{"gene":"PTP4A1","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":1994,"finding":"PRL-1 encodes a 20-kDa protein tyrosine phosphatase with a conserved active-site cysteine; mutation of this active-site cysteine abolishes phosphatase activity. PRL-1 can dephosphorylate phosphotyrosine substrates in vitro and is located primarily in the cell nucleus. Overexpression causes altered cellular growth, morphology, and transformed phenotype.","method":"Active-site mutagenesis (Cys→Ala), in vitro phosphatase assay, nuclear localization by subcellular fractionation/immunofluorescence, stable transfection overexpression","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro enzymatic assay with active-site mutagenesis, nuclear localization demonstrated directly, overexpression phenotype established; foundational paper replicated by subsequent work","pmids":["8196618"],"is_preprint":false},{"year":2000,"finding":"PRL-1 is prenylated (farnesylated) at its C-terminal CAAX motif, and this prenylation is required for its primary association with the plasma membrane and early endosomal compartment. When farnesylation is inhibited by FTI-277 or the CAAX motif is mutated, PRL-1 relocalizes to the nucleus.","method":"Metabolic labeling for prenylation, immunofluorescence and electron microscope immunogold labeling, farnesyltransferase inhibitor (FTI-277) treatment, C-terminal prenylation mutant expression, brefeldin A and wortmannin treatments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (immunogold EM, pharmacological inhibition, mutagenesis) in one study; prenylation-dependent membrane localization replicated across PRL family","pmids":["10747914"],"is_preprint":false},{"year":2002,"finding":"PRL-1 localizes to the endoplasmic reticulum in a farnesylation-dependent manner in non-mitotic cells, and relocalizes to centrosomes and the mitotic spindle (farnesylation-independently) during mitosis. Expression of a catalytic domain mutant delays mitotic progression; expression of a farnesylation-site mutant causes chromosomal bridges and lagging chromosomes in anaphase without affecting spindle checkpoint function.","method":"Immunofluorescence of endogenous PRL-1 across cell cycle stages, conditional expression of catalytic mutant and farnesylation mutant in HeLa cells, cell cycle analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct localization experiments with functional consequence (mitotic defects), catalytic and farnesylation mutants tested in same study","pmids":["12235145"],"is_preprint":false},{"year":2003,"finding":"PRL-1 expression in CHO cells enhances cell motility and invasive activity; catalytically inactive PRL-1 mutant has significantly reduced migration-promoting activity. PRL-1-expressing cells, but not controls, form metastatic tumors in mice.","method":"Stable CHO cell lines, motility and invasion assays, catalytically inactive mutant, in vivo mouse metastasis model","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — catalytic mutant used to establish enzyme-activity dependence of migration; in vivo metastasis confirmed; replicated across PRL-1 and PRL-3","pmids":["12782572"],"is_preprint":false},{"year":2005,"finding":"Crystal structure of PRL-1 reveals it forms a trimer burying ~1140 Ų per dimer interface, creating a membrane-binding surface. The active site places PRL-1 among dual-specificity phosphatases with closest structural similarity to Cdc14. Native PRL-1 crystallizes in an oxidized form where an intramolecular disulfide between active-site Cys104 and neighboring Cys49 blocks substrate binding and catalysis; biochemical and cell-based studies confirm this disulfide as a redox regulatory mechanism.","method":"X-ray crystallography (native and C104S mutant with sulfate), kinetic analysis, biochemical disulfide assays in solution and in cells","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with mutagenesis and in vitro kinetics plus cell-based validation; independent replication of Cys49–Cys104 disulfide regulatory mechanism","pmids":["16142898"],"is_preprint":false},{"year":2005,"finding":"Crystal structure of human PRL-1 at 2.7 Å shows a shallow, hydrophobic active-site pocket with a sulfate ion stabilizing the active conformation. PRL-1 forms a trimer in the crystal, and a trimer is also detected in the membrane fraction of cells, suggesting oligomerization may regulate PRL-1 activity.","method":"X-ray crystallography (2.7 Å), cell fractionation to detect trimers in membrane fraction","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with independent biochemical confirmation of trimer in cell membrane fraction; corroborates Sun et al. 2005","pmids":["15571731"],"is_preprint":false},{"year":2001,"finding":"PRL-1 physically interacts with the transcription factor ATF-7 (a bZIP protein related to ATF/CREB family); the interaction was mapped to ATF-7's bZIP region and PRL-1's phosphatase domain. PRL-1 can dephosphorylate ATF-7 in vitro.","method":"Yeast two-hybrid, domain-mapping, in vitro dephosphorylation assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid confirmed with domain mapping and in vitro phosphatase assay on substrate; single lab, two orthogonal methods","pmids":["11278933"],"is_preprint":false},{"year":1999,"finding":"Egr-1 directly binds the proximal PRL-1 promoter and transactivates PRL-1 gene expression in response to mitogen stimulation and partial hepatectomy; mutation of the Egr-1 site abolishes this induction.","method":"Electrophoretic mobility shift assay (EMSA), reporter gene assays with wild-type and mutant Egr-1 site, Northern blot of regenerating liver","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding (EMSA) and functional reporter with point mutation; single lab, two orthogonal methods","pmids":["9988683"],"is_preprint":false},{"year":2007,"finding":"PRL-1 knockdown in A549 lung cancer cells decreases c-Src and p130Cas expression, reduces Rac1 and Cdc42 activation, and elevates FAK Tyr397 phosphorylation, resulting in reduced invasion and increased cell-substrate adhesion. These results place PRL-1 upstream of c-Src, Rac1, and Cdc42 in adhesion/invasion signaling.","method":"Stable shRNA knockdown, invasion and adhesion assays, Western blot for c-Src/p130Cas/FAK phosphorylation, GTPase activation assays, immunofluorescence","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KD with multiple downstream readouts and specific phenotypic outcome; single lab","pmids":["17234774"],"is_preprint":false},{"year":2008,"finding":"PRL-1 overexpression reduces p53 protein levels through ubiquitination and proteasomal degradation, achieved via two independent pathways: induction of PIRH2 transcription and MDM2 phosphorylation through Akt signaling. Conversely, PRL-1 siRNA increases p53 levels. PRL-1 is itself transcriptionally regulated by p53 via a response element in the first intron, forming a negative feedback loop.","method":"Overexpression and siRNA knockdown, p53 ubiquitination assay, proteasome inhibitor experiments, reporter assays for PIRH2 and MDM2, identification of p53 response element","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple mechanistic approaches (ubiquitination, proteasome, Akt pathway, reporter assay) in single lab study","pmids":["18997816"],"is_preprint":false},{"year":2011,"finding":"PRL-1 binds the SH3 domain of p115 RhoGAP via a non-canonical interaction in which a PxxP ligand-binding groove of the SH3 domain occupies a folded groove within PRL-1. This interaction prevents p115 RhoGAP from binding MEKK1, thereby activating ERK1/2; simultaneously, PRL-1 binding inhibits the GAP activity of p115 RhoGAP, activating RhoA.","method":"Peptide binding/pulldown, co-IP in vitro and in cells, X-ray crystallography of PRL-1·peptide complex, GAP activity assay, ERK1/2 and RhoA activation assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure of complex plus in vitro GAP activity assay and cellular signaling readouts; multiple orthogonal methods demonstrating mechanism","pmids":["22009749"],"is_preprint":false},{"year":2016,"finding":"Crystal structure of PRL-1 in complex with the Bateman module (CBS domains) of CNNM2 reveals a heterotetrameric assembly: one CNNM2BAT homodimer bound to two independent PRL-1 molecules. The interaction is mediated via PRL-1's catalytic domain, with CNNM2 Asp-558 in the CBS2 loop being critical for the interface.","method":"X-ray crystallography of PRL-1–CNNM2BAT complex, mutagenesis of interface residues (Asp-558)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure of complex with mutagenesis validating key interface residue; mechanistically defines how PRL-1 engages CNNM2","pmids":["27899452"],"is_preprint":false},{"year":2017,"finding":"PTP4A1 promotes TGFβ signaling in dermal fibroblasts by enhancing ERK activity, which stimulates SMAD3 expression and nuclear translocation. Upstream from ERK, PTP4A1 directly interacts with SRC and inhibits basal SRC activation independently of its phosphatase activity. PTP4A2, by contrast, minimally interacts with SRC and does not promote this SRC-ERK-SMAD3 pathway.","method":"Co-IP of PTP4A1 with SRC, siRNA knockdown, TGFβ pathway readouts (SMAD3 nuclear translocation, target gene