{"gene":"ARHGEF18","run_date":"2026-04-28T17:12:37","timeline":{"discoveries":[{"year":2011,"finding":"p114RhoGEF (ARHGEF18) is a junction-associated RhoA GEF that drives spatially restricted RhoA activation at epithelial junctions, regulates tight-junction assembly and epithelial morphogenesis, and associates with a complex containing myosin II, ROCK II, and the junctional adaptor cingulin.","method":"RNAi knockdown, Co-immunoprecipitation, RhoA activation assays, live imaging, myosin phosphorylation readouts","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, KD with defined cellular phenotype, replicated across multiple orthogonal assays in a highly-cited study","pmids":["21258369"],"is_preprint":false},{"year":2003,"finding":"Gβγ subunits of heterotrimeric G proteins interact with the full-length and DH/PH domain of p114RhoGEF and stimulate its GEF activity toward RhoA and Rac1 (but not Cdc42), leading to actin stress fiber formation and ROS production via NADPH oxidase.","method":"Co-immunoprecipitation, in vivo pull-down assays, dominant-negative mutants, SRE reporter assays, Gβγ scavenger (transducin)","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (Co-IP, pull-down, dominant-negative, reporter), moderate evidence","pmids":["14512443"],"is_preprint":false},{"year":2011,"finding":"Lulu2 (a FERM-domain protein) directly interacts with and activates p114RhoGEF at apical cell-cell junctions to regulate the circumferential actomyosin belt; this interaction is negatively regulated by aPKC-mediated phosphorylation of the FERM-adjacent domain of Lulu2. Additionally, Patj recruits p114RhoGEF to apical cell-cell boundaries via PDZ domain-mediated interaction.","method":"Co-immunoprecipitation, RNAi knockdown, GEF activity assays, phosphorylation experiments, domain mapping","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 — direct interaction plus GEF activation assay, upstream regulation by phosphorylation identified, multiple orthogonal methods","pmids":["22006950"],"is_preprint":false},{"year":2013,"finding":"ArhGEF18-mediated activation of RhoA is required to maintain apicobasal polarity in the vertebrate retinal neuroepithelium; RhoA signals through Rock2 to regulate tight junction localization and cortical actin. Loss of ArhGEF18 increases proliferation and reduces cell cycle exit. Human ARHGEF18 rescues the medaka mutant phenotype.","method":"Genetic mutation in medaka fish, rescue with human ARHGEF18, immunostaining, RhoA activity assays","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 — in vivo genetic loss-of-function with defined phenotype, pathway placement (RhoA-Rock2), cross-species rescue","pmids":["23698346"],"is_preprint":false},{"year":2013,"finding":"LKB1 interacts with p114RhoGEF in a kinase-activity-independent manner to control RhoA activity at apical junctions and promote apical junction assembly in human bronchial epithelial cells.","method":"Co-immunoprecipitation, kinase-dead LKB1 mutant, RhoA activation assays, RNAi knockdown","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP plus functional KD phenotype, single lab","pmids":["23648482"],"is_preprint":false},{"year":2010,"finding":"p114-RhoGEF is required for Wnt-3a- and Dishevelled-induced RhoA activation and neurite retraction in neuroblastoma cells; p114-RhoGEF physically interacts with Dvl and Daam1, and its Dvl-binding domain acts as a dominant-negative inhibitor of Dvl-induced neurite retraction.","method":"shRNA screening, RhoA activation assays, Co-immunoprecipitation, dominant-negative domain constructs","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 — multiple methods (Co-IP, KD, dominant-negative), single lab","pmids":["20810787"],"is_preprint":false},{"year":2012,"finding":"p114RhoGEF drives cortical myosin activation specifically by stimulating myosin light chain double phosphorylation (not single phosphorylation) at cell-cell contacts in migrating epithelial sheets and at the cortex of single migrating cells, promoting collective cell migration and amoeboid-like tumor cell invasion; depletion reduces RhoA but increases Rac activity.","method":"RNAi knockdown, myosin phosphorylation assays (mono- vs. double-phospho MLC), Matrigel invasion assay, RhoA/Rac pull-down assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — KD with specific phosphorylation readout and pathway placement, single lab","pmids":["23185572"],"is_preprint":false},{"year":2015,"finding":"p114RhoGEF knockdown impairs late-stage tubulogenesis (lumen consolidation) in HGF-stimulated MDCK cells by blocking cell movement; ROCK and myosin IIA act downstream of p114RhoGEF-RhoA in this pathway.","method":"RNAi knockdown, ROCK/myosin IIA inhibitors, live-cell imaging of tubulogenesis","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis with inhibitors, live imaging with defined phenotype, single lab","pmids":["26483385"],"is_preprint":false},{"year":2015,"finding":"CRB3A recruits p114RhoGEF and its activator Ehm2 to the cell periphery via its cytoplasmic tail motifs, increasing RhoA activation; ROCK1/2 act downstream to remodel the cytoskeleton and drive circumferential actomyosin belt formation and cell shape change in HeLa cells.","method":"Co-immunoprecipitation, domain mutants of CRB3A cytoplasmic tail, RhoA activation assays, ROCK inhibitors, immunofluorescence","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP with domain mapping plus functional pathway placement, single lab","pmids":["26217016"],"is_preprint":false},{"year":2016,"finding":"p114RhoGEF contains a C-terminal region that specifically binds Gα12 (but not Gα13) independently of the canonical RGS-homology domain mechanism; charge-reversal mutagenesis of conserved residues disrupts Gα12 binding, and dominant-negative Gα12 suppresses serum-mediated signaling through p114RhoGEF in cells.","method":"Co-immunoprecipitation, chimeric Gα12/13 constructs, charge-reversal mutagenesis, dominant-negative Gα constructs","journal":"Journal of molecular signaling","confidence":"Medium","confidence_rationale":"Tier 2 — mutagenesis plus Co-IP with chimeric G proteins, single lab","pmids":["31051012"],"is_preprint":false},{"year":2017,"finding":"The