{"gene":"RND1","run_date":"2026-06-10T06:43:37","timeline":{"discoveries":[{"year":1998,"finding":"Rnd1 is constitutively GTP-bound due to low GDP affinity and rapid spontaneous nucleotide exchange, and lacks intrinsic GTPase activity. Expression of Rnd1 in fibroblasts inhibits actin stress fibers, membrane ruffles, and integrin-based focal adhesions, inducing cell rounding and loss of cell-substrate adhesion.","method":"GTPase activity assays, nucleotide binding assays, overexpression in fibroblasts with cytoskeletal and adhesion readouts","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — biochemical characterization of GTPase activity combined with cellular overexpression phenotypes; foundational paper widely replicated","pmids":["9531558"],"is_preprint":false},{"year":1998,"finding":"Rnd1 is concentrated at adherens junctions in confluent fibroblasts and epithelial cells, as determined by subcellular localization experiments.","method":"Subcellular fractionation and immunostaining","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — direct localization experiment in multiple cell types but no functional follow-up linking junctional localization to specific mechanism","pmids":["9531558"],"is_preprint":false},{"year":2002,"finding":"Rnd1 directly binds the cytoplasmic domain of Plexin-A1, and constitutively active Rnd1 is sufficient to trigger Plexin-A1 signaling and cytoskeletal collapse even in the absence of Semaphorin 3A. RhoD antagonizes this effect by blocking Plexin-A1 activation by Rnd1.","method":"Co-immunoprecipitation, pulldown, overexpression/dominant-negative experiments, growth cone collapse assay","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal binding assays combined with functional rescue/dominance experiments replicated across multiple GTPases","pmids":["11784792"],"is_preprint":false},{"year":2003,"finding":"Rnd1 directly interacts with the cytoplasmic domain of Plexin-B1, promotes the interaction between Plexin-B1 and PDZ-RhoGEF, and dramatically potentiates Plexin-B1-mediated RhoA activation in response to Semaphorin 4D, leading to cell contraction via the PDZ-RhoGEF/RhoA/ROCK pathway.","method":"Co-immunoprecipitation, pulldown, dominant-negative RhoA and PDZ-RhoGEF constructs, ROCK inhibitor treatment, RhoA activity assay in COS-7 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, multiple orthogonal dominant-negative constructs, biochemical RhoA activation assay, mutation of Rnd1 binding site on Plexin-B1","pmids":["12730235"],"is_preprint":false},{"year":2003,"finding":"Rnd1 promotes dendritic spine elongation in hippocampal neurons. Antisense-mediated knockdown of endogenous Rnd1 reduces spine number and width and increases headless protrusions, demonstrating a role in spine formation during the synaptogenic stage.","method":"Overexpression in cultured hippocampal neurons, antisense oligonucleotide knockdown, immunoblot of synaptosomal fractions, morphometric analysis","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — direct gain- and loss-of-function with defined morphological readouts, single lab","pmids":["14657163"],"is_preprint":false},{"year":1999,"finding":"Recombinant prenylated Rnd1 dose-dependently inhibits carbachol- and GTPγS-induced Ca2+ sensitization in permeabilized smooth muscle by interfering with a RhoA-dependent mechanism, without affecting Ca2+-tension relationships or calyculin A-induced tension.","method":"Permeabilized smooth muscle strip force measurements, recombinant protein application, dose-response analysis","journal":"The Journal of physiology","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — direct in vitro reconstitution in permeabilized tissue, multiple pharmacological controls, single lab","pmids":["10200428"],"is_preprint":false},{"year":2000,"finding":"Rnd1 expression in PC12 cells induces formation of neuritic processes by disrupting cortical actin filaments; this process formation is inhibited by dominant-negative Rac1, placing Rnd1 upstream of Rac in this neuritic outgrowth pathway.","method":"Overexpression in PC12 cells, cytochalasin D comparison, dominant-negative Rac1 epistasis, cytoskeletal staining","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — epistasis by dominant-negative Rac1, pharmacological mimic, single lab","pmids":["11095956"],"is_preprint":false},{"year":2000,"finding":"Rnd1 interacts with the adapter protein Grb7 via the Rnd1 switch II loop and the Grb7 SH2 domain, as demonstrated by yeast two-hybrid, in vitro pulldown, and pulldown from SK-BR3 breast cancer cells.","method":"Yeast two-hybrid, in vitro pulldown, cell lysate pulldown","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — multiple binding assays across in vitro and cellular contexts, domain mapping performed, single lab","pmids":["10664463"],"is_preprint":false},{"year":2005,"finding":"Rnd1 directly associates with FRS2α and FRS2β (docking proteins of FGF receptors). FRS2β binding suppresses the inhibitory effect of Rnd1 on RhoA. Upon FGF receptor 1 activation, FRS2β is phosphorylated, recruits Shp2, and releases Rnd1, which then inhibits RhoA activity. Rnd1 knockdown suppresses FGF-induced neurite outgrowth in PC12 cells.","method":"Co-immunoprecipitation, in vitro pulldown, siRNA knockdown, RhoA activity assay, dominant-negative and constitutively active constructs","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, siRNA knockdown with defined phenotype, biochemical RhoA activity measurement, phosphorylation-dependent release mechanism demonstrated","pmids":["15738000"],"is_preprint":false},{"year":2006,"finding":"Rnd1 is required for neuronal activity-dependent dendritic development in hippocampal neurons. RNAi knockdown inhibits neuronal activity-dependent dendritic growth and BDNF-promoted dendritogenesis, and this inhibition is rescued by blocking the RhoA effector ROCK, placing Rnd1 upstream of RhoA/ROCK in dendritic development.","method":"RNAi knockdown, ROCK inhibitor rescue, BDNF treatment, morphometric dendritic analysis in hippocampal neurons","journal":"Neuroscience letters","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — RNAi loss-of-function with ROCK inhibitor epistasis, single lab","pmids":["16530331"],"is_preprint":false},{"year":2007,"finding":"Rnd1, Rac1, and RhoD all bind the same region (β-strands 3 and 4 and a short α-helix) of the plexin-B1 Rho GTPase binding domain (RBD), not the CRIB-like motif. GTPase binding destabilizes the homodimer of the plexin-B1 RBD, suggesting a regulatory model involving dimerization-dependent signaling.","method":"Solution NMR spectroscopy, 2.0 Å X-ray crystallography, binding interface mapping","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure at 2.0 Å resolution combined with NMR mapping of binding interface; structural and biophysical methods orthogonal","pmids":["17916560"],"is_preprint":false},{"year":2009,"finding":"Rnd1 physically and functionally interacts with Unc5B and mediates FLRT3-induced cell deadhesion in Xenopus embryos. Rnd1 and FLRT3 form a complex that modulates cell adhesion during early development.","method":"Co-immunoprecipitation, overexpression, morpholino knockdown in Xenopus embryos, cell adhesion assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — protein interaction confirmed by Co-IP, functional synergy shown by morpholino double knockdown, single lab","pmids":["19492039"],"is_preprint":false},{"year":2011,"finding":"Crystal structures of the