{"gene":"ARHGAP15","run_date":"2026-06-09T22:02:44","timeline":{"discoveries":[{"year":2003,"finding":"ARHGAP15 contains a pleckstrin homology (PH) domain, a RhoGAP domain, and a novel motif N-terminal to the GAP domain. The novel motif mediates nucleotide-independent Rac1 binding through the C-terminal half of Rac1 (established by swop mutants of Rac/Cdc42). The GAP domain shows specificity towards Rac1 in vitro. The PH domain is required for membrane/cell-periphery localization. Overexpression of full-length ARHGAP15 (but not PH-domain deletion mutant) increases actin stress fibers and cell contraction, effects attenuated by co-expression of dominant-negative Rac1(N17). ARHGAP15-expressing HeLa cells are resistant to phorbol myristate acetate treatment.","method":"In vitro GAP activity assay, Rac/Cdc42 swop mutants, overexpression/deletion constructs, co-expression with dominant-negative Rac1, cell morphology analysis, PMA treatment assay","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro GAP assay, domain-deletion mutagenesis, and genetic rescue with dominant-negative Rac1 in one study with multiple orthogonal methods","pmids":["12650940"],"is_preprint":false},{"year":2013,"finding":"ARHGAP15 serves as a substrate of Rac effectors Pak1 and Pak2 (identified by protein microarray screen). ARHGAP15 also binds Pak1/2 via its PH domain. The ArhGAP15–Pak1/2 association results in mutual inhibition: ARHGAP15 GAP activity is inhibited and Pak1/2 kinase activity is inhibited. Knockdown of ARHGAP15 activates Pak1/2 both indirectly (through Rac activation) and directly (by disrupting the ARHGAP15/Pak complex), indicating a dual negative regulatory role.","method":"Protein microarray screen, co-immunoprecipitation, kinase activity assay, GAP activity assay, siRNA knockdown","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — protein microarray identification, biochemical kinase/GAP activity assays, and reciprocal interaction studies with knockdown validation in one study","pmids":["23760270"],"is_preprint":false},{"year":2016,"finding":"Loss of ArhGAP15 in mice results in hyperactivation of Rac1/Rac3. In the hippocampus, ArhGAP15 knockout reduces the number of CR+, PV+, and SST+ inhibitory interneurons in CA3 and dentate gyrus due to reduced efficiency and directionality of their migration (pyramidal neurons are unaffected). Loss of ArhGAP15 alters neuritogenesis and the balance between excitatory and inhibitory synapses, resulting in increased spike frequency and bursts with poor synchronization. Adult ArhGAP15-/- mice show defective hippocampus-dependent working and associative memory.","method":"ArhGAP15 knockout mouse model, Rac1/Rac3 activity assays, interneuron counting and migration analysis, electrophysiology, behavioral testing","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic knockout with multiple orthogonal readouts (biochemical Rac activity, cellular migration, electrophysiology, behavior) in a single study","pmids":["27713499"],"is_preprint":false},{"year":2017,"finding":"FOXP3 transcriptionally regulates ARHGAP15 expression. Overexpression of FOXP3 upregulates ARHGAP15, which inactivates Rac1, inhibiting glioma cell migration. Silencing FOXP3 downregulates ARHGAP15 and activates Rac1, promoting migration. FOXP3 also regulates EMT markers E-cadherin and N-cadherin in this context.","method":"DNA microarray, qRT-PCR, Western blot, immunohistochemistry, overexpression and siRNA knockdown in glioma cells, migration assays","journal":"Cancer science","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — overexpression and knockdown with multiple readouts in a single lab, but no direct promoter binding or ChIP assay reported in abstract","pmids":["27862679"],"is_preprint":false},{"year":2018,"finding":"In colorectal cancer cells, ARHGAP15 overexpression activates PTEN signaling, increases FOXO1 activity, and decreases AKT phosphorylation. This leads to increased p21 (causing S-phase arrest), decreased MMP-2 and MMP-9 (reducing metastasis). Conversely, FOXO1 overexpression enhances ARHGAP15 expression and promoter activity, indicating a regulatory feedback loop. PTEN upregulation, FOXO1 overexpression, or AKT inhibition (MK2206) suppressed proliferation and metastasis in ARHGAP15-silenced cells.","method":"Overexpression and siRNA knockdown in CRC cell lines, Western blot, GSEA, luciferase promoter assay, in vivo xenograft/lung metastasis model, pharmacological AKT inhibition","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (promoter assay, pharmacological rescue, in vivo model) in single lab; pathway placement via epistasis-like rescue experiments","pmids":["29867200"],"is_preprint":false},{"year":2018,"finding":"ARHGAP15 overexpression suppresses cell proliferation and migration of breast cancer cell lines (MCF-7 and SK-BR-3). ARHGAP15 mRNA is induced by dihydrotestosterone, identifying it as an androgen-regulated