expression), bleomycin fibrosis mouse model, comparison with catalytically inactive mutant","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, phosphatase-dead mutant showing phosphatase-independent SRC binding, in vivo bleomycin model, multiple orthogonal methods; single lab but rigorous design","pmids":["29057934"],"is_preprint":false},{"year":2007,"finding":"PRL-1 phosphatase activity in retinal cones and cone-derived cells is reversibly inhibited by oxidative stress through formation of an intramolecular disulfide bond between active-site Cys104 and Cys49. This was observed in vitro, in cell culture, and in isolated retinas exposed to hydrogen peroxide.","method":"In vitro phosphatase activity assay under H2O2 treatment, cell culture oxidative stress experiments, isolated retina experiments, inhibition by glutathione system blockade","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple experimental contexts (in vitro, cells, retina tissue) confirming redox-dependent disulfide regulation; single lab, consistent with structural data","pmids":["17673310"],"is_preprint":false},{"year":2019,"finding":"Drosophila Prl-1 (ortholog of PRL-1) is an axon-intrinsic factor that promotes synapse formation in a spatially restricted manner on a specific axon collateral. Prl-1 modulates insulin receptor (InR) signaling within a single contralateral axon compartment to control synapse number. The axon branch-specific localization and function of Prl-1 depend on its mRNA untranslated regions.","method":"Loss-of-function genetics (Drosophila null mutants), overexpression of Prl-1, behavioral (locomotor) assays, genetic epistasis with InR pathway, mRNA UTR deletion analysis","journal":"Science","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean loss-of-function and gain-of-function in vivo with defined circuit phenotype, genetic epistasis placing Prl-1 in InR pathway, mechanistic UTR-localization link; high-quality Drosophila ortholog study","pmids":["31048465"],"is_preprint":false},{"year":2013,"finding":"In Drosophila, overexpression of PRL under normal conditions suppresses growth in a CAAX motif-dependent manner (requiring membrane localization at the apical lateral membrane), and PRL can counteract the oncogenic activity of Src. PRL lacking the CAAX motif retains the ability to inhibit Src function even when associating non-specifically with the plasma membrane.","method":"Transgenic Drosophila overexpression, CAAX motif deletion mutant, genetic epistasis with Src, tissue growth assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo transgenic Drosophila with CAAX mutant and genetic interaction with Src; single lab, multiple genetic tools","pmids":["23577193"],"is_preprint":false},{"year":2016,"finding":"PTP4A1 promotes proliferation and epithelial-mesenchymal transition in intrahepatic cholangiocarcinoma (ICC) via PI3K/AKT signaling; downstream effectors include phosphorylation of GSK3β, upregulation of CyclinD1, and EMT transcription factors Zeb1 and Snail.","method":"Forced overexpression and knockdown of PTP4A1 in ICC cells, in vitro proliferation/invasion assays, in vivo tumor model, Western blot for PI3K/AKT pathway components","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain- and loss-of-function with in vivo confirmation and defined downstream pathway; single lab","pmids":["27655691"],"is_preprint":false},{"year":2018,"finding":"PRL-1 redistributes to the immunological synapse (IS) in two stages during T cell activation: initially accumulating at scanning membranes enriched in CD3 and actin, then delivered from pericentriolar CD3ζ-containing vesicles. At the established IS, PRL-1 distributes to LFA-1 and CD3ε sites. PRL-1 regulates actin dynamics during IS assembly and IL-2 secretion; pharmacological inhibition of PRL catalytic activity reduces IL-2 secretion.","method":"Live imaging, immunofluorescence at immunological synapse, pharmacological inhibition of PRL phosphatase activity, IL-2 secretion assays","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct live-cell localization tied to functional actin and cytokine secretion readouts; single lab, two orthogonal methods","pmids":["30515156"],"is_preprint":false},{"year":2022,"finding":"PTP4A1 dephosphorylates cytohesin-2 at Tyr381, and this dephosphorylation negatively regulates Schwann cell myelination. The adaptor SH2B1 maintains Tyr381 phosphorylation, opposing PTP4A1. Schwann cell-specific knockdown of PTP4A1 increases cytohesin-2 phosphorylation and myelin thickness; SH2B1-specific loss reduces myelin thickness and cytohesin-2 phosphorylation. Knockin mice with Y381F (non-phosphorylatable) cytohesin-2 show reduced myelin thickness and Arf6 activity.","method":"In vitro dephosphorylation assay in HEK293T cells, Schwann cell-specific knockdown mice, cytohesin-2 Y381F knockin mice, myelin thickness measurements, Arf6 activity assay","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct substrate identification (Tyr381 of cytohesin-2), multiple in vivo genetic models (KD mice, knockin mice), opposing SH2B1/PTP4A1 regulation demonstrated with multiple orthogonal approaches","pmids":["35077201"],"is_preprint":false},{"year":2023,"finding":"PRL-1/2 counteract the CNNM family's inhibition of TRPM7 magnesium channel function. PRL-2 overexpression prevents CNNM3 from interacting with TRPM7, thereby enhancing TRPM7 activity and magnesium influx. ARL15 small GTPase promotes CNNM3/TRPM7 complex formation to reduce TRPM7 activity, and PRL-2 counteracts this. PRL-1/2 promote TRPM7-induced cell signaling; co-targeting TRPM7 and PRL-1/2 disrupts mitochondrial function and sensitizes cells to magnesium depletion.","method":"Genetically encoded intracellular magnesium reporter, co-IP for protein complex formation, overexpression/knockdown of PRL-1/2, CNNM3, ARL15, TRPM7; cell signaling and metabolic stress assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — novel magnesium reporter, multiple Co-IP experiments, overexpression/knockdown with functional metabolic readouts; defines mechanism of PRL-CNNM-TRPM7 axis with multiple orthogonal approaches","pmids":["36972446"],"is_preprint":false},{"year":2023,"finding":"PTP4A1 dephosphorylates USF1 at Ser309 in endothelial cells, increasing USF1 transcriptional activity. This induces TNFAIP3/A20 transcription and subsequent NF-κB inhibition, reducing cell adhesion molecule expression. Ptp4a1 knockout mice show exacerbated IL-1β-induced CAM expression; Ptp4a1 transgenic mice show reduced CAMs. PTP4A1 deficiency in ApoE KO mice worsens diet-induced atherogenesis.","method":"shRNA knockdown and overexpression in endothelial cells, Ptp4a1 KO and transgenic mice, chromatin immunoprecipitation, luciferase reporter assays, immunostaining, ApoE KO atherosclerosis model","journal":"Cardiovascular research","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct substrate (USF1 Ser309) identified, ChIP confirms transcriptional mechanism, multiple in vivo mouse models, reporter assays; multiple orthogonal methods","pmids":["36534975"],"is_preprint":false},{"year":2023,"finding":"PTP4A1 promotes hepatosteatosis prevention by activating the CREBH/FGF21 transcriptional axis. Ptp4a1 knockout mice develop exacerbated glucose dysregulation and hepatosteatosis on a high-fat diet; liver-specific PTP4A1 overexpression rescues this. Mechanistically, lipid accumulation in PTP4A1-deficient hepatocytes reduces GLUT2 at the plasma membrane, impairing glucose uptake.","method":"Ptp4a1 KO mice, adeno-associated virus liver-specific PTP4A1 expression, adenovirus FGF21 rescue, glucose/insulin tolerance tests, hyperinsulinemic-euglycemic clamp, co-IP, luciferase reporter assay","journal":"Theranostics","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple in vivo mouse models (KO, liver-specific OE, rescue with FGF21), co-IP for protein interaction, reporter assays, metabolic phenotyping; comprehensive mechanistic dissection","pmids":["36793871"],"is_preprint":false},{"year":2023,"finding":"PTP4A1 binds pyruvate kinase isoenzyme M2 (PKM2) to promote its expression and binds aconitase 2 (ACO2) to enhance its degradation, thereby regulating mitochondrial metabolic reprogramming and invasive capacity in OSCC cells.","method":"Co-IP of PTP4A1 with PKM2 and ACO2, overexpression/knockdown in OSCC cells, in vitro invasion assays, in vivo tumor model","journal":"Cell death discovery","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP for two novel binding partners with functional invasion phenotype; single lab, mechanistic detail limited in abstract","pmids":["37773151"],"is_preprint":false},{"year":2025,"finding":"Mutagenesis studies identify an aspartic acid (D72) and the backdoor cysteine (C49) in the PRL-1 catalytic site as required for phosphocysteine hydrolysis. A C49S/D72A double mutant stabilizes the phosphocysteine intermediate for weeks. The crystal structure of cysteine-phosphorylated PRL-1 (PTP4A1) confirms that phosphocysteine sterically interferes with CNNM binding. The D72A mutation increases initial catalytic rate for all three PRL paralogs, in contrast to the homologous mutation in PTP1B/PTPN12 which disrupts catalysis, revealing a mechanistic difference between PRLs