS2-/- mice, hepatic PTP1B expression and its association with the insulin receptor are increased. Double knockout of IRS2 and PTP1B restores IRS1-mediated PI 3-kinase/Akt/Foxo1 signaling in liver, improving glucose tolerance. PTP1B determines insulin receptor phosphorylation state and interplay between IRS1 and IRS2.\",\n      \"method\": \"IRS2-/-/PTP1B-/- double-knockout mice; hepatic insulin signaling analysis; isolated hepatocyte experiments; resveratrol pharmacological inhibition\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic and pharmacological epistasis, mechanistic pathway delineation\",\n      \"pmids\": [\"20028942\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"IRS-2 is phosphorylated at Ser675 by mTOR and at Ser907 by ERK1/2 following insulin stimulation. Ser675 phosphorylation accelerates IRS-2 protein degradation (mTOR-mediated negative feedback); Ser907 phosphorylation does not impair Grb2 association but affects adjacent Tyr911 phosphorylation.\",\n      \"method\": \"Monoclonal phosphosite-specific antibodies; siRNA knockdown of ERK1/2 and mTOR; Ala mutant IRS-2 expression in HEK293 cells; protein half-life measurement\",\n      \"journal\": \"American journal of physiology. Endocrinology and metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — site-specific mutagenesis, siRNA knockdown of individual kinases, phosphosite-specific antibody validation\",\n      \"pmids\": [\"21098738\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"IRS-2 deficiency impairs NMDA receptor-dependent LTP in hippocampus. During LTP induction, IRS2 is tyrosine-phosphorylated. In Irs2-/- mice, tetanus stimulation fails to activate Fyn, AKT, and MAPK, and NMDA receptor activation is defective, despite normal NR2A, NR2B, and PSD95 expression.\",\n      \"method\": \"Hippocampal slice electrophysiology (LTP recordings); Western blot for Fyn/AKT/MAPK phosphorylation; IRS2 phosphorylation during LTP in control mice\",\n      \"journal\": \"Cerebral cortex\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with specific electrophysiological and biochemical readouts, IRS2 phosphorylation measured during LTP\",\n      \"pmids\": [\"21955917\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Increasing Irs2 levels in brains of R6/2 Huntington disease mice worsens neuronal oxidative stress and mitochondrial dysfunction; reducing Irs2 improves motor performance, extends lifespan, and increases nuclear FoxO1 and autophagy. Thus IRS2 signaling modulates HD progression through FoxO1-dependent autophagy.\",\n      \"method\": \"Genetic modulation of Irs2 in R6/2 mice; FoxO1 localization; autophagosome counting; oxidative stress and mitochondrial function assays\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — bidirectional genetic modulation with multiple mechanistic readouts\",\n      \"pmids\": [\"21926467\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Cardiac-specific deletion of IRS1 and IRS2 causes dilated cardiomyopathy with reduced Akt→FoxO1 signaling, cardiac apoptosis, and fibrosis. Hyperinsulinemia reduces IRS1/2 in cardiomyocytes via p38α MAPK activation, identifying p38α as a mediator of cardiac insulin resistance.\",\n      \"method\": \"Heart-specific IRS1/2 double-knockout mice; neonatal cardiomyocyte experiments with chronic insulin exposure; p38 inhibition\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — organ-specific KO with molecular mechanism via p38α identified in primary cells and in vivo\",\n      \"pmids\": [\"24159000\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"IRS2 is phosphorylated during caffeine-induced LTP (CAF LTP) in hippocampal CA1 in a Ca2+-dependent manner. Akt phosphorylation during CAF LTP is defective in Irs2-/- mice, demonstrating TrkB-IRS2-PI3K signaling is required for this form of synaptic plasticity.