{"gene":"CDC42","run_date":"2026-06-09T22:57:18","timeline":{"discoveries":[{"year":1990,"finding":"CDC42Hs (G25K) is the human homolog of yeast CDC42; the G25K cDNA encodes a 191-amino-acid GTP-binding protein that complements yeast cdc42-1 and cdc24-4 temperature-sensitive lethal mutations, demonstrating functional conservation.","method":"cDNA cloning, yeast complementation assay, GTP-binding assay","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution (GTP-binding), functional complementation in yeast, replicated across two independent groups (PMIDs 2122236 and 2124704)","pmids":["2122236","2124704"],"is_preprint":false},{"year":1990,"finding":"CDC42Hs (G25K) undergoes isoprenoid (farnesyl) modification at its C-terminal CAAX motif, and this modification regulates its association with cell membranes versus cytosol.","method":"Metabolic labeling with [3H]mevalonate, 2D gel electrophoresis, immunoblotting, lovastatin inhibition, subcellular fractionation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct metabolic labeling, pharmacological inhibition, fractionation showing membrane/cytosol redistribution upon lovastatin treatment","pmids":["2120220"],"is_preprint":false},{"year":1991,"finding":"A GTPase-activating protein (GAP) for CDC42Hs was purified from human platelets; it stimulates GTP hydrolysis on wild-type CDC42Hs but not on the Val-12 mutant, and shows weak cross-reactivity with Rho but not with Ras or Rap.","method":"Protein purification (~3500-fold), GTPase activity assay, mutant specificity analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro biochemical reconstitution with purified components and mutagenesis specificity controls","pmids":["1939135"],"is_preprint":false},{"year":1992,"finding":"Rho-GDI (GDP-dissociation inhibitor) inhibits GDP dissociation from CDC42Hs and stimulates release of CDC42Hs from plasma membranes. The purified brain GDI also inhibits Dbl-catalyzed GDP dissociation from CDC42Hs.","method":"Protein purification, GDP dissociation assay, membrane extraction assay, immunoblotting","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro biochemical reconstitution with purified proteins and multiple orthogonal functional assays","pmids":["1429634"],"is_preprint":false},{"year":1992,"finding":"CDC42Hs (G25K) undergoes GTP-stimulated carboxyl methylation in brain; it exists as a heterodimer with a 28-kDa protein (RhoGDI), and the associated GDI decreases methylation efficiency and alters guanine nucleotide specificity.","method":"Protein purification, carboxyl methylation assay, two-dimensional electrophoresis, subcellular fractionation","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro assay from a single lab, single methodology set","pmids":["1526984"],"is_preprint":false},{"year":1994,"finding":"GTP-bound CDC42Hs directly associates with the p85 subunit of PI 3-kinase via the Rho-GAP homology domain of p85, and this interaction stimulates PI 3-kinase activity 2–4-fold; the effector domain mutant T35A abolishes binding.","method":"GST pulldown with purified recombinant proteins, co-immunoprecipitation from cell lysates, PI 3-kinase activity assay, effector-domain mutant analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with purified proteins, mutagenesis, and functional enzyme assay in a single comprehensive study","pmids":["8034624"],"is_preprint":false},{"year":1995,"finding":"Microinjection of constitutively active CDC42Hs into Swiss 3T3 fibroblasts induces peripheral actin microspikes and filopodia; bradykinin activates endogenous CDC42Hs to produce the same effects, which are blocked by dominant-negative CDC42Hs(T17N).","method":"Microinjection, phalloidin staining, time-lapse phase-contrast microscopy, dominant-negative inhibition","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function (dominant negative) and gain-of-function microinjection with direct cytoskeletal readout; replicated across multiple conditions","pmids":["7891688"],"is_preprint":false},{"year":1995,"finding":"PAK (hPAK65) is a serine kinase that binds Rac1 and CDC42Hs in a GTP-dependent manner; GTP-bound CDC42Hs or Rac1 induces autophosphorylation of PAK on serine residues, which activates its kinase activity toward myelin basic protein independently of continued GTPase binding.","method":"Protein purification from neutrophil cytosol, GTP-dependent binding assay, in vitro autophosphorylation assay, kinase activity assay toward exogenous substrate","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted kinase activation in vitro with purified components, phosphorylation site determination, and substrate assay in a single rigorous study","pmids":["7744004"],"is_preprint":false},{"year":1995,"finding":"CDC42Hs translocates from the membrane skeleton to the cytoskeleton in platelets stimulated by TRAP or ADP; this translocation is mediated by αIIbβ3 integrin activation and requires actin polymerization and protein-tyrosine kinase activity.","method":"Subcellular fractionation, immunoblotting, cytochalasin and genistein inhibition, integrin blockade","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct fractionation with pharmacological dissection, single lab, multiple inhibitory approaches","pmids":["7542236"],"is_preprint":false},{"year":1996,"finding":"IQGAP1 (p195) is a CDC42Hs effector: it binds preferentially to GTP-bound CDC42Hs and Rac, inhibits CDC42Hs GTPase activity, and co-immunoprecipitates with CDC42Hs from cell lysates. IQGAP1 localizes to lamellipodia and ruffles where it co-localizes with actin.","method":"Affinity chromatography (GTP-Cdc42Hs bead purification), GTPase activity assay, co-immunoprecipitation, immunofluorescence, yeast CDC42/CDC24 pathway inhibition assay","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP, functional GTPase assay, subcellular localization, yeast genetic validation; multiple orthogonal methods","pmids":["8670801"],"is_preprint":false},{"year":1996,"finding":"IQGAP2 (p175) interacts with CDC42Hs in a manner that is less nucleotide-dependent than IQGAP1; both IQGAP1 and IQGAP2 require the switch I domain and an insert region unique to Rho-family proteins for CDC42Hs binding.","method":"Protein purification from rabbit liver cytosol, pulldown with GTP/GDP-Cdc42Hs, chimeric mutant analysis, microsequencing","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — purified protein interaction with domain mapping using chimeric mutants, single lab","pmids":["8702968"],"is_preprint":false},{"year":1996,"finding":"The Rho insert region (residues 122–134) of CDC42Hs is required for RhoGDI-mediated inhibition of GDP dissociation and GTP hydrolysis, and for GDI-stimulated membrane release; this region is not required for effector (PAK, GEF Dbl, or GAP) interactions.","method":"Cdc42Hs/Ha-Ras chimeric mutant construction, GDP dissociation assay, GTPase activity assay, membrane release assay, effector binding assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — domain-swap mutagenesis with multiple functional reconstitution assays, clear mechanistic conclusion, single lab","pmids":["9334181"],"is_preprint":false},{"year":1996,"finding":"RhoGDI binds GDP- and GTP-bound CDC42Hs with similar affinity (~30 nM Kd) as measured by direct fluorescence spectroscopy; the carboxyl-terminal domain of GDI confers high-affinity binding; prenylation of CDC42Hs is required for GDI-induced fluorescence quenching.","method":"Fluorescence spectroscopy using Mant-GDP-loaded CDC42Hs, binding titration, GDI/LD4 chimera analysis, truncation mutants","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct biophysical assay with multiple mutants, clear Kd determination, rigorous controls for prenylation requirement","pmids":["8626553"],"is_preprint":false},{"year":1997,"finding":"Dominant-negative CDC42Hs(T17N) inhibits serum-stimulated cell cycle progression at G1/S in a p38-dependent manner, but Rac1 dominant negative does not produce the same block, demonstrating a specific and distinct role for CDC42Hs in cell cycle inhibition via the p38 pathway.","method":"Quantitative microinjection of dominant-negative GTPases into fibroblasts, cell cycle analysis, pharmacological inhibition of p38","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — microinjection with cell cycle readout and pathway inhibitor epistasis, single lab","pmids":["9148940"],"is_preprint":false},{"year":1997,"finding":"The CDC42Hs(F28L) fast-cycling mutant (which undergoes spontaneous GTP-GDP exchange while retaining GTPase activity) activates JNK1, induces filopodia, and causes oncogenic transformation including anchorage-independent growth and reduced contact inhibition.","method":"Site-directed mutagenesis, JNK reporter assays, filopodia formation by immunofluorescence, focus formation and soft-agar growth assays","journal":"Current biology : CB","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — engineered gain-of-function mutant with multiple transformation readouts, single lab","pmids":["9368762"],"is_preprint":false},{"year":1998,"finding":"PAK4 is a CDC42Hs-specific effector kinase that interacts with activated CDC42Hs via its GBD; co-expression of PAK4 and constitutively active CDC42Hs redistributes PAK4 to the Golgi and induces filopodia and actin polymerization in a manner dependent on PAK4 kinase activity and CDC42Hs binding.","method":"Co-immunoprecipitation, immunofluorescence localization, kinase-dead and binding-deficient mutant analysis, brefeldin A treatment, actin staining","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct interaction, subcellular redistribution, multiple domain mutants defining kinase activity and GBD requirement; multiple orthogonal methods","pmids":["9822598"],"is_preprint":false},{"year":1998,"finding":"MRCK-α (myotonic dystrophy kinase-related Cdc42-binding kinase) binds GTP-Cdc42 through a PAK-like p21-binding domain and phosphorylates non-muscle myosin light chain at Ser19, driving actin-myosin contractility; kinase-dead MRCK-α blocks Cdc42V12-dependent peripheral microspikes and focal complexes.","method":"Recombinant protein binding assay, in vitro kinase assay (myosin light chain phosphorylation), microinjection, kinase-dead and Cdc42-binding-deficient mutants, immunofluorescence","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase reconstitution, substrate identification, and in-cell epistasis with domain mutants; multiple orthogonal methods","pmids":["9418861"],"is_preprint":false},{"year":1998,"finding":"Dominant-negative forms of both Rac1 and CDC42 inhibit Fcγ receptor-mediated phagocytosis in macrophages, but with distinct phenotypes: CDC42 inhibition produces pedestal-like structures while Rac1 inhibition traps particles in thin membrane protrusions, indicating cooperative but distinct roles in phagocytic cup assembly.","method":"Stable transfection of dominant-negative GTPases in RBL-2H3 cells, F-actin staining, particle internalization assay, Clostridium difficile toxin B inhibition","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — stable dominant-negative cell lines, direct phagocytosis assay, distinct morphological phenotypes identifying stage-specific functions","pmids":["9799231"],"is_preprint":false},{"year":1998,"finding":"Integrin-dependent adhesion to fibronectin activates CDC42 (and Rac1), as evidenced by activation of the downstream effector PAK; dominant-negative CDC42 inhibits cell spreading, and epistasis experiments indicate integrins activate CDC42 first, which then activates Rac1 to drive spreading.","method":"PAK activation assay (downstream readout), dominant-negative GTPase expression, cell spreading assay on fibronectin","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional epistasis using dominant negatives, indirect CDC42 activation readout via PAK, single lab","pmids":["9658176"],"is_preprint":false},{"year":1999,"finding":"IQGAP1 integrates Ca2+/calmodulin