{"gene":"ARHGAP1","run_date":"2026-06-09T22:02:44","timeline":{"discoveries":[{"year":1997,"finding":"Crystal structure of the GAP domain of p50rhoGAP (ARHGAP1) in complex with Cdc42Hs-GMPPNP resolved at 2.7Å, showing that Cdc42Hs interacts through its switch I and II regions with a shallow pocket on rhoGAP lined with conserved residues, and that Arg85 of rhoGAP interacts with the P-loop of Cdc42Hs, proposed to stabilize the GTP hydrolysis transition state.","method":"X-ray crystallography (2.7Å resolution) with biochemical data","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with functional biochemical validation, published in Nature, foundational mechanistic paper","pmids":["9262406"],"is_preprint":false},{"year":1997,"finding":"Crystal structure of the isolated GAP domain of human p50rhoGAP (ARHGAP1) resolved at high resolution; the structure comprises nine α-helices arranged around a four-helix bundle core; conserved residues are clustered on one face proposed as the G-protein interaction site; Arg85 and Asn194 are proposed to be involved in G-protein binding and GTPase enhancement.","method":"X-ray crystallography","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure of isolated domain, independent study corroborating the Arg85 catalytic role","pmids":["9009196"],"is_preprint":false},{"year":1998,"finding":"Crystal structures of Cdc42 bound to wild-type Cdc42GAP (ARHGAP1) and to the catalytically compromised Cdc42GAP(R305A) mutant in aluminum fluoride transition-state mimics; these structures confirm that Cdc42GAP contributes Arg305 (the arginine finger) to the active site to stabilize the transition state for GTP hydrolysis, analogous to RasGAP; Cdc42GAP stabilizes both switch I and switch II domains of Cdc42.","method":"X-ray crystallography of transition-state mimics; site-directed mutagenesis (R305A)","journal":"Nature structural biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted transition-state complex structures plus mutagenesis, directly identifying the catalytic arginine finger","pmids":["9846874"],"is_preprint":false},{"year":1993,"finding":"In vitro GTPase assays and fibroblast microinjection showed that rhoGAP (ARHGAP1/p50rhoGAP) has striking preferential GAP activity for G25K (Cdc42) compared with Rho and Rac; microinjection of rhoGAP did not specifically inhibit rho-mediated stress fiber formation, consistent with its substrate preference for Cdc42/G25K in vivo.","method":"In vitro GTPase assay; microinjection into Swiss 3T3 fibroblasts","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro enzymatic assay plus in vivo microinjection, replicated substrate preference for Cdc42","pmids":["8262058"],"is_preprint":false},{"year":1994,"finding":"Purification and cDNA cloning of human rhoGAP (ARHGAP1/p50rhoGAP) identified a 50 kDa ubiquitously expressed protein; in vitro GTPase assays showed that Rho, Rac, and G25K/CDC42 all bind equally well to rhoGAP, but G25K/CDC42 is the preferred substrate for GTP hydrolysis stimulation; the protein contains a proline-rich sequence suggesting it is an SH3-binding protein.","method":"Protein purification, cDNA cloning, in vitro GTPase assay, binding assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — biochemical reconstitution with recombinant protein; foundational characterization paper","pmids":["8288572"],"is_preprint":false},{"year":1998,"finding":"Kinetic analysis of RhoA GTP hydrolysis stimulated by the GAP domain of p50RhoGAP (ARHGAP1) showed at least 4000-fold stimulation of intrinsic RhoA GTPase rate; p50RhoGAP has a low Km for activated RhoA (~2.83 µM) and shows product inhibition by binding the GDP-bound form of RhoA (Kd ~6 µM); p50RhoGAP remains partially active toward effector domain mutants of RhoA (Y34K, T37A), indicating distinct structural determinants of interaction compared with p190.","method":"In vitro kinetic GTPase assay with recombinant proteins; binding studies","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — rigorous quantitative in vitro enzymatic kinetics with multiple mutants, single lab","pmids":["9548756"],"is_preprint":false},{"year":2005,"finding":"The Sec14-like domain of p50RhoGAP (ARHGAP1) targets the protein to endosomal membranes where it colocalizes with internalized transferrin receptor and Rab5/Rab11; overexpression of p50RhoGAP or its Sec14-like domain alone inhibits transferrin uptake; bioluminescence resonance energy transfer demonstrated that p50RhoGAP forms a molecular complex with Rab11 on endosomal membranes, mediated by the Sec14-like domain, linking Rab and Rho GTPase regulation at endosomes.","method":"Subcellular fractionation, co-localization imaging, transferrin uptake assay, BRET","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — BRET for interaction, functional uptake assay, and localization; single lab, multiple orthogonal methods","pmids":["16380373"],"is_preprint":false},{"year":2006,"finding":"Gene targeting of Cdc42GAP (ARHGAP1) in primary mouse embryonic fibroblasts (Cdc42GAP−/− MEFs) resulted in elevated Cdc42 activity (gain-of-function model); these cells displayed spontaneous filopodia, defective adhesion to fibronectin, impaired wound-healing, polarity establishment, and directional migration, with deficiencies in PAK1, GSK3β, myosin light chain, and FAK phosphorylation, demonstrating that ARHGAP1-regulated Cdc42 activity controls filopodia induction, polarity, and migration in primary fibroblasts.","method":"Gene targeting/knockout, GTPase activity assay, cell migration assay, phosphorylation analysis","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic knockout with multiple orthogonal functional readouts and biochemical pathway analysis","pmids":["16914516"],"is_preprint":false},{"year":2005,"finding":"Genetic deletion of Cdc42GAP (ARHGAP1) in mice resulted in 3-fold elevated Cdc42 activity in hematopoietic tissues with normal Rac and RhoA activities; Cdc42GAP−/− mice were anemic with reduced hematopoietic stem/progenitor cell (HSP) numbers due to increased JNK-mediated apoptosis; HSPs showed impaired cortical F-actin assembly, deficient adhesion and migration, and defective engraftment, establishing ARHGAP1 as a critical regulator of Cdc42 activity in hematopoiesis.","method":"Gene targeting/knockout, GTPase activity assay, hematopoietic reconstitution, apoptosis assay, adhesion and migration assays","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean knockout with specific Cdc42 activity measurement and multiple functional hematopoietic readouts","pmids":["16174757"],"is_preprint":false},{"year":2005,"finding":"Genetic disruption of Cdc42GAP (ARHGAP1) in mice caused approximately 25–40% reduction in body size and growth retardation during the perinatal period; Cdc42GAP−/− cells and tissues showed significantly elevated Cdc42 activity; increased basal apoptosis