plexin-A2 RBD in complex with Rnd1 and of plexin-C1 and -D1 RBDs alone reveal that in plexin-A2 and -B1, the RBD β3-β4 loop adjusts conformation to accommodate Rnd1 binding, whereas plexin-C1 and -D1 lack key nonpolar residues and do not significantly interact with Rnd1. Introduction of nonpolar residues in plexin-C1/-D1 generates Rnd1 affinity.","method":"X-ray crystallography, isothermal titration calorimetry, site-directed mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures with mutagenesis and ITC, multiple plexin isoforms compared","pmids":["21610070"],"is_preprint":false},{"year":2012,"finding":"Rnd1 and Rnd3, but not Rnd2, contain a KERRA sequence in their N-terminus that functions as a lipid raft-targeting determinant. This sequence mediates the targeting of p190 RhoGAP to lipid rafts, which is required for p190 RhoGAP activation and downstream RhoA inhibition. Rnd2 lacks this sequence and fails to activate p190 RhoGAP in cells despite equal direct binding to p190 RhoGAP in vitro.","method":"Lipid raft fractionation, p190 RhoGAP activity assay, N-terminal deletion/swap mutants, direct binding assays","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — mechanistic dissection with domain mutants, biochemical fractionation, in vitro vs. in vivo activity comparison distinguishing Rnd family members","pmids":["22357615"],"is_preprint":false},{"year":2014,"finding":"Rnd1 suppresses Ras signaling by activating the GAP domain of Plexin-B1, which inhibits Rap1. Rap1 inhibition derepresses p120 Ras-GAP, which then inhibits Ras-MAPK signaling. Rnd1 depletion induces EMT and cooperates with c-Myc deregulation or p53 loss for neoplastic conversion in mammary epithelial cells.","method":"Rnd1 depletion (siRNA/shRNA), Ras and Rap1 activity assays, epistasis with dominant-negative/constitutively active Ras pathway components, mouse mammary tumor models","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — biochemical pathway dissection with activity assays, genetic epistasis, and in vivo mouse models in single study","pmids":["25531777"],"is_preprint":false},{"year":2014,"finding":"Cytoplasmic STI1 (stress-inducible protein 1) directly interacts with Rnd1 specifically (not Rnd2 or Rnd3). STI1 overexpression prevents Rnd1-Plexin-A1-mediated cytoskeletal retraction in the COS collapse assay and enhances neurite outgrowth downstream of Rnd1 in PC-12 cells.","method":"Co-immunoprecipitation, COS collapse assay, PC-12 neurite outgrowth assay, overexpression","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP with specificity demonstrated across Rnd family, functional assays in two cell models, single lab","pmids":["24690281"],"is_preprint":false},{"year":2018,"finding":"RND1 interacts with p53 by co-immunoprecipitation and leads to de-ubiquitination of p53 protein, promoting p53 stability and activating the p53-SLC7A11 signaling axis to induce lipid peroxidation and ferroptosis in glioblastoma cells.","method":"Co-immunoprecipitation, ubiquitination assays, western blot, luciferase reporter, in vivo xenograft","journal":"Cell & bioscience","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — Co-IP and ubiquitination assay with pathway reporter, in vivo validation, single lab","pmids":["35505371"],"is_preprint":false},{"year":2018,"finding":"RND1 overexpression inhibits the Raf/MEK/ERK cascade and reduces RhoA activity in hepatocellular carcinoma cells, suppressing EMT-mediated metastasis.","method":"Overexpression and knockdown, ERK/RhoA activity assays, in vitro migration/invasion assays, in vivo mouse metastasis model","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — biochemical pathway activity assays with gain/loss of function, in vivo model, single lab","pmids":["29706627"],"is_preprint":false},{"year":2018,"finding":"RND1 transcription is rapidly induced by topoisomerase I cleavage complexes (TOP1cc) in a PARP-1-dependent manner. PARP-1 inhibition reduces RND1 transcription; RND1 overexpression increases PARP-1 levels, indicating a cross-talk. RND1 protects cells from camptothecin-induced apoptosis.","method":"RT-PCR, mRNA stability assay, PARP-1 inhibitor treatment, camptothecin and UV/H2O2 treatment, overexpression/apoptosis assays","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — pharmacological inhibition and overexpression with transcriptional and apoptosis readouts, single lab","pmids":["30209297"],"is_preprint":false},{"year":2019,"finding":"Rnd1 interacts with Myozap (an intercalated disc protein), identified by yeast two-hybrid and confirmed by co-immunoprecipitation. This interaction is functionally important: Rnd1 overexpression activates SRF-dependent signaling via the RhoA-Myozap network, promotes cardiomyocyte hypertrophy, and increases cardiomyocyte proliferation markers in response to mechanical stretch.","method":"Yeast two-hybrid screen, co-immunoprecipitation, overexpression in NRVCMs, SRF reporter assay, cell size and proliferation readouts","journal":"Journal of molecular and cellular cardiology","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — yeast two-hybrid confirmed by Co-IP, functional reporter assay, single lab","pmids":["30797814"],"is_preprint":false},{"year":2021,"finding":"Molecular dynamics simulations show RND1 reinforces the plexin dimerization interface whereas RhoD destabilizes it, due to differential interaction with the inner leaflet of the cell membrane. RND1 and RhoD interact differently with the membrane via allosteric networks involving the RBD, RBD linkers, and a buttress segment. RhoD's short C-terminal tail and positively charged membrane interface distinguish it from RND1.","method":"Molecular dynamics simulations (structural/computational)","journal":"eLife","confidence":"Low","confidence_rationale":"Tier 4 / Weak — computational MD simulations only, no direct experimental validation of membrane interaction or dimerization effect in this paper","pmids":["34114565"],"is_preprint":false},{"year":2022,"finding":"RND1 is a direct Notch transcriptional target in endothelial cells, required for Notch-mediated suppression of endothelial migration and sprouting angiogenesis, and for Notch control of Ras activity in endothelial cells.","method":"Transcriptomic analysis (RNA-seq), chromatin studies, RND1 knockdown with migration and angiogenesis assays, Ras activity assay","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — transcriptional target identified, functional knockdown with specific angiogenesis and Ras activity readouts, single lab","pmids":["35102202"],"is_preprint":false},{"year":2022,"finding":"Rnd1 counteracts intracellular calcium fluctuations by inhibiting RhoA activation, thereby inhibiting virus internalization in innate immune defense. Rnd1 also facilitates production of pro-inflammatory cytokines IL-6 and TNF-α through Plexin-B1 to combat intracellular bacterial infections.","method":"Overexpression and knockdown of Rnd1, calcium flux assays, viral infection assays, cytokine measurement (ELISA), Plexin-B1 interaction","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — two distinct functional mechanisms tested in gain/loss-of-function experiments with defined infection readouts, single lab","pmids":["35654795"],"is_preprint":false},{"year":2024,"finding":"RND1 overexpression suppresses EMT in glioblastoma by inhibiting phosphorylation of AKT and GSK3-β, and enhances temozolomide sensitivity both in vitro and in vivo.","method":"Overexpression and knockdown