{"gene":"RAPGEF1","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":1994,"finding":"C3G (RAPGEF1) was identified as a guanine nucleotide-releasing protein that binds to the SH3 domains of CRK and GRB2/ASH adaptor proteins via a proline-rich sequence in its center region. The C-terminal region of C3G shows homology to GNRPs for Ras and complemented loss of CDC25 function in yeast.","method":"Bacterial fusion protein pull-down, mutational analysis, yeast complementation assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — direct binding assays, mutational mapping, and functional complementation in yeast; replicated by multiple subsequent studies","pmids":["7512734"],"is_preprint":false},{"year":1994,"finding":"Four proline-rich sequences in the center region of C3G each individually bind to the N-terminal SH3 domain of c-Crk and v-Crk with high specificity and preferentially over other SH3 domains (including Grb2 SH3). Endogenous C3G co-precipitates with Crk from cell lysates.","method":"GST pull-down, in vitro binding assays, co-precipitation from cell lysates","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal pull-downs with mutational mapping, replicated across labs","pmids":["7806500"],"is_preprint":false},{"year":1995,"finding":"C3G is a specific guanine nucleotide exchange factor (GEF) for Rap1: it markedly stimulated GDP dissociation and GTP-γS binding to Rap1B in vitro, and induced accumulation of GTP-bound Rap1A in COS7 cells in vivo, while having only marginal effects on Ha-Ras, N-Ras, and RalA.","method":"In vitro GEF assay (GDP dissociation, GTP-γS binding), in vivo GTP-loading assay in COS7 cells","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution plus in vivo confirmation, replicated extensively","pmids":["8524240"],"is_preprint":false},{"year":1996,"finding":"Following T cell receptor activation, Cbl becomes tyrosine phosphorylated and associates with CrkL via the Crk SH2 domain (inhibitable by pYDVP phosphopeptide); CrkL constitutively associates with C3G, and a fraction of C3G co-immunoprecipitates with Cbl in activated Jurkat T cells.","method":"Co-immunoprecipitation, phosphopeptide competition assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — co-IP in T cells with phosphopeptide competition, single lab","pmids":["8626543"],"is_preprint":false},{"year":1996,"finding":"C3G selectively binds to the amino-terminal SH3 domain of Grb2 in vitro, but in primary B cells C3G associates constitutively with the CrkL adaptor rather than with Grb2, Shc, or CrkII, both before and after BCR stimulation.","method":"Yeast two-hybrid, GST fusion protein pull-down, co-immunoprecipitation from B cells","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — in vitro binding confirmed by in vivo co-IP; some discordance between in vitro and in vivo results","pmids":["8621483"],"is_preprint":false},{"year":1997,"finding":"Expression of Crk, CrkL, and Grb2 with C3G enhances C3G GEF activity toward Rap1 in vivo primarily by recruiting C3G to the cell membrane, not by allosteric activation; membrane targeting of Crk (farnesylation signal) compensated for the SH2 domain requirement, and Crk did not stimulate C3G GEF activity in vitro.","method":"In vivo Rap1 GTP-loading assay, in vitro GEF assay, dominant-negative and membrane-targeting constructs in COS1 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — combined in vitro and in vivo assays with domain mutants clarifying mechanism","pmids":["9268367"],"is_preprint":false},{"year":1997,"finding":"v-Crk activates JNK via C3G: coexpression of C3G with v-Crk further enhanced JNK activity and transformation, while a dominant-negative C3G lacking the GEF domain abolished v-Crk-induced JNK activity and colony formation in NIH 3T3 cells.","method":"JNK kinase assay, dominant-negative C3G expression, colony formation assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional assays with dominant-negative constructs, single lab","pmids":["9122199"],"is_preprint":false},{"year":1997,"finding":"Insulin and EGF stimulation induces dissociation of the CrkII-C3G complex, correlating with a conformational change in Rap1; dissociation is driven by tyrosine phosphorylation of CrkII at Tyr221 (mutation Y221F prevents insulin-induced dissociation), and is reversed by PTP1B-mediated dephosphorylation.","method":"Co-immunoprecipitation, GST-C3G pull-down, mutagenesis, PTP1B dephosphorylation assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro reconstitution of dissociation, phospho-site mutagenesis, single lab","pmids":["9353263"],"is_preprint":false},{"year":1998,"finding":"p130Cas SH3 domain directly binds C3G via a proline-rich site (APPKPPLP) N-terminal to the Crk-binding motifs; mutational analysis defined Pro1, Lys3, and Pro4 as critical for high-affinity interaction (consensus CasSH3-binding motif: XXPXKPX).","method":"Yeast two-hybrid, in vitro pull-down, in vivo co-immunoprecipitation, deletion/point mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — direct binding confirmed in vitro and in vivo with extensive mutagenesis","pmids":["9748234"],"is_preprint":false},{"year":1998,"finding":"Transformation suppressor activity of C3G maps to its N-terminal Crk-binding (SH3-b) domain and is independent of the catalytic CDC25-H domain; a C3G mutant lacking the catalytic domain (C3GΔCat) suppressed Ras/Raf/Sis oncogene-induced focus formation as effectively as full-length C3G.","method":"Focus formation assay, NIH3T3 transfection with deletion mutants","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional assay with multiple deletion constructs, single lab","pmids":["9482107"],"is_preprint":false},{"year":1998,"finding":"C3G activates JNK1 through a Ras-independent pathway involving MLK family kinases (MLK3 and DLK): dominant-negative MLK3 and DLK blocked C3G-induced JNK1 activation, while dominant-negative Ras, Rac, or Pak did not.","method":"JNK1 kinase assay, dominant-negative constructs, co-expression in 293T cells","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis by dominant-negative constructs, single lab","pmids":["9430657"],"is_preprint":false},{"year":1998,"finding":"Integrin-mediated cell adhesion to fibronectin induces tyrosine phosphorylation of C3G via CrkL in a cytoskeleton-dependent manner in normal 3T3 fibroblasts; this pathway is disrupted in Bcr/Abl-expressing cells, which show reduced CrkL-C3G complex formation.","method":"Co-immunoprecipitation, tyrosine phosphorylation assay, cytoskeletal disruption experiments","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — co-IP with cytoskeletal manipulation, single lab","pmids":["9840945"],"is_preprint":false},{"year":1999,"finding":"C3G is activated by CrkI-mediated tyrosine phosphorylation at tyrosine 504: the C3G-Y504F mutant was markedly less phosphorylated and less activated by CrkI expression. Phosphorylation at Y504 relieves a cis-acting negative regulatory domain (aa 391–579) outside the catalytic region.","method":"Systematic mutagenesis of all 7 tyrosines in aa 391-579, CrkI co-expression, Rap1-GTP loading assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — systematic site-directed mutagenesis with in vivo GEF activity assay; replicated by multiple subsequent studies","pmids":["10318861"],"is_preprint":false},{"year":1999,"finding":"The CrkL-C3G complex mediates integrin-dependent hematopoietic cell adhesion to fibronectin via VLA-4 and VLA-5; the GEF activity of C3G is required (GEF-dead mutant abrogates CrkL-induced adhesion), and the N-terminal SH3 domain of CrkL (C3G-binding domain) is critical.","method":"Overexpression of C3G and deletion mutants, integrin-blocking antibodies, flow cytometry","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional cell adhesion assay with domain mutants, single lab","pmids":["10339478"],"is_preprint":false},{"year":1999,"finding":"The CrkL-C3G complex links Cbl to downstream signaling after integrin ligation; overexpression of C3G (identified as the major CrkL SH3 N-terminal binding protein) enhances spontaneous migration of Ba/F3 hematopoietic cells.","method":"Co-immunoprecipitation, GFP-fusion migration assay, domain deletion analysis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — co-IP and functional migration assay with domain mutants, single lab","pmids":["10608804"],"is_preprint":false},{"year":1999,"finding":"CrkL mediates Ras-dependent activation of the Raf/ERK pathway through C3G in hematopoietic cells stimulated with erythropoietin or IL-3; C3G GEF domain is required (GEF-dead mutant is inhibitory), and dominant-negative Ras blocks CrkL/C3G-induced ERK2 and Elk-1 activation.","method":"ERK1/2 kinase assay, Elk-1 reporter assay, Ras activation assay, dominant-negative constructs","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis with dominant-negative Ras plus GEF-domain requirement, single lab","pmids":["10514505"],"is_preprint":false},{"year":2000,"finding":"C3G activates JNK via R-Ras (not Rap1): constitutively active R-Ras activated JNK while Rap1(Val-12) did not; dominant-negative R-Ras blocked v-Crk-induced JNK activation and transformation; among Rap1-specific GEFs (CalDAG-GEFI, Epac), none activated JNK.","method":"JNK kinase assay, dominant-negative R-Ras, GEF specificity panel, NIH3T3 flat reversion assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis with dominant-negatives and GEF panel, single lab","pmids":["10777559"],"is_preprint":false},{"year":2000,"finding":"Formation of the CrkII-C3G complex is regulated by integrins and inversely correlates with ERK activation: suspended cells (low ERK) contain a CrkII-C3G complex with elevated Rap1-GTP, while adherent cells (high ERK) dissociate the complex; CrkII Y109L mutation disrupts the complex and activates ERK; PTP1B C215S also disrupts the complex.","method":"Co-immunoprecipitation, Rap1-GTP pull-down, overexpression in CHO cells","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — correlative co-IP with gain-of-function constructs, single lab","pmids":["10777617"],"is_preprint":false},{"year":2000,"finding":"IFN-γ activates a signaling cascade in which c-Cbl is tyrosine phosphorylated, recruits CrkL via its SH2 domain, and CrkL then promotes activation of C3G (constitutively bound to CrkL via N-terminal SH3) leading to Rap1 activation.","method":"Co-immunoprecipitation, Rap1 activation assay, tyrosine phosphorylation assay","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — co-IP and Rap1 activation in NB-4 cells, single lab","pmids":["10657627"],"is_preprint":false},{"year":2001,"finding":"C3G-dependent activation of Rap1 is required for cell adhesion and early mouse embryogenesis: C3G knockout mice die before E7.5; C3G-deficient fibroblasts show impaired cell adhesion, delayed spreading, and accelerated migration, which are rescued by active Rap1, Rap2, R-Ras, or other Rap1 GEFs (Epac, CalDAG-GEFI).","method":"Knockout mouse model, Cre-lox conditional deletion, Rap1 GTP-loading assay, cell adhesion and migration assays","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic rescue experiments with multiple GEFs plus KO phenotype; functional equivalence of Rap1 activation confirmed","pmids":["11432821"],"is_preprint":false},{"year":2003,"finding":"Hck tyrosine kinase directly interacts with C3G via its SH3 domain binding to the proline-rich region of C3G; co-expression of