{"gene":"PTPN22","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":2006,"finding":"PTPN22 (LYP) dephosphorylates Lck at its activating tyrosine Tyr-394 and Zap70 at Tyr-493 (activating residues), but not at regulatory tyrosines Tyr-505 (Lck) or Tyr-319 (Zap70). TCRzeta was also identified as a direct substrate: native PTPN22 dephosphorylated TCRzeta in vitro and in cells, and a substrate-trap mutant (D195A/C227S) co-immunoprecipitated with TCRzeta. Additional novel substrates identified by substrate trapping coupled with mass spectrometry included Vav, CD3epsilon, and valosin-containing protein.","method":"Substrate trapping (PTPN22-D195A/C227S mutant) coupled with mass spectrometry in pervanadate-stimulated Jurkat cells; 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 / Strong — in vitro reconstitution with purified proteins, substrate-trap mutagenesis, mass spectrometry identification, and cellular co-IP in a single rigorous study","pmids":["16461343"],"is_preprint":false},{"year":2013,"finding":"PTPN22 selectively promotes TLR-induced type I interferon (IFN) production in myeloid cells by directly associating with TRAF3 and promoting TRAF3 lysine-63-linked ubiquitination. The disease-associated PTPN22-W620 variant failed to promote TRAF3 ubiquitination and type I IFN upregulation.","method":"Co-immunoprecipitation (PTPN22–TRAF3 interaction); ubiquitination assays; Ptpn22-deficient mouse models; TLR stimulation of myeloid cells; in vivo colitis and arthritis models","journal":"Immunity","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, biochemical ubiquitination assay, genetic KO mouse models with defined phenotypic readouts, multiple orthogonal methods in one study","pmids":["23871208"],"is_preprint":false},{"year":2013,"finding":"The PEP-R619W knockin mouse (ortholog of human LYP-R620W) shows normal protein stability but hyperresponsive lymphocytes upon antigen-receptor engagement, with a distinct profile of tyrosine-phosphorylated substrates. Aged knockin mice develop effector T cell expansion, B cell expansion (transitional, germinal center, age-related), autoantibodies, and systemic autoimmunity. B lineage-restricted variant expression is sufficient to promote autoimmunity.","method":"Knockin mouse generation; lymphocyte activation assays; phosphoproteomic profiling; flow cytometry of lymphocyte subsets; autoantibody detection","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — knockin mouse with defined cellular and molecular phenotypes, multiple orthogonal readouts, single rigorous study","pmids":["23619366"],"is_preprint":false},{"year":2013,"finding":"PTPN22 suppresses M1 macrophage polarization and reciprocally promotes M2-associated gene expression. PTPN22-deficient mice develop severe DSS-induced colitis with intestinal macrophages expressing higher M1 and lower M2 genes. An autoinhibition mechanism was identified whereby PTPN22 suppresses its own expression in M1 but not M2 macrophages.","method":"PTPN22-deficient mice; DSS colitis model; macrophage polarization assays; gene expression analysis; human macrophage genotype-expression correlation","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mouse with defined cellular phenotype and in vitro macrophage assays, single lab","pmids":["23913970"],"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; dominant-negative functional assays in human T cells; comparison of full-length vs. splice isoform activity","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional cell-based assays with defined isoform constructs, single lab, multiple cellular readouts","pmids":["22427951"],"is_preprint":false},{"year":2017,"finding":"Loss of PTPN22 results in decreased NLRP3 inflammasome activation via enhanced NLRP3 phosphorylation, and this inhibitory effect is dependent on autophagy: phosphorylated NLRP3 is sequestered into autophagosomes (phagophores), and loss of autophagy abolishes the inhibitory effect on NLRP3 activation observed upon loss of PTPN22.","method":"PTPN22 KO macrophages; autophagy inhibition; immunoprecipitation to detect NLRP3 in autophagosomes; NLRP3 phosphorylation assays; IL-1β secretion assays","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO cells with autophagy genetic/pharmacological manipulation, biochemical fractionation, single lab","pmids":["28786745"],"is_preprint":false},{"year":2017,"finding":"TRAF3 associates with PTPN22 and regulates its TCR/CD28-induced localization; loss of TRAF3 results in increased amounts of PTPN22 in T cell membrane fractions and decreased association of PTPN22 with CSK. TRAF3 thus promotes T cell activation partly by preventing membrane localization of PTPN22.","method":"Co-immunoprecipitation; membrane fractionation of TRAF3-deficient mouse and human T cells; phosphorylation assays for Lck","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, subcellular fractionation with functional context, single lab","pmids":["28522807"],"is_preprint":false},{"year":2016,"finding":"PTPN22 is a critical regulator of FcγR-mediated neutrophil activation: Ptpn22-/- neutrophils show reduced adhesion, reactive oxygen species production, and degranulation upon stimulation with immobilized immune complexes. Tyrosine phosphorylation of Lyn and Syk was altered in Ptpn22-/- neutrophils. Ptpn22-/- mice were protected from immune complex-mediated arthritis.","method":"Ptpn22-/- mice; neutrophil functional assays (ROS, degranulation, adhesion); phosphorylation analysis of Lyn and Syk; in vivo serum transfer arthritis model","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mouse with defined cellular and in vivo phenotypes, multiple orthogonal readouts, single lab","pmids":["27807193"],"is_preprint":false},{"year":2016,"finding":"Ptpn22 knockdown in mice promotes Treg cell expansion by upregulating GITR and increasing GITR signaling, prolonging Treg survival (decreased apoptosis) rather than accelerating cell division. This expansion is dependent on GITR signaling, as GITR-ligand blockade prevented Treg expansion caused by Ptpn22 knockdown. Loss of Ptpn22 also increased the proportion of effector Tregs (CD44hiCD62Llo) at the expense of central Tregs.","method":"Ptpn22 siRNA knockdown in mice; GITR expression and signaling analysis; apoptosis assays; GITR-ligand blockade; flow cytometry of Treg subsets","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KD with multiple orthogonal readouts and GITR-blockade rescue experiment, single lab","pmids":["26810223"],"is_preprint":false},{"year":2020,"finding":"PTPN22 is phosphorylated at Ser751 by PKCα in Jurkat and primary human T cells upon activation. This phosphorylation prolongs PTPN22 half-life by inhibiting K48-linked ubiquitination, impairs its recruitment to the plasma membrane (necessary for inhibiting proximal TCR signaling), and enhances its interaction with CSK. The R620W variant retains Ser751 phosphorylation-dependent protection from degradation but its membrane recruitment is unaffected by Ser751 phosphorylation.","method":"Mass spectrometry identification of phosphorylation site; PKCα kinase assays; ubiquitination assays; plasma membrane fractionation; co-immunoprecipitation with CSK; phosphomimetic/non-phosphorylatable mutant analysis","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 