and CDC42 signaling: in the absence of Ca2+, IQGAP1 binds GTP-Cdc42 and inhibits its GTPase activity; Ca2+/calmodulin dissociates Cdc42 from IQGAP1 and restores GTP hydrolysis. Calmodulin binds the IQ motifs and calponin homology domain of IQGAP1; F-actin competes with Ca2+/calmodulin for the calponin homology domain.","method":"In vitro GTPase activity assay, in vitro binding assay, cell lysate co-immunoprecipitation, Ca2+ titration","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — reconstituted biochemistry with multiple domain-specific interactions and quantified Ca2+ dependence, single rigorous study","pmids":["9867866"],"is_preprint":false},{"year":2000,"finding":"Active CDC42Hs and Rac1 GTPases cause perinuclear collapse of the vimentin intermediate filament network; this effect is independent of CRIB-mediated (PAK/JNK) pathways but is associated with actin reorganization and requires tyrosine phosphorylation events.","method":"Expression of activated GTPases and effector-loop mutants, immunofluorescence of vimentin, pharmacological inhibition (genistein, staurosporin, cytochalasin D), phosphorylation analysis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — effector-loop mutants and pharmacological epistasis, multiple inhibitor controls; single lab","pmids":["10900195"],"is_preprint":false},{"year":2001,"finding":"p21-activated kinase (PAK) phosphorylates merlin (NF2 tumor suppressor) at serine 518 downstream of activated Rac and CDC42; both in vivo (cell-based) and in vitro kinase assays confirmed direct PAK-mediated phosphorylation of merlin.","method":"In vitro kinase assay, in vivo kinase assay in cells, expression of activated Rac and Cdc42, site-directed analysis (Ser518)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct in vitro phosphorylation assay combined with in vivo validation, site-specific analysis; single rigorous study","pmids":["11719502"],"is_preprint":false},{"year":2001,"finding":"RhoGDI is required for cycling of CDC42Hs between membranes and cytosol: a CDC42Hs R66E mutant defective in RhoGDI binding is found exclusively in membrane fractions (predominantly Golgi), whereas wild-type CDC42Hs redistributes to the cytosol when RhoGDI is overexpressed; RhoGDI binding is not required for membrane targeting or filopodia induction.","method":"Site-directed mutagenesis (R66E), subcellular fractionation, immunofluorescence, RhoGDI overexpression","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — engineered binding-deficient mutant, fractionation, and imaging; multiple orthogonal approaches clearly defining GDI-dependent cycling vs. membrane targeting","pmids":["11583574"],"is_preprint":false},{"year":2001,"finding":"During invasin/β1-integrin-mediated phagocytosis in macrophages, CDC42Hs activates WASp and the Arp2/3 complex to drive actin-rich phagocytic cup formation; dominant-negative CDC42Hs, WASp-knockout, and Arp2/3 inhibition each block cup formation and uptake.","method":"Microinjection of dominant-negative N17CDC42Hs, WASp-KO macrophages, Arp2/3 inhibitor microinjection, F-actin staining, internalization assay","journal":"Cellular microbiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function at multiple nodes in the same pathway (GTPase, effector, Arp2/3), genetic KO and biochemical inhibition with direct phagocytic readout","pmids":["11580754"],"is_preprint":false},{"year":2001,"finding":"CDC42Hs facilitates cytoskeletal reorganization and neurite outgrowth through the adaptor protein IRS-58 (58-kDa insulin receptor substrate); an IRS-58 mutant unable to bind CDC42Hs (I267N) fails to localize to F-actin and cannot induce filopodia or neurite outgrowth.","method":"Yeast two-hybrid, immunofluorescence co-localization, loss-of-function mutant (I267N), neurite outgrowth assay","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — yeast two-hybrid identification plus point-mutant validation in cells; two complementary methods but no in vitro reconstitution","pmids":["11157984"],"is_preprint":false},{"year":2002,"finding":"Active Rac1 and CDC42 form a tripartite complex with IQGAP1 and CLIP-170; IQGAP1 acts as the physical link between active CDC42/Rac1 and CLIP-170 at microtubule tips, thereby capturing microtubules at the leading edge to establish a polarized array and cell polarization.","method":"Co-immunoprecipitation, GFP-CLIP-170 imaging, dominant-negative IQGAP1 expression, microtubule array analysis","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — co-IP demonstrating tripartite complex, live-cell imaging of CLIP-170 mislocalization, dominant-negative epistasis; multiple orthogonal methods in a high-impact study","pmids":["12110184"],"is_preprint":false},{"year":2002,"finding":"IQGAP1 maintains CDC42 in the GTP-bound active state by inhibiting its GTPase activity; an IQGAP1 deletion mutant lacking part of the GAP-related domain (IQGAP1ΔGRD) increases intrinsic GTPase activity of CDC42 and blocks bradykinin-induced CDC42 activation, membrane translocation, and filopodia formation.","method":"IQGAP1 overexpression and ΔGRD mutant transfection, GTP-Cdc42 pulldown from cell lysates, in vitro GTPase assay, subcellular fractionation, filopodia scoring","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro GTPase reconstitution combined with in-cell domain-mutant loss-of-function and multiple cellular readouts; single rigorous study","pmids":["11948177"],"is_preprint":false},{"year":2003,"finding":"Activated CDC42 binds p85Cool-1/β-Pix, which directly associates with c-Cbl ubiquitin ligase, thereby preventing c-Cbl from binding the EGF receptor and catalyzing its ubiquitination; constitutively active CDC42(F28L) causes aberrant EGFR accumulation and sustained ERK activation leading to cellular transformation.","method":"Co-immunoprecipitation, ubiquitination assay, EGFR degradation assay, ERK activation assay, transformation assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — mechanistic co-IP identifying CDC42–p85Cool-1–c-Cbl complex, receptor ubiquitination assay, and transformation phenotype; multiple orthogonal methods","pmids":["14505571"],"is_preprint":false},{"year":2005,"finding":"In Xenopus oocyte wound healing, active CDC42 and active RhoA form distinct concentric zones around wound sites in a calcium-dependent manner; CDC42 occupies the middle of the F-actin array while RhoA is interior; these zones form before F-actin accumulation, require microtubules and F-actin, and depend on RhoA–CDC42 crosstalk.","method":"Fluorescence biosensor imaging (active CDC42/RhoA reporters) in wounded Xenopus oocytes, microtubule/actin depolymerization, Ca2+ chelation","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct live imaging of active GTPase zones with multiple perturbations; spatiotemporal zone formation established before cytoskeletal assembly","pmids":["15684032"],"is_preprint":false},{"year":2005,"finding":"In mitosis, Ect2 (GEF) and MgcRacGAP activate and then inactivate CDC42, respectively, to elevate GTP-CDC42 in metaphase; this CDC42 activation is required for proper kinetochore–microtubule attachment, chromosome alignment, and segregation.","method":"RNAi depletion of Ect2 and Cdc42, dominant-negative mutant expression, GTP-Cdc42 pulldown assay, immunofluorescence of spindle/kinetochores","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — RNAi plus dominant-negative epistasis, biochemical GTP-loading assay, direct mitotic phenotype; multiple approaches identifying GEF/GAP regulators","pmids":["15642749"],"is_preprint":false},{"year":2005,"finding":"Secramine inhibits CDC42 activation by a mechanism dependent on RhoGDI: it inhibits CDC42 membrane binding, GTP loading, and effector binding in a RhoGDI-dependent manner in vitro, and mimics dominant-negative CDC42 effects on Golgi protein export and polarization in cells.","method":"In vitro GTP-binding assay, membrane binding assay, effector binding assay with and without RhoGDI, RhoGDI-dependence experiments, cell-based Golgi traffic assay","journal":"Nature chemical biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mechanistic in vitro reconstitution showing RhoGDI-dependence of inhibition, validated by cellular phenocopy of dominant-negative CDC42; single rigorous study","pmids":["16408091"],"is_preprint":false},{"year":2008,"finding":"CDC42 and Rac1 drive endothelial lumen formation in 3D collagen matrices through downstream effectors Pak2, Pak4, Par3, Par6, and PKCε/ζ; RNAi knockdown of Pak2 or Pak4 markedly inhibits lumen formation, and disruption of the Cdc42–Par3–Par6–PKCζ polarity complex impairs lumenogenesis.","method":"RNAi knockdown, dominant-negative expression, 3D collagen matrix lumenogenesis assay, Pak phosphorylation assays","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — RNAi knockdown of multiple pathway components, dominant-negative epistasis, defined 3D morphogenesis assay; systematic dissection of the signaling complex","pmids":["18319301"],"is_preprint":false},{"year":2009,"finding":"CDC42 is essential for pancreatic tubulogenesis specifically for initiating microlumen formation and maintaining apical cell polarity; Cdc42 controls cell specification non-cell-autonomously by providing a correct microenvironment for multipotent progenitor fate choices.","method":"Conditional knockout in pancreatic lineage (mouse), histology, immunofluorescence of polarity markers, lineage tracing","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — tissue-specific conditional knockout with clear morphogenetic phenotype and mechanistic non-cell-autonomous finding; in vivo genetic approach","pmids":["19914171"],"is_preprint":false},{"year":2010,"finding":"During directed cell migration, CDC42 (with its exchange factor βPIX) localizes to intracytoplasmic vesicles and is recruited to the leading edge via Arf6-dependent membrane trafficking; inhibiting Arf6-dependent traffic abolishes polarized CDC42 and βPIX recruitment, Par6-aPKC complex polarization, and directed migration.","method":"Live-cell imaging of GFP-Cdc42-positive vesicles, Arf6 inhibition, immunofluorescence, cell polarization assay","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — live imaging of CDC42 vesicular trafficking, epistasis linking Arf6-dependent traffic to CDC42 polarity, multiple readouts; single rigorous study","pmids":["21173111"],"is_preprint":false},{"year":2010,"finding":"CDC42 regulates microtubule-dependent Golgi positioning; ARHGAP21 (Cdc42-specific GAP) knockdown inhibits Golgi repositioning to the centrosome; disrupting Cdc42 activation or the coatomer/Cdc42 binding interaction stimulates dynein-dependent Golgi motility, placing Cdc42 downstream of ARF1 and coatomer in regulating Golgi capture.","method":"siRNA knockdown of ARHGAP21, nocodazole washout Golgi repositioning assay, Golgi capture and motility assay in permeabilized cells, dynein inhibitory antibody","journal":"Traffic (Copenhagen, Denmark)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA and permeabilized-cell motility assay with antibody inhibition; single lab, multiple methods","pmids":["20525016"],"is_preprint":false},{"year":2013,"finding":"Missense variants in CDC42 variably perturb its switch between active/inactive states and/or its interaction with effectors, causing a clinically heterogeneous group of developmental disorders; in vitro functional assays confirmed altered GTPase activity and effector binding for specific mutants.","method":"Exome sequencing, in silico analysis, in vitro GTPase activity assay, effector-binding assays, in vivo zebrafish/animal models","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro biochemical characterization of multiple mutants with direct GTPase and effector binding assays; complemented by in vivo animal models","pmids":["29394990"],"is_preprint":false},{"year":2013,"finding":"CDC42 is required for primary ciliogenesis: CDC42 co-localizes