{"gene":"PREX1","run_date":"2026-04-28T19:45:45","timeline":{"discoveries":[{"year":2002,"finding":"P-Rex1 is a 185 kDa guanine-nucleotide exchange factor (GEF) for Rac that is directly, substantially, and synergistically activated by PtdIns(3,4,5)P3 and Gβγ subunits both in vitro and in vivo; it was purified from neutrophil cytosol and functions as a coincidence detector in PIP3 and Gβγ signaling pathways downstream of heterotrimeric G proteins.","method":"Biochemical purification from neutrophil cytosol, in vitro GEF assay, antisense oligonucleotide knockdown, recombinant protein expression","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro GEF assay with purified components, replicated across multiple methods in foundational paper","pmids":["11955434"],"is_preprint":false},{"year":2005,"finding":"PKA phosphorylates P-Rex1, inhibiting its PIP3- and Gβγ-stimulated GEF activity; Gβγ is 47-fold less potent in activating phosphorylated versus dephosphorylated P-Rex1, and PKA activation in HEK293T cells reduces GTP-bound Rac levels.","method":"In vitro GEF assay with purified proteins, 32P-labeling in HEK293T cells, pharmacological activation of PKA","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with quantitative kinetics, confirmed in cells with multiple reagents","pmids":["16301320"],"is_preprint":false},{"year":2005,"finding":"P-Rex1 acts as a primary GEF for Rac2 (but not Rac1) in mouse neutrophils; P-Rex1 shows higher affinity for dominant-negative Rac2(S17N) than Rac1(S17N) by co-immunoprecipitation; P-Rex1 knockout impairs fMLP-induced Rac2 activation, F-actin formation, superoxide production, and chemotaxis.","method":"P-Rex1 knockout mouse, co-immunoprecipitation with Rac2(S17N) vs. Rac1(S17N), Rac activation assay, chemotaxis assay","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with defined cellular phenotype and substrate preference confirmed by differential pulldown","pmids":["16243036"],"is_preprint":false},{"year":2005,"finding":"P-Rex1 knockout mice display impaired GPCR-dependent Rac2 activation, absent LPS-primed ROS formation, and defective recruitment of neutrophils to inflammatory sites, establishing P-Rex1 as a key regulator of a subset of Rac-dependent neutrophil responses downstream of GPCRs.","method":"P-Rex1 knockout mouse, Rac activation assay, ROS measurement, in vivo inflammatory recruitment assay, chemotaxis assay","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with multiple defined cellular phenotypes, independently replicated","pmids":["16243035"],"is_preprint":false},{"year":2005,"finding":"Gβγ dimers composed of Gβ1–4 (but not Gβ5) paired with γ2 activate P-Rex1; the farnesylated γ11 subunit and Gβ1γ12 are less effective activators; Gα subunits (Gs, Gi, Gq, G12, G13) activated by AlF4- cannot activate P-Rex1, demonstrating subunit-specific regulation.","method":"In vitro GEF assay with purified recombinant G protein subunits reconstituted in synthetic lipid vesicles","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro with pure components across a panel of subunits","pmids":["16301321"],"is_preprint":false},{"year":2007,"finding":"Membrane translocation of P-Rex1 requires both Gβγ and PI3K (PIP3) synergistically; neither alone causes significant translocation. The DH/PH domain tandem is sufficient for this synergistic membrane localization, GEF activity is not required for translocation, and membrane-derived P-Rex1 has higher basal GEF activity than cytosol-derived P-Rex1.","method":"Subcellular fractionation of Sf9 cells co-expressing P-Rex1 with Gβγ and/or PI3K; P-Rex1 domain mutant analysis; in vitro Rac2-GEF activity assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 — systematic domain mutant analysis combined with biochemical fractionation and in vitro GEF assay","pmids":["17698854"],"is_preprint":false},{"year":2007,"finding":"P-Rex1 and P-Rex2 interact with mTOR through their tandem DEP domains; P-Rex1 associates with both mTORC1 and mTORC2 but is only active in the mTORC2 complex; dominant-negative P-Rex1 and shRNA knockdown reduce mTOR/mTORC2-dependent Rac activation and cell migration.","method":"Co-immunoprecipitation, dominant-negative constructs, shRNA knockdown, Rac activation assay, cell migration assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2–3 — single lab, Co-IP plus functional knockdown, but mechanistic model not fully reconstituted","pmids":["17565979"],"is_preprint":false},{"year":2007,"finding":"Endogenous P-Rex1 translocates from cytoplasm to the leading edge of polarized human neutrophils in a Gβγ- and PIP3-dependent manner upon chemoattractant stimulation, where it co-localizes with F-actin and Rac2; PKA activation inhibits P-Rex1 translocation.","method":"Immunofluorescence microscopy of human neutrophils, pharmacological inhibitors of PI3K and Gβγ, PKA activation","journal":"Journal of leukocyte biology","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization experiment with functional consequence, single lab","pmids":["17227822"],"is_preprint":false},{"year":2008,"finding":"The second DEP and first PDZ domains of P-Rex1 associate with its IP4P domain; this domain-domain interaction is essential for Gβγ-induced activation and PKA-induced inhibition. PKA phosphorylation prevents domain-domain interaction and Gβγ binding, revealing an intramolecular regulatory mechanism.","method":"Immunoprecipitation of truncated P-Rex1 mutants, in vitro GEF assay, PAK1/2 phosphorylation assay, alanine-substitution mutagenesis","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 1–2 — in vitro GEF assay plus mutagenesis, single lab","pmids":["18514484"],"is_preprint":false},{"year":2008,"finding":"P-Rex1 localizes to the distal tips of developing neurites and axonal growth cones in PC12 cells and hippocampal neurons; P-Rex1 activates Rac3 in neuronal cells; P-Rex1 expression inhibits NGF-stimulated neurite differentiation through its GEF activity, while P-Rex1 knockdown promotes neurite hyper-elongation with decreased F-actin at the growth cone.","method":"Immunofluorescence in PC12 cells and hippocampal neurons, GEF-dead mutant analysis, RNAi knockdown, cytochalasin D rescue, Rac3 GTPase activity assay","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization plus functional GEF-dead rescue analysis, single lab","pmids":["18697831"],"is_preprint":false},{"year":2009,"finding":"P-Rex1 is required for SDF-1/CXCL12-stimulated Rac activation, endothelial cell migration, and in vitro angiogenesis via the CXCR4/Gβγ/PI3K pathway; P-Rex1 knockdown does not affect VEGF-mediated responses, demonstrating pathway-specific GEF function.","method":"siRNA knockdown, Rac activation assay, cell migration assay, in vitro tube formation assay","journal":"Molecular pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — clean knockdown with defined cellular phenotypes and pathway selectivity demonstrated","pmids":["20018810"],"is_preprint":false},{"year":2009,"finding":"Silencing P-Rex1 in metastatic prostate cancer PC-3 cells inhibits Rac activity and reduces cell migration and invasion; expression of recombinant P-Rex1 (but not its GEF-dead mutant) in non-metastatic CWR22Rv1 cells promotes Rac-dependent lamellipodia formation and lymph node metastasis in a mouse xenograft model.","method":"siRNA knockdown, GEF-dead mutant rescue, Rac activation assay, xenograft mouse model, lamellipodia imaging","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 — GEF-dead mutant establishes requirement for catalytic activity; in vivo xenograft with defined molecular phenotype","pmids":["19305425"],"is_preprint":false},{"year":2010,"finding":"P-Rex1 is activated downstream of ErbB receptors by dephosphorylation of inhibitory residues and phosphorylation of activating residues; the phosphorylation/dephosphorylation cycle regulates Rac activation, and P-Rex1 knockdown impairs breast cancer cell migration, invasion, and in vivo tumorigenic potential.","method":"Phosphorylation site mutagenesis, siRNA knockdown, Rac activation assay, cell migration and invasion assay, in vivo tumorigenesis assay","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 — phospho-site mutagenesis with functional readouts, single lab","pmids":["21042280"],"is_preprint":false},{"year":2010,"finding":"P-Rex1 is an essential mediator of ErbB receptor-driven Rac1 activation, cell motility, and tumorigenesis in breast cancer cells; its activation requires convergent inputs from ErbB receptors and a Gβγ/PI3Kγ-dependent pathway; CXCR4 is identified as a crucial co-activator of P-Rex1/Rac1 in response to ErbB ligands.","method":"siRNA knockdown, dominant-negative PI3Kγ, Rac1 activation assay, cell migration and invasion assay, in vivo tumor xenograft","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods, epistasis established via PI3Kγ and CXCR4 perturbation, in vivo confirmation","pmids":["21172654"],"is_preprint":false},{"year":2010,"finding":"P-Rex1 and Vav1 synergistically control fMLF-stimulated ROS formation, adhesion, chemotaxis, and Rac1/Rac2 activation in neutrophils; combined P-Rex1/Vav1 deficiency causes greater impairment than loss of either GEF family alone, establishing P-Rex1 and Vav1 as the major fMLFR-dependent Rac-GEFs in neutrophils.","method":"Compound knockout mouse (P-Rex1−/− and Vav1−/−), Rac activation assay, ROS measurement, chemotaxis and adhesion assays","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis via compound KO with multiple orthogonal readouts","pmids":["21178006"],"is_preprint":false},{"year":2011,"finding":"P-Rex1 loss in mice causes a melanoblast migration defect and P-Rex1−/− mice crossed to a melanoma model are resistant to metastasis; mechanistically, P-Rex1 drives invasion in a Rac-dependent manner.","method":"P-Rex1 knockout mouse, melanoma mouse model cross, invasion assay, Rac activation assay","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with in vivo metastasis phenotype and Rac-dependency established","pmids":["22109529"],"is_preprint":false},{"year":2011,"finding":"P-Rex1 promotes GLUT4 trafficking to the plasma membrane in adipocytes via PI3K- and Rac1-dependent actin remodeling and membrane ruffle formation; GEF activity is required and neither Cdc42 nor Rho substitutes.","method":"P-Rex1 overexpression and siRNA knockdown in 3T3-L1 adipocytes, GLUT4 trafficking assay, membrane ruffling imaging, dominant-negative Rac1, cytochalasin D treatment","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — GEF-dependent and Rac1-specific mechanism established with multiple functional readouts, single lab","pmids":["22002247"],"is_preprint":false},{"year":2011,"finding":"P-Rex1 is expressed in platelets and associates with Rac1 by co-immunoprecipitation, but P-Rex1−/− platelets respond normally to platelet agonists and activating surfaces, indicating P-Rex1 is not required for Rac1-mediated platelet activation.","method":"Co-immunoprecipitation, P-Rex1 knockout mouse, platelet spreading/aggregation assays","journal":"Journal of molecular signaling","confidence":"Medium","confidence_rationale":"Tier 2 — negative result confirmed by KO mouse and direct interaction shown by Co-IP","pmids":["21884615"],"is_preprint":false},{"year":2012,"finding":"PP1α binds P-Rex1 through an RVxF docking motif and directly activates P-Rex1 GEF activity in vitro independently of and additively to PIP3 and Gβγ; mass spectrometry identified Ser834, Ser1001, and Ser1165 as PP1α dephosphorylation sites; Ser1165Ala mutation activates P-Rex1 to a similar extent as PP1α.","method":"Co-immunoprecipitation, in vitro GEF assay with purified