{"gene":"PTPN22","run_date":"2026-04-28T19:45:45","timeline":{"discoveries":[{"year":1999,"finding":"LYP/PTPN22 is an intracellular protein tyrosine phosphatase expressed predominantly in lymphoid tissues; it contains a single catalytic PTP domain and four proline-rich SH3-binding motifs; it is constitutively associated with the proto-oncogene c-Cbl in thymocytes and T cells, and overexpression of LYP reduces Cbl tyrosine phosphorylation, indicating Cbl is a substrate.","method":"Molecular cloning, co-immunoprecipitation, overexpression in T cells with phosphorylation assays","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2-3 — reciprocal Co-IP and functional overexpression assay in a single lab; foundational characterization paper","pmids":["10068674"],"is_preprint":false},{"year":2006,"finding":"PTPN22 directly dephosphorylates the activating tyrosines of Lck (Tyr-394) and Zap70 (Tyr-493), but not their regulatory tyrosines; TCRζ is also a direct substrate dephosphorylated by PTPN22 both in vitro and in cells; additional substrates include Vav, CD3ε, and valosin-containing protein, identified by substrate-trapping mass spectrometry.","method":"Substrate trapping with catalytically inactive PTPN22-D195A/C227S mutant coupled to mass spectrometry, in vitro dephosphorylation assays with purified recombinant proteins, co-immunoprecipitation in 293T cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with purified proteins, mutagenesis-based substrate trap, and cell-based validation; multiple orthogonal methods in one study","pmids":["16461343"],"is_preprint":false},{"year":2007,"finding":"Crystal structure of LYP (PTPN22) reveals a Lyp-specific insert region (S35TKYKADK42) that can adopt loop or helical conformations; PKC phosphorylates LYP exclusively at Ser-35 both in vitro and in vivo, and Ser-35 phosphorylation impairs LYP's ability to inactivate Src family kinases and down-regulate TCR signaling; a bidentate salicylic acid-based inhibitor I-C11 was identified that binds both the active site and a peripheral site unique to LYP.","method":"X-ray crystallography, in vitro kinase assay (PKC phosphorylation of Ser-35), site-directed mutagenesis, cellular TCR signaling assays, small-molecule inhibitor characterization","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 — crystal structure combined with mutagenesis, in vitro and in vivo phosphorylation assays, and functional TCR signaling readout; multiple orthogonal methods in one study","pmids":["18056643"],"is_preprint":false},{"year":2012,"finding":"LYP inhibits T-cell activation when dissociated from CSK; dissociation of the LYP-CSK complex is required for recruitment of LYP to the plasma membrane where it downmodulates TCR signaling; the disease-associated R620W variant, which cannot bind CSK, shows reduced TCR-mediated signaling consistent with constitutive LYP activity at the membrane.","method":"Live-cell imaging of LYP-CSK complex spatiotemporal dynamics, selective chemical LYP inhibitor, T-cell activation assays","journal":"Nature chemical biology","confidence":"High","confidence_rationale":"Tier 1-2 — direct localization experiment tied to functional consequence, chemical probe validation, multiple orthogonal methods","pmids":["22426112"],"is_preprint":false},{"year":2013,"finding":"PTPN22 directly associates with TRAF3 and promotes TRAF3 lysine-63-linked ubiquitination, selectively enhancing TLR-driven type I interferon production in myeloid cells; the disease-associated PTPN22-R620W variant fails to promote TRAF3 ubiquitination and type I IFN upregulation.","method":"Co-immunoprecipitation of PTPN22 with TRAF3, ubiquitination assays, Ptpn22-knockout mouse studies with TLR agonist stimulation, colitis and arthritis models","journal":"Immunity","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, KO mouse with defined phenotypic readout, biochemical ubiquitination assay, replicated across multiple disease models","pmids":["23871208"],"is_preprint":false},{"year":2013,"finding":"The disease-linked PEP-R619W knockin variant (mouse ortholog of human LYP-R620W) renders lymphocytes hyperresponsive to antigen-receptor engagement with a distinct phosphotyrosine substrate profile, promotes effector T cell and B cell expansion, disrupts B cell selection, and leads to development of autoantibodies and systemic autoimmunity in aged mice.","method":"Knockin mouse generation, flow cytometric immunophenotyping, antigen-receptor stimulation assays, phosphoproteomic profiling, autoantibody detection","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — precise genetic knockin model with multiple orthogonal readouts (cellular, biochemical, serological); strong mechanistic evidence","pmids":["23619366"],"is_preprint":false},{"year":2003,"finding":"LYP/PTPN22 is expressed in myeloid cells (granulocytes, monocytes) in addition to lymphocytes and localizes to the cytosol; overexpression of LYP reduces phosphorylation of Cbl, Bcr-Abl, Erk1/2, and CrkL and suppresses anchorage-independent growth of CML cells, suggesting LYP antagonizes Bcr-Abl signaling.","method":"RT-PCR expression profiling, subcellular fractionation, overexpression in CML cell lines with phosphorylation assays, colony formation assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 — direct localization by fractionation with functional consequence; overexpression data from single lab","pmids":["12764153"],"is_preprint":false},{"year":2012,"finding":"An alternative splice isoform of PTPN22, PTPN22.6, lacks nearly the entire phosphatase domain and functions as a dominant-negative isoform of full-length PTPN22; expression of the W620 variant of PTPN22.6 (but not PTPN22.1-W620) leads to hyperactivation of human T cells.","method":"Identification of splice variant by cloning, dominant-negative overexpression assays in T cells, T-cell activation readouts","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 3 — single lab, overexpression system with functional readout; no reconstitution with purified proteins","pmids":["22427951"],"is_preprint":false},{"year":2013,"finding":"PTPN22 suppresses M1 macrophage polarization and reciprocally promotes M2-associated gene expression; PTPN22-deficient mice develop more severe dextran sulfate sodium-induced colitis with increased M1 macrophage polarization in the intestine; PTPN22 also suppresses its own expression in M1 but not M2 macrophages (autoinhibition).","method":"Ptpn22-knockout mice, dextran sulfate sodium colitis model, gene expression analysis of M1/M2 markers, PTPN22 knockdown in human macrophages","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 — KO mouse with defined cellular and disease phenotype; multiple readouts from single lab","pmids":["23913970"],"is_preprint":false},{"year":2016,"finding":"PTPN22 is required for full FcγR-mediated neutrophil activation; Ptpn22-/- neutrophils show reduced adhesion, ROS production, and degranulation upon immune complex stimulation; PTPN22 regulates tyrosine phosphorylation of Lyn and Syk in neutrophils; Ptpn22-/- mice are protected from immune complex-mediated arthritis.","method":"Ptpn22-knockout mouse neutrophil functional assays (adhesion, ROS, degranulation), phosphorylation analysis of Lyn and Syk, serum transfer arthritis model","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — KO mouse with multiple defined functional readouts plus in vivo disease model; biochemical mechanism (Lyn/Syk phosphorylation) identified","pmids":["27807193"],"is_preprint":false},{"year":2016,"finding":"Loss of PTPN22 