p.Thr270Ala missense variant in the DH homology domain of ARHGEF18 (found in patients with adult-onset retinal degeneration) affects a conserved residue required for interaction with and activation of RhoA, supporting the DH domain as the catalytic interface for RhoA activation.","method":"Human genetics (biallelic mutations), functional inference from domain analysis of missense variant","journal":"American journal of human genetics","confidence":"Low","confidence_rationale":"Tier 4 — functional interpretation of human variant, no direct biochemical reconstitution reported in this paper","pmids":["28132693"],"is_preprint":false},{"year":2021,"finding":"p114RhoGEF/ARHGEF18 is required for mouse syncytiotrophoblast differentiation and placenta development: it controls expression of AKAP12, is required for PKA-induced actomyosin remodeling, and promotes CREB-driven gene expression necessary for trophoblast cell-cell fusion.","method":"In vitro trophoblast differentiation assays, in vivo mouse knockouts, PKA signaling assays, CREB reporter assays, AKAP12 expression analysis","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo KO with defined cellular phenotype plus in vitro mechanistic follow-up, single lab","pmids":["33842485"],"is_preprint":false},{"year":2018,"finding":"Eosinophils express novel N-terminally extended isoforms of ARHGEF18 (LOCGEF-X3/X4/X5) from an alternative transcriptional start site; upon activation (IL5, CCL11, or IL33), LOCGEF and RHOA relocalize from the cell periphery to the two poles of polarized eosinophils, implicating LOCGEF in polarity control in leukocytes.","method":"RT-PCR, molecular cloning, immunoblot, immunostaining, recombinant protein expression","journal":"Journal of leukocyte biology","confidence":"Low","confidence_rationale":"Tier 3 — localization and isoform identification without direct functional mechanistic assay","pmids":["29601110"],"is_preprint":false},{"year":2025,"finding":"SEPTIN9 is present at mitochondrial fission sites from early stages and activates ARHGEF18 locally through an isoform-specific N-terminal interaction; SEPTIN9-dependent ARHGEF18 activation is required for mitochondrial calcium influx at early fission steps, upstream of DRP1 recruitment.","method":"Live-cell imaging, Co-immunoprecipitation, siRNA knockdown, mitochondrial calcium assays, DRP1 localization","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP plus live imaging plus functional calcium assay, single lab","pmids":["40920138"],"is_preprint":false},{"year":2025,"finding":"ARHGEF18 is phosphorylated in response to shear stress in endothelial cells; when phosphorylated, it interacts with tight junctions and promotes EC elongation, alignment, migration, and maintenance of the endothelial barrier. In vivo, ARHGEF18 controls tight junction formation, EC flow response, and vascular permeability.","method":"Phosphorylation assays, Co-immunoprecipitation with tight junction proteins, RNAi/KO in mice, vascular permeability assays, live imaging","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo KO with defined phenotype plus biochemical phosphorylation-interaction link, single lab","pmids":["39977269"],"is_preprint":false},{"year":2025,"finding":"Conditional knockout of Arhgef18 in Müller glial cells disrupts the retinal outer limiting membrane (OLM) adherens junctions and leads to progressive retinal degeneration; ARHGEF18 depletion activates NF-κB, β-catenin, and TBK1 signaling and reduces mitochondrial activity; TBK1 inhibition or nicotinamide rescues these defects.","method":"Conditional KO mouse (Müller-specific), cell culture knockdown, OLM protein immunostaining, NF-κB/β-catenin/TBK1 activity assays, mitochondrial activity assays, pharmacological rescue","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo conditional KO with mechanistic pathway follow-up and pharmacological rescue, preprint","pmids":["bio_10.1101_2025.10.07.680916"],"is_preprint":true}],"current_model":"ARHGEF18/p114RhoGEF is a DH/PH-domain RhoGEF that is activated by upstream signals including Gβγ subunits, Gα12, Lulu2, and SEPTIN9 to catalyze guanine nucleotide exchange on RhoA (and Rac1) at spatially defined cellular compartments—including epithelial tight/adherens junctions, the circumferential actomyosin belt, endothelial tight junctions, and mitochondrial fission sites—where it engages complexes with myosin II, ROCK II, cingulin, Patj, and LKB1 to drive junction assembly, actomyosin contractility, cell polarity, tubulogenesis, cell migration, and mitochondrial fission, with phosphorylation events (by aPKC and shear-stress-induced kinases) regulating its activity and localization."},"narrative":{"teleology":[{"year":2003,"claim":"Establishing ARHGEF18 as a Gβγ-responsive RhoGEF resolved how heterotrimeric G protein signaling activates RhoA and Rac1 to induce stress fibers and ROS production.","evidence":"Co-IP, pull-down, dominant-negative mutants, and SRE reporter assays in mammalian cells","pmids":["14512443"],"confidence":"High","gaps":["Direct GEF kinetics with purified Gβγ and RhoA not reported","Relative contribution to Rac1 vs. RhoA activation in physiological settings unclear"]},{"year":2010,"claim":"Linking ARHGEF18 to Wnt/PCP signaling via Dishevelled and Daam1 revealed how non-canonical Wnt signals funnel through a specific GEF to activate RhoA and drive neurite retraction.","evidence":"shRNA screen, Co-IP with Dvl and Daam1, dominant-negative domain constructs in neuroblastoma cells","pmids":["20810787"],"confidence":"Medium","gaps":["Whether this Dvl–ARHGEF18 axis operates in non-neuronal PCP contexts not tested","Direct binding interface between Dvl and ARHGEF18 not mapped"]},{"year":2011,"claim":"Demonstrating that ARHGEF18 localizes to epithelial junctions and drives spatially restricted RhoA activation in complex with myosin II, ROCK II, and cingulin established it as the principal junctional RhoGEF controlling tight junction assembly and epithelial morphogenesis.","evidence":"RNAi, reciprocal Co-IP, RhoA activation assays, live imaging in epithelial cells; parallel study showed Lulu2-mediated activation and aPKC-dependent negative