\",\n      \"method\": \"Hippocampal slice recordings; IRS2 phosphorylation measurement; Irs2-/- mice; Ca2+ chelation experiments\",\n      \"journal\": \"Addiction biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with electrophysiology and biochemical validation, single lab\",\n      \"pmids\": [\"27457910\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"IRS2 is a major substrate and signaling node downstream of oncogenic ALK in neuroblastoma. ALK TKI treatment reduces IRS2 recruitment to ALK and IRS2 tyrosine phosphorylation. IRS2 links ALK to the Akt-FoxO3 survival axis; siRNA depletion of IRS2 or ALK reduces Akt/FoxO3 phosphorylation and cell viability.\",\n      \"method\": \"Integrated proximal proteomics (ALK interactome, phosphotyrosine interactome, phosphoproteome); siRNA depletion; ALK TKI treatment\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — comprehensive MS-based interactome plus siRNA loss-of-function, multiple readouts\",\n      \"pmids\": [\"30459283\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"HIF-2α directly or indirectly induces IRS-2 expression in liver, sensitizing hepatic insulin signaling. Liver IRS-2 is both necessary and sufficient to mediate HIF-2α and VEGF inhibitor effects on glucose tolerance and hepatic insulin signaling including gluconeogenic gene suppression.\",\n      \"method\": \"Liver-specific constitutive HIF-2α activation; IRS-2 knockout rescue experiments; VEGF inhibitor treatment in diabetic mice\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — constitutive activation and genetic epistasis demonstrating IRS2 is necessary and sufficient\",\n      \"pmids\": [\"24037094\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Insulin stimulates GRK2 recruitment to β2AR via IRS2, inducing β2AR phosphorylation at GRK sites (Ser355/356) and receptor internalization. IRS2 deletion disrupts the IR-GRK2 complex, attenuates β2AR phosphorylation and internalization, and abrogates insulin's counter-regulation of βAR signaling in cardiomyocytes.\",\n      \"method\": \"Co-immunoprecipitation of IR-GRK2 complex; IRS2 KO cardiomyocytes; β2AR phosphorylation and internalization assays; cAMP-PKA activity measurements\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP with functional KO validation, multiple readouts\",\n      \"pmids\": [\"25460042\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Nedd4 is an E3 ubiquitin ligase for IRS-2 that monoubiquitinates IRS-2, promoting its association with Epsin1 and recruitment to the plasma membrane. Membrane recruitment enhances IGF-1 receptor-induced IRS-2 tyrosine phosphorylation and downstream signaling and mitogenesis.\",\n      \"method\": \"Co-IP; ubiquitination assays; Nedd4 overexpression; Epsin1 binding assays; zebrafish embryo growth experiments; prostate cancer cell proliferation\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — E3 ligase identification with Co-IP, ubiquitination assays, in vivo zebrafish validation\",\n      \"pmids\": [\"25879670\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"FSH specifically induces IRS-2 expression in granulosa cells via the cAMP pathway and SP1 transcription factor binding to IRS-2 promoter SP1 sites. FSH stimulates SP1 nuclear translocation and IRS-2 promoter binding. IRS-2 mediates FSH-stimulated PI3K activity, Akt phosphorylation, GLUT4 translocation and glucose uptake in granulosa cells.\",\n      \"method\": \"IRS-2 promoter analysis; siRNA knockdown; chromatin immunoprecipitation; SP1 nuclear translocation imaging; GLUT4 translocation assay\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — promoter analysis with ChIP, siRNA knockdown, multiple downstream functional readouts\",\n      \"pmids\": [\"26388164\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"JAK2V617F (oncogenic JAK2) directly binds IRS2 in MPN cells; IRS2 silencing decreases STAT5 phosphorylation, reduces viability and increases apoptosis in JAK2V617F cells but not JAK2WT cells, demonstrating IRS2 as a binding partner and survival node specific to mutant JAK2 signaling.\",\n      \"method\": \"Co-immunoprecipitation of JAK2/IRS2; siRNA silencing; viability and apoptosis assays in MPN cell lines and primary patient samples\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP plus siRNA functional validation in cell lines and primary samples\",\n      \"pmids\": [\"26755644\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"YAP/TAZ transcriptional activity in liver upregulates IRS2 expression, amplifying AKT signaling. Knockout of IRS2 by AAV-Cas9 represses liver tumorigenesis in Pten-/-/Sav1-/- mice, placing IRS2 downstream of Hippo/YAP-TAZ signaling as a driver of hepatocellular carcinoma.