in GBM cell lines, western blot for p-AKT/p-GSK3-β, transwell and wound-healing assays, in vivo xenograft with TMZ treatment","journal":"Cancer biology & therapy","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — biochemical pathway activity assays with gain/loss of function and in vivo model, single lab","pmids":["38444223"],"is_preprint":false},{"year":2010,"finding":"RhoS/RSA-14-44, a testis-specific Rho GTPase renamed RhoS (also known as RHOS, an alias for RND1 according to HGNC), associates with PSMB5 (a catalytic proteasome subunit) in stage-specific spermatogenic cells and regulates the stability of unincorporated PSMB5 precursors in a GTPase activation-dependent manner, linking Rho GTPase signaling to proteasome biogenesis.","method":"Co-immunoprecipitation, overexpression of activated/dominant-negative forms, proteasome activity assays, expression analysis in spermatogenic cells","journal":"Molecular biology of the cell","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP and functional assay in single paper; HGNC aliases list RHOS as alias for RND1 but this paper describes RhoS as a testis-specific distinct Rho GTPase; possible alias collision reduces confidence","pmids":["20980621"],"is_preprint":false}],"current_model":"RND1 is a constitutively GTP-bound, GTPase-inactive member of the Rho family that disrupts actin stress fibers and focal adhesions by activating p190 RhoGAP (via lipid raft targeting) and antagonizing RhoA; it binds directly to the RBD of plexin-A1 and -B1 to activate plexin signaling (promoting cytoskeletal collapse and cell contraction through PDZ-RhoGEF/RhoA/ROCK), activates the Plexin-B1 GAP domain to inhibit Rap1 and thereby derepress p120 Ras-GAP (suppressing Ras-MAPK and EMT), interacts with FRS2β to couple FGF receptor activation to RhoA inhibition and neurite outgrowth, and associates with additional partners including STI1, Grb7, p53, and Myozap to regulate diverse processes including dendritic spine formation, ferroptosis, cardiomyocyte hypertrophy, and innate immune defense."},"narrative":{"mechanistic_narrative":"RND1 is a constitutively GTP-bound, GTPase-deficient Rho-family protein that remodels the actin cytoskeleton and cell adhesion primarily by antagonizing RhoA signaling [PMID:9531558]. Because it has very low GDP affinity, undergoes rapid spontaneous nucleotide exchange, and lacks intrinsic GTPase activity, RND1 functions in a constitutively active state, and its expression collapses actin stress fibers, membrane ruffles, and integrin-based focal adhesions, driving cell rounding and loss of substrate adhesion [PMID:9531558]. A core mechanism of RhoA inhibition is RND1's N-terminal KERRA lipid-raft-targeting sequence, which recruits and activates p190 RhoGAP at rafts—an activity that distinguishes RND1 from Rnd2, which binds p190 RhoGAP but cannot activate it [PMID:22357615]. RND1 is also a direct activator of plexin signaling: it binds the cytoplasmic Rho-GTPase-binding domain (RBD) of plexin-A1 and plexin-B1, and crystallographic and NMR analyses localize this contact to the RBD β3–β4 region rather than a CRIB-like motif, with binding modulating RBD dimerization [PMID:11784792, PMID:12730235, PMID:17916560, PMID:21610070]. Through plexin-B1, RND1 promotes recruitment of PDZ-RhoGEF and potentiates Semaphorin-4D-induced RhoA/ROCK activation and cell contraction [PMID:12730235], while concurrently activating the plexin-B1 GAP domain to inhibit Rap1, derepress p120 Ras-GAP, and suppress Ras–MAPK signaling and epithelial–mesenchymal transition [PMID:25531777]. RND1 couples FGF receptor activation to RhoA inhibition through phosphorylation-dependent release from the FRS2 docking proteins, supporting neurite outgrowth [PMID:15738000], and is required for activity- and BDNF-dependent dendritic development and dendritic spine formation via the RhoA/ROCK axis [PMID:14657163, PMID:16530331]. Acting as a tumor and signaling suppressor, RND1 inhibits Raf/MEK/ERK and AKT/GSK3β signaling in carcinoma cells and stabilizes p53 to engage ferroptosis [PMID:35505371, PMID:29706627, PMID:38444223], and it operates within additional contexts including innate immune defense, cardiomyocyte hypertrophy, and Notch-controlled angiogenesis through partners such as Plexin-B1, Myozap, and others [PMID:35102202, PMID:35654795, PMID:30797814]. RND1 additionally engages adaptor and accessory partners including Grb7, STI1, and Unc5B/FLRT3 that tune its cytoskeletal and adhesion outputs [PMID:10664463, PMID:24690281, PMID:19492039].","teleology":[{"year":1998,"claim":"Established RND1's biochemical identity and core cellular activity, answering whether it behaves like a classical switchable GTPase or a constitutively active one.","evidence":"GTPase and nucleotide-binding assays plus fibroblast overexpression with cytoskeletal/adhesion readouts; junctional localization by fractionation and immunostaining","pmids":["9531558"],"confidence":"High","gaps":["Did not identify the effectors mediating stress-fiber disassembly","Functional consequence of adherens junction localization not resolved"]},{"year":1999,"claim":"Showed that RND1 antagonizes a RhoA-dependent process in native tissue, linking it to physiological smooth muscle contractility.","evidence":"Recombinant prenylated Rnd1 applied to permeabilized smooth muscle strips with force measurements and pharmacological controls","pmids":["10200428"],"confidence":"Medium","gaps":["Molecular intermediary between Rnd1 and RhoA not defined here","Single tissue system"]},{"year":2000,"claim":"Connected RND1 cytoskeletal remodeling to neuronal morphogenesis and placed it within a Rac-dependent process-formation pathway, and identified Grb7 as a physical partner.","evidence":"PC12 process formation with dominant-negative Rac1 epistasis; yeast two-hybrid, in vitro and cellular pulldowns mapping Rnd1 switch II to the Grb7 SH2 domain","pmids":["11095956","10664463"],"confidence":"Medium","gaps":["Functional role of the Grb7 interaction not established","Epistasis based on dominant-negative constructs only"]},{"year":2002,"claim":"Defined RND1 as a direct activator of plexin signaling, answering how a semaphorin receptor is switched on intracellularly.","evidence":"Co-IP/pulldown with plexin-A1, growth cone collapse assays, and competition by RhoD","pmids":["11784792"],"confidence":"High","gaps":["Structural basis of binding not yet resolved","How RhoD competes mechanistically unclear at this stage"]},{"year":2003,"claim":"Resolved the downstream output of RND1–plexin-B1 coupling and extended RND1's neuronal role to dendritic spine formation.","evidence":"Co-IP, dominant-negative RhoA/PDZ-RhoGEF and ROCK inhibitor, RhoA activity assays in COS-7; gain/loss-of-function morphometry in hippocampal neurons","pmids":["12730235","14657163"],"confidence":"High","gaps":["How RND1 simultaneously inhibits RhoA elsewhere yet potentiates plexin-B1 RhoA activation not reconciled","Spine phenotype from a single lab"]},{"year":2005,"claim":"Identified a phosphorylation-gated mechanism coupling FGF receptor activation to RhoA inhibition via RND1 release from FRS2.","evidence":"Reciprocal Co-IP, in vitro pulldown, siRNA knockdown with neurite outgrowth phenotype, and RhoA activity assays in PC12 cells","pmids":["15738000"],"confidence":"High","gaps":["Quantitative dynamics of release not measured","Generality beyond FGFR1/PC12 untested"]},{"year":2006,"claim":"Demonstrated an endogenous requirement for RND1 