{"gene":"ASAP1","run_date":"2026-04-28T17:12:37","timeline":{"discoveries":[{"year":1998,"finding":"ASAP1 is a PIP2-dependent Arf GTPase-activating protein (GAP) with activity on Arf1 and Arf5 (less on Arf6, none on Arl2) in vitro. It contains PH, zinc finger, and ANK repeat domains that together confer PIP2-dependent GAP activity. ASAP1 associates with SH3 domains of Src family members and the Crk adapter protein via a proline-rich class II Src SH3 binding site, and is phosphorylated on tyrosine residues in cells expressing activated Src.","method":"Protein purification, in vitro GAP assay, GST pulldown, co-immunoprecipitation, tyrosine phosphorylation in cells with activated Src","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution of GAP activity, multiple binding interactions confirmed by orthogonal methods, foundational paper >200 citations","pmids":["9819391"],"is_preprint":false},{"year":2000,"finding":"ASAP1 localizes to focal adhesions and cycles with focal adhesion proteins during cell migration. Overexpression of wild-type ASAP1 alters focal adhesion morphology and blocks cell spreading and dorsal ruffle formation induced by PDGF, while a GAP-inactive mutant has reduced effect on spreading and increases dorsal ruffle formation, indicating ASAP1 regulates cytoskeletal remodeling through its GAP activity.","method":"Fluorescence microscopy, overexpression of wild-type and GAP-inactive mutants, cell spreading and dorsal ruffle assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — clean localization with functional consequence, mutant analysis, replicated findings, >180 citations","pmids":["10725410"],"is_preprint":false},{"year":2001,"finding":"DEF-1/ASAP1 functions as a GAP for ARF1 but not ARF6 in vivo (cell-based ARF GAP assay), distinguishing its substrate specificity from other ARF GAPs. Stable expression of DEF-1 enhances cell migration in a GAP-activity-dependent manner, while inhibition of cell spreading is GAP-activity-independent, indicating DEF-1 modulates motility and spreading through different pathways.","method":"Cell-based ARF GAP assay, stable cell line generation, chemotaxis/motility assays, GAP-domain deletion mutant analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — cell-based substrate specificity assay with multiple ARF GAPs compared, functional dissection with mutants, replicated across orthogonal readouts","pmids":["11773070"],"is_preprint":false},{"year":2002,"finding":"ASAP1 directly binds focal adhesion kinase (FAK) via an interaction between the C-terminal SH3 domain of ASAP1 and the second proline-rich motif in the C-terminal region of FAK. This interaction contributes to focal adhesion assembly: overexpression of wild-type ASAP1 inhibits cell spreading and prevents efficient organization of paxillin and FAK in focal adhesions, while a FAK-binding-deficient ASAP1 truncation or GAP-inactive variant has less pronounced effects.","method":"Affinity chromatography, yeast two-hybrid, GST pulldown, co-immunoprecipitation, cell spreading assays, fluorescence microscopy","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — reciprocal co-IP and pulldown confirming interaction, multiple orthogonal methods, functional readout with domain mutants, >140 citations","pmids":["12058076"],"is_preprint":false},{"year":2003,"finding":"CrkL binds ASAP1 and directs its localization to peripheral focal adhesions. In spreading platelets, endogenous ASAP1 localizes at peripheral focal adhesions. Co-expression of wild-type CrkL (but not an SH2-mutated CrkL that cannot localize at focal adhesions) recruits ASAP1 to CrkL-induced focal adhesions, indicating CrkL links ASAP1 to focal adhesions via CrkL's SH2 domain-dependent focal adhesion targeting.","method":"Pulldown with mass spectrometry identification, co-immunoprecipitation, overexpression in COS7 cells, fluorescence microscopy","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — MS identification validated by co-IP, localization linked to functional consequence via SH2 mutant, single lab","pmids":["12522101"],"is_preprint":false},{"year":2006,"finding":"The N-terminal BAR domain of ASAP1, together with the PH domain, dimerizes to form an extended structure that binds large unilamellar vesicles containing acidic phospholipids and bends vesicle membranes to form tubular structures in vitro. This membrane-bending activity is regulated by Arf1-GTP binding to the ArfGAP domain. In cells, ASAP1 BAR domain-containing mutants induced tubular structures containing EGFR and Rab11, and ASAP1 colocalized with EGFR during receptor recycling; expression of ASAP1 accelerated EGFR trafficking and slowed cell spreading in a BAR-domain-dependent manner.","method":"Recombinant protein biophysics, large unilamellar vesicle (LUV) binding and tubulation assays, electron microscopy, live-cell fluorescence microscopy, EGFR trafficking assays","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 1 — reconstituted membrane bending in vitro with structural EM validation, confirmed in cells with mechanistic mutants, multiple orthogonal methods","pmids":["16431365"],"is_preprint":false},{"year":2007,"finding":"Both ASAP1a and ASAP1b splice variants associate with invadopodia and podosomes. Reduction of ASAP1 by siRNA blocks formation of invadopodia and podosomes. Podosome formation requires ASAP1's BAR domain, SH3 domain, and Src phosphorylation site, but not the Src binding site or GAP activity per se. ASAP1 is thus a critical downstream target of tyrosine kinase signaling (Src) in podosome and invadopodium assembly, functioning as a potential coincidence detector of SH3-domain protein association and Src phosphorylation.","method":"siRNA knockdown, recombinant mutant rescue, fluorescence microscopy, live-cell FRAP","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — siRNA loss-of-function with defined phenotype, systematic mutant dissection of domains, replicated across invadopodia and podosomes","pmids":["17893324"],"is_preprint":false},{"year":2007,"finding":"ASAP1 uses Arf1-GTP as a substrate with a kcat of ~57 s⁻¹ and Km of ~2.2 μM (steady-state), forming a binary Arf1-GTP–ASAP1 complex that is stabilized by AlF4⁻. Arg-497 is the catalytic arginine finger (mutations reduce kcat >> Km). Mutations in residues Trp-479, Ile-490, Arg-505, Leu-511, and Asp-512 also primarily affect kcat rather than Km, suggesting a conformational transition to the catalytically active state. ASAP1 mutants lacking activity in vitro also lack activity in a dorsal ruffle cell-based assay.","method":"Steady-state and single-turnover kinetics with LUVs, AlF4⁻ stabilization, site-directed mutagenesis, in vivo dorsal ruffle assay","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 — rigorous kinetic characterization with mutagenesis, in vitro and in vivo correlation, defines catalytic mechanism","pmids":["17112341"],"is_preprint":false},{"year":2008,"finding":"The BAR domain of ASAP1 autoinhibits GAP activity through intraprotein interactions. The BAR-PZA protein has greater Km and smaller kcat than PZA (PH-ArfGAP-Ank) alone on LUV surfaces. This effect depends on the N-terminal loop of the BAR domain and is not due to differential membrane association or changes in vesicle curvature, suggesting the BAR domain modulates the catalytic mechanism of the adjacent PH and GAP domains.","method":"Recombinant protein LUV-based kinetic assays, BAR domain loop deletion mutants, analytical ultracentrifugation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro enzymatic assay with saturation kinetics and single-turnover kinetics, mechanistic mutagenesis of BAR loop","pmids":["19017632"],"is_preprint":false},{"year":2008,"finding":"NMR spectroscopy and biochemical analysis reveal that the PH domain of ASAP1 dynamically interacts with the ArfGAP and ankyrin repeat domains. The PH-ArfGAP domain interaction partially occludes the PIP2 binding site in the soluble protein, but the PIP2 binding site is accessible when ASAP1 is membrane-bound. PIP2 binding alters PH domain conformation; mutations in the PH domain loop contacting the ArfGAP domain affect PIP2 binding and both Km and kcat for Arf1-GTP hydrolysis.","method":"NMR spectroscopy, analytical ultracentrifugation, PIP2 binding assay, GAP activity kinetics with point mutants","journal":"Cellular signalling","confidence":"High","confidence_rationale":"Tier 1 — NMR structural analysis combined with kinetics and mutagenesis, defines allosteric PH-ArfGAP interdomain regulation","pmids":["18675341"],"is_preprint":false},{"year":2011,"finding":"GEFH1, a RhoA guanine nucleotide exchange factor, binds the BAR domain of ASAP1. Endogenous GEFH1 co-immunoprecipitates with ASAP1 and colocalizes with ASAP1 in podosomes. Overexpression of GEFH1 inhibits podosome assembly and ASAP1 GAP catalytic activity; a GEFH1 mutant