{"gene":"RAP1GAP2","run_date":"2026-04-28T19:45:45","timeline":{"discoveries":[{"year":2005,"finding":"RAP1GAP2 is a GTPase-activating protein (GAP) for Rap1 expressed in human platelets, encoded by a 715-amino acid protein with at least 3 splice variants. It exhibits strong GTPase-stimulating activity toward Rap1 in transfected cells, colocalizes with Rap1 in platelets, and is phosphorylated by cGMP-dependent protein kinase I (cGKI) exclusively on serine 7, a residue present only in platelet splice variants.","method":"5'-RACE cDNA cloning, transfection-based GAP activity assay, immunofluorescence colocalization, in vitro phosphorylation assay with cGKI, site-directed mutagenesis","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1–2 — original discovery with multiple orthogonal methods including in vitro kinase assay, mutagenesis identifying Ser7, and functional GAP assay","pmids":["15632203"],"is_preprint":false},{"year":2007,"finding":"14-3-3 proteins interact with phosphorylated serine 9 at the N-terminus of RAP1GAP2 in platelets. Platelet activation by ADP and thrombin enhances Ser9 phosphorylation and increases 14-3-3 binding, whereas inhibition by nitric oxide and prostacyclin disrupts 14-3-3 binding via cGMP- and cAMP-dependent protein kinases that phosphorylate Ser7 (adjacent to the 14-3-3 binding site). 14-3-3 binding does not alter GAP catalytic activity in vitro but attenuates RAP1GAP2-mediated inhibition of cell adhesion.","method":"Co-immunoprecipitation, in vitro phosphorylation assay, cell adhesion assay, pharmacological inhibition of cGK/cAK","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP at endogenous level in platelets, in vitro GAP assay, and cell adhesion functional readout with multiple orthogonal methods","pmids":["18039662"],"is_preprint":false},{"year":2009,"finding":"RAP1GAP2 interacts with synaptotagmin-like protein 1 (Slp1) through a TKXT motif (T524-K525-X-T527) in its C-terminus binding to the C2A domain of Slp1. RAP1GAP2, Slp1, and Rab27 form a trimeric complex in transfected cells and in human platelets. Purified RAP1GAP2 augments dense granule secretion in permeabilized platelets, and deletion of the Slp1-binding TKXT motif abolishes this effect, indicating RAP1GAP2 modulates platelet dense granule secretion by binding to Slp1.","method":"Yeast two-hybrid screening, Co-IP in COS-1/HeLa cells and human platelets, deletion/truncation mapping, permeabilized platelet granule secretion assay with purified proteins","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1–2 — yeast two-hybrid discovery confirmed by endogenous Co-IP, domain mapping, and reconstituted functional secretion assay with purified proteins","pmids":["19528539"],"is_preprint":false},{"year":2006,"finding":"The GoLoco motif of RAP1GAP2b/c is functionally inactive: it lacks GDI activity toward Gαi/o subunits and cannot interact with Gα(i1). This is partly attributable to a lysine (Lys-75) at the position normally occupied by arginine in canonical GoLoco motifs; however, mutation of Lys-75 to arginine could not restore Gα interaction, indicating additional sequence determinants contribute to its inactivity.","method":"Biophysical binding assay (GDI activity measurement), site-directed mutagenesis (Lys75Arg), primary sequence analysis","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 1 — in vitro biophysical assay with mutagenesis, single study","pmids":["16949794"],"is_preprint":false},{"year":2012,"finding":"Rap1gap2 limits neurite outgrowth and branching in Neuro-2a cells and counteracts Rap1-induced augmentation of neurite outgrowth. In mouse olfactory sensory neurons (OSNs), Rap1gap2 overexpression stunts axon outgrowth, while knockdown of Rap1gap2 significantly increases axon length, establishing a role for Rap1gap2 in controlling Rap1-dependent axon growth dynamics during early postnatal development.","method":"Overexpression and siRNA knockdown in Neuro-2a cells and in vivo OSN model, neurite length measurement, in