{"gene":"PREX2","run_date":"2026-04-28T19:45:45","timeline":{"discoveries":[{"year":2004,"finding":"PREX2 (P-Rex2) is a guanine-nucleotide exchange factor (GEF) that activates the small GTPase Rac and is synergistically regulated by PIP3 and Gβγ subunits of heterotrimeric G proteins in vitro and in vivo.","method":"GEF activity assays, in vitro and in vivo Rac activation assays","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 — two independent labs simultaneously reported GEF activity and regulation by PIP3/Gβγ with functional assays","pmids":["15304343","15304342"],"is_preprint":false},{"year":2004,"finding":"PREX2 activates Rac in a PI3K-dependent manner, linking it to the PI3K signaling pathway.","method":"GTP-bound Rac measurement after PI3K stimulation","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 — replicated in two simultaneous independent publications","pmids":["15304342","15304343"],"is_preprint":false},{"year":2008,"finding":"P-Rex2 is specifically expressed in cerebellar Purkinje neurons and is required for normal Purkinje cell dendrite morphology; P-Rex2 knockout mice exhibit thinned main dendrites in Purkinje cells and progressive motor coordination defects.","method":"P-Rex2 knockout mouse generation, histological analysis of Purkinje cell morphology, behavioral motor tests","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — clean KO mouse with defined cellular and behavioral phenotypes, replicated in double KO","pmids":["18334636"],"is_preprint":false},{"year":2012,"finding":"PREX2 is a PTEN-interacting protein and negative regulator of PTEN; somatic PREX2 mutations at ~14% frequency in melanoma accelerate tumor formation of immortalized human melanocytes in vivo.","method":"Whole-genome sequencing, ectopic expression in NRASG12D melanocytes, in vivo tumor formation assay","journal":"Nature","confidence":"Medium","confidence_rationale":"Tier 2 — functional in vivo assay, but replication attempt failed to reproduce the accelerated tumor formation result","pmids":["22622578"],"is_preprint":false},{"year":2013,"finding":"P-REX2 inhibits PTEN via two interfaces: the PH domain of P-REX2 inhibits PTEN by interacting with the catalytic region of PTEN, and the IP4P domain provides high-affinity binding to the PDZ-binding domain of PTEN. P-REX2 inhibition of PTEN requires C-terminal phosphorylation of PTEN to release the P-REX2 PH domain from its neighboring DH domain. Prex2 deletion in mice increases Pten activity and decreases insulin signaling in liver and adipose tissue, leading to reduced glucose uptake and insulin resistance.","method":"Domain mapping, co-immunoprecipitation, Prex2 knockout mouse, insulin signaling assays, glucose uptake assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods including domain mapping, KO mouse, and metabolic phenotyping","pmids":["24367090"],"is_preprint":false},{"year":2015,"finding":"PTEN inhibits PREX2 GEF activity toward RAC1 via its C-terminal tail domain (independent of PTEN lipid phosphatase activity). Cancer-derived somatic PREX2 mutants are resistant to PTEN-mediated inhibition of invasion, with two mutants escaping GEF inhibition and a third showing reduced PTEN binding affinity.","method":"Fluorescent nucleotide exchange assays (in vitro GEF activity), cell invasion assays, co-immunoprecipitation, mouse embryonic fibroblasts and breast cancer cell lines","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 1 — in vitro GEF assay with mutagenesis, multiple orthogonal methods","pmids":["25829446"],"is_preprint":false},{"year":2015,"finding":"PAK kinases phosphorylate PREX2 following Rac1 activation, reducing PREX2 GEF activity toward Rac1 by inhibiting PREX2 binding to PIP3 and Gβγ. PAK-mediated phosphorylation also prevents PREX2 membrane localization, constituting a negative feedback loop on Rac1 signaling downstream of insulin.","method":"In vitro GEF assays, cell fractionation, mass spectrometry phosphosite identification, PAK inhibitor experiments, insulin stimulation assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro GEF assay combined with fractionation, MS phosphosite mapping, and mechanistic epistasis","pmids":["26438819"],"is_preprint":false},{"year":2017,"finding":"GNMT interacts with PREX2 and promotes its degradation through an HectH9 (HUWE1) E3 ligase-mediated proteasomal ubiquitination pathway. Depletion of GNMT or HectH9 leads to elevated PREX2 protein and AKT activation.","method":"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown, protein stability assays","journal":"International journal of cancer","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, ubiquitination assays, and genetic perturbation with defined pathway phenotype","pmids":["28205209"],"is_preprint":false},{"year":2018,"finding":"Crystal structure of the P-Rex2 PH domain at 1.9 Å reveals conformational differences in loop regions compared to P-Rex1. The P-Rex2 PH domain binds PIP3 similarly to P-Rex1, and PIP3 binding is critical for P-Rex2 GEF activity but not membrane localization.","method":"X-ray crystallography, biochemical PIP3 binding assays","journal":"Journal of structural biology: X","confidence":"High","confidence_rationale":"Tier 1 — crystal structure at 1.9 Å combined with biochemical functional validation","pmids":["34958187"],"is_preprint":false},{"year":2019,"finding":"The PREX2 gain-of-function mutation S1113R, identified in HCC, enhances PREX2 protein stability by impairing HectH9-mediated ubiquitination, promotes cell migration, and activates the AKT pathway.","method":"Protein half-life assays, ubiquitination assays, cell migration assays, AKT phosphorylation western blot","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 — multiple functional assays in single study","pmids":["30796242"],"is_preprint":false},{"year":2020,"finding":"CELF2 interacts with PREX2 and reduces the association of PREX2 with PTEN, thereby upregulating PTEN phosphatase activity and repressing AKT phosphorylation. This represents a mechanism by which CELF2 antagonizes the oncogenic effect of PREX2.","method":"Co-immunoprecipitation, PTEN phosphatase activity assay, AKT phosphorylation assay, PDX tumor model","journal":"Carcinogenesis","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP, enzymatic activity assay, and in vivo validation in single study","pmids":["31241130"],"is_preprint":false},{"year":2021,"finding":"Cross-linking mass spectrometry and functional studies revealed the structural basis of PTEN:P-Rex2 complex assembly: PTEN is anchored to P-Rex2 via interactions between the PTEN C-terminal PDZ-interacting motif and the second PDZ domain of P-Rex2, bridging PTEN across the P-Rex2 surface to prevent PI(3,4,5)P3 hydrolysis. Conversely, PTEN allosterically promotes an autoinhibited P-Rex2 conformation and blocks Gβγ binding to P-Rex2.","method":"Cross-linking mass