lacking the BAR-domain binding region is less effective. siRNA knockdown of GEFH1 does not affect matrix degradation but increases the rate of podosome assembly. GEFH1 is therefore a negative regulator of podosomes acting via ASAP1.","method":"Yeast two-hybrid screening, co-immunoprecipitation, fluorescence microscopy, overexpression and siRNA knockdown, GAP activity assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — endogenous co-IP validated, loss/gain-of-function with defined phenotype, single lab","pmids":["21352810"],"is_preprint":false},{"year":2012,"finding":"The Arf GAP ASAP1 serves as a scaffold for ciliary receptor targeting of rhodopsin. ASAP1 brings together Arf4 (GTP-bound), Rab11, Rab8, and the Rab8-GEF Rabin8 into a complex. Ablation of ASAP1 abolishes ciliary targeting and causes formation of actin-rich periciliary membrane projections with mislocalized rhodopsin. ASAP1 recognizes the FR ciliary targeting signal of rhodopsin; the rhodopsin FR→AA mutant fails to interact with Rab8 and fails to cross the periciliary diffusion barrier.","method":"siRNA/shRNA ablation, co-immunoprecipitation, fluorescence and electron microscopy, ciliary targeting assays, ciliary signal mutant analysis","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 — ablation with defined phenotype, complex reconstitution by co-IP, signal motif mutagenesis validated functionally, replicated across methods","pmids":["22983554"],"is_preprint":false},{"year":2015,"finding":"The PH domain of ASAP1 binds PtdIns(4,5)P2 at two sites: a canonical (C) site and an atypical (A) site. Structures of unliganded and dibutyryl-PtdIns(4,5)P2-bound PH domain were solved. PtdIns(4,5)P2 dependence of LUV binding and GAP activity is sigmoidal (cooperative), and mutations in either the C or A site reduce both PIP2-dependent vesicle binding and GAP activity, supporting a cooperative two-site PIP2 binding mechanism that enables rapid switching of ASAP1 activity.","method":"X-ray crystallography, LUV binding assays, GAP activity assays, site-directed mutagenesis, comparison with PLC-δ1 PH domain","journal":"Structure (London, England : 1993)","confidence":"High","confidence_rationale":"Tier 1 — crystal structures of both apo and ligand-bound forms, mutagenesis validated against biochemical assays, multiple orthogonal methods","pmids":["26365802"],"is_preprint":false},{"year":2015,"finding":"FIP3 (RAB11FIP3), an Arf and Rab11 effector, promotes the activity of Rab11a and ASAP1 in Arf4-dependent ciliary transport of rhodopsin. FIP3 competes with rhodopsin for binding to ASAP1 and displaces rhodopsin from the ternary Arf4-GTP–ASAP1 complex. FIP3 also coordinates ASAP1 and Rab11a interactions with Rabin8, facilitating the Rab11-Rabin8-Rab8 cascade assembly for ciliary receptor trafficking.","method":"Co-immunoprecipitation, competition binding assays, siRNA ablation with ciliary targeting readout, fluorescence microscopy","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — multiple co-IPs, competition binding, ablation with defined phenotype, mechanistic dissection of complex assembly","pmids":["25673879"],"is_preprint":false},{"year":2015,"finding":"ASAP1 knockdown in mouse mammary gland leads to a marked increase in repopulating activity in vivo, indicating ASAP1 acts as a negative regulator of mammary stem cell activity.","method":"Pooled shRNA screen in primary mammary cells, in vivo transplantation assay, RNA-seq expression profiling","journal":"BMC cancer","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo KD with specific quantitative readout (repopulating activity), single lab with functional validation","pmids":["25879659"],"is_preprint":false},{"year":2015,"finding":"ASAP1-depleted dendritic cells show impaired matrix degradation and migration, and rs10956514 is associated with the level of reduction of ASAP1 expression after M. tuberculosis infection. ASAP1 is highly expressed in dendritic cells and involved in podosome formation and actin/membrane remodeling; its depletion impairs DC migration in the context of TB susceptibility.","method":"siRNA knockdown of ASAP1 in DCs, matrix degradation assay, migration assay, eQTL analysis linking SNP to ASAP1 expression","journal":"Nature genetics","confidence":"Medium","confidence_rationale":"Tier 2 — direct KD with defined cellular phenotype (migration, matrix degradation), functionally linked to genetic variant, single experimental approach","pmids":["25774636"],"is_preprint":false},{"year":2016,"finding":"ASAP1 directly binds nonmuscle myosin 2A (NM2A) through the BAR-PH tandem domain in vitro, and ASAP1 and NM2A co-immunoprecipitate and colocalize in cells. Knockdown of ASAP1 reduces colocalization of NM2A and F-actin. ASAP1 and NM2A knockdowns recapitulate each other's effects on focal adhesions, cell migration, cell spreading, and circular dorsal ruffles (CDRs). Exogenous NM2A rescues ASAP1 knockdown effects on CDRs but not vice versa, indicating ASAP1 is a positive regulator of NM2A.","method":"In vitro binding assay, co-immunoprecipitation, siRNA knockdown, fluorescence microscopy, functional assays (spreading, migration, CDRs)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — in vitro direct binding confirmed by reciprocal co-IP, symmetrical KD phenotypes, rescue experiment, multiple orthogonal assays","pmids":["26893376"],"is_preprint":false},{"year":2019,"finding":"Loss of ASAP1 in mice leads to defects in adipogenic and osteogenic differentiation of mesenchymal progenitor cells. Mechanistically, FAK/Src and PI3K/AKT signaling are compromised in Asap1GT/GT MEFs, leading to impaired adipogenic and osteogenic differentiation, while chondrogenic differentiation is accelerated.","method":"Gene-trap mouse model, in vivo histology, in vitro differentiation assays, kinase signaling analysis","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 — genetic KO with defined in vivo and in vitro differentiation phenotypes, signaling pathway analysis, single lab study","pmids":["31246957"],"is_preprint":false},{"year":2019,"finding":"The N-BAR domain of ASAP1 directly controls actin stress fiber organization. ASAP1 depletion causes defects in stress fiber organization while overexpression enhances actin remodeling; the BAR-PH fragment is sufficient for this effect. The BAR-PH tandem of ASAP1 directly binds and bundles actin filaments in vitro; the ArfGAP and C-terminal SH3 domains reduce filament binding and bundling by the BAR-PH domain.","method":"siRNA knockdown, overexpression, actin cosedimentation/bundling assays, fluorescence microscopy","journal":"iScience","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution of direct actin binding and bundling, combined with cell-based KD/OE with domain dissection","pmids":["31785555"],"is_preprint":false},{"year":2019,"finding":"PIP2 regulates binding of the ASAP1 PH domain to the N-terminal extension (residues 2–17) of ARF1, thereby contributing to GAP activity regulation. Without the ARF1 N-terminus, PIP2 has little effect on ASAP1 GAP activity. A peptide comprising residues 2–17 of ARF1 inhibits GAP activity and binds PIP2-dependently to the PH domain and a 17-amino-acid interdomain linker. Mutations reducing ARF1 N-terminal binding to the PH domain also reduce GAP activity and ASAP1-driven cellular actin remodeling.","method":"In vitro GAP assay with truncated ARF1 variants and peptides, PH domain binding assays, site-directed mutagenesis, actin remodeling cell assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro biochemical reconstitution with multiple ARF1 variants, mutagenesis of interaction interface, correlated with in vivo actin remodeling readout","pmids":["31591270"],"is_preprint":false},{"year":2020,"finding":"The N-BAR domain of ASAP1 directly binds F-actin, promotes formation of predominantly unipolar actin bundles, and stabilizes them against depolymerization. ASAP1 homodimerization aligns F-actin in bundles. The ASAP1 N-BAR domain moderately reduces spontaneous G-actin polymerization. Overexpression of the BAR-PH tandem in fibroblasts induces actin-filled cellular projections more effectively than full-length ASAP1; an ASAP1 construct lacking the N-BAR domain fails to induce projections.","method":"Actin cosedimentation, polymerization and depolymerization assays, TIRF microscopy, confocal microscopy, electron microscopy, cell overexpression","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — multiple in vitro actin binding/bundling assays with EM validation, cell-based functional assays, domain deletion analysis","pmids":["32444496"],"is_preprint":false},{"year":2020,"finding":"Binding of multiple PIP2 molecules to the ASAP1 PH domain triggers an allosteric conformational switch and maintains the PH domain in a well-defined orientation at the membrane, allowing critical contacts with