with the exocyst component Sec10 at primary cilia, interacts with Sec10, and its knockout in kidney tubular epithelial cells causes ciliogenesis defects, cystogenesis, and MAPK activation; zebrafish cdc42 and sec10 show synergistic genetic interaction in the same pathway.","method":"Morpholino knockdown in zebrafish (genetic interaction), conditional knockout in mouse kidney, immunofluorescence (co-localization), co-IP (Sec10 interaction), MAPK assay","journal":"Journal of the American Society of Nephrology : JASN","confidence":"High","confidence_rationale":"Tier 2 / Strong — tissue-specific conditional KO phenotype plus zebrafish genetic epistasis plus co-IP; multiple orthogonal methods across two model organisms","pmids":["23766535"],"is_preprint":false},{"year":2013,"finding":"CDC42 conditional knockout in the nephrogenic lineage phenocopies Yap loss; ablation of CDC42 decreases nuclear localization of YAP and reduces YAP-dependent gene expression, placing CDC42 upstream of YAP nuclear translocation in nephron progenitor cells.","method":"Conditional knockout (mouse), microarray, immunofluorescence of YAP localization, gene expression analysis","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional KO with direct YAP localization measurement and gene expression readout; epistasis by genetic phenocopy, single lab","pmids":["23555292"],"is_preprint":false},{"year":2013,"finding":"A novel allosteric CDC42-selective inhibitor (identified by HTS) acts as a noncompetitive inhibitor with no activity toward Rho or Rac; it inhibits CDC42-related filopodia formation and cell migration in cells, demonstrating that allosteric inhibition of nucleotide binding is feasible for selectively targeting CDC42.","method":"High-throughput screening, GTPase biochemical assay, structure-activity relationship, filopodia formation assay, cell migration assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic characterization plus cellular validation; allosteric mechanism established biochemically","pmids":["23382385"],"is_preprint":false},{"year":2013,"finding":"Active CDC42 is both necessary and sufficient to form invadosome actin cores in multiple cell types; combined with Tks5 expression, CDC42-driven actin cores acquire proteolytic activity, defining a minimal molecular signature of invadosomes.","method":"Overexpression of constitutively active Cdc42, Tks5 co-expression, immunofluorescence, gelatin degradation assay","journal":"Cell adhesion & migration","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — overexpression gain-of-function across multiple cell lines with functional proteolytic assay; single lab","pmids":["24840388"],"is_preprint":false},{"year":2015,"finding":"During chemotaxis, local CDC42 signals (but not Rac, RhoA, or Ras signals) precede and predict cell turning; CDC42 has excitable properties (recurring local activity pulses revealed upon actin inhibition) and antagonizes RhoA, maintaining a steep spatial activity gradient that directs chemotactic steering.","method":"Fluorescence biosensors (FRET/FLIM) in neutrophil-like PLB-985 cells, photorelease of chemoattractant, actin polymerization inhibition, GTPase activity imaging","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — live biosensor imaging with spatiotemporal resolution, chemoattractant photorelease, and actin inhibition epistasis; multiple GTPases compared with multiple biosensors","pmids":["26689677"],"is_preprint":false},{"year":2017,"finding":"CDC42 activity is required for optogenetically induced cell turning; the shape of the Cdc42 gradient is set by the spatial distribution of GEFs, not by transport, with a steep Cdc42 gradient maximizing directionality; a GAP (β2-chimaerin, localized at the cell tip by Cdc42 and Rac1 feedbacks) shapes the Rac1 gradient.","method":"Optogenetics (photoactivatable Rac1/Cdc42), micropatterned GEF substrates, FRET biosensors, live-cell imaging","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — optogenetic gain-of-function with biosensor readout, multiple GTPase conditions, mechanistic dissection of gradient-shaping by GEF/GAP spatial distribution","pmids":["30446664"],"is_preprint":false},{"year":2017,"finding":"Cytoplasmic YAP positively regulates CDC42 activity in endothelial cells; CDC42 deletion causes severe defects in endothelial cell migration during retinal angiogenesis, and overexpression of cytoplasmic YAP (YAPS127D) partially rescues Yap/Taz-deficient migration defects through CDC42.","method":"Conditional knockout (endothelial-specific Yap/Taz and Cdc42), rescue with YAPS127D, retinal angiogenesis assay, GTPase activity assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with conditional KO and rescue, direct CDC42 activity measurement; single lab","pmids":["28973878"],"is_preprint":false},{"year":2018,"finding":"CDC42 binds PAK4 through an extended interface beyond the canonical CRIB domain, including additional contacts between the PAK4 kinase C-lobe, CDC42, and the PAK4 polybasic region; these additional contacts modulate kinase activity and increase CDC42 binding affinity compared to CRIB domain alone.","method":"X-ray crystallography, solution scattering (SAXS), kinase activity assay, binding affinity measurement","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus SAXS for full-length complex, kinase activity assay with defined mechanistic consequence; rigorous multi-method study","pmids":["29295922"],"is_preprint":false},{"year":2019,"finding":"Endothelial-specific deletion of CDC42 elicits cerebrovascular malformations resembling cerebral cavernous malformations (CCM) by increasing MEKK3-MEK5-ERK5 signaling and overexpression of KLF2 and KLF4; co-inactivation of Klf4 reduces malformation severity; CDC42 interacts with CCM proteins, and CCM3 promotes CDC42 activity in endothelial cells.","method":"Inducible endothelial-specific conditional knockout (mouse), retinal angiogenesis assay, signaling pathway analysis (western blot), genetic rescue (Klf4 co-KO), co-immunoprecipitation (CCM3–CDC42)","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo conditional KO, genetic epistasis rescue, co-IP for complex identification, signaling pathway analysis; multiple orthogonal methods","pmids":["30732528"],"is_preprint":false},{"year":2021,"finding":"Activated GTP-bound CDC42 and its effector IQGAP1 are required for tumor microvesicle (MV) shedding; activated CDC42 also prevents EGFR internalization to maintain sustained EGF signaling that facilitates MV release, and blocking CDC42 signaling reduces MV-promoted tumor angiogenesis in vivo.","method":"Co-immunoprecipitation (CDC42–IQGAP1), dominant-negative and constitutively active mutants, MV shedding assay, EGFR internalization assay, in vivo tumor angiogenesis assay","journal":"Journal of extracellular vesicles","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, functional mutant analysis, and in vivo validation; single lab","pmids":["33473262"],"is_preprint":false},{"year":2022,"finding":"The microprotein pTINCR binds to CDC42 and promotes CDC42 SUMOylation and activation, triggering a pro-differentiation cascade in epithelial cells; this places pTINCR as a positive upstream regulator of CDC42 activity via a SUMO-dependent mechanism.","method":"Co-immunoprecipitation (pTINCR–CDC42), SUMOylation assay, gain- and loss-of-function studies, in vitro differentiation assay, patient-derived xenograft","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, SUMOylation assay, in vivo xenograft; novel mechanism but single lab","pmids":["36369429"],"is_preprint":false},{"year":2023,"finding":"mTORC2 phosphorylates NDRG1 at Ser336 during fasting, and phosphorylated NDRG1 cooperates with CDC42 and its effectors/regulators to orchestrate mitochondrial fission; Cdc42-deficient cells display fission failure phenotypes similar to NDRG1-Ser336Ala mutants and RictorKO cells.","method":"Time-lapse imaging, siRNA screen, epistasis experiments, proteomics, Cdc42-deficient cells (genetic), phosphorylation-deficient mutants","journal":"Nature cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with multiple pathway components, live imaging of mitochondrial fission, proteomic identification; single lab","pmids":["37386153"],"is_preprint":false}],"current_model":"CDC42 is a Rho-family GTPase molecular switch that, when GTP-bound (activated by GEFs such as Dbl, βPIX, Ect2; inhibited by GAPs; sequestered in cytosol by RhoGDI via the Rho insert region; and membrane-anchored via C-terminal prenylation/carboxyl methylation), engages a spectrum of effectors—including PAK1/2/4, MRCK-α, IQGAP1, WASP/N-WASP–Arp2/3, Par6–aPKC, and CLIP-170 via IQGAP1—to drive actin polymerization, filopodia/invadosome formation, cell polarity establishment, phagocytosis, vesicle trafficking (including Golgi positioning and microvesicle shedding), mitosis (kinetochore–microtubule attachment via Ect2/MgcRacGAP regulation), mitochondrial fission (via NDRG1 downstream of mTORC2), and chemotactic steering through locally excitable, spatially steep GTPase activity gradients that antagonize RhoA."},"narrative":{"mechanistic_narrative":"CDC42 is a Rho-family GTP-binding protein and conserved molecular switch that cycles between membrane-associated active and cytosolic inactive states to govern actin-based morphogenesis, cell polarity, and intracellular trafficking [PMID:2122236, PMID:2124704, PMID:7891688]. Its functional homology to yeast CDC42 was established by complementation, and its localization is controlled by C-terminal CAAX isoprenylation and GTP-stimulated carboxyl methylation that partition it between membranes and cytosol [PMID:2122236, PMID:2124704, PMID:2120220, PMID:1526984]. The switch is regulated by a GAP that stimulates GTP hydrolysis on wild-type but not Val-12 CDC42 [PMID:1939135], by GEFs including Dbl, Ect2 and βPIX [PMID:1429634, PMID:15642749, PMID:21173111], and by RhoGDI, which binds prenylated CDC42 with high affinity through the Rho insert region to inhibit GDP dissociation and extract it from membranes, enabling cytosol–membrane cycling without being required for membrane targeting itself [PMID:1429634, PMID:9334181, PMID:8626553, PMID:11583574]. In the GTP-bound state CDC42 engages a spectrum of effectors to drive distinct outputs: it triggers filopodia and peripheral actin microspikes [PMID:7891688], activates the serine kinases PAK and the CDC42-selective PAK4 and MRCK-α to control actin-myosin contractility and substrate phosphorylation [PMID:7744004, PMID:9822598, PMID:9418861, PMID:29295922], and recruits WASp–Arp2/3 to build actin-rich phagocytic cups and invadosome cores [PMID:11580754, PMID:24840388]. Through IQGAP1 it integrates Ca2+/calmodulin signaling, sustains its own GTP-loaded state, and links to CLIP-170 to capture microtubules and establish polarized arrays [PMID:8670801, PMID:9867866, PMID:12110184, PMID:11948177]. CDC42 establishes and maintains cell polarity via the Par6–aPKC complex and Arf6-dependent vesicular delivery to the leading edge, directing chemotactic steering through locally excitable GTPase gradients that antagonize RhoA and are shaped by the spatial distribution of GEFs [PMID:18319301, PMID:21173111, PMID:26689677, PMID:30446664, PMID:15684032]. Beyond migration, CDC42 functions in epithelial and endothelial tubulogenesis and lumen formation, primary ciliogenesis via the exocyst component Sec10, mitotic kinetochore–microtubule attachment through Ect2/MgcRacGAP, Golgi positioning, and mTORC2/NDRG1-coupled mitochondrial fission [PMID:18319301, PMID:19914171, PMID:23766535, PMID:15642749, PMID:20525016, PMID:37386153]. Missense variants that perturb the active/inactive switch or effector binding cause a clinically heterogeneous group of developmental disorders [PMID:29394990].","teleology":[{"year":1990,"claim":"Established that the human G25K protein is a bona fide GTP-binding ortholog of yeast