was attributed to altered c-Jun N-terminal kinase (JNK) apoptotic signals, establishing ARHGAP1 as a regulator of perinatal growth through the Cdc42-JNK apoptosis pathway.","method":"Gene targeting/knockout, Cdc42 GTPase activity assay, apoptosis assays, JNK pathway analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean knockout with pathway-specific GTPase and kinase measurements, multiple tissues","pmids":["16157885"],"is_preprint":false},{"year":2008,"finding":"Nudel, a cytoplasmic dynein regulator, competes with Cdc42 for binding to Cdc42GAP (ARHGAP1), thereby inhibiting Cdc42GAP-mediated inactivation of Cdc42 in a dose-dependent manner; both Nudel and Cdc42GAP localize to the leading edge in migrating cells; Nudel localization requires Erk1/2-mediated phosphorylation; RNAi depletion of Nudel abolishes Cdc42 activation and cell migration, establishing Nudel as a regulator that sequesters ARHGAP1 to sustain active Cdc42 at the leading edge.","method":"Co-IP, in vitro competition binding assay, RNAi knockdown, cell migration assay, Cdc42 activity assay, immunofluorescence","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (Co-IP, in vitro competition, RNAi with functional readouts, Cdc42 activity assay)","pmids":["18331715"],"is_preprint":false},{"year":2009,"finding":"Cdc42GAP (ARHGAP1) was cloned from smooth muscle; wild-type Cdc42GAP but not the catalytic mutant R282A enhanced Cdc42 GTP hydrolysis in vitro; agonist stimulation of smooth muscle cells with 5-HT decreased Cdc42GAP activity through reactive oxygen species (ROS); expression of wild-type Cdc42GAP inhibited agonist-induced Cdc42 activation, PAK phosphorylation at Thr-423, vimentin phosphorylation at Ser-56, vimentin remodeling, and smooth muscle contraction, establishing ARHGAP1 as a regulator of the Cdc42-PAK-vimentin axis in smooth muscle.","method":"In vitro GTPase assay, retroviral expression of wild-type and R282A mutant, ROS inhibitor pharmacology, phosphorylation analysis, contraction assay","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro enzymatic assay with mutagenesis plus in vivo functional pathway analysis, single lab","pmids":["19494238"],"is_preprint":false},{"year":2009,"finding":"p47(phox), a regulatory subunit of NADPH oxidase, mediates agonist-induced ROS production that suppresses Cdc42GAP (ARHGAP1) activity in smooth muscle cells; shRNA knockdown of p47(phox) attenuated ROS production, preserved Cdc42GAP activity, and reduced Cdc42 activation, PAK1 phosphorylation, vimentin phosphorylation, and smooth muscle contraction in response to 5-HT.","method":"shRNA knockdown, in vitro Cdc42GAP activity assay, ROS measurement, phosphorylation analysis, contraction assay","journal":"American journal of physiology. Cell physiology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — shRNA with multiple downstream readouts confirming pathway, single lab","pmids":["19812368"],"is_preprint":false},{"year":2000,"finding":"BNIP-2 and Cdc42GAP (ARHGAP1) directly bind each other and compete for binding to Cdc42 via their conserved BCH (BNIP-2 and Cdc42GAP Homology) domains; the BCH domain of Cdc42GAP can bind Cdc42 but is catalytically inactive; BNIP-2 BCH can stimulate Cdc42 GTPase activity via an arginine-patch motif; yeast two-hybrid and GST pulldown confirmed homo- and hetero-complex formation via BCH domains.","method":"GST pulldown, co-immunoprecipitation, yeast two-hybrid, in vitro GTPase assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — multiple binding assays and enzymatic characterization; interaction with BNIP-2 via BCH domain established","pmids":["10954711"],"is_preprint":false},{"year":1999,"finding":"BNIP-2 interacts with Cdc42GAP (ARHGAP1) via their BCH domains, and they compete for binding to Cdc42; fibroblast growth factor receptor-1 (FGFR1) phosphorylates BNIP-2 on tyrosine; tyrosine phosphorylation of BNIP-2 by FGFR1 impaired its association with Cdc42GAP and abolished BNIP-2's GAP-like activity toward Cdc42, establishing a regulatory crosstalk between receptor tyrosine kinase signaling and Cdc42GAP activity.","method":"Co-immunoprecipitation, in vitro phosphorylation assay, in vitro GTPase assay, transient transfection","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — in vitro kinase assay plus GTPase assay and co-IP, single lab","pmids":["10551883"],"is_preprint":false},{"year":2010,"finding":"The BCH domain of p50RhoGAP/Cdc42GAP (ARHGAP1) sequesters RhoA from inactivation by the adjacent GAP domain in cis; deletion of the BCH domain enhanced GAP activity and caused drastic cell rounding reversed by constitutively active RhoA or by inactivating the GAP domain; the BCH domain selectively targeted RhoA (not Cdc42 or Rac1) regardless of nucleotide-binding state; a RhoA-binding motif (residues 85–120) and an intramolecular interaction motif (residues 169–197) within the BCH domain were identified by mutagenesis as necessary for suppression of GAP activity.","method":"Domain deletion, site-directed mutagenesis, cell morphology assay, RhoA pull-down, GTPase assay","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — mutagenesis combined with functional cellular and biochemical assays establishing intramolecular regulation; single lab, multiple orthogonal methods","pmids":["20660160"],"is_preprint":false},{"year":2006,"finding":"Overexpression of BNIP-Sα displaces p50RhoGAP/Cdc42GAP (ARHGAP1) from RhoA through competitive interactions via overlapping binding motifs in the BCH domain (residues 133–177), thereby facilitating RhoA activation; cell rounding and apoptosis induced by BNIP-Sα were completely prevented by dominant-negative RhoA or by deletion of the RhoA-binding motif, establishing that competitive displacement of ARHGAP1 from RhoA drives the cellular phenotype.","method":"Co-immunoprecipitation, mutagenesis, cell morphology assay, apoptosis assay","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — co-IP with mutagenesis and functional cellular assays, single lab","pmids":["16331259"],"is_preprint":false},{"year":2013,"finding":"In zebrafish, Arhgap1 restricts Rho activation to the apical region of premigratory neural crest cells during epithelial-to-mesenchymal transition (EMT); loss of Arhgap1 caused Rho activation to spread beyond the apical region, preventing proper apical detachment; imaging of endogenous active Rho in vivo showed a discrete apical cap of active Rho during EMT, and Rho-ROCK signaling was essential for apical detachment, establishing ARHGAP1 as a spatial regulator of Rho during EMT in vivo.","method":"In vivo FRET-based Rho activity biosensor imaging, morpholino-based loss-of-function, pharmacological ROCK inhibition","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo biosensor imaging with genetic loss-of-function and pharmacological rescue; direct visualization of Rho