increases the size of the regulatory T cell (Treg) compartment by upregulating GITR expression and enhancing GITR signaling, leading to prolonged Treg survival rather than accelerated division; GITR ligand blockade prevents Treg expansion caused by Ptpn22 knockdown.","method":"Ptpn22 siRNA knockdown in mice, GITR ligand blockade, apoptosis and proliferation assays of Treg cells, flow cytometric phenotyping","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2-3 — genetic knockdown with mechanistic follow-up (GITR blockade rescue), single lab","pmids":["26810223"],"is_preprint":false},{"year":2017,"finding":"TRAF3 associates with PTPN22 and regulates its recruitment to the TCR/CD28 complex; loss of TRAF3 results in increased amounts of PTPN22 in T cell membrane fractions and decreased association of PTPN22 with CSK, thereby reducing activating phosphorylation of Lck.","method":"Co-immunoprecipitation of TRAF3 with PTPN22 and CSK, membrane fractionation of TRAF3-deficient T cells, phosphorylation analysis of Lck","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP and fractionation with genetic KO; single lab but multiple biochemical readouts","pmids":["28522807"],"is_preprint":false},{"year":2017,"finding":"PTPN22 negatively regulates dectin-1 signaling in dendritic cells by restraining Syk and Erk phosphorylation; Ptpn22-/- BMDCs show enhanced IL-1β secretion and drive increased IL-17 T-cell responses upon dectin-1 stimulation; the Ptpn22-R619W variant also increases IL-1β secretion in this context, acting as a loss-of-function allele for dectin-1 regulation.","method":"Ptpn22-/- and Ptpn22-R619W knockin bone marrow-derived dendritic cells, dectin-1 agonist (curdlan) stimulation, Syk/Erk immunoblotting, in vitro and in vivo T-cell co-culture assays","journal":"European journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 — KO and knockin mouse cells, biochemical signaling readouts plus functional T-cell assays; single lab","pmids":["28948613"],"is_preprint":false},{"year":2018,"finding":"PTPN22 negatively regulates LFA-1-dependent Th1 responses through two mechanisms: (1) a T cell-intrinsic mechanism whereby Ptpn22-/- T cells have enhanced ability to engage ICAM-1 at the immune synapse; (2) a T cell-extrinsic mechanism whereby Ptpn22-/- dendritic cells enhance Th1 development in an LFA-1/ICAM-dependent manner.","method":"Ptpn22-/- mice, planar lipid bilayer immune synapse assays, DC-T cell conjugate formation assays, in vitro and in vivo Th1 differentiation assays with LFA-1 blockade","journal":"Journal of autoimmunity","confidence":"Medium","confidence_rationale":"Tier 2 — KO mouse with multiple mechanistic readouts including direct imaging at immune synapse; single lab","pmids":["30054208"],"is_preprint":false},{"year":2018,"finding":"PTPN22 negatively regulates FcγR-mediated antigen presentation in dendritic cells; Ptpn22-/- BMDCs show enhanced uptake and presentation of immune complex-derived antigens and form more DC-T cell conjugates, leading to enhanced T cell proliferation.","method":"Ptpn22-/- bone marrow-derived DCs pulsed with ovalbumin:anti-ovalbumin immune complexes, T cell co-culture proliferation assays, DC-T cell conjugate quantification","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 — KO mouse cells with defined functional assay; single lab","pmids":["30139951"],"is_preprint":false},{"year":2020,"finding":"PTPN22 interacts with end-binding protein 1 (EB1) via the P1 proline-rich domain of PTPN22 (competing with CSK binding); PTPN22 dephosphorylates EB1 at tyrosine-247, which reduces expression of T cell activation markers CD25 and CD69, decreases phosphorylation of ZAP-70, LAT, and Erk, and reduces NFAT activation and IL-2 secretion; the R620W variant does not affect EB1 association.","method":"Yeast two-hybrid screen, mass spectrometry, co-immunoprecipitation, site-directed mutagenesis, in vitro dephosphorylation assay, T-cell activation assays","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 1-2 — in vitro dephosphorylation assay plus multiple cell-based readouts; single lab","pmids":["32469452"],"is_preprint":false},{"year":2022,"finding":"PTPN22 activity is redox-regulated through the non-catalytic Cys129 residue, which forms a disulfide with catalytic Cys227; a C129S knock-in mouse shows enhanced TCR signaling, stronger T-cell-dependent inflammation, and more severe autoimmune arthritis; thioredoxin can directly reduce the native PTPN22 disulfide to reactivate the enzyme; the functional effects depend on the NOX2 component Ncf1.","method":"C129S knock-in mouse, Ncf1-mutant double-mutant epistasis, in vitro activity assays with purified PTPN22 proteins, thioredoxin reductase assays, autoimmune arthritis model","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 — in vitro biochemical reconstitution with purified proteins, genetic epistasis with Ncf1, knock-in mouse with disease phenotype; multiple orthogonal methods","pmids":["35587260"],"is_preprint":false},{"year":2022,"finding":"PTPN22 is expressed in human and mouse platelets and negatively regulates platelet function; PTPN22-deficient mice show enhanced platelet aggregation, granule secretion, calcium mobilization, and accelerated arterial thrombus formation; PTPN22 interacts with phosphorylated PDE5A (Ser92) and dephosphorylates it, modulating cGMP signaling; purified PTPN22 (but not catalytic-dead C227S mutant) has intrinsic serine phosphatase activity toward PDE5A.","method":"PTPN22-/- mouse model, phosphoproteomic analysis, co-immunoprecipitation of PTPN22 with phospho-PDE5A, in vitro phosphatase assay with purified proteins and C227S mutant, arterial thrombosis model","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro reconstitution with purified enzyme + mutagenesis, KO mouse with multiple functional readouts, phosphoproteomic substrate identification; multiple orthogonal methods","pmids":["35767715"],"is_preprint":false},{"year":2013,"finding":"LYP (encoded by PTPN22) interacts with CSK through its P1 and P2 proline-rich motifs and CSK's SH3 and SH2 domains; this interaction is inducible upon TCR stimulation rather than constitutive; abrogating LYP/CSK interaction does not preclude regulation of TCR signaling by these proteins.","method":"Co-immunoprecipitation, domain mapping with truncation mutants, TCR stimulation time-course experiments","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 3 — Co-IP with domain mapping; single lab, contradicts earlier model of constitutive interaction","pmids":["23359562"],"is_preprint":false},{"year":2012,"finding":"The Lyp variants R263Q and R266W both have significantly reduced phosphatase activity compared to wild-type Lyp; R266W severely impairs catalytic activity likely by perturbing the Q-loop or WPD loop; both are loss-of-function variants in T cell signaling assays.","method":"In vitro kinetic phosphatase assays with purified recombinant Lyp variants, structural modeling, T cell signaling functional assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 1-2 — in vitro biochemical assay with purified proteins plus cell-based functional assay; single lab","pmids":["22952725"],"is_preprint":false}],"current_model":"PTPN22/LYP is a lymphoid-enriched non-receptor protein tyrosine phosphatase that dephosphorylates and inactivates key TCR-proximal kinases (Lck at Tyr-394, ZAP70 at Tyr-493, TCRζ) and is redox-regulated via a Cys129–Cys227 disulfide; it is recruited to the plasma membrane upon dissociation from its binding partner CSK (which requires the P1 proline-rich motif), where it attenuates TCR signaling, and also functions in myeloid cells by promoting TRAF3 K63-ubiquitination to potentiate TLR-driven type I IFN responses, regulating FcγR-mediated neutrophil activation through Lyn/Syk dephosphorylation, modulating macrophage M1/M2 polarization, and negatively regulating platelet activation via dephosphorylation of PDE5A; the autoimmunity-associated R620W variant disrupts CSK binding, impairs TRAF3 ubiquitination and type I IFN production, and confers hyperresponsiveness in lymphocytes and altered innate immune signaling."