vitro axon outgrowth assay","journal":"Molecular and cellular neurosciences","confidence":"Medium","confidence_rationale":"Tier 2–3 — loss-of-function and gain-of-function with defined cellular phenotype and Rap1 epistasis, single lab","pmids":["22732430"],"is_preprint":false},{"year":2015,"finding":"Slp2-a (synaptotagmin-like protein 2-a) interacts with RAP1GAP2 via its C2B domain and regulates renal epithelial cell size; this interaction is distinct from Rab27 binding. Loss of Slp2-a leads to excess ezrin activation, indicating RAP1GAP2 participates in a Slp2-a-dependent pathway controlling cell size.","method":"Co-IP, siRNA knockdown in MDCK II cells, cell size measurement, pharmacological inhibition","journal":"Biochemical and biophysical research communications","confidence":"Low","confidence_rationale":"Tier 3 — RAP1GAP2 involvement is described indirectly from prior work cited in the abstract, with limited mechanistic detail for RAP1GAP2 specifically in this paper","pmids":["25817786"],"is_preprint":false}],"current_model":"RAP1GAP2 is a Rap1-specific GTPase-activating protein (GAP) expressed in platelets and neurons that terminates Rap1 signaling to regulate integrin activation, platelet aggregation, dense granule secretion, and axon outgrowth; its activity is regulated by cGKI/cAKI-mediated phosphorylation at Ser7 (which disrupts 14-3-3 binding to adjacent Ser9) and by interaction with synaptotagmin-like protein 1 (Slp1) through a C-terminal TKXT motif within a trimeric RAP1GAP2–Slp1–Rab27 complex, while its GoLoco motif is intrinsically inactive toward Gα(i/o) subunits."},"narrative":{"teleology":[{"year":2005,"claim":"Identification of RAP1GAP2 as a platelet-expressed Rap1 GAP and discovery of its phosphorylation by cGKI on Ser7 established the first molecular link between cGMP-dependent inhibitory signaling and Rap1 inactivation in platelets.","evidence":"cDNA cloning from human platelet library, transfection-based GAP assays, in vitro kinase assay with cGKI, and site-directed mutagenesis of Ser7","pmids":["15632203"],"confidence":"High","gaps":["Functional consequence of Ser7 phosphorylation on GAP activity or platelet function was not determined","The mechanism by which RAP1GAP2 is recruited to Rap1 at the platelet membrane was unknown"]},{"year":2006,"claim":"Demonstrating that the GoLoco motif of RAP1GAP2 is functionally inactive toward Gαi/o ruled out a dual-function model in which RAP1GAP2 might simultaneously regulate both Rap1 and heterotrimeric G-protein signaling.","evidence":"In vitro GDI activity measurement and Lys75Arg mutagenesis","pmids":["16949794"],"confidence":"Medium","gaps":["Only a single study; independent confirmation of GoLoco inactivity is lacking","Whether the GoLoco motif has any non-canonical function (e.g., protein–protein interaction scaffold) was not tested"]},{"year":2007,"claim":"Discovery that 14-3-3 binds phospho-Ser9 of RAP1GAP2 and that Ser7 phosphorylation by cGKI/cAKI disrupts this interaction resolved how opposing platelet-activating and -inhibiting signals converge on RAP1GAP2 to control cell adhesion.","evidence":"Endogenous co-immunoprecipitation in platelets, in vitro phosphorylation, and cell adhesion assays with pharmacological inhibition of cGK/cAK","pmids":["18039662"],"confidence":"High","gaps":["14-3-3 binding did not alter catalytic GAP activity in vitro, leaving the mechanism by which it attenuates adhesion inhibition unresolved","In vivo relevance of the Ser7/Ser9 phospho-switch in thrombosis or hemostasis was not tested"]},{"year":2009,"claim":"Identification of the RAP1GAP2–Slp1–Rab27 trimeric complex and its requirement for dense granule secretion revealed a GAP-independent effector function of RAP1GAP2 in platelet exocytosis.","evidence":"Yeast two-hybrid screen, endogenous co-IP in platelets, TKXT motif deletion mapping, and reconstituted secretion assay with purified proteins in permeabilized platelets","pmids":["19528539"],"confidence":"High","gaps":["Whether