{"gene":"PAK3","run_date":"2026-06-10T05:19:53","timeline":{"discoveries":[{"year":1998,"finding":"PAK3 is a serine-threonine kinase that functions as a downstream effector linking Rho GTPases (Rac/Cdc42) to cytoskeletal reorganization and nuclear signalling; a nonsense mutation causing premature termination disrupts kinase function and causes X-linked mental retardation (MRX30).","method":"Point mutation identification in human pedigree; immunofluorescence showing PAK3 highly expressed in postmitotic neurons of developing/postnatal cerebral cortex and hippocampus","journal":"Nature genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — human genetics plus immunofluorescence localization in a single study; kinase disruption mechanistically inferred from truncation","pmids":["9731525"],"is_preprint":false},{"year":1998,"finding":"PAK3 phosphorylates Raf-1 on serine 338 both in vitro and in vivo, positively regulating Raf-1 activity; this places PAK3 at the intersection of Rac/Cdc42 signalling and the Ras-Raf-MAPK pathway.","method":"In vitro kinase assay with recombinant PAK3 and Raf-1; in vivo phosphorylation confirmed in cells; phospho-specific analysis","journal":"Nature","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay plus in vivo confirmation, but later challenged by a contradicting study (PMID:11259591)","pmids":["9823899"],"is_preprint":false},{"year":2001,"finding":"PAK3-mediated phosphorylation of Raf-1 S338 occurs in the cytosol and does not stimulate Raf-1 kinase activity; growth factor-stimulated Raf-1 S338 phosphorylation is independent of PI3-K and PAK3, arguing against PAK3 being a physiological mediator of S338 phosphorylation in growth factor-stimulated cells.","method":"Phospho-specific antibody to S338; PI3-K inhibitors (LY294002, wortmannin); constitutively active Cdc42 and activating PAK3 mutants; Raf-1 kinase activity assay","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — multiple pharmacological and genetic tools, in vitro and cellular assays; directly contradicts PMID:9823899 for the physiological context","pmids":["11259591"],"is_preprint":false},{"year":1997,"finding":"PAK3 can activate MEKK1 in vivo, but this is indirect; PAK3 does not directly phosphorylate MEKK1 in vitro.","method":"In vitro kinase assay (no direct phosphorylation detected); in vivo co-expression activation assay in COS cells; site-directed mutagenesis of MEKK1 threonines","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro assay with mutagenesis clearly established negative result (no direct phosphorylation) and positive in vivo indirect activation; single lab","pmids":["9065412"],"is_preprint":false},{"year":2000,"finding":"PAK3 directly binds paxillin alpha and beta isoforms (but not gamma); paxillin alpha associates with both kinase-inactive and Cdc42-activated PAK3 without affecting kinase activation state; paxillin alpha competes with Nck and betaPIX for PAK3 binding; PAK3 phosphorylates paxillin alpha on serine.","method":"Co-immunoprecipitation; direct binding assays with focal adhesion proteins; in vitro kinase assay showing PAK3 phosphorylates paxillin alpha","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP and in vitro kinase assay, single lab, multiple orthogonal methods","pmids":["11096073"],"is_preprint":false},{"year":2000,"finding":"Missense mutation R67C in the conserved polybasic domain (AA 66-68) of PAK3, predicted to affect GTPase binding and stimulation of PAK activity, causes X-linked nonsyndromic mental retardation (MRX47).","method":"DGGE and direct sequencing in MRX pedigree; mutation location in GTPase-binding domain inferred from conservation","journal":"American journal of medical genetics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — genetic identification of mutation in functionally relevant domain; no direct biochemical assay of GTPase binding performed in this paper","pmids":["10946356"],"is_preprint":false},{"year":2002,"finding":"A brain-specific PAK3 splice variant, PAK3b, contains a 15-amino acid insert within the autoinhibitory domain that renders the kinase constitutively active by preventing autoinhibition; PAK3b cannot bind Rac or Cdc42 GTPases, distinguishing its regulation from PAK3a.","method":"Cloning of alternatively spliced isoform; in vitro kinase assay comparing PAK3a and PAK3b; GTPase binding assays; autoinhibitory domain functional analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay plus GTPase binding assay with mutagenesis logic, multiple orthogonal methods in single rigorous study","pmids":["12464619"],"is_preprint":false},{"year":2003,"finding":"PAK3 physically interacts with the amyloid precursor protein (APP) and mediates FAD mutant APP-induced neuronal apoptosis and DNA synthesis; dominant-negative PAK3 inhibits these effects, and deletion of the PAK3 APP-binding domain abolishes the protective effect; FAD APP-induced signalling also requires G-protein Go upstream of PAK3.","method":"Dominant-negative PAK3 expression in primary neurons; APP-binding domain deletion constructs; pertussis toxin inhibition; Go rescue experiments; apoptosis and DNA synthesis assays","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple loss-of-function constructs and domain deletions in primary neurons; single lab","pmids":["12890786"],"is_preprint":false},{"year":2004,"finding":"PAK3 is required for normal dendritic spine morphogenesis and synapse formation in hippocampus; antisense/siRNA suppression or dominant-negative PAK3 (MRX30 mutation) causes elongated spines/filopodia, reduced mature synapses lacking PSDs, reduced AMPA receptor expression, and defective LTP.","method":"Antisense and siRNA knockdown; dominant-negative PAK3 expression in hippocampal organotypic slice cultures; ultrastructural analysis; electrophysiology (LTP, spontaneous activity); AMPA receptor immunostaining","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (siRNA, dominant-negative, ultrastructure, electrophysiology) in hippocampal cultures; replicated by subsequent studies","pmids":["15574732"],"is_preprint":false},{"year":2005,"finding":"PAK3 knockout mice exhibit deficient hippocampal late-phase LTP and impaired learning/memory; a dramatic reduction in active CREB (phospho-CREB) in knockout mice implicates PAK3-Rho signalling in regulating CREB-dependent synaptic plasticity.","method":"PAK3 knockout mouse; hippocampal LTP electrophysiology; behavioral learning/memory tests; phospho-CREB immunoblotting","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined LTP phenotype plus biochemical readout (phospho-CREB), multiple methods; replicated in concept by other KO studies","pmids":["16014725"],"is_preprint":false},{"year":2006,"finding":"ARHGEF6 (a Rac1/Cdc42 GEF) acts upstream of PAK3 in hippocampal spine morphogenesis; ARHGEF6 knockdown phenocopies PAK3 knockdown (elongated spines), and this is rescued by constitutively active PAK3 but not wild-type PAK3, placing PAK3 downstream of ARHGEF6 in this pathway.","method":"siRNA knockdown of ARHGEF6 and PAK3 in hippocampal slice cultures; rescue with constitutively active PAK3; co-localization with PSD95","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis via siRNA rescue experiment, single lab, two orthogonal approaches","pmids":["17105769"],"is_preprint":false},{"year":2008,"finding":"PAK3 loss-of-function and gain-of-function experiments show PAK3 and PAK1 have distinct roles in spine morphogenesis: PAK3 knockdown increases thin elongated immature spines, while PAK1 knockdown has no effect; constitutively active PAK1 can rescue the PAK3 knockdown phenotype, indicating functional overlap allowing compensation.","method":"siRNA knockdown of PAK3 and PAK1; constitutively active PAK1 and PAK3 expression; hippocampal slice cultures; spine morphology analysis","journal":"Hippocampus","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss and gain of function with epistasis rescue, single lab","pmids":["18481281"],"is_preprint":false},{"year":2010,"finding":"PAK3 phosphorylates cardiac troponin I (cTnI) at Ser151; pseudo-phosphorylation (S151E) increases myofilament Ca2+ sensitivity by shortening intersite distances between cTnC and cTnI and reducing Ca2+ dissociation-induced kinetic rates in reconstituted thin filaments.","method":"Reconstituted thin filament FRET (steady-state and time-resolved); stopped-flow kinetics; pseudo-phosphorylation mutant cTnI(S151E)","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with multiple biophysical methods (FRET, stopped-flow kinetics) and phospho-mimetic mutagenesis","pmids":["20540949"],"is_preprint":false},{"year":2011,"finding":"PAK3 preferentially interacts with Nck2/Grb4 adaptor (over Nck1) in brain and transfected cells; this interaction is independent of PAK3 kinase activity; disrupting the PAK3-Nck2 interaction with an interfering peptide increases evoked synaptic transmission; P12A mutation in PAK3 reduces Nck2 binding and eliminates PAK3's ability to decrease miniature excitatory current amplitude.","method":"Co-immunoprecipitation from brain extracts; interfering peptide in acute cortical slices; electrophysiology (evoked transmission, mEPSCs); P12A PAK3 mutant expression in hippocampal cultures","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, interfering peptide, mutant rescue; single lab, multiple methods","pmids":["21949127"],"is_preprint":false},{"year":2012,"finding":"PAK3 forms heterodimers with PAK1 in brain; PAK1 inhibits PAK3a activity in trans (but not PAK3b splice variant); two intellectual disability mutations impair PAK3 dimerization with PAK1; PAK1 and PAK3 co-localize in dendritic spines and co-purify with post-synaptic densities.","method":"Co-immunoprecipitation from brain lysates; co-purification with PSDs; in vitro kinase assay (trans-regulation); subcellular fractionation; confocal co-localization","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — Co-IP, kinase assay, subcellular fractionation and localization with functional consequence; multiple orthogonal methods in single rigorous study","pmids":["22815483"],"is_preprint":false},{"year":2012,"finding":"PAK3 is specifically recruited by synaptic activity from dendrites into spines; inhibition of PAK3 increases formation of unstable new spines (activity-dependent, clustered) and impairs plasticity-mediated spine stabilization, demonstrating a role in activity-mediated synaptic connectivity remodeling.","method":"Time-lapse imaging of spine dynamics in hippocampal slice cultures; PAK3 mutant expression; activity manipulation; fluorescence tracking of PAK3 translocation","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — live imaging with functional consequence, loss-of-function; single lab","pmids":["22238087"],"is_preprint":false},{"year":2013,"finding":"PAK3 acts downstream of Neurogenin3 to promote cell cycle exit and differentiation of beta-cells in the embryonic pancreas; PAK3 deficiency increases proliferation of Ngn3+ progenitors concomitantly with upregulation of Ccnd1, suggesting PAK3 represses Ccnd1 to promote cycle exit.","method":"Pak3 knockout mouse; pancreas development analysis; Ngn3+ progenitor proliferation assays; Ccnd1 expression analysis; glucose tolerance testing in