proteins, mass spectrometry of phosphorylation sites, site-directed mutagenesis","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with purified proteins, MS identification of sites, functional mutagenesis validation","pmids":["22242915"],"is_preprint":false},{"year":2012,"finding":"In zebrafish, Prex1 is a Nodal transcriptional target required for Nodal-dependent random endodermal cell motility and actin dynamics via Rac1; reducing Rac1 activity caused cells to bypass random migration and aberrantly contribute to mesoderm.","method":"Zebrafish transgenic reporter, morpholino knockdown of prex1, Rac1 inhibition, live imaging of actin dynamics","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis (Nodal→Prex1→Rac1) in zebrafish ortholog with live imaging, single lab","pmids":["22945937"],"is_preprint":false},{"year":2013,"finding":"PI3K inhibition in PIK3CA-mutant and HER2-amplified breast cancers suppresses Rac1/PAK/CRAF/MEK/ERK signaling via P-Rex1; constitutively active Rac1 blocks PI3Ki-induced ERK suppression and apoptosis, and P-Rex1 is the PIP3-dependent GEF mediating this pathway.","method":"Constitutively active Rac1 rescue, PI3K inhibitor treatment, ERK phosphorylation assay, apoptosis assay, in vivo tumor models","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — epistasis via constitutively active Rac1 rescue, multiple methods including in vivo","pmids":["24327733"],"is_preprint":false},{"year":2013,"finding":"P-Rex1 and PDGFRβ form a macromolecular complex; P-Rex1 expression drives invasion in a manner dependent on functional PDGFRβ, and siRNA of either P-Rex1 or PDGFRβ reduces invasiveness of WM852 melanoma cells.","method":"Co-immunoprecipitation, siRNA knockdown, 3D invasion assay","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 3 — Co-IP plus functional knockdown, single lab","pmids":["23382862"],"is_preprint":false},{"year":2014,"finding":"P-Rex1 directly acts as a GEF for RhoG in vitro and in GPCR-stimulated mouse neutrophils; loss of either P-Rex1 or RhoG causes equivalent reductions in GPCR-driven Rac activation and NADPH oxidase activity; RhoG loss impairs DOCK2 and F-actin recruitment to the leading edge, revealing a P-Rex1→RhoG→DOCK2→Rac hierarchy.","method":"In vitro GEF assay for RhoG, P-Rex1 and RhoG knockout neutrophils, DOCK2 localization by immunofluorescence, NADPH oxidase activity assay","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1–2 — in vitro GEF assay establishes direct substrate; genetic epistasis in primary neutrophils with multiple readouts","pmids":["24659802"],"is_preprint":false},{"year":2014,"finding":"P-Rex1 creates a positive feedback loop activating Rac1, PI3K/AKT, and MEK/ERK signaling independently of PTEN, and promotes insulin-like growth factor-1 receptor activation, suggesting P-Rex1 provides positive feedback to upstream PI3K activators.","method":"shRNA knockdown, Rac inhibition, P-Rex1 overexpression, phosphoproteomic analysis, PI3K inhibitor treatment in breast cancer cells","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 — multiple signaling readouts, mass spec confirmation, single lab","pmids":["25284585"],"is_preprint":false},{"year":2015,"finding":"The 1.95 Å crystal structure of the P-Rex1 DH-PH domain in complex with Rac1 was determined; mutations at the P-Rex1·Rac1 interface disrupted signaling downstream of RTKs and GPCRs; PIP3/Gβγ binding sites are on the opposite surface from the Rac1 interface, supporting a model where PIP3/Gβγ binding releases inhibitory C-terminal domains to expose the Rac1 binding site.","method":"X-ray crystallography (1.95 Å), interface mutagenesis, functional signaling assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with functional validation by mutagenesis","pmids":["26112412"],"is_preprint":false},{"year":2015,"finding":"P-Rex1 is required in the CA1 hippocampus for LTD via a PP1α-P-Rex1-Rac1 signaling pathway that regulates AMPA receptor endocytosis; P-Rex1 deletion or knockdown in CA1 impairs LTD and causes autism-like social behavior in mice.","method":"P-Rex1 genetic deletion and shRNA knockdown in CA1, electrophysiology (LTD), AMPA receptor endocytosis assay, behavioral tests","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 — genetic loss-of-function with defined synaptic and behavioral phenotype, pathway placement via PP1α-P-Rex1-Rac1","pmids":["26621702"],"is_preprint":false},{"year":2016,"finding":"Type I PKA regulatory subunit (RIα) interacts with P-Rex1 via its PDZ domains through the CNB-B domain of RIα; P-Rex1 activation localizes PKA to the cell periphery; PKA phosphorylates P-Rex1 at Ser-436 in its DEP1 domain, which inhibits the DH-PH catalytic cassette by direct interaction; the P-Rex1 S436A mutant shows increased RacGEF activity.","method":"Co-immunoprecipitation of endogenous proteins, site-directed mutagenesis, RacGEF activity assay, immunofluorescence, cell migration assay with S436A mutant","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 — endogenous Co-IP, mutagenesis with functional readout, mechanistic model of inhibitory phosphorylation confirmed","pmids":["26797121"],"is_preprint":false},{"year":2016,"finding":"PAKs (activated by Rac1 downstream of P-Rex1) phosphorylate P-Rex1 in a negative feedback loop downstream of RTK (neuregulin, IGF1) and GPCR activation, reducing P-Rex1 binding to PIP3 and GEF activity; PAK-mediated phosphorylation onset is delayed compared to AKT phosphorylation.","method":"PAK inhibitor treatment, PAK siRNA knockdown, P-Rex1 phosphorylation assays, PIP3-binding assay, GEF activity assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1–2 — in vitro and cell-based phosphorylation assays with functional readouts, single lab","pmids":["27481946"],"is_preprint":false},{"year":2016,"finding":"Norbin (Neurochondrin/NCDN), a GPCR-adaptor protein, directly binds P-Rex1 via its pleckstrin homology domain; direct interaction with Norbin increases basal, PIP3-, and Gβγ-stimulated P-Rex1 Rac-GEF activity; Norbin co-expression drives P-Rex1 translocation from cytosol to plasma membrane and promotes Rac1 activation and lamellipodia formation.","method":"Pulldown from mouse brain fractions, reciprocal Co-IP with purified proteins and in cells, GEF activity assay with purified proteins, PH domain mutagenesis, immunofluorescence and subcellular fractionation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — direct in vitro binding with purified proteins, GEF assay, domain mutagenesis, cell localization all in one study","pmids":["26792863"],"is_preprint":false},{"year":2016,"finding":"PKC (specifically PKCδ) directly phosphorylates P-Rex1 at Ser313, an inhibitory site that negatively regulates GEF exchange activity; activation of growth factor receptors phosphorylates Ser1169 through a PKC-independent mechanism; these multiple sites are regulated by distinct kinases.","method":"Kinase inhibitors, phospho-specific antibodies, PKCδ overexpression, site-directed mutagenesis (S313A), in vitro GEF assay","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 1–2 — PKCδ direct phosphorylation confirmed with mutagenesis and functional GEF assay, single lab","pmids":["27788493"],"is_preprint":false},{"year":2016,"finding":"ERK/MAPK signaling drives PREX1 overexpression in BRAF- and NRAS-mutant melanoma through both increased gene transcription and enhanced protein stability; PREX1-dependent invasion is mediated by RAC1 but not CDC42.","method":"ERK inhibitor treatment, siRNA knockdown, invasion assay, Rac1/Cdc42 activation assay, gene transcription analysis","journal":"Molecular cancer research : MCR","confidence":"Medium","confidence_rationale":"Tier 2 — pharmacological and genetic perturbation with GTPase-specific readouts, single lab","pmids":["27418645"],"is_preprint":false},{"year":2018,"finding":"GTPase-deficient GαqQL and Gα13QL form stable complexes with Gβγ that impair Gβγ interaction with P-Rex1; the N-terminal regions of Gαq and Gα13 are essential for sequestering Gβγ away from P-Rex1; Gβγ and AKT associate with SDF-1-stimulated P-Rex1; this mechanism prioritizes Gαq/Gα13→Rho signaling over Gβγ→P-Rex1→Rac signaling.","method":"Pulldown assays with constitutively active Gα mutants, chimeric Gα proteins, co-immunoprecipitation, DREADD-based chemogenetics, P-Rex1 Rac-GEF activity assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — pulldown, Co-IP, and chemogenetics with functional readout, single lab","pmids":["30446620"],"is_preprint":false},{"year":2018,"finding":"PKA regulatory subunit RIα directly activates P-Rex1 in vitro and promotes P-Rex1-mediated Rac activation and endothelial cell migration downstream of Gs-coupled EP2 receptors; RIα interacts with P-Rex1 PDZ1 domain via its CNB-B domain; this is distinct from catalytic Cα subunit, which phosphorylates and inhibits P-Rex1.","method":"In vitro P-Rex1 GEF assay with purified RIα, P-Rex1 siRNA knockdown, cAMP pulldown assay, cell migration assay, RIα mutant analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — direct in vitro activation with purified RIα, confirmed in cells with multiple methods","pmids":["30530493"],"is_preprint":false},{"year":2018,"finding":"GRK2 is required for TCR-induced CXCR4 phosphorylation at Ser-339, TCR-CXCR4 complex formation, and subsequent PREX1 membrane recruitment; TCR→GRK2→CXCR4→PI3Kγ→PREX1-Rac1 signaling stabilizes cytokine mRNAs and drives cytokine secretion in T cells.","method":"GRK2 siRNA, GRK2 inhibitor (paroxetine), CXCR4-Ser339 mutant analysis, PREX1 membrane recruitment assay, cytokine ELISA","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — pathway epistasis established by multiple genetic/pharmacological perturbations in primary T cells","pmids":["30018141"],"is_preprint":false},{"year":2019,"finding":"The 3.2 Å cryo-EM structure of the P-Rex1-Gβγ complex reveals that the C-terminal half of P-Rex1 adopts a fold similar to Legionella phosphoinositide phosphatases; this domain coalesces with a DEP domain and two PDZ domains to form an extensive Gβγ docking site; HDX-MS shows Gβγ binding induces allosteric changes; membrane localization is required for full activation.","method":"Cryo-EM (3.2 Å), hydrogen-deuterium exchange mass spectrometry, functional GEF assays","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structure with HDX-MS dynamics and functional validation","pmids":["31663027"],"is_preprint":false},{"year":2020,"finding":"The DEP1 domain of P-Rex1 autoinhibits GEF activity by interacting with the DH/PH domains in solution; the 3.1 Å crystal structure of DEP1 shows a domain-swap involving an exposed basic loop containing the PKA phosphorylation site; PKA phosphorylation of DEP1 does not affect activity or solution conformation of DH/PH-DEP1 in vitro but inhibits DEP1 binding to phosphatidic acid-containing liposomes, suggesting PKA hampers P-Rex1 membrane binding.","method":"X-ray crystallography (3.1 Å), in vitro GEF assay of DH/PH-DEP1 fragments, liposome binding assay, PKA phosphorylation of purified proteins","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — crystal structure plus in vitro functional assays with phosphomimetic analysis","pmids":["32661198"],"is_preprint":false},{"year":2020,"finding":"Small molecules targeting the P-Rex1 PH domain block PIP3 binding and inhibit fMLP-induced neutrophil spreading, Rac2 activation, and neutrophil recruitment in a zebrafish inflammation model, establishing the PH domain PIP3-binding site as a tractable drug target.","method":"Differential scanning fluorimetry screen, PIP3 binding competition assay, neutrophil Rac2 activation assay, zebrafish