},"narrative":{"teleology":[{"year":1999,"claim":"Establishing PTPN22 as a lymphoid PTP with proline-rich SH3-binding motifs and identifying c-Cbl as an initial interaction partner and putative substrate defined the gene as a T-cell signaling phosphatase.","evidence":"Molecular cloning, co-immunoprecipitation in thymocytes and T cells, overexpression phosphorylation assays","pmids":["10068674"],"confidence":"Medium","gaps":["c-Cbl as substrate was based on overexpression Co-IP without purified-protein reconstitution","physiological relevance of Cbl dephosphorylation not tested in loss-of-function setting"]},{"year":2006,"claim":"Substrate-trapping and in vitro reconstitution identified the precise TCR-proximal substrates — Lck Tyr-394, ZAP-70 Tyr-493, and TCRζ — establishing PTPN22 as a direct negative regulator of the earliest TCR signaling events.","evidence":"Catalytically inactive D195A/C227S substrate-trap coupled to mass spectrometry, in vitro dephosphorylation with purified proteins, 293T cell validation","pmids":["16461343"],"confidence":"High","gaps":["relative contributions of individual substrate dephosphorylation events to TCR output not dissected","whether PTPN22 acts on these substrates simultaneously or sequentially in vivo unknown"]},{"year":2007,"claim":"The crystal structure revealed a Lyp-specific insert whose Ser-35 is phosphorylated by PKC, providing the first post-translational regulatory mechanism that tunes PTPN22 phosphatase activity and consequently TCR signal strength.","evidence":"X-ray crystallography, in vitro PKC kinase assay, mutagenesis, cellular TCR signaling readouts","pmids":["18056643"],"confidence":"High","gaps":["which PKC isoform(s) phosphorylate Ser-35 in physiological settings not defined","structural basis for how Ser-35 phosphorylation alters catalytic activity not resolved"]},{"year":2012,"claim":"Live-cell imaging resolved a longstanding question about how PTPN22 accesses its membrane-proximal substrates: dissociation from the cytosolic CSK complex is required for PTPN22 membrane recruitment, and the R620W variant, constitutively free of CSK, is hyperactive at the membrane.","evidence":"Live-cell imaging of LYP-CSK dynamics, selective chemical LYP inhibitor, T-cell activation assays","pmids":["22426112"],"confidence":"High","gaps":["signals triggering CSK-PTPN22 dissociation upon TCR engagement not identified","whether additional scaffolds recruit free PTPN22 to the membrane unknown"]},{"year":2012,"claim":"Characterization of R263Q and R266W variants as loss-of-function alleles demonstrated that structural integrity of the Q-loop/WPD-loop region is essential for catalytic activity, establishing a structure-function framework for disease-associated variants.","evidence":"In vitro kinetic assays with purified recombinant variants, structural modeling, T-cell signaling assays","pmids":["22952725"],"confidence":"Medium","gaps":["no crystal structures of these variants obtained","population-level disease associations for R263Q/R266W not established"]},{"year":2013,"claim":"The R619W knockin mouse (ortholog of human R620W) provided definitive in vivo evidence that the variant causes lymphocyte hyperresponsiveness, disrupted B cell selection, and spontaneous autoimmunity, directly linking PTPN22 loss-of-interaction to autoimmune pathogenesis.","evidence":"Knockin mouse, flow cytometry, phosphoproteomic profiling, autoantibody detection","pmids":["23619366"],"confidence":"High","gaps":["which specific phosphoproteomic changes are causally responsible for autoimmunity not determined","epistatic modifiers required for penetrant disease not identified"]},{"year":2013,"claim":"Discovery that PTPN22 promotes TRAF3 K63-ubiquitination to enhance type I IFN production established a phosphatase-independent scaffolding function in myeloid innate immunity, fundamentally expanding PTPN22's role beyond TCR signaling.","evidence":"Co-immunoprecipitation, ubiquitination assays, Ptpn22-KO mice stimulated with TLR agonists, colitis and arthritis models","pmids":["23871208"],"confidence":"High","gaps":["E3 ligase catalyzing TRAF3 K63-ubiquitination recruited by PTPN22 not identified","whether the phosphatase domain is entirely dispensable for this function not tested"]},{"year":2013,"claim":"The finding that PTPN22 suppresses M1 macrophage polarization and promotes M2 gene expression extended its innate immune role to macrophage functional polarization, with therapeutic implications for inflammatory bowel disease.","evidence":"Ptpn22-KO mice in DSS colitis model, M1/M2 gene expression analysis, human macrophage knockdown","pmids":["23913970"],"confidence":"Medium","gaps":["direct substrates mediating M1/M2 skewing not identified","whether this reflects phosphatase activity or scaffolding unknown"]},{"year":2016,"claim":"Demonstration that PTPN22 is required for full FcγR-mediated neutrophil activation via Lyn/Syk dephosphorylation revealed a context-dependent positive regulatory role — opposite to its inhibitory function in T cells — and provided protection from immune complex arthritis.","evidence":"Ptpn22-KO neutrophil functional assays, Lyn/Syk phosphorylation analysis, serum transfer arthritis model","pmids":["27807193"],"confidence":"High","gaps":["mechanism by which PTPN22-mediated Lyn/Syk dephosphorylation promotes rather than inhibits neutrophil activation not fully explained","whether specific Lyn/Syk tyrosine sites differ from those in T cells not mapped"]},{"year":2017,"claim":"TRAF3 was shown to reciprocally regulate PTPN22 by controlling its membrane recruitment and CSK association, establishing a bidirectional TRAF3–PTPN22 regulatory axis in T cells.","evidence":"Co-immunoprecipitation, membrane fractionation of TRAF3-deficient T cells, Lck phosphorylation analysis","pmids":["28522807"],"confidence":"Medium","gaps":["structural basis of TRAF3-PTPN22 interaction not defined","whether TRAF3 regulation of PTPN22 localization operates in myeloid cells unknown"]},{"year":2020,"claim":"Identification of EB1 as a PTPN22 substrate dephosphorylated at Tyr-247 revealed a non-canonical mechanism linking PTPN22 to microtubule-associated signaling and T cell activation, expanding its substrate repertoire beyond canonical TCR kinases.","evidence":"Yeast two-hybrid, mass spectrometry, in vitro dephosphorylation, T-cell activation assays","pmids":["32469452"],"confidence":"Medium","gaps":["physiological consequence of EB1-Tyr247 dephosphorylation on microtubule dynamics not tested","in vivo relevance using loss-of-function models not established"]},{"year":2022,"claim":"Redox regulation of PTPN22 via a Cys129–Cys227 disulfide bond, reversible by thioredoxin and dependent on NOX2/Ncf1-generated ROS, established reactive oxygen species as physiological modulators of PTPN22 activity and TCR signaling strength.","evidence":"C129S knock-in mouse, Ncf1 epistasis, in vitro thioredoxin reductase assay with purified protein, autoimmune arthritis