{"gene":"GAB3","run_date":"2026-04-28T17:46:04","timeline":{"discoveries":[{"year":2002,"finding":"Gab3 contains an amino-terminal pleckstrin homology (PH) domain, multiple tyrosine phosphorylation sites, SH2 domain binding sites, and two polyproline motifs. Upon M-CSF receptor (Fms) stimulation, Gab3 is tyrosine phosphorylated and associates transiently with p85 (PI3K regulatory subunit) and SHP2. Overexpression of Gab3 in FD-Fms cells dramatically accelerates macrophage differentiation upon M-CSF stimulation.","method":"Co-immunoprecipitation, overexpression in FDC-P1/FD-Fms cell lines, tyrosine phosphorylation assay, mRNA expression analysis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP showing p85/SHP2 association, functional overexpression with defined differentiation phenotype, replicated in multiple cell contexts","pmids":["11739737"],"is_preprint":false},{"year":2002,"finding":"Gab3 specifically interacts with the adapter protein Mona/Gads during monocyte/macrophage differentiation. This interaction is mediated by the C-terminal SH3 domain of Mona and the atypical proline-rich domain of Gab3. Gab3 does not interact with the related adapter Grb2 via Mona but does form a complex with Grb2. The M-CSF receptor mutation Y697F impairs Gab3 tyrosine phosphorylation and reduces Mona induction, while Y807F (differentiation-defective) also fails to induce Mona expression.","method":"GST pull-down, co-immunoprecipitation, site-directed mutagenesis of M-CSF receptor (Y697F, Y807F), immunoblotting","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1/2 — GST pull-down domain mapping combined with receptor mutagenesis and Co-IP in primary bone marrow cells","pmids":["11997510"],"is_preprint":false},{"year":2003,"finding":"Gab3-deficient mice generated by homologous recombination develop normally with no impairment in macrophage differentiation or numbers, no compensation by Gab1 or Gab2 upregulation, and no major immune deficiency in T- or B-lymphocyte responses, indicating Gab3 is dispensable for normal hematopoiesis in vivo.","method":"Homologous recombination knockout, monoclonal antibody generation, immunoblotting, detailed hematopoietic and immune phenotyping","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — rigorous genetic knockout with comprehensive phenotypic analysis across multiple cell lineages","pmids":["12640125"],"is_preprint":false},{"year":2019,"finding":"Gab3 is required for IL-2- and IL-15-induced NK cell expansion. Loss of Gab3 causes selective impairment of MAPK signaling but not STAT5 signaling downstream of these cytokines. Gab3-deficient mice show impaired NK cell-mediated elimination of missing-self and tumor targets, and impaired uterine NK cell expansion leading to defective spiral artery remodeling and increased trophoblast invasion.","method":"Gab3-deficient mouse model (in vivo and ex vivo), cytokine stimulation with signaling readouts (MAPK, STAT5), adoptive transfer, NK cell functional assays","journal":"Science immunology","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with defined signaling pathway dissection (MAPK vs. STAT5) and multiple functional readouts in vivo","pmids":["31375526"],"is_preprint":false},{"year":2019,"finding":"Gab2 and Gab3 redundantly suppress colitis by modulating macrophage and CD8+ T-cell activation. Double knockout (Gab2/3-/-) mice develop spontaneous colitis with reduced PI3-kinase/Akt/mTORC1 signaling in macrophages and T-cells, and increased pSTAT5 in IL-2-stimulated T-cells. Reciprocal bone marrow transplantation demonstrated a hematopoietic disease-initiating mechanism.","method":"Double knockout mouse generation, bone marrow transplantation, adoptive transfer, intracellular signaling analysis (PI3K/Akt/mTORC1, STAT5)","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 2 — genetic double KO with epistasis and signaling readouts, but redundancy complicates Gab3-specific conclusions","pmids":["30936879"],"is_preprint":false},{"year":2017,"finding":"In colorectal cancer cells, Gab3 co-precipitates with p85 and SHP2, and is required for downstream Akt and Erk activation. Gab3 knockdown inhibits both Akt and Erk activation, while overexpression augments them, promoting CRC cell proliferation in vitro and tumor growth in vivo.","method":"Co-immunoprecipitation, shRNA knockdown, overexpression, xenograft tumor model, Akt/Erk