spectrometry, functional GEF and phosphatase activity assays, mutagenesis","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 1-2 — cross-linking MS structural data combined with functional mutagenesis and activity assays","pmids":["33947796"],"is_preprint":false},{"year":2022,"finding":"P-Rex2 mediates synaptic plasticity in bone cancer pain by activating Rac1 and phosphorylating GluR1, promoting GluR1-containing AMPA receptor trafficking and spine morphology changes in dorsal horn neurons.","method":"RNAi lentivirus knockdown in vivo, western blot for p-Rac1 and p-GluR1, spine counting, patch-clamp electrophysiology","journal":"Molecular pain","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo knockdown with multiple readouts including electrophysiology","pmids":["35083941"],"is_preprint":false},{"year":2024,"finding":"PREX2 promotes radioresistance in colorectal cancer by facilitating DNA repair through upregulation of DNA-PKcs and suppressing radiation-induced immunogenic cell death by inhibiting the cGAS/STING/IFNs pathway, thereby impeding CD8+ T cell infiltration.","method":"RNA-seq, colony formation assay, comet assay, apoptosis assay, western blot, xenograft mouse models, PREX2 inhibitor (PREX-in1)","journal":"BMC medicine","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal in vitro and in vivo methods in single study","pmids":["38609982"],"is_preprint":false},{"year":2025,"finding":"AHCYL1 is a novel PREX2-interacting protein that enhances PREX2 GEF activity toward RAC1 by alleviating the mutual inhibition between PREX2 and PTEN.","method":"Pull-down assay, LC-MS/MS, in vitro GEF assay, active RAC1 pull-down assay, western blotting","journal":"Theranostics","confidence":"Medium","confidence_rationale":"Tier 1-2 — in vitro GEF assay and pull-down combined with MS identification in single study","pmids":["40365293"],"is_preprint":false},{"year":2025,"finding":"P-Rex2 suppresses glucose uptake into liver and skeletal muscle independently of its Rac-GEF catalytic activity (demonstrated using catalytically-inactive Prex2GD knockin mice). In hepatocytes, P-Rex2 suppresses Glut2 surface levels and mitochondrial ATP production, and controls trafficking of the orphan GPCR Gpr21. In skeletal muscle, P-Rex2 suppresses glucose uptake via a separate adaptor function independent of Gpr21.","method":"Prex2 knockout and catalytically-inactive Prex2GD knockin mice, glucose uptake assays, Glut2 surface assay, mitochondrial membrane potential assay, Gpr21 trafficking assay","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 — catalytically-inactive knockin combined with KO mouse clearly dissects GEF-dependent vs. adaptor functions with multiple orthogonal cellular readouts","pmids":["40764335"],"is_preprint":false},{"year":2025,"finding":"Genetic loss of PREX2 in BRAF-mutant melanoma confers sensitivity to MAPK pathway inhibitors, and PREX2 acts upstream of RAC1 and PI3Kβ in a druggable signaling axis; pharmacological PI3Kβ inhibition phenocopies PREX2 deficiency.","method":"Genetically engineered mouse models, patient-derived melanoma cell lines, genetic and pharmacologic PI3Kβ inhibition, BRAF inhibitor sensitivity assays","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis in mouse models and patient-derived lines with pharmacologic validation","pmids":["39636745"],"is_preprint":false},{"year":2026,"finding":"Cryo-EM structure of full-length P-Rex2 reveals that while the overall structure resembles P-Rex1, there is a substantial repositioning of the N-terminal module relative to the C-terminal core, potentially precluding the intramolecular N-terminal/C-terminal interactions seen in autoinhibited P-Rex1. HDX-MS shows P-Rex2 dynamics are unaffected by IP4 (PIP3 headgroup), unlike P-Rex1, suggesting a distinct autoinhibition mechanism.","method":"Cryo-EM, hydrogen-deuterium exchange mass spectrometry (HDX-MS), SEC-SAXS, biochemical GEF assays","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 — cryo-EM structure with HDX-MS and biochemistry, but preprint not yet peer-reviewed","pmids":["41542420"],"is_preprint":true}],"current_model":"PREX2 is a PIP3- and Gβγ-activated Rac1 GEF that forms a mutual inhibitory complex with the tumor suppressor PTEN (anchored via PTEN's PDZ-interacting motif binding the second PDZ domain of PREX2), whereby PTEN allosterically autoinhibits PREX2 and blocks Gβγ binding while PREX2's PH domain inhibits PTEN's phosphatase activity; this complex is subject to feedback regulation by PAK-mediated phosphorylation of PREX2 (reducing its PIP3/Gβγ binding and membrane localization), proteasomal degradation via HectH9-mediated ubiquitination promoted by GNMT, and positive modulation by AHCYL1; cancer-associated PREX2 mutations escape PTEN-mediated inhibition to drive constitutive RAC1/PI3K-AKT signaling, while physiologically PREX2 regulates cerebellar Purkinje cell morphology, glucose homeostasis (suppressing hepatic and skeletal muscle glucose uptake through GEF-independent adaptor functions), and synaptic plasticity."},"narrative":{"teleology":[{"year":2004,"claim":"Establishing the core enzymatic identity of PREX2 as a Rac-GEF synergistically activated by PIP3 and Gβγ answered the fundamental question of what this multi-domain protein does biochemically and placed it at the intersection of PI3K and GPCR signaling.","evidence":"In vitro and in vivo GEF activity assays with PIP3/Gβγ stimulation, reported simultaneously by two independent groups","pmids":["15304343","15304342"],"confidence":"High","gaps":["Substrate specificity beyond Rac1 not tested","Structural basis of PIP3/Gβγ synergy unknown","Tissue-specific functions uncharacterized"]},{"year":2008,"claim":"Generation of P-Rex2 knockout mice revealed its first physiological role — maintaining Purkinje cell dendrite morphology and motor coordination — demonstrating that PREX2 is not redundant with the related P-Rex1 in the cerebellum.","evidence":"P-Rex2 knockout and P-Rex1/P-Rex2 double-knockout mice with histological and behavioral analysis","pmids":["18334636"],"confidence":"High","gaps":["Whether the Purkinje cell phenotype is Rac1-GEF-dependent or adaptor-mediated was not distinguished","Downstream effectors in dendrite morphogenesis not identified"]},{"year":2012,"claim":"The discovery that PREX2 binds and inhibits PTEN, and that PREX2 is recurrently mutated in melanoma, reframed the gene as an oncogenic regulator of the PI3K/AKT axis rather than solely a Rac-GEF.","evidence":"Whole-genome sequencing of melanomas; ectopic PREX2 expression in NRAS-mutant melanocytes with in vivo tumor formation assay","pmids":["22622578"],"confidence":"Medium","gaps":["Independent replication of tumor acceleration failed","Whether PTEN inhibition or Rac activation drives tumorigenic phenotype was unresolved"]},{"year":2013,"claim":"Mapping the two-interface interaction