and classical PTPs.","method":"Site-directed mutagenesis (C49S, D72A), in vitro enzyme assays, X-ray crystallography of phosphocysteine-intermediate form","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure of catalytic intermediate plus mutagenesis and in vitro enzyme kinetics; rigorous mechanistic dissection of catalysis and CNNM binding steric clash","pmids":["40398601"],"is_preprint":false},{"year":2025,"finding":"PTP4A1 promotes cancer–mesothelial cell adhesion in a peritoneal metastasis model; a small molecule inhibitor of PTP4A1 (CMPD-43) reduces RhoA activity and inhibits heterotypic cancer–mesothelial cell adhesion.","method":"Peritoneal mesothelial cell proteomics, heterotypic adhesion assay, small molecule inhibitor treatment, RhoA activity assay","journal":"Aging and cancer","confidence":"Medium","confidence_rationale":"Tier 3 / Weak — functional adhesion and RhoA assays with pharmacological inhibitor; single lab, limited mechanistic detail in abstract","pmids":["41769321"],"is_preprint":false},{"year":2025,"finding":"PTP4A1 physically interacts with PTEN (validated by co-IP and immunofluorescence), suppresses PTEN phosphorylation, and thereby promotes PI3K/AKT/GSK3α pathway activation to drive ICC cell proliferation, migration, and invasion.","method":"Co-immunoprecipitation, immunofluorescence co-localization, Western blot for PTEN phosphorylation and PI3K/AKT pathway, in vitro and in vivo functional assays","journal":"Oncology reports","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP and immunofluorescence confirming PTP4A1-PTEN interaction with downstream pathway readout; single lab, two orthogonal methods for interaction","pmids":["40747713"],"is_preprint":false},{"year":2024,"finding":"PTP4A1 is catalytically active in its reduced form. The oxidized form (Cys104-Cys49 disulfide) retains biological function by forming a kinase-phosphatase complex with Src kinases, establishing a phosphatase-activity-independent function for oxidized PTP4A1 in systemic sclerosis.","method":"Preparation and characterization of oxidized and reduced PTP4A1 protein forms, complex formation assay with Src kinase, functional studies in SSc context","journal":"Methods in molecular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical preparation and complex formation studies; single lab, methods paper but with functional validation of oxidized form/Src complex","pmids":["38147218"],"is_preprint":false}],"current_model":"PTP4A1 (PRL-1) is a small, farnesylated dual-specificity phosphatase that cycles between the endoplasmic reticulum/plasma membrane/early endosomes (prenylation-dependent) and the nucleus or mitotic spindle (cell-cycle regulated); its catalytic Cys104 is reversibly inactivated by a Cys49-Cys104 intramolecular disulfide under oxidative stress, while a D72 general-acid residue is required for phosphocysteine hydrolysis via a mechanism distinct from classical PTPs; mechanistically, PTP4A1 activates ERK1/2 and RhoA by binding p115 RhoGAP, promotes TGFβ/SMAD3 fibrotic signaling by forming a phosphatase-activity-independent complex with SRC, dephosphorylates USF1-Ser309 to drive A20/NF-κB anti-inflammatory signaling in endothelial cells, dephosphorylates cytohesin-2-Tyr381 to negatively regulate Schwann cell myelination, dephosphorylates ATF-7 as a nuclear substrate, upregulates CREBH/FGF21 to prevent hepatosteatosis, counteracts CNNM-mediated inhibition of the TRPM7 magnesium channel to regulate intracellular magnesium and cellular metabolism, interacts structurally with CNNM2 via a heterotetrameric interface (catalytic domain of PRL-1 binding CBS2 of CNNM2), and promotes cell migration, invasion, and metastasis in a catalytic-activity-dependent manner—collectively placing PTP4A1 at the nexus of growth-factor signaling, metabolic homeostasis, cytoskeletal regulation, and magnesium transport."},"narrative":{"mechanistic_narrative":"PTP4A1 (PRL-1) is a small, farnesylated dual-specificity protein phosphatase that couples growth-factor and cytoskeletal signaling, magnesium homeostasis, and metabolic control, and acts as a positive regulator of cell motility, invasion, and metastasis in a catalytic-activity-dependent manner [PMID:8196618, PMID:12782572]. Its C-terminal CAAX farnesylation directs association with the plasma membrane, early endosomes, and the endoplasmic reticulum, whereas loss of prenylation redirects the protein to the nucleus; during mitosis it relocalizes farnesylation-independently to centrosomes and the spindle, where catalytic and prenylation mutants cause mitotic delay and chromosome segregation defects [PMID:10747914, PMID:12235145]. Crystallographic and kinetic work shows PTP4A1 forms membrane-binding trimers and that catalysis proceeds through a phosphocysteine intermediate requiring active-site Cys104 plus an unusual general-acid Asp72 and backdoor Cys49, a mechanism distinct from classical PTPs; the same Cys49–Cys104 pair forms an intramolecular disulfide that reversibly inactivates the enzyme under oxidative stress [PMID:16142898, PMID:17673310, PMID:40398601]. Beyond catalysis, PTP4A1 acts through direct protein interactions: it binds the SH3 domain of p115 RhoGAP via a non-canonical interface to activate ERK1/2 and RhoA [PMID:22009749], binds SRC in a phosphatase-independent manner to drive ERK/SMAD3-dependent TGFβ fibrotic signaling [PMID:29057934], and engages the CBS/Bateman module of CNNM2/CNNM3 through its catalytic domain to counteract CNNM-mediated inhibition of the TRPM7 magnesium channel, thereby controlling intracellular magnesium and mitochondrial metabolism [PMID:27899452, PMID:36972446]. PTP4A1 also has defined dephosphorylation substrates with tissue-specific outputs: it dephosphorylates cytohesin-2 at Tyr381 to negatively regulate Schwann cell myelination [PMID:35077201] and dephosphorylates USF1 at Ser309 to induce A20 and restrain endothelial NF-κB-driven inflammation and atherogenesis [PMID:36534975], and it activates a CREBH/FGF21 axis in liver to prevent diet-induced hepatosteatosis and glucose dysregulation [PMID:36793871]. In cancer contexts it promotes proliferation, EMT, and invasion through PI3K/AKT signaling and PTEN suppression [PMID:27655691, PMID:40747713].","teleology":[{"year":1994,"claim":"Established PRL-1 as a bona fide protein tyrosine phosphatase whose enzymatic activity drives altered growth, answering whether the immediate-early gene encoded a functional catalytic enzyme.","evidence":"Active-site Cys→Ala mutagenesis, in vitro phosphatase assay, and overexpression in transfected cells with nuclear localization","pmids":["8196618"],"confidence":"High","gaps":["No physiological substrate identified","Mechanism linking activity to transformed phenotype unresolved"]},{"year":1999,"claim":"Identified how PRL-1 expression is induced, showing Egr-1 directly transactivates the promoter during mitogenic and regenerative stimulation.","evidence":"EMSA, reporter assays with mutated Egr-1 site, Northern blot of regenerating liver","pmids":["9988683"],"confidence":"Medium","gaps":["Does not address protein-level regulation or downstream targets","Single-lab transcriptional study"]},{"year":2000,"claim":"Defined the basis of PRL-1 membrane targeting, establishing that C-terminal farnesylation governs plasma-membrane/endosomal localization versus default nuclear localization.","evidence":"Metabolic prenylation labeling, immunogold EM, FTI-277 inhibition, and CAAX mutagenesis","pmids":["10747914"],"confidence":"High","gaps":["Functional consequence of each localization not fully resolved","Trafficking machinery unidentified"]},{"year":2001,"claim":"Provided the first candidate nuclear substrate by mapping a direct interaction with transcription factor ATF-7 and showing in vitro dephosphorylation.","evidence":"Yeast two-hybrid, domain mapping, in vitro dephosphorylation assay","pmids":["11278933"],"confidence":"Medium","gaps":["Physiological relevance in cells not established","ATF-7 phosphosite not defined"]},{"year":2002,"claim":"Connected localization to cell-cycle function, showing PRL-1 moves to centrosomes/spindle in mitosis and that catalytic and farnesylation mutants cause mitotic defects.","evidence":"Endogenous immunofluorescence across cell cycle, conditional catalytic and CAAX mutant expression in HeLa","pmids":["12235145"],"confidence":"High","gaps":["Mitotic substrate unknown","Mechanism of spindle recruitment unresolved"]},{"year":2003,"claim":"Demonstrated that PRL-1 catalytic activity is required for pro-motility and metastatic behavior, linking the enzyme to cancer cell invasion in vivo.","evidence":"Stable CHO lines, motility/invasion assays, catalytically inactive mutant, mouse metastasis model","pmids":["12782572"],"confidence":"High","gaps":["Direct substrate driving migration not identified","Pathway intermediates undefined at this stage"]},{"year":2005,"claim":"Resolved the structure and redox regulation of the catalytic domain, defining a membrane-binding trimer and a Cys49–Cys104 disulfide that blocks catalysis.","evidence":"X-ray crystallography of native and mutant PRL-1, kinetics, and cell-based disulfide assays","pmids":["16142898","15571731"],"confidence":"High","gaps":["Physiological