phosphorylation assays","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2/3 — Co-IP confirms p85/SHP2 complex, functional KD/OE with signaling readout, single lab","pmids":["28115166"],"is_preprint":false},{"year":2017,"finding":"In human glioma cells, Gab3 knockdown inhibits Akt activation and cell proliferation, while Gab3 overexpression promotes Akt activation and proliferation both in vitro and in vivo in xenograft models.","method":"shRNA/siRNA knockdown, forced overexpression, Akt phosphorylation assay, xenograft tumor model","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 3 — functional KD/OE with defined Akt signaling readout but no direct binding partner identification in this study","pmids":["28291820"],"is_preprint":false},{"year":2026,"finding":"In lung adenocarcinoma, GAB3 interacts with LYN kinase to inhibit the MAPK signaling pathway and reverse epithelial-mesenchymal transition (EMT). GAB3 overexpression also enhances CXCL10 secretion, increases CD8+ T cell infiltration, and sensitizes tumors to anti-PD-1 therapy.","method":"Co-immunoprecipitation (GAB3-LYN interaction), overexpression/knockdown with MAPK and EMT readouts, in vitro and in vivo tumor models, immune cell profiling","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2/3 — Co-IP identifies LYN as binding partner, functional assays with defined MAPK/EMT readouts, single lab","pmids":["42031161"],"is_preprint":false},{"year":2024,"finding":"GAB3 interacts with RSK kinases (p90 ribosomal S6 kinases) through a DDVF-like short linear motif (SLiM), the same interface used by viral and bacterial proteins to hijack RSKs. This interaction was identified by AlphaFold docking and confirmed by co-immunoprecipitation, suggesting GAB3 participates in negative feedback regulation of the RAS-ERK MAPK pathway via RSK.","method":"AlphaFold structural docking, co-immunoprecipitation, SLiM prediction screening of human proteome","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 — single Co-IP confirmation of RSK interaction, functional consequence inferred but not directly demonstrated for GAB3 specifically","pmids":["bio_10.1101_2024.08.08.607128"],"is_preprint":true}],"current_model":"GAB3 is a scaffolding/docking protein that, upon activation by receptors such as M-CSFR or cytokine receptors (IL-2R/IL-15R), becomes tyrosine phosphorylated and assembles signaling complexes containing p85 (PI3K), SHP2, Mona/Gads, LYN kinase, and RSK kinases to activate downstream PI3K/Akt and MAPK/Erk pathways, thereby facilitating macrophage differentiation, NK cell expansion, and immune responses, while also acting as a context-dependent regulator (oncogenic in some cancers, tumor-suppressive in lung adenocarcinoma) of cell proliferation and immune microenvironment remodeling."},"narrative":{"teleology":[{"year":2002,"claim":"Identification of GAB3 as a tyrosine-phosphorylated docking protein that assembles p85/SHP2 complexes downstream of M-CSFR and accelerates macrophage differentiation established its basic molecular architecture and initial function.","evidence":"Co-immunoprecipitation and overexpression in FD-Fms cells with M-CSF stimulation","pmids":["11739737"],"confidence":"High","gaps":["Upstream kinase(s) responsible for GAB3 tyrosine phosphorylation not identified","Whether GAB3 acts through PI3K, SHP2, or both to promote differentiation was not resolved","No in vivo loss-of-function data at this stage"]},{"year":2002,"claim":"Mapping of the GAB3–Mona/Gads interaction via an atypical proline-rich motif and demonstration that specific M-CSFR tyrosines (Y697, Y807) are required for GAB3 phosphorylation defined how receptor signals are transmitted through GAB3.","evidence":"GST pull-down domain mapping, site-directed receptor mutagenesis, Co-IP in bone marrow-derived cells","pmids":["11997510"],"confidence":"High","gaps":["Functional consequence of the Mona/Gads–GAB3 complex for downstream signaling not tested","Whether GAB3 is recruited directly to the receptor or via an intermediary adaptor (e.g., Grb2) was not resolved"]},{"year":2003,"claim":"Gab3 knockout mice revealed that GAB3 is dispensable for normal hematopoiesis and macrophage development, raising the possibility of functional redundancy with GAB1/GAB2 or context-specific roles.","evidence":"Homologous recombination knockout with comprehensive hematopoietic and immune