in activity- and BDNF-dependent dendritogenesis, placing it upstream of RhoA/ROCK in vivo-relevant signaling.","evidence":"RNAi knockdown with ROCK-inhibitor rescue and morphometric dendritic analysis in hippocampal neurons","pmids":["16530331"],"confidence":"Medium","gaps":["Upstream activator linking activity to Rnd1 not identified","Single lab"]},{"year":2007,"claim":"Provided the structural mechanism of GTPase–plexin recognition, showing multiple Rho GTPases share a non-CRIB binding surface and modulate RBD dimerization.","evidence":"Solution NMR and 2.0 Å X-ray crystallography of the plexin-B1 RBD with binding-interface mapping","pmids":["17916560"],"confidence":"High","gaps":["How dimer destabilization translates to receptor activation in cells not directly shown","Did not include all plexin subfamilies"]},{"year":2011,"claim":"Explained plexin subtype selectivity for RND1, identifying the structural determinants that permit or exclude binding.","evidence":"X-ray crystallography of plexin-A2/Rnd1 and plexin-C1/-D1 RBDs, ITC, and gain-of-affinity mutagenesis","pmids":["21610070"],"confidence":"High","gaps":["Functional consequence of engineered binding not tested in signaling","In vivo relevance of selectivity not addressed"]},{"year":2012,"claim":"Pinpointed how RND1 achieves RhoA inhibition, distinguishing binding from activation of p190 RhoGAP through lipid-raft targeting.","evidence":"Lipid raft fractionation, p190 RhoGAP activity assays, N-terminal deletion/swap mutants, and in vitro vs in vivo binding comparison across Rnd family","pmids":["22357615"],"confidence":"High","gaps":["Whether raft targeting is regulated dynamically unknown","Other raft cofactors not identified"]},{"year":2009,"claim":"Linked RND1 to developmental cell deadhesion via a receptor partner, broadening its adhesion-regulatory role.","evidence":"Co-IP with Unc5B, morpholino knockdown, and cell adhesion assays in Xenopus embryos","pmids":["19492039"],"confidence":"Medium","gaps":["Signaling downstream of the Rnd1–Unc5B/FLRT3 complex not dissected","Single model organism"]},{"year":2014,"claim":"Established RND1 as a tumor suppressor that gates Ras–MAPK output through the plexin-B1 GAP/Rap1/p120 Ras-GAP axis, and identified STI1 as a specific modulator.","evidence":"Rnd1 depletion with Ras/Rap1 activity assays, pathway epistasis, and mammary tumor models; Co-IP with STI1 and collapse/neurite assays","pmids":["25531777","24690281"],"confidence":"High","gaps":["How STI1 mechanistically prevents Rnd1-plexin-A1 retraction unclear","Tissue specificity of the Ras-suppression circuit not mapped"]},{"year":2018,"claim":"Expanded RND1 into cancer-relevant survival, metastasis, and ferroptosis regulation and identified transcriptional control by genotoxic stress.","evidence":"Co-IP/ubiquitination assays with p53 and SLC7A11 reporters and xenografts; ERK/RhoA assays and metastasis models in HCC; TOP1cc/PARP-1-dependent RND1 induction with apoptosis assays","pmids":["35505371","29706627","30209297"],"confidence":"Medium","gaps":["Mechanism of p53 de-ubiquitination by RND1 not defined","Single-lab findings per context"]},{"year":2019,"claim":"Identified Myozap as a cardiac partner coupling RND1 to RhoA–SRF signaling in mechanically stressed cardiomyocytes.","evidence":"Yeast two-hybrid and Co-IP, SRF reporter, and cell size/proliferation readouts in NRVCMs under stretch","pmids":["30797814"],"confidence":"Medium","gaps":["In vivo cardiac relevance not established","Single lab"]},{"year":2021,"claim":"Offered a computational model for how RND1 versus RhoD differentially affect plexin dimerization through membrane interaction.","evidence":"Molecular dynamics simulations of GTPase–plexin–membrane systems","pmids":["34114565"],"confidence":"Low","gaps":["No direct experimental validation of predicted membrane interactions or dimer effects","Computational only"]},{"year":2022,"claim":"Placed RND1 within Notch-controlled angiogenesis and innate immune defense, broadening its physiological signaling outputs.","evidence":"RNA-seq/chromatin studies with knockdown angiogenesis and Ras assays; calcium flux, viral infection, and cytokine assays via Plexin-B1","pmids":["35102202","35654795"],"confidence":"Medium","gaps":["Direct chromatin occupancy details limited","Immune mechanisms tested in single system"]},{"year":2024,"claim":"Connected RND1 to chemosensitivity by suppressing EMT through AKT/GSK3β inhibition in glioblastoma.","evidence":"Gain/loss-of-function with p-AKT/p-GSK3β blots, migration assays, and TMZ xenografts","pmids":["38444223"],"confidence":"Medium","gaps":["Direct link between RND1 and AKT pathway components unclear","Single lab"]},{"year":null,"claim":"It remains unresolved how RND1's opposing roles—global RhoA inhibition via p190 RhoGAP versus localized potentiation of plexin-B1-mediated RhoA activation—are spatially and contextually coordinated within a single cell.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model of when RND1 inhibits versus activates RhoA","Regulation of RND1 protein level/localization beyond transcriptional induction undefined","Endogenous in vivo loss-of-function phenotypes largely uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[2,3,13,14]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,2,3]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[3,13]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[13]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,15]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,6]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,3,8,14]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[4,9,11,21]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[16,18]}],"complexes":[],"partners":["PLXNA1","PLXNB1","ARHGAP35","FRS2","GRB7","STI1","MYOZAP","TP53"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q92730","full_name":"Rho-related GTP-binding protein Rho6","aliases":["Rho family GTPase 1","Rnd1"],"length_aa":232,"mass_kda":26.1,"function":"Lacks intrinsic GTPase activity. Has a low affinity for GDP, and constitutively binds GTP. Controls rearrangements of the actin cytoskeleton. Induces the Rac-dependent neuritic process formation in part by disruption of the cortical actin filaments. Causes the formation of many neuritic processes from the cell body with disruption of the cortical actin filaments","subcellular_location":"Cell membrane; Cytoplasm, cytoskeleton","url":"https://www.uniprot.org/uniprotkb/Q92730/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RND1","classification":"Not Classified","n_dependent_lines":28,"n_total_lines":1208,"dependency_fraction":0.023178807947019868},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/RND1","total_profiled":1310},"omim":[{"mim_id":"610344","title":"C2 CALCIUM-DEPENDENT DOMAIN-CONTAINING PROTEIN 4B; C2CD4B","url":"https://www.omim.org/entry/610344"},{"mim_id":"610343","title":"C2 CALCIUM-DEPENDENT DOMAIN-CONTAINING PROTEIN 4A; C2CD4A","url":"https://www.omim.org/entry/610343"},{"mim_id":"609151","title":"UBX DOMAIN PROTEIN 11; UBXN11","url":"https://www.omim.org/entry/609151"},{"mim_id":"609038","title":"RHO FAMILY GTPase 1; RND1","url":"https://www.omim.org/entry/609038"},{"mim_id":"602924","title":"RHO FAMILY GTPase 3; RND3","url":"https://www.omim.org/entry/602924"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Vesicles","reliability":"Supported"},{"location":"Plasma membrane","reliability":"Supported"},{"location":"Actin filaments","reliability":"Supported"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in 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Expression of Rnd1 in fibroblasts inhibits actin stress fibers, membrane ruffles, and integrin-based focal adhesions, inducing cell rounding and loss of cell-substrate adhesion.