between PREX2 and PTEN (PH domain–PTEN catalytic region and IP4P domain–PTEN PDZ-binding domain), and showing that Prex2 loss increases PTEN activity and impairs insulin signaling in vivo, established the molecular logic of mutual inhibition and its metabolic relevance.","evidence":"Domain mapping, co-immunoprecipitation, Prex2 knockout mouse with insulin signaling and glucose uptake assays","pmids":["24367090"],"confidence":"High","gaps":["Structural resolution of the interface lacking","Mechanism linking PTEN C-terminal phosphorylation to PH domain release incompletely defined"]},{"year":2015,"claim":"Two studies resolved opposite arms of the mutual inhibition: PTEN inhibits PREX2 GEF activity via its C-terminal tail (independently of phosphatase activity), and cancer-derived PREX2 mutants escape this inhibition; simultaneously, PAK-mediated phosphorylation of PREX2 was identified as a negative feedback loop that reduces PIP3/Gβγ binding and membrane localization after Rac1 activation.","evidence":"In vitro fluorescent nucleotide exchange assays with mutant panels, cell invasion assays; in vitro GEF assays with PAK phosphorylation, mass spectrometry phosphosite mapping, cell fractionation","pmids":["25829446","26438819"],"confidence":"High","gaps":["PAK phosphorylation sites not mapped to structural domains","Whether PTEN tail inhibition is allosteric or steric was unclear"]},{"year":2017,"claim":"Identification of GNMT–HectH9(HUWE1)-mediated proteasomal ubiquitination as the mechanism controlling PREX2 protein turnover added a proteostatic regulatory layer and explained how GNMT suppresses AKT signaling.","evidence":"Reciprocal co-immunoprecipitation, ubiquitination assays, siRNA knockdown of GNMT and HectH9","pmids":["28205209"],"confidence":"High","gaps":["Ubiquitination sites on PREX2 not mapped","Whether ubiquitination is constitutive or signal-regulated not determined"]},{"year":2018,"claim":"The 1.9 Å crystal structure of the P-Rex2 PH domain showed that PIP3 binding is essential for GEF activity but not membrane localization, distinguishing lipid-dependent activation from membrane targeting.","evidence":"X-ray crystallography and biochemical PIP3 binding assays","pmids":["34958187"],"confidence":"High","gaps":["Structure of remaining domains and full-length protein not resolved","PIP3-induced conformational changes in the DH-PH tandem not visualized"]},{"year":2021,"claim":"Cross-linking mass spectrometry of the PTEN–P-Rex2 complex provided a near-complete structural model of their mutual inhibition: PTEN's PDZ-interacting motif anchors to the second PDZ domain of P-Rex2, positioning PTEN to block PIP3 hydrolysis, while PTEN allosterically stabilizes P-Rex2 autoinhibition and blocks Gβγ binding.","evidence":"Cross-linking mass spectrometry, functional GEF and phosphatase activity assays with targeted mutations","pmids":["33947796"],"confidence":"High","gaps":["High-resolution atomic model of the full complex not available","Dynamics of complex assembly and disassembly upon signaling not characterized"]},{"year":2022,"claim":"PREX2's role was extended to synaptic plasticity, showing that P-Rex2 activates Rac1 in dorsal horn neurons to phosphorylate GluR1 and promote AMPA receptor trafficking during bone cancer pain, establishing a neuronal signaling function beyond cerebellum.","evidence":"In vivo lentiviral knockdown, patch-clamp electrophysiology, spine morphology analysis in dorsal horn neurons","pmids":["35083941"],"confidence":"Medium","gaps":["Direct GEF activity measurement in these neurons lacking","Relevance to non-pain synaptic plasticity not tested"]},{"year":2025,"claim":"Use of catalytically-inactive Prex2 knockin mice demonstrated that PREX2 suppresses glucose uptake in liver and skeletal muscle through a GEF-independent adaptor function, controlling GLUT2 surface levels and GPR21 trafficking — a fundamentally new mode of action for PREX2.","evidence":"Prex2 KO and catalytically-inactive Prex2GD knockin mice with glucose uptake, GLUT2 surface, mitochondrial ATP, and GPR21 trafficking assays","pmids":["40764335"],"confidence":"High","gaps":["Adaptor-binding partners mediating GLUT2/GPR21 trafficking not identified","How GEF-independent and GEF-dependent functions are coordinated in vivo unknown"]},{"year":2025,"claim":"Genetic loss of PREX2 sensitizes BRAF-mutant melanoma to MAPK inhibitors, with PI3Kβ inhibition phenocopying PREX2 deficiency, defining a druggable PREX2–RAC1–PI3Kβ signaling axis in therapy resistance.","evidence":"Genetically engineered mouse melanoma models, patient-derived cell lines, pharmacologic PI3Kβ inhibition","pmids":["39636745"],"confidence":"Medium","gaps":["Whether PREX2 directly activates PI3Kβ or acts via RAC1 not resolved","Clinical validation in patient cohorts lacking"]},{"year":null,"claim":"A high-resolution structure of the full-length PREX2–PTEN complex and the molecular basis of PREX2's GEF-independent adaptor functions remain the central unresolved mechanistic questions.","evidence":"","pmids":[],"confidence":"High","gaps":["No atomic-resolution structure of full-length PREX2 in complex with PTEN","Adaptor-mode binding partners and structural basis for GLUT2/GPR21 regulation unknown","In vivo regulation of PREX2 at different tissues (brain vs. liver vs. muscle) not integrated"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,5,6,8,14]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[15]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[4,5,10]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[6,8]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[6]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,4,5,6,11,14,16]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[2]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[3,9,13,16]}],"complexes":["PREX2–PTEN complex"],"partners":["PTEN","RAC1","PAK1","GNMT","HUWE1","AHCYL1","CELF2","GPR21"],"other_free_text":[]},"mechanistic_narrative":"PREX2 is a PIP3- and Gβγ-activated guanine-nucleotide exchange factor (GEF) for RAC1 that integrates PI3K and G-protein signaling to regulate cytoskeletal remodeling, insulin/glucose metabolism, and synaptic plasticity. PREX2 forms a mutual inhibitory complex with PTEN, in which the PREX2 PH domain blocks PTEN phosphatase activity while PTEN allosterically promotes PREX2 autoinhibition and occludes Gβγ binding, with PTEN anchored via its C-terminal PDZ-interacting motif to the second PDZ domain of PREX2 [PMID:33947796, PMID:24367090, PMID:25829446]; this complex is positively modulated by AHCYL1 [PMID:40365293] and negatively regulated by PAK-mediated phosphorylation that reduces PREX2 membrane recruitment [PMID:26438819] and GNMT/HectH9-mediated proteasomal degradation [PMID:28205209]. In vivo, PREX2 is required for cerebellar Purkinje cell dendrite morphology and motor coordination [PMID:18334636], and suppresses hepatic and skeletal-muscle glucose uptake through a GEF-independent adaptor function controlling GLUT2 surface levels and GPR21 trafficking [PMID:40764335]. Cancer-associated PREX2 mutations escape PTEN-mediated inhibition to drive constitutive RAC1/PI3K–AKT signaling and confer resistance to MAPK pathway inhibitors in melanoma [PMID:25829446, PMID:39636745]."