gene, and its protein immunoreactivity positively correlates with Rac1 and androgen receptor expression in breast carcinoma tissues.","method":"Overexpression in breast cancer cell lines, proliferation and migration assays, dihydrotestosterone treatment, immunohistochemistry","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — functional cell assays combined with hormone treatment demonstrating transcriptional induction, single lab","pmids":["29534468"],"is_preprint":false},{"year":2019,"finding":"ARHGAP15 overexpression in lung cancer cells suppresses cell proliferation, migration, and invasion and reduces MMP-2, MMP-9, VEGF expression and STAT3 phosphorylation (p-STAT3). IL-6-induced proliferation and invasion are counteracted by ARHGAP15 upregulation. ARHGAP15 silencing-induced effects are inhibited by the STAT3 inhibitor AG490, placing ARHGAP15 upstream of STAT3 in this pathway.","method":"Overexpression and siRNA knockdown in lung cancer cell lines, proliferation/transwell assays, Western blot, pharmacological STAT3 inhibition (AG490)","journal":"European review for medical and pharmacological sciences","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — pathway placement via pharmacological rescue (STAT3 inhibitor epistasis), single lab with multiple functional readouts","pmids":["31298335"],"is_preprint":false},{"year":2023,"finding":"ARHGAP15 inactivates RAC1, thereby decreasing intracellular reactive oxygen species (ROS) accumulation, which enhances the antioxidant capacity and survival of gastric cancer cells under oxidative stress during metastatic colonization. This pro-colonization phenotype is phenocopied by RAC1 inhibition and rescued by constitutively active RAC1, placing ARHGAP15 upstream of RAC1 in the ROS-regulation pathway.","method":"Ectopic expression and genetic knockdown in gastric cancer cells, in vivo lung/lymph node colonization assay in mice, ROS measurement, RAC1 inhibition and constitutively active RAC1 rescue experiments","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo colonization model, biochemical ROS assay, genetic epistasis with constitutively active RAC1 rescue, multiple orthogonal approaches in single study","pmids":["36802400"],"is_preprint":false},{"year":2013,"finding":"siRNA knockdown of ARHGAP15 in bovine fibroblast cells decreases the Bax/Bcl-2 ratio and caspase-3 levels in ethanol-treated cells, suggesting that ARHGAP15 activity is required for ethanol-induced apoptosis. Loss of ARHGAP15 is protective against ethanol-induced cell death.","method":"siRNA knockdown, RT-PCR, Western blot for Bax, Bcl-2, caspase-3, cell viability assay in ethanol-treated bovine fibroblasts","journal":"Pakistan journal of pharmaceutical sciences","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single-method knockdown with limited mechanistic follow-up, no direct link to GAP activity","pmids":["23625437"],"is_preprint":false}],"current_model":"ARHGAP15 is a Rac1-specific GTPase-activating protein with a PH domain (required for membrane localization), a RhoGAP catalytic domain (specific for Rac1 in vitro), and a novel N-terminal motif that mediates nucleotide-independent Rac1 binding; it plays a dual negative role in small GTPase signaling by both inactivating Rac1 GTP hydrolysis and binding/inhibiting Pak1/2 kinases via its PH domain (while being a Pak1/2 substrate itself); in neurons, it restrains Rac1/Rac3 activity to support inhibitory interneuron migration and hippocampal circuit function; and in multiple cancer contexts it acts as a tumor suppressor by dampening Rac1-driven proliferation and invasion through downstream PTEN/AKT/FOXO1, STAT3, or ROS pathways, with its expression transcriptionally regulated by FOXP3 and androgens."},"narrative":{"mechanistic_narrative":"ARHGAP15 is a Rac1-specific GTPase-activating protein that acts as a dual negative regulator of Rac1 signaling and thereby controls cell motility, proliferation, and circuit assembly [PMID:12650940, PMID:23760270]. It is organized into a PH domain required for membrane/cell-periphery localization, a RhoGAP catalytic domain specific for Rac1 in vitro, and a novel N-terminal motif that mediates nucleotide-independent binding to the C-terminal half of Rac1; full-length expression promotes actin stress fibers and cell contraction in a Rac1-dependent manner [PMID:12650940]. Beyond accelerating Rac1 GTP hydrolysis, ARHGAP15 binds Pak1/2 through its PH domain to produce mutual inhibition — its own GAP activity is suppressed while it blocks Pak1/2 kinase activity — and it is itself a Pak1/2 substrate, so its loss activates Pak1/2 both indirectly via Rac and directly by disrupting the complex [PMID:23760270]. In vivo, loss of ArhGAP15 hyperactivates Rac1/Rac3 and impairs the migration of inhibitory interneurons into the hippocampus, altering excitatory/inhibitory synaptic balance and producing memory deficits [PMID:27713499]. Across