\",\n      \"method\": \"GTPase activity assays, nucleotide binding assays, overexpression in fibroblasts with cytoskeletal and adhesion readouts\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — biochemical characterization of GTPase activity combined with cellular overexpression phenotypes; foundational paper widely replicated\",\n      \"pmids\": [\"9531558\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Rnd1 is concentrated at adherens junctions in confluent fibroblasts and epithelial cells, as determined by subcellular localization experiments.\",\n      \"method\": \"Subcellular fractionation and immunostaining\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — direct localization experiment in multiple cell types but no functional follow-up linking junctional localization to specific mechanism\",\n      \"pmids\": [\"9531558\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Rnd1 directly binds the cytoplasmic domain of Plexin-A1, and constitutively active Rnd1 is sufficient to trigger Plexin-A1 signaling and cytoskeletal collapse even in the absence of Semaphorin 3A. RhoD antagonizes this effect by blocking Plexin-A1 activation by Rnd1.\",\n      \"method\": \"Co-immunoprecipitation, pulldown, overexpression/dominant-negative experiments, growth cone collapse assay\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal binding assays combined with functional rescue/dominance experiments replicated across multiple GTPases\",\n      \"pmids\": [\"11784792\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Rnd1 directly interacts with the cytoplasmic domain of Plexin-B1, promotes the interaction between Plexin-B1 and PDZ-RhoGEF, and dramatically potentiates Plexin-B1-mediated RhoA activation in response to Semaphorin 4D, leading to cell contraction via the PDZ-RhoGEF/RhoA/ROCK pathway.\",\n      \"method\": \"Co-immunoprecipitation, pulldown, dominant-negative RhoA and PDZ-RhoGEF constructs, ROCK inhibitor treatment, RhoA activity assay in COS-7 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, multiple orthogonal dominant-negative constructs, biochemical RhoA activation assay, mutation of Rnd1 binding site on Plexin-B1\",\n      \"pmids\": [\"12730235\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Rnd1 promotes dendritic spine elongation in hippocampal neurons. Antisense-mediated knockdown of endogenous Rnd1 reduces spine number and width and increases headless protrusions, demonstrating a role in spine formation during the synaptogenic stage.\",\n      \"method\": \"Overexpression in cultured hippocampal neurons, antisense oligonucleotide knockdown, immunoblot of synaptosomal fractions, morphometric analysis\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — direct gain- and loss-of-function with defined morphological readouts, single lab\",\n      \"pmids\": [\"14657163\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Recombinant prenylated Rnd1 dose-dependently inhibits carbachol- and GTPγS-induced Ca2+ sensitization in permeabilized smooth muscle by interfering with a RhoA-dependent mechanism, without affecting Ca2+-tension relationships or calyculin A-induced tension.\",\n      \"method\": \"Permeabilized smooth muscle strip force measurements, recombinant protein application, dose-response analysis\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — direct in vitro reconstitution in permeabilized tissue, multiple pharmacological controls, single lab\",\n      \"pmids\": [\"10200428\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Rnd1 expression in PC12 cells induces formation of neuritic processes by disrupting cortical actin filaments; this process formation is inhibited by dominant-negative Rac1, placing Rnd1 upstream of Rac in this neuritic outgrowth pathway.\",\n      \"method\": \"Overexpression in PC12 cells, cytochalasin D comparison, dominant-negative Rac1 epistasis, cytoskeletal staining\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — epistasis by dominant-negative Rac1, pharmacological mimic, single lab\",\n      \"pmids\": [\"11095956\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Rnd1 interacts with the adapter protein Grb7 via the Rnd1 switch II loop and the Grb7 SH2 domain, as demonstrated by yeast two-hybrid, in vitro pulldown, and pulldown from SK-BR3 breast cancer cells.\",\n      \"method\": \"Yeast two-hybrid, in vitro pulldown, cell lysate pulldown\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — multiple binding assays across in vitro and cellular contexts, domain mapping performed, single lab\",\n      \"pmids\": [\"10664463\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Rnd1 directly associates with FRS2α and FRS2β (docking proteins of FGF receptors). FRS2β binding suppresses the inhibitory effect of Rnd1 on RhoA. Upon FGF receptor 1 activation, FRS2β is phosphorylated, recruits Shp2, and releases Rnd1, which then inhibits RhoA activity. Rnd1 knockdown suppresses FGF-induced neurite outgrowth in PC12 cells.\",\n      \"method\": \"Co-immunoprecipitation, in vitro pulldown, siRNA knockdown, RhoA activity assay, dominant-negative and constitutively active constructs\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, siRNA knockdown with defined phenotype, biochemical RhoA activity measurement, phosphorylation-dependent release mechanism demonstrated\",\n      \"pmids\": [\"15738000\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Rnd1 is required for neuronal activity-dependent dendritic development in hippocampal neurons. RNAi knockdown inhibits neuronal activity-dependent dendritic growth and BDNF-promoted dendritogenesis, and this inhibition is rescued by blocking the RhoA effector ROCK, placing Rnd1 upstream of RhoA/ROCK in dendritic development.\",\n      \"method\": \"RNAi knockdown, ROCK inhibitor rescue, BDNF treatment, morphometric dendritic analysis in hippocampal neurons\",\n      \"journal\": \"Neuroscience letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — RNAi loss-of-function with ROCK inhibitor epistasis, single lab\",\n      \"pmids\": [\"16530331\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Rnd1, Rac1, and RhoD all bind the same region (β-strands 3 and 4 and a short α-helix) of the plexin-B1 Rho GTPase binding domain (RBD), not the CRIB-like motif. GTPase binding destabilizes the homodimer of the plexin-B1 RBD, suggesting a regulatory model involving dimerization-dependent signaling.\",\n      \"method\": \"Solution NMR spectroscopy, 2.0 Å X-ray crystallography, binding interface mapping\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure at 2.0 Å resolution combined with NMR mapping of binding interface; structural and biophysical methods orthogonal\",\n      \"pmids\": [\"17916560\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Rnd1 physically and functionally interacts with Unc5B and mediates FLRT3-induced cell deadhesion in Xenopus embryos. Rnd1 and FLRT3 form a complex that modulates cell adhesion during early development.