phenotyping","pmids":["12640125"],"confidence":"High","gaps":["Redundancy with GAB1/GAB2 was not formally tested by combinatorial knockouts","Specialized immune challenges (infection, tumor rejection) were not examined","NK cell-specific phenotypes were not assessed"]},{"year":2017,"claim":"Extension of GAB3 function to cancer showed that GAB3 promotes Akt and Erk activation and tumor cell proliferation in colorectal cancer and glioma, confirming its scaffolding role for PI3K/MAPK signaling outside normal hematopoiesis.","evidence":"shRNA knockdown and overexpression in CRC and glioma cells with xenograft models; Co-IP confirmed p85/SHP2 association in CRC","pmids":["28115166","28291820"],"confidence":"Medium","gaps":["Whether GAB3 is amplified, mutated, or transcriptionally upregulated in these cancers was not established","Receptor inputs activating GAB3 in cancer cells not identified","Single-lab findings without independent replication"]},{"year":2019,"claim":"Discovery that GAB3 is selectively required for IL-2/IL-15-driven MAPK (but not STAT5) signaling in NK cells resolved the long-standing question of GAB3's non-redundant physiological function, linking it to missing-self recognition, tumor clearance, and uterine vascular remodeling.","evidence":"Gab3-deficient mice with cytokine stimulation, adoptive transfer, and NK cell functional assays in vivo","pmids":["31375526"],"confidence":"High","gaps":["Mechanism by which GAB3 selectively channels to MAPK rather than STAT5 is unknown","Whether GAB3 directly scaffolds a Ras-activating complex in NK cells was not shown","Human NK cell relevance not demonstrated"]},{"year":2019,"claim":"Combined GAB2/GAB3 knockout revealed redundant suppression of colitis through PI3K/Akt/mTORC1 signaling in macrophages and T cells, demonstrating that GAB family members cooperatively restrain inflammatory responses.","evidence":"Double knockout mice, bone marrow transplantation, intracellular signaling analysis","pmids":["30936879"],"confidence":"Medium","gaps":["GAB3-specific contribution versus GAB2-specific contribution not dissected","Whether the colitis phenotype is driven primarily by macrophage or T cell dysfunction remains unclear","Downstream transcriptional targets of GAB3-dependent mTORC1 signaling not identified"]},{"year":2026,"claim":"Identification of LYN kinase as a GAB3 interaction partner in lung adenocarcinoma, where GAB3 inhibits MAPK/EMT and promotes CD8+ T cell infiltration via CXCL10, revealed a context-dependent tumor-suppressive role contrasting with its oncogenic function in other cancers.","evidence":"Co-immunoprecipitation of GAB3–LYN, overexpression/knockdown with MAPK/EMT and immune profiling readouts in vitro and in vivo","pmids":["42031161"],"confidence":"Medium","gaps":["Whether LYN phosphorylates GAB3 or vice versa is unknown","Mechanism by which GAB3 switches from pro-MAPK to anti-MAPK signaling in different tumor types not resolved","Single-lab study without independent validation"]},{"year":null,"claim":"The structural basis of GAB3's context-dependent signaling — how it activates MAPK/Akt in some settings but inhibits MAPK in others — and the functional significance of its interaction with RSK kinases remain to be established.","evidence":"","pmids":[],"confidence":"Low","gaps":["No crystal or cryo-EM structure of GAB3 or its complexes exists","RSK interaction confirmed only by single Co-IP in a preprint; functional consequence for GAB3 not demonstrated","Human genetic studies linking GAB3 variants to disease are absent"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,1,5]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,5]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,3,5,7]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[3,4]}],"complexes":[],"partners":["PIK3R1","PTPN11","GRAP2","GRB2","LYN"],"other_free_text":[]},"mechanistic_narrative":"GAB3 is a scaffolding adaptor protein of the Grb2-associated binder family that couples cytokine and growth factor receptor signaling to PI3K/Akt and MAPK/Erk pathways in hematopoietic cells. It contains an N-terminal pleckstrin homology domain, multiple tyrosine phosphorylation sites, and proline-rich motifs; upon receptor activation (e.g., M-CSFR, IL-2R/IL-15R), GAB3 is tyrosine phosphorylated and recruits p85 (PI3K), SHP2, and the adaptor Mona/Gads to assemble signaling complexes