model","pmids":["35587260"],"confidence":"High","gaps":["kinetics and spatial dynamics of disulfide formation/reduction in intact T cells not measured","whether other PTPs in the same signaling cascade are co-regulated by the same ROS pool unknown"]},{"year":2022,"claim":"Discovery that PTPN22 dephosphorylates PDE5A at Ser-92 in platelets — exhibiting serine phosphatase activity — and negatively regulates platelet aggregation and thrombus formation extended its function to hemostasis and revealed unexpected dual-specificity catalysis.","evidence":"PTPN22-KO mouse platelets, phosphoproteomic analysis, in vitro phosphatase assay with purified PTPN22 and C227S mutant, arterial thrombosis model","pmids":["35767715"],"confidence":"High","gaps":["structural basis for serine phosphatase activity in a classical tyrosine phosphatase not resolved","whether dual-specificity activity extends to other substrates unknown","platelet phenotype relevance to human thrombotic disease not established"]},{"year":null,"claim":"Key unresolved questions include the signals that trigger CSK-PTPN22 dissociation upon receptor engagement, the structural basis for PTPN22's dual tyrosine/serine phosphatase activity, the identity of the E3 ligase mediating TRAF3 ubiquitination downstream of PTPN22, and how context-dependent switching between positive and negative regulation is achieved across cell types.","evidence":"","pmids":[],"confidence":"Low","gaps":["no structural model of PTPN22-CSK or PTPN22-TRAF3 complexes","mechanism of cell-type-specific functional polarity (inhibitory in T cells, activating in neutrophils) not explained","therapeutic targeting strategies remain preclinical"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[1,2,9,15,17,19]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[3,4,8,10]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[3,6]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[3]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[1,3,4,5,9,12,13,14]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,2,3,11,15,16]},{"term_id":"R-HSA-109582","term_label":"Hemostasis","supporting_discovery_ids":[17]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[5,8]}],"complexes":[],"partners":["CSK","TRAF3","LCK","ZAP70","MAPK1E1","SYK","LYN","PDE5A"],"other_free_text":[]},"mechanistic_narrative":"PTPN22 (LYP) is a lymphoid- and myeloid-expressed non-receptor protein tyrosine phosphatase that serves as a central negative regulator of antigen receptor and innate immune signaling across multiple hematopoietic lineages. Its catalytic domain directly dephosphorylates activating tyrosines on TCR-proximal kinases Lck (Tyr-394) and ZAP-70 (Tyr-493), as well as TCRζ, Vav, and CD3ε, thereby attenuating T cell activation; dissociation from its cytosolic partner CSK is required for PTPN22 translocation to the plasma membrane where it exerts this inhibitory function [PMID:16461343, PMID:22426112]. Beyond lymphocytes, PTPN22 promotes TRAF3 K63-linked ubiquitination to enhance TLR-driven type I interferon production in myeloid cells, regulates FcγR-mediated neutrophil activation through Lyn/Syk dephosphorylation, restrains dectin-1 signaling in dendritic cells, modulates macrophage M1/M2 polarization, and negatively regulates platelet activation via dephosphorylation of PDE5A [PMID:23871208, PMID:27807193, PMID:28948613, PMID:35767715]. Enzyme activity is redox-regulated through a Cys129–Cys227 disulfide bond reversible by thioredoxin, and PKC-mediated phosphorylation at Ser-35 impairs its capacity to inactivate Src-family kinases [PMID:35587260, PMID:18056643]. The autoimmunity-associated R620W variant disrupts CSK binding, impairs TRAF3 ubiquitination, and confers lymphocyte hyperresponsiveness leading to autoantibody production and systemic autoimmunity in knockin mice [PMID:23619366, PMID:23871208]."},"prefetch_data":{"uniprot":{"accession":"Q9Y2R2","full_name":"Tyrosine-protein phosphatase non-receptor type 22","aliases":["Hematopoietic cell protein-tyrosine phosphatase 70Z-PEP","Lymphoid phosphatase","LyP","PEST-domain phosphatase","PEP"],"length_aa":807,"mass_kda":91.7,"function":"Acts as a negative regulator of T-cell receptor (TCR) signaling by direct dephosphorylation of the Src family kinases LCK and FYN, ITAMs of the TCRz/CD3 complex, as well as ZAP70, VAV, VCP and other key signaling molecules (PubMed:16461343, PubMed:18056643). Associates with and probably dephosphorylates CBL. Dephosphorylates LCK at its activating 'Tyr-394' residue (PubMed:21719704). Dephosphorylates ZAP70 at its activating 'Tyr-493' residue (PubMed:16461343). Dephosphorylates the immune system activator SKAP2 (PubMed:21719704). Positively regulates toll-like receptor (TLR)-induced type 1 interferon production (PubMed:23871208). Promotes host antiviral responses mediated by type 1 interferon (By similarity). Regulates NOD2-induced pro-inflammatory cytokine secretion and autophagy (PubMed:23991106). Acts as an activator of NLRP3 inflammasome assembly by mediating dephosphorylation of 'Tyr-861' of NLRP3 (PubMed:27043286). 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cerevisiae.","date":"2020","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/32413406","citation_count":17,"is_preprint":false},{"pmid":"22952725","id":"PMC_22952725","title":"Biochemical and functional studies of lymphoid-specific tyrosine phosphatase (Lyp) variants S201F and R266W.","date":"2012","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/22952725","citation_count":17,"is_preprint":false},{"pmid":"20111888","id":"PMC_20111888","title":"LYP, a novel bestatin derivative, inhibits cell growth and suppresses APN/CD13 activity in human ovarian carcinoma cells more potently than bestatin.","date":"2010","source":"Investigational new drugs","url":"https://pubmed.ncbi.nlm.nih.gov/20111888","citation_count":17,"is_preprint":false},{"pmid":"16678435","id":"PMC_16678435","title":"Are other protein tyrosine phosphatases than PTPN22 associated with autoimmunity?","date":"2006","source":"Seminars in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/16678435","citation_count":17,"is_preprint":false},{"pmid":"30139951","id":"PMC_30139951","title":"The protein tyrosine phosphatase PTPN22 negatively regulates presentation of immune complex derived antigens.","date":"2018","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/30139951","citation_count":17,"is_preprint":false},{"pmid":"27034343","id":"PMC_27034343","title":"Autoimmune Variant PTPN22 C1858T Is Associated With Impaired Responses to Influenza Vaccination.","date":"2016","source":"The Journal of infectious diseases","url":"https://pubmed.ncbi.nlm.nih.gov/27034343","citation_count":17,"is_preprint":false},{"pmid":"21597364","id":"PMC_21597364","title":"The role of PTPN22 gene polymorphism in childhood immune thrombocytopenic purpura.","date":"2011","source":"Blood coagulation & fibrinolysis : an international journal in haemostasis and thrombosis","url":"https://pubmed.ncbi.nlm.nih.gov/21597364","citation_count":17,"is_preprint":false},{"pmid":"9243099","id":"PMC_9243099","title":"The lymphopenia (lyp) gene controls the intrathymic cytokine ratio in congenic BioBreeding rats.","date":"1997","source":"Diabetologia","url":"https://pubmed.ncbi.nlm.nih.gov/9243099","citation_count":17,"is_preprint":false},{"pmid":"24816862","id":"PMC_24816862","title":"A functional variant of PTPN22 confers risk for Vogt-Koyanagi-Harada syndrome but not for ankylosing spondylitis.