Arf1 to occur. NMR, neutron reflectometry, and molecular dynamics simulations together define how PH domain membrane binding positions ASAP1 for optimal Arf1 interaction and GTP hydrolysis.","method":"Solution NMR, neutron reflectometry, molecular dynamics simulation, reconstituted membrane-binding assays","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1 — multiple structural and biophysical methods (NMR, neutron reflectometry, MD) in a single study with functional implication for catalysis","pmids":["32998886"],"is_preprint":false},{"year":2004,"finding":"The N-terminal extension (amino acids 2–17) of Arf1 is a critical structural determinant for interaction with ASAP1, AGAP1, and Arf GAP1, though each GAP has a unique interface. Deletion of residues 2–17 reduces ASAP1 interaction by 200-fold and residues 2–17 bind directly to ASAP1. Lysines 15 and 16 contribute more to ASAP1/AGAP1 interaction than to Arf GAP1 interaction; Leu-8 distinguishes Arf GAP1 binding from ASAP1/AGAP1.","method":"GAP activity assay with Arf1 deletion and point mutants, antibody sequestration, direct peptide binding assay","journal":"Cellular signalling","confidence":"High","confidence_rationale":"Tier 1 — in vitro enzymatic assays with multiple Arf1 mutants, direct binding confirmed, defines substrate recognition interface","pmids":["15212764"],"is_preprint":false},{"year":2023,"finding":"Myr-Arf1 (active, membrane-anchored GTP form) exists in dynamic equilibrium between membrane-associated and membrane-distal G-domain conformations on lipid bilayers. The PH domain of ASAP1 restricts Arf1 G-domain motions and locks it in a conformation that exposes functionally relevant regions for GAP-catalyzed GTP hydrolysis.","method":"NMR, neutron reflectometry, molecular dynamics simulation of membrane-anchored Arf1 in complex with ASAP1 PH domain","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 — multiple orthogonal structural/biophysical methods defining dynamic conformational landscape with functional implications","pmids":["37989735"],"is_preprint":false},{"year":2023,"finding":"ASAP1 inhibits ubiquitin-mediated proteasomal degradation of IQGAP1, thereby enhancing CDC42 activity. Activated CDC42 upregulates the EGFR-MAPK pathway, promoting chemotherapy resistance in gastric cancer cells.","method":"Co-immunoprecipitation, ubiquitination assay, siRNA knockdown, overexpression in cell lines, in vivo xenograft","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 — mechanistic pathway dissection with co-IP and functional assays, single lab, novel downstream pathway","pmids":["36792578"],"is_preprint":false}],"current_model":"ASAP1 is a multi-domain ArfGAP scaffold protein that catalyzes PIP2-dependent, membrane-surface GTP hydrolysis on Arf1 (and Arf5) through a binary complex mechanism regulated by cooperative PIP2 binding to the PH domain (which allosterically controls catalysis and positions Arf1 via its N-terminal extension), while its N-BAR domain directly bundles F-actin, autoinhibits GAP activity through intraprotein contacts, mediates membrane tubulation, and serves as a binding platform for Src (leading to tyrosine phosphorylation at a site required for podosomes/invadopodia), FAK (regulating focal adhesion assembly), CrkL (directing peripheral focal adhesion targeting), NM2A (actomyosin network remodeling), GEFH1 (negative regulator of podosomes), and components of the ciliary receptor targeting machinery (Arf4, Rab11, Rabin8, FIP3), thereby coordinately linking membrane remodeling, actin cytoskeletal dynamics, cell migration, and sensory receptor trafficking to primary cilia."},"narrative":{"teleology":[{"year":1998,"claim":"Establishing ASAP1 as a PIP2-dependent ArfGAP with Src-family and Crk interactions defined its molecular identity and placed it at the intersection of Arf signaling, phosphoinositide regulation, and tyrosine-kinase pathways.","evidence":"In vitro GAP assay with purified protein, GST pulldown and co-IP for Src/Crk binding, tyrosine phosphorylation in activated-Src cells","pmids":["9819391"],"confidence":"High","gaps":["Physiological substrates among Arf isoforms in cells not determined","Tyrosine phosphorylation site identity and functional consequence unknown","No structural information on multi-domain architecture"]},{"year":2001,"claim":"Demonstration that ASAP1 localizes to focal adhesions, regulates cell spreading and migration in a GAP-activity-dependent manner, and acts on Arf1 (not Arf6) in cells connected its enzymatic specificity to cytoskeletal remodeling phenotypes.","evidence":"Fluorescence microscopy, overexpression of WT and GAP-inactive mutants, cell-based ARF GAP assay, chemotaxis assays","pmids":["10725410","11773070"],"confidence":"High","gaps":["Mechanism linking Arf1 GTP hydrolysis to focal adhesion dynamics unknown","Contribution of non-catalytic domains not dissected"]},{"year":2003,"claim":"Identification of direct FAK and CrkL interactions mapped how ASAP1 is recruited to focal adhesions and linked its scaffold function to focal adhesion assembly independent of catalysis.","evidence":"Yeast two-hybrid, reciprocal co-IP, GST pulldown, SH3/SH2-domain mutant analysis, cell spreading assays","pmids":["12058076","12522101"],"confidence":"High","gaps":["Whether FAK phosphorylates ASAP1 and its consequence unknown","CrkL–ASAP1 interaction validated in a single lab"]},{"year":2004,"claim":"Defining the Arf1 N-terminal extension (residues 2–17) as a critical substrate-recognition determinant for ASAP1 resolved how ASAP1 discriminates among Arf family members.","evidence":"In vitro GAP assay with Arf1 deletion/point mutants, direct peptide binding","pmids":["15212764"],"confidence":"High","gaps":["Structural basis of the N-terminus–ASAP1 interface not resolved at atomic level","How this recognition interface operates on membrane surfaces unknown"]},{"year":2006,"claim":"Discovery that the BAR domain dimerizes, tubulates membranes, and promotes EGFR recycling established ASAP1 as a membrane-bending protein linking Arf signaling to receptor trafficking.","evidence":"Recombinant BAR-PH biophysics, LUV tubulation with EM, EGFR trafficking assays in cells","pmids":["16431365"],"confidence":"High","gaps":["Endogenous role in EGFR trafficking not confirmed by loss-of-function","How Arf1-GTP binding regulates BAR-mediated tubulation structurally unresolved"]},{"year":2007,"claim":"Kinetic characterization identified Arg-497 as the catalytic arginine finger and established a conformational-transition mechanism for GAP-catalyzed GTP hydrolysis, while siRNA experiments showed ASAP1 is required for podosome/invadopodium formation via Src phosphorylation and the BAR/SH3 domains rather than GAP activity alone.","evidence":"Steady-state and single-turnover kinetics with mutagenesis; siRNA knockdown and systematic domain-mutant rescue in podosome/invadopodium assays","pmids":["17112341","17893324"],"confidence":"High","gaps":["Identity of the Src phosphorylation site critical for podosomes not mapped","How BAR and SH3 domains cooperate in podosome nucleation mechanistically unclear"]},{"year":2008,"claim":"NMR and kinetic analyses revealed that the BAR domain autoinhibits GAP activity via its N-terminal loop and that the PH domain allosterically communicates PIP2 binding to the ArfGAP domain, establishing a multi-layered intramolecular regulatory mechanism.","evidence":"NMR spectroscopy of PH–ArfGAP interdomain contacts, LUV-based kinetics with BAR-loop and PH-domain mutants","pmids":["19017632","18675341"],"confidence":"High","gaps":["Full-length ASAP1 structure not available","How autoinhibition is relieved by physiological signals undefined"]},{"year":2011,"claim":"Identification of GEFH1 as a BAR-domain-binding negative regulator of podosomes through ASAP1 added a RhoA-GEF input to the ASAP1 signaling nexus at podosomes.","evidence":"Yeast two-hybrid, endogenous co-IP, overexpression and siRNA with podosome/GAP readouts","pmids":["21352810"],"confidence":"Medium","gaps":["Whether GEFH1 activates RhoA locally at podosomes through ASAP1 not tested","GEFH1–ASAP1 interaction confirmed in single lab"]},{"year":2012,"claim":"Demonstrating that ASAP1 scaffolds an Arf4–Rab11–Rabin8–Rab8 complex for rhodopsin ciliary targeting revealed a non-cytoskeletal function: coordinating the Arf-to-Rab cascade at the base of primary cilia.","evidence":"siRNA/shRNA ablation with ciliary targeting readout, co-IP of multi-protein complex, FR motif mutagenesis","pmids":["22983554"],"confidence":"High","gaps":["Whether ASAP1 GAP activity is required for ciliary targeting not resolved","Generalizability to other ciliary cargo beyond rhodopsin not established"]},{"year":2015,"claim":"Crystal structures of the PH domain with and without PtdIns(4,5)P2, combined with mutagenesis, established a cooperative two-site