GAP catalytic activity and Slp1 binding are coordinated or independent during platelet activation is unknown","Structural basis of the TKXT–C2A interaction has not been determined"]},{"year":2012,"claim":"Demonstrating that Rap1gap2 restricts Rap1-dependent axon outgrowth in olfactory sensory neurons extended its functional role beyond platelets to neuronal development.","evidence":"Overexpression and siRNA knockdown in Neuro-2a cells and in vivo olfactory sensory neuron model with neurite length quantification","pmids":["22732430"],"confidence":"Medium","gaps":["Downstream effectors linking Rap1 inactivation to cytoskeletal remodeling in neurons were not identified","Findings are from a single lab; genetic knockout confirmation is lacking"]},{"year":null,"claim":"Key unresolved questions include the structural basis of RAP1GAP2 catalysis and regulation, the in vivo consequences of RAP1GAP2 loss for hemostasis and neuronal circuit formation, and whether the Slp1/Slp2-a interactions represent tissue-specific modes of RAP1GAP2 regulation.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No knockout mouse phenotype has been reported","No structural model of the GAP domain or regulatory phospho-switch exists","Relative contributions of GAP activity versus Slp1-mediated secretion function in platelet physiology are unresolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[2]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[2]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-109582","term_label":"Hemostasis","supporting_discovery_ids":[0,1,2]}],"complexes":["RAP1GAP2–Slp1–Rab27 complex"],"partners":["RAP1A","SLP1","RAB27A","YWHAZ","PRKG1"],"other_free_text":[]},"mechanistic_narrative":"RAP1GAP2 is a Rap1-specific GTPase-activating protein that terminates Rap1 signaling to regulate integrin-mediated cell adhesion, platelet dense granule secretion, and axon outgrowth. In platelets, RAP1GAP2 GAP activity is modulated by phosphorylation: agonist-stimulated phosphorylation of Ser9 recruits 14-3-3 proteins to attenuate RAP1GAP2-mediated inhibition of adhesion, while cGKI/cAKI-mediated phosphorylation of the adjacent Ser7 disrupts 14-3-3 binding, restoring the capacity of RAP1GAP2 to suppress Rap1 [PMID:15632203, PMID:18039662]. RAP1GAP2 forms a trimeric complex with synaptotagmin-like protein 1 (Slp1) and Rab27 through a C-terminal TKXT motif, and this interaction is required for RAP1GAP2-dependent augmentation of dense granule secretion in permeabilized platelets [PMID:19528539]. In neurons, Rap1gap2 limits Rap1-dependent axon outgrowth and branching, as demonstrated by gain- and loss-of-function studies in olfactory sensory neurons [PMID:22732430]."},"prefetch_data":{"uniprot":{"accession":"Q684P5","full_name":"Rap1 GTPase-activating protein 2","aliases":["GTPase-activating Rap/Ran-GAP domain-like protein 4"],"length_aa":730,"mass_kda":80.1,"function":"GTPase activator for the nuclear Ras-related regulatory protein RAP-1A (KREV-1), converting it to the putatively inactive GDP-bound state","subcellular_location":"Cytoplasm; Cytoplasm, perinuclear region","url":"https://www.uniprot.org/uniprotkb/Q684P5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RAP1GAP2","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/RAP1GAP2","total_profiled":1310},"omim":[{"mim_id":"618714","title":"RAP1 GTPase-ACTIVATING PROTEIN 2; RAP1GAP2","url":"https://www.omim.org/entry/618714"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nuclear membrane","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"},{"location":"Perinuclear theca","reliability":"Additional"},{"location":"Flagellar centriole","reliability":"Additional"},{"location":"Principal piece","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"bone marrow","ntpm":26.2},{"tissue":"pancreas","ntpm":36.5}],"url":"https://www.proteinatlas.org/search/RAP1GAP2"},"hgnc":{"alias_symbol":["KIAA1039"],"prev_symbol":["GARNL4"]},"alphafold":{"accession":"Q684P5","domains":[{"cath_id":"3.30.1120.160","chopping":"153-254","consensus_level":"high","plddt":89.8723,"start":153,"end":254},{"cath_id":"3.40.50.11210","chopping":"260-446","consensus_level":"high","plddt":95.1839,"start":260,"end":446}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q684P5","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q684P5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q684P5-F1-predicted_aligned_error_v6.png","plddt_mean":64.