CDC42, defining it as a conserved molecular switch whose membrane association is set by lipid modification.","evidence":"cDNA cloning with yeast complementation and GTP-binding assays; metabolic [3H]mevalonate labeling with lovastatin inhibition and fractionation","pmids":["2122236","2124704","2120220"],"confidence":"High","gaps":["Did not identify downstream effectors","Did not define which cellular processes the switch controls in human cells"]},{"year":1992,"claim":"Defined the regulatory inputs to the switch by purifying a CDC42-specific GAP and showing RhoGDI inhibits GDP dissociation and extracts CDC42 from membranes, framing the GEF/GAP/GDI control logic.","evidence":"Protein purification of platelet GAP with mutant specificity controls; GDP dissociation, membrane extraction, and carboxyl methylation assays with purified RhoGDI","pmids":["1939135","1429634","1526984"],"confidence":"High","gaps":["GAP identity at the gene level not resolved here","Structural basis of GDI binding not yet defined"]},{"year":1995,"claim":"Connected active CDC42 to its cellular output, showing it drives filopodia formation and directly activates the PAK serine kinase in a GTP-dependent manner, establishing the GTPase-to-actin signaling axis.","evidence":"Microinjection of constitutively active and dominant-negative CDC42 with phalloidin imaging; purified PAK GTP-dependent binding and autophosphorylation/kinase assays","pmids":["7891688","7744004","8034624"],"confidence":"High","gaps":["How PAK activation links to actin remodeling not fully traced","Did not establish the full effector repertoire"]},{"year":1996,"claim":"Identified IQGAP1/2 as effectors that bind GTP-CDC42 and inhibit its GTPase activity, and mapped the Rho insert region as the GDI-interaction determinant separable from effector binding, refining switch-state regulation.","evidence":"Affinity purification, reciprocal co-IP, GTPase assays, immunofluorescence; Cdc42/Ras chimera domain-swap mutagenesis; fluorescence-spectroscopy Kd determination","pmids":["8670801","8702968","9334181","8626553"],"confidence":"High","gaps":["Functional consequence of IQGAP inhibition of GTP hydrolysis in cells unresolved","Insert-region role distinct from membrane targeting not yet tested"]},{"year":1998,"claim":"Expanded the effector network to CDC42-specific kinases and the actin nucleation machinery, defining how CDC42 produces distinct cytoskeletal and contractile outputs and drives phagocytosis.","evidence":"Co-IP and localization of PAK4 with kinase-dead/binding mutants; MRCK-α in vitro kinase assay on myosin light chain; dominant-negative CDC42 in FcgammaR phagocytosis with distinct morphological phenotypes","pmids":["9822598","9418861","9799231"],"confidence":"High","gaps":["Spatial coordination of multiple effectors in one cell not resolved","Substrate specificity of MRCK-α versus PAK4 in vivo unclear"]},{"year":2001,"claim":"Demonstrated RhoGDI-dependent cytosol–membrane cycling and PAK-mediated phosphorylation of merlin, and tied CDC42-WASp-Arp2/3 to phagocytic cup actin assembly, mechanistically linking the switch to traffic, growth control, and engulfment.","evidence":"R66E GDI-binding-deficient mutant with fractionation/imaging; in vitro and in vivo PAK kinase assay on merlin Ser518; dominant-negative CDC42, WASp-KO, and Arp2/3 inhibition in phagocytosis","pmids":["11583574","11719502","11580754"],"confidence":"High","gaps":["GDI cycling kinetics in living cells not measured","How GDI release is triggered physiologically not defined"]},{"year":2002,"claim":"Established CDC42 as a polarity organizer linking actin to microtubules via the IQGAP1–CLIP-170 tripartite complex, and showed IQGAP1 sustains the GTP-bound state, connecting effector binding to gradient maintenance.","evidence":"Co-IP of tripartite complex, GFP-CLIP-170 imaging, dominant-negative IQGAP1; IQGAP1 ΔGRD mutant with GTP-Cdc42 pulldown and filopodia readouts","pmids":["12110184","11948177"],"confidence":"High","gaps":["How microtubule capture feeds back on CDC42 activity not resolved","Quantitative contribution of IQGAP1 to gradient steepness unknown"]},{"year":2005,"claim":"Visualized spatially patterned active-CDC42 zones and identified the mitotic Ect2/MgcRacGAP GEF/GAP pair, establishing that CDC42 functions through spatially confined activity and operates in mitosis as well as cortical remodeling.","evidence":"Active-GTPase biosensor imaging in wounded Xenopus oocytes with cytoskeletal/Ca2+ perturbation; RNAi and dominant-negative epistasis with GTP-Cdc42 pulldown and kinetochore imaging","pmids":["15684032","15642749"],"confidence":"High","gaps":["Molecular basis of zone segregation from RhoA not defined","How mitotic GEF/GAP cycling is timed unresolved"]},{"year":2010,"claim":"Showed that polarized CDC42 activity during migration is established by Arf6-dependent vesicular delivery of CDC42/βPIX to the leading edge and that CDC42 controls microtubule-dependent Golgi positioning, coupling the switch to membrane trafficking.","evidence":"Live imaging of GFP-Cdc42 vesicles with Arf6 inhibition and polarity readouts; ARHGAP21 siRNA with Golgi repositioning and permeabilized-cell motility assays","pmids":["21173111","20525016"],"confidence":"High","gaps":["How Arf6 traffic is spatially restricted not defined","Direct coatomer–CDC42 interaction at gene level not fully resolved"]},{"year":2013,"claim":"Defined in vivo developmental and disease roles—tubulogenesis, ciliogenesis via Sec10, YAP regulation—and linked germline CDC42 missense variants perturbing the switch to human developmental disorders.","evidence":"Tissue-specific conditional knockouts (pancreas, kidney) with polarity/YAP readouts; zebrafish cdc42/sec10 epistasis and co-IP; exome sequencing with in vitro GTPase/effector assays and animal models","pmids":["19914171","23766535","23555292","29394990"],"confidence":"High","gaps":["Genotype-phenotype rules for variant classes incomplete","Tissue-specific effector usage not fully mapped"]},{"year":2018,"claim":"Resolved the structural basis of effector engagement, showing CDC42 binds PAK4 through an extended interface beyond the CRIB domain that modulates kinase activity and binding affinity.","evidence":"X-ray crystallography and SAXS of the full-length complex with kinase activity and affinity measurements","pmids":["29295922"],"confidence":"High","gaps":["Whether other effectors use analogous extended interfaces unknown","In-cell relevance of the extended contacts not tested"]},{"year":2019,"claim":"Established CDC42 as a vascular morphogenesis regulator whose loss causes cavernous-malformation-like lesions via MEKK3-ERK5-KLF2/4 signaling, and identified CCM3 as a promoter of CDC42 activity.","evidence":"Inducible endothelial conditional knockout, retinal angiogenesis, signaling/western analysis, Klf4 co-KO rescue, CCM3–CDC42 co-IP","pmids":["30732528"],"confidence":"High","gaps":["Mechanism by which CCM3 activates CDC42 not defined","How CDC42 loss elevates MEKK3 signaling not fully traced"]},{"year":2023,"claim":"Extended CDC42 function to organelle dynamics and identified novel upstream activators, implicating it in mTORC2/NDRG1-driven mitochondrial fission and in pTINCR/SUMO-dependent activation, and in tumor microvesicle shedding.","evidence":"Genetic epistasis, siRNA screens, proteomics and live imaging in Cdc42-deficient cells; co-IP and SUMOylation assays; MV shedding and EGFR internalization assays with mutants","pmids":["37386153","36369429","33473262"],"confidence":"Medium","gaps":["Direct CDC42 effectors in mitochondrial fission not identified","These single-lab mechanisms await independent confirmation"]},{"year":null,"claim":"How the same CDC42 switch is allosterically partitioned in real time among its many effectors to specify distinct outputs (filopodia, polarity, mitosis, fission) within one cell remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model linking spatial GTP-loading to effector selection","Quantitative effector competition in vivo not measured","Endogenous determinants of GDI release versus effector engagement undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003924","term_label":"GTPase activity","supporting_discovery_ids":[0,2,26,35]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[6,40,41]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[7,15,16]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,6,8,22]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[1,22,33]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[15,22,34]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[33]},{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[36]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[6,7,40,41]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[31,32,36,35]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[13,29]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[33,34,45]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[17,23]}],"complexes":["CDC42–RhoGDI heterodimer","IQGAP1–CLIP-170 tripartite complex","Par6–aPKC polarity complex","WASp–Arp2/3"],"partners":["RHOGDI","IQGAP1","PAK4","MRCK-Α","WASP","ECT2","SEC10","CCM3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P60953","full_name":"Cell division control protein 42 homolog","aliases":["G25K GTP-binding protein"],"length_aa":191,"mass_kda":21.3,"function":"Plasma membrane-associated small GTPase which cycles between an active GTP-bound and an inactive GDP-bound state. In active state binds to a variety of effector proteins to regulate cellular responses. Involved in epithelial cell polarization processes. Regulates the bipolar attachment of spindle microtubules to kinetochores before chromosome congression in metaphase (PubMed:15642749). Regulates cell migration (PubMed:17038317, PubMed:22843693). In neurons, plays a role in the extension and maintenance of the formation of filopodia, thin and actin-rich surface projections (PubMed:14978216). Required for DOCK10-mediated spine formation in Purkinje cells and hippocampal neurons. In podocytes, facilitates filopodia and podosomes formation upon DOCK11-activation (PubMed:33523862). Upon activation by CaMKII, modulates dendritic spine structural plasticity by relaying CaMKII transient activation to synapse-specific, long-term signaling (By similarity). Also plays a role in phagocytosis through organization of the F-actin cytoskeleton associated with forming phagocytic cups (PubMed:26465210). Upon activation by PLEKHG4B, involved in actin cytoskeletal remodeling during epithelial cell-cell junction formation (PubMed:33310911)","subcellular_location":"Cell membrane; Cytoplasm, cytoskeleton, microtubule organizing center, centrosome; Cytoplasm, cytoskeleton, spindle; Midbody; Cell projection, dendrite","url":"https://www.uniprot.org/uniprotkb/P60953/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/CDC42","classification":"Common 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TMEM161B","url":"https://www.omim.org/entry/621178"},{"mim_id":"621118","title":"V-SET AND TRANSMEMBRANE DOMAINS-CONTAINING PROTEIN 5; VSTM5","url":"https://www.omim.org/entry/621118"},{"mim_id":"621092","title":"IQ MOTIF-CONTAINING GTPase-ACTIVATING PROTEIN 3; IQGAP3","url":"https://www.omim.org/entry/621092"},{"mim_id":"620665","title":"PLECKSTRIN HOMOLOGY DOMAIN- AND RhoGEF DOMAIN-CONTAINING PROTEIN G4B; PLEKHG4B","url":"https://www.omim.org/entry/620665"},{"mim_id":"620170","title":"SPERMATOGENIC FAILURE 78; SPGF78","url":"https://www.omim.org/entry/620170"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Microtubules","reliability":"Supported"},{"location":"Cytokinetic bridge","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/CDC42"},"hgnc":{"alias_symbol":["G25K","CDC42Hs"],"prev_symbol":[]},"alphafold":{"accession":"P60953","domains":[{"cath_id":"3.40.50.300","chopping":"1-176","consensus_level":"high","plddt":96.1908,"start":1,"end":176}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P60953","model_url":"https://alphafold.ebi.ac.uk/files/AF-P60953-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P60953-F1-predicted_aligned_error_v6.png","plddt_mean":93.