\",\n      \"method\": \"Co-immunoprecipitation, overexpression, morpholino knockdown in Xenopus embryos, cell adhesion assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — protein interaction confirmed by Co-IP, functional synergy shown by morpholino double knockdown, single lab\",\n      \"pmids\": [\"19492039\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Crystal structures of the plexin-A2 RBD in complex with Rnd1 and of plexin-C1 and -D1 RBDs alone reveal that in plexin-A2 and -B1, the RBD β3-β4 loop adjusts conformation to accommodate Rnd1 binding, whereas plexin-C1 and -D1 lack key nonpolar residues and do not significantly interact with Rnd1. Introduction of nonpolar residues in plexin-C1/-D1 generates Rnd1 affinity.\",\n      \"method\": \"X-ray crystallography, isothermal titration calorimetry, site-directed mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures with mutagenesis and ITC, multiple plexin isoforms compared\",\n      \"pmids\": [\"21610070\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Rnd1 and Rnd3, but not Rnd2, contain a KERRA sequence in their N-terminus that functions as a lipid raft-targeting determinant. This sequence mediates the targeting of p190 RhoGAP to lipid rafts, which is required for p190 RhoGAP activation and downstream RhoA inhibition. Rnd2 lacks this sequence and fails to activate p190 RhoGAP in cells despite equal direct binding to p190 RhoGAP in vitro.\",\n      \"method\": \"Lipid raft fractionation, p190 RhoGAP activity assay, N-terminal deletion/swap mutants, direct binding assays\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mechanistic dissection with domain mutants, biochemical fractionation, in vitro vs. in vivo activity comparison distinguishing Rnd family members\",\n      \"pmids\": [\"22357615\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Rnd1 suppresses Ras signaling by activating the GAP domain of Plexin-B1, which inhibits Rap1. Rap1 inhibition derepresses p120 Ras-GAP, which then inhibits Ras-MAPK signaling. Rnd1 depletion induces EMT and cooperates with c-Myc deregulation or p53 loss for neoplastic conversion in mammary epithelial cells.\",\n      \"method\": \"Rnd1 depletion (siRNA/shRNA), Ras and Rap1 activity assays, epistasis with dominant-negative/constitutively active Ras pathway components, mouse mammary tumor models\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — biochemical pathway dissection with activity assays, genetic epistasis, and in vivo mouse models in single study\",\n      \"pmids\": [\"25531777\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Cytoplasmic STI1 (stress-inducible protein 1) directly interacts with Rnd1 specifically (not Rnd2 or Rnd3). STI1 overexpression prevents Rnd1-Plexin-A1-mediated cytoskeletal retraction in the COS collapse assay and enhances neurite outgrowth downstream of Rnd1 in PC-12 cells.\",\n      \"method\": \"Co-immunoprecipitation, COS collapse assay, PC-12 neurite outgrowth assay, overexpression\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP with specificity demonstrated across Rnd family, functional assays in two cell models, single lab\",\n      \"pmids\": [\"24690281\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"RND1 interacts with p53 by co-immunoprecipitation and leads to de-ubiquitination of p53 protein, promoting p53 stability and activating the p53-SLC7A11 signaling axis to induce lipid peroxidation and ferroptosis in glioblastoma cells.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, western blot, luciferase reporter, in vivo xenograft\",\n      \"journal\": \"Cell & bioscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — Co-IP and ubiquitination assay with pathway reporter, in vivo validation, single lab\",\n      \"pmids\": [\"35505371\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"RND1 overexpression inhibits the Raf/MEK/ERK cascade and reduces RhoA activity in hepatocellular carcinoma cells, suppressing EMT-mediated metastasis.\",\n      \"method\": \"Overexpression and knockdown, ERK/RhoA activity assays, in vitro migration/invasion assays, in vivo mouse metastasis model\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — biochemical pathway activity assays with gain/loss of function, in vivo model, single lab\",\n      \"pmids\": [\"29706627\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"RND1 transcription is rapidly induced by topoisomerase I cleavage complexes (TOP1cc) in a PARP-1-dependent manner. PARP-1 inhibition reduces RND1 transcription; RND1 overexpression increases PARP-1 levels, indicating a cross-talk. RND1 protects cells from camptothecin-induced apoptosis.\",\n      \"method\": \"RT-PCR, mRNA stability assay, PARP-1 inhibitor treatment, camptothecin and UV/H2O2 treatment, overexpression/apoptosis assays\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — pharmacological inhibition and overexpression with transcriptional and apoptosis readouts, single lab\",\n      \"pmids\": [\"30209297\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Rnd1 interacts with Myozap (an intercalated disc protein), identified by yeast two-hybrid and confirmed by co-immunoprecipitation. This interaction is functionally important: Rnd1 overexpression activates SRF-dependent signaling via the RhoA-Myozap network, promotes cardiomyocyte hypertrophy, and increases cardiomyocyte proliferation markers in response to mechanical stretch.\",\n      \"method\": \"Yeast two-hybrid screen, co-immunoprecipitation, overexpression in NRVCMs, SRF reporter assay, cell size and proliferation readouts\",\n      \"journal\": \"Journal of molecular and cellular cardiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — yeast two-hybrid confirmed by Co-IP, functional reporter assay, single lab\",\n      \"pmids\": [\"30797814\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Molecular dynamics simulations show RND1 reinforces the plexin dimerization interface whereas RhoD destabilizes it, due to differential interaction with the inner leaflet of the cell membrane. RND1 and RhoD interact differently with the membrane via allosteric networks involving the RBD, RBD linkers, and a buttress segment. RhoD's short C-terminal tail and positively charged membrane interface distinguish it from RND1.\",\n      \"method\": \"Molecular dynamics simulations (structural/computational)\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — computational MD simulations only, no direct experimental validation of membrane interaction or dimerization effect in this paper\",\n      \"pmids\": [\"34114565\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"RND1 is a direct Notch transcriptional target in endothelial cells, required for Notch-mediated suppression of endothelial migration and sprouting angiogenesis, and for Notch control of Ras activity in endothelial cells.\",\n      \"method\": \"Transcriptomic analysis (RNA-seq), chromatin studies, RND1 knockdown with migration and angiogenesis assays, Ras activity assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — transcriptional target identified, functional knockdown with specific angiogenesis and Ras activity readouts, single lab\",\n      \"pmids\": [\"35102202\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Rnd1 counteracts intracellular calcium fluctuations by inhibiting RhoA activation, thereby inhibiting virus internalization in innate immune defense. Rnd1 also facilitates production of pro-inflammatory cytokines IL-6 and TNF-α through Plexin-B1 to combat intracellular bacterial infections.