in vivo model","journal":"Molecular pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — biochemical binding assay plus functional cellular and in vivo validation, single lab","pmids":["31900312"],"is_preprint":false},{"year":2020,"finding":"P-Rex1 mediates glucose-stimulated Rac1 activation and insulin secretion in pancreatic β-cells; P-Rex1 knockdown attenuates glucose-induced Rac1 activation, Rac1 membrane association, and GSIS; RhoG knockdown does not affect GSIS, distinguishing the P-Rex1-dependent pathway.","method":"siRNA knockdown, Rac1 activation pulldown assay, membrane fractionation, GSIS ELISA","journal":"Cellular physiology and biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — clean knockdown with defined cellular and molecular phenotypes, single lab","pmids":["33347743"],"is_preprint":false},{"year":2021,"finding":"Gβγ activates P-Rex1 via two independent binding interfaces: Gβγ interacts with both the DH/PH domains and the PDZ-PDZ domains; the PDZ-PDZ/Gβγ interface mediates P-Rex1 recruitment to the plasma membrane while the DH/PH/Gβγ interface contributes to catalytic activation; C-terminal domain of P-Rex1 inhibits its catalytic activity.","method":"Pulldown assays with purified proteins, chimeric GEF (Q-Rhox) to separate recruitment from activation, plasma membrane localization imaging","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — chimeric protein approach to dissect interfaces, pulldown with purified proteins, single lab","pmids":["33412417"],"is_preprint":false},{"year":2023,"finding":"P-Rex1 is a novel substrate of the E3 ubiquitin ligase Malin (EPM2B); Malin ubiquitinates P-Rex1, linking P-Rex1 to the laforin-Malin complex associated with Lafora disease and altered glucose uptake.","method":"Unbiased ubiquitination substrate screen using Malin E3 ligase activity, protein-protein interaction assays","journal":"Neurobiology of disease","confidence":"Medium","confidence_rationale":"Tier 2 — activity-based substrate identification for ubiquitin ligase, single lab","pmids":["36638890"],"is_preprint":false},{"year":2023,"finding":"NRBP1 (a pseudokinase) binds P-Rex1 and acts as a scaffold to enhance GTP-bound Rac1 and Cdc42 levels in a P-Rex1-dependent manner; NRBP1-mediated cell migration and invasion in triple-negative breast cancer requires P-Rex1; constitutively active Rac1 rescues NRBP1 knockdown effects.","method":"BioID/MS pulldown, siRNA knockdown, constitutively active Rac1 rescue, Rac1/Cdc42 activation assay, migration/invasion assay","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 — BioID identifies interaction, knockdown epistasis with rescue confirms pathway, single lab","pmids":["36693952"],"is_preprint":false},{"year":2024,"finding":"Cryo-EM structure of P-Rex1 bound to IP4 (at 3.2 Å resolution) reveals an autoinhibited conformation where the PH domain occludes the active site of the DH domain, stabilized by DH-DEP1 and PH-4HB subdomain interactions; disrupting these interfaces activates P-Rex1 in cells during chemokine-induced migration; PIP3-containing liposomes disrupt these interfaces, providing the mechanism of PIP3-mediated activation.","method":"Cryo-EM, HDX-MS, in vitro GEF assay with interface mutants, cell migration assay with full-length P-Rex1 interface variants, liposome binding","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structure plus HDX-MS plus interface mutagenesis validated in living cells, multiple orthogonal methods","pmids":["39082940"],"is_preprint":false},{"year":2025,"finding":"P-Rex1 limits hepatocyte glucose uptake and mitochondrial function (membrane potential, ATP production, morphology) independently of its Rac-GEF catalytic activity; P-Rex1 controls Glut2 surface levels and Gpr21 (an orphan inhibitory GPCR) trafficking at the plasma membrane; a catalytically inactive Prex1GD knock-in mouse recapitulates the glucose clearance phenotype of Prex1−/− mice.","method":"Prex1−/− and catalytically inactive Prex1GD knock-in mice, high-fat diet model, cell fractionation, Glut2 surface assay, mitochondrial function assays, Gpr21 trafficking analysis","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — catalytically dead knock-in mouse distinguishes GEF-independent function, multiple orthogonal readouts","pmids":["41046518"],"is_preprint":false},{"year":2025,"finding":"P-Rex1 limits the agonist-induced internalization of GPCRs (S1PR1, CXCR4, PAR4, GLP1R) but not RTKs (PDGFR, EGFR) independently of its Rac-GEF activity, through its PDZ, DEP, and IP4P domains; P-Rex1 binds GRK2 directly in vitro and in cells and blocks GRK2-mediated phosphorylation required for GPCR internalization.","method":"CRISPR-Cas9 P-Rex1 KO, catalytically inactive P-Rex1 mutant, GPCR internalization assay, GRK2 binding assay in vitro and in cells, phosphorylation assay","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — catalytically dead mutant distinguishes adaptor from GEF function; direct GRK2 binding confirmed in vitro and in cells; multiple GPCRs tested","pmids":["41100251"],"is_preprint":false},{"year":2025,"finding":"P-Rex1 mediates neutrophil phagocytosis of IgG-opsonized zymosan and bacterial killing independently of its Rac-GEF activity; P-Rex1 is required for Fc receptor-dependent Rac and Syk activation; in contrast, P-Rex1-mediated migration, ROS, and NET formation require its catalytic GEF activity.","method":"Prex1−/− and catalytically inactive Prex1GD mice, phagocytosis assay, bactericidal assay, Rac activation assay, Syk activation assay","journal":"Frontiers in immunology","confidence":"High","confidence_rationale":"Tier 2 — catalytically dead knock-in mouse cleanly dissects GEF-dependent from GEF-independent functions across multiple assays","pmids":["41098722"],"is_preprint":false},{"year":2009,"finding":"P-Rex1 PDZ domains interact directly with the S1P1 receptor carboxyl-terminal tail; P-Rex1 co-expression diminishes S1P1 trafficking to intracellular compartments (maintains receptor at cell surface); cells transfected with P-Rex1 PDZ domains show increased migratory response to S1P.","method":"Co-immunoprecipitation, PDZ domain-S1P1 tail binding assay, S1P1 internalization assay, cell migration assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 3 — Co-IP and internalization assay, single lab, no in vitro reconstitution","pmids":["20036214"],"is_preprint":false}],"current_model":"P-Rex1 is a multi-domain Rac guanine-nucleotide exchange factor that is held in an autoinhibited state (PH domain occluding the DH active site, stabilized by DEP1-DH and PH-4HB interactions) and is synergistically activated at the plasma membrane by direct binding of PIP3 (to the PH domain) and Gβγ subunits (to a composite site formed by the DEP-PDZ-IP4P module); activation is positively regulated by PP1α-mediated dephosphorylation of Ser1165 and by the adaptor Norbin, and negatively regulated by PKA-mediated phosphorylation (principally at Ser436/DEP1, impairing membrane binding, and at additional sites via a PAK feedback loop), by inositol phosphates such as IP4 that stabilize the autoinhibited conformation, and by sequestration of Gβγ by active Gαq/Gα13; beyond its catalytic GEF role—which drives Rac1/Rac2/RhoG activation to control NADPH oxidase activity, cell migration, metastasis, GLUT4 trafficking, LTD, and insulin secretion—P-Rex1 also performs GEF-independent adaptor functions including limiting GPCR internalization through GRK2 binding and controlling hepatocyte Gpr21 trafficking to regulate glucose uptake and mitochondrial metabolism."},"narrative":{"teleology":[{"year":2002,"claim":"The discovery of P-Rex1 as a Rac-GEF synergistically activated by PIP3 and Gβγ established the concept of a coincidence detector linking PI3K and heterotrimeric G protein signaling to Rac activation in neutrophils.","evidence":"Biochemical purification from neutrophil cytosol with reconstituted in vitro GEF assays","pmids":["11955434"],"confidence":"High","gaps":["Structural basis for synergistic activation unknown","Substrate specificity among Rac isoforms untested","In vivo relevance unconfirmed"]},{"year":2005,"claim":"Genetic knockout and Gβγ subunit specificity studies established that P-Rex1 preferentially activates Rac2 in neutrophils, is essential for GPCR-driven ROS and chemotaxis in vivo, and is regulated by specific Gβ1–4 subunits and inhibitory PKA phosphorylation.","evidence":"P-Rex1 KO mouse neutrophils, in vitro GEF assays with a panel of Gβγ combinations, PKA phosphorylation kinetics","pmids":["16243036","16243035","16301320","16301321"],"confidence":"High","gaps":["Phosphorylation sites responsible for PKA inhibition unidentified","Domain requirements for Gβγ binding unknown","Roles beyond neutrophils unexplored"]},{"year":2007,"claim":"Demonstration that PIP3 and Gβγ synergistically drive P-Rex1 membrane translocation via the DH/PH tandem, and that endogenous P-Rex1 localizes to the neutrophil leading edge, connected the biochemical activation mechanism to spatial regulation during chemotaxis.","evidence":"Subcellular fractionation of Sf9 cells with domain mutants; immunofluorescence of polarized human neutrophils","pmids":["17698854","17227822"],"confidence":"High","gaps":["Molecular contacts between P-Rex1 and the membrane undefined","Role of C-terminal domains in translocation unclear"]},{"year":2008,"claim":"Identification of intramolecular interactions between the DEP2/PDZ1 and IP4P domains, and their disruption by PKA phosphorylation, revealed the first intramolecular regulatory mechanism controlling Gβγ responsiveness.","evidence":"Immunoprecipitation of truncated P-Rex1 fragments, alanine mutagenesis, in vitro GEF assay","pmids":["18514484"],"confidence":"Medium","gaps":["Specific PKA site(s) mediating the effect unidentified","No structural model of the full-length autoinhibited state"]},{"year":2009,"claim":"Extension of P-Rex1 function beyond innate immunity to neuronal morphogenesis (neurite outgrowth via Rac3), endothelial CXCR4/SDF-1 signaling, and prostate cancer metastasis broadened the biological scope of this GEF.","evidence":"GEF-dead mutant analysis in PC12 cells/hippocampal neurons; siRNA in endothelial cells; xenograft metastasis model with GEF-dead rescue","pmids":["18697831","20018810","19305425"],"confidence":"High","gaps":["Whether P-Rex1 activates Rac3 directly in vitro not tested","Role in human tumor progression not validated clinically"]},{"year":2010,"claim":"Convergent ErbB receptor and Gβγ/PI3Kγ signaling through P-Rex1/Rac1 was shown to drive breast cancer cell motility and tumorigenesis, while compound P-Rex1/Vav1 KO established functional synergy between major Rac-GEF families in neutrophils.","evidence":"siRNA, dominant-negative PI3Kγ, CXCR4 epistasis in breast cancer cells; compound P-Rex1/Vav1 KO mouse neutrophils","pmids":["21172654","21178006","21042280"],"confidence":"High","gaps":["Direct physical interaction between ErbB receptors and P-Rex1 not shown","Phosphorylation code for activating versus inhibitory sites incompletely mapped"]},{"year":2012,"claim":"PP1α was identified as a direct activator of P-Rex1 via dephosphorylation of Ser1165, acting independently of and additively to PIP3 and Gβγ, establishing a third regulatory input.","evidence":"In vitro GEF assay with purified PP1α, mass spectrometry of dephosphorylation sites, S1165A mutagenesis","pmids":["22242915"],"confidence":"High","gaps":["Kinase responsible for Ser1165 phosphorylation not identified","In vivo relevance of PP1α-P-Rex1 axis in neutrophils untested at this point"]},{"year":2014,"claim":"Discovery that P-Rex1 directly