regulation at apical junctions","pmids":["21258369","22006950"],"confidence":"High","gaps":["Crystal structure of ARHGEF18–cingulin or ARHGEF18–Lulu2 complex unavailable","Whether ARHGEF18 directly binds ROCK II or association is indirect through RhoA not resolved"]},{"year":2013,"claim":"Genetic loss-of-function in medaka and interaction studies with LKB1 extended the junctional RhoGEF model in vivo, showing ARHGEF18 is essential for retinal neuroepithelial polarity, tight junction integrity, and cell cycle regulation, with LKB1 acting as a kinase-independent scaffold.","evidence":"Medaka mutant rescued by human ARHGEF18, immunostaining, RhoA assays; Co-IP of LKB1 with kinase-dead mutant in bronchial epithelial cells","pmids":["23698346","23648482"],"confidence":"High","gaps":["Mechanism by which ARHGEF18 loss increases proliferation in retinal neuroepithelium not defined","Structural basis of LKB1–ARHGEF18 interaction unknown"]},{"year":2012,"claim":"Showing that ARHGEF18 selectively promotes myosin light chain double-phosphorylation at cell contacts and in single migrating cells clarified its specific contribution to cortical contractility, collective migration, and amoeboid invasion.","evidence":"RNAi, mono- vs. di-phospho-MLC antibodies, Matrigel invasion, RhoA/Rac pull-down","pmids":["23185572"],"confidence":"Medium","gaps":["Which kinase(s) downstream of ROCK mediate double-phosphorylation not identified","Relative contribution of ARHGEF18 vs. other RhoGEFs in invasive migration not compared"]},{"year":2015,"claim":"Placing ARHGEF18 upstream of ROCK and myosin IIA during tubulogenesis and demonstrating CRB3A-mediated recruitment with Ehm2 revealed how polarity determinants spatially engage ARHGEF18 to organize the actomyosin belt.","evidence":"RNAi plus ROCK/myosin IIA inhibitors in MDCK tubulogenesis; Co-IP and domain mutants of CRB3A in HeLa cells","pmids":["26483385","26217016"],"confidence":"Medium","gaps":["Whether Ehm2 directly activates ARHGEF18 catalytic activity or only recruits it not distinguished","Role in in vivo tubulogenesis not confirmed"]},{"year":2016,"claim":"Identifying a non-canonical Gα12-binding region in the ARHGEF18 C-terminus, distinct from classic RGS-domain interactions, expanded the repertoire of heterotrimeric G protein inputs that activate this GEF.","evidence":"Co-IP with chimeric Gα12/13 constructs and charge-reversal mutagenesis","pmids":["31051012"],"confidence":"Medium","gaps":["No crystal structure of Gα12–ARHGEF18 interface","Whether Gα12 and Gβγ act synergistically or independently on ARHGEF18 not tested"]},{"year":2017,"claim":"Discovery of biallelic ARHGEF18 variants (p.Thr270Ala in the DH domain) in patients with retinal degeneration linked the gene to human Mendelian disease and pinpointed a catalytically essential residue.","evidence":"Human genetic analysis of patients with adult-onset retinal degeneration; domain-level functional inference","pmids":["28132693"],"confidence":"Low","gaps":["No direct biochemical reconstitution of T270A variant GEF activity reported in this study","Genotype–phenotype spectrum across additional families not established"]},{"year":2021,"claim":"Demonstrating that ARHGEF18 knockout disrupts syncytiotrophoblast differentiation and placenta development via PKA-dependent actomyosin remodeling and CREB-driven transcription revealed a non-junctional developmental function.","evidence":"Mouse knockout, in vitro trophoblast differentiation, PKA signaling and CREB reporter assays","pmids":["33842485"],"confidence":"Medium","gaps":["How ARHGEF18 controls AKAP12 expression mechanistically not resolved","Whether RhoA is the sole mediator downstream of ARHGEF18 in trophoblast fusion unknown"]},{"year":2025,"claim":"Identification of SEPTIN9 as an activator of ARHGEF18 at mitochondrial fission sites, upstream of calcium influx and DRP1 recruitment, established a new organellar function for this GEF beyond junctions.","evidence":"Live-cell imaging, Co-IP, siRNA, mitochondrial calcium assays in mammalian cells","pmids":["40920138"],"confidence":"Medium","gaps":["Whether ARHGEF18 activates RhoA or another GTPase at mitochondria not definitively shown","Mechanism linking ARHGEF18-dependent signaling to mitochondrial calcium influx not identified"]},{"year":2025,"claim":"Demonstrating shear-stress-induced phosphorylation of ARHGEF18 and its requirement for endothelial tight junction formation, flow-induced alignment, and vascular barrier integrity extended its junctional role to the endothelium in vivo.","evidence":"Phosphorylation assays, Co-IP with TJ proteins, endothelial KO mice, vascular permeability assays","pmids":["39977269"],"confidence":"Medium","gaps":["Identity of the kinase(s) that phosphorylate ARHGEF18 under shear stress not determined","Phosphosite(s) responsible for TJ interaction not mapped"]},{"year":null,"claim":"A full structural understanding of ARHGEF18 in complex with its diverse activators and effectors is lacking, and the relative contributions of RhoA vs. Rac1 activation across its varied cellular contexts remain unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No crystal or cryo-EM structure of ARHGEF18 or any of its complexes","Isoform-specific functions (e.g., eosinophil LOCGEF isoforms) not functionally characterized","Whether ARHGEF18 has catalytic-independent scaffold functions remains untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,2,3,5,6,8,13]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,2,6,8,12,14]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[13]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,2,3,5,8,9,13,14]},{"term_id":"R-HSA-1500931","term_label":"Cell-Cell communication","supporting_discovery_ids":[0,2,3,4,14]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[3,11]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[13]}],"complexes":["p114RhoGEF–myosin II–ROCK II–cingulin junctional complex","Lulu2–p114RhoGEF apical complex","CRB3A–Ehm2–p114RhoGEF polarity complex"],"partners":["RHOA","MYH9","ROCK2","CGN","EPB41L4B","SEPT9","STK11","CRB3"],"other_free_text":[]},"mechanistic_narrative":"ARHGEF18 (p114RhoGEF) is a DH/PH-domain guanine nucleotide