{"gene":"PIR","run_date":"2026-04-28T19:45:44","timeline":{"discoveries":[{"year":1998,"finding":"PIR-B (paired immunoglobulin-like receptor B) inhibitory signaling requires SHP-1 and SHP-2 phosphatases; mutational analysis identified tyrosine 771 (in VxYxxL motif) as the most critical residue for inhibitory signaling, and PIR-B-mediated inhibition was markedly reduced in SHP-1/SHP-2 double-deficient DT40 B cells but unaffected in SHIP-deficient cells.","method":"Mutational analysis of cytoplasmic tyrosines, genetic double-KO DT40 B cells, B cell activation assays","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 1-2 — mutagenesis + genetic KO with defined functional readout, replicated across labs","pmids":["9547347"],"is_preprint":false},{"year":1998,"finding":"PIR-B ITIMs, upon tyrosine phosphorylation, recruit SHP-1 protein tyrosine phosphatase (but not SHIP), initiating a SHP-1-dependent inhibitory pathway that negatively regulates B lymphocyte activation.","method":"Co-immunoprecipitation, ITIM phosphorylation assays, in vitro binding studies","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, replicated in multiple labs","pmids":["9482905"],"is_preprint":false},{"year":1999,"finding":"PIR-B coligation with BCR inhibits BCR-induced tyrosine phosphorylation of Igα/Igβ, Syk, Btk, and PLCγ2; SHP-1 recruited to PIR-B dephosphorylates and inactivates Syk and Btk, which reduces PLCγ2 phosphorylation; Lyn kinase mediates ITIM phosphorylation of PIR-B.","method":"Overexpression of catalytically inactive SHP-1 dominant negative, co-IP, kinase assays, calcium flux","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1-2 — dominant-negative rescue + multiple biochemical endpoints, consistent with companion papers","pmids":["10327049"],"is_preprint":false},{"year":1999,"finding":"PIR-A associates with the Fc receptor common gamma (FcRγ) chain via a charged Arg residue in its transmembrane region; this association is required for cell surface expression of PIR-A and enables ITAM-dependent activating signaling (calcium mobilization, mast cell activation).","method":"Co-transfection, cell surface flow cytometry, FcRγ knockout mice, calcium mobilization assay","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 — genetic KO mice + cotransfection + functional readout, replicated across labs","pmids":["9892613","9730901"],"is_preprint":false},{"year":1998,"finding":"PIR-A transmembrane domain associates with FcRγ chain via Arg residue; PIR-A cross-linking activates mast cells (calcium mobilization) through ITAM-dependent signaling, while PIR-B delivers inhibitory signals through ITIMs in its cytoplasmic domain suppressing degranulation and Ca2+ mobilization; mutation of 3rd and 4th ITIM tyrosines attenuates PIR-B inhibitory effects.","method":"Chimeric receptor expression in RBL-2H3 cells, degranulation assay, cytoplasmic Ca2+ measurement, tyrosine-to-phenylalanine mutagenesis","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis + functional reconstitution in cell line model","pmids":["9780174"],"is_preprint":false},{"year":1999,"finding":"PIR-B is constitutively tyrosine phosphorylated on macrophages and B lymphocytes and constitutively associated with SHP-1 and Lyn; Lyn kinase is required for PIR-B tyrosine phosphorylation; phosphorylation status is significantly reduced in MHC class I-deficient mice, suggesting MHC class I as an endogenous PIR-B ligand.","method":"Co-immunoprecipitation, Lyn-KO mice, MHC-I KO mice, phosphorylation Western blot","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — multiple genetic KO models + co-IP, strong mechanistic evidence","pmids":["10611342"],"is_preprint":false},{"year":1999,"finding":"PIR-A3 physically interacts with FcεRIγ chain through Arg632 in its transmembrane domain in macrophages; this interaction enables PIR-A to deliver activation signals (nitric oxide production synergized with IFN-γ).","method":"Chimeric receptor cotransfection in 293T cells, co-immunoprecipitation, Arg632 mutagenesis, nitric oxide assay","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1-2 — transmembrane residue mutagenesis + co-IP + functional assay","pmids":["10477705"],"is_preprint":false},{"year":2001,"finding":"PIR-B is preferentially expressed on the mast cell surface where it is constitutively tyrosine phosphorylated and associated with SHP-1; PIR-B coligation with FcεRI inhibits IgE-mediated mast cell activation and serotonin release; a third ITIM was identified that mediates inhibition independent of SHP-1, SHP-2, and SHIP.","method":"Co-IP, phosphorylation assays, SHP-1-deficient mast cells, serotonin release assay, RBL cell transfection with PIR-B cytoplasmic mutants","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — genetic KO + mutagenesis + functional assay","pmids":["11581305"],"is_preprint":false},{"year":2002,"finding":"PIR-B deficiency in mice (PIR-B−/−) leads to impaired dendritic cell maturation, constitutively activated B2 cells, augmented TH2-prone humoral responses (increased IL-4, IgG1, IgE), and increased peritoneal B1 cells, establishing PIR-B as critical for B cell suppression, DC maturation, and TH1/TH2 balance.","method":"PIR-B knockout mouse model, B cell activation/proliferation assays, cytokine ELISA, immunization with T-dependent antigens","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 — clean KO with multiple defined cellular phenotypes","pmids":["12021780"],"is_preprint":false},{"year":2002,"finding":"HLA-G interacts with murine PIR-B (a homologue of human ILT4), and this interaction modifies dendritic cell function and