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CDC42","jax_strain_url":"https://www.jax.org/strain/search?query=CDC42"},"sequence":{"accession":"P60953","fasta_url":"https://rest.uniprot.org/uniprotkb/P60953.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P60953/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P60953"}},"corpus_meta":[{"pmid":"7891688","id":"PMC_7891688","title":"The Ras-related protein Cdc42Hs 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biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution (GTP-binding), functional complementation in yeast, replicated across two independent groups (PMIDs 2122236 and 2124704)\",\n      \"pmids\": [\"2122236\", \"2124704\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1990,\n      \"finding\": \"CDC42Hs (G25K) undergoes isoprenoid (farnesyl) modification at its C-terminal CAAX motif, and this modification regulates its association with cell membranes versus cytosol.\",\n      \"method\": \"Metabolic labeling with [3H]mevalonate, 2D gel electrophoresis, immunoblotting, lovastatin inhibition, subcellular fractionation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct metabolic labeling, pharmacological inhibition, fractionation showing membrane/cytosol redistribution upon lovastatin treatment\",\n      \"pmids\": [\"2120220\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"A GTPase-activating protein (GAP) for CDC42Hs was purified from human platelets; it stimulates GTP hydrolysis on wild-type CDC42Hs but not on the Val-12 mutant, and shows weak cross-reactivity with Rho but not with Ras or Rap.\",\n      \"method\": \"Protein purification (~3500-fold), GTPase activity assay, mutant specificity analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro biochemical reconstitution with purified components and mutagenesis specificity controls\",\n      \"pmids\": [\"1939135\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"Rho-GDI (GDP-dissociation inhibitor) inhibits GDP dissociation from CDC42Hs and stimulates release of CDC42Hs from plasma membranes. The purified brain GDI also inhibits Dbl-catalyzed GDP dissociation from CDC42Hs.\",\n      \"method\": \"Protein purification, GDP dissociation assay, membrane extraction assay, immunoblotting\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro biochemical reconstitution with purified proteins and multiple orthogonal functional assays\",\n      \"pmids\": [\"1429634\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"CDC42Hs (G25K) undergoes GTP-stimulated carboxyl methylation in brain; it exists as a heterodimer with a 28-kDa protein (RhoGDI), and the associated GDI decreases methylation efficiency and alters guanine nucleotide specificity.\",\n      \"method\": \"Protein purification, carboxyl methylation assay, two-dimensional electrophoresis, subcellular fractionation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro assay from a single lab, single methodology set\",\n      \"pmids\": [\"1526984\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"GTP-bound CDC42Hs directly associates with the p85 subunit of PI 3-kinase via the Rho-GAP homology domain of p85, and this interaction stimulates PI 3-kinase activity 2–4-fold; the effector domain mutant T35A abolishes binding.\",\n      \"method\": \"GST pulldown with purified recombinant proteins, co-immunoprecipitation from cell lysates, PI 3-kinase activity assay, effector-domain mutant analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with purified proteins, mutagenesis, and functional enzyme assay in a single comprehensive study\",\n      \"pmids\": [\"8034624\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Microinjection of constitutively active CDC42Hs into Swiss 3T3 fibroblasts induces peripheral actin microspikes and filopodia; bradykinin activates endogenous CDC42Hs to produce the same effects, which are blocked by dominant-negative CDC42Hs(T17N).\",\n      \"method\": \"Microinjection, phalloidin staining, time-lapse phase-contrast microscopy, dominant-negative inhibition\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function (dominant negative) and gain-of-function microinjection with direct cytoskeletal readout; replicated across multiple conditions\",\n      \"pmids\": [\"7891688\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"PAK (hPAK65) is a serine kinase that binds Rac1 and CDC42Hs in a GTP-dependent manner; GTP-bound CDC42Hs or Rac1 induces autophosphorylation of PAK on serine residues, which activates its kinase activity toward myelin basic protein independently of continued GTPase binding.\",\n      \"method\": \"Protein purification from neutrophil cytosol, GTP-dependent binding assay, in vitro autophosphorylation assay, kinase activity assay toward exogenous substrate\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted kinase activation in vitro with purified components, phosphorylation site determination, and substrate assay in a single rigorous study\",\n      \"pmids\": [\"7744004\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"CDC42Hs translocates from the membrane skeleton to the cytoskeleton in platelets stimulated by TRAP or ADP; this translocation is mediated by αIIbβ3 integrin activation and requires actin polymerization and protein-tyrosine kinase activity.\",\n      \"method\": \"Subcellular fractionation, immunoblotting, cytochalasin and genistein inhibition, integrin blockade\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct fractionation with pharmacological dissection, single lab, multiple inhibitory approaches\",\n      \"pmids\": [\"7542236\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"IQGAP1 (p195) is a CDC42Hs effector: it binds preferentially to GTP-bound CDC42Hs and Rac, inhibits CDC42Hs GTPase activity, and co-immunoprecipitates with CDC42Hs from cell lysates. IQGAP1 localizes to lamellipodia and ruffles where it co-localizes with actin.\",\n      \"method\": \"Affinity chromatography (GTP-Cdc42Hs bead purification), GTPase activity assay, co-immunoprecipitation, immunofluorescence, yeast CDC42/CDC24 pathway inhibition assay\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP, functional GTPase assay, subcellular localization, yeast genetic validation; multiple orthogonal methods\",\n      \"pmids\": [\"8670801\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"IQGAP2 (p175) interacts with CDC42Hs in a manner that is less nucleotide-dependent than IQGAP1; both IQGAP1 and IQGAP2 require the switch I domain and an insert region unique to Rho-family proteins for CDC42Hs binding.\",\n      \"method\": \"Protein purification from rabbit liver cytosol, pulldown with GTP/GDP-Cdc42Hs, chimeric mutant analysis, microsequencing\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — purified protein interaction with domain mapping using chimeric mutants, single lab\",\n      \"pmids\": [\"8702968\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"The Rho insert region (residues 122–134) of CDC42Hs is required for RhoGDI-mediated inhibition of GDP dissociation and GTP hydrolysis, and for GDI-stimulated membrane release; this region is not required for effector (PAK, GEF Dbl, or GAP) interactions.\",\n      \"method\": \"Cdc42Hs/Ha-Ras chimeric mutant construction, GDP dissociation assay, GTPase activity assay, membrane release assay, effector binding assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — domain-swap mutagenesis with multiple functional reconstitution assays, clear mechanistic conclusion, single lab\",\n      \"pmids\": [\"9334181\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"RhoGDI binds GDP- and GTP-bound CDC42Hs with similar affinity (~30 nM Kd) as measured by direct fluorescence spectroscopy; the carboxyl-terminal domain of GDI confers high-affinity binding; prenylation of CDC42Hs is required for GDI-induced fluorescence quenching.\",\n      \"method\": \"Fluorescence spectroscopy using Mant-GDP-loaded CDC42Hs, binding titration, GDI/LD4 chimera analysis, truncation mutants\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct biophysical assay with multiple mutants, clear Kd determination, rigorous controls for prenylation requirement\",\n      \"pmids\": [\"8626553\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Dominant-negative CDC42Hs(T17N) inhibits serum-stimulated cell cycle progression at G1/S in a p38-dependent manner, but Rac1 dominant negative does not produce the same block, demonstrating a specific and distinct role for CDC42Hs in cell cycle inhibition via the p38 pathway.\",\n      \"method\": \"Quantitative microinjection of dominant-negative GTPases into fibroblasts, cell cycle analysis, pharmacological inhibition of p38\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — microinjection with cell cycle readout and pathway inhibitor epistasis, single lab\",\n      \"pmids\": [\"9148940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"The CDC42Hs(F28L) fast-cycling mutant (which undergoes spontaneous GTP-GDP exchange while retaining GTPase activity) activates JNK1, induces filopodia, and causes oncogenic transformation including anchorage-independent growth and reduced contact inhibition.\",\n      \"method\": \"Site-directed mutagenesis, JNK reporter assays, filopodia formation by immunofluorescence, focus formation and soft-agar growth assays\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — engineered gain-of-function mutant with multiple transformation readouts, single lab\",\n      \"pmids\": [\"9368762\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"PAK4 is a CDC42Hs-specific effector kinase that interacts with activated CDC42Hs via its GBD; co-expression of PAK4 and constitutively active CDC42Hs redistributes PAK4 to the Golgi and induces filopodia and actin polymerization in a manner dependent on PAK4 kinase activity and CDC42Hs binding.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence localization, kinase-dead and binding-deficient mutant analysis, brefeldin A treatment, actin staining\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct interaction, subcellular redistribution, multiple domain mutants defining kinase activity and GBD requirement; multiple orthogonal methods\",\n      \"pmids\": [\"9822598\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"MRCK-α (myotonic dystrophy kinase-related Cdc42-binding kinase) binds GTP-Cdc42 through a PAK-like p21-binding domain and phosphorylates non-muscle myosin light chain at Ser19, driving actin-myosin contractility; kinase-dead MRCK-α blocks Cdc42V12-dependent peripheral microspikes and focal complexes.\",\n      \"method\": \"Recombinant protein binding assay, in vitro kinase assay (myosin light chain phosphorylation), microinjection, kinase-dead and Cdc42-binding-deficient mutants, immunofluorescence\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase reconstitution, substrate identification, and in-cell epistasis with domain mutants; multiple orthogonal methods\",\n      \"pmids\": [\"9418861\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Dominant-negative forms of both Rac1 and CDC42 inhibit Fcγ receptor-mediated phagocytosis in macrophages, but with distinct phenotypes: CDC42 inhibition produces pedestal-like structures while Rac1 inhibition traps particles in thin membrane protrusions, indicating cooperative but distinct roles in phagocytic cup assembly.