PIP2 binding mechanism enabling switch-like regulation of GAP activity, while FIP3 was shown to coordinate ASAP1 and Rab11a in ciliary transport.","evidence":"X-ray crystallography of apo and PIP2-bound PH domain, LUV binding/GAP assays with C/A-site mutants; co-IP and competition binding for FIP3","pmids":["26365802","25673879"],"confidence":"High","gaps":["Full kinetic model of cooperativity with membrane-reconstituted protein lacking","FIP3 competition mechanism not structurally resolved"]},{"year":2016,"claim":"Direct binding of NM2A to the BAR-PH tandem and reciprocal knockdown phenocopy established ASAP1 as a positive regulator of actomyosin contractility at focal adhesions and circular dorsal ruffles.","evidence":"In vitro binding, reciprocal co-IP, siRNA KD phenocopy, NM2A rescue of ASAP1-KD CDR defect","pmids":["26893376"],"confidence":"High","gaps":["Whether NM2A binding competes with actin bundling by the BAR domain not tested","Structural basis of BAR-PH–NM2A interaction unknown"]},{"year":2019,"claim":"Reconstitution showed the N-BAR domain directly binds and bundles F-actin and that PIP2-dependent PH domain interaction with the Arf1 N-terminal extension is a key determinant of GAP regulation, unifying the actin-remodeling and catalytic functions in a single mechanistic framework.","evidence":"Actin cosedimentation/bundling, TIRF, EM; GAP assays with N-terminally truncated Arf1 and PH-domain mutants","pmids":["31785555","31591270"],"confidence":"High","gaps":["How simultaneous actin bundling and membrane tubulation are coordinated unclear","Relative contributions of actin bundling vs. GAP activity to cell migration not separated"]},{"year":2020,"claim":"Biophysical studies revealed that cooperative PIP2 binding orients the PH domain at the membrane surface, and the PH domain in turn locks membrane-anchored Arf1 in a conformation competent for GTP hydrolysis, completing a structural model of allosteric catalytic activation.","evidence":"NMR, neutron reflectometry, MD simulations of PH domain–membrane and Arf1–membrane complexes","pmids":["32998886","37989735"],"confidence":"High","gaps":["Full-length ASAP1 on membranes not yet visualized structurally","How BAR-domain autoinhibition integrates with PH-domain membrane orientation unknown"]},{"year":2023,"claim":"A novel non-GAP function was described in which ASAP1 stabilizes IQGAP1 by inhibiting its ubiquitin-mediated degradation, thereby activating CDC42 and EGFR-MAPK signaling in cancer cells.","evidence":"Co-IP, ubiquitination assay, siRNA/overexpression, xenograft","pmids":["36792578"],"confidence":"Medium","gaps":["Whether ASAP1 directly deubiquitinates IQGAP1 or prevents ubiquitin ligase access not distinguished","Single lab, not independently replicated","Relevance beyond gastric cancer unclear"]},{"year":null,"claim":"A full-length ASAP1 structure on membranes that explains how BAR-mediated autoinhibition, PIP2-driven allosteric activation, actin bundling, and scaffold interactions are coordinated spatiotemporally remains unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No full-length atomic structure of ASAP1","Mechanism by which Src phosphorylation relieves autoinhibition and promotes podosomes not structurally defined","How ASAP1 partitions between focal adhesion, podosome, and ciliary functions in a single cell unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003924","term_label":"GTPase activity","supporting_discovery_ids":[0,2,7,8,12,19]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,7,8]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[8,10,24]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[18,20]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[5,12,21]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[3,4,11,16]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,5,12,21]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[1,6,18,20]},{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[11,13]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,9]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,2,7,11,24]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[5,11,13]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[11,13]},{"term_id":"R-HSA-1500931","term_label":"Cell-Cell communication","supporting_discovery_ids":[1,3,6]}],"complexes":[],"partners":["ARF1","FAK","CRKL","MYH9","GEFH1","ARF4","RAB11A","FIP3"],"other_free_text":[]},"mechanistic_narrative":"ASAP1 is a multi-domain ArfGAP scaffold protein that integrates membrane remodeling, actin cytoskeletal dynamics, and vesicular trafficking through its enzymatic and structural activities. Its PH domain cooperatively binds PtdIns(4,5)P2 at two sites, allosterically positioning membrane-anchored Arf1-GTP for catalytic GTP hydrolysis via the arginine finger Arg-497, with the N-BAR domain exerting autoinhibitory control over GAP activity through intramolecular contacts [PMID:26365802, PMID:17112341, PMID:19017632, PMID:37989735]. The N-BAR domain additionally binds and bundles F-actin directly, tubulates membranes, and serves as a binding platform for NM2A and GEFH1, while the C-terminal SH3 domain recruits FAK and CrkL to focal adhesions; Src-mediated tyrosine phosphorylation and these scaffolding interactions are required for podosome/invadopodium formation, cell spreading, and migration [PMID:32444496, PMID:17893324, PMID:12058076, PMID:26893376]. ASAP1 also scaffolds an Arf4–Rab11–FIP3–Rabin8–Rab8 complex that targets rhodopsin and other sensory receptors to primary cilia, and its loss abolishes ciliary receptor trafficking [PMID:22983554, PMID:25673879]."},"prefetch_data":{"uniprot":{"accession":"Q9ULH1","full_name":"Arf-GAP with SH3 domain, ANK repeat and PH domain-containing protein 1","aliases":["130 kDa phosphatidylinositol 4,5-bisphosphate-dependent ARF1 GTPase-activating protein","ADP-ribosylation factor-directed GTPase-activating protein 1","ARF GTPase-activating protein 1","Development and differentiation-enhancing factor 1","DEF-1","Differentiation-enhancing factor 1","PIP2-dependent ARF1 GAP"],"length_aa":1129,"mass_kda":125.5,"function":"Possesses phosphatidylinositol 4,5-bisphosphate-dependent GTPase-activating protein activity for ARF1 (ADP ribosylation factor 1) and ARF5 and a lesser activity towards ARF6. May coordinate membrane trafficking with cell growth or actin cytoskeleton remodeling by binding to both SRC and PIP2. May function as a signal transduction protein involved in the differentiation of fibroblasts into adipocytes and possibly other cell types. Part of the ciliary targeting complex containing Rab11, ASAP1, Rabin8/RAB3IP, RAB11FIP3 and ARF4, which direct preciliary vesicle trafficking to mother centriole and ciliogenesis initiation (PubMed:25673879)","subcellular_location":"Cytoplasm; Membrane; Golgi apparatus; Golgi apparatus, trans-Golgi network","url":"https://www.uniprot.org/uniprotkb/Q9ULH1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ASAP1","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/ASAP1","total_profiled":1310},"omim":[{"mim_id":"617413","title":"PRUNE EXOPOLYPHOSPHATASE 1; PRUNE1","url":"https://www.omim.org/entry/617413"},{"mim_id":"608651","title":"ARF GTPase-ACTIVATING PROTEIN WITH GTPase DOMAIN, ANKYRIN REPEAT, AND PLECKSTRIN HOMOLOGY DOMAIN 1; AGAP1","url":"https://www.omim.org/entry/608651"},{"mim_id":"607766","title":"ARF-GAP WITH COILED-COIL, ANKYRIN REPEAT, AND PLECKSTRIN HOMOLOGY DOMAINS 2; ACAP2","url":"https://www.omim.org/entry/607766"},{"mim_id":"607763","title":"ARF-GAP WITH COILED-COIL, ANKYRIN REPEAT, AND PLECKSTRIN HOMOLOGY DOMAINS 1; ACAP1","url":"https://www.omim.org/entry/607763"},{"mim_id":"605953","title":"ARF GTPase-ACTIVATING PROTEIN WITH SH3 DOMAIN, ANKYRIN REPEAT, AND PH DOMAIN 1; ASAP1","url":"https://www.omim.org/entry/605953"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Golgi apparatus","reliability":"Approved"},{"location":"Plasma membrane","reliability":"Approved"},{"location":"Centriolar satellite","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/ASAP1"},"hgnc":{"alias_symbol":["PAP","KIAA1249","ZG14P","CENTB4"],"prev_symbol":["DDEF1"]},"alphafold":{"accession":"Q9ULH1","domains":[{"cath_id":"1.20.1270.60","chopping":"28-275","consensus_level":"high","plddt":91.7106,"start":28,"end":275},{"cath_id":"2.30.29.30","chopping":"322-425","consensus_level":"high","plddt":87.4535,"start":322,"end":425},{"cath_id":"1.10.220.150","chopping":"431-555","consensus_level":"medium","plddt":93.5711,"start":431,"end":555},{"cath_id":"1.25.40.20","chopping":"574-710","consensus_level":"medium","plddt":91.5899,"start":574,"end":710},{"cath_id":"2.30.30.40","chopping":"1072-1128","consensus_level":"high","plddt":90.7461,"start":1072,"end":1128}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9ULH1","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9ULH1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9ULH1-F1-predicted_aligned_error_v6.png","plddt_mean":71.