activates RhoG, which in turn recruits DOCK2 to amplify Rac signaling, revealed a GTPase relay (P-Rex1→RhoG→DOCK2→Rac) controlling NADPH oxidase activity and leading-edge polarity.","evidence":"In vitro GEF assay for RhoG; P-Rex1 and RhoG KO neutrophils; DOCK2 localization by immunofluorescence","pmids":["24659802"],"confidence":"High","gaps":["Structural basis of RhoG recognition by P-Rex1 unknown","Whether this relay operates in non-neutrophil contexts untested"]},{"year":2015,"claim":"Crystal structure of the DH-PH/Rac1 complex at 1.95 Å showed that PIP3/Gβγ binding surfaces are on the opposite face from the Rac1 interface, supporting a model where activator binding relieves C-terminal domain occlusion of the active site.","evidence":"X-ray crystallography, interface mutagenesis with functional signaling readouts","pmids":["26112412"],"confidence":"High","gaps":["Full-length autoinhibited structure not yet available","Mechanism of C-terminal domain relief still inferential"]},{"year":2015,"claim":"P-Rex1 was placed in a PP1α→P-Rex1→Rac1 pathway controlling AMPA receptor endocytosis and LTD in hippocampal CA1 neurons, and P-Rex1 deletion caused autism-like social behavior in mice.","evidence":"P-Rex1 KO and shRNA in CA1, electrophysiology, AMPA receptor endocytosis assay, behavioral testing","pmids":["26621702"],"confidence":"Medium","gaps":["Whether Rac2 or RhoG participates in neuronal context unknown","Behavioral phenotype assessed in single lab"]},{"year":2016,"claim":"Multiple regulatory phosphorylation inputs were mapped: PKA targets Ser436 in DEP1 to impair membrane binding, PKCδ targets Ser313 for inhibition, and a PAK-mediated negative feedback loop reduces PIP3 binding; meanwhile Norbin was identified as a direct PH-domain-binding activator promoting membrane translocation.","evidence":"Site-directed mutagenesis, in vitro GEF assays, endogenous Co-IP, PAK inhibitor studies, purified Norbin binding and GEF assay","pmids":["26797121","27481946","27788493","26792863"],"confidence":"High","gaps":["Relative contributions of each phosphosite in vivo unknown","Norbin-P-Rex1 structure not determined"]},{"year":2019,"claim":"Cryo-EM structure of the P-Rex1–Gβγ complex at 3.2 Å revealed that the C-terminal IP4P-like domain, DEP, and two PDZ domains form an extensive composite Gβγ docking site, and HDX-MS showed that Gβγ binding induces allosteric conformational changes propagated to the catalytic domain.","evidence":"Cryo-EM, hydrogen-deuterium exchange mass spectrometry, functional GEF assays","pmids":["31663027"],"confidence":"High","gaps":["PIP3-bound activation structure not captured","Dynamics of autoinhibition release not resolved temporally"]},{"year":2020,"claim":"The DEP1 domain crystal structure and liposome binding experiments showed that PKA phosphorylation of DEP1 impairs membrane association rather than directly modulating catalytic activity, redefining the PKA inhibitory mechanism as membrane-targeting disruption.","evidence":"X-ray crystallography of DEP1, liposome binding assay, in vitro GEF assay of DH/PH-DEP1 fragments","pmids":["32661198"],"confidence":"High","gaps":["Effect in the context of full-length membrane-bound P-Rex1 not tested structurally"]},{"year":2024,"claim":"The cryo-EM structure of autoinhibited P-Rex1 bound to IP4 revealed that the PH domain occludes the DH active site, stabilized by DEP1–DH and PH–4HB contacts; disruption of these interfaces activated P-Rex1 in cells and PIP3-containing liposomes broke these contacts, providing the complete autoinhibition-to-activation mechanism.","evidence":"Cryo-EM at 3.2 Å, HDX-MS, interface mutagenesis validated by cell migration assay and liposome binding","pmids":["39082940"],"confidence":"High","gaps":["Structure of fully PIP3/Gβγ-activated membrane-bound P-Rex1 not captured","How IP4 stabilizes vs. merely marks the autoinhibited state unclear"]},{"year":2025,"claim":"Catalytically inactive Prex1 knock-in mice revealed that P-Rex1 performs GEF-independent adaptor functions: it limits GPCR internalization by binding and blocking GRK2, controls hepatocyte glucose metabolism and Gpr21 trafficking, and mediates Fc receptor-dependent phagocytosis — all independent of Rac exchange activity.","evidence":"Catalytically dead Prex1GD knock-in and Prex1 KO mice, GPCR internalization assays across multiple receptors, in vitro GRK2 binding, phagocytosis and bactericidal assays","pmids":["41100251","41046518","41098722"],"confidence":"High","gaps":["Structural basis of GRK2 interaction unknown","Whether adaptor functions require specific domain contacts beyond PDZ/DEP/IP4P not mapped","Relative physiological importance of GEF vs. adaptor functions in vivo unquantified"]},{"year":null,"claim":"A full structural picture of P-Rex1 activation on the membrane — capturing simultaneous PIP3, Gβγ, and Norbin engagement in the context of the lipid bilayer — remains unresolved, as does the in vivo phosphorylation code integrating PKA, PKC, PAK, and PP1α inputs.","evidence":"","pmids":[],"confidence":"High","gaps":["No structure of fully activated membrane-bound P-Rex1","Quantitative integration of multiple phosphorylation inputs in vivo unknown","Physiological contexts requiring GEF-independent adaptor functions versus catalytic functions incompletely delineated"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[42,43,44]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,2,22,24]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,5,7]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[5,7,28,41]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[2,3,14,22,44]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,13,20,26]},{"term_id":"R-HSA-1500931","term_label":"Cell-Cell communication","supporting_discovery_ids":[10,11,15,30]}],"complexes":[],"partners":["GNB1","GNG2","PPP1CA","NCDN","GRK2","PRKAR1A","NRBP1","MTOR"],"other_free_text":[]},"mechanistic_narrative":"PREX1 encodes P-Rex1, a multidomain Rac guanine-nucleotide exchange factor (GEF) that functions as a coincidence detector for PIP3 and Gβγ signaling, integrating PI3K and GPCR inputs to activate Rac GTPases and drive neutrophil chemotaxis, ROS production, cell migration, and metastasis [PMID:11955434, PMID:16243035, PMID:22109529]. Structural studies reveal that P-Rex1 is held in an autoinhibited conformation wherein the PH domain occludes the DH catalytic site, stabilized by DEP1–DH and PH–4HB interactions; PIP3 binding to the PH domain and Gβγ engagement of a composite DEP–PDZ–IP4P surface relieve this autoinhibition, while PKA phosphorylation of Ser436 in DEP1 impairs membrane association and PP1α-mediated dephosphorylation of Ser1165 activates GEF output [PMID:39082940, PMID:31663027, PMID:26797121, PMID:22242915]. Beyond its catalytic role activating Rac1, Rac2, and RhoG in neutrophils, neurons, endothelial cells, adipocytes, and cancer cells [PMID:24659802, PMID:26621702, PMID:22002247], P-Rex1 performs GEF-independent adaptor functions: it directly binds GRK2 to limit GPCR internalization, controls hepatocyte Gpr21 trafficking and glucose metabolism, and mediates Fc receptor–dependent phagocytosis independently of its catalytic activity [PMID:41100251, PMID:41046518, PMID:41098722]."},"prefetch_data":{"uniprot":{"accession":"Q8TCU6","full_name":"Phosphatidylinositol 3,4,5-trisphosphate-dependent Rac exchanger 1 protein","aliases":[],"length_aa":1659,"mass_kda":186.2,"function":"Functions as a RAC guanine nucleotide exchange factor (GEF), which activates the Rac proteins by exchanging bound GDP for free GTP. Its activity is synergistically activated by phosphatidylinositol 3,4,5-trisphosphate and the beta gamma subunits of heterotrimeric G protein. May function downstream of heterotrimeric G proteins in neutrophils","subcellular_location":"Cytoplasm, cytosol; Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q8TCU6/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PREX1","classification":"Not Classified","n_dependent_lines":23,"n_total_lines":1208,"dependency_fraction":0.01903973509933775},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PREX1","total_profiled":1310},"omim":[{"mim_id":"612139","title":"PHOSPHATIDYLINOSITOL 3,4,5-TRISPHOSPHATE-DEPENDENT RAC EXCHANGER 2; PREX2","url":"https://www.omim.org/entry/612139"},{"mim_id":"606905","title":"PHOSPHATIDYLINOSITOL 3,4,5-TRISPHOSPHATE-DEPENDENT RAC EXCHANGER 1; PREX1","url":"https://www.omim.org/entry/606905"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Vesicles","reliability":"Supported"},{"location":"Cytosol","reliability":"Supported"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"bone marrow","ntpm":49.6}],"url":"https://www.proteinatlas.org/search/PREX1"},"hgnc":{"alias_symbol":["KIAA1415","P-REX1"],"prev_symbol":[]},"alphafold":{"accession":"Q8TCU6","domains":[{"cath_id":"1.20.900.10","chopping":"39-250","consensus_level":"high","plddt":91.7606,"start":39,"end":250},{"cath_id":"2.30.29.30","chopping":"260-306_324-397","consensus_level":"high","plddt":89.1245,"start":260,"end":397},{"cath_id":"1.10.10.10","chopping":"423-495","consensus_level":"high","plddt":83.2385,"start":423,"end":495},{"cath_id":"1.10.10.10","chopping":"540-554_561-612","consensus_level":"medium","plddt":84.0321,"start":540,"end":612},{"cath_id":"2.30.42.10","chopping":"624-707","consensus_level":"medium","plddt":91.8014,"start":624,"end":707},{"cath_id":"2.30.42.10","chopping":"709-802_840-848","consensus_level":"medium","plddt":87.9031,"start":709,"end":848}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8TCU6","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8TCU6-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8TCU6-F1-predicted_aligned_error_v6.png","plddt_mean":78.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PREX1","jax_strain_url":"https://www.jax.org/strain/search?query=PREX1"},"sequence":{"accession":"Q8TCU6","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8TCU6.