\",\n      \"method\": \"Genetic mouse models (Pten/Sav1 double KO); AAV-Cas9 IRS2 knockout; IRS2 expression correlation with YAP/TAZ in human HCC\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo genetic epistasis with AAV-Cas9 and multiple mouse models\",\n      \"pmids\": [\"29400692\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Hyperinsulinemia downregulates macrophage IRS2 expression via the insulin receptor, impairing the IL-4/IRS2/Akt pathway and M2a-subtype macrophage activation. This impairment stabilizes the FoxO1/HDAC3/NCoR1 corepressor complex and leads to systemic insulin resistance under high-fat diet.\",\n      \"method\": \"Myeloid cell-specific Irs2 and IR knockout mice; macrophage activation assays; FoxO1/HDAC3/NCoR1 complex analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific KO, molecular complex identified, in vivo metabolic validation\",\n      \"pmids\": [\"30451856\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PGC1A drives IRS2 expression downstream of glucagon/cAMP/CREB signaling in hepatocytes while simultaneously reducing IRS1 expression, controlling the IRS1:IRS2 ratio during fasting. PGC1A-induced IRS2 is essential for insulin-mediated suppression of gluconeogenesis.\",\n      \"method\": \"Gain- and loss-of-function models in primary hepatocytes; protein and gene expression; ex vivo glucose production; in vivo PGC1A overexpression\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — bidirectional gain/loss of function, CREB dependence shown, multiple functional readouts\",\n      \"pmids\": [\"30770439\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"IRS-2 is recruited into mutant huntingtin (mHTT) aggregates in pancreatic beta-cells, reducing PI3K/AKT/FoxO1 pathway activation and impairing glucose-stimulated insulin secretion and cell proliferation. Insulin treatment inhibits mHTT aggregation and restores PI3K/AKT/FoxO1 signaling.\",\n      \"method\": \"NIT-1 cells expressing N-terminal mHTT (160Q); co-localization of IRS-2 with mHTT aggregates; PI3K/AKT/FoxO1 signaling assays; insulin rescue experiments\",\n      \"journal\": \"Journal of molecular neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single lab, cell line model, co-localization without direct Co-IP validation\",\n      \"pmids\": [\"34331233\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"IRS2-PI3K signaling stabilizes MYC in breast cancer stem cells by inhibiting GSK3β, suppressing MYC phosphorylation at Thr58, and reducing proteasomal degradation of MYC. A T58A-Myc mutant rescues CSC function in Irs2-/- cells.\",\n      \"method\": \"IRS2 knockout in breast cancer cells; GSK3β activity assays; MYC phosphorylation at Thr58; T58A-Myc mutant rescue; stem cell functional assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — mutagenesis rescue (T58A-Myc), biochemical pathway dissection, GSK3β link established\",\n      \"pmids\": [\"36476848\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"IRS2 is a cytoplasmic scaffold/adaptor protein phosphorylated on tyrosine by the insulin receptor (and IGF-1R, cytokine receptors, ALK, TrkA) at the juxtamembrane domain, whereupon it recruits and activates PI3K (p85/p110α), leading to Akt activation and downstream regulation of FoxO1, mTOR, GSK3β, and MYC; its activity is positively modulated by Nedd4-mediated monoubiquitination (membrane recruitment), CREB/TFE3/FoxO3a/HIF-2α/PGC1A-driven transcription, and cAMP/GLP-1 signaling, while it is negatively regulated by serine phosphorylation via ERK1/2 (Ser907), mTOR (Ser675), and other feedback kinases causing degradation, and by SOCS1/3-elongin BC-mediated ubiquitin-proteasomal degradation; tissue-specifically, IRS2 is the dominant adaptor for beta-cell survival and proliferation, hepatic gluconeogenesis suppression, VTA dopamine neuron morphology, hippocampal LTP, macrophage M2a polarization, female reproduction, and myelination timing.