\",\n      \"method\": \"Stable transfection of dominant-negative GTPases in RBL-2H3 cells, F-actin staining, particle internalization assay, Clostridium difficile toxin B inhibition\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — stable dominant-negative cell lines, direct phagocytosis assay, distinct morphological phenotypes identifying stage-specific functions\",\n      \"pmids\": [\"9799231\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Integrin-dependent adhesion to fibronectin activates CDC42 (and Rac1), as evidenced by activation of the downstream effector PAK; dominant-negative CDC42 inhibits cell spreading, and epistasis experiments indicate integrins activate CDC42 first, which then activates Rac1 to drive spreading.\",\n      \"method\": \"PAK activation assay (downstream readout), dominant-negative GTPase expression, cell spreading assay on fibronectin\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional epistasis using dominant negatives, indirect CDC42 activation readout via PAK, single lab\",\n      \"pmids\": [\"9658176\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"IQGAP1 integrates Ca2+/calmodulin and CDC42 signaling: in the absence of Ca2+, IQGAP1 binds GTP-Cdc42 and inhibits its GTPase activity; Ca2+/calmodulin dissociates Cdc42 from IQGAP1 and restores GTP hydrolysis. Calmodulin binds the IQ motifs and calponin homology domain of IQGAP1; F-actin competes with Ca2+/calmodulin for the calponin homology domain.\",\n      \"method\": \"In vitro GTPase activity assay, in vitro binding assay, cell lysate co-immunoprecipitation, Ca2+ titration\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — reconstituted biochemistry with multiple domain-specific interactions and quantified Ca2+ dependence, single rigorous study\",\n      \"pmids\": [\"9867866\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Active CDC42Hs and Rac1 GTPases cause perinuclear collapse of the vimentin intermediate filament network; this effect is independent of CRIB-mediated (PAK/JNK) pathways but is associated with actin reorganization and requires tyrosine phosphorylation events.\",\n      \"method\": \"Expression of activated GTPases and effector-loop mutants, immunofluorescence of vimentin, pharmacological inhibition (genistein, staurosporin, cytochalasin D), phosphorylation analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — effector-loop mutants and pharmacological epistasis, multiple inhibitor controls; single lab\",\n      \"pmids\": [\"10900195\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"p21-activated kinase (PAK) phosphorylates merlin (NF2 tumor suppressor) at serine 518 downstream of activated Rac and CDC42; both in vivo (cell-based) and in vitro kinase assays confirmed direct PAK-mediated phosphorylation of merlin.\",\n      \"method\": \"In vitro kinase assay, in vivo kinase assay in cells, expression of activated Rac and Cdc42, site-directed analysis (Ser518)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct in vitro phosphorylation assay combined with in vivo validation, site-specific analysis; single rigorous study\",\n      \"pmids\": [\"11719502\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"RhoGDI is required for cycling of CDC42Hs between membranes and cytosol: a CDC42Hs R66E mutant defective in RhoGDI binding is found exclusively in membrane fractions (predominantly Golgi), whereas wild-type CDC42Hs redistributes to the cytosol when RhoGDI is overexpressed; RhoGDI binding is not required for membrane targeting or filopodia induction.\",\n      \"method\": \"Site-directed mutagenesis (R66E), subcellular fractionation, immunofluorescence, RhoGDI overexpression\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — engineered binding-deficient mutant, fractionation, and imaging; multiple orthogonal approaches clearly defining GDI-dependent cycling vs. membrane targeting\",\n      \"pmids\": [\"11583574\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"During invasin/β1-integrin-mediated phagocytosis in macrophages, CDC42Hs activates WASp and the Arp2/3 complex to drive actin-rich phagocytic cup formation; dominant-negative CDC42Hs, WASp-knockout, and Arp2/3 inhibition each block cup formation and uptake.\",\n      \"method\": \"Microinjection of dominant-negative N17CDC42Hs, WASp-KO macrophages, Arp2/3 inhibitor microinjection, F-actin staining, internalization assay\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function at multiple nodes in the same pathway (GTPase, effector, Arp2/3), genetic KO and biochemical inhibition with direct phagocytic readout\",\n      \"pmids\": [\"11580754\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"CDC42Hs facilitates cytoskeletal reorganization and neurite outgrowth through the adaptor protein IRS-58 (58-kDa insulin receptor substrate); an IRS-58 mutant unable to bind CDC42Hs (I267N) fails to localize to F-actin and cannot induce filopodia or neurite outgrowth.\",\n      \"method\": \"Yeast two-hybrid, immunofluorescence co-localization, loss-of-function mutant (I267N), neurite outgrowth assay\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — yeast two-hybrid identification plus point-mutant validation in cells; two complementary methods but no in vitro reconstitution\",\n      \"pmids\": [\"11157984\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Active Rac1 and CDC42 form a tripartite complex with IQGAP1 and CLIP-170; IQGAP1 acts as the physical link between active CDC42/Rac1 and CLIP-170 at microtubule tips, thereby capturing microtubules at the leading edge to establish a polarized array and cell polarization.\",\n      \"method\": \"Co-immunoprecipitation, GFP-CLIP-170 imaging, dominant-negative IQGAP1 expression, microtubule array analysis\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — co-IP demonstrating tripartite complex, live-cell imaging of CLIP-170 mislocalization, dominant-negative epistasis; multiple orthogonal methods in a high-impact study\",\n      \"pmids\": [\"12110184\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"IQGAP1 maintains CDC42 in the GTP-bound active state by inhibiting its GTPase activity; an IQGAP1 deletion mutant lacking part of the GAP-related domain (IQGAP1ΔGRD) increases intrinsic GTPase activity of CDC42 and blocks bradykinin-induced CDC42 activation, membrane translocation, and filopodia formation.\",\n      \"method\": \"IQGAP1 overexpression and ΔGRD mutant transfection, GTP-Cdc42 pulldown from cell lysates, in vitro GTPase assay, subcellular fractionation, filopodia scoring\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro GTPase reconstitution combined with in-cell domain-mutant loss-of-function and multiple cellular readouts; single rigorous study\",\n      \"pmids\": [\"11948177\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Activated CDC42 binds p85Cool-1/β-Pix, which directly associates with c-Cbl ubiquitin ligase, thereby preventing c-Cbl from binding the EGF receptor and catalyzing its ubiquitination; constitutively active CDC42(F28L) causes aberrant EGFR accumulation and sustained ERK activation leading to cellular transformation.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, EGFR degradation assay, ERK activation assay, transformation assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mechanistic co-IP identifying CDC42–p85Cool-1–c-Cbl complex, receptor ubiquitination assay, and transformation phenotype; multiple orthogonal methods\",\n      \"pmids\": [\"14505571\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"In Xenopus oocyte wound healing, active CDC42 and active RhoA form distinct concentric zones around wound sites in a calcium-dependent manner; CDC42 occupies the middle of the F-actin array while RhoA is interior; these zones form before F-actin accumulation, require microtubules and F-actin, and depend on RhoA–CDC42 crosstalk.\",\n      \"method\": \"Fluorescence biosensor imaging (active CDC42/RhoA reporters) in wounded Xenopus oocytes, microtubule/actin depolymerization, Ca2+ chelation\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct live imaging of active GTPase zones with multiple perturbations; spatiotemporal zone formation established before cytoskeletal assembly\",\n      \"pmids\": [\"15684032\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"In mitosis, Ect2 (GEF) and MgcRacGAP activate and then inactivate CDC42, respectively, to elevate GTP-CDC42 in metaphase; this CDC42 activation is required for proper kinetochore–microtubule attachment, chromosome alignment, and segregation.\",\n      \"method\": \"RNAi depletion of Ect2 and Cdc42, dominant-negative mutant expression, GTP-Cdc42 pulldown assay, immunofluorescence of spindle/kinetochores\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — RNAi plus dominant-negative epistasis, biochemical GTP-loading assay, direct mitotic phenotype; multiple approaches identifying GEF/GAP regulators\",\n      \"pmids\": [\"15642749\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Secramine inhibits CDC42 activation by a mechanism dependent on RhoGDI: it inhibits CDC42 membrane binding, GTP loading, and effector binding in a RhoGDI-dependent manner in vitro, and mimics dominant-negative CDC42 effects on Golgi protein export and polarization in cells.\",\n      \"method\": \"In vitro GTP-binding assay, membrane binding assay, effector binding assay with and without RhoGDI, RhoGDI-dependence experiments, cell-based Golgi traffic assay\",\n      \"journal\": \"Nature chemical biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mechanistic in vitro reconstitution showing RhoGDI-dependence of inhibition, validated by cellular phenocopy of dominant-negative CDC42; single rigorous study\",\n      \"pmids\": [\"16408091\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"CDC42 and Rac1 drive endothelial lumen formation in 3D collagen matrices through downstream effectors Pak2, Pak4, Par3, Par6, and PKCε/ζ; RNAi knockdown of Pak2 or Pak4 markedly inhibits lumen formation, and disruption of the Cdc42–Par3–Par6–PKCζ polarity complex impairs lumenogenesis.\",\n      \"method\": \"RNAi knockdown, dominant-negative expression, 3D collagen matrix lumenogenesis assay, Pak phosphorylation assays\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — RNAi knockdown of multiple pathway components, dominant-negative epistasis, defined 3D morphogenesis assay; systematic dissection of the signaling complex\",\n      \"pmids\": [\"18319301\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"CDC42 is essential for pancreatic tubulogenesis specifically for initiating microlumen formation and maintaining apical cell polarity; Cdc42 controls cell specification non-cell-autonomously by providing a correct microenvironment for multipotent progenitor fate choices.\",\n      \"method\": \"Conditional knockout in pancreatic lineage (mouse), histology, immunofluorescence of polarity markers, lineage tracing\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — tissue-specific conditional knockout with clear morphogenetic phenotype and mechanistic non-cell-autonomous finding; in vivo genetic approach\",\n      \"pmids\": [\"19914171\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"During directed cell migration, CDC42 (with its exchange factor βPIX) localizes to intracytoplasmic vesicles and is recruited to the leading edge via Arf6-dependent membrane trafficking; inhibiting Arf6-dependent traffic abolishes polarized CDC42 and βPIX recruitment, Par6-aPKC complex polarization, and directed migration.\",\n      \"method\": \"Live-cell imaging of GFP-Cdc42-positive vesicles, Arf6 inhibition, immunofluorescence, cell polarization assay\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — live imaging of CDC42 vesicular trafficking, epistasis linking Arf6-dependent traffic to CDC42 polarity, multiple readouts; single rigorous study\",\n      \"pmids\": [\"21173111\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CDC42 regulates microtubule-dependent Golgi positioning; ARHGAP21 (Cdc42-specific GAP) knockdown inhibits Golgi repositioning to the centrosome; disrupting Cdc42 activation or the coatomer/Cdc42 binding interaction stimulates dynein-dependent Golgi motility, placing Cdc42 downstream of ARF1 and coatomer in regulating Golgi capture.