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8TCU6/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8TCU6"}},"corpus_meta":[{"pmid":"11955434","id":"PMC_11955434","title":"P-Rex1, a PtdIns(3,4,5)P3- and Gbetagamma-regulated guanine-nucleotide exchange factor for Rac.","date":"2002","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/11955434","citation_count":445,"is_preprint":false},{"pmid":"24327733","id":"PMC_24327733","title":"PI3K regulates MEK/ERK signaling in breast cancer via the Rac-GEF, P-Rex1.","date":"2013","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/24327733","citation_count":180,"is_preprint":false},{"pmid":"21172654","id":"PMC_21172654","title":"Identification of the Rac-GEF P-Rex1 as an essential mediator of ErbB signaling in breast cancer.","date":"2010","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/21172654","citation_count":170,"is_preprint":false},{"pmid":"22109529","id":"PMC_22109529","title":"P-Rex1 is required for efficient melanoblast migration and melanoma metastasis.","date":"2011","source":"Nature 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mouse neutrophils.","date":"2005","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/16243036","citation_count":109,"is_preprint":false},{"pmid":"15858067","id":"PMC_15858067","title":"Involvement of a Rac activator,P-Rex1, in neurotrophin-derived signaling and neuronal migration.","date":"2005","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/15858067","citation_count":97,"is_preprint":false},{"pmid":"21042280","id":"PMC_21042280","title":"P-Rex1 participates in Neuregulin-ErbB signal transduction and its expression correlates with patient outcome in breast cancer.","date":"2010","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/21042280","citation_count":80,"is_preprint":false},{"pmid":"25284585","id":"PMC_25284585","title":"P-REX1 creates a positive feedback loop to activate growth factor receptor, PI3K/AKT and MEK/ERK signaling in breast 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novel Rac1-guanine nucleotide exchange factor (GEF) that promotes actin remodeling and GLUT4 protein trafficking in adipocytes.","date":"2011","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22002247","citation_count":57,"is_preprint":false},{"pmid":"26112412","id":"PMC_26112412","title":"The Phosphatidylinositol (3,4,5)-Trisphosphate-dependent Rac Exchanger 1·Ras-related C3 Botulinum Toxin Substrate 1 (P-Rex1·Rac1) Complex Reveals the Basis of Rac1 Activation in Breast Cancer Cells.","date":"2015","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/26112412","citation_count":51,"is_preprint":false},{"pmid":"26923603","id":"PMC_26923603","title":"P-Rex1 Promotes Resistance to VEGF/VEGFR-Targeted Therapy in Prostate Cancer.","date":"2016","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/26923603","citation_count":51,"is_preprint":false},{"pmid":"22945937","id":"PMC_22945937","title":"Nodal signaling regulates endodermal cell motility and actin dynamics via Rac1 and Prex1.","date":"2012","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/22945937","citation_count":47,"is_preprint":false},{"pmid":"16301320","id":"PMC_16301320","title":"Phosphorylation of P-Rex1 by the cyclic AMP-dependent protein kinase inhibits the phosphatidylinositiol (3,4,5)-trisphosphate and Gbetagamma-mediated regulation of its activity.","date":"2005","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16301320","citation_count":47,"is_preprint":false},{"pmid":"17227822","id":"PMC_17227822","title":"Signaling requirements for translocation of P-Rex1, a key Rac2 exchange factor involved in chemoattractant-stimulated human neutrophil function.","date":"2007","source":"Journal of leukocyte biology","url":"https://pubmed.ncbi.nlm.nih.gov/17227822","citation_count":44,"is_preprint":false},{"pmid":"18697831","id":"PMC_18697831","title":"P-Rex1 - a 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purification from neutrophil cytosol, in vitro GEF assay, antisense oligonucleotide knockdown, recombinant protein expression\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro GEF assay with purified components, replicated across multiple methods in foundational paper\",\n      \"pmids\": [\"11955434\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"PKA phosphorylates P-Rex1, inhibiting its PIP3- and Gβγ-stimulated GEF activity; Gβγ is 47-fold less potent in activating phosphorylated versus dephosphorylated P-Rex1, and PKA activation in HEK293T cells reduces GTP-bound Rac levels.\",\n      \"method\": \"In vitro GEF assay with purified proteins, 32P-labeling in HEK293T cells, pharmacological activation of PKA\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with quantitative kinetics, confirmed in cells with multiple reagents\",\n      \"pmids\": [\"16301320\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"P-Rex1 acts as a primary GEF for Rac2 (but not Rac1) in mouse neutrophils; P-Rex1 shows higher affinity for dominant-negative Rac2(S17N) than Rac1(S17N) by co-immunoprecipitation; P-Rex1 knockout impairs fMLP-induced Rac2 activation, F-actin formation, superoxide production, and chemotaxis.\",\n      \"method\": \"P-Rex1 knockout mouse, co-immunoprecipitation with Rac2(S17N) vs. Rac1(S17N), Rac activation assay, chemotaxis assay\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with defined cellular phenotype and substrate preference confirmed by differential pulldown\",\n      \"pmids\": [\"16243036\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"P-Rex1 knockout mice display impaired GPCR-dependent Rac2 activation, absent LPS-primed ROS formation, and defective recruitment of neutrophils to inflammatory sites, establishing P-Rex1 as a key regulator of a subset of Rac-dependent neutrophil responses downstream of GPCRs.\",\n      \"method\": \"P-Rex1 knockout mouse, Rac activation assay, ROS measurement, in vivo inflammatory recruitment assay, chemotaxis assay\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with multiple defined cellular phenotypes, independently replicated\",\n      \"pmids\": [\"16243035\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Gβγ dimers composed of Gβ1–4 (but not Gβ5) paired with γ2 activate P-Rex1; the farnesylated γ11 subunit and Gβ1γ12 are less effective activators; Gα subunits (Gs, Gi, Gq, G12, G13) activated by AlF4- cannot activate P-Rex1, demonstrating subunit-specific regulation.\",\n      \"method\": \"In vitro GEF assay with purified recombinant G protein subunits reconstituted in synthetic lipid vesicles\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro with pure components across a panel of subunits\",\n      \"pmids\": [\"16301321\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Membrane translocation of P-Rex1 requires both Gβγ and PI3K (PIP3) synergistically; neither alone causes significant translocation. The DH/PH domain tandem is sufficient for this synergistic membrane localization, GEF activity is not required for translocation, and membrane-derived P-Rex1 has higher basal GEF activity than cytosol-derived P-Rex1.\",\n      \"method\": \"Subcellular fractionation of Sf9 cells co-expressing P-Rex1 with Gβγ and/or PI3K; P-Rex1 domain mutant analysis; in vitro Rac2-GEF activity assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — systematic domain mutant analysis combined with biochemical fractionation and in vitro GEF assay\",\n      \"pmids\": [\"17698854\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"P-Rex1 and P-Rex2 interact with mTOR through their tandem DEP domains; P-Rex1 associates with both mTORC1 and mTORC2 but is only active in the mTORC2 complex; dominant-negative P-Rex1 and shRNA knockdown reduce mTOR/mTORC2-dependent Rac activation and cell migration.\",\n      \"method\": \"Co-immunoprecipitation, dominant-negative constructs, shRNA knockdown, Rac activation assay, cell migration assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — single lab, Co-IP plus functional knockdown, but mechanistic model not fully reconstituted\",\n      \"pmids\": [\"17565979\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Endogenous P-Rex1 translocates from cytoplasm to the leading edge of polarized human neutrophils in a Gβγ- and PIP3-dependent manner upon chemoattractant stimulation, where it co-localizes with F-actin and Rac2; PKA activation inhibits P-Rex1 translocation.\",\n      \"method\": \"Immunofluorescence microscopy of human neutrophils, pharmacological inhibitors of PI3K and Gβγ, PKA activation\",\n      \"journal\": \"Journal of leukocyte biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization experiment with functional consequence, single lab\",\n      \"pmids\": [\"17227822\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The second DEP and first PDZ domains of P-Rex1 associate with its IP4P domain; this domain-domain interaction is essential for Gβγ-induced activation and PKA-induced inhibition. PKA phosphorylation prevents domain-domain interaction and Gβγ binding, revealing an intramolecular regulatory mechanism.\",\n      \"method\": \"Immunoprecipitation of truncated P-Rex1 mutants, in vitro GEF assay, PAK1/2 phosphorylation assay, alanine-substitution mutagenesis\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro GEF assay plus mutagenesis, single lab\",\n      \"pmids\": [\"18514484\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"P-Rex1 localizes to the distal tips of developing neurites and axonal growth cones in PC12 cells and hippocampal neurons; P-Rex1 activates Rac3 in neuronal cells; P-Rex1 expression inhibits NGF-stimulated neurite differentiation through its GEF activity, while P-Rex1 knockdown promotes neurite hyper-elongation with decreased F-actin at the growth cone.\",\n      \"method\": \"Immunofluorescence in PC12 cells and hippocampal neurons, GEF-dead mutant analysis, RNAi knockdown, cytochalasin D rescue, Rac3 GTPase activity assay\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization plus functional GEF-dead rescue analysis, single lab\",\n      \"pmids\": [\"18697831\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"P-Rex1 is required for SDF-1/CXCL12-stimulated Rac activation, endothelial cell migration, and in vitro angiogenesis via the CXCR4/Gβγ/PI3K pathway; P-Rex1 knockdown does not affect VEGF-mediated responses, demonstrating pathway-specific GEF function.\",\n      \"method\": \"siRNA knockdown, Rac activation assay, cell migration assay, in vitro tube formation assay\",\n      \"journal\": \"Molecular pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean knockdown with defined cellular phenotypes and pathway selectivity demonstrated\",\n      \"pmids\": [\"20018810\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Silencing P-Rex1 in metastatic prostate cancer PC-3 cells inhibits Rac activity and reduces cell migration and invasion; expression of recombinant P-Rex1 (but not its GEF-dead mutant) in non-metastatic CWR22Rv1 cells promotes Rac-dependent lamellipodia formation and lymph node metastasis in a mouse xenograft model.\",\n      \"method\": \"siRNA knockdown, GEF-dead mutant rescue, Rac activation assay, xenograft mouse model, lamellipodia imaging\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — GEF-dead mutant establishes requirement for catalytic activity; in vivo xenograft with defined molecular phenotype\",\n      \"pmids\": [\"19305425\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"P-Rex1 is activated downstream of ErbB receptors by dephosphorylation of inhibitory residues and phosphorylation of activating residues; the phosphorylation/dephosphorylation cycle regulates Rac activation, and P-Rex1 knockdown impairs breast cancer cell migration, invasion, and in vivo tumorigenic potential.\",\n      \"method\": \"Phosphorylation site mutagenesis, siRNA knockdown, Rac activation assay, cell migration and invasion assay, in vivo tumorigenesis assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — phospho-site mutagenesis with functional readouts, single lab\",\n      \"pmids\": [\"21042280\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"P-Rex1 is an essential mediator of ErbB receptor-driven Rac1 activation, cell motility, and tumorigenesis in breast cancer cells; its activation requires convergent inputs from ErbB receptors and a Gβγ/PI3Kγ-dependent pathway; CXCR4 is identified as a crucial co-activator of P-Rex1/Rac1 in response to ErbB ligands.\",\n      \"method\": \"siRNA knockdown, dominant-negative PI3Kγ, Rac1 activation assay, cell migration and invasion assay, in vivo tumor xenograft\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods, epistasis established via PI3Kγ and CXCR4 perturbation, in vivo confirmation\",\n      \"pmids\": [\"21172654\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"P-Rex1 and Vav1 synergistically control fMLF-stimulated ROS formation, adhesion, chemotaxis, and Rac1/Rac2 activation in neutrophils; combined P-Rex1/Vav1 deficiency causes greater impairment than loss of either GEF family alone, establishing P-Rex1 and Vav1 as the major fMLFR-dependent Rac-GEFs in neutrophils.