activity pattern","pmids":["23804498"],"is_preprint":false},{"year":2000,"finding":"IGFBP-5(201–218) stimulation of mesangial cells caused rapid aggregation of Cdc42GAP (ARHGAP1) as detected by immunofluorescence, concurrent with filopodia formation and actin reorganization; staurosporin inhibited both migration and Cdc42GAP aggregation only when added in the first hour, suggesting Cdc42GAP aggregation is downstream of an IGFBP-5 receptor serine/threonine kinase.","method":"Immunofluorescence microscopy, pharmacological inhibition, wounding assay","journal":"Kidney international","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single localization method without mechanistic molecular detail; pharmacological correlation only","pmids":["10792618"],"is_preprint":false},{"year":2004,"finding":"ARHGAP8, a novel RHOGAP protein, shares identical domain architecture with ARHGAP1/CDC42GAP/p50RHOGAP including a C-terminal RHOGAP domain, a central SH3-binding motif, and an N-terminal BCH/Sec14p-like domain, indicating that ARHGAP1 defines a structural subfamily among RhoGAP proteins.","method":"Sequence/domain analysis, genomic organization comparison","journal":"Gene","confidence":"Low","confidence_rationale":"Tier 4 / Weak — bioinformatics/structural classification only, no functional experiment on ARHGAP1 itself","pmids":["15225876"],"is_preprint":false}],"current_model":"ARHGAP1 (p50RhoGAP/Cdc42GAP) is a ubiquitously expressed RhoGAP whose crystal structures in complex with Cdc42 define its catalytic mechanism: the arginine finger (Arg305) stabilizes the GTP hydrolysis transition state while Cdc42 switch I and II regions dock into a conserved surface pocket; ARHGAP1 has a strong enzymatic preference for Cdc42 as a substrate but also stimulates RhoA and Rac GTP hydrolysis; its activity is spatially regulated at the cell leading edge by Nudel (which competes with Cdc42 for ARHGAP1 binding), by reactive oxygen species downstream of NADPH oxidase, and intramolecularly by its N-terminal BCH/Sec14-like domain (which sequesters RhoA from the adjacent GAP domain); the Sec14-like domain also targets ARHGAP1 to endosomal membranes where it forms a complex with Rab11; genetic knockout in mice and fibroblasts establishes that ARHGAP1 controls Cdc42 activity to regulate filopodia formation, cell polarity, directional migration, hematopoietic stem cell survival and engraftment, perinatal body growth via the Cdc42-JNK apoptosis axis, and smooth muscle contraction through the Cdc42-PAK-vimentin pathway; in neural crest cells, ARHGAP1 restricts active Rho to the cell apex to enable apical detachment during EMT."},"narrative":{"mechanistic_narrative":"ARHGAP1 (p50RhoGAP/Cdc42GAP) is a ubiquitously expressed Rho-family GTPase-activating protein that terminates Cdc42/Rho signaling to control actin-dependent processes including filopodia formation, cell polarity, directional migration, and apoptotic survival [PMID:8288572, PMID:16914516]. Crystal structures of its GAP domain bound to Cdc42 establish the catalytic mechanism: the protein contributes an arginine finger (Arg305) that stabilizes the GTP-hydrolysis transition state while clamping the switch I and switch II regions of the bound GTPase, with the R305A (and equivalently R282A/R85) mutant abolishing catalysis [PMID:9262406, PMID:9846874, PMID:20660160]. Biochemically, ARHGAP1 binds Rho, Rac, and Cdc42 comparably but strongly prefers Cdc42 as a substrate for hydrolysis stimulation while also accelerating RhoA GTP hydrolysis several-thousand-fold [PMID:8262058, PMID:8288572, PMID:9548756]. Its activity is spatially and intramolecularly tuned through its N-terminal BCH/Sec14-like domain, which sequesters RhoA in cis to suppress the adjacent GAP domain and which targets the protein to endosomal membranes in a complex with Rab11 [PMID:20660160, PMID:16380373]; the BCH domain also mediates competitive interactions with BNIP-2 and BNIP-Sα that displace ARHGAP1 from Cdc42 or RhoA [PMID:10954711, PMID:16331259]. At the migrating leading edge, Nudel competes with Cdc42 for ARHGAP1 binding to sustain local Cdc42 activation, and ROS generated by NADPH oxidase (p47phox) suppress ARHGAP1 activity downstream of agonist stimulation [PMID:18331715, PMID:19812368]. Gene knockout in mice and fibroblasts produces Cdc42 gain-of-function, demonstrating that ARHGAP1 governs filopodia and polarity in fibroblasts, hematopoietic stem/progenitor survival via the Cdc42-JNK apoptosis axis, perinatal body growth, and smooth muscle contraction through a Cdc42-PAK-vimentin pathway [PMID:16914516, PMID:16174757, PMID:16157885, PMID:19494238]. In vivo, ARHGAP1 spatially restricts active Rho to the apex of premigratory neural crest cells to permit apical detachment during EMT [PMID:23804498].","teleology":[{"year":1994,"claim":"Established the basic identity and biochemical activity of ARHGAP1, answering whether the 50 kDa protein was a general RhoGAP or one with substrate selectivity.","evidence":"Protein purification, cDNA cloning, and in vitro GTPase/binding assays of human p50rhoGAP","pmids":["8288572","8262058"],"confidence":"High","gaps":["Substrate preference defined biochemically but cellular significance unresolved","Structural basis of selectivity unknown"]},{"year":1998,"claim":"Resolved the catalytic mechanism by defining how ARHGAP1 accelerates GTP hydrolysis, addressing how a GAP enhances an intrinsically slow GTPase.","evidence":"X-ray crystallography of isolated GAP domain and of Cdc42-GAP transition-state mimic complexes with R305A mutagenesis, plus quantitative RhoA kinetics","pmids":["9009196","9262406","9846874","9548756"],"confidence":"High","gaps":["Structures use isolated GAP domain, not full-length protein","Does not address intramolecular or spatial regulation in cells"]},{"year":2000,"claim":"Identified the BCH domain as a protein-protein interaction module that competes for Cdc42/RhoA, raising the question of how RTK and adaptor signals feed into ARHGAP1 regulation.","evidence":"Yeast two-hybrid, GST pulldown, co-IP, in vitro phosphorylation and GTPase assays with BNIP-2 and FGFR1","pmids":["10954711","10551883"],"confidence":"Medium","gaps":["Functional consequence of BNIP-2 competition in cells not established","Single-lab interaction data"]},{"year":2006,"claim":"Demonstrated in vivo physiological roles via genetic knockout, answering what cellular and organismal processes ARHGAP1-controlled Cdc42 activity governs.","evidence":"Cdc42GAP knockout mice and MEFs with GTPase, migration, apoptosis, hematopoietic reconstitution, and JNK pathway readouts","pmids":["16914516","16174757","16157885"],"confidence":"High","gaps":["Knockout is a Cdc42 gain-of-function model; does not isolate Rho/Rac contributions","Tissue-specific mechanisms partly inferred"]},{"year":2006,"claim":"Linked ARHGAP1 to membrane trafficking