multiple epithelial cancers ARHGAP15 behaves as a tumor suppressor by dampening Rac1 activity, restraining proliferation, migration, and invasion through downstream PTEN/AKT/FOXO1 [PMID:29867200], STAT3 [PMID:31298335], and ROS [PMID:36802400] effector arms, with its expression transcriptionally controlled by FOXP3 [PMID:27862679], FOXO1 feedback [PMID:29867200], and androgens [PMID:29534468].","teleology":[{"year":2003,"claim":"Established ARHGAP15 as a Rac1-directed RhoGAP and defined its domain logic, answering what GTPase it regulates and which domains drive binding and localization.","evidence":"In vitro GAP assay, Rac/Cdc42 swop mutants, domain-deletion overexpression, and dominant-negative Rac1 co-expression with cell morphology readouts","pmids":["12650940"],"confidence":"High","gaps":["In vitro Rac1 specificity not tested against the full Rho GTPase panel in cells","Function of the novel N-terminal nucleotide-independent binding motif beyond Rac1 capture unresolved","Structural basis of PH-domain membrane targeting not determined"]},{"year":2013,"claim":"Revealed a second regulatory layer beyond GAP activity by showing ARHGAP15 and Pak1/2 form a mutually inhibitory complex, explaining how ARHGAP15 doubly suppresses Rac effector output.","evidence":"Protein microarray screen, co-immunoprecipitation, reciprocal kinase and GAP activity assays, and siRNA knockdown","pmids":["23760270"],"confidence":"High","gaps":["Phosphosites on ARHGAP15 targeted by Pak1/2 and their functional consequence not mapped","Stoichiometry and structural interface of the PH-domain/Pak association unknown","Physiological contexts where the complex predominates over GAP activity not defined"]},{"year":2013,"claim":"Linked ARHGAP15 to apoptotic sensitivity by showing its knockdown protects against ethanol-induced cell death, raising a possible role in stress-induced apoptosis.","evidence":"siRNA knockdown with Bax/Bcl-2 and caspase-3 readouts and viability assay in ethanol-treated bovine fibroblasts","pmids":["23625437"],"confidence":"Low","gaps":["Single-method knockdown with no rescue and no link to GAP activity","Mechanism connecting ARHGAP15 to apoptotic machinery undefined","Not confirmed in mammalian or human cells"]},{"year":2016,"claim":"Demonstrated the physiological requirement for ArhGAP15 in restraining Rac1/Rac3 during neurodevelopment, connecting GAP activity to interneuron migration and circuit function.","evidence":"ArhGAP15 knockout mouse with Rac activity assays, interneuron migration analysis, electrophysiology, and behavioral testing","pmids":["27713499"],"confidence":"High","gaps":["Cell-autonomous versus circuit-level contributions to migration not separated","Role of Pak inhibition versus Rac GAP activity in the neuronal phenotype unresolved","Selectivity for interneurons over pyramidal neurons unexplained mechanistically"]},{"year":2017,"claim":"Identified FOXP3 as an upstream transcriptional activator of ARHGAP15, placing the GAP in a FOXP3-Rac1-migration axis in glioma.","evidence":"DNA microarray, qRT-PCR, Western blot, IHC, and overexpression/knockdown migration assays in glioma cells","pmids":["27862679"],"confidence":"Medium","gaps":["No direct promoter binding or ChIP evidence reported","Whether regulation is direct or indirect unresolved","Generalizability beyond glioma not tested"]},{"year":2018,"claim":"Wired ARHGAP15 into a PTEN/AKT/FOXO1 tumor-suppressive circuit with a feed-forward loop, explaining how it arrests cell cycle and limits metastasis in colorectal cancer.","evidence":"Overexpression/knockdown in CRC lines, luciferase promoter assay, GSEA, pharmacological AKT inhibition, and xenograft/metastasis models","pmids":["29867200"],"confidence":"Medium","gaps":["Direct FOXO1 binding to the ARHGAP15 promoter not shown","How Rac1 inactivation feeds into PTEN signaling mechanistically undefined","Single-lab pathway placement"]},{"year":2018,"claim":"Established ARHGAP15 as an androgen-regulated, growth-suppressive gene in breast cancer, adding hormonal control to its transcriptional regulation.","evidence":"Overexpression and dihydrotestosterone treatment in breast cancer lines with proliferation/migration assays and tissue IHC correlation","pmids":["29534468"],"confidence":"Medium","gaps":["Direct androgen-receptor binding to the ARHGAP15 locus not demonstrated","Mechanism coupling AR signaling to ARHGAP15 induction unknown","Functional consequence of AR/Rac1/ARHGAP15 co-expression in vivo not tested"]},{"year":2019,"claim":"Positioned ARHGAP15 upstream of STAT3 in lung cancer, broadening its tumor-suppressive output to an IL-6/STAT3 invasion axis.","evidence":"Overexpression/knockdown, transwell assays, Western blot, and STAT3 inhibitor (AG490) epistasis in lung cancer cells","pmids":["31298335"],"confidence":"Medium","gaps":["Mechanistic link from Rac1 inactivation to STAT3 dephosphorylation not defined","Pharmacological