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RAP1GAP2","jax_strain_url":"https://www.jax.org/strain/search?query=RAP1GAP2"},"sequence":{"accession":"Q684P5","fasta_url":"https://rest.uniprot.org/uniprotkb/Q684P5.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q684P5/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q684P5"}},"corpus_meta":[{"pmid":"29643944","id":"PMC_29643944","title":"Competing endogenous RNA expression profiling in pre-eclampsia identifies hsa_circ_0036877 as a potential novel blood biomarker for early pre-eclampsia.","date":"2018","source":"Clinical epigenetics","url":"https://pubmed.ncbi.nlm.nih.gov/29643944","citation_count":84,"is_preprint":false},{"pmid":"15632203","id":"PMC_15632203","title":"Rap1GAP2 is a new GTPase-activating protein of Rap1 expressed in human platelets.","date":"2005","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/15632203","citation_count":79,"is_preprint":false},{"pmid":"24824216","id":"PMC_24824216","title":"Genome-wide interaction studies reveal sex-specific asthma risk alleles.","date":"2014","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/24824216","citation_count":60,"is_preprint":false},{"pmid":"18039662","id":"PMC_18039662","title":"Cyclic nucleotide-dependent protein kinases inhibit binding of 14-3-3 to the GTPase-activating protein Rap1GAP2 in platelets.","date":"2007","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/18039662","citation_count":40,"is_preprint":false},{"pmid":"19528539","id":"PMC_19528539","title":"Synaptotagmin-like protein 1 interacts with the GTPase-activating protein Rap1GAP2 and regulates dense granule secretion in platelets.","date":"2009","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/19528539","citation_count":32,"is_preprint":false},{"pmid":"33062700","id":"PMC_33062700","title":"Identification of Circular RNA-MicroRNA-Messenger RNA Regulatory Network in Atrial Fibrillation by Integrated Analysis.","date":"2020","source":"BioMed research international","url":"https://pubmed.ncbi.nlm.nih.gov/33062700","citation_count":23,"is_preprint":false},{"pmid":"22832427","id":"PMC_22832427","title":"Hostility in adolescents and adults: a genome-wide association study of the Young Finns.","date":"2011","source":"Translational psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/22832427","citation_count":21,"is_preprint":false},{"pmid":"16949794","id":"PMC_16949794","title":"Differential G-alpha interaction capacities of the GoLoco motifs in Rap GTPase activating proteins.","date":"2006","source":"Cellular signalling","url":"https://pubmed.ncbi.nlm.nih.gov/16949794","citation_count":20,"is_preprint":false},{"pmid":"32901515","id":"PMC_32901515","title":"Methylome-wide association study of central adiposity implicates genes involved in immune and endocrine systems.","date":"2020","source":"Epigenomics","url":"https://pubmed.ncbi.nlm.nih.gov/32901515","citation_count":11,"is_preprint":false},{"pmid":"35959094","id":"PMC_35959094","title":"Sex-dimorphic gene effects on survival outcomes in people with coronary artery disease.","date":"2022","source":"American heart journal plus : cardiology research and practice","url":"https://pubmed.ncbi.nlm.nih.gov/35959094","citation_count":11,"is_preprint":false},{"pmid":"24269229","id":"PMC_24269229","title":"Modelling cellular signal communication mediated by phosphorylation dependent interaction with 14-3-3 proteins.","date":"2013","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/24269229","citation_count":5,"is_preprint":false},{"pmid":"22732430","id":"PMC_22732430","title":"Rap1gap2 