that drive macrophage differentiation and NK cell expansion [PMID:11739737, PMID:11997510, PMID:31375526]. GAB3-deficient mice are viable with grossly normal hematopoiesis, but show selective impairment of IL-2/IL-15-driven MAPK signaling in NK cells, resulting in defective missing-self recognition, impaired tumor clearance, and aberrant uterine NK cell-mediated spiral artery remodeling; combined loss of GAB2 and GAB3 unmasks redundant roles in suppressing colitis through PI3K/Akt/mTORC1 signaling in macrophages and T cells [PMID:12640125, PMID:31375526, PMID:30936879]. In cancer contexts, GAB3 promotes Akt and Erk activation and tumor cell proliferation in colorectal cancer and glioma, while in lung adenocarcinoma it interacts with LYN kinase to inhibit MAPK signaling and enhance anti-tumor immunity [PMID:28115166, PMID:28291820, PMID:42031161]."},"prefetch_data":{"uniprot":{"accession":"Q8WWW8","full_name":"GRB2-associated-binding protein 3","aliases":["GRB2-associated binder 3","Growth factor receptor bound protein 2-associated protein 3"],"length_aa":586,"mass_kda":65.6,"function":"","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q8WWW8/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GAB3","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/GAB3","total_profiled":1310},"omim":[{"mim_id":"605451","title":"p21 PROTEIN-ACTIVATED KINASE 4; PAK4","url":"https://www.omim.org/entry/605451"},{"mim_id":"314400","title":"CARDIAC VALVULAR DYSPLASIA, X-LINKED; CVDPX","url":"https://www.omim.org/entry/314400"},{"mim_id":"300482","title":"GRB2-ASSOCIATED BINDING PROTEIN 3; GAB3","url":"https://www.omim.org/entry/300482"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nuclear speckles","reliability":"Approved"},{"location":"Nucleoplasm","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"lymphoid tissue","ntpm":13.1}],"url":"https://www.proteinatlas.org/search/GAB3"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q8WWW8","domains":[{"cath_id":"2.30.29.30","chopping":"7-120","consensus_level":"high","plddt":84.5006,"start":7,"end":120}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8WWW8","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8WWW8-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8WWW8-F1-predicted_aligned_error_v6.png","plddt_mean":54.22},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GAB3","jax_strain_url":"https://www.jax.org/strain/search?query=GAB3"},"sequence":{"accession":"Q8WWW8","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8WWW8.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8WWW8/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8WWW8"}},"corpus_meta":[{"pmid":"11739737","id":"PMC_11739737","title":"Gab3, a new DOS/Gab family member, facilitates macrophage differentiation.","date":"2002","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/11739737","citation_count":71,"is_preprint":false},{"pmid":"31375526","id":"PMC_31375526","title":"Gab3 is required for IL-2- and IL-15-induced NK cell expansion and limits trophoblast invasion during pregnancy.","date":"2019","source":"Science immunology","url":"https://pubmed.ncbi.nlm.nih.gov/31375526","citation_count":52,"is_preprint":false},{"pmid":"12640125","id":"PMC_12640125","title":"Gab3-deficient mice exhibit normal development and hematopoiesis and are immunocompetent.","date":"2003","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/12640125","citation_count":45,"is_preprint":false},{"pmid":"11997510","id":"PMC_11997510","title":"Induced expression and association of the Mona/Gads adapter and Gab3 scaffolding protein during monocyte/macrophage differentiation.","date":"2002","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/11997510","citation_count":34,"is_preprint":false},{"pmid":"30936879","id":"PMC_30936879","title":"Gab2 and Gab3 Redundantly Suppress Colitis by Modulating Macrophage and CD8+ T-Cell Activation.","date":"2019","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/30936879","citation_count":14,"is_preprint":false},{"pmid":"28291820","id":"PMC_28291820","title":"Gab3 overexpression in human glioma mediates Akt activation and tumor cell proliferation.","date":"2017","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/28291820","citation_count":12,"is_preprint":false},{"pmid":"28115166","id":"PMC_28115166","title":"Gab3 is required for human colorectal cancer