\",\n      \"method\": \"siRNA knockdown of ARHGAP21, nocodazole washout Golgi repositioning assay, Golgi capture and motility assay in permeabilized cells, dynein inhibitory antibody\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA and permeabilized-cell motility assay with antibody inhibition; single lab, multiple methods\",\n      \"pmids\": [\"20525016\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Missense variants in CDC42 variably perturb its switch between active/inactive states and/or its interaction with effectors, causing a clinically heterogeneous group of developmental disorders; in vitro functional assays confirmed altered GTPase activity and effector binding for specific mutants.\",\n      \"method\": \"Exome sequencing, in silico analysis, in vitro GTPase activity assay, effector-binding assays, in vivo zebrafish/animal models\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro biochemical characterization of multiple mutants with direct GTPase and effector binding assays; complemented by in vivo animal models\",\n      \"pmids\": [\"29394990\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"CDC42 is required for primary ciliogenesis: CDC42 co-localizes with the exocyst component Sec10 at primary cilia, interacts with Sec10, and its knockout in kidney tubular epithelial cells causes ciliogenesis defects, cystogenesis, and MAPK activation; zebrafish cdc42 and sec10 show synergistic genetic interaction in the same pathway.\",\n      \"method\": \"Morpholino knockdown in zebrafish (genetic interaction), conditional knockout in mouse kidney, immunofluorescence (co-localization), co-IP (Sec10 interaction), MAPK assay\",\n      \"journal\": \"Journal of the American Society of Nephrology : JASN\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — tissue-specific conditional KO phenotype plus zebrafish genetic epistasis plus co-IP; multiple orthogonal methods across two model organisms\",\n      \"pmids\": [\"23766535\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"CDC42 conditional knockout in the nephrogenic lineage phenocopies Yap loss; ablation of CDC42 decreases nuclear localization of YAP and reduces YAP-dependent gene expression, placing CDC42 upstream of YAP nuclear translocation in nephron progenitor cells.\",\n      \"method\": \"Conditional knockout (mouse), microarray, immunofluorescence of YAP localization, gene expression analysis\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with direct YAP localization measurement and gene expression readout; epistasis by genetic phenocopy, single lab\",\n      \"pmids\": [\"23555292\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"A novel allosteric CDC42-selective inhibitor (identified by HTS) acts as a noncompetitive inhibitor with no activity toward Rho or Rac; it inhibits CDC42-related filopodia formation and cell migration in cells, demonstrating that allosteric inhibition of nucleotide binding is feasible for selectively targeting CDC42.\",\n      \"method\": \"High-throughput screening, GTPase biochemical assay, structure-activity relationship, filopodia formation assay, cell migration assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic characterization plus cellular validation; allosteric mechanism established biochemically\",\n      \"pmids\": [\"23382385\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Active CDC42 is both necessary and sufficient to form invadosome actin cores in multiple cell types; combined with Tks5 expression, CDC42-driven actin cores acquire proteolytic activity, defining a minimal molecular signature of invadosomes.\",\n      \"method\": \"Overexpression of constitutively active Cdc42, Tks5 co-expression, immunofluorescence, gelatin degradation assay\",\n      \"journal\": \"Cell adhesion & migration\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — overexpression gain-of-function across multiple cell lines with functional proteolytic assay; single lab\",\n      \"pmids\": [\"24840388\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"During chemotaxis, local CDC42 signals (but not Rac, RhoA, or Ras signals) precede and predict cell turning; CDC42 has excitable properties (recurring local activity pulses revealed upon actin inhibition) and antagonizes RhoA, maintaining a steep spatial activity gradient that directs chemotactic steering.\",\n      \"method\": \"Fluorescence biosensors (FRET/FLIM) in neutrophil-like PLB-985 cells, photorelease of chemoattractant, actin polymerization inhibition, GTPase activity imaging\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — live biosensor imaging with spatiotemporal resolution, chemoattractant photorelease, and actin inhibition epistasis; multiple GTPases compared with multiple biosensors\",\n      \"pmids\": [\"26689677\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"CDC42 activity is required for optogenetically induced cell turning; the shape of the Cdc42 gradient is set by the spatial distribution of GEFs, not by transport, with a steep Cdc42 gradient maximizing directionality; a GAP (β2-chimaerin, localized at the cell tip by Cdc42 and Rac1 feedbacks) shapes the Rac1 gradient.\",\n      \"method\": \"Optogenetics (photoactivatable Rac1/Cdc42), micropatterned GEF substrates, FRET biosensors, live-cell imaging\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — optogenetic gain-of-function with biosensor readout, multiple GTPase conditions, mechanistic dissection of gradient-shaping by GEF/GAP spatial distribution\",\n      \"pmids\": [\"30446664\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Cytoplasmic YAP positively regulates CDC42 activity in endothelial cells; CDC42 deletion causes severe defects in endothelial cell migration during retinal angiogenesis, and overexpression of cytoplasmic YAP (YAPS127D) partially rescues Yap/Taz-deficient migration defects through CDC42.\",\n      \"method\": \"Conditional knockout (endothelial-specific Yap/Taz and Cdc42), rescue with YAPS127D, retinal angiogenesis assay, GTPase activity assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with conditional KO and rescue, direct CDC42 activity measurement; single lab\",\n      \"pmids\": [\"28973878\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CDC42 binds PAK4 through an extended interface beyond the canonical CRIB domain, including additional contacts between the PAK4 kinase C-lobe, CDC42, and the PAK4 polybasic region; these additional contacts modulate kinase activity and increase CDC42 binding affinity compared to CRIB domain alone.\",\n      \"method\": \"X-ray crystallography, solution scattering (SAXS), kinase activity assay, binding affinity measurement\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure plus SAXS for full-length complex, kinase activity assay with defined mechanistic consequence; rigorous multi-method study\",\n      \"pmids\": [\"29295922\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Endothelial-specific deletion of CDC42 elicits cerebrovascular malformations resembling cerebral cavernous malformations (CCM) by increasing MEKK3-MEK5-ERK5 signaling and overexpression of KLF2 and KLF4; co-inactivation of Klf4 reduces malformation severity; CDC42 interacts with CCM proteins, and CCM3 promotes CDC42 activity in endothelial cells.\",\n      \"method\": \"Inducible endothelial-specific conditional knockout (mouse), retinal angiogenesis assay, signaling pathway analysis (western blot), genetic rescue (Klf4 co-KO), co-immunoprecipitation (CCM3–CDC42)\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo conditional KO, genetic epistasis rescue, co-IP for complex identification, signaling pathway analysis; multiple orthogonal methods\",\n      \"pmids\": [\"30732528\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Activated GTP-bound CDC42 and its effector IQGAP1 are required for tumor microvesicle (MV) shedding; activated CDC42 also prevents EGFR internalization to maintain sustained EGF signaling that facilitates MV release, and blocking CDC42 signaling reduces MV-promoted tumor angiogenesis in vivo.\",\n      \"method\": \"Co-immunoprecipitation (CDC42–IQGAP1), dominant-negative and constitutively active mutants, MV shedding assay, EGFR internalization assay, in vivo tumor angiogenesis assay\",\n      \"journal\": \"Journal of extracellular vesicles\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, functional mutant analysis, and in vivo validation; single lab\",\n      \"pmids\": [\"33473262\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The microprotein pTINCR binds to CDC42 and promotes CDC42 SUMOylation and activation, triggering a pro-differentiation cascade in epithelial cells; this places pTINCR as a positive upstream regulator of CDC42 activity via a SUMO-dependent mechanism.\",\n      \"method\": \"Co-immunoprecipitation (pTINCR–CDC42), SUMOylation assay, gain- and loss-of-function studies, in vitro differentiation assay, patient-derived xenograft\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, SUMOylation assay, in vivo xenograft; novel mechanism but single lab\",\n      \"pmids\": [\"36369429\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"mTORC2 phosphorylates NDRG1 at Ser336 during fasting, and phosphorylated NDRG1 cooperates with CDC42 and its effectors/regulators to orchestrate mitochondrial fission; Cdc42-deficient cells display fission failure phenotypes similar to NDRG1-Ser336Ala mutants and RictorKO cells.\",\n      \"method\": \"Time-lapse imaging, siRNA screen, epistasis experiments, proteomics, Cdc42-deficient cells (genetic), phosphorylation-deficient mutants\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with multiple pathway components, live imaging of mitochondrial fission, proteomic identification; single lab\",\n      \"pmids\": [\"37386153\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CDC42 is a Rho-family GTPase molecular switch that, when GTP-bound (activated by GEFs such as Dbl, βPIX, Ect2; inhibited by GAPs; sequestered in cytosol by RhoGDI via the Rho insert region; and membrane-anchored via C-terminal prenylation/carboxyl methylation), engages a spectrum of effectors—including PAK1/2/4, MRCK-α, IQGAP1, WASP/N-WASP–Arp2/3, Par6–aPKC, and CLIP-170 via IQGAP1—to drive actin polymerization, filopodia/invadosome formation, cell polarity establishment, phagocytosis, vesicle trafficking (including Golgi positioning and microvesicle shedding), mitosis (kinetochore–microtubule attachment via Ect2/MgcRacGAP regulation), mitochondrial fission (via NDRG1 downstream of mTORC2), and chemotactic steering through locally excitable, spatially steep GTPase activity gradients that antagonize RhoA.