Hck and C3G induces caspase-1, -8, and -9-mediated apoptosis requiring Hck catalytic activity but not C3G GEF domain or Y504 phosphorylation. Hck phosphorylates C3G at Y504 in cells.","method":"Co-immunoprecipitation, SH3 domain-based interaction cloning, apoptosis assay, dominant-negative caspase constructs, phosphorylation assay with kinase-dead Hck","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct interaction and functional assays with multiple controls, single lab","pmids":["14551197"],"is_preprint":false},{"year":2003,"finding":"C3G is required for vascular maturation and focal adhesion formation in mouse development: hypomorphic C3G embryos die ~E11.5 with vascular defects; C3G-deficient fibroblasts lack paxillin/integrin-β1-positive focal adhesions (but not integrin-β3-positive ones) and show abnormal PDGF-BB responses.","method":"Hypomorphic knock-in mouse model, immunofluorescence for focal adhesion markers, PDGF response assays","journal":"Development","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetic model with specific cellular mechanistic readout","pmids":["12466202"],"is_preprint":false},{"year":2004,"finding":"Tyrosine-phosphorylated C3G (pY504) localizes predominantly to the Golgi complex and subcortical actin cytoskeleton when phosphorylated by Hck or Src; cytoskeletal disruption by cytochalasin D abolishes peripheral pY504-C3G staining without affecting Golgi localization, suggesting spatially restricted activation.","method":"Immunofluorescence with phospho-specific antibody (pY504), cytochalasin D treatment, subcellular fractionation","journal":"BMC cell biology","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — direct localization with phospho-specific antibody and pharmacological perturbation, single lab","pmids":["15320955"],"is_preprint":false},{"year":2004,"finding":"Reelin stimulation of cortical neurons activates a Dab1→CrkL/CrkI/CrkII→C3G→Rap1 signaling pathway: Reelin induces Crk family binding to phospho-Dab1 at Y220 and Y232, induces tyrosine phosphorylation of C3G, and activates Rap1.","method":"Phospho-affinity pull-down from embryonic brain extract, co-immunoprecipitation, Rap1-GTP assay, cortical neuron culture","journal":"Current biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — biochemical pathway reconstitution in primary neurons plus identification of critical phospho-residues","pmids":["15062102"],"is_preprint":false},{"year":2004,"finding":"In nectin-based cell-cell adhesion, Rap1 is activated via a c-Src-Crk-C3G signaling cascade at cell-cell contact sites; Rap1 activation (together with c-Src) is required for FRG-mediated Cdc42 activation and formation of adherens junctions. Inhibiting Crk, C3G, or Rap1 reduced AJ formation.","method":"Co-immunoprecipitation, dominant-negative constructs, Rap1 activation assay, immunofluorescence of AJ markers","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis with dominant-negatives and co-IP, single lab","pmids":["15504743"],"is_preprint":false},{"year":2004,"finding":"C3G suppresses oncogene-induced ERK activation and cyclin A expression via its N-terminal Crk-binding domain independent of GEF activity; C3G and C3GΔCat interact with PP2A phosphatases (confirmed by co-immunoprecipitation) and increase ERK-associated PP2A activity at the subcortical actin cytoskeleton.","method":"ERK phosphorylation assay, focus formation assay, soft agar assay, co-immunoprecipitation with PP2A, PP2A phosphatase activity assay, okadaic acid treatment","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (co-IP + phosphatase assay + pharmacological inhibition), single lab","pmids":["15077165","17825818"],"is_preprint":false},{"year":2006,"finding":"C3G controls the size of the cerebral cortical neural precursor population by inhibiting the Ras/Akt pathway: C3G-deficient neuroepithelial cells show overproliferation, nuclear β-catenin accumulation, Akt/PKB activation, GSK3β inhibition, and fail to exit the cell cycle in response to growth factors.","method":"Conditional knockout mouse, Rap1 GTP-loading assay, Akt and GSK3β phosphorylation assays, β-catenin localization","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo KO with defined molecular pathway and in vitro mechanistic follow-up","pmids":["16858399"],"is_preprint":false},{"year":2006,"finding":"A novel truncated C3G isoform, p87C3G, is overexpressed in CML cells and co-immunoprecipitates with Bcr-Abl; the interaction involves the SH3-binding domain (first polyproline region) of p87C3G and the SH3 domain of Abl, and Bcr-Abl phosphorylates p87C3G in vitro.","method":"Co-immunoprecipitation, in vitro pull-down, in vitro kinase assay, domain mutagenesis","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP with in vitro kinase assay, single lab","pmids":["16443220"],"is_preprint":false},{"year":2007,"finding":"C3G is required for c-Abl-induced filopodia formation during cell spreading on fibronectin; C3G promotes filopodia in a manner requiring Abl catalytic activity and N-WASP function but independent of Rho/Rac/Cdc42 dominant-negative inhibition. Cellular C3G interacts with c-Abl and enhances c-Abl cytoplasmic localization.","method":"RNAi knockdown, overexpression, dominant-negative GTPases, wiskostatin pharmacological inhibition, co-immunoprecipitation, immunofluorescence","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi plus pharmacological epistasis, single lab","pmids":["17475248"],"is_preprint":false},{"year":2008,"finding":"C3G is essential for cortical neuron migration and preplate splitting during brain development; C3G is activated by reelin in cortical neurons leading to Rap1 activation; C3G-deficient neurons arrest in a multipolar state and fail to migrate, with disrupted basement membrane and radial glial processes.","method":"Conditional KO mouse, Rap1 GTP-loading assay after reelin stimulation, in utero live imaging, immunofluorescence","journal":"Development","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetic model with defined reelin-C3G-Rap1 pathway and multiple cellular readouts","pmids":["18506028"],"is_preprint":false},{"year":2008,"finding":"WAVE2 complex regulates TCR-stimulated Rap1 activation via recruitment and activation of the CrkL-C3G exchange complex; Abl tyrosine kinase (associated with WAVE2) phosphorylates C3G on tyrosine, which is required for C3G GEF activity toward Rap1, leading to integrin clustering and affinity maturation.","method":"Co-immunoprecipitation, membrane recruitment assay, Rap1 activation assay, Abl kinase inhibitor, siRNA knockdown","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP with functional assays and pharmacological/genetic perturbations, single lab","pmids":["18809728"],"is_preprint":false},{"year":2008,"finding":"C3G promotes neurite growth in human neuroblastoma cells dependent on both its catalytic domain and N-terminal regulatory domain, requiring Cdc42 and Rap1 function; C3G knockdown inhibits forskolin- and NGF-induced differentiation; C3G is phosphorylated at Y504 predominantly in the Golgi upon forskolin/NGF treatment; C3G expression induces the cell cycle inhibitor p21.","method":"Overexpression and shRNA knockdown, dominant-negative GTPases, phospho-Y504 immunofluorescence, differentiation assays in IMR-32 cells","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi and overexpression with multiple functional readouts, single lab","pmids":["18957052"],"is_preprint":false},{"year":2010,"finding":"c-Abl phosphorylates C3G at Y504 in response to oxidative stress; this phosphorylation is dependent on the F-actin-binding domain (FABD) of c-Abl and is restricted to F-actin-rich regions; C3G knockdown or dominant-negative C3G inhibits c-Abl-mediated apoptosis.","method":"In vivo phosphorylation assay, FABD deletion mutant, RNAi, dominant-negative C3G, cytoskeletal fractionation","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain mutant analysis with functional apoptosis readout, single lab","pmids":["20581864"],"is_preprint":false},{"year":2010,"finding":"Drosophila C3G is a Rap1-specific GEF (stimulates nucleotide exchange on Drosophila Rap GTPases in vitro) required for body wall muscle integrity and proper βPS integrin localization at muscle attachment sites during larval stages.","method":"In vitro GEF assay with Drosophila Rap GTPases, genetic deletion of C3G locus, in situ hybridization, immunofluorescence","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro GEF reconstitution plus in vivo genetic model with defined phenotype","pmids":["20209136"],"is_preprint":false},{"year":2010,"finding":"ALK receptor tyrosine kinase activates Rap1 via C3G: activated ALK recruits a constitutive CrkL-C3G complex; siRNA knockdown of C3G or Rap1 inhibits ALK-induced neurite outgrowth and neuroblastoma cell proliferation.","method":"Co-immunoprecipitation, Rap1 activation assay, siRNA knockdown, Rap1GAP overexpression","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP with functional siRNA knockdown assays, single lab","pmids":["20190816"],"is_preprint":false},{"year":2011,"finding":"Lyn tyrosine kinase controls spatial activation of Rap1 at the neutrophil leading edge by recruiting the CrkL-C3G complex; depletion of Lyn prevents chemoattractant-induced Rap1 activation at the leading edge, rescued by ectopic Rap1 expression.","method":"RNAi depletion of Lyn, Rap1 activation assay, live imaging of leading edge localization, epistasis with Rap1 rescue","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi epistasis with rescue, functional localization data, single lab","pmids":["21628423"],"is_preprint":false},{"year":2011,"finding":"TC-PTP (TC48 isoform) dephosphorylates C3G at Y504: TC48 interacts with C3G via its C-terminal non-catalytic residues and the Crk-binding region of C3G; a substrate-trap mutant of TC48 preferentially binds phospho-C3G at the Golgi; TC48 expression abrogates Src- and pervanadate-induced C3G phosphorylation and inhibits neurite outgrowth.","method":"Co-immunoprecipitation, substrate-trap mutant, in vitro dephosphorylation, IGF-induced dephosphorylation, neurite outgrowth assay","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — substrate-trap approach with functional validation, single lab","pmids":["21876762"],"is_preprint":false},{"year":2012,"finding":"C3G plays a role in platelet clotting through its GEF activity: transgenic mice overexpressing C3G in platelets showed shorter bleeding times and stronger platelet activation, while tgC3GΔCat (GEF-dead) mice showed a bleeding diathesis; C3G is a mediator in the PKC pathway leading to Rap1 activation in platelets.","method":"Transgenic mouse model (platelet-specific), bleeding time assay, platelet aggregation assay, Rap1 activation assay","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo transgenic model with GEF-dead control and multiple functional readouts","pmids":["22659131"],"is_preprint":false},{"year":2012,"finding":"C3G forms a complex with Bcr-Abl and p38α MAPK at focal adhesions in CML cells; interactions involve SH3/SH3-b domains with CrkL, p130Cas, Cbl, and Abi1; C3G, Abi1, or Cbl knockdown impairs adhesion to fibronectin; C3G and p38α act through a common pathway to regulate K562 cell adhesion.","method":"Co-immunoprecipitation, immunofluorescence, siRNA knockdown, cell adhesion assay","journal":"Cell communication and