epistasis only, no genetic STAT3 manipulation","Single-lab study"]},{"year":2023,"claim":"Uncovered a redox dimension showing ARHGAP15 lowers RAC1-driven ROS to enhance cancer cell survival during metastatic colonization, refining its context-dependent role.","evidence":"Ectopic expression/knockdown, in vivo colonization assay, ROS measurement, and constitutively active RAC1 rescue in gastric cancer","pmids":["36802400"],"confidence":"High","gaps":["Source of Rac1-dependent ROS in this setting not identified","Reconciliation of pro-survival colonization role with tumor-suppressor role in other cancers incomplete","Downstream antioxidant effectors not mapped"]},{"year":null,"claim":"How ARHGAP15's two negative functions — Rac1 GAP activity and Pak1/2 sequestration — are balanced and switched across neuronal, epithelial, and metastatic contexts remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of the autoinhibitory ARHGAP15/Pak complex or PH-domain membrane engagement","Phosphoregulation by Pak1/2 not functionally mapped","Context-dependent tumor-suppressor versus pro-survival switch mechanistically unexplained"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,2]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[1]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[4,6,7]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[2]}],"complexes":[],"partners":["RAC1","PAK1","PAK2","RAC3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q53QZ3","full_name":"Rho GTPase-activating protein 15","aliases":["ArhGAP15","Rho-type GTPase-activating protein 15"],"length_aa":475,"mass_kda":54.5,"function":"GTPase activator for the Rho-type GTPases by converting them to an inactive GDP-bound state. Has activity toward RAC1. Overexpression results in an increase in actin stress fibers and cell contraction","subcellular_location":"Cytoplasm; Membrane","url":"https://www.uniprot.org/uniprotkb/Q53QZ3/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ARHGAP15","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"EDC4","stoichiometry":0.2},{"gene":"ESYT1","stoichiometry":0.2},{"gene":"BCAP31","stoichiometry":0.2},{"gene":"PGRMC1","stoichiometry":0.2},{"gene":"SCD","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/ARHGAP15","total_profiled":1310},"omim":[{"mim_id":"610578","title":"RHO GTPase-ACTIVATING PROTEIN 15; ARHGAP15","url":"https://www.omim.org/entry/610578"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Plasma membrane","reliability":"Supported"}],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"bone marrow","ntpm":75.1},{"tissue":"lymphoid tissue","ntpm":70.0}],"url":"https://www.proteinatlas.org/search/ARHGAP15"},"hgnc":{"alias_symbol":["BM046"],"prev_symbol":[]},"alphafold":{"accession":"Q53QZ3","domains":[{"cath_id":"2.30.29.30","chopping":"81-191","consensus_level":"high","plddt":83.7882,"start":81,"end":191},{"cath_id":"1.10.555.10","chopping":"284-471","consensus_level":"high","plddt":94.8222,"start":284,"end":471}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q53QZ3","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q53QZ3-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q53QZ3-F1-predicted_aligned_error_v6.png","plddt_mean":76.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ARHGAP15","jax_strain_url":"https://www.jax.org/strain/search?query=ARHGAP15"},"sequence":{"accession":"Q53QZ3","fasta_url":"https://rest.uniprot.org/uniprotkb/Q53QZ3.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q53QZ3/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q53QZ3"}},"corpus_meta":[{"pmid":"28585551","id":"PMC_28585551","title":"Sequence variants in ARHGAP15, COLQ and FAM155A associate with diverticular disease and diverticulitis.","date":"2017","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/28585551","citation_count":69,"is_preprint":false},{"pmid":"12650940","id":"PMC_12650940","title":"ArhGAP15, a novel human RacGAP protein with GTPase binding property.","date":"2003","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/12650940","citation_count":59,"is_preprint":false},{"pmid":"29867200","id":"PMC_29867200","title":"Decreased expression of ARHGAP15 promotes the development of colorectal cancer through PTEN/AKT/FOXO1 axis.","date":"2018","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/29867200","citation_count":32,"is_preprint":false},{"pmid":"27713499","id":"PMC_27713499","title":"Disruption of ArhGAP15 results in hyperactive Rac1, affects the architecture and function of hippocampal inhibitory neurons and causes cognitive deficits.","date":"2016","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/27713499","citation_count":31,"is_preprint":false},{"pmid":"29534468","id":"PMC_29534468","title":"ARHGAP15 in Human Breast Carcinoma: A Potent Tumor Suppressor Regulated by Androgens.","date":"2018","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/29534468","citation_count":26,"is_preprint":false},{"pmid":"23760270","id":"PMC_23760270","title":"ArhGAP15, a