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ASAP1","jax_strain_url":"https://www.jax.org/strain/search?query=ASAP1"},"sequence":{"accession":"Q9ULH1","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9ULH1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9ULH1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9ULH1"}},"corpus_meta":[{"pmid":"22128124","id":"PMC_22128124","title":"Evidence 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A new candidate for neonatal screening of cystic fibrosis.","date":"1994","source":"Comptes rendus de l'Academie des sciences. 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the Susceptibility to Tuberculosis in Chinese Population.","date":"2016","source":"Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/27227929","citation_count":13,"is_preprint":false},{"pmid":"31591270","id":"PMC_31591270","title":"Interaction of the N terminus of ADP-ribosylation factor with the PH domain of the GTPase-activating protein ASAP1 requires phosphatidylinositol 4,5-bisphosphate.","date":"2019","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/31591270","citation_count":13,"is_preprint":false},{"pmid":"30283018","id":"PMC_30283018","title":"Glycerophosphatidylcholine PC(36:1) absence and 3'-phosphoadenylate (pAp) accumulation are hallmarks of the human glioma metabolome.","date":"2018","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/30283018","citation_count":13,"is_preprint":false},{"pmid":"22289690","id":"PMC_22289690","title":"Golgi-resident PAP-specific 3'-phosphatase-coupled sulfotransferase 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It contains PH, zinc finger, and ANK repeat domains that together confer PIP2-dependent GAP activity. ASAP1 associates with SH3 domains of Src family members and the Crk adapter protein via a proline-rich class II Src SH3 binding site, and is phosphorylated on tyrosine residues in cells expressing activated Src.\",\n      \"method\": \"Protein purification, in vitro GAP assay, GST pulldown, co-immunoprecipitation, tyrosine phosphorylation in cells with activated Src\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution of GAP activity, multiple binding interactions confirmed by orthogonal methods, foundational paper >200 citations\",\n      \"pmids\": [\"9819391\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"ASAP1 localizes to focal adhesions and cycles with focal adhesion proteins during cell migration. Overexpression of wild-type ASAP1 alters focal adhesion morphology and blocks cell spreading and dorsal ruffle formation induced by PDGF, while a GAP-inactive mutant has reduced effect on spreading and increases dorsal ruffle formation, indicating ASAP1 regulates cytoskeletal remodeling through its GAP activity.\",\n      \"method\": \"Fluorescence microscopy, overexpression of wild-type and GAP-inactive mutants, cell spreading and dorsal ruffle assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean localization with functional consequence, mutant analysis, replicated findings, >180 citations\",\n      \"pmids\": [\"10725410\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"DEF-1/ASAP1 functions as a GAP for ARF1 but not ARF6 in vivo (cell-based ARF GAP assay), distinguishing its substrate specificity from other ARF GAPs. Stable expression of DEF-1 enhances cell migration in a GAP-activity-dependent manner, while inhibition of cell spreading is GAP-activity-independent, indicating DEF-1 modulates motility and spreading through different pathways.\",\n      \"method\": \"Cell-based ARF GAP assay, stable cell line generation, chemotaxis/motility assays, GAP-domain deletion mutant analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-based substrate specificity assay with multiple ARF GAPs compared, functional dissection with mutants, replicated across orthogonal readouts\",\n      \"pmids\": [\"11773070\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"ASAP1 directly binds focal adhesion kinase (FAK) via an interaction between the C-terminal SH3 domain of ASAP1 and the second proline-rich motif in the C-terminal region of FAK. This interaction contributes to focal adhesion assembly: overexpression of wild-type ASAP1 inhibits cell spreading and prevents efficient organization of paxillin and FAK in focal adhesions, while a FAK-binding-deficient ASAP1 truncation or GAP-inactive variant has less pronounced effects.\",\n      \"method\": \"Affinity chromatography, yeast two-hybrid, GST pulldown, co-immunoprecipitation, cell spreading assays, fluorescence microscopy\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP and pulldown confirming interaction, multiple orthogonal methods, functional readout with domain mutants, >140 citations\",\n      \"pmids\": [\"12058076\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"CrkL binds ASAP1 and directs its localization to peripheral focal adhesions. In spreading platelets, endogenous ASAP1 localizes at peripheral focal adhesions. Co-expression of wild-type CrkL (but not an SH2-mutated CrkL that cannot localize at focal adhesions) recruits ASAP1 to CrkL-induced focal adhesions, indicating CrkL links ASAP1 to focal adhesions via CrkL's SH2 domain-dependent focal adhesion targeting.\",\n      \"method\": \"Pulldown with mass spectrometry identification, co-immunoprecipitation, overexpression in COS7 cells, fluorescence microscopy\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — MS identification validated by co-IP, localization linked to functional consequence via SH2 mutant, single lab\",\n      \"pmids\": [\"12522101\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The N-terminal BAR domain of ASAP1, together with the PH domain, dimerizes to form an extended structure that binds large unilamellar vesicles containing acidic phospholipids and bends vesicle membranes to form tubular structures in vitro. This membrane-bending activity is regulated by Arf1-GTP binding to the ArfGAP domain. In cells, ASAP1 BAR domain-containing mutants induced tubular structures containing EGFR and Rab11, and ASAP1 colocalized with EGFR during receptor recycling; expression of ASAP1 accelerated EGFR trafficking and slowed cell spreading in a BAR-domain-dependent manner.\",\n      \"method\": \"Recombinant protein biophysics, large unilamellar vesicle (LUV) binding and tubulation assays, electron microscopy, live-cell fluorescence microscopy, EGFR trafficking assays\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted membrane bending in vitro with structural EM validation, confirmed in cells with mechanistic mutants, multiple orthogonal methods\",\n      \"pmids\": [\"16431365\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Both ASAP1a and ASAP1b splice variants associate with invadopodia and podosomes. Reduction of ASAP1 by siRNA blocks formation of invadopodia and podosomes. Podosome formation requires ASAP1's BAR domain, SH3 domain, and Src phosphorylation site, but not the Src binding site or GAP activity per se. ASAP1 is thus a critical downstream target of tyrosine kinase signaling (Src) in podosome and invadopodium assembly, functioning as a potential coincidence detector of SH3-domain protein association and Src phosphorylation.\",\n      \"method\": \"siRNA knockdown, recombinant mutant rescue, fluorescence microscopy, live-cell FRAP\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — siRNA loss-of-function with defined phenotype, systematic mutant dissection of domains, replicated across invadopodia and podosomes\",\n      \"pmids\": [\"17893324\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"ASAP1 uses Arf1-GTP as a substrate with a kcat of ~57 s⁻¹ and Km of ~2.2 μM (steady-state), forming a binary Arf1-GTP–ASAP1 complex that is stabilized by AlF4⁻. Arg-497 is the catalytic arginine finger (mutations reduce kcat >> Km). Mutations in residues Trp-479, Ile-490, Arg-505, Leu-511, and Asp-512 also primarily affect kcat rather than Km, suggesting a conformational transition to the catalytically active state. ASAP1 mutants lacking activity in vitro also lack activity in a dorsal ruffle cell-based assay.\",\n      \"method\": \"Steady-state and single-turnover kinetics with LUVs, AlF4⁻ stabilization, site-directed mutagenesis, in vivo dorsal ruffle assay\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — rigorous kinetic characterization with mutagenesis, in vitro and in vivo correlation, defines catalytic mechanism\",\n      \"pmids\": [\"17112341\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The BAR domain of ASAP1 autoinhibits GAP activity through intraprotein interactions. The BAR-PZA protein has greater Km and smaller kcat than PZA (PH-ArfGAP-Ank) alone on LUV surfaces. This effect depends on the N-terminal loop of the BAR domain and is not due to differential membrane association or changes in vesicle curvature, suggesting the BAR domain modulates the catalytic mechanism of the adjacent PH and GAP domains.