cell proliferation.","date":"2017","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/28115166","citation_count":11,"is_preprint":false},{"pmid":"36227511","id":"PMC_36227511","title":"Silencing Asian Seabass gab3 Inhibits Nervous Necrosis Virus Replication.","date":"2022","source":"Marine biotechnology (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/36227511","citation_count":6,"is_preprint":false},{"pmid":"32473363","id":"PMC_32473363","title":"Characterization of GAB3 and its association with NNV resistance in the Asian seabass.","date":"2020","source":"Fish & shellfish immunology","url":"https://pubmed.ncbi.nlm.nih.gov/32473363","citation_count":6,"is_preprint":false},{"pmid":"38680425","id":"PMC_38680425","title":"Association analysis of polymorphisms in SLK, ARHGEF9, WWC2, GAB3, and FSHR genes with reproductive traits in different sheep breeds.","date":"2024","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/38680425","citation_count":5,"is_preprint":false},{"pmid":"40140746","id":"PMC_40140746","title":"Genetic susceptibility to essential hypertension in the Chinese han population: a study on GAB1, GAB2, and GAB3 gene polymorphisms.","date":"2025","source":"BMC cardiovascular disorders","url":"https://pubmed.ncbi.nlm.nih.gov/40140746","citation_count":0,"is_preprint":false},{"pmid":"42031161","id":"PMC_42031161","title":"GAB3 suppresses lung adenocarcinoma progression by inhibiting the MAPK signaling and potentiating CD8+ T cell immunity.","date":"2026","source":"Cancer letters","url":"https://pubmed.ncbi.nlm.nih.gov/42031161","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.08.08.607128","title":"The “DDVF” motif used by viral and bacterial proteins to hijack RSK kinases evolved as a mimic of a short linear motif (SLiM) found in proteins related to the RAS-ERK MAP kinase pathway","date":"2024-08-08","source":"bioRxiv","url":"https://doi.org/10.1101/2024.08.08.607128","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.07.23.604849","title":"Genetic Architecture and Analysis Practices of Circulating Metabolites in the NHLBI Trans-Omics for Precision Medicine (TOPMed) Program","date":"2024-07-24","source":"bioRxiv","url":"https://doi.org/10.1101/2024.07.23.604849","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8573,"output_tokens":2476,"usd":0.031429},"stage2":{"model":"claude-opus-4-6","input_tokens":5764,"output_tokens":2363,"usd":0.131843},"total_usd":0.163272,"stage1_batch_id":"msgbatch_0118RScg3WGaGkaZRtWZbtce","stage2_batch_id":"msgbatch_01Cpfzvtbj42aqp5oYZ5Te2s","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2002,\n      \"finding\": \"Gab3 contains an amino-terminal pleckstrin homology (PH) domain, multiple tyrosine phosphorylation sites, SH2 domain binding sites, and two polyproline motifs. Upon M-CSF receptor (Fms) stimulation, Gab3 is tyrosine phosphorylated and associates transiently with p85 (PI3K regulatory subunit) and SHP2. Overexpression of Gab3 in FD-Fms cells dramatically accelerates macrophage differentiation upon M-CSF stimulation.\",\n      \"method\": \"Co-immunoprecipitation, overexpression in FDC-P1/FD-Fms cell lines, tyrosine phosphorylation assay, mRNA expression analysis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP showing p85/SHP2 association, functional overexpression with defined differentiation phenotype, replicated in multiple cell contexts\",\n      \"pmids\": [\"11739737\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Gab3 specifically interacts with the adapter protein Mona/Gads during monocyte/macrophage differentiation. This interaction is mediated by the C-terminal SH3 domain of Mona and the atypical proline-rich domain of Gab3. Gab3 does not interact with the related adapter Grb2 via Mona but does form a complex with Grb2. The M-CSF receptor mutation Y697F impairs Gab3 tyrosine phosphorylation and reduces Mona induction, while Y807F (differentiation-defective) also fails to induce Mona expression.\",\n      \"method\": \"GST pull-down, co-immunoprecipitation, site-directed mutagenesis of M-CSF receptor (Y697F, Y807F), immunoblotting\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — GST pull-down domain mapping combined with receptor mutagenesis and Co-IP in primary bone marrow cells\",\n      \"pmids\": [\"11997510\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Gab3-deficient mice generated by homologous recombination develop normally with no impairment in macrophage differentiation or numbers, no compensation by Gab1 or Gab2 upregulation, and no major immune deficiency in T- or B-lymphocyte responses, indicating Gab3 is dispensable for normal hematopoiesis in vivo.