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24816862","citation_count":17,"is_preprint":false},{"pmid":"34417261","id":"PMC_34417261","title":"Proautoimmune Allele of Tyrosine Phosphatase, PTPN22, Enhances Tumor Immunity.","date":"2021","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/34417261","citation_count":16,"is_preprint":false},{"pmid":"28948613","id":"PMC_28948613","title":"Protein tyrosine phosphatase PTPN22 regulates IL-1β dependent Th17 responses by modulating dectin-1 signaling in mice.","date":"2017","source":"European journal of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/28948613","citation_count":16,"is_preprint":false},{"pmid":"32469452","id":"PMC_32469452","title":"PTPN22 interacts with EB1 to regulate T-cell receptor signaling.","date":"2020","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/32469452","citation_count":16,"is_preprint":false},{"pmid":"21688149","id":"PMC_21688149","title":"The association between the PTPN22 C1858T polymorphism and systemic sclerosis: a meta-analysis.","date":"2011","source":"Molecular biology 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of a novel LyP-1-containing self-microemulsifying drug delivery system (SMEDDS) for active targeting to breast cancer.","date":"2019","source":"European journal of pharmaceutics and biopharmaceutics : official journal of Arbeitsgemeinschaft fur Pharmazeutische Verfahrenstechnik e.V","url":"https://pubmed.ncbi.nlm.nih.gov/30660694","citation_count":16,"is_preprint":false},{"pmid":"17230194","id":"PMC_17230194","title":"Expression of human PTPN22 alleles.","date":"2007","source":"Genes and immunity","url":"https://pubmed.ncbi.nlm.nih.gov/17230194","citation_count":15,"is_preprint":false},{"pmid":"23637320","id":"PMC_23637320","title":"Metaanalysis of the association of smoking and PTPN22 R620W genotype on autoantibody status and radiological erosions in rheumatoid arthritis.","date":"2013","source":"The Journal of rheumatology","url":"https://pubmed.ncbi.nlm.nih.gov/23637320","citation_count":15,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":47738,"output_tokens":5397,"usd":0.112085},"stage2":{"model":"claude-opus-4-6","input_tokens":8920,"output_tokens":3599,"usd":0.201863},"total_usd":0.313948,"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\": 1999,\n      \"finding\": \"LYP/PTPN22 is an intracellular protein tyrosine phosphatase expressed predominantly in lymphoid tissues; it contains a single catalytic PTP domain and four proline-rich SH3-binding motifs; it is constitutively associated with the proto-oncogene c-Cbl in thymocytes and T cells, and overexpression of LYP reduces Cbl tyrosine phosphorylation, indicating Cbl is a substrate.\",\n      \"method\": \"Molecular cloning, co-immunoprecipitation, overexpression in T cells with phosphorylation assays\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — reciprocal Co-IP and functional overexpression assay in a single lab; foundational characterization paper\",\n      \"pmids\": [\"10068674\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"PTPN22 directly dephosphorylates the activating tyrosines of Lck (Tyr-394) and Zap70 (Tyr-493), but not their regulatory tyrosines; TCRζ is also a direct substrate dephosphorylated by PTPN22 both in vitro and in cells; additional substrates include Vav, CD3ε, and valosin-containing protein, identified by substrate-trapping mass spectrometry.\",\n      \"method\": \"Substrate trapping with catalytically inactive PTPN22-D195A/C227S mutant coupled to mass spectrometry, in vitro dephosphorylation assays with purified recombinant proteins, co-immunoprecipitation in 293T cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with purified proteins, mutagenesis-based substrate trap, and cell-based validation; multiple orthogonal methods in one study\",\n      \"pmids\": [\"16461343\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Crystal structure of LYP (PTPN22) reveals a Lyp-specific insert region (S35TKYKADK42) that can adopt loop or helical conformations; PKC phosphorylates LYP exclusively at Ser-35 both in vitro and in vivo, and Ser-35 phosphorylation impairs LYP's ability to inactivate Src family kinases and down-regulate TCR signaling; a bidentate salicylic acid-based inhibitor I-C11 was identified that binds both the active site and a peripheral site unique to LYP.\",\n      \"method\": \"X-ray crystallography, in vitro kinase assay (PKC phosphorylation of Ser-35), site-directed mutagenesis, cellular TCR signaling assays, small-molecule inhibitor characterization\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure combined with mutagenesis, in vitro and in vivo phosphorylation assays, and functional TCR signaling readout; multiple orthogonal methods in one study\",\n      \"pmids\": [\"18056643\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"LYP inhibits T-cell activation when dissociated from CSK; dissociation of the LYP-CSK complex is required for recruitment of LYP to the plasma membrane where it downmodulates TCR signaling; the disease-associated R620W variant, which cannot bind CSK, shows reduced TCR-mediated signaling consistent with constitutive LYP activity at the membrane.\",\n      \"method\": \"Live-cell imaging of LYP-CSK complex spatiotemporal dynamics, selective chemical LYP inhibitor, T-cell activation assays\",\n      \"journal\": \"Nature chemical biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct localization experiment tied to functional consequence, chemical probe validation, multiple orthogonal methods\",\n      \"pmids\": [\"22426112\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PTPN22 directly associates with TRAF3 and promotes TRAF3 lysine-63-linked ubiquitination, selectively enhancing TLR-driven type I interferon production in myeloid cells; the disease-associated PTPN22-R620W variant fails to promote TRAF3 ubiquitination and type I IFN upregulation.\",\n      \"method\": \"Co-immunoprecipitation of PTPN22 with TRAF3, ubiquitination assays, Ptpn22-knockout mouse studies with TLR agonist stimulation, colitis and arthritis models\",\n      \"journal\": \"Immunity\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, KO mouse with defined phenotypic readout, biochemical ubiquitination assay, replicated across multiple disease models\",\n      \"pmids\": [\"23871208\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The disease-linked PEP-R619W knockin variant (mouse ortholog of human LYP-R620W) renders lymphocytes hyperresponsive to antigen-receptor engagement with a distinct phosphotyrosine substrate profile, promotes effector T cell and B cell expansion, disrupts B cell selection, and leads to development of autoantibodies and systemic autoimmunity in aged mice.\",\n      \"method\": \"Knockin mouse generation, flow cytometric immunophenotyping, antigen-receptor stimulation assays, phosphoproteomic profiling, autoantibody detection\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — precise genetic knockin model with multiple orthogonal readouts (cellular, biochemical, serological); strong mechanistic evidence\",\n      \"pmids\": [\"23619366\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"LYP/PTPN22 is expressed in myeloid cells (granulocytes, monocytes) in addition to lymphocytes and localizes to the cytosol; overexpression of LYP reduces phosphorylation of Cbl, Bcr-Abl, Erk1/2, and CrkL and suppresses anchorage-independent growth of CML cells, suggesting LYP antagonizes Bcr-Abl signaling.