regulates axon outgrowth in olfactory sensory neurons.","date":"2012","source":"Molecular and cellular neurosciences","url":"https://pubmed.ncbi.nlm.nih.gov/22732430","citation_count":3,"is_preprint":false},{"pmid":"25817786","id":"PMC_25817786","title":"Slp2-a inactivates ezrin by recruiting protein phosphatase 1 to the plasma membrane.","date":"2015","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/25817786","citation_count":2,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8087,"output_tokens":1918,"usd":0.026516},"stage2":{"model":"claude-opus-4-6","input_tokens":5180,"output_tokens":1895,"usd":0.109912},"total_usd":0.136428,"stage1_batch_id":"msgbatch_01SUR8NDzVrNmyszWyJeCct7","stage2_batch_id":"msgbatch_01G7Yfutko3cDWzejrwH5AMx","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2005,\n      \"finding\": \"RAP1GAP2 is a GTPase-activating protein (GAP) for Rap1 expressed in human platelets, encoded by a 715-amino acid protein with at least 3 splice variants. It exhibits strong GTPase-stimulating activity toward Rap1 in transfected cells, colocalizes with Rap1 in platelets, and is phosphorylated by cGMP-dependent protein kinase I (cGKI) exclusively on serine 7, a residue present only in platelet splice variants.\",\n      \"method\": \"5'-RACE cDNA cloning, transfection-based GAP activity assay, immunofluorescence colocalization, in vitro phosphorylation assay with cGKI, site-directed mutagenesis\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — original discovery with multiple orthogonal methods including in vitro kinase assay, mutagenesis identifying Ser7, and functional GAP assay\",\n      \"pmids\": [\"15632203\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"14-3-3 proteins interact with phosphorylated serine 9 at the N-terminus of RAP1GAP2 in platelets. Platelet activation by ADP and thrombin enhances Ser9 phosphorylation and increases 14-3-3 binding, whereas inhibition by nitric oxide and prostacyclin disrupts 14-3-3 binding via cGMP- and cAMP-dependent protein kinases that phosphorylate Ser7 (adjacent to the 14-3-3 binding site). 14-3-3 binding does not alter GAP catalytic activity in vitro but attenuates RAP1GAP2-mediated inhibition of cell adhesion.\",\n      \"method\": \"Co-immunoprecipitation, in vitro phosphorylation assay, cell adhesion assay, pharmacological inhibition of cGK/cAK\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP at endogenous level in platelets, in vitro GAP assay, and cell adhesion functional readout with multiple orthogonal methods\",\n      \"pmids\": [\"18039662\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"RAP1GAP2 interacts with synaptotagmin-like protein 1 (Slp1) through a TKXT motif (T524-K525-X-T527) in its C-terminus binding to the C2A domain of Slp1. RAP1GAP2, Slp1, and Rab27 form a trimeric complex in transfected cells and in human platelets. Purified RAP1GAP2 augments dense granule secretion in permeabilized platelets, and deletion of the Slp1-binding TKXT motif abolishes this effect, indicating RAP1GAP2 modulates platelet dense granule secretion by binding to Slp1.\",\n      \"method\": \"Yeast two-hybrid screening, Co-IP in COS-1/HeLa cells and human platelets, deletion/truncation mapping, permeabilized platelet granule secretion assay with purified proteins\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — yeast two-hybrid discovery confirmed by endogenous Co-IP, domain mapping, and reconstituted functional secretion assay with purified proteins\",\n      \"pmids\": [\"19528539\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The GoLoco motif of RAP1GAP2b/c is functionally inactive: it lacks GDI activity toward Gαi/o subunits and cannot interact with Gα(i1). This is partly attributable to a lysine (Lys-75) at the position normally occupied by arginine in canonical GoLoco motifs; however, mutation of Lys-75 to arginine could not restore Gα interaction, indicating additional sequence determinants contribute to its inactivity.