adults","journal":"Diabetes","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO with defined cellular phenotype and molecular correlate (Ccnd1 upregulation); single lab","pmids":["24163148"],"is_preprint":false},{"year":2013,"finding":"PAK3 is required for actin organization and cell migration associated with AP-1 (cJun)-mediated cellular transformation; AP-1 directly binds a Jun binding site in the PAK3 promoter to regulate PAK3 transcription.","method":"siRNA knockdown of PAK3; PAK3 promoter luciferase assay with site-directed mutagenesis; cell migration assays; actin staining","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — promoter binding confirmed by in vitro and in vivo ChIP, siRNA phenotype assay; single lab","pmids":["23818969"],"is_preprint":false},{"year":2014,"finding":"The PAK3 K389N mutation abolishes kinase activity (like other XLID mutations) but additionally confers dominant-negative function; the mutant protein escapes physiologic degradation and perturbs MAPK signalling through a kinase-independent mechanism, causing brain and craniofacial structural defects in zebrafish.","method":"In vitro kinase assay; zebrafish in vivo model; biochemical stability assays; MAPK signalling analysis","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay combined with in vivo zebrafish studies and biochemical analysis; single lab, multiple methods","pmids":["24556213"],"is_preprint":false},{"year":2014,"finding":"The PAK3 effector domain (PBD46) binds Cdc42Hs; upon binding, side-chain dynamics propagate away from the binding interface causing rigidification near the nucleotide-binding pocket (slowing GTP hydrolysis) and increased flexibility around the guanine ring (facilitating nucleotide exchange).","method":"NMR 15N backbone and 13C methyl relaxation measurements; order parameter analysis on activated GMPPCP·Cdc42Hs","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR structure-function study with rigorous relaxation analysis; single lab but highly detailed biophysical characterization","pmids":["25109462"],"is_preprint":false},{"year":2015,"finding":"PAK3 phosphorylates GluA1 AMPAR subunit at Ser863 in vitro; PAK3 loss and pharmacological PAK inhibition disrupt activity-dependent S863 phosphorylation in cortical neurons; EphB2-Cdc42-PAK3 signalling cascade controls GluA1 surface trafficking.","method":"In vitro kinase assay (PAK3 phosphorylates S863); PAK3 siRNA knockdown; pharmacological PAK inhibition; EphB2/Zizimin1 signalling pathway analysis in cortical neurons","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay plus siRNA and pharmacological loss-of-function in neurons; multiple orthogonal approaches in single study","pmids":["26013460"],"is_preprint":false},{"year":2015,"finding":"In Drosophila border cells, Pak3 functions downstream of guidance receptor signalling through Rac GTPase to regulate F-actin distribution, protrusion stability/directionality, and apical-basal polarity during collective migration; Pak3 genetically interacts with Scribble and regulates JNK signalling.","method":"Pak3 RNAi in border cells; time-lapse imaging; genetic interaction with Scribble and Jra (JNK pathway); F-actin staining; polarity marker localization","journal":"Development (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis, live imaging, multiple genetic interactions; Drosophila ortholog study consistent with mammalian PAK3 function","pmids":["26395489"],"is_preprint":false},{"year":2016,"finding":"GIT1 activates PAK3 in cells; SCZ-associated GIT1 variants (R283W, S601N) fail to activate PAK3 and MAPK signalling; GIT1-R283W also fails to stimulate PAK phosphorylation in hippocampal neurons, placing GIT1 upstream of PAK3 in a synaptic signalling pathway.","method":"Cell-based co-expression assays for PAK3 activation; MAPK activity assays; hippocampal neuron culture PAK phosphorylation assay; allelic series functional analysis","journal":"Molecular psychiatry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional cell-based assays in multiple alleles plus neuronal validation; single lab","pmids":["27457813"],"is_preprint":false},{"year":2016,"finding":"PAK3 is highly expressed in oligodendrocyte precursor cells (OPCs); Pak3 knockout impairs OPC differentiation into mature oligodendrocytes in the developing corpus callosum in a cell-autonomous manner, without affecting OPC proliferation or migration.","method":"Pak3 KO mouse; OPC culture in vitro; differentiation assays; white matter analysis; cell-autonomous rescue experiments","journal":"Neurobiology of disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO with defined cellular phenotype, in vitro and in vivo validation; single lab","pmids":["27940202"],"is_preprint":false},{"year":2019,"finding":"PAK3 mutations G424R and K389N (associated with severe ID and corpus callosum agenesis) abolish kinase activity, stabilize the protein, increase interaction with αPIX/ARHGEF6, disturb adhesion point dynamics and cell spreading, and severely impair cell migration; the milder A365E variant also abolishes kinase activity but does not affect these cellular processes, explaining differential severity.","method":"In vitro kinase assays; protein stability assays; co-immunoprecipitation with αPIX; cell spreading/adhesion dynamics assays; migration assays; comparison of three PAK3 mutations","journal":"Neurobiology of disease","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay plus Co-IP, cell biology assays comparing multiple mutations; single lab with multiple rigorous methods","pmids":["31843706"],"is_preprint":false},{"year":2020,"finding":"PAK3-R67C knock-in mice show impaired long-term spatial memory and pattern separation, and exhibit accelerated death of adult-born hippocampal neurons during the 18-28 day critical period; young newborn neurons fail to be recruited during memory tasks, show decreased KCC2b chloride co-transporter, and altered dendritic development.","method":"R67C knock-in mouse model; behavioral testing (spatial memory, pattern separation); adult hippocampal neurogenesis BrdU/DCX analysis; post-recall c-Fos activation; KCC2b immunostaining","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knock-in mouse with multiple behavioral and cellular readouts; single lab","pmids":["31943058"],"is_preprint":false},{"year":2021,"finding":"PAK3 mediates metastatic signal transduction via the PAK3-JNK-Jun pathway downstream of Smad4; Smad4 loss-of-function upregulates PAK3 by reducing Smad4-dependent transcription of miR-495 and miR-543, which directly target the PAK3 3'UTR.","method":"Conditional KrasG12D/p53/Smad4 knockout mouse model; PAK3-JNK-Jun pathway analysis; miRNA-PAK3 3'UTR luciferase assays; miRNA overexpression/inhibition","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo mouse model plus 3'UTR luciferase validation, pathway analysis; single lab","pmids":["34381046"],"is_preprint":false},{"year":2023,"finding":"PAK3 suppresses autophagy through hyper-activation of mTORC1; cardiac-specific PAK3 overexpression causes pathological remodelling, hypertrophy, fibrosis, and apoptosis; PAK3-provoked cardiac dysfunction is mitigated by autophagic inducers.","method":"Cardiac-specific PAK3 overexpression in mice; isoprenaline stimulation; mTORC1 activity assays; autophagy flux assays in cardiomyocytes; pharmacological autophagic induction rescue","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo overexpression model with biochemical mTORC1/autophagy readouts and pharmacological rescue; single lab","pmids":["37324527"],"is_preprint":false},{"year":2024,"finding":"PAK3 promotes nuclear expression of SREBP1c through activation of mTOR and S6K1 in cardiomyocytes, resulting in abnormal lipid gene expression, lipid accumulation, and oxidative stress; PAK3 knockdown attenuates fatty acid-induced lipotoxicity in cardiomyocytes; S6K1 or SREBP1c inhibition alleviates PAK3-triggered lipid overload.","method":"Cardiac-specific PAK3 overexpression mice; PAK3 knockdown in rat and human cardiomyocytes; mTOR/S6K1/SREBP1c pathway analysis; lipid accumulation assays; pharmacological inhibitors","journal":"Diabetes","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo and in vitro models with pathway inhibitors; single lab, multiple cellular methods","pmids":["39137120"],"is_preprint":false},{"year":2024,"finding":"PAK3 kinase activity promotes tangential-to-radial migration switch of cortical interneurons by shortening leading processes and inducing polarity changes; constitutively active PAK3 impairs processive tangential migration and causes accumulation in deep cortical layers; kinase-dead PAK3 promotes branched leading processes and maintains processive tangential migration.","method":"Constitutively active and kinase-dead PAK3 expression in embryonic cortical interneurons; pharmacological PAK3 inhibition; time-lapse imaging; process dynamics quantification","journal":"Molecular psychiatry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain/loss-of-function with live imaging, pharmacological confirmation; single lab","pmids":["38454080"],"is_preprint":false},{"year":2024,"finding":"Tgif1 acts as a transcriptional repressor of PAK3 in osteoblasts; Tgif1 deficiency increases PAK3 expression, impairing osteoblast spreading, adhesion to collagen type I, and migration; these cytoskeletal defects are PAK3-dependent.","method":"Tgif1 knockout osteoblasts; PAK3 expression analysis; PAK3 knockdown rescue; cell spreading/adhesion/migration assays; chromatin analysis of PAK3 promoter","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO with defined molecular mechanism and rescue experiment; single lab","pmids":["38661167"],"is_preprint":false},{"year":2000,"finding":"PAK3 is activated by thrombin signalling through PAR1 and G-protein-coupled receptor systems in a pertussis toxin-sensitive (Gi/Go-dependent) but PI3-K-independent manner; constitutively active PAK3 does not activate JNK, showing that thrombin-stimulated JNK activation occurs independently of PAK3.","method":"HA-tagged PAK3 kinase assay in transfected CCL39 cells; pertussis toxin and LY294002 inhibition; constitutively active PAK3 inducible expression; JNK activity assay","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — kinase assay with pharmacological dissection and inducible overexpression; single lab","pmids":["11025445"],"is_preprint":false},{"year":2025,"finding":"PAK3-R67C variant enhances interactions with PAK-interacting exchange factors (PIX) in vitro; expression of PAK3-R67C in COS7 cells alters focal adhesion distribution; Pak3-R67C knock-in mice exhibit reduced hippocampal synaptic efficacy and defects in LTP despite unaltered synapse structure.","method":"Biochemical interaction assays; focal adhesion imaging in COS7 cells; Pak3-R67C knock-in mouse electrophysiology; behavioral analysis","journal":"Neurobiology of disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knock-in mouse with electrophysiology plus in vitro biochemical assays; single lab","pmids":["41223971"],"is_preprint":false},{"year":2023,"finding":"Cranial irradiation downregulates PAK3 via upregulation of miR-206-3p targeting PAK3, disrupting the PAK3-LIMK1-cofilin actin turnover signalling pathway and the F/G-actin ratio; inhibition of miR-206-3p