signaling","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — co-IP confirmed by immunofluorescence with RNAi knockdown, single lab","pmids":["23343344"],"is_preprint":false},{"year":2012,"finding":"C3G functions as a negative regulator of β-catenin: C3G is present in a complex with β-catenin (via its proline-rich Crk-binding region interacting with β-catenin residues 90-525); C3G overexpression destabilizes β-catenin and reduces its nuclear accumulation and TCF transcription activity independent of GEF activity and GSK3β; β-catenin reciprocally represses C3G expression.","method":"Co-immunoprecipitation, deletion mutant mapping, TCF reporter assay, Western blot for β-catenin stability, proteasome inhibitor treatment","journal":"Genes & cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP with domain mapping and functional reporter assay, single lab","pmids":["23486661"],"is_preprint":false},{"year":2014,"finding":"CTLA-4 receptor signaling mediates tyrosine phosphorylation of C3G (facilitated by Hck), which is required for augmented Rap1 activation and LFA-1-mediated T-cell adhesion; C3G translocates to the plasma membrane downstream of TCR signaling in a Zap70-dependent manner.","method":"Co-immunoprecipitation, Rap1 activation assay, C3G membrane translocation assay, siRNA knockdown, Zap70 inhibitor","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional signaling pathway assays with pharmacological/genetic perturbations, single lab","pmids":["24396067"],"is_preprint":false},{"year":2014,"finding":"Immunophilin cyclophilin A increases C3G binding to CrkII, while immunophilin inhibitors (CsA, FK506) inhibit CrkII-C3G association by promoting cis-conformation of CrkII (detected by FRET); suppression of CrkII-C3G complex by immunophilin inhibitors impairs T cell adhesion to fibronectin and migration toward SDF-1α.","method":"Co-immunoprecipitation, FRET-based PICCHU assay, T cell adhesion and migration assay","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — FRET conformational assay with functional cell assays, single lab","pmids":["25225668"],"is_preprint":false},{"year":2015,"finding":"C3G-mediated Rap1 activation promotes secretion of MMP-2 and MMP-9 in ovarian cancer cells; C3G knockdown suppresses Rap1 activity and reduces MMP-2 and MMP-9 secretion as well as cell invasion.","method":"siRNA knockdown, Rap1 activation assay, MMP secretion assay, invasion assay","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — siRNA knockdown with multiple functional readouts, single lab","pmids":["25617801"],"is_preprint":false},{"year":2015,"finding":"C3G promotes survival and myogenic differentiation of C2C12 cells through mechanisms requiring both its catalytic and protein interaction domains, dependent on cellular R-Ras; C3G localizes to focal adhesions in myotubes; C3G expression increases Akt activity and suppresses cyclin D1 while inducing p27.","method":"C2C12 differentiation assay, shRNA knockdown, dominant-negative C3G, R-Ras dependence assay, immunofluorescence","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple domain mutants with functional assays, single lab","pmids":["26133694"],"is_preprint":false},{"year":2016,"finding":"C3G is required in multipolar neurons for the multi-to-bipolar transition during cortical development: conditional inactivation of Rapgef1 results in defects in neuronal migration, axon formation, and cortical lamination; C3G is required for specification of an axon and initiation of radial migration.","method":"Conditional KO (Cre-mediated at different time points), in utero electroporation, live cell imaging","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with temporal control and live imaging, functional rescue data","pmids":["27111087"],"is_preprint":false},{"year":2017,"finding":"C3G regulates platelet α-granule exocytosis with both GEF-dependent and independent mechanisms; transgenic C3G platelets showed decreased secretion of anti-angiogenic factors; C3G interacts with VAMP-7 (vesicle-associated membrane protein), potentially explaining α-granule retention.","method":"Proteomic analysis of platelet secretome, in vitro capillary tube formation assay, in vivo tumor models, immunofluorescence, co-immunoprecipitation with VAMP-7","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — co-IP identification of VAMP-7 interaction with functional secretome readout, single lab","pmids":["29340032"],"is_preprint":false},{"year":2017,"finding":"C3G undergoes regulated nucleocytoplasmic exchange: it contains functional NLS, NES, and requires GSK3-β-dependent phosphorylation for nuclear localization; nuclear C3G associates with chromatin and nuclear matrix, represses euchromatin-associated histone modifications, and is required for myogenic differentiation.","method":"Leptomycin B treatment, importin-α co-expression, GSK3β inhibition, CRISPR/Cas9 KO, chromatin fractionation, ChIP-like histone modification assay","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple localization methods plus KO functional assay, single lab","pmids":["28148649"],"is_preprint":false},{"year":2018,"finding":"C3G, through its GEF activity, induces megakaryocytic differentiation and proplatelet formation: transgenic C3G (but not C3GΔCat) bone marrow cells showed increased megakaryocyte differentiation markers; GATA-1 was identified as a positive regulator of C3G expression.","method":"Transgenic mouse models (platelet-specific C3G and C3GΔCat), flow cytometry for differentiation markers, bone marrow explant proplatelet assay","journal":"Cell communication and signaling","confidence":"Medium","confidence_rationale":"Tier 2 / Strong — GEF-domain comparison in vivo with GEF-dead control, single lab","pmids":["30567575"],"is_preprint":false},{"year":2020,"finding":"C3G autoinhibition is mediated by two intramolecular interactions: (1) an autoinhibitory region (AIR) in the central domain binds to and blocks the catalytic Cdc25H domain; (2) the N-terminal domain binding to the REM domain is required for GEF activity. CrkL activates C3G by displacing the AIR/Cdc25HD interaction. Two lymphoma missense mutations in the AIR (Y554H, M555K) disrupt autoinhibition and cause constitutive Rap1 and LFA-1 activation.","method":"Biochemical mapping of intramolecular interactions, nucleotide exchange assay, mutagenesis, Ba/F3 cell functional assay for Rap1 and LFA-1 activation","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 1 / Strong — mechanistic dissection with in vitro biochemistry, mutagenesis, and cell biology; disease mutations validate model","pmids":["32873726"],"is_preprint":false},{"year":2020,"finding":"C3G is phosphorylated at Y504 in platelets by a PKC-Src-dependent mechanism; ERKs positively regulate this phosphorylation by inhibiting the tyrosine phosphatase Shp2; C3G participates in the ADP-P2Y12-PI3K-Rap1b and thrombin-TXA2 pathways and inhibits TXA2 synthesis through cPLA2 regulation.","method":"Platelet-specific C3G KO mouse, Rap1 activation assay, specific pathway inhibitors, phosphorylation assays","journal":"Signal transduction and targeted therapy","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO mouse model with multiple pharmacological pathway dissections and phospho-site validation","pmids":["32296045"],"is_preprint":false},{"year":2021,"finding":"C3G is essential for embryonic stem cell differentiation and lineage commitment: C3G-null ES cells show elevated STAT3 activity, very low ERK activity, high self-renewal factor expression (KLF4, ESRRB), and fail to differentiate upon LIF withdrawal; reintroduction of C3G partially reverts these changes. C3G KO cells also show reduced pFAK, pPaxillin, and integrin-β1, and downregulation of adhesion genes.","method":"CRISPR/Cas9 KO, STAT3 and ERK activity assay, gene expression analysis, C3G rescue, teratoma assay","journal":"Stem cell reviews and reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR KO with rescue and multiple pathway readouts, single lab","pmids":["33624208"],"is_preprint":false},{"year":2023,"finding":"Crk proteins activate C3G GEF activity via two segregated mechanisms: (1) recruitment to the plasma membrane via CrkL-SH3N binding to P1/P2 sites; (2) direct GEF stimulation via Crk binding to P3 (essential, occluded in resting C3G) and P4 sites. Tyrosine phosphorylation of C3G alone causes marginal activation but primes C3G by lowering the Crk concentration required for full activation and increasing maximum activity. CrkL-SH2 domain interaction with phospho-C3G is additionally required for optimal activation.","method":"Isothermal titration calorimetry, sedimentation velocity, nucleotide-dissociation kinetic assay, affinity pull-down, plasma membrane translocation assay in Jurkat cells","journal":"Cell communication and signaling","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted biochemistry (ITC, GEF kinetics) plus cell biology with domain mutant mapping; mechanistic model validated in T cells","pmids":["36737758"],"is_preprint":false}],"current_model":"RAPGEF1/C3G is a ubiquitously expressed guanine nucleotide exchange factor (GEF) that specifically activates Rap1 (and also R-Ras and Rap2) by catalyzing GDP-to-GTP exchange; its GEF activity is autoinhibited by an intramolecular AIR-Cdc25H interaction and is activated by a two-factor mechanism requiring both tyrosine phosphorylation at Y504 (by Src-family kinases, Hck, or c-Abl) and direct binding of Crk/CrkL adaptor proteins to proline-rich motifs P3/P4, while Crk/CrkL-SH3N binding to P1/P2 recruits C3G to the plasma membrane; upstream inputs include integrins, multiple receptor tyrosine kinases (ALK, EGFR), Reelin-Dab1, Cbl-CrkL, and TCR/CTLA-4 signaling; downstream, C3G-Rap1 regulates cell adhesion, migration, filopodia, cortical neuron migration, platelet activation, megakaryopoiesis, ES cell differentiation, and embryonic development, while GEF-independent functions include suppression of ERK via PP2A recruitment and destabilization of β-catenin."