Rac-specific GTPase-activating protein, plays a dual role in inhibiting small GTPase signaling.","date":"2013","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/23760270","citation_count":24,"is_preprint":false},{"pmid":"27862679","id":"PMC_27862679","title":"Forkhead box P3 regulates ARHGAP15 expression and affects migration of glioma cells through the Rac1 signaling pathway.","date":"2017","source":"Cancer science","url":"https://pubmed.ncbi.nlm.nih.gov/27862679","citation_count":21,"is_preprint":false},{"pmid":"31298335","id":"PMC_31298335","title":"ARHGAP15 regulates lung cancer cell proliferation and metastasis via the STAT3 pathway.","date":"2019","source":"European review for medical and pharmacological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/31298335","citation_count":11,"is_preprint":false},{"pmid":"36802400","id":"PMC_36802400","title":"ARHGAP15 promotes metastatic colonization in gastric cancer by suppressing RAC1-ROS pathway.","date":"2023","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/36802400","citation_count":9,"is_preprint":false},{"pmid":"26515718","id":"PMC_26515718","title":"African Cattle do not Carry Unique Mutations on the Exon 9 of the ARHGAP15 Gene.","date":"2016","source":"Animal biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/26515718","citation_count":8,"is_preprint":false},{"pmid":"34225052","id":"PMC_34225052","title":"COLQ and ARHGAP15 are Associated with Diverticular Disease and are Expressed in the Colon.","date":"2021","source":"The Journal of surgical research","url":"https://pubmed.ncbi.nlm.nih.gov/34225052","citation_count":6,"is_preprint":false},{"pmid":"23625437","id":"PMC_23625437","title":"Rho GTPase activating protein 15 (arhGAP15) siRNA effect apoptosis-induced by ethanol in bovine fibroblast cells.","date":"2013","source":"Pakistan journal of pharmaceutical sciences","url":"https://pubmed.ncbi.nlm.nih.gov/23625437","citation_count":5,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.07.26.605344","title":"Whole genome sequencing of 76 Mexican Indigenous reveals recent selection signatures linked to pathogens and diet adaptation","date":"2024-07-29","source":"bioRxiv","url":"https://doi.org/10.1101/2024.07.26.605344","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8523,"output_tokens":2864,"usd":0.034265,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10196,"output_tokens":3511,"usd":0.069377,"stage2_stop_reason":"end_turn"},"total_usd":0.103642,"stage1_batch_id":"msgbatch_0179Z2pxRYBsXi2xADneafRw","stage2_batch_id":"msgbatch_01LaY9ZaVdgjWArcZo9eqQE5","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2003,\n      \"finding\": \"ARHGAP15 contains a pleckstrin homology (PH) domain, a RhoGAP domain, and a novel motif N-terminal to the GAP domain. The novel motif mediates nucleotide-independent Rac1 binding through the C-terminal half of Rac1 (established by swop mutants of Rac/Cdc42). The GAP domain shows specificity towards Rac1 in vitro. The PH domain is required for membrane/cell-periphery localization. Overexpression of full-length ARHGAP15 (but not PH-domain deletion mutant) increases actin stress fibers and cell contraction, effects attenuated by co-expression of dominant-negative Rac1(N17). ARHGAP15-expressing HeLa cells are resistant to phorbol myristate acetate treatment.\",\n      \"method\": \"In vitro GAP activity assay, Rac/Cdc42 swop mutants, overexpression/deletion constructs, co-expression with dominant-negative Rac1, cell morphology analysis, PMA treatment assay\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro GAP assay, domain-deletion mutagenesis, and genetic rescue with dominant-negative Rac1 in one study with multiple orthogonal methods\",\n      \"pmids\": [\"12650940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"ARHGAP15 serves as a substrate of Rac effectors Pak1 and Pak2 (identified by protein microarray screen). ARHGAP15 also binds Pak1/2 via its PH domain. The ArhGAP15–Pak1/2 association results in mutual inhibition: ARHGAP15 GAP activity is inhibited and Pak1/2 kinase activity is inhibited. Knockdown of ARHGAP15 activates Pak1/2 both indirectly (through Rac activation) and directly (by disrupting the ARHGAP15/Pak complex), indicating a dual negative regulatory role.\",\n      \"method\": \"Protein microarray screen, co-immunoprecipitation, kinase activity assay, GAP activity assay, siRNA knockdown\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — protein microarray identification, biochemical kinase/GAP activity assays, and reciprocal interaction studies with knockdown validation in one study\",\n      \"pmids\": [\"23760270\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Loss of ArhGAP15 in mice results in hyperactivation of Rac1/Rac3. In the hippocampus, ArhGAP15 knockout reduces the number of CR+, PV+, and SST+ inhibitory interneurons in CA3 and dentate gyrus due to reduced efficiency and directionality of their migration (pyramidal neurons are unaffected). Loss of ArhGAP15 alters neuritogenesis and the balance between excitatory and inhibitory synapses, resulting in increased spike frequency and bursts with poor synchronization. Adult ArhGAP15-/- mice show defective hippocampus-dependent working and associative memory.