with antagomiR restores PAK3 signalling and cognitive function in irradiated mice.","method":"Cranial irradiation mouse model; PAK3-LIMK1-cofilin pathway analysis; antagomiR-206-3p intranasal administration; F/G-actin ratio measurement; behavioral testing","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo model with pharmacological rescue and signalling pathway analysis; single lab","pmids":["38131292"],"is_preprint":false},{"year":2026,"finding":"PAK3 phosphorylates SLC3A2 at Serine 175 in gemcitabine-resistant pancreatic cancer cells, enhancing SLC3A2 protein stability by preventing its recognition and ubiquitination by E3 ligase STUB1, thereby promoting ferroptosis resistance and gemcitabine resistance; PAK3 transcription is driven by FGF1-induced PAX6 from cancer-associated fibroblasts.","method":"Transcriptomic sequencing of resistant cells; PAK3 kinase assay on SLC3A2; ubiquitination assays with STUB1; PAX6 transcription analysis; CAF co-culture model","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — kinase assay identifying phosphorylation site plus ubiquitination assay; single lab, multiple orthogonal biochemical methods","pmids":["41786277"],"is_preprint":false}],"current_model":"PAK3 is a group I p21-activated serine/threonine kinase that is activated by GTP-bound Rac and Cdc42 (and by GPCR/Go signalling), and which regulates actin cytoskeletal dynamics, dendritic spine morphogenesis, and synaptic plasticity in neurons through multiple mechanisms: it dimerizes with PAK1 (subject to trans-inhibition), interacts with scaffold proteins (paxillin, Nck2/Grb4, αPIX/ARHGEF6), phosphorylates substrates including GluA1-S863 to regulate AMPAR trafficking, cardiac troponin I-S151 to increase myofilament Ca2+ sensitivity, and SLC3A2-S175 to enhance protein stability; it also controls mTORC1-dependent autophagy and SREBP1c-driven lipid metabolism in cardiomyocytes, promotes oligodendrocyte precursor differentiation and cortical interneuron radial migration, and loss-of-function mutations that abolish kinase activity cause X-linked intellectual disability by impairing spine formation, synaptic plasticity, and adult hippocampal neurogenesis."},"narrative":{"mechanistic_narrative":"PAK3 is a group I p21-activated serine/threonine kinase that links Rho-family GTPase signalling to actin cytoskeletal remodelling, neuronal connectivity, and synaptic plasticity [PMID:9731525, PMID:25109462]. Its effector domain binds GTP-loaded Cdc42, and binding propagates side-chain dynamics that rigidify the nucleotide pocket while loosening the guanine ring, coupling GTPase engagement to kinase activation [PMID:25109462]; a brain-specific splice variant (PAK3b) inserts 15 residues into the autoinhibitory domain to render the kinase constitutively active and GTPase-independent [PMID:12464619]. PAK3 is also activated through Gi/Go-coupled receptor signalling in a PI3K-independent manner [PMID:11025445] and by upstream scaffolds/GEFs including ARHGEF6/αPIX and GIT1, which feed into hippocampal spine morphogenesis and synaptic signalling [PMID:17105769, PMID:27457813, PMID:31843706]. In neurons, PAK3 is required for dendritic spine maturation and synapse formation, is recruited into spines by activity to stabilize new connections, and supports late-phase LTP and CREB-dependent plasticity [PMID:15574732, PMID:16014725, PMID:22238087]; it functions in part by heterodimerizing with PAK1, which trans-inhibits PAK3a but not PAK3b, and by associating with adaptor and scaffold proteins (Nck2/Grb4, paxillin) [PMID:11096073, PMID:21949127, PMID:22815483]. PAK3 phosphorylates defined substrates to execute these roles, including the AMPA receptor subunit GluA1 at Ser863 downstream of EphB2–Cdc42 to control receptor trafficking [PMID:26013460] and signalling through a PAK3–LIMK1–cofilin axis governing the F/G-actin ratio [PMID:38131292]. Loss-of-function mutations that abolish kinase activity cause X-linked intellectual disability by impairing spine formation, synaptic plasticity, and adult hippocampal neurogenesis, with severity modulated by gain of dominant-negative or aberrant scaffold-binding properties [PMID:9731525, PMID:24556213, PMID:31843706, PMID:31943058, PMID:41223971]. Beyond the nervous system, PAK3 controls actin organization and cell migration in multiple contexts and acts as a transcriptionally regulated node in cancer and cardiac disease: it phosphorylates cardiac troponin I at Ser151 to raise myofilament Ca2+ sensitivity [PMID:20540949], hyperactivates mTORC1 to suppress autophagy and drive SREBP1c-dependent lipotoxic cardiac remodelling [PMID:37324527, PMID:39137120], and phosphorylates SLC3A2 at Ser175 to block STUB1-mediated ubiquitination and confer ferroptosis and chemotherapy resistance [PMID:41786277].","teleology":[{"year":1998,"claim":"Established PAK3 as a neuronal Rho-GTPase effector kinase whose disruption causes human disease, defining the gene's clinical and signalling significance.","evidence":"Nonsense mutation in an X-linked mental retardation pedigree with PAK3 immunolocalization in postmitotic cortical and hippocampal neurons","pmids":["9731525"],"confidence":"Medium","gaps":["Kinase disruption inferred from truncation rather than directly assayed","No substrates identified in this study"]},{"year":1997,"claim":"Tested whether PAK3 couples to MAP kinase cascades, distinguishing direct from indirect activation.","evidence":"In vitro kinase assay (no direct MEKK1 phosphorylation) plus in vivo co-expression activation in COS cells","pmids":["9065412"],"confidence":"Medium","gaps":["Mechanism of indirect MEKK1 activation undefined","Physiological relevance not established"]},{"year":1998,"claim":"Proposed PAK3 as a Raf-1 S338 kinase placing it at the Rac/Cdc42–Ras-Raf-MAPK intersection, a claim later contested.","evidence":"In vitro and in vivo phospho-specific analysis of Raf-1 S338; subsequently challenged by pharmacological/genetic dissection showing PAK3-independent S338 phosphorylation","pmids":["9823899","11259591"],"confidence":"Medium","gaps":["Physiological contribution of PAK3 to Raf-1 S338 phosphorylation contradicted","Cellular context dependence unresolved"]},{"year":2000,"claim":"Defined PAK3 scaffold partners and upstream receptor inputs, situating PAK3 within focal-adhesion and GPCR signalling.","evidence":"Co-IP and in vitro kinase assays with paxillin alpha/beta; thrombin/PAR1 activation of PAK3 dissected with pertussis toxin and PI3K inhibitors","pmids":["11096073","11025445"],"confidence":"Medium","gaps":["Functional consequence of paxillin phosphorylation not defined","Single-lab observations"]},{"year":2000,"claim":"Linked a GTPase-binding-domain missense mutation (R67C) to nonsyndromic intellectual disability, implicating GTPase coupling in disease.","evidence":"Sequencing in an MRX pedigree; functional effect inferred from domain conservation","pmids":["10946356"],"confidence":"Low","gaps":["No biochemical assay of GTPase binding performed in this study","Functional effect remained inferred"]},{"year":2002,"claim":"Revealed splice-isoform control of PAK3 activation, showing a brain-specific variant escapes both autoinhibition and GTPase dependence.","evidence":"Cloning of PAK3b; comparative in vitro kinase and GTPase-binding assays with autoinhibitory-domain analysis","pmids":["12464619"],"confidence":"High","gaps":["In vivo functional role of PAK3b vs PAK3a not resolved","Tissue distribution of isoforms incompletely mapped"]},{"year":2003,"claim":"Connected PAK3 to APP-dependent neuronal death, implicating Go signalling upstream of PAK3 in a neurodegeneration context.","evidence":"Dominant-negative and APP-binding-domain deletion constructs, pertussis toxin and Go rescue in primary neurons","pmids":["12890786"],"confidence":"Medium","gaps":["Direct PAK3-APP binding interface not mapped biochemically","Relevance to sporadic Alzheimer disease unaddressed"]},{"year":2004,"claim":"Established PAK3 as essential for dendritic spine maturation, synapse formation, AMPA receptor expression, and LTP, defining its core neuronal function.","evidence":"Antisense/siRNA and dominant-negative PAK3 in hippocampal slices with ultrastructure, electrophysiology, and AMPAR immunostaining","pmids":["15574732"],"confidence":"High","gaps":["Substrates mediating spine effects not identified in this study","Mechanism linking kinase activity to spine shape unresolved"]},{"year":2005,"claim":"Showed PAK3 loss disrupts late-phase LTP and learning with reduced active CREB, connecting PAK3 to transcription-dependent plasticity.","evidence":"PAK3 knockout mice with hippocampal LTP, behavior, and phospho-CREB immunoblotting","pmids":["16014725"],"confidence":"High","gaps":["Mechanistic link from PAK3 to CREB phosphorylation undefined","Compensation by PAK1 not assessed here"]},{"year":2006,"claim":"Placed PAK3 epistatically downstream of the GEF ARHGEF6 in spine morphogenesis.","evidence":"siRNA of ARHGEF6 and PAK3 in hippocampal slices with constitutively active PAK3 rescue and PSD95 co-localization","pmids":["17105769"],"confidence":"Medium","gaps":["Direct GEF-to-GTPase-to-PAK3 step not biochemically reconstituted","Single lab"]},{"year":2008,"claim":"Distinguished PAK3 from PAK1 in spine morphogenesis while showing functional redundancy that permits compensation.","evidence":"siRNA knockdown and constitutively active rescue of PAK1/PAK3 in hippocampal slices","pmids":["18481281"],"confidence":"Medium","gaps":["Molecular basis of isoform-specific roles undefined","Endogenous compensation in vivo not measured"]},{"year":2010,"claim":"Identified cardiac troponin I Ser151 as a PAK3 substrate, extending PAK3 function to myofilament Ca2+ regulation.","evidence":"Reconstituted thin-filament FRET and stopped-flow kinetics with cTnI(S151E) phospho-mimetic","pmids":["20540949"],"confidence":"High","gaps":["In vivo cardiac role of cTnI S151 phosphorylation by PAK3 not established here","Endogenous PAK3 activity in cardiomyocytes not measured"]},{"year":2011,"claim":"Defined a kinase-independent PAK3-Nck2/Grb4 interaction that regulates synaptic transmission, distinguishing scaffold from catalytic functions.","evidence":"Brain Co-IP, interfering peptide in cortical slices, P12A mutant, and mEPSC/evoked transmission electrophysiology","pmids":["21949127"],"confidence":"Medium","gaps":["Downstream effectors of the Nck2 complex undefined","Single lab"]},{"year":2012,"claim":"Established PAK1–PAK3 heterodimerization with trans-inhibition and showed disease mutations impair dimerization, linking complex assembly to function.","evidence":"Brain Co-IP, PSD co-purification, subcellular fractionation, and in vitro trans-regulation kinase assays","pmids":["22815483"],"confidence":"High","gaps":["Stoichiometry and regulation of heterodimers in vivo unresolved","How PAK3b escapes trans-inhibition mechanistically partial"]},{"year":2012,"claim":"Showed activity-dependent recruitment of PAK3 into spines stabilizes new connections, framing PAK3 as a regulator of plasticity-driven remodelling.","evidence":"Time-lapse imaging of spine dynamics and PAK3 translocation with mutant expression in hippocampal slices","pmids":["22238087"],"confidence":"Medium","gaps":["Recruitment signal/anchor not