},"prefetch_data":{"uniprot":{"accession":"Q70Z35","full_name":"Phosphatidylinositol 3,4,5-trisphosphate-dependent Rac exchanger 2 protein","aliases":["DEP domain-containing protein 2"],"length_aa":1606,"mass_kda":182.6,"function":"Functions as a RAC1 guanine nucleotide exchange factor (GEF), activating 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. Mediates the activation of RAC1 in a PI3K-dependent manner. May be an important mediator of Rac signaling, acting directly downstream of both G protein-coupled receptors and phosphoinositide 3-kinase","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q70Z35/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PREX2","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PREX2","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"},{"mim_id":"260350","title":"PANCREATIC CANCER","url":"https://www.omim.org/entry/260350"},{"mim_id":"155600","title":"MELANOMA, CUTANEOUS MALIGNANT, SUSCEPTIBILITY TO, 1; CMM1","url":"https://www.omim.org/entry/155600"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Endoplasmic reticulum","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/PREX2"},"hgnc":{"alias_symbol":["DEP.2","FLJ12987","P-REX2","PPP1R129"],"prev_symbol":["DEPDC2"]},"alphafold":{"accession":"Q70Z35","domains":[{"cath_id":"1.20.900.10","chopping":"14-220","consensus_level":"high","plddt":89.3971,"start":14,"end":220},{"cath_id":"2.30.29.30","chopping":"234-279_293-367","consensus_level":"medium","plddt":87.0098,"start":234,"end":367},{"cath_id":"1.10.10.10","chopping":"394-470","consensus_level":"medium","plddt":84.069,"start":394,"end":470},{"cath_id":"1.10.10.10","chopping":"481-571","consensus_level":"high","plddt":86.4443,"start":481,"end":571},{"cath_id":"2.30.42.10","chopping":"585-675","consensus_level":"medium","plddt":88.5386,"start":585,"end":675},{"cath_id":"2.30.42.10","chopping":"677-768_804-814","consensus_level":"medium","plddt":82.223,"start":677,"end":814}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q70Z35","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q70Z35-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q70Z35-F1-predicted_aligned_error_v6.png","plddt_mean":79.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PREX2","jax_strain_url":"https://www.jax.org/strain/search?query=PREX2"},"sequence":{"accession":"Q70Z35","fasta_url":"https://rest.uniprot.org/uniprotkb/Q70Z35.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q70Z35/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q70Z35"}},"corpus_meta":[{"pmid":"22622578","id":"PMC_22622578","title":"Melanoma genome sequencing reveals frequent PREX2 mutations.","date":"2012","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/22622578","citation_count":588,"is_preprint":false},{"pmid":"15304343","id":"PMC_15304343","title":"P-Rex2, a new guanine-nucleotide exchange factor for Rac.","date":"2004","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/15304343","citation_count":88,"is_preprint":false},{"pmid":"15304342","id":"PMC_15304342","title":"P-REX2, a novel PI-3-kinase sensitive Rac exchange factor.","date":"2004","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/15304342","citation_count":82,"is_preprint":false},{"pmid":"25829446","id":"PMC_25829446","title":"PTEN inhibits PREX2-catalyzed activation of RAC1 to restrain tumor cell invasion.","date":"2015","source":"Science signaling","url":"https://pubmed.ncbi.nlm.nih.gov/25829446","citation_count":62,"is_preprint":false},{"pmid":"18334636","id":"PMC_18334636","title":"P-Rex2 regulates Purkinje cell dendrite morphology and motor coordination.","date":"2008","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/18334636","citation_count":58,"is_preprint":false},{"pmid":"24367090","id":"PMC_24367090","title":"Regulation of PTEN inhibition by the pleckstrin homology domain of P-REX2 during insulin signaling and glucose homeostasis.","date":"2013","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/24367090","citation_count":57,"is_preprint":false},{"pmid":"31241130","id":"PMC_31241130","title":"CELF2 suppresses non-small cell lung carcinoma growth by inhibiting the PREX2-PTEN interaction.","date":"2020","source":"Carcinogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/31241130","citation_count":43,"is_preprint":false},{"pmid":"28710285","id":"PMC_28710285","title":"P-Rex1 and P-Rex2 RacGEFs and cancer.","date":"2017","source":"Biochemical Society transactions","url":"https://pubmed.ncbi.nlm.nih.gov/28710285","citation_count":38,"is_preprint":false},{"pmid":"28205209","id":"PMC_28205209","title":"Characterization of the GNMT-HectH9-PREX2 tripartite relationship in the pathogenesis of hepatocellular carcinoma.","date":"2017","source":"International journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/28205209","citation_count":27,"is_preprint":false},{"pmid":"25151370","id":"PMC_25151370","title":"The effect of CXCL9 on the invasion ability of hepatocellular carcinoma through up-regulation of PREX2.","date":"2014","source":"Journal of molecular histology","url":"https://pubmed.ncbi.nlm.nih.gov/25151370","citation_count":26,"is_preprint":false},{"pmid":"30796242","id":"PMC_30796242","title":"Somatic mutations of PREX2 gene in patients with hepatocellular carcinoma.","date":"2019","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/30796242","citation_count":20,"is_preprint":false},{"pmid":"31582017","id":"PMC_31582017","title":"Involvement of TLR4/ CXCL9/ PREX-2 pathway in the development of hepatocellular carcinoma (HCC) and the promising role of early administration of lactobacillus plantarum in Wistar rats.","date":"2019","source":"Tissue & cell","url":"https://pubmed.ncbi.nlm.nih.gov/31582017","citation_count":20,"is_preprint":false},{"pmid":"28100394","id":"PMC_28100394","title":"Replication Study: Melanoma genome sequencing reveals frequent PREX2 mutations.","date":"2017","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/28100394","citation_count":19,"is_preprint":false},{"pmid":"26438819","id":"PMC_26438819","title":"p21-activated Kinases (PAKs) Mediate the Phosphorylation of PREX2 Protein to Initiate Feedback Inhibition of Rac1 GTPase.","date":"2015","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/26438819","citation_count":19,"is_preprint":false},{"pmid":"26998152","id":"PMC_26998152","title":"Upregulation of PREX2 promotes the proliferation and migration of hepatocellular carcinoma cells via PTEN-AKT signaling.","date":"2016","source":"Oncology