\",\n      \"method\": \"Compound knockout mouse (P-Rex1−/− and Vav1−/−), Rac activation assay, ROS measurement, chemotaxis and adhesion assays\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis via compound KO with multiple orthogonal readouts\",\n      \"pmids\": [\"21178006\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"P-Rex1 loss in mice causes a melanoblast migration defect and P-Rex1−/− mice crossed to a melanoma model are resistant to metastasis; mechanistically, P-Rex1 drives invasion in a Rac-dependent manner.\",\n      \"method\": \"P-Rex1 knockout mouse, melanoma mouse model cross, invasion assay, Rac activation assay\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with in vivo metastasis phenotype and Rac-dependency established\",\n      \"pmids\": [\"22109529\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"P-Rex1 promotes GLUT4 trafficking to the plasma membrane in adipocytes via PI3K- and Rac1-dependent actin remodeling and membrane ruffle formation; GEF activity is required and neither Cdc42 nor Rho substitutes.\",\n      \"method\": \"P-Rex1 overexpression and siRNA knockdown in 3T3-L1 adipocytes, GLUT4 trafficking assay, membrane ruffling imaging, dominant-negative Rac1, cytochalasin D treatment\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — GEF-dependent and Rac1-specific mechanism established with multiple functional readouts, single lab\",\n      \"pmids\": [\"22002247\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"P-Rex1 is expressed in platelets and associates with Rac1 by co-immunoprecipitation, but P-Rex1−/− platelets respond normally to platelet agonists and activating surfaces, indicating P-Rex1 is not required for Rac1-mediated platelet activation.\",\n      \"method\": \"Co-immunoprecipitation, P-Rex1 knockout mouse, platelet spreading/aggregation assays\",\n      \"journal\": \"Journal of molecular signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — negative result confirmed by KO mouse and direct interaction shown by Co-IP\",\n      \"pmids\": [\"21884615\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PP1α binds P-Rex1 through an RVxF docking motif and directly activates P-Rex1 GEF activity in vitro independently of and additively to PIP3 and Gβγ; mass spectrometry identified Ser834, Ser1001, and Ser1165 as PP1α dephosphorylation sites; Ser1165Ala mutation activates P-Rex1 to a similar extent as PP1α.\",\n      \"method\": \"Co-immunoprecipitation, in vitro GEF assay with purified proteins, mass spectrometry of phosphorylation sites, site-directed mutagenesis\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with purified proteins, MS identification of sites, functional mutagenesis validation\",\n      \"pmids\": [\"22242915\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"In zebrafish, Prex1 is a Nodal transcriptional target required for Nodal-dependent random endodermal cell motility and actin dynamics via Rac1; reducing Rac1 activity caused cells to bypass random migration and aberrantly contribute to mesoderm.\",\n      \"method\": \"Zebrafish transgenic reporter, morpholino knockdown of prex1, Rac1 inhibition, live imaging of actin dynamics\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis (Nodal→Prex1→Rac1) in zebrafish ortholog with live imaging, single lab\",\n      \"pmids\": [\"22945937\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PI3K inhibition in PIK3CA-mutant and HER2-amplified breast cancers suppresses Rac1/PAK/CRAF/MEK/ERK signaling via P-Rex1; constitutively active Rac1 blocks PI3Ki-induced ERK suppression and apoptosis, and P-Rex1 is the PIP3-dependent GEF mediating this pathway.\",\n      \"method\": \"Constitutively active Rac1 rescue, PI3K inhibitor treatment, ERK phosphorylation assay, apoptosis assay, in vivo tumor models\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — epistasis via constitutively active Rac1 rescue, multiple methods including in vivo\",\n      \"pmids\": [\"24327733\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"P-Rex1 and PDGFRβ form a macromolecular complex; P-Rex1 expression drives invasion in a manner dependent on functional PDGFRβ, and siRNA of either P-Rex1 or PDGFRβ reduces invasiveness of WM852 melanoma cells.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, 3D invasion assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — Co-IP plus functional knockdown, single lab\",\n      \"pmids\": [\"23382862\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"P-Rex1 directly acts as a GEF for RhoG in vitro and in GPCR-stimulated mouse neutrophils; loss of either P-Rex1 or RhoG causes equivalent reductions in GPCR-driven Rac activation and NADPH oxidase activity; RhoG loss impairs DOCK2 and F-actin recruitment to the leading edge, revealing a P-Rex1→RhoG→DOCK2→Rac hierarchy.\",\n      \"method\": \"In vitro GEF assay for RhoG, P-Rex1 and RhoG knockout neutrophils, DOCK2 localization by immunofluorescence, NADPH oxidase activity assay\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro GEF assay establishes direct substrate; genetic epistasis in primary neutrophils with multiple readouts\",\n      \"pmids\": [\"24659802\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"P-Rex1 creates a positive feedback loop activating Rac1, PI3K/AKT, and MEK/ERK signaling independently of PTEN, and promotes insulin-like growth factor-1 receptor activation, suggesting P-Rex1 provides positive feedback to upstream PI3K activators.\",\n      \"method\": \"shRNA knockdown, Rac inhibition, P-Rex1 overexpression, phosphoproteomic analysis, PI3K inhibitor treatment in breast cancer cells\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple signaling readouts, mass spec confirmation, single lab\",\n      \"pmids\": [\"25284585\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The 1.95 Å crystal structure of the P-Rex1 DH-PH domain in complex with Rac1 was determined; mutations at the P-Rex1·Rac1 interface disrupted signaling downstream of RTKs and GPCRs; PIP3/Gβγ binding sites are on the opposite surface from the Rac1 interface, supporting a model where PIP3/Gβγ binding releases inhibitory C-terminal domains to expose the Rac1 binding site.\",\n      \"method\": \"X-ray crystallography (1.95 Å), interface mutagenesis, functional signaling assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with functional validation by mutagenesis\",\n      \"pmids\": [\"26112412\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"P-Rex1 is required in the CA1 hippocampus for LTD via a PP1α-P-Rex1-Rac1 signaling pathway that regulates AMPA receptor endocytosis; P-Rex1 deletion or knockdown in CA1 impairs LTD and causes autism-like social behavior in mice.\",\n      \"method\": \"P-Rex1 genetic deletion and shRNA knockdown in CA1, electrophysiology (LTD), AMPA receptor endocytosis assay, behavioral tests\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic loss-of-function with defined synaptic and behavioral phenotype, pathway placement via PP1α-P-Rex1-Rac1\",\n      \"pmids\": [\"26621702\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Type I PKA regulatory subunit (RIα) interacts with P-Rex1 via its PDZ domains through the CNB-B domain of RIα; P-Rex1 activation localizes PKA to the cell periphery; PKA phosphorylates P-Rex1 at Ser-436 in its DEP1 domain, which inhibits the DH-PH catalytic cassette by direct interaction; the P-Rex1 S436A mutant shows increased RacGEF activity.\",\n      \"method\": \"Co-immunoprecipitation of endogenous proteins, site-directed mutagenesis, RacGEF activity assay, immunofluorescence, cell migration assay with S436A mutant\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — endogenous Co-IP, mutagenesis with functional readout, mechanistic model of inhibitory phosphorylation confirmed\",\n      \"pmids\": [\"26797121\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PAKs (activated by Rac1 downstream of P-Rex1) phosphorylate P-Rex1 in a negative feedback loop downstream of RTK (neuregulin, IGF1) and GPCR activation, reducing P-Rex1 binding to PIP3 and GEF activity; PAK-mediated phosphorylation onset is delayed compared to AKT phosphorylation.\",\n      \"method\": \"PAK inhibitor treatment, PAK siRNA knockdown, P-Rex1 phosphorylation assays, PIP3-binding assay, GEF activity assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro and cell-based phosphorylation assays with functional readouts, single lab\",\n      \"pmids\": [\"27481946\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Norbin (Neurochondrin/NCDN), a GPCR-adaptor protein, directly binds P-Rex1 via its pleckstrin homology domain; direct interaction with Norbin increases basal, PIP3-, and Gβγ-stimulated P-Rex1 Rac-GEF activity; Norbin co-expression drives P-Rex1 translocation from cytosol to plasma membrane and promotes Rac1 activation and lamellipodia formation.\",\n      \"method\": \"Pulldown from mouse brain fractions, reciprocal Co-IP with purified proteins and in cells, GEF activity assay with purified proteins, PH domain mutagenesis, immunofluorescence and subcellular fractionation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct in vitro binding with purified proteins, GEF assay, domain mutagenesis, cell localization all in one study\",\n      \"pmids\": [\"26792863\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PKC (specifically PKCδ) directly phosphorylates P-Rex1 at Ser313, an inhibitory site that negatively regulates GEF exchange activity; activation of growth factor receptors phosphorylates Ser1169 through a PKC-independent mechanism; these multiple sites are regulated by distinct kinases.\",\n      \"method\": \"Kinase inhibitors, phospho-specific antibodies, PKCδ overexpression, site-directed mutagenesis (S313A), in vitro GEF assay\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 — PKCδ direct phosphorylation confirmed with mutagenesis and functional GEF assay, single lab\",\n      \"pmids\": [\"27788493\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"ERK/MAPK signaling drives PREX1 overexpression in BRAF- and NRAS-mutant melanoma through both increased gene transcription and enhanced protein stability; PREX1-dependent invasion is mediated by RAC1 but not CDC42.\",\n      \"method\": \"ERK inhibitor treatment, siRNA knockdown, invasion assay, Rac1/Cdc42 activation assay, gene transcription analysis\",\n      \"journal\": \"Molecular cancer research : MCR\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological and genetic perturbation with GTPase-specific readouts, single lab\",\n      \"pmids\": [\"27418645\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"GTPase-deficient GαqQL and Gα13QL form stable complexes with Gβγ that impair Gβγ interaction with P-Rex1; the N-terminal regions of Gαq and Gα13 are essential for sequestering Gβγ away from P-Rex1; Gβγ and AKT associate with SDF-1-stimulated P-Rex1; this mechanism prioritizes Gαq/Gα13→Rho signaling over Gβγ→P-Rex1→Rac signaling.\",\n      \"method\": \"Pulldown assays with constitutively active Gα mutants, chimeric Gα proteins, co-immunoprecipitation, DREADD-based chemogenetics, P-Rex1 Rac-GEF activity assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pulldown, Co-IP, and chemogenetics with functional readout, single lab\",\n      \"pmids\": [\"30446620\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PKA regulatory subunit RIα directly activates P-Rex1 in vitro and promotes P-Rex1-mediated Rac activation and endothelial cell migration downstream of Gs-coupled EP2 receptors; RIα interacts with P-Rex1 PDZ1 domain via its CNB-B domain; this is distinct from catalytic Cα subunit, which phosphorylates and inhibits P-Rex1.