\",\n      \"method\": \"RT-PCR expression profiling, subcellular fractionation, overexpression in CML cell lines with phosphorylation assays, colony formation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct localization by fractionation with functional consequence; overexpression data from single lab\",\n      \"pmids\": [\"12764153\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"An alternative splice isoform of PTPN22, PTPN22.6, lacks nearly the entire phosphatase domain and functions as a dominant-negative isoform of full-length PTPN22; expression of the W620 variant of PTPN22.6 (but not PTPN22.1-W620) leads to hyperactivation of human T cells.\",\n      \"method\": \"Identification of splice variant by cloning, dominant-negative overexpression assays in T cells, T-cell activation readouts\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single lab, overexpression system with functional readout; no reconstitution with purified proteins\",\n      \"pmids\": [\"22427951\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PTPN22 suppresses M1 macrophage polarization and reciprocally promotes M2-associated gene expression; PTPN22-deficient mice develop more severe dextran sulfate sodium-induced colitis with increased M1 macrophage polarization in the intestine; PTPN22 also suppresses its own expression in M1 but not M2 macrophages (autoinhibition).\",\n      \"method\": \"Ptpn22-knockout mice, dextran sulfate sodium colitis model, gene expression analysis of M1/M2 markers, PTPN22 knockdown in human macrophages\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse with defined cellular and disease phenotype; multiple readouts from single lab\",\n      \"pmids\": [\"23913970\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PTPN22 is required for full FcγR-mediated neutrophil activation; Ptpn22-/- neutrophils show reduced adhesion, ROS production, and degranulation upon immune complex stimulation; PTPN22 regulates tyrosine phosphorylation of Lyn and Syk in neutrophils; Ptpn22-/- mice are protected from immune complex-mediated arthritis.\",\n      \"method\": \"Ptpn22-knockout mouse neutrophil functional assays (adhesion, ROS, degranulation), phosphorylation analysis of Lyn and Syk, serum transfer arthritis model\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse with multiple defined functional readouts plus in vivo disease model; biochemical mechanism (Lyn/Syk phosphorylation) identified\",\n      \"pmids\": [\"27807193\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Loss of PTPN22 increases the size of the regulatory T cell (Treg) compartment by upregulating GITR expression and enhancing GITR signaling, leading to prolonged Treg survival rather than accelerated division; GITR ligand blockade prevents Treg expansion caused by Ptpn22 knockdown.\",\n      \"method\": \"Ptpn22 siRNA knockdown in mice, GITR ligand blockade, apoptosis and proliferation assays of Treg cells, flow cytometric phenotyping\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — genetic knockdown with mechanistic follow-up (GITR blockade rescue), single lab\",\n      \"pmids\": [\"26810223\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TRAF3 associates with PTPN22 and regulates its recruitment to the TCR/CD28 complex; loss of TRAF3 results in increased amounts of PTPN22 in T cell membrane fractions and decreased association of PTPN22 with CSK, thereby reducing activating phosphorylation of Lck.\",\n      \"method\": \"Co-immunoprecipitation of TRAF3 with PTPN22 and CSK, membrane fractionation of TRAF3-deficient T cells, phosphorylation analysis of Lck\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP and fractionation with genetic KO; single lab but multiple biochemical readouts\",\n      \"pmids\": [\"28522807\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PTPN22 negatively regulates dectin-1 signaling in dendritic cells by restraining Syk and Erk phosphorylation; Ptpn22-/- BMDCs show enhanced IL-1β secretion and drive increased IL-17 T-cell responses upon dectin-1 stimulation; the Ptpn22-R619W variant also increases IL-1β secretion in this context, acting as a loss-of-function allele for dectin-1 regulation.\",\n      \"method\": \"Ptpn22-/- and Ptpn22-R619W knockin bone marrow-derived dendritic cells, dectin-1 agonist (curdlan) stimulation, Syk/Erk immunoblotting, in vitro and in vivo T-cell co-culture assays\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO and knockin mouse cells, biochemical signaling readouts plus functional T-cell assays; single lab\",\n      \"pmids\": [\"28948613\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PTPN22 negatively regulates LFA-1-dependent Th1 responses through two mechanisms: (1) a T cell-intrinsic mechanism whereby Ptpn22-/- T cells have enhanced ability to engage ICAM-1 at the immune synapse; (2) a T cell-extrinsic mechanism whereby Ptpn22-/- dendritic cells enhance Th1 development in an LFA-1/ICAM-dependent manner.\",\n      \"method\": \"Ptpn22-/- mice, planar lipid bilayer immune synapse assays, DC-T cell conjugate formation assays, in vitro and in vivo Th1 differentiation assays with LFA-1 blockade\",\n      \"journal\": \"Journal of autoimmunity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse with multiple mechanistic readouts including direct imaging at immune synapse; single lab\",\n      \"pmids\": [\"30054208\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PTPN22 negatively regulates FcγR-mediated antigen presentation in dendritic cells; Ptpn22-/- BMDCs show enhanced uptake and presentation of immune complex-derived antigens and form more DC-T cell conjugates, leading to enhanced T cell proliferation.\",\n      \"method\": \"Ptpn22-/- bone marrow-derived DCs pulsed with ovalbumin:anti-ovalbumin immune complexes, T cell co-culture proliferation assays, DC-T cell conjugate quantification\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse cells with defined functional assay; single lab\",\n      \"pmids\": [\"30139951\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PTPN22 interacts with end-binding protein 1 (EB1) via the P1 proline-rich domain of PTPN22 (competing with CSK binding); PTPN22 dephosphorylates EB1 at tyrosine-247, which reduces expression of T cell activation markers CD25 and CD69, decreases phosphorylation of ZAP-70, LAT, and Erk, and reduces NFAT activation and IL-2 secretion; the R620W variant does not affect EB1 association.\",\n      \"method\": \"Yeast two-hybrid screen, mass spectrometry, co-immunoprecipitation, site-directed mutagenesis, in vitro dephosphorylation assay, T-cell activation assays\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro dephosphorylation assay plus multiple cell-based readouts; single lab\",\n      \"pmids\": [\"32469452\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PTPN22 activity is redox-regulated through the non-catalytic Cys129 residue, which forms a disulfide with catalytic Cys227; a C129S knock-in mouse shows enhanced TCR signaling, stronger T-cell-dependent inflammation, and more severe autoimmune arthritis; thioredoxin can directly reduce the native PTPN22 disulfide to reactivate the enzyme; the functional effects depend on the NOX2 component Ncf1.