},"narrative":{"mechanistic_narrative":"RAPGEF1 (C3G) is a guanine nucleotide exchange factor that couples adaptor-based signaling to Rap-family GTPase activation, governing cell adhesion, migration, and developmental morphogenesis [PMID:8524240, PMID:11432821]. It is a specific GEF for Rap1, markedly stimulating GDP-to-GTP exchange in vitro and elevating Rap1-GTP in cells, with weaker activity toward related Ras-family GTPases including R-Ras and Rap2 [PMID:8524240, PMID:11432821]; its activation of R-Ras specifically routes signaling to JNK via MLK family kinases [PMID:9430657, PMID:10777559]. C3G is recruited and activated through proline-rich motifs in its central region that bind the N-terminal SH3 domains of the Crk/CrkL adaptors, which deliver C3G to membranes downstream of integrins, receptor tyrosine kinases, and immune receptors [PMID:7512734, PMID:7806500, PMID:9268367]. Its catalytic Cdc25H domain is held in cis-autoinhibition by an intramolecular autoinhibitory region (AIR), and full GEF output requires a two-input mechanism: tyrosine phosphorylation at Y504 by Src-family kinases, Hck, or c-Abl relieves negative regulation, while direct Crk binding to segregated proline-rich sites both targets C3G to the plasma membrane and stimulates exchange activity; lymphoma AIR mutations that break autoinhibition cause constitutive Rap1 and LFA-1 activation [PMID:10318861, PMID:14551197, PMID:32873726, PMID:36737758]. Upstream activating inputs include integrin adhesion, ALK and EGF/insulin signaling, Reelin-Dab1 in cortical neurons, Cbl-CrkL in immune cells, and TCR/CTLA-4 signaling [PMID:9840945, PMID:10657627, PMID:15062102, PMID:18809728, PMID:20190816, PMID:24396067]. Through Rap1, C3G drives integrin-dependent adhesion and migration, cortical neuron multipolar-to-bipolar transition and migration, platelet activation and megakaryocyte differentiation, and is essential for early mouse embryogenesis and vascular maturation [PMID:11432821, PMID:12466202, PMID:18506028, PMID:22659131, PMID:27111087, PMID:30567575]. C3G additionally exerts GEF-independent functions, including suppression of oncogene-induced ERK activation via PP2A recruitment and destabilization of β-catenin to limit TCF transcription [PMID:15077165, PMID:17825818, PMID:23486661].","teleology":[{"year":1994,"claim":"Established C3G's molecular identity by showing it binds Crk/Grb2 SH3 domains through a proline-rich region and carries a Ras-GNRP-homologous C-terminus, defining it as an adaptor-coupled exchange-factor candidate.","evidence":"Bacterial fusion pull-down, mutational mapping, and yeast CDC25 complementation","pmids":["7512734","7806500"],"confidence":"High","gaps":["GEF substrate not yet defined","specificity of Crk SH3 binding over other adaptors not fully resolved in cells"]},{"year":1995,"claim":"Defined the catalytic substrate, showing C3G is a specific GEF for Rap1 in vitro and in cells with only marginal activity on Ras and Ral.","evidence":"In vitro GDP-dissociation/GTP-γS binding assays and in vivo GTP-loading in COS7 cells","pmids":["8524240"],"confidence":"High","gaps":["mechanism linking adaptor binding to catalysis unknown","physiological upstream activators not identified"]},{"year":1997,"claim":"Resolved how adaptors activate C3G, demonstrating Crk/CrkL/Grb2 act mainly by membrane recruitment rather than allosteric stimulation in vivo.","evidence":"In vivo Rap1 GTP-loading versus in vitro GEF assays with membrane-targeting and dominant-negative constructs in COS1 cells","pmids":["9268367"],"confidence":"High","gaps":["did not reconcile later evidence for direct Crk stimulation of catalysis","phospho-regulation of activity not addressed"]},{"year":1999,"claim":"Identified the activating phospho-switch, showing Y504 phosphorylation relieves an internal negative regulatory domain to activate GEF output.","evidence":"Systematic tyrosine mutagenesis (aa 391-579) with CrkI co-expression and Rap1-GTP loading","pmids":["10318861"],"confidence":"High","gaps":["structural basis of the negative regulatory domain not defined","kinase responsible in physiological settings not pinned down"]},{"year":2001,"claim":"Established the in vivo requirement for C3G, showing it is essential for cell adhesion and early embryogenesis and that its role is interchangeable with other Rap1-activating GEFs.","evidence":"Knockout/conditional mouse, adhesion/migration assays, rescue by active Rap1, Rap2, R-Ras and other GEFs","pmids":["11432821"],"confidence":"High","gaps":["tissue-specific downstream effectors not dissected","GEF-independent contributions to phenotype not separated"]},{"year":2003,"claim":"Connected C3G to specific adhesion structures and vascular development, showing it is needed for integrin-β1/paxillin focal adhesion formation in vivo.","evidence":"Hypomorphic knock-in mouse, focal adhesion immunofluorescence, PDGF response assays","pmids":["12466202"],"confidence":"High","gaps":["selectivity for β1- over β3-adhesions mechanistically unexplained"]},{"year":2004,"claim":"Defined GEF-independent functions, showing C3G's N-terminal Crk-binding domain suppresses ERK via PP2A recruitment, expanding its role beyond Rap1 activation.","evidence":"Focus/soft-agar assays, co-IP with PP2A and PP2A activity assays, okadaic acid","pmids":["15077165","17825818"],"confidence":"Medium","gaps":["direct PP2A binding interface not mapped","single lab; reciprocal validation limited"]},{"year":2004,"claim":"Placed C3G in the Reelin-Dab1 neuronal pathway, showing Reelin activates a Dab1→Crk→C3G→Rap1 cascade in cortical neurons.","evidence":"Phospho-Dab1 affinity pull-down, co-IP, Rap1-GTP assay in primary cortical neurons","pmids":["15062102"],"confidence":"High","gaps":["downstream Rap1 effectors in migration not identified at this stage"]},{"year":2008,"claim":"Demonstrated the developmental neuronal requirement, showing C3G is needed for preplate splitting, the multipolar-to-bipolar transition, and cortical neuron migration via Reelin-driven Rap1 activation.","evidence":"Conditional KO mice, Rap1-GTP after reelin, in utero imaging","pmids":["18506028","27111087"],"confidence":"High","gaps":["effector linking Rap1 to cytoskeletal remodeling in migrating neurons not fully defined"]},{"year":2012,"claim":"Established a GEF-dependent role in hemostasis, showing C3G overexpression enhances and GEF-dead C3G impairs platelet activation downstream of PKC-Rap1.","evidence":"Platelet-specific transgenic mice (C3G and C3GΔCat), bleeding time, aggregation, Rap1 assays","pmids":["22659131"],"confidence":"High","gaps":["upstream kinase coupling PKC to C3G not yet defined here"]},{"year":2012,"claim":"Extended GEF-independent regulation to Wnt signaling, showing C3G binds and destabilizes β-catenin to repress TCF transcription independent of GEF activity and GSK3β.","evidence":"Reciprocal co-IP, domain mapping, TCF reporter, proteasome inhibitor","pmids":["23486661"],"confidence":"Medium","gaps":["mechanism of β-catenin destabilization unresolved","single-lab finding"]},{"year":2020,"claim":"Resolved the autoinhibition mechanism, showing an intramolecular AIR blocks the catalytic domain and CrkL activates by displacing it, with lymphoma AIR mutations causing constitutive activation.","evidence":"Intramolecular interaction mapping, nucleotide exchange assays, mutagenesis, Ba/F3 Rap1/LFA-1 readouts","pmids":["32873726"],"confidence":"High","gaps":["high-resolution structure of the autoinhibited state not reported","interplay of AIR release with Y504 phosphorylation not fully quantified here"]},{"year":2020,"claim":"Defined platelet-specific phospho-regulation, showing PKC-Src drives Y504 phosphorylation, ERK supports it by inhibiting Shp2, and C3G feeds the P2Y12-PI3K-Rap1b and thrombin-TXA2 pathways.","evidence":"Platelet-specific KO mouse, pathway inhibitors, phospho-site assays","pmids":["32296045"],"confidence":"High","gaps":["direct Shp2-C3G relationship not biochemically reconstituted"]},{"year":2023,"claim":"Integrated phosphorylation and adaptor inputs into a two-factor activation model, showing Crk binding to segregated proline sites both recruits and directly stimulates C3G while Y504 phosphorylation primes the enzyme.","evidence":"ITC, sedimentation velocity, GEF kinetics, pull-downs, and membrane translocation in Jurkat cells","pmids":["36737758"],"confidence":"High","gaps":["full-length structural model of the activated complex not determined","in vivo verification across cell types incomplete"]},{"year":null,"claim":"How C3G's GEF-dependent Rap1 outputs are integrated with its GEF-independent nuclear, PP2A, and β-catenin functions to produce cell-type-specific outcomes remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["no unified structural model of activated, membrane-bound C3G","spatial coordination of Golgi/cytoskeletal/nuclear pools not defined","physiological selection between Rap1 versus R-Ras outputs unclear"]}],"mechanism_profile":{"molecular_activity":[],"localization":[{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[22,31]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[22,32]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[5,40,51]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[46]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,5,12,51]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[19,21,29,44]},{"term_id":"R-HSA-109582","term_label":"Hemostasis","supporting_discovery_ids":[37,49]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[18,30,40]},{"term_id":"R-HSA-1474244","term_label":"Extracellular matrix organization","supporting_discovery_ids":[11,13,21]}],"complexes":[],"partners":["CRK","CRKL","RAP1A","HCK","ABL1","BCAR1","CBL","PPP2CA"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q13905","full_name":"Rap guanine nucleotide exchange factor 1","aliases":["CRK SH3-binding GNRP","Guanine nucleotide-releasing factor 2","Protein C3G"],"length_aa":1077,"mass_kda":120.5,"function":"Guanine nucleotide-releasing protein that binds to SH3 domain of CRK and GRB2/ASH. Transduces signals from CRK to activate RAS. Involved in cell branching and adhesion mediated by BCAR1-CRK-RAPGEF1 signaling and activation of RAP1 (PubMed:12432078). Plays a role in the establishment of basal endothelial barrier function. Plays a role in nerve growth factor (NGF)-induced sustained activation of Rap1 and neurite outgrowth","subcellular_location":"Early endosome","url":"https://www.uniprot.org/uniprotkb/Q13905/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RAPGEF1","classification":"Not Classified","n_dependent_lines":47,"n_total_lines":1208,"dependency_fraction":0.03890728476821192},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/RAPGEF1","total_profiled":1310},"omim":[{"mim_id":"615759","title":"KINASE D-INTERACTING SUBSTRATE, 220-KD; KIDINS220","url":"https://www.omim.org/entry/615759"},{"mim_id":"607901","title":"FERM DOMAIN-CONTAINING KINDLIN 3; FERMT3","url":"https://www.omim.org/entry/607901"},{"mim_id":"601790","title":"PANCREATIC POLYPEPTIDE RECEPTOR 1; PPYR1","url":"https://www.omim.org/entry/601790"},{"mim_id":"600303","title":"RAP GUANINE NUCLEOTIDE EXCHANGE FACTOR 1; RAPGEF1","url":"https://www.omim.org/entry/600303"},{"mim_id":"151440","title":"LYMPHOBLASTIC LEUKEMIA-DERIVED SEQUENCE 1; LYL1","url":"https://www.omim.org/entry/151440"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Vesicles","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/RAPGEF1"},"hgnc":{"alias_symbol":["C3G"],"prev_symbol":["GRF2"]},"alphafold":{"accession":"Q13905","domains":[{"cath_id":"1.20.120.330","chopping":"78-208","consensus_level":"high","plddt":85.6932,"start":78,"end":208},{"cath_id":"1.20.870.10","chopping":"669-820","consensus_level":"medium","plddt":89.9751,"start":669,"end":820},{"cath_id":"1.10.840.10","chopping":"843-1076","consensus_level":"medium","plddt":91.2519,"start":843,"end":1076}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q13905","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q13905-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q13905-F1-predicted_aligned_error_v6.png","plddt_mean":64.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RAPGEF1","jax_strain_url":"https://www.jax.org/strain/search?query=RAPGEF1"},"sequence":{"accession":"Q13905","fasta_url":"https://rest.uniprot.org/uniprotkb/Q13905.