exchange factor that catalyzes RhoA activation at spatially defined cellular compartments—epithelial and endothelial tight junctions, the circumferential actomyosin belt, and mitochondrial fission sites—to drive junction assembly, apicobasal polarity, actomyosin contractility, cell migration, and organelle fission [PMID:21258369, PMID:22006950, PMID:40920138]. It is activated by diverse upstream inputs including Gβγ subunits, Gα12, the FERM-domain protein Lulu2, CRB3A/Ehm2, Dishevelled/Daam1, SEPTIN9, and LKB1, with aPKC phosphorylation and shear-stress-induced phosphorylation modulating its localization and activity [PMID:14512443, PMID:31051012, PMID:22006950, PMID:39977269]. Downstream, ARHGEF18-activated RhoA signals through ROCK and myosin II to control myosin light chain double-phosphorylation, cortical contractility, tubulogenesis, syncytiotrophoblast differentiation, and endothelial barrier function [PMID:23185572, PMID:26483385, PMID:33842485, PMID:39977269]. Biallelic loss-of-function variants in ARHGEF18 cause retinal degeneration in humans and animal models, reflecting its essential role in maintaining neuroepithelial polarity and the outer limiting membrane [PMID:28132693, PMID:23698346]."},"prefetch_data":{"uniprot":{"accession":"Q6ZSZ5","full_name":"Rho guanine nucleotide exchange factor 18","aliases":["114 kDa Rho-specific guanine nucleotide exchange factor","p114-Rho-GEF","p114RhoGEF","Septin-associated RhoGEF","SA-RhoGEF"],"length_aa":1361,"mass_kda":151.6,"function":"Acts as a guanine nucleotide exchange factor (GEF) for RhoA GTPases. Its activation induces formation of actin stress fibers. Also acts as a GEF for RAC1, inducing production of reactive oxygen species (ROS). Does not act as a GEF for CDC42. The G protein beta-gamma (Gbetagamma) subunits of heterotrimeric G proteins act as activators, explaining the integrated effects of LPA and other G-protein coupled receptor agonists on actin stress fiber formation, cell shape change and ROS production. Required for EPB41L4B-mediated regulation of the circumferential actomyosin belt in epithelial cells (PubMed:22006950)","subcellular_location":"Cytoplasm; Cytoplasm, cytoskeleton; Cell membrane; Apical cell membrane","url":"https://www.uniprot.org/uniprotkb/Q6ZSZ5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ARHGEF18","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000104880","cell_line_id":"CID000567","localizations":[{"compartment":"cytoplasmic","grade":3}],"interactors":[{"gene":"AKAP13","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000567","total_profiled":1310},"omim":[{"mim_id":"617433","title":"RETINITIS PIGMENTOSA 78; RP78","url":"https://www.omim.org/entry/617433"},{"mim_id":"616432","title":"RHO GUANINE NUCLEOTIDE EXCHANGE FACTOR 18; ARHGEF18","url":"https://www.omim.org/entry/616432"},{"mim_id":"602216","title":"SERINE/THREONINE PROTEIN KINASE 11; STK11","url":"https://www.omim.org/entry/602216"},{"mim_id":"268000","title":"RETINITIS PIGMENTOSA; RP","url":"https://www.omim.org/entry/268000"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"},{"location":"Plasma membrane","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/ARHGEF18"},"hgnc":{"alias_symbol":["P114-RhoGEF","KIAA0521","MGC15913","p114RhoGEF"],"prev_symbol":[]},"alphafold":{"accession":"Q6ZSZ5","domains":[{"cath_id":"1.20.900.10","chopping":"409-649","consensus_level":"medium","plddt":94.576,"start":409,"end":649},{"cath_id":"2.30.29.30","chopping":"664-791","consensus_level":"high","plddt":90.0312,"start":664,"end":791}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q6ZSZ5","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q6ZSZ5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q6ZSZ5-F1-predicted_aligned_error_v6.png","plddt_mean":60.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ARHGEF18","jax_strain_url":"https://www.jax.org/strain/search?query=ARHGEF18"},"sequence":{"accession":"Q6ZSZ5","fasta_url":"https://rest.uniprot.org/uniprotkb/Q6ZSZ5.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q6ZSZ5/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q6ZSZ5"}},"corpus_meta":[{"pmid":"21258369","id":"PMC_21258369","title":"Spatially restricted activation of RhoA signalling at epithelial junctions by p114RhoGEF drives junction formation and morphogenesis.","date":"2011","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/21258369","citation_count":188,"is_preprint":false},{"pmid":"14512443","id":"PMC_14512443","title":"G Protein betagamma subunits stimulate p114RhoGEF, a guanine nucleotide exchange factor for RhoA and Rac1: regulation of cell shape and reactive oxygen species production.","date":"2003","source":"Circulation research","url":"https://pubmed.ncbi.nlm.nih.gov/14512443","citation_count":100,"is_preprint":false},{"pmid":"22006950","id":"PMC_22006950","title":"Lulu2 regulates the circumferential actomyosin tensile system in epithelial cells through p114RhoGEF.","date":"2011","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/22006950","citation_count":77,"is_preprint":false},{"pmid":"23648482","id":"PMC_23648482","title":"LKB1 controls human bronchial epithelial morphogenesis through p114RhoGEF-dependent RhoA activation.","date":"2013","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/23648482","citation_count":39,"is_preprint":false},{"pmid":"20810787","id":"PMC_20810787","title":"Involvement of p114-RhoGEF and Lfc in Wnt-3a- and dishevelled-induced RhoA activation and neurite retraction in N1E-115 mouse neuroblastoma cells.","date":"2010","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/20810787","citation_count":38,"is_preprint":false},{"pmid":"23698346","id":"PMC_23698346","title":"ArhGEF18 regulates RhoA-Rock2 signaling to maintain neuro-epithelial apico-basal polarity and proliferation.","date":"2013","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/23698346","citation_count":33,"is_preprint":false},{"pmid":"23185572","id":"PMC_23185572","title":"Stimulation of cortical myosin phosphorylation by p114RhoGEF drives cell migration and tumor cell invasion.","date":"2012","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23185572","citation_count":30,"is_preprint":false},{"pmid":"28132693","id":"PMC_28132693","title":"Biallelic