\",\n      \"method\": \"In vitro P-Rex1 GEF assay with purified RIα, P-Rex1 siRNA knockdown, cAMP pulldown assay, cell migration assay, RIα mutant analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct in vitro activation with purified RIα, confirmed in cells with multiple methods\",\n      \"pmids\": [\"30530493\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"GRK2 is required for TCR-induced CXCR4 phosphorylation at Ser-339, TCR-CXCR4 complex formation, and subsequent PREX1 membrane recruitment; TCR→GRK2→CXCR4→PI3Kγ→PREX1-Rac1 signaling stabilizes cytokine mRNAs and drives cytokine secretion in T cells.\",\n      \"method\": \"GRK2 siRNA, GRK2 inhibitor (paroxetine), CXCR4-Ser339 mutant analysis, PREX1 membrane recruitment assay, cytokine ELISA\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pathway epistasis established by multiple genetic/pharmacological perturbations in primary T cells\",\n      \"pmids\": [\"30018141\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The 3.2 Å cryo-EM structure of the P-Rex1-Gβγ complex reveals that the C-terminal half of P-Rex1 adopts a fold similar to Legionella phosphoinositide phosphatases; this domain coalesces with a DEP domain and two PDZ domains to form an extensive Gβγ docking site; HDX-MS shows Gβγ binding induces allosteric changes; membrane localization is required for full activation.\",\n      \"method\": \"Cryo-EM (3.2 Å), hydrogen-deuterium exchange mass spectrometry, functional GEF assays\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structure with HDX-MS dynamics and functional validation\",\n      \"pmids\": [\"31663027\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The DEP1 domain of P-Rex1 autoinhibits GEF activity by interacting with the DH/PH domains in solution; the 3.1 Å crystal structure of DEP1 shows a domain-swap involving an exposed basic loop containing the PKA phosphorylation site; PKA phosphorylation of DEP1 does not affect activity or solution conformation of DH/PH-DEP1 in vitro but inhibits DEP1 binding to phosphatidic acid-containing liposomes, suggesting PKA hampers P-Rex1 membrane binding.\",\n      \"method\": \"X-ray crystallography (3.1 Å), in vitro GEF assay of DH/PH-DEP1 fragments, liposome binding assay, PKA phosphorylation of purified proteins\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure plus in vitro functional assays with phosphomimetic analysis\",\n      \"pmids\": [\"32661198\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Small molecules targeting the P-Rex1 PH domain block PIP3 binding and inhibit fMLP-induced neutrophil spreading, Rac2 activation, and neutrophil recruitment in a zebrafish inflammation model, establishing the PH domain PIP3-binding site as a tractable drug target.\",\n      \"method\": \"Differential scanning fluorimetry screen, PIP3 binding competition assay, neutrophil Rac2 activation assay, zebrafish in vivo model\",\n      \"journal\": \"Molecular pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — biochemical binding assay plus functional cellular and in vivo validation, single lab\",\n      \"pmids\": [\"31900312\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"P-Rex1 mediates glucose-stimulated Rac1 activation and insulin secretion in pancreatic β-cells; P-Rex1 knockdown attenuates glucose-induced Rac1 activation, Rac1 membrane association, and GSIS; RhoG knockdown does not affect GSIS, distinguishing the P-Rex1-dependent pathway.\",\n      \"method\": \"siRNA knockdown, Rac1 activation pulldown assay, membrane fractionation, GSIS ELISA\",\n      \"journal\": \"Cellular physiology and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean knockdown with defined cellular and molecular phenotypes, single lab\",\n      \"pmids\": [\"33347743\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Gβγ activates P-Rex1 via two independent binding interfaces: Gβγ interacts with both the DH/PH domains and the PDZ-PDZ domains; the PDZ-PDZ/Gβγ interface mediates P-Rex1 recruitment to the plasma membrane while the DH/PH/Gβγ interface contributes to catalytic activation; C-terminal domain of P-Rex1 inhibits its catalytic activity.\",\n      \"method\": \"Pulldown assays with purified proteins, chimeric GEF (Q-Rhox) to separate recruitment from activation, plasma membrane localization imaging\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — chimeric protein approach to dissect interfaces, pulldown with purified proteins, single lab\",\n      \"pmids\": [\"33412417\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"P-Rex1 is a novel substrate of the E3 ubiquitin ligase Malin (EPM2B); Malin ubiquitinates P-Rex1, linking P-Rex1 to the laforin-Malin complex associated with Lafora disease and altered glucose uptake.\",\n      \"method\": \"Unbiased ubiquitination substrate screen using Malin E3 ligase activity, protein-protein interaction assays\",\n      \"journal\": \"Neurobiology of disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — activity-based substrate identification for ubiquitin ligase, single lab\",\n      \"pmids\": [\"36638890\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NRBP1 (a pseudokinase) binds P-Rex1 and acts as a scaffold to enhance GTP-bound Rac1 and Cdc42 levels in a P-Rex1-dependent manner; NRBP1-mediated cell migration and invasion in triple-negative breast cancer requires P-Rex1; constitutively active Rac1 rescues NRBP1 knockdown effects.\",\n      \"method\": \"BioID/MS pulldown, siRNA knockdown, constitutively active Rac1 rescue, Rac1/Cdc42 activation assay, migration/invasion assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — BioID identifies interaction, knockdown epistasis with rescue confirms pathway, single lab\",\n      \"pmids\": [\"36693952\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Cryo-EM structure of P-Rex1 bound to IP4 (at 3.2 Å resolution) reveals an autoinhibited conformation where the PH domain occludes the active site of the DH domain, stabilized by DH-DEP1 and PH-4HB subdomain interactions; disrupting these interfaces activates P-Rex1 in cells during chemokine-induced migration; PIP3-containing liposomes disrupt these interfaces, providing the mechanism of PIP3-mediated activation.\",\n      \"method\": \"Cryo-EM, HDX-MS, in vitro GEF assay with interface mutants, cell migration assay with full-length P-Rex1 interface variants, liposome binding\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structure plus HDX-MS plus interface mutagenesis validated in living cells, multiple orthogonal methods\",\n      \"pmids\": [\"39082940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"P-Rex1 limits hepatocyte glucose uptake and mitochondrial function (membrane potential, ATP production, morphology) independently of its Rac-GEF catalytic activity; P-Rex1 controls Glut2 surface levels and Gpr21 (an orphan inhibitory GPCR) trafficking at the plasma membrane; a catalytically inactive Prex1GD knock-in mouse recapitulates the glucose clearance phenotype of Prex1−/− mice.\",\n      \"method\": \"Prex1−/− and catalytically inactive Prex1GD knock-in mice, high-fat diet model, cell fractionation, Glut2 surface assay, mitochondrial function assays, Gpr21 trafficking analysis\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — catalytically dead knock-in mouse distinguishes GEF-independent function, multiple orthogonal readouts\",\n      \"pmids\": [\"41046518\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"P-Rex1 limits the agonist-induced internalization of GPCRs (S1PR1, CXCR4, PAR4, GLP1R) but not RTKs (PDGFR, EGFR) independently of its Rac-GEF activity, through its PDZ, DEP, and IP4P domains; P-Rex1 binds GRK2 directly in vitro and in cells and blocks GRK2-mediated phosphorylation required for GPCR internalization.\",\n      \"method\": \"CRISPR-Cas9 P-Rex1 KO, catalytically inactive P-Rex1 mutant, GPCR internalization assay, GRK2 binding assay in vitro and in cells, phosphorylation assay\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — catalytically dead mutant distinguishes adaptor from GEF function; direct GRK2 binding confirmed in vitro and in cells; multiple GPCRs tested\",\n      \"pmids\": [\"41100251\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"P-Rex1 mediates neutrophil phagocytosis of IgG-opsonized zymosan and bacterial killing independently of its Rac-GEF activity; P-Rex1 is required for Fc receptor-dependent Rac and Syk activation; in contrast, P-Rex1-mediated migration, ROS, and NET formation require its catalytic GEF activity.\",\n      \"method\": \"Prex1−/− and catalytically inactive Prex1GD mice, phagocytosis assay, bactericidal assay, Rac activation assay, Syk activation assay\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — catalytically dead knock-in mouse cleanly dissects GEF-dependent from GEF-independent functions across multiple assays\",\n      \"pmids\": [\"41098722\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"P-Rex1 PDZ domains interact directly with the S1P1 receptor carboxyl-terminal tail; P-Rex1 co-expression diminishes S1P1 trafficking to intracellular compartments (maintains receptor at cell surface); cells transfected with P-Rex1 PDZ domains show increased migratory response to S1P.\",\n      \"method\": \"Co-immunoprecipitation, PDZ domain-S1P1 tail binding assay, S1P1 internalization assay, cell migration assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — Co-IP and internalization assay, single lab, no in vitro reconstitution\",\n      \"pmids\": [\"20036214\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"P-Rex1 is a multi-domain Rac guanine-nucleotide exchange factor that is held in an autoinhibited state (PH domain occluding the DH active site, stabilized by DEP1-DH and PH-4HB interactions) and is synergistically activated at the plasma membrane by direct binding of PIP3 (to the PH domain) and Gβγ subunits (to a composite site formed by the DEP-PDZ-IP4P module); activation is positively regulated by PP1α-mediated dephosphorylation of Ser1165 and by the adaptor Norbin, and negatively regulated by PKA-mediated phosphorylation (principally at Ser436/DEP1, impairing membrane binding, and at additional sites via a PAK feedback loop), by inositol phosphates such as IP4 that stabilize the autoinhibited conformation, and by sequestration of Gβγ by active Gαq/Gα13; beyond its catalytic GEF role—which drives Rac1/Rac2/RhoG activation to control NADPH oxidase activity, cell migration, metastasis, GLUT4 trafficking, LTD, and insulin secretion—P-Rex1 also performs GEF-independent adaptor functions including limiting GPCR internalization through GRK2 binding and controlling hepatocyte Gpr21 trafficking to regulate glucose uptake and mitochondrial metabolism.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PREX1 encodes P-Rex1, a multidomain Rac guanine-nucleotide exchange factor (GEF) that functions as a coincidence detector for PIP3 and Gβγ signaling, integrating PI3K and GPCR inputs to activate Rac GTPases and drive neutrophil chemotaxis, ROS production, cell migration, and metastasis [PMID:11955434, PMID:16243035, PMID:22109529]. Structural studies reveal that P-Rex1 is held in an autoinhibited conformation wherein the PH domain occludes the DH catalytic site, stabilized by DEP1–DH and PH–4HB interactions; PIP3 binding to the PH domain and Gβγ engagement of a composite DEP–PDZ–IP4P surface relieve this autoinhibition, while PKA phosphorylation of Ser436 in DEP1 impairs membrane association and PP1α-mediated dephosphorylation of Ser1165 activates GEF output [PMID:39082940, PMID:31663027, PMID:26797121, PMID:22242915]. Beyond its catalytic role activating Rac1, Rac2, and RhoG in neutrophils, neurons, endothelial cells, adipocytes, and cancer cells [PMID:24659802, PMID:26621702, PMID:22002247], P-Rex1 performs GEF-independent adaptor functions: it directly binds GRK2 to limit GPCR internalization, controls hepatocyte Gpr21 trafficking and glucose metabolism, and mediates Fc receptor–dependent phagocytosis independently of its catalytic activity [PMID:41100251, PMID:41046518, PMID:41098722].