1 / Strong — mass spectrometry, in vitro kinase assay, ubiquitination assay, subcellular fractionation, Co-IP, mutagenesis — multiple orthogonal Tier 1 methods in one study","pmids":["32184287"],"is_preprint":false},{"year":2022,"finding":"PTPN22 is expressed in both human and mouse platelets and negatively regulates platelet function and arterial thrombus formation. PTPN22 deficiency accelerates arterial thrombosis and enhances platelet aggregation, granule secretion, calcium mobilization, and clot retraction. Mechanistically, PTPN22 interacts with phosphorylated PDE5A (Ser92) and dephosphorylates it in activated platelets; reduced PDE5A phosphorylation is associated with increased cGMP signaling (vasodilator-stimulated phosphoprotein). Purified PTPN22, but not the catalytic mutant C227S, possesses intrinsic serine phosphatase activity.","method":"PTPN22-/- mice; tail-bleeding time; in vivo thrombosis models; quantitative phosphoproteomics; co-immunoprecipitation (PTPN22–PDE5A); in vitro phosphatase assay with purified proteins and C227S mutant; human platelet inhibition experiments","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with purified proteins and catalytic mutant, phosphoproteomics, Co-IP, KO mouse in vivo phenotypes, multiple orthogonal methods","pmids":["35767715"],"is_preprint":false},{"year":2020,"finding":"PTPN22 interacts with EB1 (end-binding protein 1) via the P1 domain of PTPN22, competing with CSK for the same binding domain. The R620W variant does not affect EB1 association. PTPN22 dephosphorylates EB1 at tyrosine-247 (Y247), which decreases expression of T cell activation markers CD25 and CD69 and phosphorylation of ZAP-70, LAT, and Erk, leading to downregulation of NFAT and reduced IL-2 secretion.","method":"Yeast two-hybrid; mass spectrometry; co-immunoprecipitation; in vitro dephosphorylation assay; T cell activation assays with overexpression/knockdown constructs","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, yeast two-hybrid, in vitro dephosphorylation, cellular functional assays; single lab","pmids":["32469452"],"is_preprint":false},{"year":2022,"finding":"PTPN22 activity is regulated by oxidation via the non-catalytic Cys129 residue, which forms a disulfide with catalytic Cys227. A C129S knock-in mouse showed stronger T cell-dependent inflammatory responses and autoimmune arthritis due to enhanced TCR signaling. The C129S mutant PTPN22 was more sensitive to oxidation and less amenable to reductive reactivation by the thioredoxin system. The pro-inflammatory effect of the C129S mutation was neutralized by a mutation in Ncf1 (a NOX2 complex component), establishing functional interaction between PTPN22 and Ncf1/NOX2-derived reactive oxygen species.","method":"C129S knock-in mouse; T cell activation and arthritis assays; in vitro oxidation/activity assays with purified proteins; genetic epistasis with Ncf1 mutation; thioredoxin reductase reactivation assay","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Strong — knock-in mouse, in vitro biochemical assays with purified proteins, genetic epistasis (Ncf1 double mutant rescue), multiple orthogonal methods in one study","pmids":["35587260"],"is_preprint":false},{"year":2017,"finding":"PTPN22 regulates dectin-1 signaling in dendritic cells by modulating Syk and Erk phosphorylation. Ptpn22-/- BMDCs activated by the dectin-1 agonist curdlan showed enhanced Syk and Erk phosphorylation, increased IL-1β secretion, and enhanced IL-17 T cell responses in an IL-1β-dependent manner. BMDCs expressing the Ptpn22-R619W variant (mouse ortholog of R620W) also showed increased IL-1β and IL-17 responses, indicating that in the dectin-1 context Ptpn22-R619W operates as a loss-of-function variant.","method":"Ptpn22-/- and Ptpn22-R619W knock-in BMDC; dectin-1 agonist stimulation; immunoblotting for Syk and Erk phosphorylation; in vitro and in vivo T cell co-culture assays; IL-1β neutralization","journal":"European journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO and knock-in DCs with signaling biochemistry and functional cellular readouts, single lab","pmids":["28948613"],"is_preprint":false},{"year":2018,"finding":"PTPN22 negatively regulates FcγR-mediated antigen presentation in dendritic cells: Ptpn22-/- bone marrow-derived DCs pulsed with ovalbumin:anti-ovalbumin immune complexes have enhanced capability to present immune complex-derived antigens, induce T cell proliferation, and form DC-T cell conjugates.","method":"Ptpn22-/- BMDC; immune complex pulsing; DC-T cell co-culture with OT-II T cells; T cell proliferation assays; DC-T cell conjugate formation assays","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO cells with multiple cellular functional readouts, single lab","pmids":["30139951"],"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 limits LFA-1/ICAM-1-dependent immune synapse formation and DC-T cell conjugate formation; (2) a T cell-extrinsic mechanism whereby PTPN22 in dendritic cells limits LFA-1-dependent Th1 induction by DCs.","method":"Ptpn22-/- mice; in vitro anti-CD3/LFA-1 stimulation vs. anti-CD3/anti-CD28 stimulation; planar lipid bilayer immune synapse assays; DC-T cell conjugate assays; adoptive transfer experiments; LFA-1 blockade","journal":"Journal of autoimmunity","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO cells/mice with multiple in vitro and in vivo functional assays, LFA-1 blockade rescue, single lab","pmids":["30054208"],"is_preprint":false},{"year":2022,"finding":"TRAF3 enhances type I IFN signaling in CD4+ T cells by preventing recruitment of PTPN22 to the IFNAR complex, thereby enabling activation of JAK1 and STAT1 downstream of IFNAR.","method":"Co-immunoprecipitation of PTPN22 with IFNAR complex; TRAF3-deficient T cells; JAK1 and STAT1 phosphorylation assays; CD4+ T cell differentiation assays","journal":"Science signaling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, KO T cells with signaling readouts, single lab","pmids":["36166512"],"is_preprint":false},{"year":2016,"finding":"Loss of PTPN22 in SKG mice (which carry a hypomorphic ZAP70 allele) reduces the severity of mannan-induced autoimmune arthritis. Ptpn22 deficiency biases CD4+ Th cell differentiation away from the pathogenic Th17 lineage toward a Th1/Treg-focused response, without significantly altering thymocyte development or repertoire selection.","method":"SKG Ptpn22-/- double-mutant mice; mannan-induced arthritis model; flow cytometry of T cell subsets; Th17/Th1/Treg differentiation assays","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis in double-mutant mice with defined disease and cellular phenotypes, single lab","pmids":["27288531"],"is_preprint":false},{"year":2023,"finding":"CRISPR/Cas9 gene editing of PTPN22-R620W in primary human naive T cells shows that the risk variant (620W) enhances TCR signaling and activation markers following non-specific TCR engagement, phenocopying PTPN22 KO. Using patient-derived TCRs against the autoantigen IGRP, loss of PTPN22 function (KO or 620W) enhanced signaling specifically in T cells expressing a lower-avidity self-reactive TCR (but not high-avidity TCR), promoting enhanced proliferation and Th1 skewing.","method":"CRISPR/Cas9 gene editing with donor