Mutation of ARHGEF18, Involved in the Determination of Epithelial Apicobasal Polarity, Causes Adult-Onset Retinal Degeneration.","date":"2017","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/28132693","citation_count":25,"is_preprint":false},{"pmid":"26483385","id":"PMC_26483385","title":"p114RhoGEF governs cell motility and lumen formation during tubulogenesis through a ROCK-myosin-II pathway.","date":"2015","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/26483385","citation_count":22,"is_preprint":false},{"pmid":"26217016","id":"PMC_26217016","title":"CRB3A Controls the Morphology and Cohesion of Cancer Cells through Ehm2/p114RhoGEF-Dependent Signaling.","date":"2015","source":"Molecular and cellular 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biology","url":"https://pubmed.ncbi.nlm.nih.gov/29601110","citation_count":3,"is_preprint":false},{"pmid":"38367539","id":"PMC_38367539","title":"ARHGEF18 can promote BVDV NS5B activation of the host NF-κB signaling pathway by combining with the NS5B-palm domain.","date":"2023","source":"Veterinary microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/38367539","citation_count":2,"is_preprint":false},{"pmid":"40625715","id":"PMC_40625715","title":"Establishment and identification of cardiomyocyte arhGEF18 gene conditional knockout mice.","date":"2023","source":"Pediatric discovery","url":"https://pubmed.ncbi.nlm.nih.gov/40625715","citation_count":1,"is_preprint":false},{"pmid":"39977269","id":"PMC_39977269","title":"ARHGEF18 is a flow-responsive exchange factor controlling endothelial tight junctions and vascular leakage.","date":"2025","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/39977269","citation_count":1,"is_preprint":false},{"pmid":"40920138","id":"PMC_40920138","title":"SEPTIN9 locally activates the RhoGEF ARHGEF18 to promote early stages of mitochondrial fission.","date":"2025","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/40920138","citation_count":1,"is_preprint":false},{"pmid":"40159883","id":"PMC_40159883","title":"Establishment and functional studies of a model of cardiomyopathy with cardiomyocyte-specific conditional knockout of Arhgef18.","date":"2025","source":"Disease models & mechanisms","url":"https://pubmed.ncbi.nlm.nih.gov/40159883","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.10.07.680916","title":"<i>Arhgef18</i> is a component of the outer limiting membrane required for retinal homeostasis","date":"2025-10-07","source":"bioRxiv","url":"https://doi.org/10.1101/2025.10.07.680916","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.11.18.624118","title":"Inhibition of GEF-H1-RhoA signaling in inflammation with a stapled peptide mimicry of the RhoA<sup>67-78</sup>helix","date":"2024-11-19","source":"bioRxiv","url":"https://doi.org/10.1101/2024.11.18.624118","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.05.02.25326852","title":"Genetic Heterogeneity and Homogeneity Among Orofacial Cleft Subtypes: Genome-Wide Association Studies in the Cleft Collective","date":"2025-05-03","source":"bioRxiv","url":"https://doi.org/10.1101/2025.05.02.25326852","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":12955,"output_tokens":3800,"usd":0.047933},"stage2":{"model":"claude-opus-4-6","input_tokens":7279,"output_tokens":3174,"usd":0.173618},"total_usd":0.221551,"stage1_batch_id":"msgbatch_01TqNM6p6FsoMBT2jzQTwKBr","stage2_batch_id":"msgbatch_01Ya473eco8sTHbvRymQaU8o","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2011,\n      \"finding\": \"p114RhoGEF (ARHGEF18) is a junction-associated RhoA GEF that drives spatially restricted RhoA activation at epithelial junctions, regulates tight-junction assembly and epithelial morphogenesis, and associates with a complex containing myosin II, ROCK II, and the junctional adaptor cingulin.\",\n      \"method\": \"RNAi knockdown, Co-immunoprecipitation, RhoA activation assays, live imaging, myosin phosphorylation readouts\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, KD with defined cellular phenotype, replicated across multiple orthogonal assays in a highly-cited study\",\n      \"pmids\": [\"21258369\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Gβγ subunits of heterotrimeric G proteins interact with the full-length and DH/PH domain of p114RhoGEF and stimulate its GEF activity toward RhoA and Rac1 (but not Cdc42), leading to actin stress fiber formation and ROS production via NADPH oxidase.\",\n      \"method\": \"Co-immunoprecipitation, in vivo pull-down assays, dominant-negative mutants, SRE reporter assays, Gβγ scavenger (transducin)\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (Co-IP, pull-down, dominant-negative, reporter), moderate evidence\",\n      \"pmids\": [\"14512443\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Lulu2 (a FERM-domain protein) directly interacts with and activates p114RhoGEF at apical cell-cell junctions to regulate the circumferential actomyosin belt; this interaction is negatively regulated by aPKC-mediated phosphorylation of the FERM-adjacent domain of Lulu2. Additionally, Patj recruits p114RhoGEF to apical cell-cell boundaries via PDZ domain-mediated interaction.\",\n      \"method\": \"Co-immunoprecipitation, RNAi knockdown, GEF activity assays, phosphorylation experiments, domain mapping\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct interaction plus GEF activation assay, upstream regulation by phosphorylation identified, multiple orthogonal methods\",\n      \"pmids\": [\"22006950\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"ArhGEF18-mediated activation of RhoA is required to maintain apicobasal polarity in the vertebrate retinal neuroepithelium; RhoA signals through Rock2 to regulate tight junction localization and cortical actin. Loss of ArhGEF18 increases proliferation and reduces cell cycle exit. Human ARHGEF18 rescues the medaka mutant phenotype.