prolongs allogeneic graft survival.","method":"In vivo graft transplantation model, PIR-B interaction studies with HLA-G","journal":"European journal of immunology","confidence":"Medium","confidence_rationale":"Tier 3 — single study, functional in vivo evidence but limited direct binding characterization","pmids":["12207326"],"is_preprint":false},{"year":2004,"finding":"Src family kinases Hck and Fgr negatively regulate neutrophil and dendritic cell chemokine signaling by maintaining tonic phosphorylation of PIR-B; in hck−/−fgr−/− cells PIR-B is unphosphorylated and cells are hyperresponsive to chemokines; PIR-B−/− neutrophils and DCs show similarly elevated chemokine responses.","method":"Src-family kinase double-KO mice, PIR-B KO mice, Ca2+ flux, MAP kinase activation, actin polymerization, chemotaxis assays","journal":"Immunity","confidence":"High","confidence_rationale":"Tier 2 — parallel genetic KO models with multiple functional readouts establishing epistasis","pmids":["15723811"],"is_preprint":false},{"year":2004,"finding":"PIR-B negatively regulates neutrophil and macrophage integrin signaling; PIR-B−/− neutrophils show enhanced respiratory burst, granule release, and hyperadhesion on ECM/adhesion molecules; PIR-B−/− macrophages show enhanced phosphorylation of integrin signaling proteins and increased spreading.","method":"PIR-B knockout mice, respiratory burst assay, granule release assay, adhesion assay, integrin signaling biochemistry","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — KO model with multiple orthogonal functional readouts and biochemical validation","pmids":["15494528"],"is_preprint":false},{"year":2005,"finding":"PIR-B binds MHC class I molecules; PIR-B and CD8αα compete for binding to MHC class I on DCs; PIR-B on DCs blocks CD8 molecule access to MHC-I, thereby reducing CTL triggering; PIR-B-deficient DCs evoke CTLs more efficiently leading to accelerated graft and tumor rejection.","method":"Surface plasmon resonance, PIR-B-KO DCs, CTL priming assays, transfectant competition assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 — SPR binding kinetics + KO functional assay, multiple orthogonal methods","pmids":["18787130"],"is_preprint":false},{"year":2008,"finding":"PIR-B and human LILRB inhibitory receptors are expressed on osteoclast precursor cells, constitutively recruit SHP-1 in the presence of RANKL and M-CSF, and suppress osteoclast development in vitro; FRET analysis indicates constitutive binding of PIR-B (and human LILRB1) to MHC class I molecules on the same cell surface (cis) as a regulatory mechanism.","method":"Flow cytometry, co-immunoprecipitation, FRET, in vitro osteoclast differentiation assay, PIR-B KO","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — FRET structural evidence + Co-IP + functional differentiation assay","pmids":["18802077"],"is_preprint":false},{"year":2009,"finding":"PIR-B on B-1 cells suppresses TLR9 signaling by dephosphorylating Bruton's tyrosine kinase (Btk), attenuating NF-κB p65RelA activation but not p38 or Erk, and blocking natural IgM autoantibody production including rheumatoid factor.","method":"PIR-B KO mice, Fasˡᵖʳ double-mutant, TLR9 stimulation, Btk phosphorylation assays, NF-κB activation assay","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with double mutant + multiple biochemical readouts","pmids":["19687229"],"is_preprint":false},{"year":2010,"finding":"PIR-B negatively regulates macrophage MAPK and NF-κB activation in response to bacterial stimulation; PIR-B−/− mice are more susceptible to DSS-induced colitis; adoptive transfer of PIR-B−/− macrophages into WT mice is sufficient to increase disease susceptibility.","method":"PIR-B KO mice, DSS colitis model, macrophage adoptive transfer, cytokine ELISA, MAPK/NF-κB Western blot","journal":"Gastroenterology","confidence":"High","confidence_rationale":"Tier 2 — KO + adoptive transfer rescue experiment + biochemical pathway analysis","pmids":["20398663"],"is_preprint":false},{"year":2011,"finding":"PIR-B mediates axon growth inhibition by myelin-derived inhibitors (MAG, Nogo, OMgp); MAG binding to PIR-B leads to PIR-B association with Trk neurotrophin receptors, recruiting SHP-1 and SHP-2 which act as Trk tyrosine phosphatases, reducing basal and neurotrophin-stimulated Trk activity; siRNA knockdown of SHP-1 or SHP-2 in vivo promotes axonal regeneration after optic nerve injury.","method":"Co-immunoprecipitation, in vitro phosphatase assays, siRNA knockdown in vivo, optic nerve crush model","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1-2 — Co-IP + enzymatic assay + in vivo siRNA with functional readout","pmids":["21364532"],"is_preprint":false},{"year":2011,"finding":"p75 neurotrophin receptor interacts with PIR-B upon ligand binding and is required for PIR-B-mediated SHP activation and axon growth inhibition; p75 mutant mice show promotion of axonal regeneration after optic nerve injury.","method":"Co-immunoprecipitation, p75 gene mutant mice, optic nerve crush model, SHP activation assay","journal":"Cell death & disease","confidence":"High","confidence_rationale":"Tier 2 — Co-IP + genetic KO with defined in vivo phenotype","pmids":["21881600"],"is_preprint":false},{"year":2011,"finding":"PIR-B binds Nogo with higher affinity than MHC class I; MHCI binding is restricted to N-terminal PIR-B ectodomains, whereas Nogo binds either N- or C-terminal ectodomains; Nogo and MHCI binding to PIR-B is competitive; endogenous Nogo intensifies PIR-B-mediated suppression of IL-6 release from mast cells.","method":"Surface plasmon resonance (kinetic analysis), recombinant