identified","Single lab"]},{"year":2013,"claim":"Extended PAK3 function to cell-cycle exit/differentiation and to transcriptionally regulated migration and transformation.","evidence":"Pak3 knockout pancreas analysis (Ngn3/Ccnd1); siRNA migration assays and PAK3 promoter luciferase/ChIP for AP-1 (cJun)","pmids":["24163148","23818969"],"confidence":"Medium","gaps":["Direct PAK3 substrates in these contexts not defined","Tissue-specific generality untested"]},{"year":2014,"claim":"Resolved the structural basis of Cdc42-coupled PAK3 activation and demonstrated that some XLID mutations act through dominant-negative, kinase-independent mechanisms.","evidence":"NMR relaxation analysis of PBD46·Cdc42Hs; in vitro kinase, stability, and MAPK assays plus zebrafish modeling of K389N","pmids":["25109462","24556213"],"confidence":"High","gaps":["Full-length PAK3-Cdc42 dynamics not solved","Dominant-negative mechanism for MAPK perturbation incomplete"]},{"year":2015,"claim":"Identified GluA1 Ser863 as a PAK3 substrate in an EphB2-Cdc42-PAK3 cascade controlling AMPAR trafficking, and confirmed conserved migration roles via the Drosophila ortholog.","evidence":"In vitro kinase assay, siRNA and pharmacological PAK inhibition in cortical neurons; Drosophila border-cell RNAi, imaging, and genetic interactions","pmids":["26013460","26395489"],"confidence":"High","gaps":["In vivo significance of GluA1 S863 phosphorylation in plasticity not fully established","Cross-species conservation of substrate specificity untested"]},{"year":2016,"claim":"Placed GIT1 upstream of PAK3 with disease-associated alleles failing to activate it, and revealed a cell-type-specific role in oligodendrocyte differentiation.","evidence":"Cell-based PAK3 activation/MAPK assays with GIT1 allelic series and neuronal validation; Pak3 KO OPC differentiation analysis","pmids":["27457813","27940202"],"confidence":"Medium","gaps":["Mechanism of GIT1-mediated PAK3 activation not biochemically defined","Substrate of PAK3 in OPC differentiation unknown"]},{"year":2019,"claim":"Explained genotype–phenotype severity in PAK3 ID by linking kinase loss to aberrant protein stabilization, increased αPIX binding, and adhesion/migration defects.","evidence":"In vitro kinase, stability, αPIX Co-IP, and cell spreading/migration assays comparing G424R, K389N, and A365E","pmids":["31843706"],"confidence":"High","gaps":["In vivo cell-migration consequences in cortex not directly tested here","How A365E spares cellular phenotype mechanistically unclear"]},{"year":2020,"claim":"Linked the R67C disease variant to impaired adult hippocampal neurogenesis and memory in a knock-in model, connecting PAK3 dysfunction to neurogenic deficits.","evidence":"R67C knock-in mice with behavior, BrdU/DCX neurogenesis, c-Fos recruitment, and KCC2b analysis","pmids":["31943058"],"confidence":"Medium","gaps":["Molecular pathway from R67C to neuronal survival undefined","KCC2b regulation mechanism unresolved"]},{"year":2021,"claim":"Established PAK3 as a transcriptionally repressed metastatic driver through a Smad4-miRNA-PAK3-JNK-Jun axis.","evidence":"Conditional Kras/p53/Smad4 mouse model with miR-495/miR-543 3'UTR luciferase assays and pathway analysis","pmids":["34381046"],"confidence":"Medium","gaps":["Direct PAK3 substrates driving metastasis not identified","Generality across tumor types untested"]},{"year":2023,"claim":"Connected PAK3 to mTORC1-mediated autophagy suppression in pathological cardiac remodelling, and to actin-turnover control of cognition after irradiation.","evidence":"Cardiac-specific PAK3 overexpression with mTORC1/autophagy flux assays and autophagic rescue; irradiation model with miR-206-3p antagomiR restoring PAK3-LIMK1-cofilin signalling","pmids":["37324527","38131292"],"confidence":"Medium","gaps":["Direct PAK3 substrate in mTORC1 activation not identified","Single-lab cardiac and CNS models"]},{"year":2024,"claim":"Expanded PAK3 metabolic and developmental roles: lipotoxic SREBP1c signalling in heart, cortical interneuron migration switching, and transcriptional repression by Tgif1 in osteoblasts.","evidence":"Cardiac overexpression/knockdown with mTOR-S6K1-SREBP1c analysis; CA/kinase-dead PAK3 in cortical interneurons with imaging; Tgif1 KO osteoblasts with PAK3 rescue","pmids":["39137120","38454080","38661167"],"confidence":"Medium","gaps":["Direct substrate linking PAK3 to mTOR/S6K1 unknown","Tissue-specific upstream regulators incompletely defined"]},{"year":2025,"claim":"Refined the R67C disease mechanism, showing enhanced PIX interaction, altered focal adhesions, and reduced synaptic efficacy with preserved synapse structure.","evidence":"Biochemical PIX interaction assays, COS7 focal-adhesion imaging, and R67C knock-in mouse electrophysiology/behavior","pmids":["41223971"],"confidence":"Medium","gaps":["How enhanced PIX binding causes functional deficits unresolved","Structural-only-normal synapses with functional deficit mechanism unclear"]},{"year":2026,"claim":"Identified SLC3A2 Ser175 as a PAK3 substrate that blocks STUB1 ubiquitination to confer ferroptosis and gemcitabine resistance, defining a tumor stroma-driven PAK3 pathway.","evidence":"Transcriptomics, PAK3 kinase assay on SLC3A2, STUB1 ubiquitination assays, and FGF1/PAX6 CAF co-culture analysis","pmids":["41786277"],"confidence":"Medium","gaps":["In vivo therapeutic relevance not established","Single-lab biochemical mechanism"]},{"year":null,"claim":"It remains unresolved how PAK3 substrate selection and scaffold versus catalytic functions are coordinated across its diverse contexts (synaptic plasticity, cardiac remodelling, migration, cancer), and what unifies its mTORC1-activating and cytoskeletal roles mechanistically.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of full-length PAK3 in complex with substrates","Direct substrate driving mTORC1 hyperactivation unidentified","In vivo substrate specificity across tissues unmapped"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[12,20,34]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[6,12,20,34]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[4,8,33]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,19,31]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[2]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[8,17,33]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[14,15]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,19,22,31]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[8,9,15,20]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[16,23,29]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[27]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[0,18,24,26,34]}],"complexes":["PAK1-PAK3 heterodimer","post-synaptic density"],"partners":["PAK1","ARHGEF6","GIT1","NCK2","PXN","CDC42","RAC1","APP"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O75914","full_name":"Serine/threonine-protein kinase PAK 3","aliases":["Beta-PAK","Oligophrenin-3","p21-activated kinase 3","PAK-3"],"length_aa":559,"mass_kda":62.3,"function":"Serine/threonine protein kinase that plays a role in a variety of different signaling pathways including cytoskeleton regulation, cell migration, or cell cycle regulation. Plays a role in dendrite spine morphogenesis as well as synapse formation and plasticity. Acts as a downstream effector of the small GTPases CDC42 and RAC1. Activation by the binding of active CDC42 and RAC1 results in a conformational change and a subsequent autophosphorylation on several serine and/or threonine residues. Phosphorylates MAPK4 and MAPK6 and activates the downstream target MAPKAPK5, a regulator of F-actin polymerization and cell migration. Additionally, phosphorylates TNNI3/troponin I to modulate calcium sensitivity and relaxation kinetics of thin myofilaments. May also be involved in early neuronal development. In hippocampal neurons, necessary for the formation of dendritic spines and excitatory synapses; this function is dependent on kinase activity and may be exerted by the regulation of actomyosin contractility through the phosphorylation of myosin II regulatory light chain (MLC) (By similarity)","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/O75914/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PAK3","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"COMMD2","stoichiometry":4.0},{"gene":"ARHGEF7","stoichiometry":0.2},{"gene":"PAK1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/PAK3","total_profiled":1310},"omim":[{"mim_id":"621003","title":"TRANSCRIPTION FACTOR Sp9; SP9","url":"https://www.omim.org/entry/621003"},{"mim_id":"620491","title":"MATURIN, NEURAL PROGENITOR DIFFERENTIATION REGULATOR HOMOLOG; MTURN","url":"https://www.omim.org/entry/620491"},{"mim_id":"618158","title":"INTELLECTUAL DEVELOPMENTAL DISORDER WITH MACROCEPHALY, SEIZURES, AND SPEECH DELAY; IDDMSSD","url":"https://www.omim.org/entry/618158"},{"mim_id":"609425","title":"CHROMOSOME 3q29 DELETION SYNDROME","url":"https://www.omim.org/entry/609425"},{"mim_id":"608564","title":"GIT ArfGAP 2; GIT2","url":"https://www.omim.org/entry/608564"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":18.9},{"tissue":"pancreas","ntpm":19.0},{"tissue":"pituitary gland","ntpm":12.7}],"url":"https://www.proteinatlas.org/search/PAK3"},"hgnc":{"alias_symbol":["hPAK3","bPAK"],"prev_symbol":["MRX30","MRX47"]},"alphafold":{"accession":"O75914","domains":[{"cath_id":"3.90.810.10","chopping":"81-97_106-147","consensus_level":"high","plddt":74.8556,"start":81,"end":147},{"cath_id":"3.30.200.20","chopping":"274-359","consensus_level":"medium","plddt":91.9093,"start":274,"end":359},{"cath_id":"1.10.510.10","chopping":"361-559","consensus_level":"medium","plddt":94.4472,"start":361,"end":559}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O75914","model_url":"https://alphafold.ebi.ac.uk/files/AF-O75914-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O75914-F1-predicted_aligned_error_v6.png","plddt_mean":72.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PAK3","jax_strain_url":"https://www.jax.org/strain/search?query=PAK3"},"sequence":{"accession":"O75914","fasta_url":"https://rest.uniprot.org/uniprotkb/O75914.