trigger of oxidation in vivo not yet defined","Functional role of trimerization in cells unclear"]},{"year":2007,"claim":"Placed PRL-1 upstream in adhesion/invasion signaling and confirmed oxidative-stress regulation in a native tissue context.","evidence":"shRNA knockdown in A549 with Src/Rac1/Cdc42/FAK readouts; H2O2 disulfide experiments in cells and isolated retina","pmids":["17234774","17673310"],"confidence":"Medium","gaps":["Direct dephosphorylation events not established in the invasion pathway","Redox studies single-lab"]},{"year":2008,"claim":"Identified a p53 feedback loop, showing PRL-1 lowers p53 via PIRH2 and Akt/MDM2 while p53 transcriptionally controls PRL-1.","evidence":"Overexpression/siRNA, ubiquitination and proteasome assays, reporter assays, p53 response element mapping","pmids":["18997816"],"confidence":"Medium","gaps":["Direct phosphatase substrate in the pathway not defined","Single-lab mechanistic study"]},{"year":2011,"claim":"Defined a non-catalytic scaffolding mechanism whereby PRL-1 binds the p115 RhoGAP SH3 domain to simultaneously activate ERK1/2 and RhoA.","evidence":"Peptide binding, co-IP, crystallography of PRL-1·peptide complex, GAP and signaling assays","pmids":["22009749"],"confidence":"High","gaps":["In vivo physiological output of this complex not addressed","Interplay with catalytic substrates unresolved"]},{"year":2013,"claim":"Showed in Drosophila that membrane-localized PRL suppresses growth and antagonizes Src, with CAAX-independent Src inhibition revealing functional complexity.","evidence":"Transgenic overexpression, CAAX deletion mutant, genetic epistasis with Src","pmids":["23577193"],"confidence":"Medium","gaps":["Direct biochemical link to Src not defined here","Reconciliation with pro-oncogenic roles in mammals incomplete"]},{"year":2016,"claim":"Defined the structural basis of CNNM engagement, showing the PRL-1 catalytic domain binds the CNNM2 Bateman module in a heterotetramer.","evidence":"X-ray crystallography of PRL-1–CNNM2BAT complex with interface mutagenesis (Asp-558)","pmids":["27899452"],"confidence":"High","gaps":["Functional output of the complex not yet established in this study","Competition with substrate binding unresolved here"]},{"year":2016,"claim":"Extended PRL-1 oncogenic signaling to PI3K/AKT, linking it to proliferation and EMT in cholangiocarcinoma.","evidence":"Overexpression/knockdown in ICC cells, in vivo tumor model, Western blot of AKT/GSK3β/CyclinD1/Zeb1/Snail","pmids":["27655691"],"confidence":"Medium","gaps":["Mechanism connecting PTP4A1 to PI3K/AKT not defined here","Direct substrate unidentified"]},{"year":2017,"claim":"Established a phosphatase-independent SRC-binding mechanism driving TGFβ/ERK/SMAD3 fibrotic signaling and distinguished PTP4A1 from PTP4A2.","evidence":"Reciprocal co-IP, phosphatase-dead mutant, SMAD3 readouts, bleomycin fibrosis mouse model","pmids":["29057934"],"confidence":"High","gaps":["Structural basis of PTP4A1-SRC binding not resolved","How catalytic and scaffolding roles are balanced unclear"]},{"year":2018,"claim":"Localized PRL-1 to the immunological synapse and tied its activity to actin dynamics and IL-2 secretion in T cells.","evidence":"Live imaging, IS immunofluorescence, pharmacological PRL inhibition, IL-2 assays","pmids":["30515156"],"confidence":"Medium","gaps":["No T-cell substrate identified","Inhibitor specificity caveats"]},{"year":2019,"claim":"Showed in Drosophila that Prl-1 modulates insulin-receptor signaling in an axon-branch-specific, UTR-dependent manner to control synapse number.","evidence":"Loss/gain-of-function genetics, InR epistasis, mRNA UTR deletion, locomotor assays","pmids":["31048465"],"confidence":"High","gaps":["Mammalian relevance of neuronal role untested in corpus","Biochemical InR-pathway substrate undefined"]},{"year":2022,"claim":"Identified cytohesin-2 Tyr381 as a direct substrate and placed PTP4A1 opposite SH2B1 in negative control of Schwann cell myelination.","evidence":"In vitro dephosphorylation, Schwann cell-specific KD mice, cytohesin-2 Y381F knockin mice, Arf6 activity assays","pmids":["35077201"],"confidence":"High","gaps":["Upstream signals controlling PTP4A1 in Schwann cells unknown","Generalization to other myelinating contexts untested"]},{"year":2023,"claim":"Defined multiple in vivo physiological substrates and axes — USF1-Ser309/A20/NF-κB in endothelial anti-inflammation, CREBH/FGF21 in hepatosteatosis prevention, and PRL-CNNM-TRPM7 in magnesium/metabolic control.","evidence":"KO and transgenic/liver-specific OE mice, ChIP and reporter assays, magnesium reporter, co-IP, atherosclerosis and metabolic models","pmids":["36534975","36793871","36972446","37773151"],"confidence":"High","gaps":["Tissue specificity of substrate selection mechanism unclear","How a single phosphatase coordinates these distinct programs unresolved"]},{"year":2024,"claim":"Demonstrated that the oxidized, catalytically inactive form retains biological function by forming a phosphatase-independent complex with Src kinases.","evidence":"Biochemical preparation of oxidized/reduced forms and Src complex assays in systemic sclerosis context","pmids":["38147218"],"confidence":"Medium","gaps":["Single-lab biochemical characterization","In vivo relevance of the oxidized-Src complex not fully established"]},{"year":2025,"claim":"Dissected the unusual catalytic mechanism (Asp72 general acid, backdoor Cys49, phosphocysteine intermediate) and showed it differs from classical PTPs and sterically gates CNNM binding.","evidence":"C49S/D72A mutagenesis, in vitro kinetics, crystal structure of phosphocysteine intermediate","pmids":["40398601"],"confidence":"High","gaps":["Physiological control of the catalytic-vs-CNNM-binding switch 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Nucleic acids","url":"https://pubmed.ncbi.nlm.nih.gov/36865088","citation_count":3,"is_preprint":false},{"pmid":"19636948","id":"PMC_19636948","title":"1H, 15N, 13C resonance assignments of the reduced and active form of human Protein Tyrosine Phosphatase, PRL-1.","date":"2009","source":"Biomolecular NMR assignments","url":"https://pubmed.ncbi.nlm.nih.gov/19636948","citation_count":3,"is_preprint":false},{"pmid":"38134119","id":"PMC_38134119","title":"Expression of PTP4A1 in circulating tumor cells and its efficacy evaluation in patients with early- and intermediate-stage esophageal cancer.","date":"2023","source":"Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/38134119","citation_count":2,"is_preprint":false},{"pmid":"41322418","id":"PMC_41322418","title":"GINS2 promotes oral squamous cell carcinoma progression and immune evasion by recruiting PD-L1+ neutrophils and modulating the PTP4A1/PKM2 axis.","date":"2025","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/41322418","citation_count":1,"is_preprint":false},{"pmid":"36670907","id":"PMC_36670907","title":"Phosphatase of Regenerating Liver-1 (PRL-1)-Overexpressing Placenta-Derived Mesenchymal Stem Cells Enhance Antioxidant Effects via Peroxiredoxin 3 in TAA-Injured Rat Livers.","date":"2022","source":"Antioxidants (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/36670907","citation_count":1,"is_preprint":false},{"pmid":"40747713","id":"PMC_40747713","title":"PTP4A1 promotes intrahepatic cholangiocarcinoma development and progression by interacting with PTEN and activating the PI3K/AKT/GSKα axis.","date":"2025","source":"Oncology reports","url":"https://pubmed.ncbi.nlm.nih.gov/40747713","citation_count":0,"is_preprint":false},{"pmid":"38147218","id":"PMC_38147218","title":"Preparation of Oxidized and Reduced PTP4A1 for Structural and Functional Studies.","date":"2024","source":"Methods in molecular biology (Clifton, N.J.)","url":"https://pubmed.ncbi.nlm.nih.gov/38147218","citation_count":0,"is_preprint":false},{"pmid":"40398601","id":"PMC_40398601","title":"Structure of the phosphocysteine intermediate of the phosphatase of regenerating liver PTP4A1.","date":"2025","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/40398601","citation_count":0,"is_preprint":false},{"pmid":"41769321","id":"PMC_41769321","title":"Protein Tyrosine Phosphatase 4A1 (PTP4A1) Regulates Early Events in Colorectal Cancer Intraperitoneal Dissemination in the Aged Male Host.","date":"2025","source":"Aging and cancer","url":"https://pubmed.ncbi.nlm.nih.gov/41769321","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":32253,"output_tokens":7605,"usd":0.105417,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":17040,"output_tokens":6157,"usd":0.119563,"stage2_stop_reason":"end_turn"},"total_usd":0.22498,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1994,\n      \"finding\": \"PRL-1 encodes a 20-kDa protein tyrosine phosphatase with a conserved active-site cysteine; mutation of this active-site cysteine abolishes phosphatase activity. PRL-1 can dephosphorylate phosphotyrosine substrates in vitro and is located primarily in the cell nucleus. Overexpression causes altered cellular growth, morphology, and transformed phenotype.