\",\n      \"method\": \"Homologous recombination knockout, monoclonal antibody generation, immunoblotting, detailed hematopoietic and immune phenotyping\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — rigorous genetic knockout with comprehensive phenotypic analysis across multiple cell lineages\",\n      \"pmids\": [\"12640125\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Gab3 is required for IL-2- and IL-15-induced NK cell expansion. Loss of Gab3 causes selective impairment of MAPK signaling but not STAT5 signaling downstream of these cytokines. Gab3-deficient mice show impaired NK cell-mediated elimination of missing-self and tumor targets, and impaired uterine NK cell expansion leading to defective spiral artery remodeling and increased trophoblast invasion.\",\n      \"method\": \"Gab3-deficient mouse model (in vivo and ex vivo), cytokine stimulation with signaling readouts (MAPK, STAT5), adoptive transfer, NK cell functional assays\",\n      \"journal\": \"Science immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with defined signaling pathway dissection (MAPK vs. STAT5) and multiple functional readouts in vivo\",\n      \"pmids\": [\"31375526\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Gab2 and Gab3 redundantly suppress colitis by modulating macrophage and CD8+ T-cell activation. Double knockout (Gab2/3-/-) mice develop spontaneous colitis with reduced PI3-kinase/Akt/mTORC1 signaling in macrophages and T-cells, and increased pSTAT5 in IL-2-stimulated T-cells. Reciprocal bone marrow transplantation demonstrated a hematopoietic disease-initiating mechanism.\",\n      \"method\": \"Double knockout mouse generation, bone marrow transplantation, adoptive transfer, intracellular signaling analysis (PI3K/Akt/mTORC1, STAT5)\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic double KO with epistasis and signaling readouts, but redundancy complicates Gab3-specific conclusions\",\n      \"pmids\": [\"30936879\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"In colorectal cancer cells, Gab3 co-precipitates with p85 and SHP2, and is required for downstream Akt and Erk activation. Gab3 knockdown inhibits both Akt and Erk activation, while overexpression augments them, promoting CRC cell proliferation in vitro and tumor growth in vivo.\",\n      \"method\": \"Co-immunoprecipitation, shRNA knockdown, overexpression, xenograft tumor model, Akt/Erk phosphorylation assays\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — Co-IP confirms p85/SHP2 complex, functional KD/OE with signaling readout, single lab\",\n      \"pmids\": [\"28115166\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"In human glioma cells, Gab3 knockdown inhibits Akt activation and cell proliferation, while Gab3 overexpression promotes Akt activation and proliferation both in vitro and in vivo in xenograft models.\",\n      \"method\": \"shRNA/siRNA knockdown, forced overexpression, Akt phosphorylation assay, xenograft tumor model\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — functional KD/OE with defined Akt signaling readout but no direct binding partner identification in this study\",\n      \"pmids\": [\"28291820\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"In lung adenocarcinoma, GAB3 interacts with LYN kinase to inhibit the MAPK signaling pathway and reverse epithelial-mesenchymal transition (EMT). GAB3 overexpression also enhances CXCL10 secretion, increases CD8+ T cell infiltration, and sensitizes tumors to anti-PD-1 therapy.\",\n      \"method\": \"Co-immunoprecipitation (GAB3-LYN interaction), overexpression/knockdown with MAPK and EMT readouts, in vitro and in vivo tumor models, immune cell profiling\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — Co-IP identifies LYN as binding partner, functional assays with defined MAPK/EMT readouts, single lab\",\n      \"pmids\": [\"42031161\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"GAB3 interacts with RSK kinases (p90 ribosomal S6 kinases) through a DDVF-like short linear motif (SLiM), the same interface used by viral and bacterial proteins to hijack RSKs. This interaction was identified by AlphaFold docking and confirmed by co-immunoprecipitation, suggesting GAB3 participates in negative feedback regulation of the RAS-ERK MAPK pathway via RSK.