PIR-B ectodomain fragments, PIR-B KO mast cells, IL-6 assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstituted SPR with defined binding domains + KO functional validation","pmids":["21636572"],"is_preprint":false},{"year":2014,"finding":"Basal transcription of the human PIR (Pirin) gene is driven by NRF2 via a highly conserved antioxidant response element (ARE) located 281 bp downstream of the transcription start site; NRF2 was shown to bind this element in vivo.","method":"Luciferase reporter assay with PIR promoter constructs, ChIP (NRF2 binding), chromatin immunoprecipitation","journal":"Molecular and cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — reporter assay + ChIP, single lab study","pmids":["24390086"],"is_preprint":false},{"year":2019,"finding":"Pirin (PIR) protein activates E2F1 transcription by directly binding to the E2F1 promoter region; PIR knockdown downregulates E2F1 and its target genes (CDK4, CDK6, cyclin E, cyclin D, DDR1) causing G1/S arrest and reduced proliferation; PIR knockdown also reduces cell migration and invasion in breast cancer cells.","method":"Luciferase reporter assay, ChIP, PIR knockdown (siRNA/shRNA), xenograft mouse model, cell cycle analysis","journal":"Cell cycle","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP + reporter assay + KO phenotype, single lab","pmids":["31500513"],"is_preprint":false},{"year":2020,"finding":"HPV16 E7 oncoprotein promotes Pirin (PIR) upregulation through the EGFR/PI3K/AKT1/NRF2 signaling pathway, resulting in PIR/NF-κB activation in oral cancer cells.","method":"Pathway inhibitor experiments, Western blot, reporter assays for NF-κB activity","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 3 — pathway inhibition + reporter assay, single lab, limited mechanistic depth for PIR specifically","pmids":["32679705"],"is_preprint":false},{"year":2024,"finding":"The PIR domain of IRS-1 (phosphorylation insulin resistance domain, C-terminal to the PTB domain) containing Ser307, Ser312, Ser315, and Ser323 interacts with the N-terminal lobe and hinge region of the IR kinase domain; this interaction strengthens IRS-1 binding to IR and may protect IR from PTP1B-mediated dephosphorylation; phosphorylation of these serines abrogates IRS-1/IR interaction and reduces downstream AKT signaling.","method":"Surface plasmon resonance, hydrogen-deuterium exchange mass spectrometry, phosphomimetic mutagenesis, cell-based insulin signaling assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 — SPR + HDX-MS structural mapping + mutagenesis + cell signaling readout in single study","pmids":["38625937"],"is_preprint":false},{"year":2000,"finding":"Grb7 binds activated, tyrosine-phosphorylated insulin receptor through two domains: the SH2 domain and the PIR (phosphotyrosine interacting region) domain; the PIR domain binds the activated tyrosine kinase loop of the insulin receptor; Grb7 is not a substrate of the insulin receptor kinase.","method":"Two-hybrid, GST pull-down, co-immunoprecipitation, domain mapping","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 — multiple binding assays (two-hybrid + pulldown + Co-IP) in single study","pmids":["10803466"],"is_preprint":false},{"year":2003,"finding":"The PIR domain of Grb14 is an intrinsically unstructured/disordered protein by NMR; despite lacking secondary structure, isolated PIR and PIR-SH2 domains inhibit insulin-induced meiosis reinitiation in Xenopus oocytes, demonstrating functional activity in the absence of folded structure.","method":"NMR spectroscopy (15N-labeled PIR), Xenopus oocyte functional assay","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 — NMR structural characterization + functional assay, orthogonal methods","pmids":["14623073"],"is_preprint":false},{"year":2004,"finding":"The PIR domain of Grb14 is natively unfolded in solution (confirmed by SAXS and CD); a short stretch (residues 399-407) may be transiently structured and could mediate binding to the insulin receptor kinase.","method":"Small-angle X-ray scattering (SAXS), circular dichroism, computational ensemble modeling","journal":"Biophysical journal","confidence":"Medium","confidence_rationale":"Tier 1 — SAXS + CD structural characterization, single study","pmids":["15465854"],"is_preprint":false},{"year":2020,"finding":"C. elegans PIR-1 (ortholog of mammalian PIR-1/DUSP11 RNA phosphatase family) dephosphorylates 5'-triphosphorylated RNAs produced by cellular RNA-dependent RNA polymerases and is required for maturation of Dicer-dependent 26G-RNAs during spermatogenesis and embryogenesis; PIR-1 also regulates the CSR-1 22G-RNA pathway.","method":"Genetic KO/depletion, small RNA sequencing, biochemical dephosphorylation assays","journal":"Molecular cell","confidence":"Medium","confidence_rationale":"Tier 2 — genetic loss-of-function + biochemical assay, C. elegans ortholog","pmids":["33378643"],"is_preprint":false}],"current_model":"PIR-B (the murine paired immunoglobulin-like inhibitory receptor) functions as an ITIM-bearing cell-surface receptor that, upon constitutive or ligand-induced tyrosine phosphorylation by Lyn kinase, recruits SHP-1 and SHP-2 phosphatases to dephosphorylate and inactivate BCR/FcεRI/TLR9/integrin signaling components (including Syk, Btk, and Trk), negatively regulating B cell, mast cell, DC, macrophage, and neutrophil activation; its activating counterpart PIR-A signals through an ITAM-bearing FcRγ chain associated via a transmembrane arginine; in neurons, PIR-B binds myelin inhibitors (MAG/Nogo/OMgp) and associates with Trk receptors, suppressing axon regeneration via SHP-1/2-mediated Trk dephosphorylation; in the IRS-1/insulin receptor context, the PIR (phosphorylation insulin resistance) domain of IRS-1 directly engages the IR kinase domain and serine phosphorylation within it abrogates this interaction to cause insulin resistance."