\",\n      \"method\": \"Active-site mutagenesis (Cys→Ala), in vitro phosphatase assay, nuclear localization by subcellular fractionation/immunofluorescence, stable transfection overexpression\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro enzymatic assay with active-site mutagenesis, nuclear localization demonstrated directly, overexpression phenotype established; foundational paper replicated by subsequent work\",\n      \"pmids\": [\"8196618\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"PRL-1 is prenylated (farnesylated) at its C-terminal CAAX motif, and this prenylation is required for its primary association with the plasma membrane and early endosomal compartment. When farnesylation is inhibited by FTI-277 or the CAAX motif is mutated, PRL-1 relocalizes to the nucleus.\",\n      \"method\": \"Metabolic labeling for prenylation, immunofluorescence and electron microscope immunogold labeling, farnesyltransferase inhibitor (FTI-277) treatment, C-terminal prenylation mutant expression, brefeldin A and wortmannin treatments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (immunogold EM, pharmacological inhibition, mutagenesis) in one study; prenylation-dependent membrane localization replicated across PRL family\",\n      \"pmids\": [\"10747914\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PRL-1 localizes to the endoplasmic reticulum in a farnesylation-dependent manner in non-mitotic cells, and relocalizes to centrosomes and the mitotic spindle (farnesylation-independently) during mitosis. Expression of a catalytic domain mutant delays mitotic progression; expression of a farnesylation-site mutant causes chromosomal bridges and lagging chromosomes in anaphase without affecting spindle checkpoint function.\",\n      \"method\": \"Immunofluorescence of endogenous PRL-1 across cell cycle stages, conditional expression of catalytic mutant and farnesylation mutant in HeLa cells, cell cycle analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiments with functional consequence (mitotic defects), catalytic and farnesylation mutants tested in same study\",\n      \"pmids\": [\"12235145\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"PRL-1 expression in CHO cells enhances cell motility and invasive activity; catalytically inactive PRL-1 mutant has significantly reduced migration-promoting activity. PRL-1-expressing cells, but not controls, form metastatic tumors in mice.\",\n      \"method\": \"Stable CHO cell lines, motility and invasion assays, catalytically inactive mutant, in vivo mouse metastasis model\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — catalytic mutant used to establish enzyme-activity dependence of migration; in vivo metastasis confirmed; replicated across PRL-1 and PRL-3\",\n      \"pmids\": [\"12782572\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Crystal structure of PRL-1 reveals it forms a trimer burying ~1140 Ų per dimer interface, creating a membrane-binding surface. The active site places PRL-1 among dual-specificity phosphatases with closest structural similarity to Cdc14. Native PRL-1 crystallizes in an oxidized form where an intramolecular disulfide between active-site Cys104 and neighboring Cys49 blocks substrate binding and catalysis; biochemical and cell-based studies confirm this disulfide as a redox regulatory mechanism.\",\n      \"method\": \"X-ray crystallography (native and C104S mutant with sulfate), kinetic analysis, biochemical disulfide assays in solution and in cells\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with mutagenesis and in vitro kinetics plus cell-based validation; independent replication of Cys49–Cys104 disulfide regulatory mechanism\",\n      \"pmids\": [\"16142898\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Crystal structure of human PRL-1 at 2.7 Å shows a shallow, hydrophobic active-site pocket with a sulfate ion stabilizing the active conformation. PRL-1 forms a trimer in the crystal, and a trimer is also detected in the membrane fraction of cells, suggesting oligomerization may regulate PRL-1 activity.\",\n      \"method\": \"X-ray crystallography (2.7 Å), cell fractionation to detect trimers in membrane fraction\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with independent biochemical confirmation of trimer in cell membrane fraction; corroborates Sun et al. 2005\",\n      \"pmids\": [\"15571731\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"PRL-1 physically interacts with the transcription factor ATF-7 (a bZIP protein related to ATF/CREB family); the interaction was mapped to ATF-7's bZIP region and PRL-1's phosphatase domain. PRL-1 can dephosphorylate ATF-7 in vitro.\",\n      \"method\": \"Yeast two-hybrid, domain-mapping, in vitro dephosphorylation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid confirmed with domain mapping and in vitro phosphatase assay on substrate; single lab, two orthogonal methods\",\n      \"pmids\": [\"11278933\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Egr-1 directly binds the proximal PRL-1 promoter and transactivates PRL-1 gene expression in response to mitogen stimulation and partial hepatectomy; mutation of the Egr-1 site abolishes this induction.\",\n      \"method\": \"Electrophoretic mobility shift assay (EMSA), reporter gene assays with wild-type and mutant Egr-1 site, Northern blot of regenerating liver\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding (EMSA) and functional reporter with point mutation; single lab, two orthogonal methods\",\n      \"pmids\": [\"9988683\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PRL-1 knockdown in A549 lung cancer cells decreases c-Src and p130Cas expression, reduces Rac1 and Cdc42 activation, and elevates FAK Tyr397 phosphorylation, resulting in reduced invasion and increased cell-substrate adhesion. These results place PRL-1 upstream of c-Src, Rac1, and Cdc42 in adhesion/invasion signaling.\",\n      \"method\": \"Stable shRNA knockdown, invasion and adhesion assays, Western blot for c-Src/p130Cas/FAK phosphorylation, GTPase activation assays, immunofluorescence\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KD with multiple downstream readouts and specific phenotypic outcome; single lab\",\n      \"pmids\": [\"17234774\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PRL-1 overexpression reduces p53 protein levels through ubiquitination and proteasomal degradation, achieved via two independent pathways: induction of PIRH2 transcription and MDM2 phosphorylation through Akt signaling. Conversely, PRL-1 siRNA increases p53 levels. PRL-1 is itself transcriptionally regulated by p53 via a response element in the first intron, forming a negative feedback loop.\",\n      \"method\": \"Overexpression and siRNA knockdown, p53 ubiquitination assay, proteasome inhibitor experiments, reporter assays for PIRH2 and MDM2, identification of p53 response element\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple mechanistic approaches (ubiquitination, proteasome, Akt pathway, reporter assay) in single lab study\",\n      \"pmids\": [\"18997816\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PRL-1 binds the SH3 domain of p115 RhoGAP via a non-canonical interaction in which a PxxP ligand-binding groove of the SH3 domain occupies a folded groove within PRL-1. This interaction prevents p115 RhoGAP from binding MEKK1, thereby activating ERK1/2; simultaneously, PRL-1 binding inhibits the GAP activity of p115 RhoGAP, activating RhoA.\",\n      \"method\": \"Peptide binding/pulldown, co-IP in vitro and in cells, X-ray crystallography of PRL-1·peptide complex, GAP activity assay, ERK1/2 and RhoA activation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure of complex plus in vitro GAP activity assay and cellular signaling readouts; multiple orthogonal methods demonstrating mechanism\",\n      \"pmids\": [\"22009749\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Crystal structure of PRL-1 in complex with the Bateman module (CBS domains) of CNNM2 reveals a heterotetrameric assembly: one CNNM2BAT homodimer bound to two independent PRL-1 molecules. The interaction is mediated via PRL-1's catalytic domain, with CNNM2 Asp-558 in the CBS2 loop being critical for the interface.\",\n      \"method\": \"X-ray crystallography of PRL-1–CNNM2BAT complex, mutagenesis of interface residues (Asp-558)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure of complex with mutagenesis validating key interface residue; mechanistically defines how PRL-1 engages CNNM2\",\n      \"pmids\": [\"27899452\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PTP4A1 promotes TGFβ signaling in dermal fibroblasts by enhancing ERK activity, which stimulates SMAD3 expression and nuclear translocation. Upstream from ERK, PTP4A1 directly interacts with SRC and inhibits basal SRC activation independently of its phosphatase activity. PTP4A2, by contrast, minimally interacts with SRC and does not promote this SRC-ERK-SMAD3 pathway.