\",\n      \"method\": \"AlphaFold structural docking, co-immunoprecipitation, SLiM prediction screening of human proteome\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single Co-IP confirmation of RSK interaction, functional consequence inferred but not directly demonstrated for GAB3 specifically\",\n      \"pmids\": [\"bio_10.1101_2024.08.08.607128\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"GAB3 is a scaffolding/docking protein that, upon activation by receptors such as M-CSFR or cytokine receptors (IL-2R/IL-15R), becomes tyrosine phosphorylated and assembles signaling complexes containing p85 (PI3K), SHP2, Mona/Gads, LYN kinase, and RSK kinases to activate downstream PI3K/Akt and MAPK/Erk pathways, thereby facilitating macrophage differentiation, NK cell expansion, and immune responses, while also acting as a context-dependent regulator (oncogenic in some cancers, tumor-suppressive in lung adenocarcinoma) of cell proliferation and immune microenvironment remodeling.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"GAB3 is a scaffolding adaptor protein of the Grb2-associated binder family that couples cytokine and growth factor receptor signaling to PI3K/Akt and MAPK/Erk pathways in hematopoietic cells. It contains an N-terminal pleckstrin homology domain, multiple tyrosine phosphorylation sites, and proline-rich motifs; upon receptor activation (e.g., M-CSFR, IL-2R/IL-15R), GAB3 is tyrosine phosphorylated and recruits p85 (PI3K), SHP2, and the adaptor Mona/Gads to assemble signaling complexes that drive macrophage differentiation and NK cell expansion [PMID:11739737, PMID:11997510, PMID:31375526]. GAB3-deficient mice are viable with grossly normal hematopoiesis, but show selective impairment of IL-2/IL-15-driven MAPK signaling in NK cells, resulting in defective missing-self recognition, impaired tumor clearance, and aberrant uterine NK cell-mediated spiral artery remodeling; combined loss of GAB2 and GAB3 unmasks redundant roles in suppressing colitis through PI3K/Akt/mTORC1 signaling in macrophages and T cells [PMID:12640125, PMID:31375526, PMID:30936879]. In cancer contexts, GAB3 promotes Akt and Erk activation and tumor cell proliferation in colorectal cancer and glioma, while in lung adenocarcinoma it interacts with LYN kinase to inhibit MAPK signaling and enhance anti-tumor immunity [PMID:28115166, PMID:28291820, PMID:42031161].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Identification of GAB3 as a tyrosine-phosphorylated docking protein that assembles p85/SHP2 complexes downstream of M-CSFR and accelerates macrophage differentiation established its basic molecular architecture and initial function.\",\n      \"evidence\": \"Co-immunoprecipitation and overexpression in FD-Fms cells with M-CSF stimulation\",\n      \"pmids\": [\"11739737\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Upstream kinase(s) responsible for GAB3 tyrosine phosphorylation not identified\",\n        \"Whether GAB3 acts through PI3K, SHP2, or both to promote differentiation was not resolved\",\n        \"No in vivo loss-of-function data at this stage\"\n      ]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Mapping of the GAB3–Mona/Gads interaction via an atypical proline-rich motif and demonstration that specific M-CSFR tyrosines (Y697, Y807) are required for GAB3 phosphorylation defined how receptor signals are transmitted through GAB3.\",\n      \"evidence\": \"GST pull-down domain mapping, site-directed receptor mutagenesis, Co-IP in bone marrow-derived cells\",\n      \"pmids\": [\"11997510\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Functional consequence of the Mona/Gads–GAB3 complex for downstream signaling not tested\",\n        \"Whether GAB3 is recruited directly to the receptor or via an intermediary adaptor (e.g., Grb2) was not resolved\"\n      ]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Gab3 knockout mice revealed that GAB3 is dispensable for normal hematopoiesis and macrophage development, raising the possibility of functional redundancy with GAB1/GAB2 or context-specific roles.