},"narrative":{"teleology":[{"year":1998,"claim":"Establishing the core inhibitory mechanism of PIR-B: the discovery that PIR-B ITIM tyrosines (especially Y771) recruit SHP-1/SHP-2 to suppress B cell activation resolved how this receptor transduces inhibitory signals, distinguishing it from SHIP-dependent pathways.","evidence":"Tyrosine mutagenesis in PIR-B cytoplasmic domain and SHP-1/SHP-2 double-KO DT40 B cells with functional activation readouts","pmids":["9547347","9482905"],"confidence":"High","gaps":["Crystal structure of PIR-B ITIM–SHP-1 complex not determined","Relative contribution of individual ITIMs beyond Y771 not fully resolved"]},{"year":1998,"claim":"Defining the activating counterpart: PIR-A was shown to associate with FcRγ chain via a transmembrane Arg residue, enabling ITAM-dependent calcium mobilization and mast cell activation, establishing the paired receptor paradigm.","evidence":"Chimeric receptor cotransfection in RBL-2H3 and 293T cells, FcRγ KO mice, degranulation and calcium flux assays, Arg mutagenesis","pmids":["9780174","9892613","9730901","10477705"],"confidence":"High","gaps":["Ligand specificity distinguishing PIR-A from PIR-B engagement not clarified","Stoichiometry of PIR-A/FcRγ complex unknown"]},{"year":1999,"claim":"Identifying the upstream kinase and downstream substrates: Lyn kinase was shown to phosphorylate PIR-B ITIMs, and SHP-1 recruited to PIR-B was shown to dephosphorylate Syk and Btk, explaining how PIR-B intercepts proximal BCR signaling.","evidence":"Dominant-negative SHP-1, co-IP, Lyn-KO mice, kinase/phosphorylation assays","pmids":["10327049","10611342"],"confidence":"High","gaps":["Whether PIR-B directly dephosphorylates Igα/Igβ or acts only through Syk/Btk not resolved"]},{"year":1999,"claim":"Identifying MHC class I as an endogenous PIR-B ligand: reduced PIR-B phosphorylation in MHC-I-deficient mice established that MHC-I molecules provide tonic signals maintaining constitutive PIR-B activation.","evidence":"MHC-I KO mice, phosphorylation Western blot, co-IP","pmids":["10611342"],"confidence":"High","gaps":["Precise MHC-I allele specificity for PIR-B binding not mapped","Whether soluble vs membrane-bound MHC-I differentially regulate PIR-B unknown"]},{"year":2001,"claim":"Extending PIR-B inhibition to mast cells and revealing SHP-independent ITIM function: PIR-B coligation with FcεRI inhibited IgE-mediated mast cell degranulation, and a third ITIM was found to function independently of SHP-1, SHP-2, and SHIP.","evidence":"PIR-B cytoplasmic mutant transfection in RBL cells, SHP-1-deficient mast cells, serotonin release assay","pmids":["11581305"],"confidence":"High","gaps":["Effector recruited by the third ITIM not identified","Relevance of SHP-independent pathway in vivo not tested"]},{"year":2002,"claim":"Establishing in vivo physiological consequences: PIR-B KO mice displayed constitutively activated B2 cells, impaired DC maturation, augmented TH2 responses, and increased B1 cells, demonstrating PIR-B as a critical immune checkpoint.","evidence":"PIR-B knockout mice, B cell activation assays, cytokine ELISA, T-dependent antigen immunization","pmids":["12021780"],"confidence":"High","gaps":["Mechanism of DC maturation impairment not fully delineated at the signaling level","Role of PIR-B in human immune regulation via LILRB orthologs not directly tested"]},{"year":2004,"claim":"Broadening PIR-B's inhibitory reach to innate immunity: PIR-B was shown to suppress neutrophil and macrophage integrin signaling and chemokine responses, with Src kinases Hck/Fgr maintaining tonic PIR-B phosphorylation.","evidence":"Hck/Fgr double-KO and PIR-B KO mice, respiratory burst, chemotaxis, Ca2+ flux, MAPK activation assays","pmids":["15723811","15494528"],"confidence":"High","gaps":["Direct substrate(s) of SHP-1 downstream of PIR-B in integrin signaling not identified","Contribution of individual Src kinases not separated"]},{"year":2008,"claim":"Demonstrating cis-interaction with MHC-I and extending to osteoclastogenesis: FRET analysis showed constitutive cis-binding of PIR-B to MHC-I on the same cell, and PIR-B suppressed osteoclast differentiation, linking immune receptor biology to bone homeostasis.","evidence":"FRET, co-IP, in vitro osteoclast differentiation assay, SPR for MHC-I binding, PIR-B KO","pmids":["18802077","18787130"],"confidence":"High","gaps":["How cis-MHC-I engagement is regulated during activation not determined","In vivo bone phenotype of PIR-B KO not characterized"]},{"year":2009,"claim":"Connecting PIR-B to TLR9 signaling and autoimmunity: PIR-B on B-1 cells suppressed TLR9-driven Btk phosphorylation and NF-κB activation, preventing natural IgM autoantibody (including rheumatoid factor) production.","evidence":"PIR-B KO × Faslpr double-mutant mice, TLR9 stimulation, Btk/NF-κB biochemistry","pmids":["19687229"],"confidence":"High","gaps":["Whether PIR-B modulates other TLR pathways beyond TLR9 not systematically tested"]},{"year":2010,"claim":"Demonstrating PIR-B's role in intestinal immune homeostasis: PIR-B KO mice showed increased susceptibility to DSS colitis, and adoptive transfer of PIR-B-deficient macrophages was sufficient to transfer susceptibility, pinpointing macrophage PIR-B as a disease-relevant checkpoint.","evidence":"PIR-B KO mice, DSS colitis model, macrophage adoptive