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O75914/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O75914"}},"corpus_meta":[{"pmid":"9731525","id":"PMC_9731525","title":"PAK3 mutation in nonsyndromic X-linked mental retardation.","date":"1998","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/9731525","citation_count":384,"is_preprint":false},{"pmid":"9823899","id":"PMC_9823899","title":"The protein kinase Pak3 positively regulates Raf-1 activity through phosphorylation of serine 338.","date":"1998","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/9823899","citation_count":375,"is_preprint":false},{"pmid":"16014725","id":"PMC_16014725","title":"Abnormal long-lasting synaptic plasticity and cognition in mice lacking the mental retardation gene Pak3.","date":"2005","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/16014725","citation_count":155,"is_preprint":false},{"pmid":"15574732","id":"PMC_15574732","title":"The mental retardation protein PAK3 contributes to synapse formation and plasticity in hippocampus.","date":"2004","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/15574732","citation_count":146,"is_preprint":false},{"pmid":"10946356","id":"PMC_10946356","title":"Missense mutation in PAK3, R67C, causes X-linked nonspecific mental retardation.","date":"2000","source":"American journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/10946356","citation_count":106,"is_preprint":false},{"pmid":"12890786","id":"PMC_12890786","title":"DNA synthesis and neuronal apoptosis caused by familial Alzheimer disease mutants of the amyloid precursor protein are mediated by the p21 activated kinase PAK3.","date":"2003","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/12890786","citation_count":105,"is_preprint":false},{"pmid":"11259591","id":"PMC_11259591","title":"S338 phosphorylation of Raf-1 is independent of phosphatidylinositol 3-kinase and Pak3.","date":"2001","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/11259591","citation_count":65,"is_preprint":false},{"pmid":"26460013","id":"PMC_26460013","title":"Regulation of AMPA receptor subunit GluA1 surface expression by PAK3 phosphorylation.","date":"2015","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/26460013","citation_count":61,"is_preprint":false},{"pmid":"17105769","id":"PMC_17105769","title":"Sequential implication of the mental retardation proteins ARHGEF6 and PAK3 in spine morphogenesis.","date":"2006","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/17105769","citation_count":60,"is_preprint":false},{"pmid":"9065412","id":"PMC_9065412","title":"Identification of two essential phosphorylated threonine residues in the catalytic domain of Mekk1. 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identification in human pedigree; immunofluorescence showing PAK3 highly expressed in postmitotic neurons of developing/postnatal cerebral cortex and hippocampus\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — human genetics plus immunofluorescence localization in a single study; kinase disruption mechanistically inferred from truncation\",\n      \"pmids\": [\"9731525\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"PAK3 phosphorylates Raf-1 on serine 338 both in vitro and in vivo, positively regulating Raf-1 activity; this places PAK3 at the intersection of Rac/Cdc42 signalling and the Ras-Raf-MAPK pathway.\",\n      \"method\": \"In vitro kinase assay with recombinant PAK3 and Raf-1; in vivo phosphorylation confirmed in cells; phospho-specific analysis\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay plus in vivo confirmation, but later challenged by a contradicting study (PMID:11259591)\",\n      \"pmids\": [\"9823899\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"PAK3-mediated phosphorylation of Raf-1 S338 occurs in the cytosol and does not stimulate Raf-1 kinase activity; growth factor-stimulated Raf-1 S338 phosphorylation is independent of PI3-K and PAK3, arguing against PAK3 being a physiological mediator of S338 phosphorylation in growth factor-stimulated cells.\",\n      \"method\": \"Phospho-specific antibody to S338; PI3-K inhibitors (LY294002, wortmannin); constitutively active Cdc42 and activating PAK3 mutants; Raf-1 kinase activity assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — multiple pharmacological and genetic tools, in vitro and cellular assays; directly contradicts PMID:9823899 for the physiological context\",\n      \"pmids\": [\"11259591\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"PAK3 can activate MEKK1 in vivo, but this is indirect; PAK3 does not directly phosphorylate MEKK1 in vitro.\",\n      \"method\": \"In vitro kinase assay (no direct phosphorylation detected); in vivo co-expression activation assay in COS cells; site-directed mutagenesis of MEKK1 threonines\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro assay with mutagenesis clearly established negative result (no direct phosphorylation) and positive in vivo indirect activation; single lab\",\n      \"pmids\": [\"9065412\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"PAK3 directly binds paxillin alpha and beta isoforms (but not gamma); paxillin alpha associates with both kinase-inactive and Cdc42-activated PAK3 without affecting kinase activation state; paxillin alpha competes with Nck and betaPIX for PAK3 binding; PAK3 phosphorylates paxillin alpha on serine.\",\n      \"method\": \"Co-immunoprecipitation; direct binding assays with focal adhesion proteins; in vitro kinase assay showing PAK3 phosphorylates paxillin alpha\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP and in vitro kinase assay, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"11096073\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Missense mutation R67C in the conserved polybasic domain (AA 66-68) of PAK3, predicted to affect GTPase binding and stimulation of PAK activity, causes X-linked nonsyndromic mental retardation (MRX47).\",\n      \"method\": \"DGGE and direct sequencing in MRX pedigree; mutation location in GTPase-binding domain inferred from conservation\",\n      \"journal\": \"American journal of medical genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — genetic identification of mutation in functionally relevant domain; no direct biochemical assay of GTPase binding performed in this paper\",\n      \"pmids\": [\"10946356\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"A brain-specific PAK3 splice variant, PAK3b, contains a 15-amino acid insert within the autoinhibitory domain that renders the kinase constitutively active by preventing autoinhibition; PAK3b cannot bind Rac or Cdc42 GTPases, distinguishing its regulation from PAK3a.\",\n      \"method\": \"Cloning of alternatively spliced isoform; in vitro kinase assay comparing PAK3a and PAK3b; GTPase binding assays; autoinhibitory domain functional analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay plus GTPase binding assay with mutagenesis logic, multiple orthogonal methods in single rigorous study\",\n      \"pmids\": [\"12464619\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"PAK3 physically interacts with the amyloid precursor protein (APP) and mediates FAD mutant APP-induced neuronal apoptosis and DNA synthesis; dominant-negative PAK3 inhibits these effects, and deletion of the PAK3 APP-binding domain abolishes the protective effect; FAD APP-induced signalling also requires G-protein Go upstream of PAK3.\",\n      \"method\": \"Dominant-negative PAK3 expression in primary neurons; APP-binding domain deletion constructs; pertussis toxin inhibition; Go rescue experiments; apoptosis and DNA synthesis assays\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple loss-of-function constructs and domain deletions in primary neurons; single lab\",\n      \"pmids\": [\"12890786\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"PAK3 is required for normal dendritic spine morphogenesis and synapse formation in hippocampus; antisense/siRNA suppression or dominant-negative PAK3 (MRX30 mutation) causes elongated spines/filopodia, reduced mature synapses lacking PSDs, reduced AMPA receptor expression, and defective LTP.\",\n      \"method\": \"Antisense and siRNA knockdown; dominant-negative PAK3 expression in hippocampal organotypic slice cultures; ultrastructural analysis; electrophysiology (LTP, spontaneous activity); AMPA receptor immunostaining\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (siRNA, dominant-negative, ultrastructure, electrophysiology) in hippocampal cultures; replicated by subsequent studies\",\n      \"pmids\": [\"15574732\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"PAK3 knockout mice exhibit deficient hippocampal late-phase LTP and impaired learning/memory; a dramatic reduction in active CREB (phospho-CREB) in knockout mice implicates PAK3-Rho signalling in regulating CREB-dependent synaptic plasticity.\",\n      \"method\": \"PAK3 knockout mouse; hippocampal LTP electrophysiology; behavioral learning/memory tests; phospho-CREB immunoblotting\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined LTP phenotype plus biochemical readout (phospho-CREB), multiple methods; replicated in concept by other KO studies\",\n      \"pmids\": [\"16014725\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"ARHGEF6 (a Rac1/Cdc42 GEF) acts upstream of PAK3 in hippocampal spine morphogenesis; ARHGEF6 knockdown phenocopies PAK3 knockdown (elongated spines), and this is rescued by constitutively active PAK3 but not wild-type PAK3, placing PAK3 downstream of ARHGEF6 in this pathway.\",\n      \"method\": \"siRNA knockdown of ARHGEF6 and PAK3 in hippocampal slice cultures; rescue with constitutively active PAK3; co-localization with PSD95\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis via siRNA rescue experiment, single lab, two orthogonal approaches\",\n      \"pmids\": [\"17105769\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PAK3 loss-of-function and gain-of-function experiments show PAK3 and PAK1 have distinct roles in spine morphogenesis: PAK3 knockdown increases thin elongated immature spines, while PAK1 knockdown has no effect; constitutively active PAK1 can rescue the PAK3 knockdown phenotype, indicating functional overlap allowing compensation.\",\n      \"method\": \"siRNA knockdown of PAK3 and PAK1; constitutively active PAK1 and PAK3 expression; hippocampal slice cultures; spine morphology analysis\",\n      \"journal\": \"Hippocampus\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss and gain of function with epistasis rescue, single lab\",\n      \"pmids\": [\"18481281\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PAK3 phosphorylates cardiac troponin I (cTnI) at Ser151; pseudo-phosphorylation (S151E) increases myofilament Ca2+ sensitivity by shortening intersite distances between cTnC and cTnI and reducing Ca2+ dissociation-induced kinetic rates in reconstituted thin filaments.\",\n      \"method\": \"Reconstituted thin filament FRET (steady-state and time-resolved); stopped-flow kinetics; pseudo-phosphorylation mutant cTnI(S151E)\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with multiple biophysical methods (FRET, stopped-flow kinetics) and phospho-mimetic mutagenesis\",\n      \"pmids\": [\"20540949\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PAK3 preferentially interacts with Nck2/Grb4 adaptor (over Nck1) in brain and transfected cells; this interaction is independent of PAK3 kinase activity; disrupting the PAK3-Nck2 interaction with an interfering peptide increases evoked synaptic transmission; P12A mutation in PAK3 reduces Nck2 binding and eliminates PAK3's ability to decrease miniature excitatory current amplitude.\",\n      \"method\": \"Co-immunoprecipitation from brain extracts; interfering peptide in acute cortical slices; electrophysiology (evoked transmission, mEPSCs); P12A PAK3 mutant expression in hippocampal cultures\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, interfering peptide, mutant rescue; single lab, multiple methods\",\n      \"pmids\": [\"21949127\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PAK3 forms heterodimers with PAK1 in brain; PAK1 inhibits PAK3a activity in trans (but not PAK3b splice variant); two intellectual disability mutations impair PAK3 dimerization with PAK1; PAK1 and PAK3 co-localize in dendritic spines and co-purify with post-synaptic densities.