\",\n      \"evidence\": \"Homologous recombination knockout with comprehensive hematopoietic and immune phenotyping\",\n      \"pmids\": [\"12640125\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Redundancy with GAB1/GAB2 was not formally tested by combinatorial knockouts\",\n        \"Specialized immune challenges (infection, tumor rejection) were not examined\",\n        \"NK cell-specific phenotypes were not assessed\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Extension of GAB3 function to cancer showed that GAB3 promotes Akt and Erk activation and tumor cell proliferation in colorectal cancer and glioma, confirming its scaffolding role for PI3K/MAPK signaling outside normal hematopoiesis.\",\n      \"evidence\": \"shRNA knockdown and overexpression in CRC and glioma cells with xenograft models; Co-IP confirmed p85/SHP2 association in CRC\",\n      \"pmids\": [\"28115166\", \"28291820\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether GAB3 is amplified, mutated, or transcriptionally upregulated in these cancers was not established\",\n        \"Receptor inputs activating GAB3 in cancer cells not identified\",\n        \"Single-lab findings without independent replication\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Discovery that GAB3 is selectively required for IL-2/IL-15-driven MAPK (but not STAT5) signaling in NK cells resolved the long-standing question of GAB3's non-redundant physiological function, linking it to missing-self recognition, tumor clearance, and uterine vascular remodeling.\",\n      \"evidence\": \"Gab3-deficient mice with cytokine stimulation, adoptive transfer, and NK cell functional assays in vivo\",\n      \"pmids\": [\"31375526\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Mechanism by which GAB3 selectively channels to MAPK rather than STAT5 is unknown\",\n        \"Whether GAB3 directly scaffolds a Ras-activating complex in NK cells was not shown\",\n        \"Human NK cell relevance not demonstrated\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Combined GAB2/GAB3 knockout revealed redundant suppression of colitis through PI3K/Akt/mTORC1 signaling in macrophages and T cells, demonstrating that GAB family members cooperatively restrain inflammatory responses.\",\n      \"evidence\": \"Double knockout mice, bone marrow transplantation, intracellular signaling analysis\",\n      \"pmids\": [\"30936879\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"GAB3-specific contribution versus GAB2-specific contribution not dissected\",\n        \"Whether the colitis phenotype is driven primarily by macrophage or T cell dysfunction remains unclear\",\n        \"Downstream transcriptional targets of GAB3-dependent mTORC1 signaling not identified\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Identification of LYN kinase as a GAB3 interaction partner in lung adenocarcinoma, where GAB3 inhibits MAPK/EMT and promotes CD8+ T cell infiltration via CXCL10, revealed a context-dependent tumor-suppressive role contrasting with its oncogenic function in other cancers.\",\n      \"evidence\": \"Co-immunoprecipitation of GAB3–LYN, overexpression/knockdown with MAPK/EMT and immune profiling readouts in vitro and in vivo\",\n      \"pmids\": [\"42031161\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether LYN phosphorylates GAB3 or vice versa is unknown\",\n        \"Mechanism by which GAB3 switches from pro-MAPK to anti-MAPK signaling in different tumor types not resolved\",\n        \"Single-lab study without independent validation\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The structural basis of GAB3's context-dependent signaling — how it activates MAPK/Akt in some settings but inhibits MAPK in others — and the functional significance of its interaction with RSK kinases remain to be established.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No crystal or cryo-EM structure of GAB3 or its complexes exists\",\n        \"RSK interaction confirmed only by single Co-IP in a preprint; functional consequence for GAB3 not demonstrated\",\n        \"Human genetic studies linking GAB3 variants to disease are absent\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 3, 5, 7]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [3, 4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"PIK3R1\",\n      \"PTPN11\",\n      \"GRAP2\",\n      \"GRB2\",\n      \"LYN\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}