\",\n      \"method\": \"Genetic mutation in medaka fish, rescue with human ARHGEF18, immunostaining, RhoA activity assays\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo genetic loss-of-function with defined phenotype, pathway placement (RhoA-Rock2), cross-species rescue\",\n      \"pmids\": [\"23698346\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"LKB1 interacts with p114RhoGEF in a kinase-activity-independent manner to control RhoA activity at apical junctions and promote apical junction assembly in human bronchial epithelial cells.\",\n      \"method\": \"Co-immunoprecipitation, kinase-dead LKB1 mutant, RhoA activation assays, RNAi knockdown\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP plus functional KD phenotype, single lab\",\n      \"pmids\": [\"23648482\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"p114-RhoGEF is required for Wnt-3a- and Dishevelled-induced RhoA activation and neurite retraction in neuroblastoma cells; p114-RhoGEF physically interacts with Dvl and Daam1, and its Dvl-binding domain acts as a dominant-negative inhibitor of Dvl-induced neurite retraction.\",\n      \"method\": \"shRNA screening, RhoA activation assays, Co-immunoprecipitation, dominant-negative domain constructs\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple methods (Co-IP, KD, dominant-negative), single lab\",\n      \"pmids\": [\"20810787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"p114RhoGEF drives cortical myosin activation specifically by stimulating myosin light chain double phosphorylation (not single phosphorylation) at cell-cell contacts in migrating epithelial sheets and at the cortex of single migrating cells, promoting collective cell migration and amoeboid-like tumor cell invasion; depletion reduces RhoA but increases Rac activity.\",\n      \"method\": \"RNAi knockdown, myosin phosphorylation assays (mono- vs. double-phospho MLC), Matrigel invasion assay, RhoA/Rac pull-down assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KD with specific phosphorylation readout and pathway placement, single lab\",\n      \"pmids\": [\"23185572\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"p114RhoGEF knockdown impairs late-stage tubulogenesis (lumen consolidation) in HGF-stimulated MDCK cells by blocking cell movement; ROCK and myosin IIA act downstream of p114RhoGEF-RhoA in this pathway.\",\n      \"method\": \"RNAi knockdown, ROCK/myosin IIA inhibitors, live-cell imaging of tubulogenesis\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with inhibitors, live imaging with defined phenotype, single lab\",\n      \"pmids\": [\"26483385\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CRB3A recruits p114RhoGEF and its activator Ehm2 to the cell periphery via its cytoplasmic tail motifs, increasing RhoA activation; ROCK1/2 act downstream to remodel the cytoskeleton and drive circumferential actomyosin belt formation and cell shape change in HeLa cells.\",\n      \"method\": \"Co-immunoprecipitation, domain mutants of CRB3A cytoplasmic tail, RhoA activation assays, ROCK inhibitors, immunofluorescence\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP with domain mapping plus functional pathway placement, single lab\",\n      \"pmids\": [\"26217016\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"p114RhoGEF contains a C-terminal region that specifically binds Gα12 (but not Gα13) independently of the canonical RGS-homology domain mechanism; charge-reversal mutagenesis of conserved residues disrupts Gα12 binding, and dominant-negative Gα12 suppresses serum-mediated signaling through p114RhoGEF in cells.\",\n      \"method\": \"Co-immunoprecipitation, chimeric Gα12/13 constructs, charge-reversal mutagenesis, dominant-negative Gα constructs\",\n      \"journal\": \"Journal of molecular signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mutagenesis plus Co-IP with chimeric G proteins, single lab\",\n      \"pmids\": [\"31051012\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"The p.Thr270Ala missense variant in the DH homology domain of ARHGEF18 (found in patients with adult-onset retinal degeneration) affects a conserved residue required for interaction with and activation of RhoA, supporting the DH domain as the catalytic interface for RhoA activation.\",\n      \"method\": \"Human genetics (biallelic mutations), functional inference from domain analysis of missense variant\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 — functional interpretation of human variant, no direct biochemical reconstitution reported in this paper\",\n      \"pmids\": [\"28132693\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"p114RhoGEF/ARHGEF18 is required for mouse syncytiotrophoblast differentiation and placenta development: it controls expression of AKAP12, is required for PKA-induced actomyosin remodeling, and promotes CREB-driven gene expression necessary for trophoblast cell-cell fusion.\",\n      \"method\": \"In vitro trophoblast differentiation assays, in vivo mouse knockouts, PKA signaling assays, CREB reporter assays, AKAP12 expression analysis\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo KO with defined cellular phenotype plus in vitro mechanistic follow-up, single lab\",\n      \"pmids\": [\"33842485\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Eosinophils express novel N-terminally extended isoforms of ARHGEF18 (LOCGEF-X3/X4/X5) from an alternative transcriptional start site; upon activation (IL5, CCL11, or IL33), LOCGEF and RHOA relocalize from the cell periphery to the two poles of polarized eosinophils, implicating LOCGEF in polarity control in leukocytes.\",\n      \"method\": \"RT-PCR, molecular cloning, immunoblot, immunostaining, recombinant protein expression\",\n      \"journal\": \"Journal of leukocyte biology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — localization and isoform identification without direct functional mechanistic assay\",\n      \"pmids\": [\"29601110\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SEPTIN9 is present at mitochondrial fission sites from early stages and activates ARHGEF18 locally through an isoform-specific N-terminal interaction; SEPTIN9-dependent ARHGEF18 activation is required for mitochondrial calcium influx at early fission steps, upstream of DRP1 recruitment.