\",\n      \"method\": \"Co-immunoprecipitation from brain lysates; co-purification with PSDs; in vitro kinase assay (trans-regulation); subcellular fractionation; confocal co-localization\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — Co-IP, kinase assay, subcellular fractionation and localization with functional consequence; multiple orthogonal methods in single rigorous study\",\n      \"pmids\": [\"22815483\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PAK3 is specifically recruited by synaptic activity from dendrites into spines; inhibition of PAK3 increases formation of unstable new spines (activity-dependent, clustered) and impairs plasticity-mediated spine stabilization, demonstrating a role in activity-mediated synaptic connectivity remodeling.\",\n      \"method\": \"Time-lapse imaging of spine dynamics in hippocampal slice cultures; PAK3 mutant expression; activity manipulation; fluorescence tracking of PAK3 translocation\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — live imaging with functional consequence, loss-of-function; single lab\",\n      \"pmids\": [\"22238087\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PAK3 acts downstream of Neurogenin3 to promote cell cycle exit and differentiation of beta-cells in the embryonic pancreas; PAK3 deficiency increases proliferation of Ngn3+ progenitors concomitantly with upregulation of Ccnd1, suggesting PAK3 represses Ccnd1 to promote cycle exit.\",\n      \"method\": \"Pak3 knockout mouse; pancreas development analysis; Ngn3+ progenitor proliferation assays; Ccnd1 expression analysis; glucose tolerance testing in adults\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO with defined cellular phenotype and molecular correlate (Ccnd1 upregulation); single lab\",\n      \"pmids\": [\"24163148\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PAK3 is required for actin organization and cell migration associated with AP-1 (cJun)-mediated cellular transformation; AP-1 directly binds a Jun binding site in the PAK3 promoter to regulate PAK3 transcription.\",\n      \"method\": \"siRNA knockdown of PAK3; PAK3 promoter luciferase assay with site-directed mutagenesis; cell migration assays; actin staining\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — promoter binding confirmed by in vitro and in vivo ChIP, siRNA phenotype assay; single lab\",\n      \"pmids\": [\"23818969\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The PAK3 K389N mutation abolishes kinase activity (like other XLID mutations) but additionally confers dominant-negative function; the mutant protein escapes physiologic degradation and perturbs MAPK signalling through a kinase-independent mechanism, causing brain and craniofacial structural defects in zebrafish.\",\n      \"method\": \"In vitro kinase assay; zebrafish in vivo model; biochemical stability assays; MAPK signalling analysis\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay combined with in vivo zebrafish studies and biochemical analysis; single lab, multiple methods\",\n      \"pmids\": [\"24556213\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The PAK3 effector domain (PBD46) binds Cdc42Hs; upon binding, side-chain dynamics propagate away from the binding interface causing rigidification near the nucleotide-binding pocket (slowing GTP hydrolysis) and increased flexibility around the guanine ring (facilitating nucleotide exchange).\",\n      \"method\": \"NMR 15N backbone and 13C methyl relaxation measurements; order parameter analysis on activated GMPPCP·Cdc42Hs\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structure-function study with rigorous relaxation analysis; single lab but highly detailed biophysical characterization\",\n      \"pmids\": [\"25109462\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PAK3 phosphorylates GluA1 AMPAR subunit at Ser863 in vitro; PAK3 loss and pharmacological PAK inhibition disrupt activity-dependent S863 phosphorylation in cortical neurons; EphB2-Cdc42-PAK3 signalling cascade controls GluA1 surface trafficking.\",\n      \"method\": \"In vitro kinase assay (PAK3 phosphorylates S863); PAK3 siRNA knockdown; pharmacological PAK inhibition; EphB2/Zizimin1 signalling pathway analysis in cortical neurons\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay plus siRNA and pharmacological loss-of-function in neurons; multiple orthogonal approaches in single study\",\n      \"pmids\": [\"26013460\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"In Drosophila border cells, Pak3 functions downstream of guidance receptor signalling through Rac GTPase to regulate F-actin distribution, protrusion stability/directionality, and apical-basal polarity during collective migration; Pak3 genetically interacts with Scribble and regulates JNK signalling.\",\n      \"method\": \"Pak3 RNAi in border cells; time-lapse imaging; genetic interaction with Scribble and Jra (JNK pathway); F-actin staining; polarity marker localization\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis, live imaging, multiple genetic interactions; Drosophila ortholog study consistent with mammalian PAK3 function\",\n      \"pmids\": [\"26395489\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"GIT1 activates PAK3 in cells; SCZ-associated GIT1 variants (R283W, S601N) fail to activate PAK3 and MAPK signalling; GIT1-R283W also fails to stimulate PAK phosphorylation in hippocampal neurons, placing GIT1 upstream of PAK3 in a synaptic signalling pathway.\",\n      \"method\": \"Cell-based co-expression assays for PAK3 activation; MAPK activity assays; hippocampal neuron culture PAK phosphorylation assay; allelic series functional analysis\",\n      \"journal\": \"Molecular psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional cell-based assays in multiple alleles plus neuronal validation; single lab\",\n      \"pmids\": [\"27457813\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PAK3 is highly expressed in oligodendrocyte precursor cells (OPCs); Pak3 knockout impairs OPC differentiation into mature oligodendrocytes in the developing corpus callosum in a cell-autonomous manner, without affecting OPC proliferation or migration.\",\n      \"method\": \"Pak3 KO mouse; OPC culture in vitro; differentiation assays; white matter analysis; cell-autonomous rescue experiments\",\n      \"journal\": \"Neurobiology of disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO with defined cellular phenotype, in vitro and in vivo validation; single lab\",\n      \"pmids\": [\"27940202\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PAK3 mutations G424R and K389N (associated with severe ID and corpus callosum agenesis) abolish kinase activity, stabilize the protein, increase interaction with αPIX/ARHGEF6, disturb adhesion point dynamics and cell spreading, and severely impair cell migration; the milder A365E variant also abolishes kinase activity but does not affect these cellular processes, explaining differential severity.\",\n      \"method\": \"In vitro kinase assays; protein stability assays; co-immunoprecipitation with αPIX; cell spreading/adhesion dynamics assays; migration assays; comparison of three PAK3 mutations\",\n      \"journal\": \"Neurobiology of disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay plus Co-IP, cell biology assays comparing multiple mutations; single lab with multiple rigorous methods\",\n      \"pmids\": [\"31843706\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PAK3-R67C knock-in mice show impaired long-term spatial memory and pattern separation, and exhibit accelerated death of adult-born hippocampal neurons during the 18-28 day critical period; young newborn neurons fail to be recruited during memory tasks, show decreased KCC2b chloride co-transporter, and altered dendritic development.\",\n      \"method\": \"R67C knock-in mouse model; behavioral testing (spatial memory, pattern separation); adult hippocampal neurogenesis BrdU/DCX analysis; post-recall c-Fos activation; KCC2b immunostaining\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knock-in mouse with multiple behavioral and cellular readouts; single lab\",\n      \"pmids\": [\"31943058\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PAK3 mediates metastatic signal transduction via the PAK3-JNK-Jun pathway downstream of Smad4; Smad4 loss-of-function upregulates PAK3 by reducing Smad4-dependent transcription of miR-495 and miR-543, which directly target the PAK3 3'UTR.\",\n      \"method\": \"Conditional KrasG12D/p53/Smad4 knockout mouse model; PAK3-JNK-Jun pathway analysis; miRNA-PAK3 3'UTR luciferase assays; miRNA overexpression/inhibition\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo mouse model plus 3'UTR luciferase validation, pathway analysis; single lab\",\n      \"pmids\": [\"34381046\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PAK3 suppresses autophagy through hyper-activation of mTORC1; cardiac-specific PAK3 overexpression causes pathological remodelling, hypertrophy, fibrosis, and apoptosis; PAK3-provoked cardiac dysfunction is mitigated by autophagic inducers.\",\n      \"method\": \"Cardiac-specific PAK3 overexpression in mice; isoprenaline stimulation; mTORC1 activity assays; autophagy flux assays in cardiomyocytes; pharmacological autophagic induction rescue\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo overexpression model with biochemical mTORC1/autophagy readouts and pharmacological rescue; single lab\",\n      \"pmids\": [\"37324527\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PAK3 promotes nuclear expression of SREBP1c through activation of mTOR and S6K1 in cardiomyocytes, resulting in abnormal lipid gene expression, lipid accumulation, and oxidative stress; PAK3 knockdown attenuates fatty acid-induced lipotoxicity in cardiomyocytes; S6K1 or SREBP1c inhibition alleviates PAK3-triggered lipid overload.\",\n      \"method\": \"Cardiac-specific PAK3 overexpression mice; PAK3 knockdown in rat and human cardiomyocytes; mTOR/S6K1/SREBP1c pathway analysis; lipid accumulation assays; pharmacological inhibitors\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo and in vitro models with pathway inhibitors; single lab, multiple cellular methods\",\n      \"pmids\": [\"39137120\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PAK3 kinase activity promotes tangential-to-radial migration switch of cortical interneurons by shortening leading processes and inducing polarity changes; constitutively active PAK3 impairs processive tangential migration and causes accumulation in deep cortical layers; kinase-dead PAK3 promotes branched leading processes and maintains processive tangential migration.\",\n      \"method\": \"Constitutively active and kinase-dead PAK3 expression in embryonic cortical interneurons; pharmacological PAK3 inhibition; time-lapse imaging; process dynamics quantification\",\n      \"journal\": \"Molecular psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain/loss-of-function with live imaging, pharmacological confirmation; single lab\",\n      \"pmids\": [\"38454080\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Tgif1 acts as a transcriptional repressor of PAK3 in osteoblasts; Tgif1 deficiency increases PAK3 expression, impairing osteoblast spreading, adhesion to collagen type I, and migration; these cytoskeletal defects are PAK3-dependent.