\",\n      \"method\": \"Overexpression and knockdown of Rnd1, calcium flux assays, viral infection assays, cytokine measurement (ELISA), Plexin-B1 interaction\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — two distinct functional mechanisms tested in gain/loss-of-function experiments with defined infection readouts, single lab\",\n      \"pmids\": [\"35654795\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"RND1 overexpression suppresses EMT in glioblastoma by inhibiting phosphorylation of AKT and GSK3-β, and enhances temozolomide sensitivity both in vitro and in vivo.\",\n      \"method\": \"Overexpression and knockdown in GBM cell lines, western blot for p-AKT/p-GSK3-β, transwell and wound-healing assays, in vivo xenograft with TMZ treatment\",\n      \"journal\": \"Cancer biology & therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — biochemical pathway activity assays with gain/loss of function and in vivo model, single lab\",\n      \"pmids\": [\"38444223\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"RhoS/RSA-14-44, a testis-specific Rho GTPase renamed RhoS (also known as RHOS, an alias for RND1 according to HGNC), associates with PSMB5 (a catalytic proteasome subunit) in stage-specific spermatogenic cells and regulates the stability of unincorporated PSMB5 precursors in a GTPase activation-dependent manner, linking Rho GTPase signaling to proteasome biogenesis.\",\n      \"method\": \"Co-immunoprecipitation, overexpression of activated/dominant-negative forms, proteasome activity assays, expression analysis in spermatogenic cells\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP and functional assay in single paper; HGNC aliases list RHOS as alias for RND1 but this paper describes RhoS as a testis-specific distinct Rho GTPase; possible alias collision reduces confidence\",\n      \"pmids\": [\"20980621\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RND1 is a constitutively GTP-bound, GTPase-inactive member of the Rho family that disrupts actin stress fibers and focal adhesions by activating p190 RhoGAP (via lipid raft targeting) and antagonizing RhoA; it binds directly to the RBD of plexin-A1 and -B1 to activate plexin signaling (promoting cytoskeletal collapse and cell contraction through PDZ-RhoGEF/RhoA/ROCK), activates the Plexin-B1 GAP domain to inhibit Rap1 and thereby derepress p120 Ras-GAP (suppressing Ras-MAPK and EMT), interacts with FRS2β to couple FGF receptor activation to RhoA inhibition and neurite outgrowth, and associates with additional partners including STI1, Grb7, p53, and Myozap to regulate diverse processes including dendritic spine formation, ferroptosis, cardiomyocyte hypertrophy, and innate immune defense.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RND1 is a constitutively GTP-bound, GTPase-deficient Rho-family protein that remodels the actin cytoskeleton and cell adhesion primarily by antagonizing RhoA signaling [#0]. Because it has very low GDP affinity, undergoes rapid spontaneous nucleotide exchange, and lacks intrinsic GTPase activity, RND1 functions in a constitutively active state, and its expression collapses actin stress fibers, membrane ruffles, and integrin-based focal adhesions, driving cell rounding and loss of substrate adhesion [#0]. A core mechanism of RhoA inhibition is RND1's N-terminal KERRA lipid-raft-targeting sequence, which recruits and activates p190 RhoGAP at rafts—an activity that distinguishes RND1 from Rnd2, which binds p190 RhoGAP but cannot activate it [#13]. RND1 is also a direct activator of plexin signaling: it binds the cytoplasmic Rho-GTPase-binding domain (RBD) of plexin-A1 and plexin-B1, and crystallographic and NMR analyses localize this contact to the RBD β3–β4 region rather than a CRIB-like motif, with binding modulating RBD dimerization [#2, #3, #10, #12]. Through plexin-B1, RND1 promotes recruitment of PDZ-RhoGEF and potentiates Semaphorin-4D-induced RhoA/ROCK activation and cell contraction [#3], while concurrently activating the plexin-B1 GAP domain to inhibit Rap1, derepress p120 Ras-GAP, and suppress Ras–MAPK signaling and epithelial–mesenchymal transition [#14]. RND1 couples FGF receptor activation to RhoA inhibition through phosphorylation-dependent release from the FRS2 docking proteins, supporting neurite outgrowth [#8], and is required for activity- and BDNF-dependent dendritic development and dendritic spine formation via the RhoA/ROCK axis [#4, #9]. Acting as a tumor and signaling suppressor, RND1 inhibits Raf/MEK/ERK and AKT/GSK3β signaling in carcinoma cells and stabilizes p53 to engage ferroptosis [#16, #17, #23], and it operates within additional contexts including innate immune defense, cardiomyocyte hypertrophy, and Notch-controlled angiogenesis through partners such as Plexin-B1, Myozap, and others [#21, #22, #19]. RND1 additionally engages adaptor and accessory partners including Grb7, STI1, and Unc5B/FLRT3 that tune its cytoskeletal and adhesion outputs [#7, #15, #11].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established RND1's biochemical identity and core cellular activity, answering whether it behaves like a classical switchable GTPase or a constitutively active one.\",\n      \"evidence\": \"GTPase and nucleotide-binding assays plus fibroblast overexpression with cytoskeletal/adhesion readouts; junctional localization by fractionation and immunostaining\",\n      \"pmids\": [\"9531558\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the effectors mediating stress-fiber disassembly\", \"Functional consequence of adherens junction localization not resolved\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Showed that RND1 antagonizes a RhoA-dependent process in native tissue, linking it to physiological smooth muscle contractility.\",\n      \"evidence\": \"Recombinant prenylated Rnd1 applied to permeabilized smooth muscle strips with force measurements and pharmacological controls\",\n      \"pmids\": [\"10200428\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular intermediary between Rnd1 and RhoA not defined here\", \"Single tissue system\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Connected RND1 cytoskeletal remodeling to neuronal morphogenesis and placed it within a Rac-dependent process-formation pathway, and identified Grb7 as a physical partner.\",\n      \"evidence\": \"PC12 process formation with dominant-negative Rac1 epistasis; yeast two-hybrid, in vitro and cellular pulldowns mapping Rnd1 switch II to the Grb7 SH2 domain\",\n      \"pmids\": [\"11095956\", \"10664463\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional role of the Grb7 interaction not established\", \"Epistasis based on dominant-negative constructs only\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Defined RND1 as a direct activator of plexin signaling, answering how a semaphorin receptor is switched on intracellularly.\",\n      \"evidence\": \"Co-IP/pulldown with plexin-A1, growth cone collapse assays, and competition by RhoD\",\n      \"pmids\": [\"11784792\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of binding not yet resolved\", \"How RhoD competes mechanistically unclear at this stage\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Resolved the downstream output of RND1–plexin-B1 coupling and extended RND1's neuronal role to dendritic spine formation.