\",\n      \"method\": \"Co-IP of PTP4A1 with SRC, siRNA knockdown, TGFβ pathway readouts (SMAD3 nuclear translocation, target gene expression), bleomycin fibrosis mouse model, comparison with catalytically inactive mutant\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, phosphatase-dead mutant showing phosphatase-independent SRC binding, in vivo bleomycin model, multiple orthogonal methods; single lab but rigorous design\",\n      \"pmids\": [\"29057934\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PRL-1 phosphatase activity in retinal cones and cone-derived cells is reversibly inhibited by oxidative stress through formation of an intramolecular disulfide bond between active-site Cys104 and Cys49. This was observed in vitro, in cell culture, and in isolated retinas exposed to hydrogen peroxide.\",\n      \"method\": \"In vitro phosphatase activity assay under H2O2 treatment, cell culture oxidative stress experiments, isolated retina experiments, inhibition by glutathione system blockade\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple experimental contexts (in vitro, cells, retina tissue) confirming redox-dependent disulfide regulation; single lab, consistent with structural data\",\n      \"pmids\": [\"17673310\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Drosophila Prl-1 (ortholog of PRL-1) is an axon-intrinsic factor that promotes synapse formation in a spatially restricted manner on a specific axon collateral. Prl-1 modulates insulin receptor (InR) signaling within a single contralateral axon compartment to control synapse number. The axon branch-specific localization and function of Prl-1 depend on its mRNA untranslated regions.\",\n      \"method\": \"Loss-of-function genetics (Drosophila null mutants), overexpression of Prl-1, behavioral (locomotor) assays, genetic epistasis with InR pathway, mRNA UTR deletion analysis\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean loss-of-function and gain-of-function in vivo with defined circuit phenotype, genetic epistasis placing Prl-1 in InR pathway, mechanistic UTR-localization link; high-quality Drosophila ortholog study\",\n      \"pmids\": [\"31048465\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"In Drosophila, overexpression of PRL under normal conditions suppresses growth in a CAAX motif-dependent manner (requiring membrane localization at the apical lateral membrane), and PRL can counteract the oncogenic activity of Src. PRL lacking the CAAX motif retains the ability to inhibit Src function even when associating non-specifically with the plasma membrane.\",\n      \"method\": \"Transgenic Drosophila overexpression, CAAX motif deletion mutant, genetic epistasis with Src, tissue growth assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo transgenic Drosophila with CAAX mutant and genetic interaction with Src; single lab, multiple genetic tools\",\n      \"pmids\": [\"23577193\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PTP4A1 promotes proliferation and epithelial-mesenchymal transition in intrahepatic cholangiocarcinoma (ICC) via PI3K/AKT signaling; downstream effectors include phosphorylation of GSK3β, upregulation of CyclinD1, and EMT transcription factors Zeb1 and Snail.\",\n      \"method\": \"Forced overexpression and knockdown of PTP4A1 in ICC cells, in vitro proliferation/invasion assays, in vivo tumor model, Western blot for PI3K/AKT pathway components\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain- and loss-of-function with in vivo confirmation and defined downstream pathway; single lab\",\n      \"pmids\": [\"27655691\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PRL-1 redistributes to the immunological synapse (IS) in two stages during T cell activation: initially accumulating at scanning membranes enriched in CD3 and actin, then delivered from pericentriolar CD3ζ-containing vesicles. At the established IS, PRL-1 distributes to LFA-1 and CD3ε sites. PRL-1 regulates actin dynamics during IS assembly and IL-2 secretion; pharmacological inhibition of PRL catalytic activity reduces IL-2 secretion.\",\n      \"method\": \"Live imaging, immunofluorescence at immunological synapse, pharmacological inhibition of PRL phosphatase activity, IL-2 secretion assays\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct live-cell localization tied to functional actin and cytokine secretion readouts; single lab, two orthogonal methods\",\n      \"pmids\": [\"30515156\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PTP4A1 dephosphorylates cytohesin-2 at Tyr381, and this dephosphorylation negatively regulates Schwann cell myelination. The adaptor SH2B1 maintains Tyr381 phosphorylation, opposing PTP4A1. Schwann cell-specific knockdown of PTP4A1 increases cytohesin-2 phosphorylation and myelin thickness; SH2B1-specific loss reduces myelin thickness and cytohesin-2 phosphorylation. Knockin mice with Y381F (non-phosphorylatable) cytohesin-2 show reduced myelin thickness and Arf6 activity.\",\n      \"method\": \"In vitro dephosphorylation assay in HEK293T cells, Schwann cell-specific knockdown mice, cytohesin-2 Y381F knockin mice, myelin thickness measurements, Arf6 activity assay\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct substrate identification (Tyr381 of cytohesin-2), multiple in vivo genetic models (KD mice, knockin mice), opposing SH2B1/PTP4A1 regulation demonstrated with multiple orthogonal approaches\",\n      \"pmids\": [\"35077201\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PRL-1/2 counteract the CNNM family's inhibition of TRPM7 magnesium channel function. PRL-2 overexpression prevents CNNM3 from interacting with TRPM7, thereby enhancing TRPM7 activity and magnesium influx. ARL15 small GTPase promotes CNNM3/TRPM7 complex formation to reduce TRPM7 activity, and PRL-2 counteracts this. PRL-1/2 promote TRPM7-induced cell signaling; co-targeting TRPM7 and PRL-1/2 disrupts mitochondrial function and sensitizes cells to magnesium depletion.\",\n      \"method\": \"Genetically encoded intracellular magnesium reporter, co-IP for protein complex formation, overexpression/knockdown of PRL-1/2, CNNM3, ARL15, TRPM7; cell signaling and metabolic stress assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — novel magnesium reporter, multiple Co-IP experiments, overexpression/knockdown with functional metabolic readouts; defines mechanism of PRL-CNNM-TRPM7 axis with multiple orthogonal approaches\",\n      \"pmids\": [\"36972446\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PTP4A1 dephosphorylates USF1 at Ser309 in endothelial cells, increasing USF1 transcriptional activity. This induces TNFAIP3/A20 transcription and subsequent NF-κB inhibition, reducing cell adhesion molecule expression. Ptp4a1 knockout mice show exacerbated IL-1β-induced CAM expression; Ptp4a1 transgenic mice show reduced CAMs. PTP4A1 deficiency in ApoE KO mice worsens diet-induced atherogenesis.\",\n      \"method\": \"shRNA knockdown and overexpression in endothelial cells, Ptp4a1 KO and transgenic mice, chromatin immunoprecipitation, luciferase reporter assays, immunostaining, ApoE KO atherosclerosis model\",\n      \"journal\": \"Cardiovascular research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct substrate (USF1 Ser309) identified, ChIP confirms transcriptional mechanism, multiple in vivo mouse models, reporter assays; multiple orthogonal methods\",\n      \"pmids\": [\"36534975\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PTP4A1 promotes hepatosteatosis prevention by activating the CREBH/FGF21 transcriptional axis. Ptp4a1 knockout mice develop exacerbated glucose dysregulation and hepatosteatosis on a high-fat diet; liver-specific PTP4A1 overexpression rescues this. Mechanistically, lipid accumulation in PTP4A1-deficient hepatocytes reduces GLUT2 at the plasma membrane, impairing glucose uptake.\",\n      \"method\": \"Ptp4a1 KO mice, adeno-associated virus liver-specific PTP4A1 expression, adenovirus FGF21 rescue, glucose/insulin tolerance tests, hyperinsulinemic-euglycemic clamp, co-IP, luciferase reporter assay\",\n      \"journal\": \"Theranostics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple in vivo mouse models (KO, liver-specific OE, rescue with FGF21), co-IP for protein interaction, reporter assays, metabolic phenotyping; comprehensive mechanistic dissection\",\n      \"pmids\": [\"36793871\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PTP4A1 binds pyruvate kinase isoenzyme M2 (PKM2) to promote its expression and binds aconitase 2 (ACO2) to enhance its degradation, thereby regulating mitochondrial metabolic reprogramming and invasive capacity in OSCC cells.\",\n      \"method\": \"Co-IP of PTP4A1 with PKM2 and ACO2, overexpression/knockdown in OSCC cells, in vitro invasion assays, in vivo tumor model\",\n      \"journal\": \"Cell death discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP for two novel binding partners with functional invasion phenotype; single lab, mechanistic detail limited in abstract\",\n      \"pmids\": [\"37773151\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Mutagenesis studies identify an aspartic acid (D72) and the backdoor cysteine (C49) in the PRL-1 catalytic site as required for phosphocysteine hydrolysis. A C49S/D72A double mutant stabilizes the phosphocysteine intermediate for weeks. The crystal structure of cysteine-phosphorylated PRL-1 (PTP4A1) confirms that phosphocysteine sterically interferes with CNNM binding. The D72A mutation increases initial catalytic rate for all three PRL paralogs, in contrast to the homologous mutation in PTP1B/PTPN12 which disrupts catalysis, revealing a mechanistic difference between PRLs and classical PTPs.