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q13905/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q13905"}},"corpus_meta":[{"pmid":"7512734","id":"PMC_7512734","title":"C3G, a guanine nucleotide-releasing protein expressed ubiquitously, binds to the Src homology 3 domains of CRK and GRB2/ASH proteins.","date":"1994","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/7512734","citation_count":371,"is_preprint":false},{"pmid":"8524240","id":"PMC_8524240","title":"Identification of Rap1 as a target for the Crk SH3 domain-binding guanine nucleotide-releasing factor C3G.","date":"1995","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/8524240","citation_count":330,"is_preprint":false},{"pmid":"11731477","id":"PMC_11731477","title":"c(3)G encodes a Drosophila synaptonemal complex protein.","date":"2001","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/11731477","citation_count":261,"is_preprint":false},{"pmid":"6177820","id":"PMC_6177820","title":"Breakdown of C3 after complement activation. 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The C-terminal region of C3G shows homology to GNRPs for Ras and complemented loss of CDC25 function in yeast.\",\n      \"method\": \"Bacterial fusion protein pull-down, mutational analysis, yeast complementation assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — direct binding assays, mutational mapping, and functional complementation in yeast; replicated by multiple subsequent studies\",\n      \"pmids\": [\"7512734\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Four proline-rich sequences in the center region of C3G each individually bind to the N-terminal SH3 domain of c-Crk and v-Crk with high specificity and preferentially over other SH3 domains (including Grb2 SH3). Endogenous C3G co-precipitates with Crk from cell lysates.\",\n      \"method\": \"GST pull-down, in vitro binding assays, co-precipitation from cell lysates\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal pull-downs with mutational mapping, replicated across labs\",\n      \"pmids\": [\"7806500\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"C3G is a specific guanine nucleotide exchange factor (GEF) for Rap1: it markedly stimulated GDP dissociation and GTP-γS binding to Rap1B in vitro, and induced accumulation of GTP-bound Rap1A in COS7 cells in vivo, while having only marginal effects on Ha-Ras, N-Ras, and RalA.\",\n      \"method\": \"In vitro GEF assay (GDP dissociation, GTP-γS binding), in vivo GTP-loading assay in COS7 cells\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution plus in vivo confirmation, replicated extensively\",\n      \"pmids\": [\"8524240\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Following T cell receptor activation, Cbl becomes tyrosine phosphorylated and associates with CrkL via the Crk SH2 domain (inhibitable by pYDVP phosphopeptide); CrkL constitutively associates with C3G, and a fraction of C3G co-immunoprecipitates with Cbl in activated Jurkat T cells.\",\n      \"method\": \"Co-immunoprecipitation, phosphopeptide competition assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — co-IP in T cells with phosphopeptide competition, single lab\",\n      \"pmids\": [\"8626543\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"C3G selectively binds to the amino-terminal SH3 domain of Grb2 in vitro, but in primary B cells C3G associates constitutively with the CrkL adaptor rather than with Grb2, Shc, or CrkII, both before and after BCR stimulation.\",\n      \"method\": \"Yeast two-hybrid, GST fusion protein pull-down, co-immunoprecipitation from B cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — in vitro binding confirmed by in vivo co-IP; some discordance between in vitro and in vivo results\",\n      \"pmids\": [\"8621483\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Expression of Crk, CrkL, and Grb2 with C3G enhances C3G GEF activity toward Rap1 in vivo primarily by recruiting C3G to the cell membrane, not by allosteric activation; membrane targeting of Crk (farnesylation signal) compensated for the SH2 domain requirement, and Crk did not stimulate C3G GEF activity in vitro.\",\n      \"method\": \"In vivo Rap1 GTP-loading assay, in vitro GEF assay, dominant-negative and membrane-targeting constructs in COS1 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — combined in vitro and in vivo assays with domain mutants clarifying mechanism\",\n      \"pmids\": [\"9268367\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"v-Crk activates JNK via C3G: coexpression of C3G with v-Crk further enhanced JNK activity and transformation, while a dominant-negative C3G lacking the GEF domain abolished v-Crk-induced JNK activity and colony formation in NIH 3T3 cells.\",\n      \"method\": \"JNK kinase assay, dominant-negative C3G expression, colony formation assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional assays with dominant-negative constructs, single lab\",\n      \"pmids\": [\"9122199\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Insulin and EGF stimulation induces dissociation of the CrkII-C3G complex, correlating with a conformational change in Rap1; dissociation is driven by tyrosine phosphorylation of CrkII at Tyr221 (mutation Y221F prevents insulin-induced dissociation), and is reversed by PTP1B-mediated dephosphorylation.\",\n      \"method\": \"Co-immunoprecipitation, GST-C3G pull-down, mutagenesis, PTP1B dephosphorylation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro reconstitution of dissociation, phospho-site mutagenesis, single lab\",\n      \"pmids\": [\"9353263\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"p130Cas SH3 domain directly binds C3G via a proline-rich site (APPKPPLP) N-terminal to the Crk-binding motifs; mutational analysis defined Pro1, Lys3, and Pro4 as critical for high-affinity interaction (consensus CasSH3-binding motif: XXPXKPX).\",\n      \"method\": \"Yeast two-hybrid, in vitro pull-down, in vivo co-immunoprecipitation, deletion/point mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — direct binding confirmed in vitro and in vivo with extensive mutagenesis\",\n      \"pmids\": [\"9748234\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Transformation suppressor activity of C3G maps to its N-terminal Crk-binding (SH3-b) domain and is independent of the catalytic CDC25-H domain; a C3G mutant lacking the catalytic domain (C3GΔCat) suppressed Ras/Raf/Sis oncogene-induced focus formation as effectively as full-length C3G.\",\n      \"method\": \"Focus formation assay, NIH3T3 transfection with deletion mutants\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional assay with multiple deletion constructs, single lab\",\n      \"pmids\": [\"9482107\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"C3G activates JNK1 through a Ras-independent pathway involving MLK family kinases (MLK3 and DLK): dominant-negative MLK3 and DLK blocked C3G-induced JNK1 activation, while dominant-negative Ras, Rac, or Pak did not.\",\n      \"method\": \"JNK1 kinase assay, dominant-negative constructs, co-expression in 293T cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis by dominant-negative constructs, single lab\",\n      \"pmids\": [\"9430657\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Integrin-mediated cell adhesion to fibronectin induces tyrosine phosphorylation of C3G via CrkL in a cytoskeleton-dependent manner in normal 3T3 fibroblasts; this pathway is disrupted in Bcr/Abl-expressing cells, which show reduced CrkL-C3G complex formation.\",\n      \"method\": \"Co-immunoprecipitation, tyrosine phosphorylation assay, cytoskeletal disruption experiments\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — co-IP with cytoskeletal manipulation, single lab\",\n      \"pmids\": [\"9840945\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"C3G is activated by CrkI-mediated tyrosine phosphorylation at tyrosine 504: the C3G-Y504F mutant was markedly less phosphorylated and less activated by CrkI expression. Phosphorylation at Y504 relieves a cis-acting negative regulatory domain (aa 391–579) outside the catalytic region.\",\n      \"method\": \"Systematic mutagenesis of all 7 tyrosines in aa 391-579, CrkI co-expression, Rap1-GTP loading assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — systematic site-directed mutagenesis with in vivo GEF activity assay; replicated by multiple subsequent studies\",\n      \"pmids\": [\"10318861\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"The CrkL-C3G complex mediates integrin-dependent hematopoietic cell adhesion to fibronectin via VLA-4 and VLA-5; the GEF activity of C3G is required (GEF-dead mutant abrogates CrkL-induced adhesion), and the N-terminal SH3 domain of CrkL (C3G-binding domain) is critical.\",\n      \"method\": \"Overexpression of C3G and deletion mutants, integrin-blocking antibodies, flow cytometry\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional cell adhesion assay with domain mutants, single lab\",\n      \"pmids\": [\"10339478\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"The CrkL-C3G complex links Cbl to downstream signaling after integrin ligation; overexpression of C3G (identified as the major CrkL SH3 N-terminal binding protein) enhances spontaneous migration of Ba/F3 hematopoietic cells.\",\n      \"method\": \"Co-immunoprecipitation, GFP-fusion migration assay, domain deletion analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — co-IP and functional migration assay with domain mutants, single lab\",\n      \"pmids\": [\"10608804\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"CrkL mediates Ras-dependent activation of the Raf/ERK pathway through C3G in hematopoietic cells stimulated with erythropoietin or IL-3; C3G GEF domain is required (GEF-dead mutant is inhibitory), and dominant-negative Ras blocks CrkL/C3G-induced ERK2 and Elk-1 activation.\",\n      \"method\": \"ERK1/2 kinase assay, Elk-1 reporter assay, Ras activation assay, dominant-negative constructs\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis with dominant-negative Ras plus GEF-domain requirement, single lab\",\n      \"pmids\": [\"10514505\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"C3G activates JNK via R-Ras (not Rap1): constitutively active R-Ras activated JNK while Rap1(Val-12) did not; dominant-negative R-Ras blocked v-Crk-induced JNK activation and transformation; among Rap1-specific GEFs (CalDAG-GEFI, Epac), none activated JNK.\",\n      \"method\": \"JNK kinase assay, dominant-negative R-Ras, GEF specificity panel, NIH3T3 flat reversion assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis with dominant-negatives and GEF panel, single lab\",\n      \"pmids\": [\"10777559\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Formation of the CrkII-C3G complex is regulated by integrins and inversely correlates with ERK activation: suspended cells (low ERK) contain a CrkII-C3G complex with elevated Rap1-GTP, while adherent cells (high ERK) dissociate the complex; CrkII Y109L mutation disrupts the complex and activates ERK; PTP1B C215S also disrupts the complex.\",\n      \"method\": \"Co-immunoprecipitation, Rap1-GTP pull-down, overexpression in CHO cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — correlative co-IP with gain-of-function constructs, single lab\",\n      \"pmids\": [\"10777617\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"IFN-γ activates a signaling cascade in which c-Cbl is tyrosine phosphorylated, recruits CrkL via its SH2 domain, and CrkL then promotes activation of C3G (constitutively bound to CrkL via N-terminal SH3) leading to Rap1 activation.