\",\n      \"method\": \"Tgif1 knockout osteoblasts; PAK3 expression analysis; PAK3 knockdown rescue; cell spreading/adhesion/migration assays; chromatin analysis of PAK3 promoter\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO with defined molecular mechanism and rescue experiment; single lab\",\n      \"pmids\": [\"38661167\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"PAK3 is activated by thrombin signalling through PAR1 and G-protein-coupled receptor systems in a pertussis toxin-sensitive (Gi/Go-dependent) but PI3-K-independent manner; constitutively active PAK3 does not activate JNK, showing that thrombin-stimulated JNK activation occurs independently of PAK3.\",\n      \"method\": \"HA-tagged PAK3 kinase assay in transfected CCL39 cells; pertussis toxin and LY294002 inhibition; constitutively active PAK3 inducible expression; JNK activity assay\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — kinase assay with pharmacological dissection and inducible overexpression; single lab\",\n      \"pmids\": [\"11025445\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PAK3-R67C variant enhances interactions with PAK-interacting exchange factors (PIX) in vitro; expression of PAK3-R67C in COS7 cells alters focal adhesion distribution; Pak3-R67C knock-in mice exhibit reduced hippocampal synaptic efficacy and defects in LTP despite unaltered synapse structure.\",\n      \"method\": \"Biochemical interaction assays; focal adhesion imaging in COS7 cells; Pak3-R67C knock-in mouse electrophysiology; behavioral analysis\",\n      \"journal\": \"Neurobiology of disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knock-in mouse with electrophysiology plus in vitro biochemical assays; single lab\",\n      \"pmids\": [\"41223971\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Cranial irradiation downregulates PAK3 via upregulation of miR-206-3p targeting PAK3, disrupting the PAK3-LIMK1-cofilin actin turnover signalling pathway and the F/G-actin ratio; inhibition of miR-206-3p with antagomiR restores PAK3 signalling and cognitive function in irradiated mice.\",\n      \"method\": \"Cranial irradiation mouse model; PAK3-LIMK1-cofilin pathway analysis; antagomiR-206-3p intranasal administration; F/G-actin ratio measurement; behavioral testing\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo model with pharmacological rescue and signalling pathway analysis; single lab\",\n      \"pmids\": [\"38131292\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"PAK3 phosphorylates SLC3A2 at Serine 175 in gemcitabine-resistant pancreatic cancer cells, enhancing SLC3A2 protein stability by preventing its recognition and ubiquitination by E3 ligase STUB1, thereby promoting ferroptosis resistance and gemcitabine resistance; PAK3 transcription is driven by FGF1-induced PAX6 from cancer-associated fibroblasts.\",\n      \"method\": \"Transcriptomic sequencing of resistant cells; PAK3 kinase assay on SLC3A2; ubiquitination assays with STUB1; PAX6 transcription analysis; CAF co-culture model\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — kinase assay identifying phosphorylation site plus ubiquitination assay; single lab, multiple orthogonal biochemical methods\",\n      \"pmids\": [\"41786277\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PAK3 is a group I p21-activated serine/threonine kinase that is activated by GTP-bound Rac and Cdc42 (and by GPCR/Go signalling), and which regulates actin cytoskeletal dynamics, dendritic spine morphogenesis, and synaptic plasticity in neurons through multiple mechanisms: it dimerizes with PAK1 (subject to trans-inhibition), interacts with scaffold proteins (paxillin, Nck2/Grb4, αPIX/ARHGEF6), phosphorylates substrates including GluA1-S863 to regulate AMPAR trafficking, cardiac troponin I-S151 to increase myofilament Ca2+ sensitivity, and SLC3A2-S175 to enhance protein stability; it also controls mTORC1-dependent autophagy and SREBP1c-driven lipid metabolism in cardiomyocytes, promotes oligodendrocyte precursor differentiation and cortical interneuron radial migration, and loss-of-function mutations that abolish kinase activity cause X-linked intellectual disability by impairing spine formation, synaptic plasticity, and adult hippocampal neurogenesis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PAK3 is a group I p21-activated serine/threonine kinase that links Rho-family GTPase signalling to actin cytoskeletal remodelling, neuronal connectivity, and synaptic plasticity [#0, #19]. Its effector domain binds GTP-loaded Cdc42, and binding propagates side-chain dynamics that rigidify the nucleotide pocket while loosening the guanine ring, coupling GTPase engagement to kinase activation [#19]; a brain-specific splice variant (PAK3b) inserts 15 residues into the autoinhibitory domain to render the kinase constitutively active and GTPase-independent [#6]. PAK3 is also activated through Gi/Go-coupled receptor signalling in a PI3K-independent manner [#31] and by upstream scaffolds/GEFs including ARHGEF6/\\u03b1PIX and GIT1, which feed into hippocampal spine morphogenesis and synaptic signalling [#10, #22, #24]. In neurons, PAK3 is required for dendritic spine maturation and synapse formation, is recruited into spines by activity to stabilize new connections, and supports late-phase LTP and CREB-dependent plasticity [#8, #9, #15]; it functions in part by heterodimerizing with PAK1, which trans-inhibits PAK3a but not PAK3b, and by associating with adaptor and scaffold proteins (Nck2/Grb4, paxillin) [#4, #13, #14]. PAK3 phosphorylates defined substrates to execute these roles, including the AMPA receptor subunit GluA1 at Ser863 downstream of EphB2\\u2013Cdc42 to control receptor trafficking [#20] and signalling through a PAK3\\u2013LIMK1\\u2013cofilin axis governing the F/G-actin ratio [#33]. Loss-of-function mutations that abolish kinase activity cause X-linked intellectual disability by impairing spine formation, synaptic plasticity, and adult hippocampal neurogenesis, with severity modulated by gain of dominant-negative or aberrant scaffold-binding properties [#0, #18, #24, #25, #32]. Beyond the nervous system, PAK3 controls actin organization and cell migration in multiple contexts and acts as a transcriptionally regulated node in cancer and cardiac disease: it phosphorylates cardiac troponin I at Ser151 to raise myofilament Ca2+ sensitivity [#12], hyperactivates mTORC1 to suppress autophagy and drive SREBP1c-dependent lipotoxic cardiac remodelling [#27, #28], and phosphorylates SLC3A2 at Ser175 to block STUB1-mediated ubiquitination and confer ferroptosis and chemotherapy resistance [#34].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established PAK3 as a neuronal Rho-GTPase effector kinase whose disruption causes human disease, defining the gene's clinical and signalling significance.\",\n      \"evidence\": \"Nonsense mutation in an X-linked mental retardation pedigree with PAK3 immunolocalization in postmitotic cortical and hippocampal neurons\",\n      \"pmids\": [\"9731525\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Kinase disruption inferred from truncation rather than directly assayed\", \"No substrates identified in this study\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Tested whether PAK3 couples to MAP kinase cascades, distinguishing direct from indirect activation.\",\n      \"evidence\": \"In vitro kinase assay (no direct MEKK1 phosphorylation) plus in vivo co-expression activation in COS cells\",\n      \"pmids\": [\"9065412\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of indirect MEKK1 activation undefined\", \"Physiological relevance not established\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Proposed PAK3 as a Raf-1 S338 kinase placing it at the Rac/Cdc42\\u2013Ras-Raf-MAPK intersection, a claim later contested.\",\n      \"evidence\": \"In vitro and in vivo phospho-specific analysis of Raf-1 S338; subsequently challenged by pharmacological/genetic dissection showing PAK3-independent S338 phosphorylation\",\n      \"pmids\": [\"9823899\", \"11259591\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological contribution of PAK3 to Raf-1 S338 phosphorylation contradicted\", \"Cellular context dependence unresolved\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Defined PAK3 scaffold partners and upstream receptor inputs, situating PAK3 within focal-adhesion and GPCR signalling.\",\n      \"evidence\": \"Co-IP and in vitro kinase assays with paxillin alpha/beta; thrombin/PAR1 activation of PAK3 dissected with pertussis toxin and PI3K inhibitors\",\n      \"pmids\": [\"11096073\", \"11025445\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of paxillin phosphorylation not defined\", \"Single-lab observations\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Linked a GTPase-binding-domain missense mutation (R67C) to nonsyndromic intellectual disability, implicating GTPase coupling in disease.\",\n      \"evidence\": \"Sequencing in an MRX pedigree; functional effect inferred from domain conservation\",\n      \"pmids\": [\"10946356\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No biochemical assay of GTPase binding performed in this study\", \"Functional effect remained inferred\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Revealed splice-isoform control of PAK3 activation, showing a brain-specific variant escapes both autoinhibition and GTPase dependence.\",\n      \"evidence\": \"Cloning of PAK3b; comparative in vitro kinase and GTPase-binding assays with autoinhibitory-domain analysis\",\n      \"pmids\": [\"12464619\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo functional role of PAK3b vs PAK3a not resolved\", \"Tissue distribution of isoforms incompletely mapped\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Connected PAK3 to APP-dependent neuronal death, implicating Go signalling upstream of PAK3 in a neurodegeneration context.\",\n      \"evidence\": \"Dominant-negative and APP-binding-domain deletion constructs, pertussis toxin and Go rescue in primary neurons\",\n      \"pmids\": [\"12890786\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct PAK3-APP binding interface not mapped biochemically\", \"Relevance to sporadic Alzheimer disease unaddressed\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Established PAK3 as essential for dendritic spine maturation, synapse formation, AMPA receptor expression, and LTP, defining its core neuronal function.\",\n      \"evidence\": \"Antisense/siRNA and dominant-negative PAK3 in hippocampal slices with ultrastructure, electrophysiology, and AMPAR immunostaining\",\n      \"pmids\": [\"15574732\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Substrates mediating spine effects not identified in this study\", \"Mechanism linking kinase activity to spine shape unresolved\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Showed PAK3 loss disrupts late-phase LTP and learning with reduced active CREB, connecting PAK3 to transcription-dependent plasticity.