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"IRS2 is a cytoplasmic adaptor protein that transduces signals from insulin, IGF-1, cytokine, and receptor tyrosine kinase receptors to the PI3K–Akt axis, thereby governing glucose homeostasis, cell survival, proliferation, and differentiation across multiple tissues. Upon receptor activation, IRS2 is tyrosine-phosphorylated and recruits the p85 subunit of PI3K, activating Akt and downstream effectors including FoxO1, GSK3β, and mTOR; its activity is positively regulated by CREB-, TFE3-, HIF-2α-, PGC1A-, YAP/TAZ-, and SP1-driven transcription, cAMP/GLP-1 signaling, and Nedd4-mediated monoubiquitination that promotes membrane recruitment, while it is negatively regulated by serine phosphorylation (mTOR at Ser675, ERK1/2 at Ser907) triggering degradation and by SOCS1/3–elongin BC-mediated ubiquitin-proteasomal destruction [PMID:7675087, PMID:7559579, PMID:9368067, PMID:12228220, PMID:21098738, PMID:25879670, PMID:12842910, PMID:16327801, PMID:24037094, PMID:29400692]. IRS2 is the dominant adaptor for pancreatic β-cell survival and Pdx1 maintenance, hepatic suppression of gluconeogenesis via the Akt–FoxO1 pathway, VTA dopamine neuron morphology, hippocampal LTP, myelination timing, macrophage M2a polarization, and female fertility [PMID:10471495, PMID:11994408, PMID:15711641, PMID:16374520, PMID:17143271, PMID:21955917, PMID:18717815, PMID:30451856, PMID:11014193]. In cancer contexts, IRS2 stabilizes MYC by inhibiting GSK3β-mediated Thr58 phosphorylation in breast cancer stem cells, mediates ALK-driven Akt–FoxO3 survival signaling in neuroblastoma, and functions as a YAP/TAZ effector promoting hepatocellular carcinoma [PMID:36476848, PMID:30459283, PMID:29400692].\",\n  \"teleology\": [\n    {\n      \"year\": 1995,\n      \"claim\": \"Identification of IRS-2 as a second insulin receptor substrate with PH and PTB domains established that insulin/IGF-1/cytokine signaling operates through a family of adaptor proteins rather than solely through IRS-1.\",\n      \"evidence\": \"Protein purification and cloning from myeloid progenitor cells; reciprocal IP and PI3K assays in IRS-1-deficient mice\",\n      \"pmids\": [\"7675087\", \"7559579\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Three-dimensional structure of full-length IRS-2 undetermined\", \"Relative stoichiometry of IRS-1 vs IRS-2 at the insulin receptor not quantified\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Demonstration that serine/threonine phosphorylation of IRS-2 blocks its binding to the insulin receptor juxtamembrane domain revealed the molecular basis of TNFα- and chronic-insulin-induced insulin resistance at the IRS-2 level.\",\n      \"evidence\": \"In vitro binding assays with His6-tagged IR domains; TNFα treatment and alkaline phosphatase reversal in Fao cells\",\n      \"pmids\": [\"9368067\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific serine residues mediating TNFα-induced inhibition not mapped in this study\", \"Kinase(s) responsible for inhibitory serine phosphorylation not identified here\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Showing that IRS-1 and IRS-2 are not functionally interchangeable for IGF-1-driven mitogenesis — IRS-2 restores PI3K but not cell cycle progression — defined substrate-specific signaling outputs.\",\n      \"evidence\": \"Retroviral reconstitution in IRS-1-deficient cells; SH2-domain pull-downs across cell types\",\n      \"pmids\": [\"9032279\", \"9013772\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular determinant on IRS-1 that uniquely drives S-phase entry not identified\", \"Differential phosphosite usage between IRS-1 and IRS-2 not fully mapped\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Subcellular fractionation revealed that IRS-2 is predominantly cytosolic yet phosphorylated at intracellular membranes, with more transient PI3K signaling than IRS-1, establishing compartmentalization as a mechanism for signaling specificity.