\",\n      \"method\": \"Live-cell imaging, Co-immunoprecipitation, siRNA knockdown, mitochondrial calcium assays, DRP1 localization\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP plus live imaging plus functional calcium assay, single lab\",\n      \"pmids\": [\"40920138\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ARHGEF18 is phosphorylated in response to shear stress in endothelial cells; when phosphorylated, it interacts with tight junctions and promotes EC elongation, alignment, migration, and maintenance of the endothelial barrier. In vivo, ARHGEF18 controls tight junction formation, EC flow response, and vascular permeability.\",\n      \"method\": \"Phosphorylation assays, Co-immunoprecipitation with tight junction proteins, RNAi/KO in mice, vascular permeability assays, live imaging\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo KO with defined phenotype plus biochemical phosphorylation-interaction link, single lab\",\n      \"pmids\": [\"39977269\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Conditional knockout of Arhgef18 in Müller glial cells disrupts the retinal outer limiting membrane (OLM) adherens junctions and leads to progressive retinal degeneration; ARHGEF18 depletion activates NF-κB, β-catenin, and TBK1 signaling and reduces mitochondrial activity; TBK1 inhibition or nicotinamide rescues these defects.\",\n      \"method\": \"Conditional KO mouse (Müller-specific), cell culture knockdown, OLM protein immunostaining, NF-κB/β-catenin/TBK1 activity assays, mitochondrial activity assays, pharmacological rescue\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo conditional KO with mechanistic pathway follow-up and pharmacological rescue, preprint\",\n      \"pmids\": [\"bio_10.1101_2025.10.07.680916\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"ARHGEF18/p114RhoGEF is a DH/PH-domain RhoGEF that is activated by upstream signals including Gβγ subunits, Gα12, Lulu2, and SEPTIN9 to catalyze guanine nucleotide exchange on RhoA (and Rac1) at spatially defined cellular compartments—including epithelial tight/adherens junctions, the circumferential actomyosin belt, endothelial tight junctions, and mitochondrial fission sites—where it engages complexes with myosin II, ROCK II, cingulin, Patj, and LKB1 to drive junction assembly, actomyosin contractility, cell polarity, tubulogenesis, cell migration, and mitochondrial fission, with phosphorylation events (by aPKC and shear-stress-induced kinases) regulating its activity and localization.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"ARHGEF18 (p114RhoGEF) is a DH/PH-domain guanine nucleotide exchange factor that catalyzes RhoA activation at spatially defined cellular compartments—epithelial and endothelial tight junctions, the circumferential actomyosin belt, and mitochondrial fission sites—to drive junction assembly, apicobasal polarity, actomyosin contractility, cell migration, and organelle fission [PMID:21258369, PMID:22006950, PMID:40920138]. It is activated by diverse upstream inputs including Gβγ subunits, Gα12, the FERM-domain protein Lulu2, CRB3A/Ehm2, Dishevelled/Daam1, SEPTIN9, and LKB1, with aPKC phosphorylation and shear-stress-induced phosphorylation modulating its localization and activity [PMID:14512443, PMID:31051012, PMID:22006950, PMID:39977269]. Downstream, ARHGEF18-activated RhoA signals through ROCK and myosin II to control myosin light chain double-phosphorylation, cortical contractility, tubulogenesis, syncytiotrophoblast differentiation, and endothelial barrier function [PMID:23185572, PMID:26483385, PMID:33842485, PMID:39977269]. Biallelic loss-of-function variants in ARHGEF18 cause retinal degeneration in humans and animal models, reflecting its essential role in maintaining neuroepithelial polarity and the outer limiting membrane [PMID:28132693, PMID:23698346].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Establishing ARHGEF18 as a Gβγ-responsive RhoGEF resolved how heterotrimeric G protein signaling activates RhoA and Rac1 to induce stress fibers and ROS production.\",\n      \"evidence\": \"Co-IP, pull-down, dominant-negative mutants, and SRE reporter assays in mammalian cells\",\n      \"pmids\": [\"14512443\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct GEF kinetics with purified Gβγ and RhoA not reported\", \"Relative contribution to Rac1 vs. RhoA activation in physiological settings unclear\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Linking ARHGEF18 to Wnt/PCP signaling via Dishevelled and Daam1 revealed how non-canonical Wnt signals funnel through a specific GEF to activate RhoA and drive neurite retraction.\",\n      \"evidence\": \"shRNA screen, Co-IP with Dvl and Daam1, dominant-negative domain constructs in neuroblastoma cells\",\n      \"pmids\": [\"20810787\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether this Dvl–ARHGEF18 axis operates in non-neuronal PCP contexts not tested\", \"Direct binding interface between Dvl and ARHGEF18 not mapped\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Demonstrating that ARHGEF18 localizes to epithelial junctions and drives spatially restricted RhoA activation in complex with myosin II, ROCK II, and cingulin established it as the principal junctional RhoGEF controlling tight junction assembly and epithelial morphogenesis.\",\n      \"evidence\": \"RNAi, reciprocal Co-IP, RhoA activation assays, live imaging in epithelial cells; parallel study showed Lulu2-mediated activation and aPKC-dependent negative regulation at apical junctions\",\n      \"pmids\": [\"21258369\", \"22006950\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Crystal structure of ARHGEF18–cingulin or ARHGEF18–Lulu2 complex unavailable\", \"Whether ARHGEF18 directly binds ROCK II or association is indirect through RhoA not resolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Genetic loss-of-function in medaka and interaction studies with LKB1 extended the junctional RhoGEF model in vivo, showing ARHGEF18 is essential for retinal neuroepithelial polarity, tight junction integrity, and cell cycle regulation, with LKB1 acting as a kinase-independent scaffold.