templates in human cord blood T cells; lentiviral TCR delivery; T cell activation assays; proliferation assays; cytokine profiling","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Strong — isogenic CRISPR-edited primary human T cells with disease-relevant TCRs, multiple orthogonal functional assays, rigorous controls","pmids":["36961507"],"is_preprint":false},{"year":2016,"finding":"PTPN22 has dual roles in CD8+ T cell responses: it promotes antigen-driven CD8 T cell expansion during acute LCMV infection by positively regulating IFN-α/STAT-1 signaling in T cells (Ptpn22-/- CD8 T cells show reduced STAT-1 upregulation and reduced STAT-1 phosphorylation in response to IFN-α); conversely, it inhibits homeostatic-driven proliferation (Ptpn22-/- CD8 T cells show increased expansion in lymphopenic hosts).","method":"LCMV infection of Ptpn22-/- mice; adoptive transfer into lymphopenic hosts; STAT-1 phosphorylation assays in response to IFN-α; flow cytometry of CD8 T cell subsets","journal":"Immunology and cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mouse with in vivo infection model, biochemical signaling assays, adoptive transfer; single lab","pmids":["27725666"],"is_preprint":false}],"current_model":"PTPN22 (LYP/PEP) is a hematopoietic-specific non-receptor protein tyrosine phosphatase that inhibits T cell receptor signaling by dephosphorylating activating residues on Lck (Tyr-394), ZAP70 (Tyr-493), TCRzeta, and EB1 (Tyr-247); its activity at the plasma membrane is regulated by PKCα-mediated Ser751 phosphorylation (which promotes CSK binding and inhibits membrane recruitment) and by redox regulation through a non-catalytic Cys129–Cys227 disulfide; beyond T cells, PTPN22 promotes TLR-driven type I IFN production in myeloid cells by facilitating TRAF3 K63-ubiquitination, regulates NLRP3 inflammasome activity via autophagy-dependent NLRP3 phosphorylation and sequestration, modulates FcγR signaling in neutrophils and dendritic cells, suppresses M1 macrophage polarization, expands regulatory T cells via GITR upregulation, and dephosphorylates PDE5A in platelets to limit arterial thrombosis; the disease-associated R620W variant disrupts CSK binding, impairs membrane-localized phosphatase activity, fails to promote TRAF3 ubiquitination and type I IFN responses, and enhances low-avidity self-reactive T cell signaling, collectively lowering the threshold for autoimmunity."},"narrative":{"mechanistic_narrative":"PTPN22 (LYP/PEP) is a hematopoietic non-receptor protein tyrosine phosphatase that raises the activation threshold of immune cells by dephosphorylating activating tyrosines in antigen-receptor and Fc-receptor signaling cascades [PMID:16461343, PMID:36961507]. In T cells it directly dephosphorylates the activating sites on Lck (Tyr-394) and ZAP70 (Tyr-493) while sparing their inhibitory tyrosines, and it acts on TCRzeta, Vav, and CD3epsilon, thereby attenuating proximal TCR signaling [PMID:16461343]. It also targets the microtubule end-binding protein EB1 at Tyr-247 through its P1 domain, dampening downstream ZAP-70/LAT/Erk activation, NFAT, and IL-2 output [PMID:32469452]. Its inhibitory action depends on recruitment to the plasma membrane and on association with CSK; PKCalpha-mediated Ser751 phosphorylation stabilizes PTPN22 against K48-ubiquitin-driven degradation while impairing membrane recruitment and enhancing CSK binding, and TRAF3 likewise restrains membrane localization to permit T cell activation [PMID:32184287, PMID:28522807]. PTPN22 catalytic activity is redox-controlled through a non-catalytic Cys129–catalytic Cys227 disulfide that, when disrupted, sensitizes the enzyme to NOX2/Ncf1-derived oxidation and heightens TCR-driven autoimmunity [PMID:35587260]. Beyond T cells, PTPN22 governs innate immune responses: it promotes TLR-induced type I interferon by facilitating K63-linked TRAF3 ubiquitination, restrains NLRP3 inflammasome activation by promoting autophagy-dependent sequestration of phosphorylated NLRP3, suppresses M1 macrophage polarization, and negatively regulates FcgammaR- and dectin-1-driven neutrophil and dendritic-cell effector functions [PMID:23871208, PMID:28786745, PMID:23913970, PMID:27807193, PMID:28948613, PMID:30139951]. It also expands regulatory T cells via GITR signaling and, outside immunity, dephosphorylates PDE5A in platelets to limit arterial thrombosis [PMID:26810223, PMID:35767715]. The autoimmunity-associated R620W (mouse R619W) variant disrupts CSK binding and membrane-localized phosphatase function, fails to promote TRAF3 ubiquitination and type I IFN responses, and selectively lowers the signaling threshold of low-avidity self-reactive T cells, establishing it as a loss-of-function risk allele for autoimmunity [PMID:23871208, PMID:23619366, PMID:36961507].","teleology":[{"year":2006,"claim":"Establishing PTPN22's direct substrates answered how it suppresses TCR signaling at the molecular level, showing selective removal of activating rather than inhibitory phosphotyrosines.","evidence":"substrate-trap mutagenesis with mass spectrometry, in vitro dephosphorylation of purified proteins, and co-IP in Jurkat/293T cells","pmids":["16461343"],"confidence":"High","gaps":["Did not define which substrate dephosphorylation dominates in vivo","Membrane recruitment and spatial regulation not addressed","Disease-variant effect on catalysis not tested"]},{"year":2012,"claim":"Identification of the dominant-negative PTPN22.6 splice isoform revealed an additional layer of regulation and a mechanism by which the W620 variant context drives T cell hyperactivation.","evidence":"splice-variant identification and dominant-negative functional assays in human T cells","pmids":["22427951"],"confidence":"Medium","gaps":["Physiological abundance of PTPN22.6 in primary cells unclear","Structural basis of dominant-negative action not resolved"]},{"year":2013,"claim":"Three studies extended PTPN22 beyond TCR inhibition, showing positive control of TLR-driven type I IFN via TRAF3 ubiquitination, in vivo autoimmunity in the R619W knockin, and suppression of M1 macrophage polarization.","evidence":"PTPN22-TRAF3 Co-IP and ubiquitination assays, knockin and KO mouse models with colitis/arthritis and macrophage phenotypes","pmids":["23871208","23619366","23913970"],"confidence":"High","gaps":["Whether TRAF3 ubiquitination is catalytic or scaffolding by PTPN22 unresolved","Cell-type specificity of pro- vs anti-inflammatory roles not unified","Direct substrate driving M1/M2 skewing unidentified"]},{"year":2016,"claim":"A series of studies mapped PTPN22's roles across innate and adaptive compartments — FcgammaR-mediated neutrophil activation, GITR-dependent Treg expansion, ZAP70-context arthritis, and dual CD8 T cell regulation.","evidence":"Ptpn22-/- and knockdown mice with neutrophil functional assays, GITR-blockade rescue, SKG epistasis, and LCMV infection models","pmids":["27807193","26810223","27288531","27725666"],"confidence":"Medium","gaps":["Direct phosphatase substrates in neutrophils, Tregs, and CD8 T cells not biochemically defined","Mechanism of positive IFN-alpha/STAT-1 regulation unresolved","Single-lab phenotypes"]},{"year":2017,"claim":"Work this year placed PTPN22 within innate inflammasome and pattern-recognition