transfer, MAPK/NF-κB Western blot","pmids":["20398663"],"confidence":"High","gaps":["Specific ligand driving PIR-B activation in gut mucosa not identified"]},{"year":2011,"claim":"Revealing a neuronal function: PIR-B was shown to bind myelin inhibitors (MAG, Nogo, OMgp), associate with Trk receptors via p75NTR, and recruit SHP-1/SHP-2 to dephosphorylate Trk, suppressing axon regeneration; in vivo SHP knockdown promoted regeneration after optic nerve crush.","evidence":"Co-IP, in vitro phosphatase assays, SPR for Nogo/MHC-I binding kinetics, p75 mutant mice, in vivo siRNA, optic nerve crush model","pmids":["21364532","21881600","21636572"],"confidence":"High","gaps":["Whether PIR-B operates through identical ITIM/SHP mechanism in neurons as in immune cells not fully confirmed","Nogo receptor complex hierarchy (NgR1 vs PIR-B) in regeneration not resolved"]},{"year":2014,"claim":"Identifying NRF2 as the transcriptional driver of human Pirin (PIR): NRF2 was found to bind a conserved ARE downstream of the PIR transcription start site, establishing how Pirin expression is regulated under oxidative stress conditions.","evidence":"Luciferase reporter assays with PIR promoter constructs, ChIP for NRF2 binding","pmids":["24390086"],"confidence":"Medium","gaps":["Whether other transcription factors co-regulate PIR expression not explored","Functional consequence of NRF2-driven PIR upregulation on cell phenotype not directly tested in this study"]},{"year":2019,"claim":"Establishing Pirin as a transcriptional activator of E2F1: Pirin directly binds the E2F1 promoter and its knockdown causes G1/S arrest and reduced proliferation, linking Pirin to cell cycle control in breast cancer.","evidence":"ChIP, luciferase reporter, siRNA/shRNA knockdown, xenograft model, cell cycle analysis","pmids":["31500513"],"confidence":"Medium","gaps":["Molecular mechanism by which Pirin activates E2F1 transcription (cofactor interactions, chromatin remodeling) not defined","Generalizability beyond breast cancer cell lines not tested"]},{"year":2000,"claim":"Characterizing the PIR domain of Grb7/Grb14 adaptor proteins: the PIR domain was shown to bind the activated insulin receptor kinase loop independently of the SH2 domain, and NMR/SAXS revealed it is intrinsically disordered yet functionally active in inhibiting insulin signaling.","evidence":"Two-hybrid, GST pull-down, co-IP, NMR (15N-labeled PIR), SAXS, CD, Xenopus oocyte functional assay","pmids":["10803466","14623073","15465854"],"confidence":"High","gaps":["Atomic-resolution structure of PIR domain bound to IR kinase not available","In vivo significance of Grb7/14 PIR domain in insulin resistance not directly shown"]},{"year":2024,"claim":"Mapping the IRS-1 PIR domain interaction with the insulin receptor: the PIR domain containing Ser307/312/315/323 contacts the N-terminal lobe and hinge of the IR kinase, strengthening IRS-1 binding; serine phosphorylation of these residues disrupts the interaction and reduces AKT signaling, providing a structural basis for insulin resistance.","evidence":"SPR, hydrogen-deuterium exchange MS, phosphomimetic mutagenesis, cell-based insulin signaling assays","pmids":["38625937"],"confidence":"High","gaps":["Which kinase(s) phosphorylate the PIR domain serines in vivo during insulin resistance not identified in this study","Whether the IRS-1 PIR domain mechanism is conserved across species not tested"]},{"year":null,"claim":"Major open questions include: the identity of the SHP-independent effector recruited by the third PIR-B ITIM; whether the distinct PIR-B functions in immune cells versus neurons use identical downstream signaling cascades; and the precise mechanism by which Pirin activates transcription at the E2F1 promoter.","evidence":"","pmids":[],"confidence":"Low","gaps":["Third ITIM effector unidentified","No unified signaling model across immune and neuronal PIR-B contexts","Pirin's transcriptional cofactors unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,2,7,14,16]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[3,4,6]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[20]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,3,4,5,7,12,13]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[20]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,1,2,5,8,10,11,14,15]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[3,4,6,16,22]}],"complexes":["PIR-B/SHP-1 complex","PIR-A/FcRγ complex","PIR-B/Trk/p75NTR complex"],"partners":["SHP-1","SHP-2","LYN","FCERG1","BTK","NGFR","NTRK1","E2F1"],"other_free_text":[]},"mechanistic_narrative":"PIR encompasses multiple distinct molecular entities studied under the same gene symbol: (1) PIR-B, a murine ITIM-bearing inhibitory receptor that, upon constitutive Lyn/Hck/Fgr-mediated tyrosine phosphorylation, recruits SHP-1 and SHP-2 phosphatases to negatively regulate BCR, FcεRI, TLR9, integrin, and chemokine signaling in B cells, mast cells, macrophages, neutrophils, dendritic cells, and osteoclast precursors, with its activating counterpart PIR-A signaling through FcRγ chain ITAM-dependent pathways [PMID:9547347, PMID:9780174, PMID:12021780, PMID:15723811]; (2) Pirin, a nuclear protein whose transcription is driven by NRF2 via an antioxidant response element and which activates E2F1 transcription by directly binding the E2F1 promoter, promoting cell cycle progression [PMID:24390086, PMID:31500513]; and (3) the PIR (phosphorylation insulin resistance) domain found in IRS-1 and Grb7/Grb14 adapter proteins, an intrinsically disordered region that engages the insulin receptor kinase domain and whose serine phosphorylation disrupts this interaction to attenuate insulin signaling [PMID:38625937, PMID:14623073]. In neurons, PIR-B binds myelin inhibitors (MAG, Nogo, OMgp) and associates with Trk receptors via p75NTR, recruiting SHP-1/SHP-2 to dephosphorylate Trk and suppress axon regeneration [PMID:21364532, PMID:21881600]."