letters","url":"https://pubmed.ncbi.nlm.nih.gov/26998152","citation_count":15,"is_preprint":false},{"pmid":"38609982","id":"PMC_38609982","title":"PREX2 contributes to radiation resistance by inhibiting radiotherapy-induced tumor immunogenicity via cGAS/STING/IFNs pathway in colorectal cancer.","date":"2024","source":"BMC medicine","url":"https://pubmed.ncbi.nlm.nih.gov/38609982","citation_count":14,"is_preprint":false},{"pmid":"33947796","id":"PMC_33947796","title":"Structural analysis of the PTEN:P-Rex2 signaling complex reveals how cancer-associated mutations coordinate to hyperactivate Rac1.","date":"2021","source":"Science signaling","url":"https://pubmed.ncbi.nlm.nih.gov/33947796","citation_count":12,"is_preprint":false},{"pmid":"27446408","id":"PMC_27446408","title":"PREX2 promotes the proliferation, invasion and migration of pancreatic cancer cells by modulating the PI3K signaling pathway.","date":"2016","source":"Oncology letters","url":"https://pubmed.ncbi.nlm.nih.gov/27446408","citation_count":10,"is_preprint":false},{"pmid":"39636745","id":"PMC_39636745","title":"Targeting the PREX2/RAC1/PI3Kβ Signaling Axis Confers Sensitivity to Clinically Relevant Therapeutic Approaches in Melanoma.","date":"2025","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/39636745","citation_count":5,"is_preprint":false},{"pmid":"27314100","id":"PMC_27314100","title":"Mechanistic insights into the role of truncating PREX2 mutations in melanoma.","date":"2016","source":"Molecular & cellular oncology","url":"https://pubmed.ncbi.nlm.nih.gov/27314100","citation_count":5,"is_preprint":false},{"pmid":"34958187","id":"PMC_34958187","title":"Structural and biochemical characterization of the pleckstrin homology domain of the RhoGEF P-Rex2 and its regulation by PIP3.","date":"2018","source":"Journal of structural biology: X","url":"https://pubmed.ncbi.nlm.nih.gov/34958187","citation_count":5,"is_preprint":false},{"pmid":"34705970","id":"PMC_34705970","title":"PREX2 gene's expression in gastric antral epithelial cells of patients with H. pylori infection.","date":"2021","source":"Arquivos de gastroenterologia","url":"https://pubmed.ncbi.nlm.nih.gov/34705970","citation_count":3,"is_preprint":false},{"pmid":"25490935","id":"PMC_25490935","title":"Registered report: Melanoma genome sequencing reveals frequent PREX2 mutations.","date":"2014","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/25490935","citation_count":3,"is_preprint":false},{"pmid":"23844743","id":"PMC_23844743","title":"P-Rex2, a Rac-guanine nucleotide exchange factor, is expressed selectively in ribbon synaptic terminals of the mouse retina.","date":"2013","source":"BMC neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/23844743","citation_count":3,"is_preprint":false},{"pmid":"40764335","id":"PMC_40764335","title":"P-Rex2 suppresses glucose uptake into liver and skeletal muscle through different adaptor functions.","date":"2025","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/40764335","citation_count":2,"is_preprint":false},{"pmid":"35083941","id":"PMC_35083941","title":"P-Rex2 mediation of synaptic plasticity contributes to bone cancer pain.","date":"2022","source":"Molecular pain","url":"https://pubmed.ncbi.nlm.nih.gov/35083941","citation_count":2,"is_preprint":false},{"pmid":"34988572","id":"PMC_34988572","title":"Sustainable and cost-effective ternary electrolyte Et3NHCl-AlCl3-Mg(DEP)2 for high-performance rechargeable magnesium batteries.","date":"2022","source":"Physical chemistry chemical physics : PCCP","url":"https://pubmed.ncbi.nlm.nih.gov/34988572","citation_count":1,"is_preprint":false},{"pmid":"40365293","id":"PMC_40365293","title":"AHCYL1 mediates the tumor-promoting effect of PREX2 in non-small cell lung carcinoma.","date":"2025","source":"Theranostics","url":"https://pubmed.ncbi.nlm.nih.gov/40365293","citation_count":0,"is_preprint":false},{"pmid":"40971540","id":"PMC_40971540","title":"Unraveling the role of PREX2 mutations as a biomarker for immunotherapy response in colorectal cancer.","date":"2025","source":"Cancer biomarkers : section A of Disease markers","url":"https://pubmed.ncbi.nlm.nih.gov/40971540","citation_count":0,"is_preprint":false},{"pmid":"34386078","id":"PMC_34386078","title":"PREX2 promotes the proliferation, invasion and migration of pancreatic cancer cells by modulating the PI3K signaling pathway.","date":"2021","source":"Oncology letters","url":"https://pubmed.ncbi.nlm.nih.gov/34386078","citation_count":0,"is_preprint":false},{"pmid":"41542420","id":"PMC_41542420","title":"P-Rex2 exhibits unique structural features and regulatory mechanisms distinct from the closely related RhoGEF P-Rex1.","date":"2026","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/41542420","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":15874,"output_tokens":4200,"usd":0.055311},"stage2":{"model":"claude-opus-4-6","input_tokens":7719,"output_tokens":3133,"usd":0.17538},"total_usd":0.230691,"stage1_batch_id":"msgbatch_01SUR8NDzVrNmyszWyJeCct7","stage2_batch_id":"msgbatch_01G7Yfutko3cDWzejrwH5AMx","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2004,\n      \"finding\": \"PREX2 (P-Rex2) is a guanine-nucleotide exchange factor (GEF) that activates the small GTPase Rac and is synergistically regulated by PIP3 and Gβγ subunits of heterotrimeric G proteins in vitro and in vivo.\",\n      \"method\": \"GEF activity assays, in vitro and in vivo Rac activation assays\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — two independent labs simultaneously reported GEF activity and regulation by PIP3/Gβγ with functional assays\",\n      \"pmids\": [\"15304343\", \"15304342\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"PREX2 activates Rac in a PI3K-dependent manner, linking it to the PI3K signaling pathway.\",\n      \"method\": \"GTP-bound Rac measurement after PI3K stimulation\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — replicated in two simultaneous independent publications\",\n      \"pmids\": [\"15304342\", \"15304343\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"P-Rex2 is specifically expressed in cerebellar Purkinje neurons and is required for normal Purkinje cell dendrite morphology; P-Rex2 knockout mice exhibit thinned main dendrites in Purkinje cells and progressive motor coordination defects.\",\n      \"method\": \"P-Rex2 knockout mouse generation, histological analysis of Purkinje cell morphology, behavioral motor tests\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO mouse with defined cellular and behavioral phenotypes, replicated in double KO\",\n      \"pmids\": [\"18334636\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PREX2 is a PTEN-interacting protein and negative regulator of PTEN; somatic PREX2 mutations at ~14% frequency in melanoma accelerate tumor formation of immortalized human melanocytes in vivo.