pathways, showing autophagy-dependent NLRP3 control, dectin-1/Syk regulation in DCs, and TRAF3-controlled membrane localization.","evidence":"KO macrophages with autophagy manipulation and NLRP3 fractionation, Ptpn22-R619W BMDC dectin-1 assays, TRAF3-deficient T cell membrane fractionation","pmids":["28786745","28948613","28522807"],"confidence":"Medium","gaps":["Whether PTPN22 directly dephosphorylates NLRP3 not established","Kinase/phosphatase coupling to autophagy machinery unclear","Reciprocal validation limited to single labs"]},{"year":2018,"claim":"Studies defined PTPN22's negative control of antigen presentation and adhesion-driven Th1 responses, distinguishing T cell-intrinsic and DC-extrinsic mechanisms.","evidence":"Ptpn22-/- BMDC immune-complex presentation assays, planar bilayer immune synapse imaging, LFA-1 blockade and adoptive transfer","pmids":["30139951","30054208"],"confidence":"Medium","gaps":["Molecular substrates governing synapse and LFA-1 signaling not identified","Relative contribution of intrinsic vs extrinsic effects in disease unquantified"]},{"year":2020,"claim":"Discovery of PKCalpha-driven Ser751 phosphorylation and EB1 as a substrate clarified how PTPN22's stability, membrane recruitment, CSK binding, and microtubule-linked signaling are coordinated.","evidence":"mass spectrometry phosphosite mapping, in vitro PKCalpha kinase and ubiquitination assays, fractionation, CSK Co-IP, yeast two-hybrid and EB1 dephosphorylation","pmids":["32184287","32469452"],"confidence":"High","gaps":["How Ser751 phosphorylation mechanistically blocks membrane recruitment unresolved","Why R620W membrane recruitment is insensitive to Ser751 phosphorylation not explained"]},{"year":2022,"claim":"Three studies added redox regulation via the Cys129–Cys227 disulfide, a platelet PDE5A serine-phosphatase function, and TRAF3-gated PTPN22 recruitment to IFNAR, broadening PTPN22's activity and regulation.","evidence":"C129S knock-in mice with Ncf1 epistasis and thioredoxin assays, platelet KO thrombosis models with PDE5A Co-IP and purified-protein phosphatase assays, IFNAR Co-IP in TRAF3-deficient T cells","pmids":["35587260","35767715","36166512"],"confidence":"High","gaps":["Physiological oxidant source for Cys129 oxidation beyond NOX2 unclear","Structural basis of intrinsic serine-phosphatase activity not defined","Generality of IFNAR recruitment across cell types untested"]},{"year":2023,"claim":"Isogenic CRISPR editing of R620W in primary human T cells established that the risk allele acts as a loss-of-function variant that selectively lowers the activation threshold of low-avidity self-reactive T cells.","evidence":"CRISPR/Cas9 knock-in/knockout in human cord blood T cells with patient-derived IGRP-specific TCRs and functional assays","pmids":["36961507"],"confidence":"High","gaps":["In vivo relevance of low-avidity selectivity to human autoimmunity untested","Mechanism linking avidity threshold to PTPN22 substrate choice not resolved"]},{"year":null,"claim":"It remains unresolved how PTPN22 mechanistically switches between negative regulation of antigen-receptor signaling and positive regulation of TRAF3/type I IFN pathways, and how its tyrosine- versus serine-phosphatase activities are partitioned across cell types.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified structural model integrating membrane recruitment, redox state, and substrate selection","Direct in vivo substrate repertoire in non-T cell lineages undefined","Mechanism of dual tyrosine/serine phosphatase activity not structurally explained"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,10,11]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,10]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,6,9]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[6,9]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,9]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,1,2,18]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,9,11]},{"term_id":"R-HSA-109582","term_label":"Hemostasis","supporting_discovery_ids":[10]}],"complexes":[],"partners":["CSK","TRAF3","EB1","PDE5A","NLRP3","IFNAR"],"other_free_text":[]}},"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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reports","url":"https://pubmed.ncbi.nlm.nih.gov/21706348","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":"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 reports","url":"https://pubmed.ncbi.nlm.nih.gov/21688149","citation_count":16,"is_preprint":false},{"pmid":"27125674","id":"PMC_27125674","title":"CD28 and PTPN22 are associated with susceptibility to rheumatoid arthritis in Egyptians.","date":"2016","source":"Human immunology","url":"https://pubmed.ncbi.nlm.nih.gov/27125674","citation_count":16,"is_preprint":false},{"pmid":"21384170","id":"PMC_21384170","title":"No association of PTPN22 R620W gene polymorphism with rheumatic heart disease and systemic lupus erythematosus.","date":"2011","source":"Molecular biology reports","url":"https://pubmed.ncbi.nlm.nih.gov/21384170","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":"22197427","id":"PMC_22197427","title":"PTPN22 and myasthenia gravis: replication in an Italian population and meta-analysis of literature data.","date":"2011","source":"Neuromuscular disorders : NMD","url":"https://pubmed.ncbi.nlm.nih.gov/22197427","citation_count":15,"is_preprint":false},{"pmid":"19237203","id":"PMC_19237203","title":"PTPN22/LYP 1858C>T gene polymorphism and susceptibility to endometriosis in a Polish population.","date":"2009","source":"Journal of reproductive immunology","url":"https://pubmed.ncbi.nlm.nih.gov/19237203","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},{"pmid":"24985973","id":"PMC_24985973","title":"PTPN22 1858C>T gene polymorphism in patients with SLE: association with serological and clinical results.","date":"2014","source":"Molecular biology reports","url":"https://pubmed.ncbi.nlm.nih.gov/24985973","citation_count":15,"is_preprint":false},{"pmid":"33103521","id":"PMC_33103521","title":"The Relationship between PTPN22 R620W Polymorphisms and the Susceptibility to Autoimmune Thyroid Diseases: An Updated Meta-analysis.","date":"2020","source":"Immunological investigations","url":"https://pubmed.ncbi.nlm.nih.gov/33103521","citation_count":14,"is_preprint":false},{"pmid":"28920273","id":"PMC_28920273","title":"PTPN22 and CTLA-4 gene polymorphisms in resected thymomas and thymus for myasthenia gravis.","date":"2012","source":"Thoracic cancer","url":"https://pubmed.ncbi.nlm.nih.gov/28920273","citation_count":14,"is_preprint":false},{"pmid":"25463433","id":"PMC_25463433","title":"The effect of the autoimmunity-associated gene, PTPN22, on a BXSB-derived model of lupus.","date":"2014","source":"Clinical immunology (Orlando, Fla.)","url":"https://pubmed.ncbi.nlm.nih.gov/25463433","citation_count":14,"is_preprint":false},{"pmid":"27725666","id":"PMC_27725666","title":"Protein tyrosine phosphatase PTPN22 has dual roles in promoting pathogen versus homeostatic-driven CD8 T-cell responses.","date":"2016","source":"Immunology and cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/27725666","citation_count":14,"is_preprint":false},{"pmid":"20522204","id":"PMC_20522204","title":"PTPN22 