\",\n      \"method\": \"ArhGAP15 knockout mouse model, Rac1/Rac3 activity assays, interneuron counting and migration analysis, electrophysiology, behavioral testing\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout with multiple orthogonal readouts (biochemical Rac activity, cellular migration, electrophysiology, behavior) in a single study\",\n      \"pmids\": [\"27713499\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"FOXP3 transcriptionally regulates ARHGAP15 expression. Overexpression of FOXP3 upregulates ARHGAP15, which inactivates Rac1, inhibiting glioma cell migration. Silencing FOXP3 downregulates ARHGAP15 and activates Rac1, promoting migration. FOXP3 also regulates EMT markers E-cadherin and N-cadherin in this context.\",\n      \"method\": \"DNA microarray, qRT-PCR, Western blot, immunohistochemistry, overexpression and siRNA knockdown in glioma cells, migration assays\",\n      \"journal\": \"Cancer science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — overexpression and knockdown with multiple readouts in a single lab, but no direct promoter binding or ChIP assay reported in abstract\",\n      \"pmids\": [\"27862679\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"In colorectal cancer cells, ARHGAP15 overexpression activates PTEN signaling, increases FOXO1 activity, and decreases AKT phosphorylation. This leads to increased p21 (causing S-phase arrest), decreased MMP-2 and MMP-9 (reducing metastasis). Conversely, FOXO1 overexpression enhances ARHGAP15 expression and promoter activity, indicating a regulatory feedback loop. PTEN upregulation, FOXO1 overexpression, or AKT inhibition (MK2206) suppressed proliferation and metastasis in ARHGAP15-silenced cells.\",\n      \"method\": \"Overexpression and siRNA knockdown in CRC cell lines, Western blot, GSEA, luciferase promoter assay, in vivo xenograft/lung metastasis model, pharmacological AKT inhibition\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (promoter assay, pharmacological rescue, in vivo model) in single lab; pathway placement via epistasis-like rescue experiments\",\n      \"pmids\": [\"29867200\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"ARHGAP15 overexpression suppresses cell proliferation and migration of breast cancer cell lines (MCF-7 and SK-BR-3). ARHGAP15 mRNA is induced by dihydrotestosterone, identifying it as an androgen-regulated gene, and its protein immunoreactivity positively correlates with Rac1 and androgen receptor expression in breast carcinoma tissues.\",\n      \"method\": \"Overexpression in breast cancer cell lines, proliferation and migration assays, dihydrotestosterone treatment, immunohistochemistry\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — functional cell assays combined with hormone treatment demonstrating transcriptional induction, single lab\",\n      \"pmids\": [\"29534468\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"ARHGAP15 overexpression in lung cancer cells suppresses cell proliferation, migration, and invasion and reduces MMP-2, MMP-9, VEGF expression and STAT3 phosphorylation (p-STAT3). IL-6-induced proliferation and invasion are counteracted by ARHGAP15 upregulation. ARHGAP15 silencing-induced effects are inhibited by the STAT3 inhibitor AG490, placing ARHGAP15 upstream of STAT3 in this pathway.\",\n      \"method\": \"Overexpression and siRNA knockdown in lung cancer cell lines, proliferation/transwell assays, Western blot, pharmacological STAT3 inhibition (AG490)\",\n      \"journal\": \"European review for medical and pharmacological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — pathway placement via pharmacological rescue (STAT3 inhibitor epistasis), single lab with multiple functional readouts\",\n      \"pmids\": [\"31298335\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"ARHGAP15 inactivates RAC1, thereby decreasing intracellular reactive oxygen species (ROS) accumulation, which enhances the antioxidant capacity and survival of gastric cancer cells under oxidative stress during metastatic colonization. This pro-colonization phenotype is phenocopied by RAC1 inhibition and rescued by constitutively active RAC1, placing ARHGAP15 upstream of RAC1 in the ROS-regulation pathway.