},"prefetch_data":{"uniprot":{"accession":"O00625","full_name":"Pirin","aliases":["Probable quercetin 2,3-dioxygenase PIR","Probable quercetinase"],"length_aa":290,"mass_kda":32.1,"function":"Transcriptional coregulator of NF-kappa-B which facilitates binding of NF-kappa-B proteins to target kappa-B genes in a redox-state-dependent manner. May be required for efficient terminal myeloid maturation of hematopoietic cells. 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mitophagy by binding to PINK1 in colorectal cancer.","date":"2022","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/35581181","citation_count":27,"is_preprint":false},{"pmid":"9550322","id":"PMC_9550322","title":"Genomic structure of PIR-B, the inhibitory member of the paired immunoglobulin-like receptor genes in mice.","date":"1998","source":"Tissue antigens","url":"https://pubmed.ncbi.nlm.nih.gov/9550322","citation_count":27,"is_preprint":false},{"pmid":"10477705","id":"PMC_10477705","title":"Functional association of FcepsilonRIgamma with arginine(632) of paired immunoglobulin-like receptor (PIR)-A3 in murine macrophages.","date":"1999","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/10477705","citation_count":27,"is_preprint":false},{"pmid":"10869023","id":"PMC_10869023","title":"PIR: a new resource for bioinformatics.","date":"2000","source":"Bioinformatics (Oxford, England)","url":"https://pubmed.ncbi.nlm.nih.gov/10869023","citation_count":26,"is_preprint":false},{"pmid":"38625937","id":"PMC_38625937","title":"The serine phosphorylations in the IRS-1 PIR domain abrogate IRS-1 and IR interaction.","date":"2024","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/38625937","citation_count":24,"is_preprint":false},{"pmid":"21360733","id":"PMC_21360733","title":"Isolation of Pichia pastoris PIR genes and their utilization for cell surface display and recombinant protein secretion.","date":"2010","source":"Yeast (Chichester, England)","url":"https://pubmed.ncbi.nlm.nih.gov/21360733","citation_count":24,"is_preprint":false},{"pmid":"36249068","id":"PMC_36249068","title":"Serum-derived piR-hsa-164586 of extracellular vesicles as a novel biomarker for early diagnosis of non-small cell lung cancer.","date":"2022","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/36249068","citation_count":23,"is_preprint":false},{"pmid":"14623073","id":"PMC_14623073","title":"The PIR domain of Grb14 is an intrinsically unstructured protein: implication in insulin signaling.","date":"2003","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/14623073","citation_count":22,"is_preprint":false},{"pmid":"22433797","id":"PMC_22433797","title":"A simple method for construction of pir+ Enterobacterial hosts for maintenance of R6K replicon plasmids.","date":"2012","source":"BMC research notes","url":"https://pubmed.ncbi.nlm.nih.gov/22433797","citation_count":22,"is_preprint":false},{"pmid":"12673625","id":"PMC_12673625","title":"Characterization of a disulphide-bound Pir-cell wall protein (Pir-CWP) of Yarrowia lipolytica.","date":"2003","source":"Yeast (Chichester, England)","url":"https://pubmed.ncbi.nlm.nih.gov/12673625","citation_count":22,"is_preprint":false},{"pmid":"31500513","id":"PMC_31500513","title":"PIR promotes tumorigenesis of breast cancer by upregulating cell cycle activator E2F1.","date":"2019","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/31500513","citation_count":20,"is_preprint":false},{"pmid":"39102033","id":"PMC_39102033","title":"piR-823 tale as emerging cancer-hallmark molecular marker in different cancer types: a step-toward ncRNA-precision.","date":"2024","source":"Naunyn-Schmiedeberg's archives of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/39102033","citation_count":20,"is_preprint":false},{"pmid":"34249688","id":"PMC_34249688","title":"piR-hsa-211106 Inhibits the Progression of Lung Adenocarcinoma Through Pyruvate Carboxylase and Enhances Chemotherapy Sensitivity.","date":"2021","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/34249688","citation_count":19,"is_preprint":false},{"pmid":"38572963","id":"PMC_38572963","title":"Small Extracellular Vesicle piR-hsa-30937 Derived from Pancreatic Neuroendocrine Neoplasms Upregulates CD276 in Macrophages to Promote Immune Evasion.","date":"2024","source":"Cancer immunology research","url":"https://pubmed.ncbi.nlm.nih.gov/38572963","citation_count":19,"is_preprint":false},{"pmid":"33378643","id":"PMC_33378643","title":"The RNA phosphatase PIR-1 regulates endogenous small RNA pathways in C. elegans.","date":"2020","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/33378643","citation_count":18,"is_preprint":false},{"pmid":"24493571","id":"PMC_24493571","title":"The contribution of Pir protein family to yeast cell surface display.","date":"2014","source":"Applied microbiology and biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/24493571","citation_count":18,"is_preprint":false},{"pmid":"32881713","id":"PMC_32881713","title":"piR-19166 inhibits migration and metastasis through CTTN/MMPs pathway in prostate carcinoma.","date":"2020","source":"Aging","url":"https://pubmed.ncbi.nlm.nih.gov/32881713","citation_count":18,"is_preprint":false},{"pmid":"37473805","id":"PMC_37473805","title":"FDFT1 repression by piR-39980 prevents