\",\n      \"method\": \"Recombinant protein LUV-based kinetic assays, BAR domain loop deletion mutants, analytical ultracentrifugation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro enzymatic assay with saturation kinetics and single-turnover kinetics, mechanistic mutagenesis of BAR loop\",\n      \"pmids\": [\"19017632\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"NMR spectroscopy and biochemical analysis reveal that the PH domain of ASAP1 dynamically interacts with the ArfGAP and ankyrin repeat domains. The PH-ArfGAP domain interaction partially occludes the PIP2 binding site in the soluble protein, but the PIP2 binding site is accessible when ASAP1 is membrane-bound. PIP2 binding alters PH domain conformation; mutations in the PH domain loop contacting the ArfGAP domain affect PIP2 binding and both Km and kcat for Arf1-GTP hydrolysis.\",\n      \"method\": \"NMR spectroscopy, analytical ultracentrifugation, PIP2 binding assay, GAP activity kinetics with point mutants\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — NMR structural analysis combined with kinetics and mutagenesis, defines allosteric PH-ArfGAP interdomain regulation\",\n      \"pmids\": [\"18675341\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"GEFH1, a RhoA guanine nucleotide exchange factor, binds the BAR domain of ASAP1. Endogenous GEFH1 co-immunoprecipitates with ASAP1 and colocalizes with ASAP1 in podosomes. Overexpression of GEFH1 inhibits podosome assembly and ASAP1 GAP catalytic activity; a GEFH1 mutant lacking the BAR-domain binding region is less effective. siRNA knockdown of GEFH1 does not affect matrix degradation but increases the rate of podosome assembly. GEFH1 is therefore a negative regulator of podosomes acting via ASAP1.\",\n      \"method\": \"Yeast two-hybrid screening, co-immunoprecipitation, fluorescence microscopy, overexpression and siRNA knockdown, GAP activity assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — endogenous co-IP validated, loss/gain-of-function with defined phenotype, single lab\",\n      \"pmids\": [\"21352810\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The Arf GAP ASAP1 serves as a scaffold for ciliary receptor targeting of rhodopsin. ASAP1 brings together Arf4 (GTP-bound), Rab11, Rab8, and the Rab8-GEF Rabin8 into a complex. Ablation of ASAP1 abolishes ciliary targeting and causes formation of actin-rich periciliary membrane projections with mislocalized rhodopsin. ASAP1 recognizes the FR ciliary targeting signal of rhodopsin; the rhodopsin FR→AA mutant fails to interact with Rab8 and fails to cross the periciliary diffusion barrier.\",\n      \"method\": \"siRNA/shRNA ablation, co-immunoprecipitation, fluorescence and electron microscopy, ciliary targeting assays, ciliary signal mutant analysis\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — ablation with defined phenotype, complex reconstitution by co-IP, signal motif mutagenesis validated functionally, replicated across methods\",\n      \"pmids\": [\"22983554\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The PH domain of ASAP1 binds PtdIns(4,5)P2 at two sites: a canonical (C) site and an atypical (A) site. Structures of unliganded and dibutyryl-PtdIns(4,5)P2-bound PH domain were solved. PtdIns(4,5)P2 dependence of LUV binding and GAP activity is sigmoidal (cooperative), and mutations in either the C or A site reduce both PIP2-dependent vesicle binding and GAP activity, supporting a cooperative two-site PIP2 binding mechanism that enables rapid switching of ASAP1 activity.\",\n      \"method\": \"X-ray crystallography, LUV binding assays, GAP activity assays, site-directed mutagenesis, comparison with PLC-δ1 PH domain\",\n      \"journal\": \"Structure (London, England : 1993)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structures of both apo and ligand-bound forms, mutagenesis validated against biochemical assays, multiple orthogonal methods\",\n      \"pmids\": [\"26365802\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"FIP3 (RAB11FIP3), an Arf and Rab11 effector, promotes the activity of Rab11a and ASAP1 in Arf4-dependent ciliary transport of rhodopsin. FIP3 competes with rhodopsin for binding to ASAP1 and displaces rhodopsin from the ternary Arf4-GTP–ASAP1 complex. FIP3 also coordinates ASAP1 and Rab11a interactions with Rabin8, facilitating the Rab11-Rabin8-Rab8 cascade assembly for ciliary receptor trafficking.\",\n      \"method\": \"Co-immunoprecipitation, competition binding assays, siRNA ablation with ciliary targeting readout, fluorescence microscopy\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple co-IPs, competition binding, ablation with defined phenotype, mechanistic dissection of complex assembly\",\n      \"pmids\": [\"25673879\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"ASAP1 knockdown in mouse mammary gland leads to a marked increase in repopulating activity in vivo, indicating ASAP1 acts as a negative regulator of mammary stem cell activity.\",\n      \"method\": \"Pooled shRNA screen in primary mammary cells, in vivo transplantation assay, RNA-seq expression profiling\",\n      \"journal\": \"BMC cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo KD with specific quantitative readout (repopulating activity), single lab with functional validation\",\n      \"pmids\": [\"25879659\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"ASAP1-depleted dendritic cells show impaired matrix degradation and migration, and rs10956514 is associated with the level of reduction of ASAP1 expression after M. tuberculosis infection. ASAP1 is highly expressed in dendritic cells and involved in podosome formation and actin/membrane remodeling; its depletion impairs DC migration in the context of TB susceptibility.\",\n      \"method\": \"siRNA knockdown of ASAP1 in DCs, matrix degradation assay, migration assay, eQTL analysis linking SNP to ASAP1 expression\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct KD with defined cellular phenotype (migration, matrix degradation), functionally linked to genetic variant, single experimental approach\",\n      \"pmids\": [\"25774636\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"ASAP1 directly binds nonmuscle myosin 2A (NM2A) through the BAR-PH tandem domain in vitro, and ASAP1 and NM2A co-immunoprecipitate and colocalize in cells. Knockdown of ASAP1 reduces colocalization of NM2A and F-actin. ASAP1 and NM2A knockdowns recapitulate each other's effects on focal adhesions, cell migration, cell spreading, and circular dorsal ruffles (CDRs). Exogenous NM2A rescues ASAP1 knockdown effects on CDRs but not vice versa, indicating ASAP1 is a positive regulator of NM2A.\",\n      \"method\": \"In vitro binding assay, co-immunoprecipitation, siRNA knockdown, fluorescence microscopy, functional assays (spreading, migration, CDRs)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vitro direct binding confirmed by reciprocal co-IP, symmetrical KD phenotypes, rescue experiment, multiple orthogonal assays\",\n      \"pmids\": [\"26893376\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Loss of ASAP1 in mice leads to defects in adipogenic and osteogenic differentiation of mesenchymal progenitor cells. Mechanistically, FAK/Src and PI3K/AKT signaling are compromised in Asap1GT/GT MEFs, leading to impaired adipogenic and osteogenic differentiation, while chondrogenic differentiation is accelerated.\",\n      \"method\": \"Gene-trap mouse model, in vivo histology, in vitro differentiation assays, kinase signaling analysis\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with defined in vivo and in vitro differentiation phenotypes, signaling pathway analysis, single lab study\",\n      \"pmids\": [\"31246957\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The N-BAR domain of ASAP1 directly controls actin stress fiber organization. ASAP1 depletion causes defects in stress fiber organization while overexpression enhances actin remodeling; the BAR-PH fragment is sufficient for this effect. The BAR-PH tandem of ASAP1 directly binds and bundles actin filaments in vitro; the ArfGAP and C-terminal SH3 domains reduce filament binding and bundling by the BAR-PH domain.