\",\n      \"evidence\": \"Subcellular fractionation and in vitro reconstitution in 3T3-L1 adipocytes; GST-SH2 pull-downs in brown adipocytes\",\n      \"pmids\": [\"9565570\", \"9605931\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism driving IRS-2 membrane translocation not determined\", \"Whether compartmentalization differs across cell types not systematically tested\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Genetic epistasis in Irs2-haploinsufficient and Igf1r-haploinsufficient mice proved IRS-2 is the dominant adaptor coordinating IGF-1R-mediated β-cell development and compensation for insulin resistance, distinguishing its role from IRS-1.\",\n      \"evidence\": \"Intercross of Irs1+/-, Irs2+/-, and Igf1r+/- mice with metabolic phenotyping\",\n      \"pmids\": [\"10471495\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"IRS-2-specific downstream transcriptional programs in β-cells not characterized\", \"Whether IRS-2 is required cell-autonomously in β-cells not yet resolved at this stage\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Discovery that IRS-2 knockout causes female infertility (anovulatory ovaries, reduced gonadotrophs) and that hepatic IRS-2 is transcriptionally downregulated by hyperinsulinemia broadened IRS-2 biology beyond metabolism to reproduction and established a 'mixed resistance' model in liver.\",\n      \"evidence\": \"Irs2 knockout reproductive phenotyping; mRNA analysis in lipodystrophic and ob/ob mouse livers\",\n      \"pmids\": [\"11014193\", \"10949029\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of IRS-2 transcriptional repression by chronic insulin not identified\", \"Cell-autonomous role in pituitary gonadotrophs vs. ovarian cells not dissected\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Identification of SOCS1/3–elongin BC as the E3 ligase complex mediating IRS-2 ubiquitin-proteasomal degradation, and demonstration that IRS-2 sustains Pdx1 expression in β-cells (rescued by Pdx1 transgene), defined both a key negative regulator and a critical transcriptional target of IRS-2 signaling.\",\n      \"evidence\": \"SOCS box mutagenesis and ubiquitination assays; Irs2-/-/Pdx1-transgenic genetic rescue; IL-4/T cell functional assays in Irs2-/- mice\",\n      \"pmids\": [\"12228220\", \"11994408\", \"11739727\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific lysine residues on IRS-2 targeted by SOCS-mediated ubiquitination not mapped\", \"Whether SOCS-mediated degradation is the dominant pathway in β-cells not tested\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"ChIP-validated CREB binding to the IRS2 promoter established a cAMP→CREB→IRS2→Akt feed-forward circuit that explained how incretin signaling promotes β-cell survival.\",\n      \"evidence\": \"A-CREB dominant-negative transgenic mice; chromatin immunoprecipitation of IRS2 promoter; cAMP-IRS2-Akt signaling in islets\",\n      \"pmids\": [\"12842910\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Other transcription factors co-operating with CREB at the IRS2 promoter not identified\", \"Epigenetic regulation of IRS2 promoter not addressed\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Isoform-specific hepatic knockdown and liver-specific double knockouts established that IRS-1 and IRS-2 have partially non-overlapping hepatic roles — IRS-2 linked to SREBP-1c/lipogenesis, IRS-1 to gluconeogenesis suppression — with combined loss abolishing Akt–FoxO1 signaling. TFE3 and GLP-1/exendin-4 were identified as positive transcriptional and hormonal regulators of IRS-2.\",\n      \"evidence\": \"Adenoviral shRNA knockdown in liver; liver-specific Irs2 KO on Irs1-/- background; TFE3 adenoviral expression; exendin-4 treatment in Irs2-/- mice and human islets\",\n      \"pmids\": [\"15711641\", \"16374520\", \"16327801\", \"16272563\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether TFE3 regulation of IRS-2 operates in extrahepatic tissues not tested\", \"Mechanistic basis for IRS-2-specific lipogenic gene regulation not fully delineated\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"IRS-2 was shown to regulate diverse biological contexts: β-catenin-driven mammary tumorigenesis upon overexpression, VTA dopamine neuron size and morphine reward via Akt, glucose-dependent transcriptional induction in β-cells, and a reciprocal stability circuit with FoxO1.