oncogenesis by regulating proliferation and apoptosis through hypoxia in tongue squamous cell carcinoma.","date":"2023","source":"Life sciences","url":"https://pubmed.ncbi.nlm.nih.gov/37473805","citation_count":18,"is_preprint":false},{"pmid":"31286407","id":"PMC_31286407","title":"Nogo-A/Pir-B/TrkB Signaling Pathway Activation Inhibits Neuronal Survival and Axonal Regeneration After Experimental Intracerebral Hemorrhage in Rats.","date":"2019","source":"Journal of molecular neuroscience : MN","url":"https://pubmed.ncbi.nlm.nih.gov/31286407","citation_count":18,"is_preprint":false},{"pmid":"30576786","id":"PMC_30576786","title":"Multiplex SYBR Green and duplex TaqMan real-time PCR assays for the detection of Photorhabdus Insect-Related (Pir) toxin genes pirA and pirB.","date":"2018","source":"Molecular and cellular probes","url":"https://pubmed.ncbi.nlm.nih.gov/30576786","citation_count":18,"is_preprint":false},{"pmid":"29040791","id":"PMC_29040791","title":"From the Cover: Roles of mmu_piR_003399 in Microcystin-Leucine Arginine-Induced Reproductive Toxicity in the Spermatogonial Cells and Testis.","date":"2018","source":"Toxicological sciences : an official journal of the Society of Toxicology","url":"https://pubmed.ncbi.nlm.nih.gov/29040791","citation_count":18,"is_preprint":false},{"pmid":"24145365","id":"PMC_24145365","title":"Nevirapine-raltegravir combination, an NRTI and PI/r sparing regimen, as maintenance antiretroviral therapy in virologically suppressed HIV-1-infected patients.","date":"2013","source":"Antiviral therapy","url":"https://pubmed.ncbi.nlm.nih.gov/24145365","citation_count":18,"is_preprint":false},{"pmid":"32428871","id":"PMC_32428871","title":"PIWI-interacting RNAs piR-13643 and piR-21238 are promising diagnostic biomarkers of papillary thyroid carcinoma.","date":"2020","source":"Aging","url":"https://pubmed.ncbi.nlm.nih.gov/32428871","citation_count":17,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":45965,"output_tokens":6203,"usd":0.11547},"stage2":{"model":"claude-opus-4-6","input_tokens":9952,"output_tokens":4035,"usd":0.225953},"total_usd":0.341423,"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\": 1998,\n      \"finding\": \"PIR-B (paired immunoglobulin-like receptor B) inhibitory signaling requires SHP-1 and SHP-2 phosphatases; mutational analysis identified tyrosine 771 (in VxYxxL motif) as the most critical residue for inhibitory signaling, and PIR-B-mediated inhibition was markedly reduced in SHP-1/SHP-2 double-deficient DT40 B cells but unaffected in SHIP-deficient cells.\",\n      \"method\": \"Mutational analysis of cytoplasmic tyrosines, genetic double-KO DT40 B cells, B cell activation assays\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — mutagenesis + genetic KO with defined functional readout, replicated across labs\",\n      \"pmids\": [\"9547347\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"PIR-B ITIMs, upon tyrosine phosphorylation, recruit SHP-1 protein tyrosine phosphatase (but not SHIP), initiating a SHP-1-dependent inhibitory pathway that negatively regulates B lymphocyte activation.\",\n      \"method\": \"Co-immunoprecipitation, ITIM phosphorylation assays, in vitro binding studies\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, replicated in multiple labs\",\n      \"pmids\": [\"9482905\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"PIR-B coligation with BCR inhibits BCR-induced tyrosine phosphorylation of Igα/Igβ, Syk, Btk, and PLCγ2; SHP-1 recruited to PIR-B dephosphorylates and inactivates Syk and Btk, which reduces PLCγ2 phosphorylation; Lyn kinase mediates ITIM phosphorylation of PIR-B.\",\n      \"method\": \"Overexpression of catalytically inactive SHP-1 dominant negative, co-IP, kinase assays, calcium flux\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — dominant-negative rescue + multiple biochemical endpoints, consistent with companion papers\",\n      \"pmids\": [\"10327049\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"PIR-A associates with the Fc receptor common gamma (FcRγ) chain via a charged Arg residue in its transmembrane region; this association is required for cell surface expression of PIR-A and enables ITAM-dependent activating signaling (calcium mobilization, mast cell activation).\",\n      \"method\": \"Co-transfection, cell surface flow cytometry, FcRγ knockout mice, calcium mobilization assay\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO mice + cotransfection + functional readout, replicated across labs\",\n      \"pmids\": [\"9892613\", \"9730901\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"PIR-A transmembrane domain associates with FcRγ chain via Arg residue; PIR-A cross-linking activates mast cells (calcium mobilization) through ITAM-dependent signaling, while PIR-B delivers inhibitory signals through ITIMs in its cytoplasmic domain suppressing degranulation and Ca2+ mobilization; mutation of 3rd and 4th ITIM tyrosines attenuates PIR-B inhibitory effects.\",\n      \"method\": \"Chimeric receptor expression in RBL-2H3 cells, degranulation assay, cytoplasmic Ca2+ measurement, tyrosine-to-phenylalanine mutagenesis\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis + functional reconstitution in cell line model\",\n      \"pmids\": [\"9780174\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"PIR-B is constitutively tyrosine phosphorylated on macrophages and B lymphocytes and constitutively associated with SHP-1 and Lyn; Lyn kinase is required for PIR-B tyrosine phosphorylation; phosphorylation status is significantly reduced in MHC class I-deficient mice, suggesting MHC class I as an endogenous PIR-B ligand.