\",\n      \"method\": \"siRNA knockdown, overexpression, actin cosedimentation/bundling assays, fluorescence microscopy\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution of direct actin binding and bundling, combined with cell-based KD/OE with domain dissection\",\n      \"pmids\": [\"31785555\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PIP2 regulates binding of the ASAP1 PH domain to the N-terminal extension (residues 2–17) of ARF1, thereby contributing to GAP activity regulation. Without the ARF1 N-terminus, PIP2 has little effect on ASAP1 GAP activity. A peptide comprising residues 2–17 of ARF1 inhibits GAP activity and binds PIP2-dependently to the PH domain and a 17-amino-acid interdomain linker. Mutations reducing ARF1 N-terminal binding to the PH domain also reduce GAP activity and ASAP1-driven cellular actin remodeling.\",\n      \"method\": \"In vitro GAP assay with truncated ARF1 variants and peptides, PH domain binding assays, site-directed mutagenesis, actin remodeling cell assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro biochemical reconstitution with multiple ARF1 variants, mutagenesis of interaction interface, correlated with in vivo actin remodeling readout\",\n      \"pmids\": [\"31591270\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The N-BAR domain of ASAP1 directly binds F-actin, promotes formation of predominantly unipolar actin bundles, and stabilizes them against depolymerization. ASAP1 homodimerization aligns F-actin in bundles. The ASAP1 N-BAR domain moderately reduces spontaneous G-actin polymerization. Overexpression of the BAR-PH tandem in fibroblasts induces actin-filled cellular projections more effectively than full-length ASAP1; an ASAP1 construct lacking the N-BAR domain fails to induce projections.\",\n      \"method\": \"Actin cosedimentation, polymerization and depolymerization assays, TIRF microscopy, confocal microscopy, electron microscopy, cell overexpression\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple in vitro actin binding/bundling assays with EM validation, cell-based functional assays, domain deletion analysis\",\n      \"pmids\": [\"32444496\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Binding of multiple PIP2 molecules to the ASAP1 PH domain triggers an allosteric conformational switch and maintains the PH domain in a well-defined orientation at the membrane, allowing critical contacts with Arf1 to occur. NMR, neutron reflectometry, and molecular dynamics simulations together define how PH domain membrane binding positions ASAP1 for optimal Arf1 interaction and GTP hydrolysis.\",\n      \"method\": \"Solution NMR, neutron reflectometry, molecular dynamics simulation, reconstituted membrane-binding assays\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple structural and biophysical methods (NMR, neutron reflectometry, MD) in a single study with functional implication for catalysis\",\n      \"pmids\": [\"32998886\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The N-terminal extension (amino acids 2–17) of Arf1 is a critical structural determinant for interaction with ASAP1, AGAP1, and Arf GAP1, though each GAP has a unique interface. Deletion of residues 2–17 reduces ASAP1 interaction by 200-fold and residues 2–17 bind directly to ASAP1. Lysines 15 and 16 contribute more to ASAP1/AGAP1 interaction than to Arf GAP1 interaction; Leu-8 distinguishes Arf GAP1 binding from ASAP1/AGAP1.\",\n      \"method\": \"GAP activity assay with Arf1 deletion and point mutants, antibody sequestration, direct peptide binding assay\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro enzymatic assays with multiple Arf1 mutants, direct binding confirmed, defines substrate recognition interface\",\n      \"pmids\": [\"15212764\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Myr-Arf1 (active, membrane-anchored GTP form) exists in dynamic equilibrium between membrane-associated and membrane-distal G-domain conformations on lipid bilayers. The PH domain of ASAP1 restricts Arf1 G-domain motions and locks it in a conformation that exposes functionally relevant regions for GAP-catalyzed GTP hydrolysis.\",\n      \"method\": \"NMR, neutron reflectometry, molecular dynamics simulation of membrane-anchored Arf1 in complex with ASAP1 PH domain\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple orthogonal structural/biophysical methods defining dynamic conformational landscape with functional implications\",\n      \"pmids\": [\"37989735\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"ASAP1 inhibits ubiquitin-mediated proteasomal degradation of IQGAP1, thereby enhancing CDC42 activity. Activated CDC42 upregulates the EGFR-MAPK pathway, promoting chemotherapy resistance in gastric cancer cells.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, siRNA knockdown, overexpression in cell lines, in vivo xenograft\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mechanistic pathway dissection with co-IP and functional assays, single lab, novel downstream pathway\",\n      \"pmids\": [\"36792578\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ASAP1 is a multi-domain ArfGAP scaffold protein that catalyzes PIP2-dependent, membrane-surface GTP hydrolysis on Arf1 (and Arf5) through a binary complex mechanism regulated by cooperative PIP2 binding to the PH domain (which allosterically controls catalysis and positions Arf1 via its N-terminal extension), while its N-BAR domain directly bundles F-actin, autoinhibits GAP activity through intraprotein contacts, mediates membrane tubulation, and serves as a binding platform for Src (leading to tyrosine phosphorylation at a site required for podosomes/invadopodia), FAK (regulating focal adhesion assembly), CrkL (directing peripheral focal adhesion targeting), NM2A (actomyosin network remodeling), GEFH1 (negative regulator of podosomes), and components of the ciliary receptor targeting machinery (Arf4, Rab11, Rabin8, FIP3), thereby coordinately linking membrane remodeling, actin cytoskeletal dynamics, cell migration, and sensory receptor trafficking to primary cilia.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"ASAP1 is a multi-domain ArfGAP scaffold protein that integrates membrane remodeling, actin cytoskeletal dynamics, and vesicular trafficking through its enzymatic and structural activities. Its PH domain cooperatively binds PtdIns(4,5)P2 at two sites, allosterically positioning membrane-anchored Arf1-GTP for catalytic GTP hydrolysis via the arginine finger Arg-497, with the N-BAR domain exerting autoinhibitory control over GAP activity through intramolecular contacts [PMID:26365802, PMID:17112341, PMID:19017632, PMID:37989735]. The N-BAR domain additionally binds and bundles F-actin directly, tubulates membranes, and serves as a binding platform for NM2A and GEFH1, while the C-terminal SH3 domain recruits FAK and CrkL to focal adhesions; Src-mediated tyrosine phosphorylation and these scaffolding interactions are required for podosome/invadopodium formation, cell spreading, and migration [PMID:32444496, PMID:17893324, PMID:12058076, PMID:26893376]. ASAP1 also scaffolds an Arf4–Rab11–FIP3–Rabin8–Rab8 complex that targets rhodopsin and other sensory receptors to primary cilia, and its loss abolishes ciliary receptor trafficking [PMID:22983554, PMID:25673879].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Establishing ASAP1 as a PIP2-dependent ArfGAP with Src-family and Crk interactions defined its molecular identity and placed it at the intersection of Arf signaling, phosphoinositide regulation, and tyrosine-kinase pathways.\",\n      \"evidence\": \"In vitro GAP assay with purified protein, GST pulldown and co-IP for Src/Crk binding, tyrosine phosphorylation in activated-Src cells\",\n      \"pmids\": [\"9819391\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological substrates among Arf isoforms in cells not determined\", \"Tyrosine phosphorylation site identity and functional consequence unknown\", \"No structural information on multi-domain architecture\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Demonstration that ASAP1 localizes to focal adhesions, regulates cell spreading and migration in a GAP-activity-dependent manner, and acts on Arf1 (not Arf6) in cells connected its enzymatic specificity to cytoskeletal remodeling phenotypes.\",\n      \"evidence\": \"Fluorescence microscopy, overexpression of WT and GAP-inactive mutants, cell-based ARF GAP assay, chemotaxis assays\",\n      \"pmids\": [\"10725410\", \"11773070\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism linking Arf1 GTP hydrolysis to focal adhesion dynamics unknown\", \"Contribution of non-catalytic domains not dissected\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Identification of direct FAK and CrkL interactions mapped how ASAP1 is recruited to focal adhesions and linked its scaffold function to focal adhesion assembly independent of catalysis.