\",\n      \"method\": \"Biophysical binding assay (GDI activity measurement), site-directed mutagenesis (Lys75Arg), primary sequence analysis\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — in vitro biophysical assay with mutagenesis, single study\",\n      \"pmids\": [\"16949794\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Rap1gap2 limits neurite outgrowth and branching in Neuro-2a cells and counteracts Rap1-induced augmentation of neurite outgrowth. In mouse olfactory sensory neurons (OSNs), Rap1gap2 overexpression stunts axon outgrowth, while knockdown of Rap1gap2 significantly increases axon length, establishing a role for Rap1gap2 in controlling Rap1-dependent axon growth dynamics during early postnatal development.\",\n      \"method\": \"Overexpression and siRNA knockdown in Neuro-2a cells and in vivo OSN model, neurite length measurement, in vitro axon outgrowth assay\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — loss-of-function and gain-of-function with defined cellular phenotype and Rap1 epistasis, single lab\",\n      \"pmids\": [\"22732430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Slp2-a (synaptotagmin-like protein 2-a) interacts with RAP1GAP2 via its C2B domain and regulates renal epithelial cell size; this interaction is distinct from Rab27 binding. Loss of Slp2-a leads to excess ezrin activation, indicating RAP1GAP2 participates in a Slp2-a-dependent pathway controlling cell size.\",\n      \"method\": \"Co-IP, siRNA knockdown in MDCK II cells, cell size measurement, pharmacological inhibition\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — RAP1GAP2 involvement is described indirectly from prior work cited in the abstract, with limited mechanistic detail for RAP1GAP2 specifically in this paper\",\n      \"pmids\": [\"25817786\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RAP1GAP2 is a Rap1-specific GTPase-activating protein (GAP) expressed in platelets and neurons that terminates Rap1 signaling to regulate integrin activation, platelet aggregation, dense granule secretion, and axon outgrowth; its activity is regulated by cGKI/cAKI-mediated phosphorylation at Ser7 (which disrupts 14-3-3 binding to adjacent Ser9) and by interaction with synaptotagmin-like protein 1 (Slp1) through a C-terminal TKXT motif within a trimeric RAP1GAP2–Slp1–Rab27 complex, while its GoLoco motif is intrinsically inactive toward Gα(i/o) subunits.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"RAP1GAP2 is a Rap1-specific GTPase-activating protein that terminates Rap1 signaling to regulate integrin-mediated cell adhesion, platelet dense granule secretion, and axon outgrowth. In platelets, RAP1GAP2 GAP activity is modulated by phosphorylation: agonist-stimulated phosphorylation of Ser9 recruits 14-3-3 proteins to attenuate RAP1GAP2-mediated inhibition of adhesion, while cGKI/cAKI-mediated phosphorylation of the adjacent Ser7 disrupts 14-3-3 binding, restoring the capacity of RAP1GAP2 to suppress Rap1 [PMID:15632203, PMID:18039662]. RAP1GAP2 forms a trimeric complex with synaptotagmin-like protein 1 (Slp1) and Rab27 through a C-terminal TKXT motif, and this interaction is required for RAP1GAP2-dependent augmentation of dense granule secretion in permeabilized platelets [PMID:19528539]. In neurons, Rap1gap2 limits Rap1-dependent axon outgrowth and branching, as demonstrated by gain- and loss-of-function studies in olfactory sensory neurons [PMID:22732430].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Identification of RAP1GAP2 as a platelet-expressed Rap1 GAP and discovery of its phosphorylation by cGKI on Ser7 established the first molecular link between cGMP-dependent inhibitory signaling and Rap1 inactivation in platelets.