\",\n      \"method\": \"Site-directed mutagenesis (C49S, D72A), in vitro enzyme assays, X-ray crystallography of phosphocysteine-intermediate form\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure of catalytic intermediate plus mutagenesis and in vitro enzyme kinetics; rigorous mechanistic dissection of catalysis and CNNM binding steric clash\",\n      \"pmids\": [\"40398601\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PTP4A1 promotes cancer–mesothelial cell adhesion in a peritoneal metastasis model; a small molecule inhibitor of PTP4A1 (CMPD-43) reduces RhoA activity and inhibits heterotypic cancer–mesothelial cell adhesion.\",\n      \"method\": \"Peritoneal mesothelial cell proteomics, heterotypic adhesion assay, small molecule inhibitor treatment, RhoA activity assay\",\n      \"journal\": \"Aging and cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Weak — functional adhesion and RhoA assays with pharmacological inhibitor; single lab, limited mechanistic detail in abstract\",\n      \"pmids\": [\"41769321\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PTP4A1 physically interacts with PTEN (validated by co-IP and immunofluorescence), suppresses PTEN phosphorylation, and thereby promotes PI3K/AKT/GSK3α pathway activation to drive ICC cell proliferation, migration, and invasion.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence co-localization, Western blot for PTEN phosphorylation and PI3K/AKT pathway, in vitro and in vivo functional assays\",\n      \"journal\": \"Oncology reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP and immunofluorescence confirming PTP4A1-PTEN interaction with downstream pathway readout; single lab, two orthogonal methods for interaction\",\n      \"pmids\": [\"40747713\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PTP4A1 is catalytically active in its reduced form. The oxidized form (Cys104-Cys49 disulfide) retains biological function by forming a kinase-phosphatase complex with Src kinases, establishing a phosphatase-activity-independent function for oxidized PTP4A1 in systemic sclerosis.\",\n      \"method\": \"Preparation and characterization of oxidized and reduced PTP4A1 protein forms, complex formation assay with Src kinase, functional studies in SSc context\",\n      \"journal\": \"Methods in molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical preparation and complex formation studies; single lab, methods paper but with functional validation of oxidized form/Src complex\",\n      \"pmids\": [\"38147218\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PTP4A1 (PRL-1) is a small, farnesylated dual-specificity phosphatase that cycles between the endoplasmic reticulum/plasma membrane/early endosomes (prenylation-dependent) and the nucleus or mitotic spindle (cell-cycle regulated); its catalytic Cys104 is reversibly inactivated by a Cys49-Cys104 intramolecular disulfide under oxidative stress, while a D72 general-acid residue is required for phosphocysteine hydrolysis via a mechanism distinct from classical PTPs; mechanistically, PTP4A1 activates ERK1/2 and RhoA by binding p115 RhoGAP, promotes TGFβ/SMAD3 fibrotic signaling by forming a phosphatase-activity-independent complex with SRC, dephosphorylates USF1-Ser309 to drive A20/NF-κB anti-inflammatory signaling in endothelial cells, dephosphorylates cytohesin-2-Tyr381 to negatively regulate Schwann cell myelination, dephosphorylates ATF-7 as a nuclear substrate, upregulates CREBH/FGF21 to prevent hepatosteatosis, counteracts CNNM-mediated inhibition of the TRPM7 magnesium channel to regulate intracellular magnesium and cellular metabolism, interacts structurally with CNNM2 via a heterotetrameric interface (catalytic domain of PRL-1 binding CBS2 of CNNM2), and promotes cell migration, invasion, and metastasis in a catalytic-activity-dependent manner—collectively placing PTP4A1 at the nexus of growth-factor signaling, metabolic homeostasis, cytoskeletal regulation, and magnesium transport.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PTP4A1 (PRL-1) is a small, farnesylated dual-specificity protein phosphatase that couples growth-factor and cytoskeletal signaling, magnesium homeostasis, and metabolic control, and acts as a positive regulator of cell motility, invasion, and metastasis in a catalytic-activity-dependent manner [#0, #3]. Its C-terminal CAAX farnesylation directs association with the plasma membrane, early endosomes, and the endoplasmic reticulum, whereas loss of prenylation redirects the protein to the nucleus; during mitosis it relocalizes farnesylation-independently to centrosomes and the spindle, where catalytic and prenylation mutants cause mitotic delay and chromosome segregation defects [#1, #2]. Crystallographic and kinetic work shows PTP4A1 forms membrane-binding trimers and that catalysis proceeds through a phosphocysteine intermediate requiring active-site Cys104 plus an unusual general-acid Asp72 and backdoor Cys49, a mechanism distinct from classical PTPs; the same Cys49–Cys104 pair forms an intramolecular disulfide that reversibly inactivates the enzyme under oxidative stress [#4, #13, #23]. Beyond catalysis, PTP4A1 acts through direct protein interactions: it binds the SH3 domain of p115 RhoGAP via a non-canonical interface to activate ERK1/2 and RhoA [#10], binds SRC in a phosphatase-independent manner to drive ERK/SMAD3-dependent TGFβ fibrotic signaling [#12], and engages the CBS/Bateman module of CNNM2/CNNM3 through its catalytic domain to counteract CNNM-mediated inhibition of the TRPM7 magnesium channel, thereby controlling intracellular magnesium and mitochondrial metabolism [#11, #19]. PTP4A1 also has defined dephosphorylation substrates with tissue-specific outputs: it dephosphorylates cytohesin-2 at Tyr381 to negatively regulate Schwann cell myelination [#18] and dephosphorylates USF1 at Ser309 to induce A20 and restrain endothelial NF-κB-driven inflammation and atherogenesis [#20], and it activates a CREBH/FGF21 axis in liver to prevent diet-induced hepatosteatosis and glucose dysregulation [#21]. In cancer contexts it promotes proliferation, EMT, and invasion through PI3K/AKT signaling and PTEN suppression [#16, #25].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"Established PRL-1 as a bona fide protein tyrosine phosphatase whose enzymatic activity drives altered growth, answering whether the immediate-early gene encoded a functional catalytic enzyme.\",\n      \"evidence\": \"Active-site Cys\\u2192Ala mutagenesis, in vitro phosphatase assay, and overexpression in transfected cells with nuclear localization\",\n      \"pmids\": [\"8196618\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No physiological substrate identified\", \"Mechanism linking activity to transformed phenotype unresolved\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Identified how PRL-1 expression is induced, showing Egr-1 directly transactivates the promoter during mitogenic and regenerative stimulation.\",\n      \"evidence\": \"EMSA, reporter assays with mutated Egr-1 site, Northern blot of regenerating liver\",\n      \"pmids\": [\"9988683\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not address protein-level regulation or downstream targets\", \"Single-lab transcriptional study\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Defined the basis of PRL-1 membrane targeting, establishing that C-terminal farnesylation governs plasma-membrane/endosomal localization versus default nuclear localization.\",\n      \"evidence\": \"Metabolic prenylation labeling, immunogold EM, FTI-277 inhibition, and CAAX mutagenesis\",\n      \"pmids\": [\"10747914\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of each localization not fully resolved\", \"Trafficking machinery unidentified\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Provided the first candidate nuclear substrate by mapping a direct interaction with transcription factor ATF-7 and showing in vitro dephosphorylation.\",\n      \"evidence\": \"Yeast two-hybrid, domain mapping, in vitro dephosphorylation assay\",\n      \"pmids\": [\"11278933\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological relevance in cells not established\", \"ATF-7 phosphosite not defined\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Connected localization to cell-cycle function, showing PRL-1 moves to centrosomes/spindle in mitosis and that catalytic and farnesylation mutants cause mitotic defects.\",\n      \"evidence\": \"Endogenous immunofluorescence across cell cycle, conditional catalytic and CAAX mutant expression in HeLa\",\n      \"pmids\": [\"12235145\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mitotic substrate unknown\", \"Mechanism of spindle recruitment unresolved\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Demonstrated that PRL-1 catalytic activity is required for pro-motility and metastatic behavior, linking the enzyme to cancer cell invasion in vivo.