gene regulates natural killer cell proliferation during in vitro expansion.","date":"2010","source":"Tissue antigens","url":"https://pubmed.ncbi.nlm.nih.gov/20522204","citation_count":13,"is_preprint":false},{"pmid":"25448792","id":"PMC_25448792","title":"PTPN22 R620W polymorphism and ANCA disease risk in white populations: a metaanalysis.","date":"2014","source":"The Journal of rheumatology","url":"https://pubmed.ncbi.nlm.nih.gov/25448792","citation_count":13,"is_preprint":false},{"pmid":"28751955","id":"PMC_28751955","title":"PTPN22 and islet-specific autoimmunity: What have the mouse models taught us?","date":"2017","source":"World journal of diabetes","url":"https://pubmed.ncbi.nlm.nih.gov/28751955","citation_count":12,"is_preprint":false},{"pmid":"33059697","id":"PMC_33059697","title":"rs2476601 in PTPN22 gene in rheumatoid arthritis and periodontitis-a possible interface?","date":"2020","source":"Journal of translational medicine","url":"https://pubmed.ncbi.nlm.nih.gov/33059697","citation_count":12,"is_preprint":false},{"pmid":"28653215","id":"PMC_28653215","title":"NLRP1, PTPN22 and PADI4 gene polymorphisms and rheumatoid arthritis in ACPA-positive Singaporean Chinese.","date":"2017","source":"Rheumatology international","url":"https://pubmed.ncbi.nlm.nih.gov/28653215","citation_count":12,"is_preprint":false},{"pmid":"30384852","id":"PMC_30384852","title":"Novel missense mutation in PTPN22 in a Chinese pedigree with Hashimoto's thyroiditis.","date":"2018","source":"BMC endocrine disorders","url":"https://pubmed.ncbi.nlm.nih.gov/30384852","citation_count":12,"is_preprint":false},{"pmid":"36166512","id":"PMC_36166512","title":"TRAF3 enhances type I interferon receptor signaling in T cells by modulating the phosphatase PTPN22.","date":"2022","source":"Science signaling","url":"https://pubmed.ncbi.nlm.nih.gov/36166512","citation_count":12,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":48848,"output_tokens":6077,"usd":0.118849,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":14668,"output_tokens":4056,"usd":0.08737,"stage2_stop_reason":"end_turn"},"total_usd":0.206219,"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\": 2006,\n      \"finding\": \"PTPN22 (LYP) dephosphorylates Lck at its activating tyrosine Tyr-394 and Zap70 at Tyr-493 (activating residues), but not at regulatory tyrosines Tyr-505 (Lck) or Tyr-319 (Zap70). TCRzeta was also identified as a direct substrate: native PTPN22 dephosphorylated TCRzeta in vitro and in cells, and a substrate-trap mutant (D195A/C227S) co-immunoprecipitated with TCRzeta. Additional novel substrates identified by substrate trapping coupled with mass spectrometry included Vav, CD3epsilon, and valosin-containing protein.\",\n      \"method\": \"Substrate trapping (PTPN22-D195A/C227S mutant) coupled with mass spectrometry in pervanadate-stimulated Jurkat cells; 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 / Strong — in vitro reconstitution with purified proteins, substrate-trap mutagenesis, mass spectrometry identification, and cellular co-IP in a single rigorous study\",\n      \"pmids\": [\"16461343\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PTPN22 selectively promotes TLR-induced type I interferon (IFN) production in myeloid cells by directly associating with TRAF3 and promoting TRAF3 lysine-63-linked ubiquitination. The disease-associated PTPN22-W620 variant failed to promote TRAF3 ubiquitination and type I IFN upregulation.\",\n      \"method\": \"Co-immunoprecipitation (PTPN22–TRAF3 interaction); ubiquitination assays; Ptpn22-deficient mouse models; TLR stimulation of myeloid cells; in vivo colitis and arthritis models\",\n      \"journal\": \"Immunity\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, biochemical ubiquitination assay, genetic KO mouse models with defined phenotypic readouts, multiple orthogonal methods in one study\",\n      \"pmids\": [\"23871208\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The PEP-R619W knockin mouse (ortholog of human LYP-R620W) shows normal protein stability but hyperresponsive lymphocytes upon antigen-receptor engagement, with a distinct profile of tyrosine-phosphorylated substrates. Aged knockin mice develop effector T cell expansion, B cell expansion (transitional, germinal center, age-related), autoantibodies, and systemic autoimmunity. B lineage-restricted variant expression is sufficient to promote autoimmunity.\",\n      \"method\": \"Knockin mouse generation; lymphocyte activation assays; phosphoproteomic profiling; flow cytometry of lymphocyte subsets; autoantibody detection\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — knockin mouse with defined cellular and molecular phenotypes, multiple orthogonal readouts, single rigorous study\",\n      \"pmids\": [\"23619366\"],\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 severe DSS-induced colitis with intestinal macrophages expressing higher M1 and lower M2 genes. An autoinhibition mechanism was identified whereby PTPN22 suppresses its own expression in M1 but not M2 macrophages.\",\n      \"method\": \"PTPN22-deficient mice; DSS colitis model; macrophage polarization assays; gene expression analysis; human macrophage genotype-expression correlation\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mouse with defined cellular phenotype and in vitro macrophage assays, single lab\",\n      \"pmids\": [\"23913970\"],\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; dominant-negative functional assays in human T cells; comparison of full-length vs. splice isoform activity\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional cell-based assays with defined isoform constructs, single lab, multiple cellular readouts\",\n      \"pmids\": [\"22427951\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Loss of PTPN22 results in decreased NLRP3 inflammasome activation via enhanced NLRP3 phosphorylation, and this inhibitory effect is dependent on autophagy: phosphorylated NLRP3 is sequestered into autophagosomes (phagophores), and loss of autophagy abolishes the inhibitory effect on NLRP3 activation observed upon loss of PTPN22.\",\n      \"method\": \"PTPN22 KO macrophages; autophagy inhibition; immunoprecipitation to detect NLRP3 in autophagosomes; NLRP3 phosphorylation assays; IL-1β secretion assays\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO cells with autophagy genetic/pharmacological manipulation, biochemical fractionation, single lab\",\n      \"pmids\": [\"28786745\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TRAF3 associates with PTPN22 and regulates its TCR/CD28-induced localization; loss of TRAF3 results in increased amounts of PTPN22 in T cell membrane fractions and decreased association of PTPN22 with CSK. TRAF3 thus promotes T cell activation partly by preventing membrane localization of PTPN22.\",\n      \"method\": \"Co-immunoprecipitation; membrane fractionation of TRAF3-deficient mouse and human T cells; phosphorylation assays for Lck\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, subcellular fractionation with functional context, single lab\",\n      \"pmids\": [\"28522807\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PTPN22 is a critical regulator of FcγR-mediated neutrophil activation: Ptpn22-/- neutrophils show reduced adhesion, reactive oxygen species production, and degranulation upon stimulation with immobilized immune complexes. Tyrosine phosphorylation of Lyn and Syk was altered in Ptpn22-/- neutrophils. Ptpn22-/- mice were protected from immune complex-mediated arthritis.