by showing Sec14-like domain targeting to endosomes and Rab11 complex formation, addressing where in the cell it acts.","evidence":"Subcellular fractionation, transferrin uptake assay, colocalization, and BRET","pmids":["16380373"],"confidence":"Medium","gaps":["Single-lab data; reciprocal validation limited","Functional consequence of Rab11 complex on Rho signaling not fully defined"]},{"year":2010,"claim":"Resolved how ARHGAP1 activity is autoregulated by showing the BCH domain sequesters RhoA in cis from the adjacent GAP domain, explaining substrate gating within the protein.","evidence":"Domain deletion, site-directed mutagenesis, RhoA pulldown, and cell morphology assays","pmids":["20660160","16331259"],"confidence":"High","gaps":["Structural model of the closed/open intramolecular state lacking","Signals that relieve BCH autoinhibition in vivo unclear"]},{"year":2009,"claim":"Defined spatial and signal-dependent regulation at the leading edge and in smooth muscle, answering how local GAP activity is dynamically modulated by upstream signals.","evidence":"Nudel competition Co-IP/RNAi with Cdc42 activity readouts; ROS/p47phox-dependent suppression of GAP activity with PAK-vimentin-contraction readouts","pmids":["18331715","19494238","19812368"],"confidence":"High","gaps":["Molecular target of ROS on ARHGAP1 (oxidized residue) not identified","Crosstalk between Nudel and ROS regulation not integrated"]},{"year":2013,"claim":"Showed in vivo spatial control of Rho during morphogenesis, establishing ARHGAP1 as a positional regulator of GTPase activity during EMT.","evidence":"Zebrafish FRET Rho biosensor imaging with morpholino loss-of-function and ROCK pharmacology in neural crest cells","pmids":["23804498"],"confidence":"High","gaps":["Mechanism localizing ARHGAP1 to the apical domain unknown","Relationship to mammalian roles not directly tested"]},{"year":null,"claim":"How the distinct regulatory inputs (BCH autoinhibition, Nudel sequestration, ROS oxidation, Rab11 endosomal targeting) are integrated to produce substrate- and location-specific GTPase inactivation in vivo remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No full-length structure capturing autoinhibited vs active states","Direct ROS-modified residue unidentified","Integration of competing regulators at a single subcellular site untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,2,3,4,5,15]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[2,5,11]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[6]}],"localization":[{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[6]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[10]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[4]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[7,8,9,11]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[6]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[8,9]}],"complexes":[],"partners":["CDC42","RHOA","RAC1","RAB11","NDEL1","BNIP2","BNIPSA"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q07960","full_name":"Rho GTPase-activating protein 1","aliases":["CDC42 GTPase-activating protein","GTPase-activating protein rhoGAP","Rho-related small GTPase protein activator","Rho-type GTPase-activating protein 1","p50-RhoGAP"],"length_aa":439,"mass_kda":50.4,"function":"GTPase activator for the Rho, Rac and Cdc42 proteins, converting them to the putatively inactive GDP-bound state. Cdc42 seems to be the preferred substrate","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q07960/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ARHGAP1","classification":"Not Classified","n_dependent_lines":53,"n_total_lines":1208,"dependency_fraction":0.043874172185430466},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000175220","cell_line_id":"CID000590","localizations":[{"compartment":"er","grade":3},{"compartment":"golgi","grade":3},{"compartment":"vesicles","grade":3},{"compartment":"cytoplasmic","grade":1}],"interactors":[{"gene":"RHOC","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000590","total_profiled":1310},"omim":[{"mim_id":"621479","title":"MICRO RNA 940; MIR940","url":"https://www.omim.org/entry/621479"},{"mim_id":"621473","title":"RETICULOPHAGY REGULATOR FAMILY, MEMBER 2; RETREG2","url":"https://www.omim.org/entry/621473"},{"mim_id":"617368","title":"SH3 DOMAIN-BINDING PROTEIN 1; SH3BP1","url":"https://www.omim.org/entry/617368"},{"mim_id":"611275","title":"BCL2/ADENOVIRUS E1B 19-KD PROTEIN-INTERACTING PROTEIN 2-LIKE; BNIPL","url":"https://www.omim.org/entry/611275"},{"mim_id":"610691","title":"PRUNE HOMOLOG 2 WITH BCH DOMAIN; PRUNE2","url":"https://www.omim.org/entry/610691"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"},{"location":"Vesicles","reliability":"Additional"},{"location":"Primary cilium","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/ARHGAP1"},"hgnc":{"alias_symbol":["RhoGAP","p50rhoGAP","CDC42GAP","Cdc42GAP"],"prev_symbol":[]},"alphafold":{"accession":"Q07960","domains":[{"cath_id":"3.40.525.10","chopping":"57-221","consensus_level":"high","plddt":87.1285,"start":57,"end":221},{"cath_id":"1.10.555.10","chopping":"247-431","consensus_level":"high","plddt":93.2566,"start":247,"end":431}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q07960","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q07960-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q07960-F1-predicted_aligned_error_v6.png","plddt_mean":82.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ARHGAP1","jax_strain_url":"https://www.jax.org/strain/search?query=ARHGAP1"},"sequence":{"accession":"Q07960","fasta_url":"https://rest.uniprot.org/uniprotkb/Q07960.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q07960/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q07960"}},"corpus_meta":[{"pmid":"11782313","id":"PMC_11782313","title":"Central spindle assembly and cytokinesis require a kinesin-like protein/RhoGAP complex with microtubule bundling activity.","date":"2002","source":"Developmental cell","url":"https://pubmed.ncbi.nlm.nih.gov/11782313","citation_count":424,"is_preprint":false},{"pmid":"9582072","id":"PMC_9582072","title":"Oligophrenin-1 encodes a rhoGAP protein involved in X-linked mental retardation.","date":"1998","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/9582072","citation_count":355,"is_preprint":false},{"pmid":"9262406","id":"PMC_9262406","title":"Crystal structure of a small G protein in complex with the GTPase-activating protein rhoGAP.","date":"1997","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/9262406","citation_count":235,"is_preprint":false},{"pmid":"8262058","id":"PMC_8262058","title":"rho family GTPase activating proteins p190, bcr and rhoGAP show distinct specificities in vitro and in vivo.","date":"1993","source":"The EMBO 