\",\n      \"method\": \"C129S knock-in mouse, Ncf1-mutant double-mutant epistasis, in vitro activity assays with purified PTPN22 proteins, thioredoxin reductase assays, autoimmune arthritis model\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro biochemical reconstitution with purified proteins, genetic epistasis with Ncf1, knock-in mouse with disease phenotype; multiple orthogonal methods\",\n      \"pmids\": [\"35587260\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PTPN22 is expressed in human and mouse platelets and negatively regulates platelet function; PTPN22-deficient mice show enhanced platelet aggregation, granule secretion, calcium mobilization, and accelerated arterial thrombus formation; PTPN22 interacts with phosphorylated PDE5A (Ser92) and dephosphorylates it, modulating cGMP signaling; purified PTPN22 (but not catalytic-dead C227S mutant) has intrinsic serine phosphatase activity toward PDE5A.\",\n      \"method\": \"PTPN22-/- mouse model, phosphoproteomic analysis, co-immunoprecipitation of PTPN22 with phospho-PDE5A, in vitro phosphatase assay with purified proteins and C227S mutant, arterial thrombosis model\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro reconstitution with purified enzyme + mutagenesis, KO mouse with multiple functional readouts, phosphoproteomic substrate identification; multiple orthogonal methods\",\n      \"pmids\": [\"35767715\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"LYP (encoded by PTPN22) interacts with CSK through its P1 and P2 proline-rich motifs and CSK's SH3 and SH2 domains; this interaction is inducible upon TCR stimulation rather than constitutive; abrogating LYP/CSK interaction does not preclude regulation of TCR signaling by these proteins.\",\n      \"method\": \"Co-immunoprecipitation, domain mapping with truncation mutants, TCR stimulation time-course experiments\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — Co-IP with domain mapping; single lab, contradicts earlier model of constitutive interaction\",\n      \"pmids\": [\"23359562\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The Lyp variants R263Q and R266W both have significantly reduced phosphatase activity compared to wild-type Lyp; R266W severely impairs catalytic activity likely by perturbing the Q-loop or WPD loop; both are loss-of-function variants in T cell signaling assays.\",\n      \"method\": \"In vitro kinetic phosphatase assays with purified recombinant Lyp variants, structural modeling, T cell signaling functional assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro biochemical assay with purified proteins plus cell-based functional assay; single lab\",\n      \"pmids\": [\"22952725\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PTPN22/LYP is a lymphoid-enriched non-receptor protein tyrosine phosphatase that dephosphorylates and inactivates key TCR-proximal kinases (Lck at Tyr-394, ZAP70 at Tyr-493, TCRζ) and is redox-regulated via a Cys129–Cys227 disulfide; it is recruited to the plasma membrane upon dissociation from its binding partner CSK (which requires the P1 proline-rich motif), where it attenuates TCR signaling, and also functions in myeloid cells by promoting TRAF3 K63-ubiquitination to potentiate TLR-driven type I IFN responses, regulating FcγR-mediated neutrophil activation through Lyn/Syk dephosphorylation, modulating macrophage M1/M2 polarization, and negatively regulating platelet activation via dephosphorylation of PDE5A; the autoimmunity-associated R620W variant disrupts CSK binding, impairs TRAF3 ubiquitination and type I IFN production, and confers hyperresponsiveness in lymphocytes and altered innate immune signaling.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PTPN22 (LYP) is a lymphoid- and myeloid-expressed non-receptor protein tyrosine phosphatase that serves as a central negative regulator of antigen receptor and innate immune signaling across multiple hematopoietic lineages. Its catalytic domain directly dephosphorylates activating tyrosines on TCR-proximal kinases Lck (Tyr-394) and ZAP-70 (Tyr-493), as well as TCRζ, Vav, and CD3ε, thereby attenuating T cell activation; dissociation from its cytosolic partner CSK is required for PTPN22 translocation to the plasma membrane where it exerts this inhibitory function [PMID:16461343, PMID:22426112]. Beyond lymphocytes, PTPN22 promotes TRAF3 K63-linked ubiquitination to enhance TLR-driven type I interferon production in myeloid cells, regulates FcγR-mediated neutrophil activation through Lyn/Syk dephosphorylation, restrains dectin-1 signaling in dendritic cells, modulates macrophage M1/M2 polarization, and negatively regulates platelet activation via dephosphorylation of PDE5A [PMID:23871208, PMID:27807193, PMID:28948613, PMID:35767715]. Enzyme activity is redox-regulated through a Cys129–Cys227 disulfide bond reversible by thioredoxin, and PKC-mediated phosphorylation at Ser-35 impairs its capacity to inactivate Src-family kinases [PMID:35587260, PMID:18056643]. The autoimmunity-associated R620W variant disrupts CSK binding, impairs TRAF3 ubiquitination, and confers lymphocyte hyperresponsiveness leading to autoantibody production and systemic autoimmunity in knockin mice [PMID:23619366, PMID:23871208].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Establishing PTPN22 as a lymphoid PTP with proline-rich SH3-binding motifs and identifying c-Cbl as an initial interaction partner and putative substrate defined the gene as a T-cell signaling phosphatase.\",\n      \"evidence\": \"Molecular cloning, co-immunoprecipitation in thymocytes and T cells, overexpression phosphorylation assays\",\n      \"pmids\": [\"10068674\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"c-Cbl as substrate was based on overexpression Co-IP without purified-protein reconstitution\", \"physiological relevance of Cbl dephosphorylation not tested in loss-of-function setting\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Substrate-trapping and in vitro reconstitution identified the precise TCR-proximal substrates — Lck Tyr-394, ZAP-70 Tyr-493, and TCRζ — establishing PTPN22 as a direct negative regulator of the earliest TCR signaling events.\",\n      \"evidence\": \"Catalytically inactive D195A/C227S substrate-trap coupled to mass spectrometry, in vitro dephosphorylation with purified proteins, 293T cell validation\",\n      \"pmids\": [\"16461343\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"relative contributions of individual substrate dephosphorylation events to TCR output not dissected\", \"whether PTPN22 acts on these substrates simultaneously or sequentially in vivo unknown\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"The crystal structure revealed a Lyp-specific insert whose Ser-35 is phosphorylated by PKC, providing the first post-translational regulatory mechanism that tunes PTPN22 phosphatase activity and consequently TCR signal strength.\",\n      \"evidence\": \"X-ray crystallography, in vitro PKC kinase assay, mutagenesis, cellular TCR signaling readouts\",\n      \"pmids\": [\"18056643\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"which PKC isoform(s) phosphorylate Ser-35 in physiological settings not defined\", \"structural basis for how Ser-35 phosphorylation alters catalytic activity not resolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Live-cell imaging resolved a longstanding question about how PTPN22 accesses its membrane-proximal substrates: dissociation from the cytosolic CSK complex is required for PTPN22 membrane recruitment, and the R620W variant, constitutively free of CSK, is hyperactive at the membrane.\",\n      \"evidence\": \"Live-cell imaging of LYP-CSK dynamics, selective chemical LYP inhibitor, T-cell activation assays\",\n      \"pmids\": [\"22426112\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"signals triggering CSK-PTPN22 dissociation upon TCR engagement not identified\", \"whether additional scaffolds recruit free PTPN22 to the membrane unknown\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Characterization of R263Q and R266W variants as loss-of-function alleles demonstrated that structural integrity of the Q-loop/WPD-loop region is essential for catalytic activity, establishing a structure-function framework for disease-associated variants.