\",\n      \"evidence\": \"Co-IP, dominant-negative RhoA/PDZ-RhoGEF and ROCK inhibitor, RhoA activity assays in COS-7; gain/loss-of-function morphometry in hippocampal neurons\",\n      \"pmids\": [\"12730235\", \"14657163\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How RND1 simultaneously inhibits RhoA elsewhere yet potentiates plexin-B1 RhoA activation not reconciled\", \"Spine phenotype from a single lab\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identified a phosphorylation-gated mechanism coupling FGF receptor activation to RhoA inhibition via RND1 release from FRS2.\",\n      \"evidence\": \"Reciprocal Co-IP, in vitro pulldown, siRNA knockdown with neurite outgrowth phenotype, and RhoA activity assays in PC12 cells\",\n      \"pmids\": [\"15738000\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative dynamics of release not measured\", \"Generality beyond FGFR1/PC12 untested\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrated an endogenous requirement for RND1 in activity- and BDNF-dependent dendritogenesis, placing it upstream of RhoA/ROCK in vivo-relevant signaling.\",\n      \"evidence\": \"RNAi knockdown with ROCK-inhibitor rescue and morphometric dendritic analysis in hippocampal neurons\",\n      \"pmids\": [\"16530331\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Upstream activator linking activity to Rnd1 not identified\", \"Single lab\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Provided the structural mechanism of GTPase–plexin recognition, showing multiple Rho GTPases share a non-CRIB binding surface and modulate RBD dimerization.\",\n      \"evidence\": \"Solution NMR and 2.0 Å X-ray crystallography of the plexin-B1 RBD with binding-interface mapping\",\n      \"pmids\": [\"17916560\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How dimer destabilization translates to receptor activation in cells not directly shown\", \"Did not include all plexin subfamilies\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Explained plexin subtype selectivity for RND1, identifying the structural determinants that permit or exclude binding.\",\n      \"evidence\": \"X-ray crystallography of plexin-A2/Rnd1 and plexin-C1/-D1 RBDs, ITC, and gain-of-affinity mutagenesis\",\n      \"pmids\": [\"21610070\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of engineered binding not tested in signaling\", \"In vivo relevance of selectivity not addressed\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Pinpointed how RND1 achieves RhoA inhibition, distinguishing binding from activation of p190 RhoGAP through lipid-raft targeting.\",\n      \"evidence\": \"Lipid raft fractionation, p190 RhoGAP activity assays, N-terminal deletion/swap mutants, and in vitro vs in vivo binding comparison across Rnd family\",\n      \"pmids\": [\"22357615\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether raft targeting is regulated dynamically unknown\", \"Other raft cofactors not identified\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Linked RND1 to developmental cell deadhesion via a receptor partner, broadening its adhesion-regulatory role.\",\n      \"evidence\": \"Co-IP with Unc5B, morpholino knockdown, and cell adhesion assays in Xenopus embryos\",\n      \"pmids\": [\"19492039\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Signaling downstream of the Rnd1–Unc5B/FLRT3 complex not dissected\", \"Single model organism\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Established RND1 as a tumor suppressor that gates Ras–MAPK output through the plexin-B1 GAP/Rap1/p120 Ras-GAP axis, and identified STI1 as a specific modulator.\",\n      \"evidence\": \"Rnd1 depletion with Ras/Rap1 activity assays, pathway epistasis, and mammary tumor models; Co-IP with STI1 and collapse/neurite assays\",\n      \"pmids\": [\"25531777\", \"24690281\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How STI1 mechanistically prevents Rnd1-plexin-A1 retraction unclear\", \"Tissue specificity of the Ras-suppression circuit not mapped\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Expanded RND1 into cancer-relevant survival, metastasis, and ferroptosis regulation and identified transcriptional control by genotoxic stress.\",\n      \"evidence\": \"Co-IP/ubiquitination assays with p53 and SLC7A11 reporters and xenografts; ERK/RhoA assays and metastasis models in HCC; TOP1cc/PARP-1-dependent RND1 induction with apoptosis assays\",\n      \"pmids\": [\"35505371\", \"29706627\", \"30209297\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of p53 de-ubiquitination by RND1 not defined\", \"Single-lab findings per context\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identified Myozap as a cardiac partner coupling RND1 to RhoA–SRF signaling in mechanically stressed cardiomyocytes.\",\n      \"evidence\": \"Yeast two-hybrid and Co-IP, SRF reporter, and cell size/proliferation readouts in NRVCMs under stretch\",\n      \"pmids\": [\"30797814\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo cardiac relevance not established\", \"Single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Offered a computational model for how RND1 versus RhoD differentially affect plexin dimerization through membrane interaction.\",\n      \"evidence\": \"Molecular dynamics simulations of GTPase–plexin–membrane systems\",\n      \"pmids\": [\"34114565\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No direct experimental validation of predicted membrane interactions or dimer effects\", \"Computational only\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Placed RND1 within Notch-controlled angiogenesis and innate immune defense, broadening its physiological signaling outputs.\",\n      \"evidence\": \"RNA-seq/chromatin studies with knockdown angiogenesis and Ras assays; calcium flux, viral infection, and cytokine assays via Plexin-B1\",\n      \"pmids\": [\"35102202\", \"35654795\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct chromatin occupancy details limited\", \"Immune mechanisms tested in single system\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Connected RND1 to chemosensitivity by suppressing EMT through AKT/GSK3β inhibition in glioblastoma.\",\n      \"evidence\": \"Gain/loss-of-function with p-AKT/p-GSK3β blots, migration assays, and TMZ xenografts\",\n      \"pmids\": [\"38444223\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct link between RND1 and AKT pathway components unclear\", \"Single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how RND1's opposing roles—global RhoA inhibition via p190 RhoGAP versus localized potentiation of plexin-B1-mediated RhoA activation—are spatially and contextually coordinated within a single cell.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model of when RND1 inhibits versus activates RhoA\", \"Regulation of RND1 protein level/localization beyond transcriptional induction undefined\", \"Endogenous in vivo loss-of-function phenotypes largely uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [2, 3, 13, 14]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 2, 3]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [3, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [13]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 15]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 3, 8, 14]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [4, 9, 11, 21]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [16, 18]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"PLXNA1\", \"PLXNB1\", \"ARHGAP35\", \"FRS2\", \"GRB7\", \"STI1\", \"MYOZAP\", \"TP53\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":8,"faith_pct":87.5}}