\",\n      \"method\": \"Ectopic expression and genetic knockdown in gastric cancer cells, in vivo lung/lymph node colonization assay in mice, ROS measurement, RAC1 inhibition and constitutively active RAC1 rescue experiments\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo colonization model, biochemical ROS assay, genetic epistasis with constitutively active RAC1 rescue, multiple orthogonal approaches in single study\",\n      \"pmids\": [\"36802400\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"siRNA knockdown of ARHGAP15 in bovine fibroblast cells decreases the Bax/Bcl-2 ratio and caspase-3 levels in ethanol-treated cells, suggesting that ARHGAP15 activity is required for ethanol-induced apoptosis. Loss of ARHGAP15 is protective against ethanol-induced cell death.\",\n      \"method\": \"siRNA knockdown, RT-PCR, Western blot for Bax, Bcl-2, caspase-3, cell viability assay in ethanol-treated bovine fibroblasts\",\n      \"journal\": \"Pakistan journal of pharmaceutical sciences\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single-method knockdown with limited mechanistic follow-up, no direct link to GAP activity\",\n      \"pmids\": [\"23625437\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ARHGAP15 is a Rac1-specific GTPase-activating protein with a PH domain (required for membrane localization), a RhoGAP catalytic domain (specific for Rac1 in vitro), and a novel N-terminal motif that mediates nucleotide-independent Rac1 binding; it plays a dual negative role in small GTPase signaling by both inactivating Rac1 GTP hydrolysis and binding/inhibiting Pak1/2 kinases via its PH domain (while being a Pak1/2 substrate itself); in neurons, it restrains Rac1/Rac3 activity to support inhibitory interneuron migration and hippocampal circuit function; and in multiple cancer contexts it acts as a tumor suppressor by dampening Rac1-driven proliferation and invasion through downstream PTEN/AKT/FOXO1, STAT3, or ROS pathways, with its expression transcriptionally regulated by FOXP3 and androgens.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ARHGAP15 is a Rac1-specific GTPase-activating protein that acts as a dual negative regulator of Rac1 signaling and thereby controls cell motility, proliferation, and circuit assembly [#0, #1]. It is organized into a PH domain required for membrane/cell-periphery localization, a RhoGAP catalytic domain specific for Rac1 in vitro, and a novel N-terminal motif that mediates nucleotide-independent binding to the C-terminal half of Rac1; full-length expression promotes actin stress fibers and cell contraction in a Rac1-dependent manner [#0]. Beyond accelerating Rac1 GTP hydrolysis, ARHGAP15 binds Pak1/2 through its PH domain to produce mutual inhibition — its own GAP activity is suppressed while it blocks Pak1/2 kinase activity — and it is itself a Pak1/2 substrate, so its loss activates Pak1/2 both indirectly via Rac and directly by disrupting the complex [#1]. In vivo, loss of ArhGAP15 hyperactivates Rac1/Rac3 and impairs the migration of inhibitory interneurons into the hippocampus, altering excitatory/inhibitory synaptic balance and producing memory deficits [#2]. Across multiple epithelial cancers ARHGAP15 behaves as a tumor suppressor by dampening Rac1 activity, restraining proliferation, migration, and invasion through downstream PTEN/AKT/FOXO1 [#4], STAT3 [#6], and ROS [#7] effector arms, with its expression transcriptionally controlled by FOXP3 [#3], FOXO1 feedback [#4], and androgens [#5].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Established ARHGAP15 as a Rac1-directed RhoGAP and defined its domain logic, answering what GTPase it regulates and which domains drive binding and localization.\",\n      \"evidence\": \"In vitro GAP assay, Rac/Cdc42 swop mutants, domain-deletion overexpression, and dominant-negative Rac1 co-expression with cell morphology readouts\",\n      \"pmids\": [\"12650940\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vitro Rac1 specificity not tested against the full Rho GTPase panel in cells\", \"Function of the novel N-terminal nucleotide-independent binding motif beyond Rac1 capture unresolved\", \"Structural basis of PH-domain membrane targeting not determined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Revealed a second regulatory layer beyond GAP activity by showing ARHGAP15 and Pak1/2 form a mutually inhibitory complex, explaining how ARHGAP15 doubly suppresses Rac effector output.\",\n      \"evidence\": \"Protein microarray screen, co-immunoprecipitation, reciprocal kinase and GAP activity assays, and siRNA knockdown\",\n      \"pmids\": [\"23760270\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Phosphosites on ARHGAP15 targeted by Pak1/2 and their functional consequence not mapped\", \"Stoichiometry and structural interface of the PH-domain/Pak association unknown\", \"Physiological contexts where the complex predominates over GAP activity not defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Linked ARHGAP15 to apoptotic sensitivity by showing its knockdown protects against ethanol-induced cell death, raising a possible role in stress-induced apoptosis.