\",\n      \"evidence\": \"Medaka mutant rescued by human ARHGEF18, immunostaining, RhoA assays; Co-IP of LKB1 with kinase-dead mutant in bronchial epithelial cells\",\n      \"pmids\": [\"23698346\", \"23648482\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which ARHGEF18 loss increases proliferation in retinal neuroepithelium not defined\", \"Structural basis of LKB1–ARHGEF18 interaction unknown\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Showing that ARHGEF18 selectively promotes myosin light chain double-phosphorylation at cell contacts and in single migrating cells clarified its specific contribution to cortical contractility, collective migration, and amoeboid invasion.\",\n      \"evidence\": \"RNAi, mono- vs. di-phospho-MLC antibodies, Matrigel invasion, RhoA/Rac pull-down\",\n      \"pmids\": [\"23185572\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Which kinase(s) downstream of ROCK mediate double-phosphorylation not identified\", \"Relative contribution of ARHGEF18 vs. other RhoGEFs in invasive migration not compared\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Placing ARHGEF18 upstream of ROCK and myosin IIA during tubulogenesis and demonstrating CRB3A-mediated recruitment with Ehm2 revealed how polarity determinants spatially engage ARHGEF18 to organize the actomyosin belt.\",\n      \"evidence\": \"RNAi plus ROCK/myosin IIA inhibitors in MDCK tubulogenesis; Co-IP and domain mutants of CRB3A in HeLa cells\",\n      \"pmids\": [\"26483385\", \"26217016\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether Ehm2 directly activates ARHGEF18 catalytic activity or only recruits it not distinguished\", \"Role in in vivo tubulogenesis not confirmed\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identifying a non-canonical Gα12-binding region in the ARHGEF18 C-terminus, distinct from classic RGS-domain interactions, expanded the repertoire of heterotrimeric G protein inputs that activate this GEF.\",\n      \"evidence\": \"Co-IP with chimeric Gα12/13 constructs and charge-reversal mutagenesis\",\n      \"pmids\": [\"31051012\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No crystal structure of Gα12–ARHGEF18 interface\", \"Whether Gα12 and Gβγ act synergistically or independently on ARHGEF18 not tested\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Discovery of biallelic ARHGEF18 variants (p.Thr270Ala in the DH domain) in patients with retinal degeneration linked the gene to human Mendelian disease and pinpointed a catalytically essential residue.\",\n      \"evidence\": \"Human genetic analysis of patients with adult-onset retinal degeneration; domain-level functional inference\",\n      \"pmids\": [\"28132693\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No direct biochemical reconstitution of T270A variant GEF activity reported in this study\", \"Genotype–phenotype spectrum across additional families not established\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrating that ARHGEF18 knockout disrupts syncytiotrophoblast differentiation and placenta development via PKA-dependent actomyosin remodeling and CREB-driven transcription revealed a non-junctional developmental function.\",\n      \"evidence\": \"Mouse knockout, in vitro trophoblast differentiation, PKA signaling and CREB reporter assays\",\n      \"pmids\": [\"33842485\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How ARHGEF18 controls AKAP12 expression mechanistically not resolved\", \"Whether RhoA is the sole mediator downstream of ARHGEF18 in trophoblast fusion unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identification of SEPTIN9 as an activator of ARHGEF18 at mitochondrial fission sites, upstream of calcium influx and DRP1 recruitment, established a new organellar function for this GEF beyond junctions.\",\n      \"evidence\": \"Live-cell imaging, Co-IP, siRNA, mitochondrial calcium assays in mammalian cells\",\n      \"pmids\": [\"40920138\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether ARHGEF18 activates RhoA or another GTPase at mitochondria not definitively shown\", \"Mechanism linking ARHGEF18-dependent signaling to mitochondrial calcium influx not identified\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Demonstrating shear-stress-induced phosphorylation of ARHGEF18 and its requirement for endothelial tight junction formation, flow-induced alignment, and vascular barrier integrity extended its junctional role to the endothelium in vivo.\",\n      \"evidence\": \"Phosphorylation assays, Co-IP with TJ proteins, endothelial KO mice, vascular permeability assays\",\n      \"pmids\": [\"39977269\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Identity of the kinase(s) that phosphorylate ARHGEF18 under shear stress not determined\", \"Phosphosite(s) responsible for TJ interaction not mapped\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A full structural understanding of ARHGEF18 in complex with its diverse activators and effectors is lacking, and the relative contributions of RhoA vs. Rac1 activation across its varied cellular contexts remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No crystal or cryo-EM structure of ARHGEF18 or any of its complexes\", \"Isoform-specific functions (e.g., eosinophil LOCGEF isoforms) not functionally characterized\", \"Whether ARHGEF18 has catalytic-independent scaffold functions remains untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 2, 3, 5, 6, 8, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 2, 6, 8, 12, 14]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [13]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 2, 3, 5, 8, 9, 13, 14]},\n      {\"term_id\": \"R-HSA-1500931\", \"supporting_discovery_ids\": [0, 2, 3, 4, 14]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [3, 11]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [13]}\n    ],\n    \"complexes\": [\n      \"p114RhoGEF–myosin II–ROCK II–cingulin junctional complex\",\n      \"Lulu2–p114RhoGEF apical complex\",\n      \"CRB3A–Ehm2–p114RhoGEF polarity complex\"\n    ],\n    \"partners\": [\n      \"RHOA\",\n      \"MYH9\",\n      \"ROCK2\",\n      \"CGN\",\n      \"EPB41L4B\",\n      \"SEPT9\",\n      \"STK11\",\n      \"CRB3\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}