\",\n      \"method\": \"Whole-genome sequencing, ectopic expression in NRASG12D melanocytes, in vivo tumor formation assay\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional in vivo assay, but replication attempt failed to reproduce the accelerated tumor formation result\",\n      \"pmids\": [\"22622578\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"P-REX2 inhibits PTEN via two interfaces: the PH domain of P-REX2 inhibits PTEN by interacting with the catalytic region of PTEN, and the IP4P domain provides high-affinity binding to the PDZ-binding domain of PTEN. P-REX2 inhibition of PTEN requires C-terminal phosphorylation of PTEN to release the P-REX2 PH domain from its neighboring DH domain. Prex2 deletion in mice increases Pten activity and decreases insulin signaling in liver and adipose tissue, leading to reduced glucose uptake and insulin resistance.\",\n      \"method\": \"Domain mapping, co-immunoprecipitation, Prex2 knockout mouse, insulin signaling assays, glucose uptake assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods including domain mapping, KO mouse, and metabolic phenotyping\",\n      \"pmids\": [\"24367090\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PTEN inhibits PREX2 GEF activity toward RAC1 via its C-terminal tail domain (independent of PTEN lipid phosphatase activity). Cancer-derived somatic PREX2 mutants are resistant to PTEN-mediated inhibition of invasion, with two mutants escaping GEF inhibition and a third showing reduced PTEN binding affinity.\",\n      \"method\": \"Fluorescent nucleotide exchange assays (in vitro GEF activity), cell invasion assays, co-immunoprecipitation, mouse embryonic fibroblasts and breast cancer cell lines\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro GEF assay with mutagenesis, multiple orthogonal methods\",\n      \"pmids\": [\"25829446\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PAK kinases phosphorylate PREX2 following Rac1 activation, reducing PREX2 GEF activity toward Rac1 by inhibiting PREX2 binding to PIP3 and Gβγ. PAK-mediated phosphorylation also prevents PREX2 membrane localization, constituting a negative feedback loop on Rac1 signaling downstream of insulin.\",\n      \"method\": \"In vitro GEF assays, cell fractionation, mass spectrometry phosphosite identification, PAK inhibitor experiments, insulin stimulation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro GEF assay combined with fractionation, MS phosphosite mapping, and mechanistic epistasis\",\n      \"pmids\": [\"26438819\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"GNMT interacts with PREX2 and promotes its degradation through an HectH9 (HUWE1) E3 ligase-mediated proteasomal ubiquitination pathway. Depletion of GNMT or HectH9 leads to elevated PREX2 protein and AKT activation.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown, protein stability assays\",\n      \"journal\": \"International journal of cancer\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, ubiquitination assays, and genetic perturbation with defined pathway phenotype\",\n      \"pmids\": [\"28205209\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Crystal structure of the P-Rex2 PH domain at 1.9 Å reveals conformational differences in loop regions compared to P-Rex1. The P-Rex2 PH domain binds PIP3 similarly to P-Rex1, and PIP3 binding is critical for P-Rex2 GEF activity but not membrane localization.\",\n      \"method\": \"X-ray crystallography, biochemical PIP3 binding assays\",\n      \"journal\": \"Journal of structural biology: X\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure at 1.9 Å combined with biochemical functional validation\",\n      \"pmids\": [\"34958187\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The PREX2 gain-of-function mutation S1113R, identified in HCC, enhances PREX2 protein stability by impairing HectH9-mediated ubiquitination, promotes cell migration, and activates the AKT pathway.\",\n      \"method\": \"Protein half-life assays, ubiquitination assays, cell migration assays, AKT phosphorylation western blot\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple functional assays in single study\",\n      \"pmids\": [\"30796242\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"CELF2 interacts with PREX2 and reduces the association of PREX2 with PTEN, thereby upregulating PTEN phosphatase activity and repressing AKT phosphorylation. This represents a mechanism by which CELF2 antagonizes the oncogenic effect of PREX2.\",\n      \"method\": \"Co-immunoprecipitation, PTEN phosphatase activity assay, AKT phosphorylation assay, PDX tumor model\",\n      \"journal\": \"Carcinogenesis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP, enzymatic activity assay, and in vivo validation in single study\",\n      \"pmids\": [\"31241130\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Cross-linking mass spectrometry and functional studies revealed the structural basis of PTEN:P-Rex2 complex assembly: PTEN is anchored to P-Rex2 via interactions between the PTEN C-terminal PDZ-interacting motif and the second PDZ domain of P-Rex2, bridging PTEN across the P-Rex2 surface to prevent PI(3,4,5)P3 hydrolysis. Conversely, PTEN allosterically promotes an autoinhibited P-Rex2 conformation and blocks Gβγ binding to P-Rex2.\",\n      \"method\": \"Cross-linking mass spectrometry, functional GEF and phosphatase activity assays, mutagenesis\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — cross-linking MS structural data combined with functional mutagenesis and activity assays\",\n      \"pmids\": [\"33947796\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"P-Rex2 mediates synaptic plasticity in bone cancer pain by activating Rac1 and phosphorylating GluR1, promoting GluR1-containing AMPA receptor trafficking and spine morphology changes in dorsal horn neurons.\",\n      \"method\": \"RNAi lentivirus knockdown in vivo, western blot for p-Rac1 and p-GluR1, spine counting, patch-clamp electrophysiology\",\n      \"journal\": \"Molecular pain\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo knockdown with multiple readouts including electrophysiology\",\n      \"pmids\": [\"35083941\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PREX2 promotes radioresistance in colorectal cancer by facilitating DNA repair through upregulation of DNA-PKcs and suppressing radiation-induced immunogenic cell death by inhibiting the cGAS/STING/IFNs pathway, thereby impeding CD8+ T cell infiltration.\",\n      \"method\": \"RNA-seq, colony formation assay, comet assay, apoptosis assay, western blot, xenograft mouse models, PREX2 inhibitor (PREX-in1)\",\n      \"journal\": \"BMC medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal in vitro and in vivo methods in single study\",\n      \"pmids\": [\"38609982\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"AHCYL1 is a novel PREX2-interacting protein that enhances PREX2 GEF activity toward RAC1 by alleviating the mutual inhibition between PREX2 and PTEN.