\",\n      \"evidence\": \"Mammary-specific IRS-2 transgenic mice and β-catenin Co-IP; viral IRS2/Akt manipulation in rat VTA with behavioral assays; glucose dose-response in isolated islets; Irs2-/- MEFs with rapamycin and FoxO1 stability assays\",\n      \"pmids\": [\"17030631\", \"17143271\", \"16574657\", \"16916938\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for IRS-2/β-catenin interaction unknown\", \"Whether FoxO1–IRS-2 reciprocal circuit operates in all IRS-2-expressing tissues not tested\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Brain-specific Irs2 deletion extended lifespan by ~18% and reduced hypothalamic oxidative stress, establishing CNS IRS-2 signaling as a determinant of organismal aging.\",\n      \"evidence\": \"Brain-specific Irs2 conditional KO mice; lifespan measurement; metabolic cage studies; SOD2 analysis\",\n      \"pmids\": [\"17641201\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific neuronal populations mediating lifespan effect not identified\", \"Whether caloric restriction and IRS-2 reduction share a common mechanism not tested\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"SILAC-based phosphotyrosine interactome mapping of IRS-2 revealed site-specific interaction partners and combinatorial phosphorylation effects, while IRS-2 was shown to be required for proper myelination timing via IGF-1R signaling.\",\n      \"evidence\": \"SILAC quantitative MS with phosphopeptide baits; Irs2-/- mouse myelin protein analysis at P10\",\n      \"pmids\": [\"19001411\", \"18717815\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which tyrosine sites are critical for myelination signaling not identified\", \"Oligodendrocyte-autonomous requirement for IRS-2 not demonstrated\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Mapping mTOR-dependent Ser675 phosphorylation as a degradation signal and ERK1/2-dependent Ser907 phosphorylation as a modulator of adjacent Tyr911 defined the molecular logic of negative feedback serine phosphorylation on IRS-2.\",\n      \"evidence\": \"Phosphosite-specific monoclonal antibodies; Ala mutants; siRNA knockdown of ERK1/2 and mTOR; protein half-life in HEK293 cells\",\n      \"pmids\": [\"21098738\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full catalog of inhibitory serine phosphorylation sites on IRS-2 not complete\", \"In vivo significance of Ser675 and Ser907 not tested in animal models\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"IRS-2 was found to be tyrosine-phosphorylated during hippocampal LTP induction and required for NMDA receptor-dependent Fyn/Akt/MAPK activation, and separately, reducing brain IRS-2 in Huntington disease mice improved motor function via FoxO1-dependent autophagy, revealing bidirectional roles in neuronal plasticity and neurodegeneration.\",\n      \"evidence\": \"Hippocampal slice LTP recordings in Irs2-/- mice; genetic modulation of Irs2 in R6/2 HD mice with autophagosome quantification\",\n      \"pmids\": [\"21955917\", \"21926467\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Upstream kinase phosphorylating IRS-2 during LTP not identified\", \"Whether IRS-2 reduction benefits other polyglutamine diseases not tested\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"IRS-2 was placed downstream of ALK as a signaling node in neuroblastoma and downstream of HIF-2α in liver, expanding the receptor and transcriptional inputs that converge on IRS-2.\",\n      \"evidence\": \"Integrated proximal proteomics and siRNA in neuroblastoma cells; liver-specific HIF-2α activation with IRS-2 KO rescue\",\n      \"pmids\": [\"30459283\", \"24037094\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether ALK directly phosphorylates IRS-2 or acts via an intermediary kinase not resolved\", \"Mechanism by which HIF-2α induces IRS-2 (direct vs. indirect) not fully determined\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Nedd4 was identified as an E3 ligase that monoubiquitinates IRS-2, promoting Epsin1-dependent plasma membrane recruitment and enhanced IGF-1R signaling — the first positive ubiquitination event on IRS-2. Separately, FSH was shown to induce IRS-2 via SP1 in granulosa cells linking IRS-2 to ovarian physiology.