\",\n      \"method\": \"Ptpn22-/- mice; neutrophil functional assays (ROS, degranulation, adhesion); phosphorylation analysis of Lyn and Syk; in vivo serum transfer arthritis model\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mouse with defined cellular and in vivo phenotypes, multiple orthogonal readouts, single lab\",\n      \"pmids\": [\"27807193\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Ptpn22 knockdown in mice promotes Treg cell expansion by upregulating GITR and increasing GITR signaling, prolonging Treg survival (decreased apoptosis) rather than accelerating cell division. This expansion is dependent on GITR signaling, as GITR-ligand blockade prevented Treg expansion caused by Ptpn22 knockdown. Loss of Ptpn22 also increased the proportion of effector Tregs (CD44hiCD62Llo) at the expense of central Tregs.\",\n      \"method\": \"Ptpn22 siRNA knockdown in mice; GITR expression and signaling analysis; apoptosis assays; GITR-ligand blockade; flow cytometry of Treg subsets\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KD with multiple orthogonal readouts and GITR-blockade rescue experiment, single lab\",\n      \"pmids\": [\"26810223\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PTPN22 is phosphorylated at Ser751 by PKCα in Jurkat and primary human T cells upon activation. This phosphorylation prolongs PTPN22 half-life by inhibiting K48-linked ubiquitination, impairs its recruitment to the plasma membrane (necessary for inhibiting proximal TCR signaling), and enhances its interaction with CSK. The R620W variant retains Ser751 phosphorylation-dependent protection from degradation but its membrane recruitment is unaffected by Ser751 phosphorylation.\",\n      \"method\": \"Mass spectrometry identification of phosphorylation site; PKCα kinase assays; ubiquitination assays; plasma membrane fractionation; co-immunoprecipitation with CSK; phosphomimetic/non-phosphorylatable mutant analysis\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mass spectrometry, in vitro kinase assay, ubiquitination assay, subcellular fractionation, Co-IP, mutagenesis — multiple orthogonal Tier 1 methods in one study\",\n      \"pmids\": [\"32184287\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PTPN22 is expressed in both human and mouse platelets and negatively regulates platelet function and arterial thrombus formation. PTPN22 deficiency accelerates arterial thrombosis and enhances platelet aggregation, granule secretion, calcium mobilization, and clot retraction. Mechanistically, PTPN22 interacts with phosphorylated PDE5A (Ser92) and dephosphorylates it in activated platelets; reduced PDE5A phosphorylation is associated with increased cGMP signaling (vasodilator-stimulated phosphoprotein). Purified PTPN22, but not the catalytic mutant C227S, possesses intrinsic serine phosphatase activity.\",\n      \"method\": \"PTPN22-/- mice; tail-bleeding time; in vivo thrombosis models; quantitative phosphoproteomics; co-immunoprecipitation (PTPN22–PDE5A); in vitro phosphatase assay with purified proteins and C227S mutant; human platelet inhibition experiments\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with purified proteins and catalytic mutant, phosphoproteomics, Co-IP, KO mouse in vivo phenotypes, multiple orthogonal methods\",\n      \"pmids\": [\"35767715\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PTPN22 interacts with EB1 (end-binding protein 1) via the P1 domain of PTPN22, competing with CSK for the same binding domain. The R620W variant does not affect EB1 association. PTPN22 dephosphorylates EB1 at tyrosine-247 (Y247), which decreases expression of T cell activation markers CD25 and CD69 and phosphorylation of ZAP-70, LAT, and Erk, leading to downregulation of NFAT and reduced IL-2 secretion.\",\n      \"method\": \"Yeast two-hybrid; mass spectrometry; co-immunoprecipitation; in vitro dephosphorylation assay; T cell activation assays with overexpression/knockdown constructs\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, yeast two-hybrid, in vitro dephosphorylation, cellular functional assays; single lab\",\n      \"pmids\": [\"32469452\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PTPN22 activity is regulated by oxidation via the non-catalytic Cys129 residue, which forms a disulfide with catalytic Cys227. A C129S knock-in mouse showed stronger T cell-dependent inflammatory responses and autoimmune arthritis due to enhanced TCR signaling. The C129S mutant PTPN22 was more sensitive to oxidation and less amenable to reductive reactivation by the thioredoxin system. The pro-inflammatory effect of the C129S mutation was neutralized by a mutation in Ncf1 (a NOX2 complex component), establishing functional interaction between PTPN22 and Ncf1/NOX2-derived reactive oxygen species.\",\n      \"method\": \"C129S knock-in mouse; T cell activation and arthritis assays; in vitro oxidation/activity assays with purified proteins; genetic epistasis with Ncf1 mutation; thioredoxin reductase reactivation assay\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — knock-in mouse, in vitro biochemical assays with purified proteins, genetic epistasis (Ncf1 double mutant rescue), multiple orthogonal methods in one study\",\n      \"pmids\": [\"35587260\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PTPN22 regulates dectin-1 signaling in dendritic cells by modulating Syk and Erk phosphorylation. Ptpn22-/- BMDCs activated by the dectin-1 agonist curdlan showed enhanced Syk and Erk phosphorylation, increased IL-1β secretion, and enhanced IL-17 T cell responses in an IL-1β-dependent manner. BMDCs expressing the Ptpn22-R619W variant (mouse ortholog of R620W) also showed increased IL-1β and IL-17 responses, indicating that in the dectin-1 context Ptpn22-R619W operates as a loss-of-function variant.\",\n      \"method\": \"Ptpn22-/- and Ptpn22-R619W knock-in BMDC; dectin-1 agonist stimulation; immunoblotting for Syk and Erk phosphorylation; in vitro and in vivo T cell co-culture assays; IL-1β neutralization\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO and knock-in DCs with signaling biochemistry and functional cellular readouts, single lab\",\n      \"pmids\": [\"28948613\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PTPN22 negatively regulates FcγR-mediated antigen presentation in dendritic cells: Ptpn22-/- bone marrow-derived DCs pulsed with ovalbumin:anti-ovalbumin immune complexes have enhanced capability to present immune complex-derived antigens, induce T cell proliferation, and form DC-T cell conjugates.\",\n      \"method\": \"Ptpn22-/- BMDC; immune complex pulsing; DC-T cell co-culture with OT-II T cells; T cell proliferation assays; DC-T cell conjugate formation assays\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO cells with multiple cellular functional readouts, single lab\",\n      \"pmids\": [\"30139951\"],\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 limits LFA-1/ICAM-1-dependent immune synapse formation and DC-T cell conjugate formation; (2) a T cell-extrinsic mechanism whereby PTPN22 in dendritic cells limits LFA-1-dependent Th1 induction by DCs.