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one","url":"https://pubmed.ncbi.nlm.nih.gov/25211221","citation_count":28,"is_preprint":false},{"pmid":"20860838","id":"PMC_20860838","title":"P190B RhoGAP has pro-tumorigenic functions during MMTV-Neu mammary tumorigenesis and metastasis.","date":"2010","source":"Breast cancer research : BCR","url":"https://pubmed.ncbi.nlm.nih.gov/20860838","citation_count":28,"is_preprint":false},{"pmid":"20530197","id":"PMC_20530197","title":"The anaphase-promoting complex/cyclosome activator Cdh1 modulates Rho GTPase by targeting p190 RhoGAP for degradation.","date":"2010","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/20530197","citation_count":28,"is_preprint":false},{"pmid":"29310936","id":"PMC_29310936","title":"The RhoGAP Stard13 controls insulin secretion through F-actin remodeling.","date":"2017","source":"Molecular metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/29310936","citation_count":26,"is_preprint":false},{"pmid":"38621923","id":"PMC_38621923","title":"Recurrent RhoGAP gene fusion CLDN18-ARHGAP26 promotes RHOA activation and focal adhesion kinase and YAP-TEAD signalling in diffuse gastric cancer.","date":"2024","source":"Gut","url":"https://pubmed.ncbi.nlm.nih.gov/38621923","citation_count":25,"is_preprint":false},{"pmid":"24259668","id":"PMC_24259668","title":"The RhoGAP ARHGAP19 controls cytokinesis and chromosome segregation in T lymphocytes.","date":"2013","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/24259668","citation_count":25,"is_preprint":false},{"pmid":"20660160","id":"PMC_20660160","title":"The BNIP-2 and Cdc42GAP homology (BCH) domain of p50RhoGAP/Cdc42GAP sequesters RhoA from inactivation by the adjacent GTPase-activating protein domain.","date":"2010","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/20660160","citation_count":24,"is_preprint":false},{"pmid":"19812368","id":"PMC_19812368","title":"Role of p47(phox) in regulating Cdc42GAP, vimentin, and contraction in smooth muscle cells.","date":"2009","source":"American journal of physiology. Cell physiology","url":"https://pubmed.ncbi.nlm.nih.gov/19812368","citation_count":24,"is_preprint":false},{"pmid":"18845541","id":"PMC_18845541","title":"Phosphoinositides affect both the cellular distribution and activity of the F-BAR-containing RhoGAP Rgd1p in yeast.","date":"2008","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/18845541","citation_count":24,"is_preprint":false},{"pmid":"32378260","id":"PMC_32378260","title":"Comprehensive analysis on the whole Rho-GAP family reveals that ARHGAP4 suppresses EMT in epithelial cells under negative regulation by Septin9.","date":"2020","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/32378260","citation_count":24,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":49571,"output_tokens":5749,"usd":0.117474,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":14287,"output_tokens":3308,"usd":0.077067,"stage2_stop_reason":"end_turn"},"total_usd":0.194541,"stage1_batch_id":"msgbatch_0179Z2pxRYBsXi2xADneafRw","stage2_batch_id":"msgbatch_01LaY9ZaVdgjWArcZo9eqQE5","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1997,\n      \"finding\": \"Crystal structure of the GAP domain of p50rhoGAP (ARHGAP1) in complex with Cdc42Hs-GMPPNP resolved at 2.7Å, showing that Cdc42Hs interacts through its switch I and II regions with a shallow pocket on rhoGAP lined with conserved residues, and that Arg85 of rhoGAP interacts with the P-loop of Cdc42Hs, proposed to stabilize the GTP hydrolysis transition state.\",\n      \"method\": \"X-ray crystallography (2.7Å resolution) with biochemical data\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with functional biochemical validation, published in Nature, foundational mechanistic paper\",\n      \"pmids\": [\"9262406\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Crystal structure of the isolated GAP domain of human p50rhoGAP (ARHGAP1) resolved at high resolution; the structure comprises nine α-helices arranged around a four-helix bundle core; conserved residues are clustered on one face proposed as the G-protein interaction site; Arg85 and Asn194 are proposed to be involved in G-protein binding and GTPase enhancement.\",\n      \"method\": \"X-ray crystallography\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure of isolated domain, independent study corroborating the Arg85 catalytic role\",\n      \"pmids\": [\"9009196\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Crystal structures of Cdc42 bound to wild-type Cdc42GAP (ARHGAP1) and to the catalytically compromised Cdc42GAP(R305A) mutant in aluminum fluoride transition-state mimics; these structures confirm that Cdc42GAP contributes Arg305 (the arginine finger) to the active site to stabilize the transition state for GTP hydrolysis, analogous to RasGAP; Cdc42GAP stabilizes both switch I and switch II domains of Cdc42.\",\n      \"method\": \"X-ray crystallography of transition-state mimics; site-directed mutagenesis (R305A)\",\n      \"journal\": \"Nature structural biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted transition-state complex structures plus mutagenesis, directly identifying the catalytic arginine finger\",\n      \"pmids\": [\"9846874\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"In vitro GTPase assays and fibroblast microinjection showed that rhoGAP (ARHGAP1/p50rhoGAP) has striking preferential GAP activity for G25K (Cdc42) compared with Rho and Rac; microinjection of rhoGAP did not specifically inhibit rho-mediated stress fiber formation, consistent with its substrate preference for Cdc42/G25K in vivo.\",\n      \"method\": \"In vitro GTPase assay; microinjection into Swiss 3T3 fibroblasts\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro enzymatic assay plus in vivo microinjection, replicated substrate preference for Cdc42\",\n      \"pmids\": [\"8262058\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Purification and cDNA cloning of human rhoGAP (ARHGAP1/p50rhoGAP) identified a 50 kDa ubiquitously expressed protein; in vitro GTPase assays showed that Rho, Rac, and G25K/CDC42 all bind equally well to rhoGAP, but G25K/CDC42 is the preferred substrate for GTP hydrolysis stimulation; the protein contains a proline-rich sequence suggesting it is an SH3-binding protein.\",\n      \"method\": \"Protein purification, cDNA cloning, in vitro GTPase assay, binding assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — biochemical reconstitution with recombinant protein; foundational characterization paper\",\n      \"pmids\": [\"8288572\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Kinetic analysis of RhoA GTP hydrolysis stimulated by the GAP domain of p50RhoGAP (ARHGAP1) showed at least 4000-fold stimulation of intrinsic RhoA GTPase rate; p50RhoGAP has a low Km for activated RhoA (~2.83 µM) and shows product inhibition by binding the GDP-bound form of RhoA (Kd ~6 µM); p50RhoGAP remains partially active toward effector domain mutants of RhoA (Y34K, T37A), indicating distinct structural determinants of interaction compared with p190.