\",\n      \"evidence\": \"Yeast two-hybrid, reciprocal co-IP, GST pulldown, SH3/SH2-domain mutant analysis, cell spreading assays\",\n      \"pmids\": [\"12058076\", \"12522101\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether FAK phosphorylates ASAP1 and its consequence unknown\", \"CrkL–ASAP1 interaction validated in a single lab\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Defining the Arf1 N-terminal extension (residues 2–17) as a critical substrate-recognition determinant for ASAP1 resolved how ASAP1 discriminates among Arf family members.\",\n      \"evidence\": \"In vitro GAP assay with Arf1 deletion/point mutants, direct peptide binding\",\n      \"pmids\": [\"15212764\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the N-terminus–ASAP1 interface not resolved at atomic level\", \"How this recognition interface operates on membrane surfaces unknown\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Discovery that the BAR domain dimerizes, tubulates membranes, and promotes EGFR recycling established ASAP1 as a membrane-bending protein linking Arf signaling to receptor trafficking.\",\n      \"evidence\": \"Recombinant BAR-PH biophysics, LUV tubulation with EM, EGFR trafficking assays in cells\",\n      \"pmids\": [\"16431365\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endogenous role in EGFR trafficking not confirmed by loss-of-function\", \"How Arf1-GTP binding regulates BAR-mediated tubulation structurally unresolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Kinetic characterization identified Arg-497 as the catalytic arginine finger and established a conformational-transition mechanism for GAP-catalyzed GTP hydrolysis, while siRNA experiments showed ASAP1 is required for podosome/invadopodium formation via Src phosphorylation and the BAR/SH3 domains rather than GAP activity alone.\",\n      \"evidence\": \"Steady-state and single-turnover kinetics with mutagenesis; siRNA knockdown and systematic domain-mutant rescue in podosome/invadopodium assays\",\n      \"pmids\": [\"17112341\", \"17893324\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the Src phosphorylation site critical for podosomes not mapped\", \"How BAR and SH3 domains cooperate in podosome nucleation mechanistically unclear\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"NMR and kinetic analyses revealed that the BAR domain autoinhibits GAP activity via its N-terminal loop and that the PH domain allosterically communicates PIP2 binding to the ArfGAP domain, establishing a multi-layered intramolecular regulatory mechanism.\",\n      \"evidence\": \"NMR spectroscopy of PH–ArfGAP interdomain contacts, LUV-based kinetics with BAR-loop and PH-domain mutants\",\n      \"pmids\": [\"19017632\", \"18675341\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length ASAP1 structure not available\", \"How autoinhibition is relieved by physiological signals undefined\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Identification of GEFH1 as a BAR-domain-binding negative regulator of podosomes through ASAP1 added a RhoA-GEF input to the ASAP1 signaling nexus at podosomes.\",\n      \"evidence\": \"Yeast two-hybrid, endogenous co-IP, overexpression and siRNA with podosome/GAP readouts\",\n      \"pmids\": [\"21352810\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether GEFH1 activates RhoA locally at podosomes through ASAP1 not tested\", \"GEFH1–ASAP1 interaction confirmed in single lab\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstrating that ASAP1 scaffolds an Arf4–Rab11–Rabin8–Rab8 complex for rhodopsin ciliary targeting revealed a non-cytoskeletal function: coordinating the Arf-to-Rab cascade at the base of primary cilia.\",\n      \"evidence\": \"siRNA/shRNA ablation with ciliary targeting readout, co-IP of multi-protein complex, FR motif mutagenesis\",\n      \"pmids\": [\"22983554\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether ASAP1 GAP activity is required for ciliary targeting not resolved\", \"Generalizability to other ciliary cargo beyond rhodopsin not established\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Crystal structures of the PH domain with and without PtdIns(4,5)P2, combined with mutagenesis, established a cooperative two-site PIP2 binding mechanism enabling switch-like regulation of GAP activity, while FIP3 was shown to coordinate ASAP1 and Rab11a in ciliary transport.\",\n      \"evidence\": \"X-ray crystallography of apo and PIP2-bound PH domain, LUV binding/GAP assays with C/A-site mutants; co-IP and competition binding for FIP3\",\n      \"pmids\": [\"26365802\", \"25673879\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full kinetic model of cooperativity with membrane-reconstituted protein lacking\", \"FIP3 competition mechanism not structurally resolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Direct binding of NM2A to the BAR-PH tandem and reciprocal knockdown phenocopy established ASAP1 as a positive regulator of actomyosin contractility at focal adhesions and circular dorsal ruffles.\",\n      \"evidence\": \"In vitro binding, reciprocal co-IP, siRNA KD phenocopy, NM2A rescue of ASAP1-KD CDR defect\",\n      \"pmids\": [\"26893376\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether NM2A binding competes with actin bundling by the BAR domain not tested\", \"Structural basis of BAR-PH–NM2A interaction unknown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Reconstitution showed the N-BAR domain directly binds and bundles F-actin and that PIP2-dependent PH domain interaction with the Arf1 N-terminal extension is a key determinant of GAP regulation, unifying the actin-remodeling and catalytic functions in a single mechanistic framework.\",\n      \"evidence\": \"Actin cosedimentation/bundling, TIRF, EM; GAP assays with N-terminally truncated Arf1 and PH-domain mutants\",\n      \"pmids\": [\"31785555\", \"31591270\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How simultaneous actin bundling and membrane tubulation are coordinated unclear\", \"Relative contributions of actin bundling vs. GAP activity to cell migration not separated\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Biophysical studies revealed that cooperative PIP2 binding orients the PH domain at the membrane surface, and the PH domain in turn locks membrane-anchored Arf1 in a conformation competent for GTP hydrolysis, completing a structural model of allosteric catalytic activation.\",\n      \"evidence\": \"NMR, neutron reflectometry, MD simulations of PH domain–membrane and Arf1–membrane complexes\",\n      \"pmids\": [\"32998886\", \"37989735\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length ASAP1 on membranes not yet visualized structurally\", \"How BAR-domain autoinhibition integrates with PH-domain membrane orientation unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"A novel non-GAP function was described in which ASAP1 stabilizes IQGAP1 by inhibiting its ubiquitin-mediated degradation, thereby activating CDC42 and EGFR-MAPK signaling in cancer cells.\",\n      \"evidence\": \"Co-IP, ubiquitination assay, siRNA/overexpression, xenograft\",\n      \"pmids\": [\"36792578\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether ASAP1 directly deubiquitinates IQGAP1 or prevents ubiquitin ligase access not distinguished\", \"Single lab, not independently replicated\", \"Relevance beyond gastric cancer unclear\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A full-length ASAP1 structure on membranes that explains how BAR-mediated autoinhibition, PIP2-driven allosteric activation, actin bundling, and scaffold interactions are coordinated spatiotemporally remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No full-length atomic structure of ASAP1\", \"Mechanism by which Src phosphorylation relieves autoinhibition and promotes podosomes not structurally defined\", \"How ASAP1 partitions between focal adhesion, podosome, and ciliary functions in a single cell unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003924\", \"supporting_discovery_ids\": [0, 2, 7, 8, 12, 19]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 7, 8]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [8, 10, 24]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [18, 20]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [5, 12, 21]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [3, 4, 11, 16]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 5, 12, 21]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [1, 6, 18, 20]},\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [11, 13]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 9]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 2, 7, 11, 24]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [5, 11, 13]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [11, 13]},\n      {\"term_id\": \"R-HSA-1500931\", \"supporting_discovery_ids\": [1, 3, 6]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"ARF1\", \"FAK\", \"CRKL\", \"MYH9\", \"GEFH1\", \"ARF4\", \"RAB11A\", \"FIP3\"],\n    \"other_free_text\": []\n  }\n}\n```"}