\",\n      \"evidence\": \"siRNA knockdown with Bax/Bcl-2 and caspase-3 readouts and viability assay in ethanol-treated bovine fibroblasts\",\n      \"pmids\": [\"23625437\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single-method knockdown with no rescue and no link to GAP activity\", \"Mechanism connecting ARHGAP15 to apoptotic machinery undefined\", \"Not confirmed in mammalian or human cells\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstrated the physiological requirement for ArhGAP15 in restraining Rac1/Rac3 during neurodevelopment, connecting GAP activity to interneuron migration and circuit function.\",\n      \"evidence\": \"ArhGAP15 knockout mouse with Rac activity assays, interneuron migration analysis, electrophysiology, and behavioral testing\",\n      \"pmids\": [\"27713499\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cell-autonomous versus circuit-level contributions to migration not separated\", \"Role of Pak inhibition versus Rac GAP activity in the neuronal phenotype unresolved\", \"Selectivity for interneurons over pyramidal neurons unexplained mechanistically\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identified FOXP3 as an upstream transcriptional activator of ARHGAP15, placing the GAP in a FOXP3-Rac1-migration axis in glioma.\",\n      \"evidence\": \"DNA microarray, qRT-PCR, Western blot, IHC, and overexpression/knockdown migration assays in glioma cells\",\n      \"pmids\": [\"27862679\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct promoter binding or ChIP evidence reported\", \"Whether regulation is direct or indirect unresolved\", \"Generalizability beyond glioma not tested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Wired ARHGAP15 into a PTEN/AKT/FOXO1 tumor-suppressive circuit with a feed-forward loop, explaining how it arrests cell cycle and limits metastasis in colorectal cancer.\",\n      \"evidence\": \"Overexpression/knockdown in CRC lines, luciferase promoter assay, GSEA, pharmacological AKT inhibition, and xenograft/metastasis models\",\n      \"pmids\": [\"29867200\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct FOXO1 binding to the ARHGAP15 promoter not shown\", \"How Rac1 inactivation feeds into PTEN signaling mechanistically undefined\", \"Single-lab pathway placement\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Established ARHGAP15 as an androgen-regulated, growth-suppressive gene in breast cancer, adding hormonal control to its transcriptional regulation.\",\n      \"evidence\": \"Overexpression and dihydrotestosterone treatment in breast cancer lines with proliferation/migration assays and tissue IHC correlation\",\n      \"pmids\": [\"29534468\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct androgen-receptor binding to the ARHGAP15 locus not demonstrated\", \"Mechanism coupling AR signaling to ARHGAP15 induction unknown\", \"Functional consequence of AR/Rac1/ARHGAP15 co-expression in vivo not tested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Positioned ARHGAP15 upstream of STAT3 in lung cancer, broadening its tumor-suppressive output to an IL-6/STAT3 invasion axis.\",\n      \"evidence\": \"Overexpression/knockdown, transwell assays, Western blot, and STAT3 inhibitor (AG490) epistasis in lung cancer cells\",\n      \"pmids\": [\"31298335\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic link from Rac1 inactivation to STAT3 dephosphorylation not defined\", \"Pharmacological epistasis only, no genetic STAT3 manipulation\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Uncovered a redox dimension showing ARHGAP15 lowers RAC1-driven ROS to enhance cancer cell survival during metastatic colonization, refining its context-dependent role.\",\n      \"evidence\": \"Ectopic expression/knockdown, in vivo colonization assay, ROS measurement, and constitutively active RAC1 rescue in gastric cancer\",\n      \"pmids\": [\"36802400\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Source of Rac1-dependent ROS in this setting not identified\", \"Reconciliation of pro-survival colonization role with tumor-suppressor role in other cancers incomplete\", \"Downstream antioxidant effectors not mapped\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How ARHGAP15's two negative functions — Rac1 GAP activity and Pak1/2 sequestration — are balanced and switched across neuronal, epithelial, and metastatic contexts remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of the autoinhibitory ARHGAP15/Pak complex or PH-domain membrane engagement\", \"Phosphoregulation by Pak1/2 not functionally mapped\", \"Context-dependent tumor-suppressor versus pro-survival switch mechanistically unexplained\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [4, 6, 7]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"RAC1\", \"PAK1\", \"PAK2\", \"RAC3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"tie","faith_supported":5,"faith_total":5,"faith_pct":100.0}}