\",\n      \"method\": \"In vitro kinetic GTPase assay with recombinant proteins; binding studies\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — rigorous quantitative in vitro enzymatic kinetics with multiple mutants, single lab\",\n      \"pmids\": [\"9548756\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The Sec14-like domain of p50RhoGAP (ARHGAP1) targets the protein to endosomal membranes where it colocalizes with internalized transferrin receptor and Rab5/Rab11; overexpression of p50RhoGAP or its Sec14-like domain alone inhibits transferrin uptake; bioluminescence resonance energy transfer demonstrated that p50RhoGAP forms a molecular complex with Rab11 on endosomal membranes, mediated by the Sec14-like domain, linking Rab and Rho GTPase regulation at endosomes.\",\n      \"method\": \"Subcellular fractionation, co-localization imaging, transferrin uptake assay, BRET\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — BRET for interaction, functional uptake assay, and localization; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"16380373\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Gene targeting of Cdc42GAP (ARHGAP1) in primary mouse embryonic fibroblasts (Cdc42GAP−/− MEFs) resulted in elevated Cdc42 activity (gain-of-function model); these cells displayed spontaneous filopodia, defective adhesion to fibronectin, impaired wound-healing, polarity establishment, and directional migration, with deficiencies in PAK1, GSK3β, myosin light chain, and FAK phosphorylation, demonstrating that ARHGAP1-regulated Cdc42 activity controls filopodia induction, polarity, and migration in primary fibroblasts.\",\n      \"method\": \"Gene targeting/knockout, GTPase activity assay, cell migration assay, phosphorylation analysis\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic knockout with multiple orthogonal functional readouts and biochemical pathway analysis\",\n      \"pmids\": [\"16914516\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Genetic deletion of Cdc42GAP (ARHGAP1) in mice resulted in 3-fold elevated Cdc42 activity in hematopoietic tissues with normal Rac and RhoA activities; Cdc42GAP−/− mice were anemic with reduced hematopoietic stem/progenitor cell (HSP) numbers due to increased JNK-mediated apoptosis; HSPs showed impaired cortical F-actin assembly, deficient adhesion and migration, and defective engraftment, establishing ARHGAP1 as a critical regulator of Cdc42 activity in hematopoiesis.\",\n      \"method\": \"Gene targeting/knockout, GTPase activity assay, hematopoietic reconstitution, apoptosis assay, adhesion and migration assays\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean knockout with specific Cdc42 activity measurement and multiple functional hematopoietic readouts\",\n      \"pmids\": [\"16174757\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Genetic disruption of Cdc42GAP (ARHGAP1) in mice caused approximately 25–40% reduction in body size and growth retardation during the perinatal period; Cdc42GAP−/− cells and tissues showed significantly elevated Cdc42 activity; increased basal apoptosis was attributed to altered c-Jun N-terminal kinase (JNK) apoptotic signals, establishing ARHGAP1 as a regulator of perinatal growth through the Cdc42-JNK apoptosis pathway.\",\n      \"method\": \"Gene targeting/knockout, Cdc42 GTPase activity assay, apoptosis assays, JNK pathway analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean knockout with pathway-specific GTPase and kinase measurements, multiple tissues\",\n      \"pmids\": [\"16157885\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Nudel, a cytoplasmic dynein regulator, competes with Cdc42 for binding to Cdc42GAP (ARHGAP1), thereby inhibiting Cdc42GAP-mediated inactivation of Cdc42 in a dose-dependent manner; both Nudel and Cdc42GAP localize to the leading edge in migrating cells; Nudel localization requires Erk1/2-mediated phosphorylation; RNAi depletion of Nudel abolishes Cdc42 activation and cell migration, establishing Nudel as a regulator that sequesters ARHGAP1 to sustain active Cdc42 at the leading edge.\",\n      \"method\": \"Co-IP, in vitro competition binding assay, RNAi knockdown, cell migration assay, Cdc42 activity assay, immunofluorescence\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (Co-IP, in vitro competition, RNAi with functional readouts, Cdc42 activity assay)\",\n      \"pmids\": [\"18331715\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Cdc42GAP (ARHGAP1) was cloned from smooth muscle; wild-type Cdc42GAP but not the catalytic mutant R282A enhanced Cdc42 GTP hydrolysis in vitro; agonist stimulation of smooth muscle cells with 5-HT decreased Cdc42GAP activity through reactive oxygen species (ROS); expression of wild-type Cdc42GAP inhibited agonist-induced Cdc42 activation, PAK phosphorylation at Thr-423, vimentin phosphorylation at Ser-56, vimentin remodeling, and smooth muscle contraction, establishing ARHGAP1 as a regulator of the Cdc42-PAK-vimentin axis in smooth muscle.\",\n      \"method\": \"In vitro GTPase assay, retroviral expression of wild-type and R282A mutant, ROS inhibitor pharmacology, phosphorylation analysis, contraction assay\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro enzymatic assay with mutagenesis plus in vivo functional pathway analysis, single lab\",\n      \"pmids\": [\"19494238\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"p47(phox), a regulatory subunit of NADPH oxidase, mediates agonist-induced ROS production that suppresses Cdc42GAP (ARHGAP1) activity in smooth muscle cells; shRNA knockdown of p47(phox) attenuated ROS production, preserved Cdc42GAP activity, and reduced Cdc42 activation, PAK1 phosphorylation, vimentin phosphorylation, and smooth muscle contraction in response to 5-HT.\",\n      \"method\": \"shRNA knockdown, in vitro Cdc42GAP activity assay, ROS measurement, phosphorylation analysis, contraction assay\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — shRNA with multiple downstream readouts confirming pathway, single lab\",\n      \"pmids\": [\"19812368\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"BNIP-2 and Cdc42GAP (ARHGAP1) directly bind each other and compete for binding to Cdc42 via their conserved BCH (BNIP-2 and Cdc42GAP Homology) domains; the BCH domain of Cdc42GAP can bind Cdc42 but is catalytically inactive; BNIP-2 BCH can stimulate Cdc42 GTPase activity via an arginine-patch motif; yeast two-hybrid and GST pulldown confirmed homo- and hetero-complex formation via BCH domains.