\",\n      \"method\": \"Co-immunoprecipitation, Rap1 activation assay, tyrosine phosphorylation assay\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — co-IP and Rap1 activation in NB-4 cells, single lab\",\n      \"pmids\": [\"10657627\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"C3G-dependent activation of Rap1 is required for cell adhesion and early mouse embryogenesis: C3G knockout mice die before E7.5; C3G-deficient fibroblasts show impaired cell adhesion, delayed spreading, and accelerated migration, which are rescued by active Rap1, Rap2, R-Ras, or other Rap1 GEFs (Epac, CalDAG-GEFI).\",\n      \"method\": \"Knockout mouse model, Cre-lox conditional deletion, Rap1 GTP-loading assay, cell adhesion and migration assays\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic rescue experiments with multiple GEFs plus KO phenotype; functional equivalence of Rap1 activation confirmed\",\n      \"pmids\": [\"11432821\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Hck tyrosine kinase directly interacts with C3G via its SH3 domain binding to the proline-rich region of C3G; co-expression of Hck and C3G induces caspase-1, -8, and -9-mediated apoptosis requiring Hck catalytic activity but not C3G GEF domain or Y504 phosphorylation. Hck phosphorylates C3G at Y504 in cells.\",\n      \"method\": \"Co-immunoprecipitation, SH3 domain-based interaction cloning, apoptosis assay, dominant-negative caspase constructs, phosphorylation assay with kinase-dead Hck\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct interaction and functional assays with multiple controls, single lab\",\n      \"pmids\": [\"14551197\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"C3G is required for vascular maturation and focal adhesion formation in mouse development: hypomorphic C3G embryos die ~E11.5 with vascular defects; C3G-deficient fibroblasts lack paxillin/integrin-β1-positive focal adhesions (but not integrin-β3-positive ones) and show abnormal PDGF-BB responses.\",\n      \"method\": \"Hypomorphic knock-in mouse model, immunofluorescence for focal adhesion markers, PDGF response assays\",\n      \"journal\": \"Development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetic model with specific cellular mechanistic readout\",\n      \"pmids\": [\"12466202\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Tyrosine-phosphorylated C3G (pY504) localizes predominantly to the Golgi complex and subcortical actin cytoskeleton when phosphorylated by Hck or Src; cytoskeletal disruption by cytochalasin D abolishes peripheral pY504-C3G staining without affecting Golgi localization, suggesting spatially restricted activation.\",\n      \"method\": \"Immunofluorescence with phospho-specific antibody (pY504), cytochalasin D treatment, subcellular fractionation\",\n      \"journal\": \"BMC cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — direct localization with phospho-specific antibody and pharmacological perturbation, single lab\",\n      \"pmids\": [\"15320955\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Reelin stimulation of cortical neurons activates a Dab1→CrkL/CrkI/CrkII→C3G→Rap1 signaling pathway: Reelin induces Crk family binding to phospho-Dab1 at Y220 and Y232, induces tyrosine phosphorylation of C3G, and activates Rap1.\",\n      \"method\": \"Phospho-affinity pull-down from embryonic brain extract, co-immunoprecipitation, Rap1-GTP assay, cortical neuron culture\",\n      \"journal\": \"Current biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — biochemical pathway reconstitution in primary neurons plus identification of critical phospho-residues\",\n      \"pmids\": [\"15062102\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"In nectin-based cell-cell adhesion, Rap1 is activated via a c-Src-Crk-C3G signaling cascade at cell-cell contact sites; Rap1 activation (together with c-Src) is required for FRG-mediated Cdc42 activation and formation of adherens junctions. Inhibiting Crk, C3G, or Rap1 reduced AJ formation.\",\n      \"method\": \"Co-immunoprecipitation, dominant-negative constructs, Rap1 activation assay, immunofluorescence of AJ markers\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis with dominant-negatives and co-IP, single lab\",\n      \"pmids\": [\"15504743\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"C3G suppresses oncogene-induced ERK activation and cyclin A expression via its N-terminal Crk-binding domain independent of GEF activity; C3G and C3GΔCat interact with PP2A phosphatases (confirmed by co-immunoprecipitation) and increase ERK-associated PP2A activity at the subcortical actin cytoskeleton.\",\n      \"method\": \"ERK phosphorylation assay, focus formation assay, soft agar assay, co-immunoprecipitation with PP2A, PP2A phosphatase activity assay, okadaic acid treatment\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (co-IP + phosphatase assay + pharmacological inhibition), single lab\",\n      \"pmids\": [\"15077165\", \"17825818\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"C3G controls the size of the cerebral cortical neural precursor population by inhibiting the Ras/Akt pathway: C3G-deficient neuroepithelial cells show overproliferation, nuclear β-catenin accumulation, Akt/PKB activation, GSK3β inhibition, and fail to exit the cell cycle in response to growth factors.\",\n      \"method\": \"Conditional knockout mouse, Rap1 GTP-loading assay, Akt and GSK3β phosphorylation assays, β-catenin localization\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo KO with defined molecular pathway and in vitro mechanistic follow-up\",\n      \"pmids\": [\"16858399\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"A novel truncated C3G isoform, p87C3G, is overexpressed in CML cells and co-immunoprecipitates with Bcr-Abl; the interaction involves the SH3-binding domain (first polyproline region) of p87C3G and the SH3 domain of Abl, and Bcr-Abl phosphorylates p87C3G in vitro.\",\n      \"method\": \"Co-immunoprecipitation, in vitro pull-down, in vitro kinase assay, domain mutagenesis\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP with in vitro kinase assay, single lab\",\n      \"pmids\": [\"16443220\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"C3G is required for c-Abl-induced filopodia formation during cell spreading on fibronectin; C3G promotes filopodia in a manner requiring Abl catalytic activity and N-WASP function but independent of Rho/Rac/Cdc42 dominant-negative inhibition. Cellular C3G interacts with c-Abl and enhances c-Abl cytoplasmic localization.\",\n      \"method\": \"RNAi knockdown, overexpression, dominant-negative GTPases, wiskostatin pharmacological inhibition, co-immunoprecipitation, immunofluorescence\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi plus pharmacological epistasis, single lab\",\n      \"pmids\": [\"17475248\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"C3G is essential for cortical neuron migration and preplate splitting during brain development; C3G is activated by reelin in cortical neurons leading to Rap1 activation; C3G-deficient neurons arrest in a multipolar state and fail to migrate, with disrupted basement membrane and radial glial processes.\",\n      \"method\": \"Conditional KO mouse, Rap1 GTP-loading assay after reelin stimulation, in utero live imaging, immunofluorescence\",\n      \"journal\": \"Development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetic model with defined reelin-C3G-Rap1 pathway and multiple cellular readouts\",\n      \"pmids\": [\"18506028\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"WAVE2 complex regulates TCR-stimulated Rap1 activation via recruitment and activation of the CrkL-C3G exchange complex; Abl tyrosine kinase (associated with WAVE2) phosphorylates C3G on tyrosine, which is required for C3G GEF activity toward Rap1, leading to integrin clustering and affinity maturation.\",\n      \"method\": \"Co-immunoprecipitation, membrane recruitment assay, Rap1 activation assay, Abl kinase inhibitor, siRNA knockdown\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP with functional assays and pharmacological/genetic perturbations, single lab\",\n      \"pmids\": [\"18809728\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"C3G promotes neurite growth in human neuroblastoma cells dependent on both its catalytic domain and N-terminal regulatory domain, requiring Cdc42 and Rap1 function; C3G knockdown inhibits forskolin- and NGF-induced differentiation; C3G is phosphorylated at Y504 predominantly in the Golgi upon forskolin/NGF treatment; C3G expression induces the cell cycle inhibitor p21.\",\n      \"method\": \"Overexpression and shRNA knockdown, dominant-negative GTPases, phospho-Y504 immunofluorescence, differentiation assays in IMR-32 cells\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi and overexpression with multiple functional readouts, single lab\",\n      \"pmids\": [\"18957052\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"c-Abl phosphorylates C3G at Y504 in response to oxidative stress; this phosphorylation is dependent on the F-actin-binding domain (FABD) of c-Abl and is restricted to F-actin-rich regions; C3G knockdown or dominant-negative C3G inhibits c-Abl-mediated apoptosis.\",\n      \"method\": \"In vivo phosphorylation assay, FABD deletion mutant, RNAi, dominant-negative C3G, cytoskeletal fractionation\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain mutant analysis with functional apoptosis readout, single lab\",\n      \"pmids\": [\"20581864\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Drosophila C3G is a Rap1-specific GEF (stimulates nucleotide exchange on Drosophila Rap GTPases in vitro) required for body wall muscle integrity and proper βPS integrin localization at muscle attachment sites during larval stages.\",\n      \"method\": \"In vitro GEF assay with Drosophila Rap GTPases, genetic deletion of C3G locus, in situ hybridization, immunofluorescence\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro GEF reconstitution plus in vivo genetic model with defined phenotype\",\n      \"pmids\": [\"20209136\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"ALK receptor tyrosine kinase activates Rap1 via C3G: activated ALK recruits a constitutive CrkL-C3G complex; siRNA knockdown of C3G or Rap1 inhibits ALK-induced neurite outgrowth and neuroblastoma cell proliferation.\",\n      \"method\": \"Co-immunoprecipitation, Rap1 activation assay, siRNA knockdown, Rap1GAP overexpression\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP with functional siRNA knockdown assays, single lab\",\n      \"pmids\": [\"20190816\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Lyn tyrosine kinase controls spatial activation of Rap1 at the neutrophil leading edge by recruiting the CrkL-C3G complex; depletion of Lyn prevents chemoattractant-induced Rap1 activation at the leading edge, rescued by ectopic Rap1 expression.\",\n      \"method\": \"RNAi depletion of Lyn, Rap1 activation assay, live imaging of leading edge localization, epistasis with Rap1 rescue\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi epistasis with rescue, functional localization data, single lab\",\n      \"pmids\": [\"21628423\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"TC-PTP (TC48 isoform) dephosphorylates C3G at Y504: TC48 interacts with C3G via its C-terminal non-catalytic residues and the Crk-binding region of C3G; a substrate-trap mutant of TC48 preferentially binds phospho-C3G at the Golgi; TC48 expression abrogates Src- and pervanadate-induced C3G phosphorylation and inhibits neurite outgrowth.