\",\n      \"method\": \"Pull-down assay, LC-MS/MS, in vitro GEF assay, active RAC1 pull-down assay, western blotting\",\n      \"journal\": \"Theranostics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro GEF assay and pull-down combined with MS identification in single study\",\n      \"pmids\": [\"40365293\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"P-Rex2 suppresses glucose uptake into liver and skeletal muscle independently of its Rac-GEF catalytic activity (demonstrated using catalytically-inactive Prex2GD knockin mice). In hepatocytes, P-Rex2 suppresses Glut2 surface levels and mitochondrial ATP production, and controls trafficking of the orphan GPCR Gpr21. In skeletal muscle, P-Rex2 suppresses glucose uptake via a separate adaptor function independent of Gpr21.\",\n      \"method\": \"Prex2 knockout and catalytically-inactive Prex2GD knockin mice, glucose uptake assays, Glut2 surface assay, mitochondrial membrane potential assay, Gpr21 trafficking assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — catalytically-inactive knockin combined with KO mouse clearly dissects GEF-dependent vs. adaptor functions with multiple orthogonal cellular readouts\",\n      \"pmids\": [\"40764335\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Genetic loss of PREX2 in BRAF-mutant melanoma confers sensitivity to MAPK pathway inhibitors, and PREX2 acts upstream of RAC1 and PI3Kβ in a druggable signaling axis; pharmacological PI3Kβ inhibition phenocopies PREX2 deficiency.\",\n      \"method\": \"Genetically engineered mouse models, patient-derived melanoma cell lines, genetic and pharmacologic PI3Kβ inhibition, BRAF inhibitor sensitivity assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in mouse models and patient-derived lines with pharmacologic validation\",\n      \"pmids\": [\"39636745\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Cryo-EM structure of full-length P-Rex2 reveals that while the overall structure resembles P-Rex1, there is a substantial repositioning of the N-terminal module relative to the C-terminal core, potentially precluding the intramolecular N-terminal/C-terminal interactions seen in autoinhibited P-Rex1. HDX-MS shows P-Rex2 dynamics are unaffected by IP4 (PIP3 headgroup), unlike P-Rex1, suggesting a distinct autoinhibition mechanism.\",\n      \"method\": \"Cryo-EM, hydrogen-deuterium exchange mass spectrometry (HDX-MS), SEC-SAXS, biochemical GEF assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structure with HDX-MS and biochemistry, but preprint not yet peer-reviewed\",\n      \"pmids\": [\"41542420\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"PREX2 is a PIP3- and Gβγ-activated Rac1 GEF that forms a mutual inhibitory complex with the tumor suppressor PTEN (anchored via PTEN's PDZ-interacting motif binding the second PDZ domain of PREX2), whereby PTEN allosterically autoinhibits PREX2 and blocks Gβγ binding while PREX2's PH domain inhibits PTEN's phosphatase activity; this complex is subject to feedback regulation by PAK-mediated phosphorylation of PREX2 (reducing its PIP3/Gβγ binding and membrane localization), proteasomal degradation via HectH9-mediated ubiquitination promoted by GNMT, and positive modulation by AHCYL1; cancer-associated PREX2 mutations escape PTEN-mediated inhibition to drive constitutive RAC1/PI3K-AKT signaling, while physiologically PREX2 regulates cerebellar Purkinje cell morphology, glucose homeostasis (suppressing hepatic and skeletal muscle glucose uptake through GEF-independent adaptor functions), and synaptic plasticity.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PREX2 is a PIP3- and Gβγ-activated guanine-nucleotide exchange factor (GEF) for RAC1 that integrates PI3K and G-protein signaling to regulate cytoskeletal remodeling, insulin/glucose metabolism, and synaptic plasticity. PREX2 forms a mutual inhibitory complex with PTEN, in which the PREX2 PH domain blocks PTEN phosphatase activity while PTEN allosterically promotes PREX2 autoinhibition and occludes Gβγ binding, with PTEN anchored via its C-terminal PDZ-interacting motif to the second PDZ domain of PREX2 [PMID:33947796, PMID:24367090, PMID:25829446]; this complex is positively modulated by AHCYL1 [PMID:40365293] and negatively regulated by PAK-mediated phosphorylation that reduces PREX2 membrane recruitment [PMID:26438819] and GNMT/HectH9-mediated proteasomal degradation [PMID:28205209]. In vivo, PREX2 is required for cerebellar Purkinje cell dendrite morphology and motor coordination [PMID:18334636], and suppresses hepatic and skeletal-muscle glucose uptake through a GEF-independent adaptor function controlling GLUT2 surface levels and GPR21 trafficking [PMID:40764335]. Cancer-associated PREX2 mutations escape PTEN-mediated inhibition to drive constitutive RAC1/PI3K–AKT signaling and confer resistance to MAPK pathway inhibitors in melanoma [PMID:25829446, PMID:39636745].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Establishing the core enzymatic identity of PREX2 as a Rac-GEF synergistically activated by PIP3 and Gβγ answered the fundamental question of what this multi-domain protein does biochemically and placed it at the intersection of PI3K and GPCR signaling.\",\n      \"evidence\": \"In vitro and in vivo GEF activity assays with PIP3/Gβγ stimulation, reported simultaneously by two independent groups\",\n      \"pmids\": [\"15304343\", \"15304342\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Substrate specificity beyond Rac1 not tested\", \"Structural basis of PIP3/Gβγ synergy unknown\", \"Tissue-specific functions uncharacterized\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Generation of P-Rex2 knockout mice revealed its first physiological role — maintaining Purkinje cell dendrite morphology and motor coordination — demonstrating that PREX2 is not redundant with the related P-Rex1 in the cerebellum.\",\n      \"evidence\": \"P-Rex2 knockout and P-Rex1/P-Rex2 double-knockout mice with histological and behavioral analysis\",\n      \"pmids\": [\"18334636\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the Purkinje cell phenotype is Rac1-GEF-dependent or adaptor-mediated was not distinguished\", \"Downstream effectors in dendrite morphogenesis not identified\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"The discovery that PREX2 binds and inhibits PTEN, and that PREX2 is recurrently mutated in melanoma, reframed the gene as an oncogenic regulator of the PI3K/AKT axis rather than solely a Rac-GEF.