\",\n      \"evidence\": \"Co-IP, ubiquitination assays, Epsin1 binding, zebrafish validation; IRS-2 promoter ChIP for SP1, siRNA knockdown in granulosa cells\",\n      \"pmids\": [\"25879670\", \"26388164\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific lysine(s) on IRS-2 monoubiquitinated by Nedd4 not mapped\", \"Whether Nedd4-mediated membrane recruitment occurs in β-cells or neurons not tested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"YAP/TAZ-driven IRS2 transcription was shown to amplify Akt signaling and drive hepatocellular carcinoma, while hyperinsulinemia-mediated IRS-2 downregulation in macrophages impaired M2a polarization through FoxO1/HDAC3/NCoR1 stabilization, extending IRS-2 biology to Hippo pathway oncogenesis and innate immune regulation.\",\n      \"evidence\": \"Pten/Sav1 double KO mice with AAV-Cas9 IRS2 knockout; myeloid-specific Irs2 and IR KO mice; macrophage activation assays\",\n      \"pmids\": [\"29400692\", \"30451856\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct YAP/TAZ binding to IRS2 promoter not shown by ChIP\", \"Whether M2a polarization defect contributes to human metabolic disease not established\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"PGC1A was identified as a fasting-induced transcriptional driver of IRS2 (while suppressing IRS1), establishing the IRS1:IRS2 ratio as a regulated variable that primes the liver for insulin-mediated gluconeogenic suppression upon refeeding.\",\n      \"evidence\": \"Gain- and loss-of-function in primary hepatocytes; ex vivo glucose production; in vivo PGC1A overexpression\",\n      \"pmids\": [\"30770439\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PGC1A regulation of IRS2 extends to muscle or brain not tested\", \"Co-activator complex used by PGC1A at the IRS2 locus not identified\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"IRS2-PI3K signaling was shown to stabilize MYC in breast cancer stem cells by inhibiting GSK3β-mediated Thr58 phosphorylation and proteasomal degradation, as proven by T58A-Myc rescue in Irs2-null cells, establishing a direct IRS2–GSK3β–MYC oncogenic axis.\",\n      \"evidence\": \"IRS2 KO in breast cancer cells; GSK3β activity; MYC Thr58 phosphorylation; T58A-Myc mutant rescue; stem cell functional assays\",\n      \"pmids\": [\"36476848\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether this axis operates in non-breast cancers not tested\", \"Contribution of IRS-1 to MYC stabilization not evaluated\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the full-length structure of IRS-2, the complete catalog of regulatory serine/threonine phosphorylation sites and their kinases, the tissue-specific mechanisms controlling the IRS-1:IRS-2 ratio, and the structural basis for differential SH2-domain recruitment relative to IRS-1.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No high-resolution structure of IRS-2\", \"Complete serine phosphorylation code not mapped\", \"Tissue-specific transcriptional regulation not comprehensively defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1, 5, 20, 35]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [4, 16, 45]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [38]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 2, 15, 30, 35, 38]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [8, 16, 19, 43]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [10, 23, 35, 41, 45]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [14, 42]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [7, 9, 27]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [24, 31]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"PIK3R1\",\n      \"GRB2\",\n      \"NEDD4\",\n      \"SOCS1\",\n      \"SOCS3\",\n      \"CTNNB1\",\n      \"ALK\",\n      \"GRK2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}