\",\n      \"method\": \"GST pulldown, co-immunoprecipitation, yeast two-hybrid, in vitro GTPase assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — multiple binding assays and enzymatic characterization; interaction with BNIP-2 via BCH domain established\",\n      \"pmids\": [\"10954711\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"BNIP-2 interacts with Cdc42GAP (ARHGAP1) via their BCH domains, and they compete for binding to Cdc42; fibroblast growth factor receptor-1 (FGFR1) phosphorylates BNIP-2 on tyrosine; tyrosine phosphorylation of BNIP-2 by FGFR1 impaired its association with Cdc42GAP and abolished BNIP-2's GAP-like activity toward Cdc42, establishing a regulatory crosstalk between receptor tyrosine kinase signaling and Cdc42GAP activity.\",\n      \"method\": \"Co-immunoprecipitation, in vitro phosphorylation assay, in vitro GTPase assay, transient transfection\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — in vitro kinase assay plus GTPase assay and co-IP, single lab\",\n      \"pmids\": [\"10551883\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The BCH domain of p50RhoGAP/Cdc42GAP (ARHGAP1) sequesters RhoA from inactivation by the adjacent GAP domain in cis; deletion of the BCH domain enhanced GAP activity and caused drastic cell rounding reversed by constitutively active RhoA or by inactivating the GAP domain; the BCH domain selectively targeted RhoA (not Cdc42 or Rac1) regardless of nucleotide-binding state; a RhoA-binding motif (residues 85–120) and an intramolecular interaction motif (residues 169–197) within the BCH domain were identified by mutagenesis as necessary for suppression of GAP activity.\",\n      \"method\": \"Domain deletion, site-directed mutagenesis, cell morphology assay, RhoA pull-down, GTPase assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — mutagenesis combined with functional cellular and biochemical assays establishing intramolecular regulation; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"20660160\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Overexpression of BNIP-Sα displaces p50RhoGAP/Cdc42GAP (ARHGAP1) from RhoA through competitive interactions via overlapping binding motifs in the BCH domain (residues 133–177), thereby facilitating RhoA activation; cell rounding and apoptosis induced by BNIP-Sα were completely prevented by dominant-negative RhoA or by deletion of the RhoA-binding motif, establishing that competitive displacement of ARHGAP1 from RhoA drives the cellular phenotype.\",\n      \"method\": \"Co-immunoprecipitation, mutagenesis, cell morphology assay, apoptosis assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — co-IP with mutagenesis and functional cellular assays, single lab\",\n      \"pmids\": [\"16331259\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"In zebrafish, Arhgap1 restricts Rho activation to the apical region of premigratory neural crest cells during epithelial-to-mesenchymal transition (EMT); loss of Arhgap1 caused Rho activation to spread beyond the apical region, preventing proper apical detachment; imaging of endogenous active Rho in vivo showed a discrete apical cap of active Rho during EMT, and Rho-ROCK signaling was essential for apical detachment, establishing ARHGAP1 as a spatial regulator of Rho during EMT in vivo.\",\n      \"method\": \"In vivo FRET-based Rho activity biosensor imaging, morpholino-based loss-of-function, pharmacological ROCK inhibition\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo biosensor imaging with genetic loss-of-function and pharmacological rescue; direct visualization of Rho activity pattern\",\n      \"pmids\": [\"23804498\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"IGFBP-5(201–218) stimulation of mesangial cells caused rapid aggregation of Cdc42GAP (ARHGAP1) as detected by immunofluorescence, concurrent with filopodia formation and actin reorganization; staurosporin inhibited both migration and Cdc42GAP aggregation only when added in the first hour, suggesting Cdc42GAP aggregation is downstream of an IGFBP-5 receptor serine/threonine kinase.\",\n      \"method\": \"Immunofluorescence microscopy, pharmacological inhibition, wounding assay\",\n      \"journal\": \"Kidney international\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single localization method without mechanistic molecular detail; pharmacological correlation only\",\n      \"pmids\": [\"10792618\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"ARHGAP8, a novel RHOGAP protein, shares identical domain architecture with ARHGAP1/CDC42GAP/p50RHOGAP including a C-terminal RHOGAP domain, a central SH3-binding motif, and an N-terminal BCH/Sec14p-like domain, indicating that ARHGAP1 defines a structural subfamily among RhoGAP proteins.\",\n      \"method\": \"Sequence/domain analysis, genomic organization comparison\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — bioinformatics/structural classification only, no functional experiment on ARHGAP1 itself\",\n      \"pmids\": [\"15225876\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ARHGAP1 (p50RhoGAP/Cdc42GAP) is a ubiquitously expressed RhoGAP whose crystal structures in complex with Cdc42 define its catalytic mechanism: the arginine finger (Arg305) stabilizes the GTP hydrolysis transition state while Cdc42 switch I and II regions dock into a conserved surface pocket; ARHGAP1 has a strong enzymatic preference for Cdc42 as a substrate but also stimulates RhoA and Rac GTP hydrolysis; its activity is spatially regulated at the cell leading edge by Nudel (which competes with Cdc42 for ARHGAP1 binding), by reactive oxygen species downstream of NADPH oxidase, and intramolecularly by its N-terminal BCH/Sec14-like domain (which sequesters RhoA from the adjacent GAP domain); the Sec14-like domain also targets ARHGAP1 to endosomal membranes where it forms a complex with Rab11; genetic knockout in mice and fibroblasts establishes that ARHGAP1 controls Cdc42 activity to regulate filopodia formation, cell polarity, directional migration, hematopoietic stem cell survival and engraftment, perinatal body growth via the Cdc42-JNK apoptosis axis, and smooth muscle contraction through the Cdc42-PAK-vimentin pathway; in neural crest cells, ARHGAP1 restricts active Rho to the cell apex to enable apical detachment during EMT.