\",\n      \"evidence\": \"Whole-genome sequencing of melanomas; ectopic PREX2 expression in NRAS-mutant melanocytes with in vivo tumor formation assay\",\n      \"pmids\": [\"22622578\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Independent replication of tumor acceleration failed\", \"Whether PTEN inhibition or Rac activation drives tumorigenic phenotype was unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Mapping the two-interface interaction between PREX2 and PTEN (PH domain–PTEN catalytic region and IP4P domain–PTEN PDZ-binding domain), and showing that Prex2 loss increases PTEN activity and impairs insulin signaling in vivo, established the molecular logic of mutual inhibition and its metabolic relevance.\",\n      \"evidence\": \"Domain mapping, co-immunoprecipitation, Prex2 knockout mouse with insulin signaling and glucose uptake assays\",\n      \"pmids\": [\"24367090\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural resolution of the interface lacking\", \"Mechanism linking PTEN C-terminal phosphorylation to PH domain release incompletely defined\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Two studies resolved opposite arms of the mutual inhibition: PTEN inhibits PREX2 GEF activity via its C-terminal tail (independently of phosphatase activity), and cancer-derived PREX2 mutants escape this inhibition; simultaneously, PAK-mediated phosphorylation of PREX2 was identified as a negative feedback loop that reduces PIP3/Gβγ binding and membrane localization after Rac1 activation.\",\n      \"evidence\": \"In vitro fluorescent nucleotide exchange assays with mutant panels, cell invasion assays; in vitro GEF assays with PAK phosphorylation, mass spectrometry phosphosite mapping, cell fractionation\",\n      \"pmids\": [\"25829446\", \"26438819\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"PAK phosphorylation sites not mapped to structural domains\", \"Whether PTEN tail inhibition is allosteric or steric was unclear\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identification of GNMT–HectH9(HUWE1)-mediated proteasomal ubiquitination as the mechanism controlling PREX2 protein turnover added a proteostatic regulatory layer and explained how GNMT suppresses AKT signaling.\",\n      \"evidence\": \"Reciprocal co-immunoprecipitation, ubiquitination assays, siRNA knockdown of GNMT and HectH9\",\n      \"pmids\": [\"28205209\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Ubiquitination sites on PREX2 not mapped\", \"Whether ubiquitination is constitutive or signal-regulated not determined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"The 1.9 Å crystal structure of the P-Rex2 PH domain showed that PIP3 binding is essential for GEF activity but not membrane localization, distinguishing lipid-dependent activation from membrane targeting.\",\n      \"evidence\": \"X-ray crystallography and biochemical PIP3 binding assays\",\n      \"pmids\": [\"34958187\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of remaining domains and full-length protein not resolved\", \"PIP3-induced conformational changes in the DH-PH tandem not visualized\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Cross-linking mass spectrometry of the PTEN–P-Rex2 complex provided a near-complete structural model of their mutual inhibition: PTEN's PDZ-interacting motif anchors to the second PDZ domain of P-Rex2, positioning PTEN to block PIP3 hydrolysis, while PTEN allosterically stabilizes P-Rex2 autoinhibition and blocks Gβγ binding.\",\n      \"evidence\": \"Cross-linking mass spectrometry, functional GEF and phosphatase activity assays with targeted mutations\",\n      \"pmids\": [\"33947796\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"High-resolution atomic model of the full complex not available\", \"Dynamics of complex assembly and disassembly upon signaling not characterized\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"PREX2's role was extended to synaptic plasticity, showing that P-Rex2 activates Rac1 in dorsal horn neurons to phosphorylate GluR1 and promote AMPA receptor trafficking during bone cancer pain, establishing a neuronal signaling function beyond cerebellum.\",\n      \"evidence\": \"In vivo lentiviral knockdown, patch-clamp electrophysiology, spine morphology analysis in dorsal horn neurons\",\n      \"pmids\": [\"35083941\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct GEF activity measurement in these neurons lacking\", \"Relevance to non-pain synaptic plasticity not tested\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Use of catalytically-inactive Prex2 knockin mice demonstrated that PREX2 suppresses glucose uptake in liver and skeletal muscle through a GEF-independent adaptor function, controlling GLUT2 surface levels and GPR21 trafficking — a fundamentally new mode of action for PREX2.\",\n      \"evidence\": \"Prex2 KO and catalytically-inactive Prex2GD knockin mice with glucose uptake, GLUT2 surface, mitochondrial ATP, and GPR21 trafficking assays\",\n      \"pmids\": [\"40764335\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Adaptor-binding partners mediating GLUT2/GPR21 trafficking not identified\", \"How GEF-independent and GEF-dependent functions are coordinated in vivo unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Genetic loss of PREX2 sensitizes BRAF-mutant melanoma to MAPK inhibitors, with PI3Kβ inhibition phenocopying PREX2 deficiency, defining a druggable PREX2–RAC1–PI3Kβ signaling axis in therapy resistance.\",\n      \"evidence\": \"Genetically engineered mouse melanoma models, patient-derived cell lines, pharmacologic PI3Kβ inhibition\",\n      \"pmids\": [\"39636745\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether PREX2 directly activates PI3Kβ or acts via RAC1 not resolved\", \"Clinical validation in patient cohorts lacking\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A high-resolution structure of the full-length PREX2–PTEN complex and the molecular basis of PREX2's GEF-independent adaptor functions remain the central unresolved mechanistic questions.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No atomic-resolution structure of full-length PREX2 in complex with PTEN\", \"Adaptor-mode binding partners and structural basis for GLUT2/GPR21 regulation unknown\", \"In vivo regulation of PREX2 at different tissues (brain vs. liver vs. muscle) not integrated\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 5, 6, 8, 14]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [15]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [4, 5, 10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [6, 8]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 4, 5, 6, 11, 14, 16]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [3, 9, 13, 16]}\n    ],\n    \"complexes\": [\n      \"PREX2–PTEN complex\"\n    ],\n    \"partners\": [\n      \"PTEN\",\n      \"RAC1\",\n      \"PAK1\",\n      \"GNMT\",\n      \"HUWE1\",\n      \"AHCYL1\",\n      \"CELF2\",\n      \"GPR21\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}