\",\n      \"method\": \"Ptpn22-/- mice; in vitro anti-CD3/LFA-1 stimulation vs. anti-CD3/anti-CD28 stimulation; planar lipid bilayer immune synapse assays; DC-T cell conjugate assays; adoptive transfer experiments; LFA-1 blockade\",\n      \"journal\": \"Journal of autoimmunity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO cells/mice with multiple in vitro and in vivo functional assays, LFA-1 blockade rescue, single lab\",\n      \"pmids\": [\"30054208\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"TRAF3 enhances type I IFN signaling in CD4+ T cells by preventing recruitment of PTPN22 to the IFNAR complex, thereby enabling activation of JAK1 and STAT1 downstream of IFNAR.\",\n      \"method\": \"Co-immunoprecipitation of PTPN22 with IFNAR complex; TRAF3-deficient T cells; JAK1 and STAT1 phosphorylation assays; CD4+ T cell differentiation assays\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, KO T cells with signaling readouts, single lab\",\n      \"pmids\": [\"36166512\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Loss of PTPN22 in SKG mice (which carry a hypomorphic ZAP70 allele) reduces the severity of mannan-induced autoimmune arthritis. Ptpn22 deficiency biases CD4+ Th cell differentiation away from the pathogenic Th17 lineage toward a Th1/Treg-focused response, without significantly altering thymocyte development or repertoire selection.\",\n      \"method\": \"SKG Ptpn22-/- double-mutant mice; mannan-induced arthritis model; flow cytometry of T cell subsets; Th17/Th1/Treg differentiation assays\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis in double-mutant mice with defined disease and cellular phenotypes, single lab\",\n      \"pmids\": [\"27288531\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CRISPR/Cas9 gene editing of PTPN22-R620W in primary human naive T cells shows that the risk variant (620W) enhances TCR signaling and activation markers following non-specific TCR engagement, phenocopying PTPN22 KO. Using patient-derived TCRs against the autoantigen IGRP, loss of PTPN22 function (KO or 620W) enhanced signaling specifically in T cells expressing a lower-avidity self-reactive TCR (but not high-avidity TCR), promoting enhanced proliferation and Th1 skewing.\",\n      \"method\": \"CRISPR/Cas9 gene editing with donor templates in human cord blood T cells; lentiviral TCR delivery; T cell activation assays; proliferation assays; cytokine profiling\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — isogenic CRISPR-edited primary human T cells with disease-relevant TCRs, multiple orthogonal functional assays, rigorous controls\",\n      \"pmids\": [\"36961507\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PTPN22 has dual roles in CD8+ T cell responses: it promotes antigen-driven CD8 T cell expansion during acute LCMV infection by positively regulating IFN-α/STAT-1 signaling in T cells (Ptpn22-/- CD8 T cells show reduced STAT-1 upregulation and reduced STAT-1 phosphorylation in response to IFN-α); conversely, it inhibits homeostatic-driven proliferation (Ptpn22-/- CD8 T cells show increased expansion in lymphopenic hosts).\",\n      \"method\": \"LCMV infection of Ptpn22-/- mice; adoptive transfer into lymphopenic hosts; STAT-1 phosphorylation assays in response to IFN-α; flow cytometry of CD8 T cell subsets\",\n      \"journal\": \"Immunology and cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mouse with in vivo infection model, biochemical signaling assays, adoptive transfer; single lab\",\n      \"pmids\": [\"27725666\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PTPN22 (LYP/PEP) is a hematopoietic-specific non-receptor protein tyrosine phosphatase that inhibits T cell receptor signaling by dephosphorylating activating residues on Lck (Tyr-394), ZAP70 (Tyr-493), TCRzeta, and EB1 (Tyr-247); its activity at the plasma membrane is regulated by PKCα-mediated Ser751 phosphorylation (which promotes CSK binding and inhibits membrane recruitment) and by redox regulation through a non-catalytic Cys129–Cys227 disulfide; beyond T cells, PTPN22 promotes TLR-driven type I IFN production in myeloid cells by facilitating TRAF3 K63-ubiquitination, regulates NLRP3 inflammasome activity via autophagy-dependent NLRP3 phosphorylation and sequestration, modulates FcγR signaling in neutrophils and dendritic cells, suppresses M1 macrophage polarization, expands regulatory T cells via GITR upregulation, and dephosphorylates PDE5A in platelets to limit arterial thrombosis; the disease-associated R620W variant disrupts CSK binding, impairs membrane-localized phosphatase activity, fails to promote TRAF3 ubiquitination and type I IFN responses, and enhances low-avidity self-reactive T cell signaling, collectively lowering the threshold for autoimmunity.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PTPN22 (LYP/PEP) is a hematopoietic non-receptor protein tyrosine phosphatase that raises the activation threshold of immune cells by dephosphorylating activating tyrosines in antigen-receptor and Fc-receptor signaling cascades [#0, #18]. In T cells it directly dephosphorylates the activating sites on Lck (Tyr-394) and ZAP70 (Tyr-493) while sparing their inhibitory tyrosines, and it acts on TCRzeta, Vav, and CD3epsilon, thereby attenuating proximal TCR signaling [#0]. It also targets the microtubule end-binding protein EB1 at Tyr-247 through its P1 domain, dampening downstream ZAP-70/LAT/Erk activation, NFAT, and IL-2 output [#11]. Its inhibitory action depends on recruitment to the plasma membrane and on association with CSK; PKCalpha-mediated Ser751 phosphorylation stabilizes PTPN22 against K48-ubiquitin-driven degradation while impairing membrane recruitment and enhancing CSK binding, and TRAF3 likewise restrains membrane localization to permit T cell activation [#9, #6]. PTPN22 catalytic activity is redox-controlled through a non-catalytic Cys129–catalytic Cys227 disulfide that, when disrupted, sensitizes the enzyme to NOX2/Ncf1-derived oxidation and heightens TCR-driven autoimmunity [#12]. Beyond T cells, PTPN22 governs innate immune responses: it promotes TLR-induced type I interferon by facilitating K63-linked TRAF3 ubiquitination, restrains NLRP3 inflammasome activation by promoting autophagy-dependent sequestration of phosphorylated NLRP3, suppresses M1 macrophage polarization, and negatively regulates FcgammaR- and dectin-1-driven neutrophil and dendritic-cell effector functions [#1, #5, #3, #7, #13, #14]. It also expands regulatory T cells via GITR signaling and, outside immunity, dephosphorylates PDE5A in platelets to limit arterial thrombosis [#8, #10]. The autoimmunity-associated R620W (mouse R619W) variant disrupts CSK binding and membrane-localized phosphatase function, fails to promote TRAF3 ubiquitination and type I IFN responses, and selectively lowers the signaling threshold of low-avidity self-reactive T cells, establishing it as a loss-of-function risk allele for autoimmunity [#1, #2, #18].\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Establishing PTPN22's direct substrates answered how it suppresses TCR signaling at the molecular level, showing selective removal of activating rather than inhibitory phosphotyrosines.