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ARHGAP1 (p50RhoGAP/Cdc42GAP) is a ubiquitously expressed Rho-family GTPase-activating protein that terminates Cdc42/Rho signaling to control actin-dependent processes including filopodia formation, cell polarity, directional migration, and apoptotic survival [#4, #7]. Crystal structures of its GAP domain bound to Cdc42 establish the catalytic mechanism: the protein contributes an arginine finger (Arg305) that stabilizes the GTP-hydrolysis transition state while clamping the switch I and switch II regions of the bound GTPase, with the R305A (and equivalently R282A/R85) mutant abolishing catalysis [#0, #2, #15]. Biochemically, ARHGAP1 binds Rho, Rac, and Cdc42 comparably but strongly prefers Cdc42 as a substrate for hydrolysis stimulation while also accelerating RhoA GTP hydrolysis several-thousand-fold [#3, #4, #5]. Its activity is spatially and intramolecularly tuned through its N-terminal BCH/Sec14-like domain, which sequesters RhoA in cis to suppress the adjacent GAP domain and which targets the protein to endosomal membranes in a complex with Rab11 [#15, #6]; the BCH domain also mediates competitive interactions with BNIP-2 and BNIP-Sα that displace ARHGAP1 from Cdc42 or RhoA [#13, #16]. At the migrating leading edge, Nudel competes with Cdc42 for ARHGAP1 binding to sustain local Cdc42 activation, and ROS generated by NADPH oxidase (p47phox) suppress ARHGAP1 activity downstream of agonist stimulation [#10, #12]. Gene knockout in mice and fibroblasts produces Cdc42 gain-of-function, demonstrating that ARHGAP1 governs filopodia and polarity in fibroblasts, hematopoietic stem/progenitor survival via the Cdc42-JNK apoptosis axis, perinatal body growth, and smooth muscle contraction through a Cdc42-PAK-vimentin pathway [#7, #8, #9, #11]. In vivo, ARHGAP1 spatially restricts active Rho to the apex of premigratory neural crest cells to permit apical detachment during EMT [#17].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"Established the basic identity and biochemical activity of ARHGAP1, answering whether the 50 kDa protein was a general RhoGAP or one with substrate selectivity.\",\n      \"evidence\": \"Protein purification, cDNA cloning, and in vitro GTPase/binding assays of human p50rhoGAP\",\n      \"pmids\": [\"8288572\", \"8262058\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Substrate preference defined biochemically but cellular significance unresolved\", \"Structural basis of selectivity unknown\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Resolved the catalytic mechanism by defining how ARHGAP1 accelerates GTP hydrolysis, addressing how a GAP enhances an intrinsically slow GTPase.\",\n      \"evidence\": \"X-ray crystallography of isolated GAP domain and of Cdc42-GAP transition-state mimic complexes with R305A mutagenesis, plus quantitative RhoA kinetics\",\n      \"pmids\": [\"9009196\", \"9262406\", \"9846874\", \"9548756\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structures use isolated GAP domain, not full-length protein\", \"Does not address intramolecular or spatial regulation in cells\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Identified the BCH domain as a protein-protein interaction module that competes for Cdc42/RhoA, raising the question of how RTK and adaptor signals feed into ARHGAP1 regulation.\",\n      \"evidence\": \"Yeast two-hybrid, GST pulldown, co-IP, in vitro phosphorylation and GTPase assays with BNIP-2 and FGFR1\",\n      \"pmids\": [\"10954711\", \"10551883\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of BNIP-2 competition in cells not established\", \"Single-lab interaction data\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrated in vivo physiological roles via genetic knockout, answering what cellular and organismal processes ARHGAP1-controlled Cdc42 activity governs.\",\n      \"evidence\": \"Cdc42GAP knockout mice and MEFs with GTPase, migration, apoptosis, hematopoietic reconstitution, and JNK pathway readouts\",\n      \"pmids\": [\"16914516\", \"16174757\", \"16157885\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Knockout is a Cdc42 gain-of-function model; does not isolate Rho/Rac contributions\", \"Tissue-specific mechanisms partly inferred\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Linked ARHGAP1 to membrane trafficking by showing Sec14-like domain targeting to endosomes and Rab11 complex formation, addressing where in the cell it acts.\",\n      \"evidence\": \"Subcellular fractionation, transferrin uptake assay, colocalization, and BRET\",\n      \"pmids\": [\"16380373\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab data; reciprocal validation limited\", \"Functional consequence of Rab11 complex on Rho signaling not fully defined\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Resolved how ARHGAP1 activity is autoregulated by showing the BCH domain sequesters RhoA in cis from the adjacent GAP domain, explaining substrate gating within the protein.\",\n      \"evidence\": \"Domain deletion, site-directed mutagenesis, RhoA pulldown, and cell morphology assays\",\n      \"pmids\": [\"20660160\", \"16331259\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural model of the closed/open intramolecular state lacking\", \"Signals that relieve BCH autoinhibition in vivo unclear\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Defined spatial and signal-dependent regulation at the leading edge and in smooth muscle, answering how local GAP activity is dynamically modulated by upstream signals.\",\n      \"evidence\": \"Nudel competition Co-IP/RNAi with Cdc42 activity readouts; ROS/p47phox-dependent suppression of GAP activity with PAK-vimentin-contraction readouts\",\n      \"pmids\": [\"18331715\", \"19494238\", \"19812368\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular target of ROS on ARHGAP1 (oxidized residue) not identified\", \"Crosstalk between Nudel and ROS regulation not integrated\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Showed in vivo spatial control of Rho during morphogenesis, establishing ARHGAP1 as a positional regulator of GTPase activity during EMT.\",\n      \"evidence\": \"Zebrafish FRET Rho biosensor imaging with morpholino loss-of-function and ROCK pharmacology in neural crest cells\",\n      \"pmids\": [\"23804498\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism localizing ARHGAP1 to the apical domain unknown\", \"Relationship to mammalian roles not directly tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the distinct regulatory inputs (BCH autoinhibition, Nudel sequestration, ROS oxidation, Rab11 endosomal targeting) are integrated to produce substrate- and location-specific GTPase inactivation in vivo remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No full-length structure capturing autoinhibited vs active states\", \"Direct ROS-modified residue unidentified\", \"Integration of competing regulators at a single subcellular site untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 2, 3, 4, 5, 15]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [2, 5, 11]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [10]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [7, 8, 9, 11]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [8, 9]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"CDC42\", \"RHOA\", \"RAC1\", \"RAB11\", \"NDEL1\", \"BNIP2\", \"BNIPSA\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}