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"The discovery of P-Rex1 as a Rac-GEF synergistically activated by PIP3 and Gβγ established the concept of a coincidence detector linking PI3K and heterotrimeric G protein signaling to Rac activation in neutrophils.\",\n      \"evidence\": \"Biochemical purification from neutrophil cytosol with reconstituted in vitro GEF assays\",\n      \"pmids\": [\"11955434\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for synergistic activation unknown\", \"Substrate specificity among Rac isoforms untested\", \"In vivo relevance unconfirmed\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Genetic knockout and Gβγ subunit specificity studies established that P-Rex1 preferentially activates Rac2 in neutrophils, is essential for GPCR-driven ROS and chemotaxis in vivo, and is regulated by specific Gβ1–4 subunits and inhibitory PKA phosphorylation.\",\n      \"evidence\": \"P-Rex1 KO mouse neutrophils, in vitro GEF assays with a panel of Gβγ combinations, PKA phosphorylation kinetics\",\n      \"pmids\": [\"16243036\", \"16243035\", \"16301320\", \"16301321\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Phosphorylation sites responsible for PKA inhibition unidentified\", \"Domain requirements for Gβγ binding unknown\", \"Roles beyond neutrophils unexplored\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Demonstration that PIP3 and Gβγ synergistically drive P-Rex1 membrane translocation via the DH/PH tandem, and that endogenous P-Rex1 localizes to the neutrophil leading edge, connected the biochemical activation mechanism to spatial regulation during chemotaxis.\",\n      \"evidence\": \"Subcellular fractionation of Sf9 cells with domain mutants; immunofluorescence of polarized human neutrophils\",\n      \"pmids\": [\"17698854\", \"17227822\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular contacts between P-Rex1 and the membrane undefined\", \"Role of C-terminal domains in translocation unclear\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Identification of intramolecular interactions between the DEP2/PDZ1 and IP4P domains, and their disruption by PKA phosphorylation, revealed the first intramolecular regulatory mechanism controlling Gβγ responsiveness.\",\n      \"evidence\": \"Immunoprecipitation of truncated P-Rex1 fragments, alanine mutagenesis, in vitro GEF assay\",\n      \"pmids\": [\"18514484\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific PKA site(s) mediating the effect unidentified\", \"No structural model of the full-length autoinhibited state\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Extension of P-Rex1 function beyond innate immunity to neuronal morphogenesis (neurite outgrowth via Rac3), endothelial CXCR4/SDF-1 signaling, and prostate cancer metastasis broadened the biological scope of this GEF.\",\n      \"evidence\": \"GEF-dead mutant analysis in PC12 cells/hippocampal neurons; siRNA in endothelial cells; xenograft metastasis model with GEF-dead rescue\",\n      \"pmids\": [\"18697831\", \"20018810\", \"19305425\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether P-Rex1 activates Rac3 directly in vitro not tested\", \"Role in human tumor progression not validated clinically\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Convergent ErbB receptor and Gβγ/PI3Kγ signaling through P-Rex1/Rac1 was shown to drive breast cancer cell motility and tumorigenesis, while compound P-Rex1/Vav1 KO established functional synergy between major Rac-GEF families in neutrophils.\",\n      \"evidence\": \"siRNA, dominant-negative PI3Kγ, CXCR4 epistasis in breast cancer cells; compound P-Rex1/Vav1 KO mouse neutrophils\",\n      \"pmids\": [\"21172654\", \"21178006\", \"21042280\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct physical interaction between ErbB receptors and P-Rex1 not shown\", \"Phosphorylation code for activating versus inhibitory sites incompletely mapped\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"PP1α was identified as a direct activator of P-Rex1 via dephosphorylation of Ser1165, acting independently of and additively to PIP3 and Gβγ, establishing a third regulatory input.\",\n      \"evidence\": \"In vitro GEF assay with purified PP1α, mass spectrometry of dephosphorylation sites, S1165A mutagenesis\",\n      \"pmids\": [\"22242915\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinase responsible for Ser1165 phosphorylation not identified\", \"In vivo relevance of PP1α-P-Rex1 axis in neutrophils untested at this point\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Discovery that P-Rex1 directly activates RhoG, which in turn recruits DOCK2 to amplify Rac signaling, revealed a GTPase relay (P-Rex1→RhoG→DOCK2→Rac) controlling NADPH oxidase activity and leading-edge polarity.\",\n      \"evidence\": \"In vitro GEF assay for RhoG; P-Rex1 and RhoG KO neutrophils; DOCK2 localization by immunofluorescence\",\n      \"pmids\": [\"24659802\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of RhoG recognition by P-Rex1 unknown\", \"Whether this relay operates in non-neutrophil contexts untested\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Crystal structure of the DH-PH/Rac1 complex at 1.95 Å showed that PIP3/Gβγ binding surfaces are on the opposite face from the Rac1 interface, supporting a model where activator binding relieves C-terminal domain occlusion of the active site.\",\n      \"evidence\": \"X-ray crystallography, interface mutagenesis with functional signaling readouts\",\n      \"pmids\": [\"26112412\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length autoinhibited structure not yet available\", \"Mechanism of C-terminal domain relief still inferential\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"P-Rex1 was placed in a PP1α→P-Rex1→Rac1 pathway controlling AMPA receptor endocytosis and LTD in hippocampal CA1 neurons, and P-Rex1 deletion caused autism-like social behavior in mice.\",\n      \"evidence\": \"P-Rex1 KO and shRNA in CA1, electrophysiology, AMPA receptor endocytosis assay, behavioral testing\",\n      \"pmids\": [\"26621702\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether Rac2 or RhoG participates in neuronal context unknown\", \"Behavioral phenotype assessed in single lab\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Multiple regulatory phosphorylation inputs were mapped: PKA targets Ser436 in DEP1 to impair membrane binding, PKCδ targets Ser313 for inhibition, and a PAK-mediated negative feedback loop reduces PIP3 binding; meanwhile Norbin was identified as a direct PH-domain-binding activator promoting membrane translocation.\",\n      \"evidence\": \"Site-directed mutagenesis, in vitro GEF assays, endogenous Co-IP, PAK inhibitor studies, purified Norbin binding and GEF assay\",\n      \"pmids\": [\"26797121\", \"27481946\", \"27788493\", \"26792863\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contributions of each phosphosite in vivo unknown\", \"Norbin-P-Rex1 structure not determined\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Cryo-EM structure of the P-Rex1–Gβγ complex at 3.2 Å revealed that the C-terminal IP4P-like domain, DEP, and two PDZ domains form an extensive composite Gβγ docking site, and HDX-MS showed that Gβγ binding induces allosteric conformational changes propagated to the catalytic domain.\",\n      \"evidence\": \"Cryo-EM, hydrogen-deuterium exchange mass spectrometry, functional GEF assays\",\n      \"pmids\": [\"31663027\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"PIP3-bound activation structure not captured\", \"Dynamics of autoinhibition release not resolved temporally\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"The DEP1 domain crystal structure and liposome binding experiments showed that PKA phosphorylation of DEP1 impairs membrane association rather than directly modulating catalytic activity, redefining the PKA inhibitory mechanism as membrane-targeting disruption.\",\n      \"evidence\": \"X-ray crystallography of DEP1, liposome binding assay, in vitro GEF assay of DH/PH-DEP1 fragments\",\n      \"pmids\": [\"32661198\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Effect in the context of full-length membrane-bound P-Rex1 not tested structurally\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"The cryo-EM structure of autoinhibited P-Rex1 bound to IP4 revealed that the PH domain occludes the DH active site, stabilized by DEP1–DH and PH–4HB contacts; disruption of these interfaces activated P-Rex1 in cells and PIP3-containing liposomes broke these contacts, providing the complete autoinhibition-to-activation mechanism.\",\n      \"evidence\": \"Cryo-EM at 3.2 Å, HDX-MS, interface mutagenesis validated by cell migration assay and liposome binding\",\n      \"pmids\": [\"39082940\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of fully PIP3/Gβγ-activated membrane-bound P-Rex1 not captured\", \"How IP4 stabilizes vs. merely marks the autoinhibited state unclear\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Catalytically inactive Prex1 knock-in mice revealed that P-Rex1 performs GEF-independent adaptor functions: it limits GPCR internalization by binding and blocking GRK2, controls hepatocyte glucose metabolism and Gpr21 trafficking, and mediates Fc receptor-dependent phagocytosis — all independent of Rac exchange activity.\",\n      \"evidence\": \"Catalytically dead Prex1GD knock-in and Prex1 KO mice, GPCR internalization assays across multiple receptors, in vitro GRK2 binding, phagocytosis and bactericidal assays\",\n      \"pmids\": [\"41100251\", \"41046518\", \"41098722\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of GRK2 interaction unknown\", \"Whether adaptor functions require specific domain contacts beyond PDZ/DEP/IP4P not mapped\", \"Relative physiological importance of GEF vs. adaptor functions in vivo unquantified\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A full structural picture of P-Rex1 activation on the membrane — capturing simultaneous PIP3, Gβγ, and Norbin engagement in the context of the lipid bilayer — remains unresolved, as does the in vivo phosphorylation code integrating PKA, PKC, PAK, and PP1α inputs.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structure of fully activated membrane-bound P-Rex1\", \"Quantitative integration of multiple phosphorylation inputs in vivo unknown\", \"Physiological contexts requiring GEF-independent adaptor functions versus catalytic functions incompletely delineated\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [42, 43, 44]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 2, 22, 24]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 5, 7]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [5, 7, 28, 41]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [2, 3, 14, 22, 44]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 13, 20, 26]},\n      {\"term_id\": \"R-HSA-1500931\", \"supporting_discovery_ids\": [10, 11, 15, 30]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"GNB1\", \"GNG2\", \"PPP1CA\", \"NCDN\", \"GRK2\", \"PRKAR1A\", \"NRBP1\", \"MTOR\"],\n    \"other_free_text\": []\n  }\n}\n```"}