\",\n      \"evidence\": \"cDNA cloning from human platelet library, transfection-based GAP assays, in vitro kinase assay with cGKI, and site-directed mutagenesis of Ser7\",\n      \"pmids\": [\"15632203\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Functional consequence of Ser7 phosphorylation on GAP activity or platelet function was not determined\",\n        \"The mechanism by which RAP1GAP2 is recruited to Rap1 at the platelet membrane was unknown\"\n      ]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrating that the GoLoco motif of RAP1GAP2 is functionally inactive toward Gαi/o ruled out a dual-function model in which RAP1GAP2 might simultaneously regulate both Rap1 and heterotrimeric G-protein signaling.\",\n      \"evidence\": \"In vitro GDI activity measurement and Lys75Arg mutagenesis\",\n      \"pmids\": [\"16949794\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Only a single study; independent confirmation of GoLoco inactivity is lacking\",\n        \"Whether the GoLoco motif has any non-canonical function (e.g., protein–protein interaction scaffold) was not tested\"\n      ]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Discovery that 14-3-3 binds phospho-Ser9 of RAP1GAP2 and that Ser7 phosphorylation by cGKI/cAKI disrupts this interaction resolved how opposing platelet-activating and -inhibiting signals converge on RAP1GAP2 to control cell adhesion.\",\n      \"evidence\": \"Endogenous co-immunoprecipitation in platelets, in vitro phosphorylation, and cell adhesion assays with pharmacological inhibition of cGK/cAK\",\n      \"pmids\": [\"18039662\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"14-3-3 binding did not alter catalytic GAP activity in vitro, leaving the mechanism by which it attenuates adhesion inhibition unresolved\",\n        \"In vivo relevance of the Ser7/Ser9 phospho-switch in thrombosis or hemostasis was not tested\"\n      ]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identification of the RAP1GAP2–Slp1–Rab27 trimeric complex and its requirement for dense granule secretion revealed a GAP-independent effector function of RAP1GAP2 in platelet exocytosis.\",\n      \"evidence\": \"Yeast two-hybrid screen, endogenous co-IP in platelets, TKXT motif deletion mapping, and reconstituted secretion assay with purified proteins in permeabilized platelets\",\n      \"pmids\": [\"19528539\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether GAP catalytic activity and Slp1 binding are coordinated or independent during platelet activation is unknown\",\n        \"Structural basis of the TKXT–C2A interaction has not been determined\"\n      ]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstrating that Rap1gap2 restricts Rap1-dependent axon outgrowth in olfactory sensory neurons extended its functional role beyond platelets to neuronal development.\",\n      \"evidence\": \"Overexpression and siRNA knockdown in Neuro-2a cells and in vivo olfactory sensory neuron model with neurite length quantification\",\n      \"pmids\": [\"22732430\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Downstream effectors linking Rap1 inactivation to cytoskeletal remodeling in neurons were not identified\",\n        \"Findings are from a single lab; genetic knockout confirmation is lacking\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis of RAP1GAP2 catalysis and regulation, the in vivo consequences of RAP1GAP2 loss for hemostasis and neuronal circuit formation, and whether the Slp1/Slp2-a interactions represent tissue-specific modes of RAP1GAP2 regulation.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No knockout mouse phenotype has been reported\",\n        \"No structural model of the GAP domain or regulatory phospho-switch exists\",\n        \"Relative contributions of GAP activity versus Slp1-mediated secretion function in platelet physiology are unresolved\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-109582\", \"supporting_discovery_ids\": [0, 1, 2]}\n    ],\n    \"complexes\": [\n      \"RAP1GAP2–Slp1–Rab27 complex\"\n    ],\n    \"partners\": [\n      \"RAP1A\",\n      \"SLP1\",\n      \"RAB27A\",\n      \"YWHAZ\",\n      \"PRKG1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}