\",\n      \"evidence\": \"In vitro kinetic assays with purified recombinant variants, structural modeling, T-cell signaling assays\",\n      \"pmids\": [\"22952725\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"no crystal structures of these variants obtained\", \"population-level disease associations for R263Q/R266W not established\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"The R619W knockin mouse (ortholog of human R620W) provided definitive in vivo evidence that the variant causes lymphocyte hyperresponsiveness, disrupted B cell selection, and spontaneous autoimmunity, directly linking PTPN22 loss-of-interaction to autoimmune pathogenesis.\",\n      \"evidence\": \"Knockin mouse, flow cytometry, phosphoproteomic profiling, autoantibody detection\",\n      \"pmids\": [\"23619366\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"which specific phosphoproteomic changes are causally responsible for autoimmunity not determined\", \"epistatic modifiers required for penetrant disease not identified\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Discovery that PTPN22 promotes TRAF3 K63-ubiquitination to enhance type I IFN production established a phosphatase-independent scaffolding function in myeloid innate immunity, fundamentally expanding PTPN22's role beyond TCR signaling.\",\n      \"evidence\": \"Co-immunoprecipitation, ubiquitination assays, Ptpn22-KO mice stimulated with TLR agonists, colitis and arthritis models\",\n      \"pmids\": [\"23871208\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"E3 ligase catalyzing TRAF3 K63-ubiquitination recruited by PTPN22 not identified\", \"whether the phosphatase domain is entirely dispensable for this function not tested\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"The finding that PTPN22 suppresses M1 macrophage polarization and promotes M2 gene expression extended its innate immune role to macrophage functional polarization, with therapeutic implications for inflammatory bowel disease.\",\n      \"evidence\": \"Ptpn22-KO mice in DSS colitis model, M1/M2 gene expression analysis, human macrophage knockdown\",\n      \"pmids\": [\"23913970\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"direct substrates mediating M1/M2 skewing not identified\", \"whether this reflects phosphatase activity or scaffolding unknown\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstration that PTPN22 is required for full FcγR-mediated neutrophil activation via Lyn/Syk dephosphorylation revealed a context-dependent positive regulatory role — opposite to its inhibitory function in T cells — and provided protection from immune complex arthritis.\",\n      \"evidence\": \"Ptpn22-KO neutrophil functional assays, Lyn/Syk phosphorylation analysis, serum transfer arthritis model\",\n      \"pmids\": [\"27807193\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"mechanism by which PTPN22-mediated Lyn/Syk dephosphorylation promotes rather than inhibits neutrophil activation not fully explained\", \"whether specific Lyn/Syk tyrosine sites differ from those in T cells not mapped\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"TRAF3 was shown to reciprocally regulate PTPN22 by controlling its membrane recruitment and CSK association, establishing a bidirectional TRAF3–PTPN22 regulatory axis in T cells.\",\n      \"evidence\": \"Co-immunoprecipitation, membrane fractionation of TRAF3-deficient T cells, Lck phosphorylation analysis\",\n      \"pmids\": [\"28522807\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"structural basis of TRAF3-PTPN22 interaction not defined\", \"whether TRAF3 regulation of PTPN22 localization operates in myeloid cells unknown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identification of EB1 as a PTPN22 substrate dephosphorylated at Tyr-247 revealed a non-canonical mechanism linking PTPN22 to microtubule-associated signaling and T cell activation, expanding its substrate repertoire beyond canonical TCR kinases.\",\n      \"evidence\": \"Yeast two-hybrid, mass spectrometry, in vitro dephosphorylation, T-cell activation assays\",\n      \"pmids\": [\"32469452\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"physiological consequence of EB1-Tyr247 dephosphorylation on microtubule dynamics not tested\", \"in vivo relevance using loss-of-function models not established\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Redox regulation of PTPN22 via a Cys129–Cys227 disulfide bond, reversible by thioredoxin and dependent on NOX2/Ncf1-generated ROS, established reactive oxygen species as physiological modulators of PTPN22 activity and TCR signaling strength.\",\n      \"evidence\": \"C129S knock-in mouse, Ncf1 epistasis, in vitro thioredoxin reductase assay with purified protein, autoimmune arthritis model\",\n      \"pmids\": [\"35587260\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"kinetics and spatial dynamics of disulfide formation/reduction in intact T cells not measured\", \"whether other PTPs in the same signaling cascade are co-regulated by the same ROS pool unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Discovery that PTPN22 dephosphorylates PDE5A at Ser-92 in platelets — exhibiting serine phosphatase activity — and negatively regulates platelet aggregation and thrombus formation extended its function to hemostasis and revealed unexpected dual-specificity catalysis.\",\n      \"evidence\": \"PTPN22-KO mouse platelets, phosphoproteomic analysis, in vitro phosphatase assay with purified PTPN22 and C227S mutant, arterial thrombosis model\",\n      \"pmids\": [\"35767715\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"structural basis for serine phosphatase activity in a classical tyrosine phosphatase not resolved\", \"whether dual-specificity activity extends to other substrates unknown\", \"platelet phenotype relevance to human thrombotic disease not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the signals that trigger CSK-PTPN22 dissociation upon receptor engagement, the structural basis for PTPN22's dual tyrosine/serine phosphatase activity, the identity of the E3 ligase mediating TRAF3 ubiquitination downstream of PTPN22, and how context-dependent switching between positive and negative regulation is achieved across cell types.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"no structural model of PTPN22-CSK or PTPN22-TRAF3 complexes\", \"mechanism of cell-type-specific functional polarity (inhibitory in T cells, activating in neutrophils) not explained\", \"therapeutic targeting strategies remain preclinical\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1, 2, 9, 15, 17, 19]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [3, 4, 8, 10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [3, 6]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [1, 3, 4, 5, 9, 12, 13, 14]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 2, 3, 11, 15, 16]},\n      {\"term_id\": \"R-HSA-109582\", \"supporting_discovery_ids\": [17]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [5, 8]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"CSK\", \"TRAF3\", \"LCK\", \"ZAP70\", \"MAPK1E1\", \"SYK\", \"LYN\", \"PDE5A\"],\n    \"other_free_text\": []\n  }\n}\n```"}