\",\n      \"evidence\": \"substrate-trap mutagenesis with mass spectrometry, in vitro dephosphorylation of purified proteins, and co-IP in Jurkat/293T cells\",\n      \"pmids\": [\"16461343\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define which substrate dephosphorylation dominates in vivo\", \"Membrane recruitment and spatial regulation not addressed\", \"Disease-variant effect on catalysis not tested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identification of the dominant-negative PTPN22.6 splice isoform revealed an additional layer of regulation and a mechanism by which the W620 variant context drives T cell hyperactivation.\",\n      \"evidence\": \"splice-variant identification and dominant-negative functional assays in human T cells\",\n      \"pmids\": [\"22427951\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological abundance of PTPN22.6 in primary cells unclear\", \"Structural basis of dominant-negative action not resolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Three studies extended PTPN22 beyond TCR inhibition, showing positive control of TLR-driven type I IFN via TRAF3 ubiquitination, in vivo autoimmunity in the R619W knockin, and suppression of M1 macrophage polarization.\",\n      \"evidence\": \"PTPN22-TRAF3 Co-IP and ubiquitination assays, knockin and KO mouse models with colitis/arthritis and macrophage phenotypes\",\n      \"pmids\": [\"23871208\", \"23619366\", \"23913970\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether TRAF3 ubiquitination is catalytic or scaffolding by PTPN22 unresolved\", \"Cell-type specificity of pro- vs anti-inflammatory roles not unified\", \"Direct substrate driving M1/M2 skewing unidentified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"A series of studies mapped PTPN22's roles across innate and adaptive compartments — FcgammaR-mediated neutrophil activation, GITR-dependent Treg expansion, ZAP70-context arthritis, and dual CD8 T cell regulation.\",\n      \"evidence\": \"Ptpn22-/- and knockdown mice with neutrophil functional assays, GITR-blockade rescue, SKG epistasis, and LCMV infection models\",\n      \"pmids\": [\"27807193\", \"26810223\", \"27288531\", \"27725666\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct phosphatase substrates in neutrophils, Tregs, and CD8 T cells not biochemically defined\", \"Mechanism of positive IFN-alpha/STAT-1 regulation unresolved\", \"Single-lab phenotypes\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Work this year placed PTPN22 within innate inflammasome and pattern-recognition pathways, showing autophagy-dependent NLRP3 control, dectin-1/Syk regulation in DCs, and TRAF3-controlled membrane localization.\",\n      \"evidence\": \"KO macrophages with autophagy manipulation and NLRP3 fractionation, Ptpn22-R619W BMDC dectin-1 assays, TRAF3-deficient T cell membrane fractionation\",\n      \"pmids\": [\"28786745\", \"28948613\", \"28522807\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether PTPN22 directly dephosphorylates NLRP3 not established\", \"Kinase/phosphatase coupling to autophagy machinery unclear\", \"Reciprocal validation limited to single labs\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Studies defined PTPN22's negative control of antigen presentation and adhesion-driven Th1 responses, distinguishing T cell-intrinsic and DC-extrinsic mechanisms.\",\n      \"evidence\": \"Ptpn22-/- BMDC immune-complex presentation assays, planar bilayer immune synapse imaging, LFA-1 blockade and adoptive transfer\",\n      \"pmids\": [\"30139951\", \"30054208\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular substrates governing synapse and LFA-1 signaling not identified\", \"Relative contribution of intrinsic vs extrinsic effects in disease unquantified\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Discovery of PKCalpha-driven Ser751 phosphorylation and EB1 as a substrate clarified how PTPN22's stability, membrane recruitment, CSK binding, and microtubule-linked signaling are coordinated.\",\n      \"evidence\": \"mass spectrometry phosphosite mapping, in vitro PKCalpha kinase and ubiquitination assays, fractionation, CSK Co-IP, yeast two-hybrid and EB1 dephosphorylation\",\n      \"pmids\": [\"32184287\", \"32469452\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How Ser751 phosphorylation mechanistically blocks membrane recruitment unresolved\", \"Why R620W membrane recruitment is insensitive to Ser751 phosphorylation not explained\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Three studies added redox regulation via the Cys129–Cys227 disulfide, a platelet PDE5A serine-phosphatase function, and TRAF3-gated PTPN22 recruitment to IFNAR, broadening PTPN22's activity and regulation.\",\n      \"evidence\": \"C129S knock-in mice with Ncf1 epistasis and thioredoxin assays, platelet KO thrombosis models with PDE5A Co-IP and purified-protein phosphatase assays, IFNAR Co-IP in TRAF3-deficient T cells\",\n      \"pmids\": [\"35587260\", \"35767715\", \"36166512\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological oxidant source for Cys129 oxidation beyond NOX2 unclear\", \"Structural basis of intrinsic serine-phosphatase activity not defined\", \"Generality of IFNAR recruitment across cell types untested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Isogenic CRISPR editing of R620W in primary human T cells established that the risk allele acts as a loss-of-function variant that selectively lowers the activation threshold of low-avidity self-reactive T cells.\",\n      \"evidence\": \"CRISPR/Cas9 knock-in/knockout in human cord blood T cells with patient-derived IGRP-specific TCRs and functional assays\",\n      \"pmids\": [\"36961507\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance of low-avidity selectivity to human autoimmunity untested\", \"Mechanism linking avidity threshold to PTPN22 substrate choice not resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how PTPN22 mechanistically switches between negative regulation of antigen-receptor signaling and positive regulation of TRAF3/type I IFN pathways, and how its tyrosine- versus serine-phosphatase activities are partitioned across cell types.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified structural model integrating membrane recruitment, redox state, and substrate selection\", \"Direct in vivo substrate repertoire in non-T cell lineages undefined\", \"Mechanism of dual tyrosine/serine phosphatase activity not structurally explained\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 10, 11]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 10]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 6, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [6, 9]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 9]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 1, 2, 18]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 9, 11]},\n      {\"term_id\": \"R-HSA-109582\", \"supporting_discovery_ids\": [10]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"CSK\", \"TRAF3\", \"EB1\", \"PDE5A\", \"NLRP3\", \"IFNAR\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}