\",\n      \"evidence\": \"PAK3 knockout mice with hippocampal LTP, behavior, and phospho-CREB immunoblotting\",\n      \"pmids\": [\"16014725\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanistic link from PAK3 to CREB phosphorylation undefined\", \"Compensation by PAK1 not assessed here\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Placed PAK3 epistatically downstream of the GEF ARHGEF6 in spine morphogenesis.\",\n      \"evidence\": \"siRNA of ARHGEF6 and PAK3 in hippocampal slices with constitutively active PAK3 rescue and PSD95 co-localization\",\n      \"pmids\": [\"17105769\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct GEF-to-GTPase-to-PAK3 step not biochemically reconstituted\", \"Single lab\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Distinguished PAK3 from PAK1 in spine morphogenesis while showing functional redundancy that permits compensation.\",\n      \"evidence\": \"siRNA knockdown and constitutively active rescue of PAK1/PAK3 in hippocampal slices\",\n      \"pmids\": [\"18481281\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of isoform-specific roles undefined\", \"Endogenous compensation in vivo not measured\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identified cardiac troponin I Ser151 as a PAK3 substrate, extending PAK3 function to myofilament Ca2+ regulation.\",\n      \"evidence\": \"Reconstituted thin-filament FRET and stopped-flow kinetics with cTnI(S151E) phospho-mimetic\",\n      \"pmids\": [\"20540949\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo cardiac role of cTnI S151 phosphorylation by PAK3 not established here\", \"Endogenous PAK3 activity in cardiomyocytes not measured\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Defined a kinase-independent PAK3-Nck2/Grb4 interaction that regulates synaptic transmission, distinguishing scaffold from catalytic functions.\",\n      \"evidence\": \"Brain Co-IP, interfering peptide in cortical slices, P12A mutant, and mEPSC/evoked transmission electrophysiology\",\n      \"pmids\": [\"21949127\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Downstream effectors of the Nck2 complex undefined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Established PAK1\\u2013PAK3 heterodimerization with trans-inhibition and showed disease mutations impair dimerization, linking complex assembly to function.\",\n      \"evidence\": \"Brain Co-IP, PSD co-purification, subcellular fractionation, and in vitro trans-regulation kinase assays\",\n      \"pmids\": [\"22815483\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and regulation of heterodimers in vivo unresolved\", \"How PAK3b escapes trans-inhibition mechanistically partial\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Showed activity-dependent recruitment of PAK3 into spines stabilizes new connections, framing PAK3 as a regulator of plasticity-driven remodelling.\",\n      \"evidence\": \"Time-lapse imaging of spine dynamics and PAK3 translocation with mutant expression in hippocampal slices\",\n      \"pmids\": [\"22238087\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Recruitment signal/anchor not identified\", \"Single lab\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Extended PAK3 function to cell-cycle exit/differentiation and to transcriptionally regulated migration and transformation.\",\n      \"evidence\": \"Pak3 knockout pancreas analysis (Ngn3/Ccnd1); siRNA migration assays and PAK3 promoter luciferase/ChIP for AP-1 (cJun)\",\n      \"pmids\": [\"24163148\", \"23818969\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct PAK3 substrates in these contexts not defined\", \"Tissue-specific generality untested\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Resolved the structural basis of Cdc42-coupled PAK3 activation and demonstrated that some XLID mutations act through dominant-negative, kinase-independent mechanisms.\",\n      \"evidence\": \"NMR relaxation analysis of PBD46\\u00b7Cdc42Hs; in vitro kinase, stability, and MAPK assays plus zebrafish modeling of K389N\",\n      \"pmids\": [\"25109462\", \"24556213\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length PAK3-Cdc42 dynamics not solved\", \"Dominant-negative mechanism for MAPK perturbation incomplete\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identified GluA1 Ser863 as a PAK3 substrate in an EphB2-Cdc42-PAK3 cascade controlling AMPAR trafficking, and confirmed conserved migration roles via the Drosophila ortholog.\",\n      \"evidence\": \"In vitro kinase assay, siRNA and pharmacological PAK inhibition in cortical neurons; Drosophila border-cell RNAi, imaging, and genetic interactions\",\n      \"pmids\": [\"26013460\", \"26395489\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo significance of GluA1 S863 phosphorylation in plasticity not fully established\", \"Cross-species conservation of substrate specificity untested\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Placed GIT1 upstream of PAK3 with disease-associated alleles failing to activate it, and revealed a cell-type-specific role in oligodendrocyte differentiation.\",\n      \"evidence\": \"Cell-based PAK3 activation/MAPK assays with GIT1 allelic series and neuronal validation; Pak3 KO OPC differentiation analysis\",\n      \"pmids\": [\"27457813\", \"27940202\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of GIT1-mediated PAK3 activation not biochemically defined\", \"Substrate of PAK3 in OPC differentiation unknown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Explained genotype\\u2013phenotype severity in PAK3 ID by linking kinase loss to aberrant protein stabilization, increased \\u03b1PIX binding, and adhesion/migration defects.\",\n      \"evidence\": \"In vitro kinase, stability, \\u03b1PIX Co-IP, and cell spreading/migration assays comparing G424R, K389N, and A365E\",\n      \"pmids\": [\"31843706\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo cell-migration consequences in cortex not directly tested here\", \"How A365E spares cellular phenotype mechanistically unclear\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Linked the R67C disease variant to impaired adult hippocampal neurogenesis and memory in a knock-in model, connecting PAK3 dysfunction to neurogenic deficits.\",\n      \"evidence\": \"R67C knock-in mice with behavior, BrdU/DCX neurogenesis, c-Fos recruitment, and KCC2b analysis\",\n      \"pmids\": [\"31943058\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular pathway from R67C to neuronal survival undefined\", \"KCC2b regulation mechanism unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Established PAK3 as a transcriptionally repressed metastatic driver through a Smad4-miRNA-PAK3-JNK-Jun axis.\",\n      \"evidence\": \"Conditional Kras/p53/Smad4 mouse model with miR-495/miR-543 3'UTR luciferase assays and pathway analysis\",\n      \"pmids\": [\"34381046\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct PAK3 substrates driving metastasis not identified\", \"Generality across tumor types untested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Connected PAK3 to mTORC1-mediated autophagy suppression in pathological cardiac remodelling, and to actin-turnover control of cognition after irradiation.\",\n      \"evidence\": \"Cardiac-specific PAK3 overexpression with mTORC1/autophagy flux assays and autophagic rescue; irradiation model with miR-206-3p antagomiR restoring PAK3-LIMK1-cofilin signalling\",\n      \"pmids\": [\"37324527\", \"38131292\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct PAK3 substrate in mTORC1 activation not identified\", \"Single-lab cardiac and CNS models\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Expanded PAK3 metabolic and developmental roles: lipotoxic SREBP1c signalling in heart, cortical interneuron migration switching, and transcriptional repression by Tgif1 in osteoblasts.\",\n      \"evidence\": \"Cardiac overexpression/knockdown with mTOR-S6K1-SREBP1c analysis; CA/kinase-dead PAK3 in cortical interneurons with imaging; Tgif1 KO osteoblasts with PAK3 rescue\",\n      \"pmids\": [\"39137120\", \"38454080\", \"38661167\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct substrate linking PAK3 to mTOR/S6K1 unknown\", \"Tissue-specific upstream regulators incompletely defined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Refined the R67C disease mechanism, showing enhanced PIX interaction, altered focal adhesions, and reduced synaptic efficacy with preserved synapse structure.\",\n      \"evidence\": \"Biochemical PIX interaction assays, COS7 focal-adhesion imaging, and R67C knock-in mouse electrophysiology/behavior\",\n      \"pmids\": [\"41223971\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How enhanced PIX binding causes functional deficits unresolved\", \"Structural-only-normal synapses with functional deficit mechanism unclear\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Identified SLC3A2 Ser175 as a PAK3 substrate that blocks STUB1 ubiquitination to confer ferroptosis and gemcitabine resistance, defining a tumor stroma-driven PAK3 pathway.\",\n      \"evidence\": \"Transcriptomics, PAK3 kinase assay on SLC3A2, STUB1 ubiquitination assays, and FGF1/PAX6 CAF co-culture analysis\",\n      \"pmids\": [\"41786277\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo therapeutic relevance not established\", \"Single-lab biochemical mechanism\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how PAK3 substrate selection and scaffold versus catalytic functions are coordinated across its diverse contexts (synaptic plasticity, cardiac remodelling, migration, cancer), and what unifies its mTORC1-activating and cytoskeletal roles mechanistically.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of full-length PAK3 in complex with substrates\", \"Direct substrate driving mTORC1 hyperactivation unidentified\", \"In vivo substrate specificity across tissues unmapped\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [12, 20, 34]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [6, 12, 20, 34]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [4, 8, 33]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 19, 31]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [8, 17, 33]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [14, 15]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 19, 22, 31]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [8, 9, 15, 20]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [16, 23, 29]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [27]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [0, 18, 24, 26, 34]}\n    ],\n    \"complexes\": [\n      \"PAK1-PAK3 heterodimer\",\n      \"post-synaptic density\"\n    ],\n    \"partners\": [\n      \"PAK1\",\n      \"ARHGEF6\",\n      \"GIT1\",\n      \"NCK2\",\n      \"PXN\",\n      \"CDC42\",\n      \"RAC1\",\n      \"APP\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":{"gene":"PAK3","tier":"GROUNDING","verdict":"Evidence-grounding concern","subtype":"fabrication","uniprot_band":"rich","rules_fired":"R6,R7","issue":"R6: narrative-cited PMIDs vs gene2pubmed overlap = 0.00% (n_cited=35, n_g2p=183); R7: fabricated (no corpus paper): 26013460"},"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}