\",\n      \"evidence\": \"Stable CHO lines, motility/invasion assays, catalytically inactive mutant, mouse metastasis model\",\n      \"pmids\": [\"12782572\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct substrate driving migration not identified\", \"Pathway intermediates undefined at this stage\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Resolved the structure and redox regulation of the catalytic domain, defining a membrane-binding trimer and a Cys49\\u2013Cys104 disulfide that blocks catalysis.\",\n      \"evidence\": \"X-ray crystallography of native and mutant PRL-1, kinetics, and cell-based disulfide assays\",\n      \"pmids\": [\"16142898\", \"15571731\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological trigger of oxidation in vivo not yet defined\", \"Functional role of trimerization in cells unclear\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Placed PRL-1 upstream in adhesion/invasion signaling and confirmed oxidative-stress regulation in a native tissue context.\",\n      \"evidence\": \"shRNA knockdown in A549 with Src/Rac1/Cdc42/FAK readouts; H2O2 disulfide experiments in cells and isolated retina\",\n      \"pmids\": [\"17234774\", \"17673310\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct dephosphorylation events not established in the invasion pathway\", \"Redox studies single-lab\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Identified a p53 feedback loop, showing PRL-1 lowers p53 via PIRH2 and Akt/MDM2 while p53 transcriptionally controls PRL-1.\",\n      \"evidence\": \"Overexpression/siRNA, ubiquitination and proteasome assays, reporter assays, p53 response element mapping\",\n      \"pmids\": [\"18997816\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct phosphatase substrate in the pathway not defined\", \"Single-lab mechanistic study\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Defined a non-catalytic scaffolding mechanism whereby PRL-1 binds the p115 RhoGAP SH3 domain to simultaneously activate ERK1/2 and RhoA.\",\n      \"evidence\": \"Peptide binding, co-IP, crystallography of PRL-1\\u00b7peptide complex, GAP and signaling assays\",\n      \"pmids\": [\"22009749\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo physiological output of this complex not addressed\", \"Interplay with catalytic substrates unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Showed in Drosophila that membrane-localized PRL suppresses growth and antagonizes Src, with CAAX-independent Src inhibition revealing functional complexity.\",\n      \"evidence\": \"Transgenic overexpression, CAAX deletion mutant, genetic epistasis with Src\",\n      \"pmids\": [\"23577193\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct biochemical link to Src not defined here\", \"Reconciliation with pro-oncogenic roles in mammals incomplete\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined the structural basis of CNNM engagement, showing the PRL-1 catalytic domain binds the CNNM2 Bateman module in a heterotetramer.\",\n      \"evidence\": \"X-ray crystallography of PRL-1\\u2013CNNM2BAT complex with interface mutagenesis (Asp-558)\",\n      \"pmids\": [\"27899452\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional output of the complex not yet established in this study\", \"Competition with substrate binding unresolved here\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Extended PRL-1 oncogenic signaling to PI3K/AKT, linking it to proliferation and EMT in cholangiocarcinoma.\",\n      \"evidence\": \"Overexpression/knockdown in ICC cells, in vivo tumor model, Western blot of AKT/GSK3\\u03b2/CyclinD1/Zeb1/Snail\",\n      \"pmids\": [\"27655691\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism connecting PTP4A1 to PI3K/AKT not defined here\", \"Direct substrate unidentified\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Established a phosphatase-independent SRC-binding mechanism driving TGF\\u03b2/ERK/SMAD3 fibrotic signaling and distinguished PTP4A1 from PTP4A2.\",\n      \"evidence\": \"Reciprocal co-IP, phosphatase-dead mutant, SMAD3 readouts, bleomycin fibrosis mouse model\",\n      \"pmids\": [\"29057934\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of PTP4A1-SRC binding not resolved\", \"How catalytic and scaffolding roles are balanced unclear\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Localized PRL-1 to the immunological synapse and tied its activity to actin dynamics and IL-2 secretion in T cells.\",\n      \"evidence\": \"Live imaging, IS immunofluorescence, pharmacological PRL inhibition, IL-2 assays\",\n      \"pmids\": [\"30515156\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No T-cell substrate identified\", \"Inhibitor specificity caveats\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Showed in Drosophila that Prl-1 modulates insulin-receptor signaling in an axon-branch-specific, UTR-dependent manner to control synapse number.\",\n      \"evidence\": \"Loss/gain-of-function genetics, InR epistasis, mRNA UTR deletion, locomotor assays\",\n      \"pmids\": [\"31048465\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mammalian relevance of neuronal role untested in corpus\", \"Biochemical InR-pathway substrate undefined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified cytohesin-2 Tyr381 as a direct substrate and placed PTP4A1 opposite SH2B1 in negative control of Schwann cell myelination.\",\n      \"evidence\": \"In vitro dephosphorylation, Schwann cell-specific KD mice, cytohesin-2 Y381F knockin mice, Arf6 activity assays\",\n      \"pmids\": [\"35077201\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Upstream signals controlling PTP4A1 in Schwann cells unknown\", \"Generalization to other myelinating contexts untested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined multiple in vivo physiological substrates and axes \\u2014 USF1-Ser309/A20/NF-\\u03baB in endothelial anti-inflammation, CREBH/FGF21 in hepatosteatosis prevention, and PRL-CNNM-TRPM7 in magnesium/metabolic control.\",\n      \"evidence\": \"KO and transgenic/liver-specific OE mice, ChIP and reporter assays, magnesium reporter, co-IP, atherosclerosis and metabolic models\",\n      \"pmids\": [\"36534975\", \"36793871\", \"36972446\", \"37773151\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Tissue specificity of substrate selection mechanism unclear\", \"How a single phosphatase coordinates these distinct programs unresolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Demonstrated that the oxidized, catalytically inactive form retains biological function by forming a phosphatase-independent complex with Src kinases.\",\n      \"evidence\": \"Biochemical preparation of oxidized/reduced forms and Src complex assays in systemic sclerosis context\",\n      \"pmids\": [\"38147218\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab biochemical characterization\", \"In vivo relevance of the oxidized-Src complex not fully established\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Dissected the unusual catalytic mechanism (Asp72 general acid, backdoor Cys49, phosphocysteine intermediate) and showed it differs from classical PTPs and sterically gates CNNM binding.\",\n      \"evidence\": \"C49S/D72A mutagenesis, in vitro kinetics, crystal structure of phosphocysteine intermediate\",\n      \"pmids\": [\"40398601\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological control of the catalytic-vs-CNNM-binding switch unresolved\", \"How intermediate stabilization affects substrate range unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Added a PTEN-suppression mechanism and an inhibitable RhoA-dependent adhesion role in cancer metastasis.\",\n      \"evidence\": \"Co-IP and immunofluorescence with PTEN, PI3K/AKT readouts; peritoneal adhesion assays with CMPD-43 inhibitor and RhoA assay\",\n      \"pmids\": [\"40747713\", \"41769321\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether PTEN is a direct dephosphorylation substrate not established\", \"Inhibitor specificity and target engagement limited\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PTP4A1 selects among its many substrates and binding partners across tissues, and how localization, redox state, and the catalytic/scaffolding switch are coordinated to specify distinct biological outputs, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No unifying model integrating catalytic, scaffolding, and redox functions\", \"Substrate-selection determinants in vivo unknown\", \"Spatial regulation across compartments incompletely mapped\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 6, 18, 20]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 4, 23]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [10, 12, 19]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [10, 11]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 5]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0005819\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [10, 12, 16, 25]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [3, 16, 20, 21]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [19]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [19, 21, 22]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"CNNM2\", \"CNNM3\", \"SRC\", \"ARHGAP5\", \"TRPM7\", \"ATF7\", \"PTEN\", \"PKM2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}