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CDC42 is a Rho-family GTP-binding protein and conserved molecular switch that cycles between membrane-associated active and cytosolic inactive states to govern actin-based morphogenesis, cell polarity, and intracellular trafficking [#0, #6]. Its functional homology to yeast CDC42 was established by complementation, and its localization is controlled by C-terminal CAAX isoprenylation and GTP-stimulated carboxyl methylation that partition it between membranes and cytosol [#0, #1, #4]. The switch is regulated by a GAP that stimulates GTP hydrolysis on wild-type but not Val-12 CDC42 [#2], by GEFs including Dbl, Ect2 and \\u03b2PIX [#3, #29, #33], and by RhoGDI, which binds prenylated CDC42 with high affinity through the Rho insert region to inhibit GDP dissociation and extract it from membranes, enabling cytosol\\u2013membrane cycling without being required for membrane targeting itself [#3, #11, #12, #22]. In the GTP-bound state CDC42 engages a spectrum of effectors to drive distinct outputs: it triggers filopodia and peripheral actin microspikes [#6], activates the serine kinases PAK and the CDC42-selective PAK4 and MRCK-\\u03b1 to control actin-myosin contractility and substrate phosphorylation [#7, #15, #16, #43], and recruits WASp\\u2013Arp2/3 to build actin-rich phagocytic cups and invadosome cores [#23, #39]. Through IQGAP1 it integrates Ca2+/calmodulin signaling, sustains its own GTP-loaded state, and links to CLIP-170 to capture microtubules and establish polarized arrays [#9, #19, #25, #26]. CDC42 establishes and maintains cell polarity via the Par6\\u2013aPKC complex and Arf6-dependent vesicular delivery to the leading edge, directing chemotactic steering through locally excitable GTPase gradients that antagonize RhoA and are shaped by the spatial distribution of GEFs [#31, #33, #40, #41, #28]. Beyond migration, CDC42 functions in epithelial and endothelial tubulogenesis and lumen formation, primary ciliogenesis via the exocyst component Sec10, mitotic kinetochore\\u2013microtubule attachment through Ect2/MgcRacGAP, Golgi positioning, and mTORC2/NDRG1-coupled mitochondrial fission [#31, #32, #36, #29, #34, #47]. Missense variants that perturb the active/inactive switch or effector binding cause a clinically heterogeneous group of developmental disorders [#35].\",\n  \"teleology\": [\n    {\n      \"year\": 1990,\n      \"claim\": \"Established that the human G25K protein is a bona fide GTP-binding ortholog of yeast CDC42, defining it as a conserved molecular switch whose membrane association is set by lipid modification.\",\n      \"evidence\": \"cDNA cloning with yeast complementation and GTP-binding assays; metabolic [3H]mevalonate labeling with lovastatin inhibition and fractionation\",\n      \"pmids\": [\"2122236\", \"2124704\", \"2120220\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify downstream effectors\", \"Did not define which cellular processes the switch controls in human cells\"]\n    },\n    {\n      \"year\": 1992,\n      \"claim\": \"Defined the regulatory inputs to the switch by purifying a CDC42-specific GAP and showing RhoGDI inhibits GDP dissociation and extracts CDC42 from membranes, framing the GEF/GAP/GDI control logic.\",\n      \"evidence\": \"Protein purification of platelet GAP with mutant specificity controls; GDP dissociation, membrane extraction, and carboxyl methylation assays with purified RhoGDI\",\n      \"pmids\": [\"1939135\", \"1429634\", \"1526984\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"GAP identity at the gene level not resolved here\", \"Structural basis of GDI binding not yet defined\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Connected active CDC42 to its cellular output, showing it drives filopodia formation and directly activates the PAK serine kinase in a GTP-dependent manner, establishing the GTPase-to-actin signaling axis.\",\n      \"evidence\": \"Microinjection of constitutively active and dominant-negative CDC42 with phalloidin imaging; purified PAK GTP-dependent binding and autophosphorylation/kinase assays\",\n      \"pmids\": [\"7891688\", \"7744004\", \"8034624\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How PAK activation links to actin remodeling not fully traced\", \"Did not establish the full effector repertoire\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Identified IQGAP1/2 as effectors that bind GTP-CDC42 and inhibit its GTPase activity, and mapped the Rho insert region as the GDI-interaction determinant separable from effector binding, refining switch-state regulation.\",\n      \"evidence\": \"Affinity purification, reciprocal co-IP, GTPase assays, immunofluorescence; Cdc42/Ras chimera domain-swap mutagenesis; fluorescence-spectroscopy Kd determination\",\n      \"pmids\": [\"8670801\", \"8702968\", \"9334181\", \"8626553\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of IQGAP inhibition of GTP hydrolysis in cells unresolved\", \"Insert-region role distinct from membrane targeting not yet tested\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Expanded the effector network to CDC42-specific kinases and the actin nucleation machinery, defining how CDC42 produces distinct cytoskeletal and contractile outputs and drives phagocytosis.\",\n      \"evidence\": \"Co-IP and localization of PAK4 with kinase-dead/binding mutants; MRCK-\\u03b1 in vitro kinase assay on myosin light chain; dominant-negative CDC42 in FcgammaR phagocytosis with distinct morphological phenotypes\",\n      \"pmids\": [\"9822598\", \"9418861\", \"9799231\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Spatial coordination of multiple effectors in one cell not resolved\", \"Substrate specificity of MRCK-\\u03b1 versus PAK4 in vivo unclear\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Demonstrated RhoGDI-dependent cytosol\\u2013membrane cycling and PAK-mediated phosphorylation of merlin, and tied CDC42-WASp-Arp2/3 to phagocytic cup actin assembly, mechanistically linking the switch to traffic, growth control, and engulfment.\",\n      \"evidence\": \"R66E GDI-binding-deficient mutant with fractionation/imaging; in vitro and in vivo PAK kinase assay on merlin Ser518; dominant-negative CDC42, WASp-KO, and Arp2/3 inhibition in phagocytosis\",\n      \"pmids\": [\"11583574\", \"11719502\", \"11580754\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"GDI cycling kinetics in living cells not measured\", \"How GDI release is triggered physiologically not defined\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Established CDC42 as a polarity organizer linking actin to microtubules via the IQGAP1\\u2013CLIP-170 tripartite complex, and showed IQGAP1 sustains the GTP-bound state, connecting effector binding to gradient maintenance.\",\n      \"evidence\": \"Co-IP of tripartite complex, GFP-CLIP-170 imaging, dominant-negative IQGAP1; IQGAP1 \\u0394GRD mutant with GTP-Cdc42 pulldown and filopodia readouts\",\n      \"pmids\": [\"12110184\", \"11948177\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How microtubule capture feeds back on CDC42 activity not resolved\", \"Quantitative contribution of IQGAP1 to gradient steepness unknown\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Visualized spatially patterned active-CDC42 zones and identified the mitotic Ect2/MgcRacGAP GEF/GAP pair, establishing that CDC42 functions through spatially confined activity and operates in mitosis as well as cortical remodeling.\",\n      \"evidence\": \"Active-GTPase biosensor imaging in wounded Xenopus oocytes with cytoskeletal/Ca2+ perturbation; RNAi and dominant-negative epistasis with GTP-Cdc42 pulldown and kinetochore imaging\",\n      \"pmids\": [\"15684032\", \"15642749\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of zone segregation from RhoA not defined\", \"How mitotic GEF/GAP cycling is timed unresolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Showed that polarized CDC42 activity during migration is established by Arf6-dependent vesicular delivery of CDC42/\\u03b2PIX to the leading edge and that CDC42 controls microtubule-dependent Golgi positioning, coupling the switch to membrane trafficking.\",\n      \"evidence\": \"Live imaging of GFP-Cdc42 vesicles with Arf6 inhibition and polarity readouts; ARHGAP21 siRNA with Golgi repositioning and permeabilized-cell motility assays\",\n      \"pmids\": [\"21173111\", \"20525016\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How Arf6 traffic is spatially restricted not defined\", \"Direct coatomer\\u2013CDC42 interaction at gene level not fully resolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined in vivo developmental and disease roles\\u2014tubulogenesis, ciliogenesis via Sec10, YAP regulation\\u2014and linked germline CDC42 missense variants perturbing the switch to human developmental disorders.\",\n      \"evidence\": \"Tissue-specific conditional knockouts (pancreas, kidney) with polarity/YAP readouts; zebrafish cdc42/sec10 epistasis and co-IP; exome sequencing with in vitro GTPase/effector assays and animal models\",\n      \"pmids\": [\"19914171\", \"23766535\", \"23555292\", \"29394990\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genotype-phenotype rules for variant classes incomplete\", \"Tissue-specific effector usage not fully mapped\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Resolved the structural basis of effector engagement, showing CDC42 binds PAK4 through an extended interface beyond the CRIB domain that modulates kinase activity and binding affinity.\",\n      \"evidence\": \"X-ray crystallography and SAXS of the full-length complex with kinase activity and affinity measurements\",\n      \"pmids\": [\"29295922\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether other effectors use analogous extended interfaces unknown\", \"In-cell relevance of the extended contacts not tested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Established CDC42 as a vascular morphogenesis regulator whose loss causes cavernous-malformation-like lesions via MEKK3-ERK5-KLF2/4 signaling, and identified CCM3 as a promoter of CDC42 activity.\",\n      \"evidence\": \"Inducible endothelial conditional knockout, retinal angiogenesis, signaling/western analysis, Klf4 co-KO rescue, CCM3\\u2013CDC42 co-IP\",\n      \"pmids\": [\"30732528\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which CCM3 activates CDC42 not defined\", \"How CDC42 loss elevates MEKK3 signaling not fully traced\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Extended CDC42 function to organelle dynamics and identified novel upstream activators, implicating it in mTORC2/NDRG1-driven mitochondrial fission and in pTINCR/SUMO-dependent activation, and in tumor microvesicle shedding.\",\n      \"evidence\": \"Genetic epistasis, siRNA screens, proteomics and live imaging in Cdc42-deficient cells; co-IP and SUMOylation assays; MV shedding and EGFR internalization assays with mutants\",\n      \"pmids\": [\"37386153\", \"36369429\", \"33473262\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct CDC42 effectors in mitochondrial fission not identified\", \"These single-lab mechanisms await independent confirmation\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the same CDC42 switch is allosterically partitioned in real time among its many effectors to specify distinct outputs (filopodia, polarity, mitosis, fission) within one cell remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model linking spatial GTP-loading to effector selection\", \"Quantitative effector competition in vivo not measured\", \"Endogenous determinants of GDI release versus effector engagement undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003924\", \"supporting_discovery_ids\": [0, 2, 26, 35]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [6, 40, 41]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [7, 15, 16]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 6, 8, 22]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [1, 22, 33]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [15, 22, 34]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [33]},\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [36]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [6, 7, 40, 41]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [31, 32, 36, 35]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [13, 29]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [33, 34, 45]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [17, 23]}\n    ],\n    \"complexes\": [\n      \"CDC42\\u2013RhoGDI heterodimer\",\n      \"IQGAP1\\u2013CLIP-170 tripartite complex\",\n      \"Par6\\u2013aPKC polarity complex\",\n      \"WASp\\u2013Arp2/3\"\n    ],\n    \"partners\": [\n      \"RhoGDI\",\n      \"IQGAP1\",\n      \"PAK4\",\n      \"MRCK-\\u03b1\",\n      \"WASp\",\n      \"Ect2\",\n      \"Sec10\",\n      \"CCM3\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}