\",\n      \"method\": \"Co-immunoprecipitation, substrate-trap mutant, in vitro dephosphorylation, IGF-induced dephosphorylation, neurite outgrowth assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — substrate-trap approach with functional validation, single lab\",\n      \"pmids\": [\"21876762\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"C3G plays a role in platelet clotting through its GEF activity: transgenic mice overexpressing C3G in platelets showed shorter bleeding times and stronger platelet activation, while tgC3GΔCat (GEF-dead) mice showed a bleeding diathesis; C3G is a mediator in the PKC pathway leading to Rap1 activation in platelets.\",\n      \"method\": \"Transgenic mouse model (platelet-specific), bleeding time assay, platelet aggregation assay, Rap1 activation assay\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo transgenic model with GEF-dead control and multiple functional readouts\",\n      \"pmids\": [\"22659131\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"C3G forms a complex with Bcr-Abl and p38α MAPK at focal adhesions in CML cells; interactions involve SH3/SH3-b domains with CrkL, p130Cas, Cbl, and Abi1; C3G, Abi1, or Cbl knockdown impairs adhesion to fibronectin; C3G and p38α act through a common pathway to regulate K562 cell adhesion.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence, siRNA knockdown, cell adhesion assay\",\n      \"journal\": \"Cell communication and signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — co-IP confirmed by immunofluorescence with RNAi knockdown, single lab\",\n      \"pmids\": [\"23343344\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"C3G functions as a negative regulator of β-catenin: C3G is present in a complex with β-catenin (via its proline-rich Crk-binding region interacting with β-catenin residues 90-525); C3G overexpression destabilizes β-catenin and reduces its nuclear accumulation and TCF transcription activity independent of GEF activity and GSK3β; β-catenin reciprocally represses C3G expression.\",\n      \"method\": \"Co-immunoprecipitation, deletion mutant mapping, TCF reporter assay, Western blot for β-catenin stability, proteasome inhibitor treatment\",\n      \"journal\": \"Genes & cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP with domain mapping and functional reporter assay, single lab\",\n      \"pmids\": [\"23486661\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"CTLA-4 receptor signaling mediates tyrosine phosphorylation of C3G (facilitated by Hck), which is required for augmented Rap1 activation and LFA-1-mediated T-cell adhesion; C3G translocates to the plasma membrane downstream of TCR signaling in a Zap70-dependent manner.\",\n      \"method\": \"Co-immunoprecipitation, Rap1 activation assay, C3G membrane translocation assay, siRNA knockdown, Zap70 inhibitor\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional signaling pathway assays with pharmacological/genetic perturbations, single lab\",\n      \"pmids\": [\"24396067\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Immunophilin cyclophilin A increases C3G binding to CrkII, while immunophilin inhibitors (CsA, FK506) inhibit CrkII-C3G association by promoting cis-conformation of CrkII (detected by FRET); suppression of CrkII-C3G complex by immunophilin inhibitors impairs T cell adhesion to fibronectin and migration toward SDF-1α.\",\n      \"method\": \"Co-immunoprecipitation, FRET-based PICCHU assay, T cell adhesion and migration assay\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — FRET conformational assay with functional cell assays, single lab\",\n      \"pmids\": [\"25225668\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"C3G-mediated Rap1 activation promotes secretion of MMP-2 and MMP-9 in ovarian cancer cells; C3G knockdown suppresses Rap1 activity and reduces MMP-2 and MMP-9 secretion as well as cell invasion.\",\n      \"method\": \"siRNA knockdown, Rap1 activation assay, MMP secretion assay, invasion assay\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — siRNA knockdown with multiple functional readouts, single lab\",\n      \"pmids\": [\"25617801\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"C3G promotes survival and myogenic differentiation of C2C12 cells through mechanisms requiring both its catalytic and protein interaction domains, dependent on cellular R-Ras; C3G localizes to focal adhesions in myotubes; C3G expression increases Akt activity and suppresses cyclin D1 while inducing p27.\",\n      \"method\": \"C2C12 differentiation assay, shRNA knockdown, dominant-negative C3G, R-Ras dependence assay, immunofluorescence\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple domain mutants with functional assays, single lab\",\n      \"pmids\": [\"26133694\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"C3G is required in multipolar neurons for the multi-to-bipolar transition during cortical development: conditional inactivation of Rapgef1 results in defects in neuronal migration, axon formation, and cortical lamination; C3G is required for specification of an axon and initiation of radial migration.\",\n      \"method\": \"Conditional KO (Cre-mediated at different time points), in utero electroporation, live cell imaging\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with temporal control and live imaging, functional rescue data\",\n      \"pmids\": [\"27111087\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"C3G regulates platelet α-granule exocytosis with both GEF-dependent and independent mechanisms; transgenic C3G platelets showed decreased secretion of anti-angiogenic factors; C3G interacts with VAMP-7 (vesicle-associated membrane protein), potentially explaining α-granule retention.\",\n      \"method\": \"Proteomic analysis of platelet secretome, in vitro capillary tube formation assay, in vivo tumor models, immunofluorescence, co-immunoprecipitation with VAMP-7\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — co-IP identification of VAMP-7 interaction with functional secretome readout, single lab\",\n      \"pmids\": [\"29340032\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"C3G undergoes regulated nucleocytoplasmic exchange: it contains functional NLS, NES, and requires GSK3-β-dependent phosphorylation for nuclear localization; nuclear C3G associates with chromatin and nuclear matrix, represses euchromatin-associated histone modifications, and is required for myogenic differentiation.\",\n      \"method\": \"Leptomycin B treatment, importin-α co-expression, GSK3β inhibition, CRISPR/Cas9 KO, chromatin fractionation, ChIP-like histone modification assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple localization methods plus KO functional assay, single lab\",\n      \"pmids\": [\"28148649\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"C3G, through its GEF activity, induces megakaryocytic differentiation and proplatelet formation: transgenic C3G (but not C3GΔCat) bone marrow cells showed increased megakaryocyte differentiation markers; GATA-1 was identified as a positive regulator of C3G expression.\",\n      \"method\": \"Transgenic mouse models (platelet-specific C3G and C3GΔCat), flow cytometry for differentiation markers, bone marrow explant proplatelet assay\",\n      \"journal\": \"Cell communication and signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Strong — GEF-domain comparison in vivo with GEF-dead control, single lab\",\n      \"pmids\": [\"30567575\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"C3G autoinhibition is mediated by two intramolecular interactions: (1) an autoinhibitory region (AIR) in the central domain binds to and blocks the catalytic Cdc25H domain; (2) the N-terminal domain binding to the REM domain is required for GEF activity. CrkL activates C3G by displacing the AIR/Cdc25HD interaction. Two lymphoma missense mutations in the AIR (Y554H, M555K) disrupt autoinhibition and cause constitutive Rap1 and LFA-1 activation.\",\n      \"method\": \"Biochemical mapping of intramolecular interactions, nucleotide exchange assay, mutagenesis, Ba/F3 cell functional assay for Rap1 and LFA-1 activation\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mechanistic dissection with in vitro biochemistry, mutagenesis, and cell biology; disease mutations validate model\",\n      \"pmids\": [\"32873726\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"C3G is phosphorylated at Y504 in platelets by a PKC-Src-dependent mechanism; ERKs positively regulate this phosphorylation by inhibiting the tyrosine phosphatase Shp2; C3G participates in the ADP-P2Y12-PI3K-Rap1b and thrombin-TXA2 pathways and inhibits TXA2 synthesis through cPLA2 regulation.\",\n      \"method\": \"Platelet-specific C3G KO mouse, Rap1 activation assay, specific pathway inhibitors, phosphorylation assays\",\n      \"journal\": \"Signal transduction and targeted therapy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KO mouse model with multiple pharmacological pathway dissections and phospho-site validation\",\n      \"pmids\": [\"32296045\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"C3G is essential for embryonic stem cell differentiation and lineage commitment: C3G-null ES cells show elevated STAT3 activity, very low ERK activity, high self-renewal factor expression (KLF4, ESRRB), and fail to differentiate upon LIF withdrawal; reintroduction of C3G partially reverts these changes. C3G KO cells also show reduced pFAK, pPaxillin, and integrin-β1, and downregulation of adhesion genes.\",\n      \"method\": \"CRISPR/Cas9 KO, STAT3 and ERK activity assay, gene expression analysis, C3G rescue, teratoma assay\",\n      \"journal\": \"Stem cell reviews and reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR KO with rescue and multiple pathway readouts, single lab\",\n      \"pmids\": [\"33624208\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Crk proteins activate C3G GEF activity via two segregated mechanisms: (1) recruitment to the plasma membrane via CrkL-SH3N binding to P1/P2 sites; (2) direct GEF stimulation via Crk binding to P3 (essential, occluded in resting C3G) and P4 sites. Tyrosine phosphorylation of C3G alone causes marginal activation but primes C3G by lowering the Crk concentration required for full activation and increasing maximum activity. CrkL-SH2 domain interaction with phospho-C3G is additionally required for optimal activation.\",\n      \"method\": \"Isothermal titration calorimetry, sedimentation velocity, nucleotide-dissociation kinetic assay, affinity pull-down, plasma membrane translocation assay in Jurkat cells\",\n      \"journal\": \"Cell communication and signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted biochemistry (ITC, GEF kinetics) plus cell biology with domain mutant mapping; mechanistic model validated in T cells\",\n      \"pmids\": [\"36737758\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RAPGEF1/C3G is a ubiquitously expressed guanine nucleotide exchange factor (GEF) that specifically activates Rap1 (and also R-Ras and Rap2) by catalyzing GDP-to-GTP exchange; its GEF activity is autoinhibited by an intramolecular AIR-Cdc25H interaction and is activated by a two-factor mechanism requiring both tyrosine phosphorylation at Y504 (by Src-family kinases, Hck, or c-Abl) and direct binding of Crk/CrkL adaptor proteins to proline-rich motifs P3/P4, while Crk/CrkL-SH3N binding to P1/P2 recruits C3G to the plasma membrane; upstream inputs include integrins, multiple receptor tyrosine kinases (ALK, EGFR), Reelin-Dab1, Cbl-CrkL, and TCR/CTLA-4 signaling; downstream, C3G-Rap1 regulates cell adhesion, migration, filopodia, cortical neuron migration, platelet activation, megakaryopoiesis, ES cell differentiation, and embryonic development, while GEF-independent functions include suppression of ERK via PP2A recruitment and destabilization of β-catenin.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RAPGEF1 (C3G) is a guanine nucleotide exchange factor that couples adaptor-based signaling to Rap-family GTPase activation, governing cell adhesion, migration, and developmental morphogenesis [#2, #19]. It is a specific GEF for Rap1, markedly stimulating GDP-to-GTP exchange in vitro and elevating Rap1-GTP in cells, with weaker activity toward related Ras-family GTPases including R-Ras and Rap2 [#2, #19]; its activation of R-Ras specifically routes signaling to JNK via MLK family kinases [#10, #16]. C3G is recruited and activated through proline-rich motifs in its central region that bind the N-terminal SH3 domains of the Crk/CrkL adaptors, which deliver C3G to membranes downstream of integrins, receptor tyrosine kinases, and immune receptors [#0, #1, #5]. Its catalytic Cdc25H domain is held in cis-autoinhibition by an intramolecular autoinhibitory region (AIR), and full GEF output requires a two-input mechanism: tyrosine phosphorylation at Y504 by Src-family kinases, Hck, or c-Abl relieves negative regulation, while direct Crk binding to segregated proline-rich sites both targets C3G to the plasma membrane and stimulates exchange activity; lymphoma AIR mutations that break autoinhibition cause constitutive Rap1 and LFA-1 activation [#12, #20, #48, #51]. Upstream activating inputs include integrin adhesion, ALK and EGF/insulin signaling, Reelin-Dab1 in cortical neurons, Cbl-CrkL in immune cells, and TCR/CTLA-4 signaling [#11, #18, #23, #30, #34, #40]. Through Rap1, C3G drives integrin-dependent adhesion and migration, cortical neuron multipolar-to-bipolar transition and migration, platelet activation and megakaryocyte differentiation, and is essential for early mouse embryogenesis and vascular maturation [#19, #21, #29, #37, #44, #47]. C3G additionally exerts GEF-independent functions, including suppression of oncogene-induced ERK activation via PP2A recruitment and destabilization of \\u03b2-catenin to limit TCF transcription [#25, #39].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"Established C3G's molecular identity by showing it binds Crk/Grb2 SH3 domains through a proline-rich region and carries a Ras-GNRP-homologous C-terminus, defining it as an adaptor-coupled exchange-factor candidate.\",\n      \"evidence\": \"Bacterial fusion pull-down, mutational mapping, and yeast CDC25 complementation\",\n      \"pmids\": [\"7512734\", \"7806500\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"GEF substrate not yet defined\", \"specificity of Crk SH3 binding over other adaptors not fully resolved in cells\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Defined the catalytic substrate, showing C3G is a specific GEF for Rap1 in vitro and in cells with only marginal activity on Ras and Ral.\",\n      \"evidence\": \"In vitro GDP-dissociation/GTP-\\u03b3S binding assays and in vivo GTP-loading in COS7 cells\",\n      \"pmids\": [\"8524240\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"mechanism linking adaptor binding to catalysis unknown\", \"physiological upstream activators not identified\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Resolved how adaptors activate C3G, demonstrating Crk/CrkL/Grb2 act mainly by membrane recruitment rather than allosteric stimulation in vivo.\",\n      \"evidence\": \"In vivo Rap1 GTP-loading versus in vitro GEF assays with membrane-targeting and dominant-negative constructs in COS1 cells\",\n      \"pmids\": [\"9268367\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"did not reconcile later evidence for direct Crk stimulation of catalysis\", \"phospho-regulation of activity not addressed\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Identified the activating phospho-switch, showing Y504 phosphorylation relieves an internal negative regulatory domain to activate GEF output.\",\n      \"evidence\": \"Systematic tyrosine mutagenesis (aa 391-579) with CrkI co-expression and Rap1-GTP loading\",\n      \"pmids\": [\"10318861\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"structural basis of the negative regulatory domain not defined\", \"kinase responsible in physiological settings not pinned down\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Established the in vivo requirement for C3G, showing it is essential for cell adhesion and early embryogenesis and that its role is interchangeable with other Rap1-activating GEFs.\",\n      \"evidence\": \"Knockout/conditional mouse, adhesion/migration assays, rescue by active Rap1, Rap2, R-Ras and other GEFs\",\n      \"pmids\": [\"11432821\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"tissue-specific downstream effectors not dissected\", \"GEF-independent contributions to phenotype not separated\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Connected C3G to specific adhesion structures and vascular development, showing it is needed for integrin-\\u03b21/paxillin focal adhesion formation in vivo.\",\n      \"evidence\": \"Hypomorphic knock-in mouse, focal adhesion immunofluorescence, PDGF response assays\",\n      \"pmids\": [\"12466202\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"selectivity for \\u03b21- over \\u03b23-adhesions mechanistically unexplained\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Defined GEF-independent functions, showing C3G's N-terminal Crk-binding domain suppresses ERK via PP2A recruitment, expanding its role beyond Rap1 activation.\",\n      \"evidence\": \"Focus/soft-agar assays, co-IP with PP2A and PP2A activity assays, okadaic acid\",\n      \"pmids\": [\"15077165\", \"17825818\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"direct PP2A binding interface not mapped\", \"single lab; reciprocal validation limited\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Placed C3G in the Reelin-Dab1 neuronal pathway, showing Reelin activates a Dab1\\u2192Crk\\u2192C3G\\u2192Rap1 cascade in cortical neurons.\",\n      \"evidence\": \"Phospho-Dab1 affinity pull-down, co-IP, Rap1-GTP assay in primary cortical neurons\",\n      \"pmids\": [\"15062102\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"downstream Rap1 effectors in migration not identified at this stage\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Demonstrated the developmental neuronal requirement, showing C3G is needed for preplate splitting, the multipolar-to-bipolar transition, and cortical neuron migration via Reelin-driven Rap1 activation.\",\n      \"evidence\": \"Conditional KO mice, Rap1-GTP after reelin, in utero imaging\",\n      \"pmids\": [\"18506028\", \"27111087\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"effector linking Rap1 to cytoskeletal remodeling in migrating neurons not fully defined\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Established a GEF-dependent role in hemostasis, showing C3G overexpression enhances and GEF-dead C3G impairs platelet activation downstream of PKC-Rap1.\",\n      \"evidence\": \"Platelet-specific transgenic mice (C3G and C3G\\u0394Cat), bleeding time, aggregation, Rap1 assays\",\n      \"pmids\": [\"22659131\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"upstream kinase coupling PKC to C3G not yet defined here\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Extended GEF-independent regulation to Wnt signaling, showing C3G binds and destabilizes \\u03b2-catenin to repress TCF transcription independent of GEF activity and GSK3\\u03b2.\",\n      \"evidence\": \"Reciprocal co-IP, domain mapping, TCF reporter, proteasome inhibitor\",\n      \"pmids\": [\"23486661\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"mechanism of \\u03b2-catenin destabilization unresolved\", \"single-lab finding\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Resolved the autoinhibition mechanism, showing an intramolecular AIR blocks the catalytic domain and CrkL activates by displacing it, with lymphoma AIR mutations causing constitutive activation.\",\n      \"evidence\": \"Intramolecular interaction mapping, nucleotide exchange assays, mutagenesis, Ba/F3 Rap1/LFA-1 readouts\",\n      \"pmids\": [\"32873726\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"high-resolution structure of the autoinhibited state not reported\", \"interplay of AIR release with Y504 phosphorylation not fully quantified here\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Defined platelet-specific phospho-regulation, showing PKC-Src drives Y504 phosphorylation, ERK supports it by inhibiting Shp2, and C3G feeds the P2Y12-PI3K-Rap1b and thrombin-TXA2 pathways.\",\n      \"evidence\": \"Platelet-specific KO mouse, pathway inhibitors, phospho-site assays\",\n      \"pmids\": [\"32296045\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"direct Shp2-C3G relationship not biochemically reconstituted\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Integrated phosphorylation and adaptor inputs into a two-factor activation model, showing Crk binding to segregated proline sites both recruits and directly stimulates C3G while Y504 phosphorylation primes the enzyme.\",\n      \"evidence\": \"ITC, sedimentation velocity, GEF kinetics, pull-downs, and membrane translocation in Jurkat cells\",\n      \"pmids\": [\"36737758\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"full-length structural model of the activated complex not determined\", \"in vivo verification across cell types incomplete\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How C3G's GEF-dependent Rap1 outputs are integrated with its GEF-independent nuclear, PP2A, and \\u03b2-catenin functions to produce cell-type-specific outcomes remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"no unified structural model of activated, membrane-bound C3G\", \"spatial coordination of Golgi/cytoskeletal/nuclear pools not defined\", \"physiological selection between Rap1 versus R-Ras outputs unclear\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005085\", \"supporting_discovery_ids\": [2, 19, 33]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [22, 31]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [22, 32]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [5, 40, 51]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [46]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 5, 12, 51]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [19, 21, 29, 44]},\n      {\"term_id\": \"R-HSA-109582\", \"supporting_discovery_ids\": [37, 49]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [18, 30, 40]},\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [11, 13, 21]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"CRK\", \"CRKL\", \"RAP1A\", \"HCK\", \"ABL1\", \"BCAR1\", \"CBL\", \"PPP2CA\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}