\",\n      \"method\": \"Co-immunoprecipitation, Lyn-KO mice, MHC-I KO mice, phosphorylation Western blot\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple genetic KO models + co-IP, strong mechanistic evidence\",\n      \"pmids\": [\"10611342\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"PIR-A3 physically interacts with FcεRIγ chain through Arg632 in its transmembrane domain in macrophages; this interaction enables PIR-A to deliver activation signals (nitric oxide production synergized with IFN-γ).\",\n      \"method\": \"Chimeric receptor cotransfection in 293T cells, co-immunoprecipitation, Arg632 mutagenesis, nitric oxide assay\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — transmembrane residue mutagenesis + co-IP + functional assay\",\n      \"pmids\": [\"10477705\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"PIR-B is preferentially expressed on the mast cell surface where it is constitutively tyrosine phosphorylated and associated with SHP-1; PIR-B coligation with FcεRI inhibits IgE-mediated mast cell activation and serotonin release; a third ITIM was identified that mediates inhibition independent of SHP-1, SHP-2, and SHIP.\",\n      \"method\": \"Co-IP, phosphorylation assays, SHP-1-deficient mast cells, serotonin release assay, RBL cell transfection with PIR-B cytoplasmic mutants\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO + mutagenesis + functional assay\",\n      \"pmids\": [\"11581305\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PIR-B deficiency in mice (PIR-B−/−) leads to impaired dendritic cell maturation, constitutively activated B2 cells, augmented TH2-prone humoral responses (increased IL-4, IgG1, IgE), and increased peritoneal B1 cells, establishing PIR-B as critical for B cell suppression, DC maturation, and TH1/TH2 balance.\",\n      \"method\": \"PIR-B knockout mouse model, B cell activation/proliferation assays, cytokine ELISA, immunization with T-dependent antigens\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with multiple defined cellular phenotypes\",\n      \"pmids\": [\"12021780\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"HLA-G interacts with murine PIR-B (a homologue of human ILT4), and this interaction modifies dendritic cell function and prolongs allogeneic graft survival.\",\n      \"method\": \"In vivo graft transplantation model, PIR-B interaction studies with HLA-G\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single study, functional in vivo evidence but limited direct binding characterization\",\n      \"pmids\": [\"12207326\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Src family kinases Hck and Fgr negatively regulate neutrophil and dendritic cell chemokine signaling by maintaining tonic phosphorylation of PIR-B; in hck−/−fgr−/− cells PIR-B is unphosphorylated and cells are hyperresponsive to chemokines; PIR-B−/− neutrophils and DCs show similarly elevated chemokine responses.\",\n      \"method\": \"Src-family kinase double-KO mice, PIR-B KO mice, Ca2+ flux, MAP kinase activation, actin polymerization, chemotaxis assays\",\n      \"journal\": \"Immunity\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — parallel genetic KO models with multiple functional readouts establishing epistasis\",\n      \"pmids\": [\"15723811\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"PIR-B negatively regulates neutrophil and macrophage integrin signaling; PIR-B−/− neutrophils show enhanced respiratory burst, granule release, and hyperadhesion on ECM/adhesion molecules; PIR-B−/− macrophages show enhanced phosphorylation of integrin signaling proteins and increased spreading.\",\n      \"method\": \"PIR-B knockout mice, respiratory burst assay, granule release assay, adhesion assay, integrin signaling biochemistry\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO model with multiple orthogonal functional readouts and biochemical validation\",\n      \"pmids\": [\"15494528\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"PIR-B binds MHC class I molecules; PIR-B and CD8αα compete for binding to MHC class I on DCs; PIR-B on DCs blocks CD8 molecule access to MHC-I, thereby reducing CTL triggering; PIR-B-deficient DCs evoke CTLs more efficiently leading to accelerated graft and tumor rejection.\",\n      \"method\": \"Surface plasmon resonance, PIR-B-KO DCs, CTL priming assays, transfectant competition assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — SPR binding kinetics + KO functional assay, multiple orthogonal methods\",\n      \"pmids\": [\"18787130\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PIR-B and human LILRB inhibitory receptors are expressed on osteoclast precursor cells, constitutively recruit SHP-1 in the presence of RANKL and M-CSF, and suppress osteoclast development in vitro; FRET analysis indicates constitutive binding of PIR-B (and human LILRB1) to MHC class I molecules on the same cell surface (cis) as a regulatory mechanism.\",\n      \"method\": \"Flow cytometry, co-immunoprecipitation, FRET, in vitro osteoclast differentiation assay, PIR-B KO\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — FRET structural evidence + Co-IP + functional differentiation assay\",\n      \"pmids\": [\"18802077\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PIR-B on B-1 cells suppresses TLR9 signaling by dephosphorylating Bruton's tyrosine kinase (Btk), attenuating NF-κB p65RelA activation but not p38 or Erk, and blocking natural IgM autoantibody production including rheumatoid factor.\",\n      \"method\": \"PIR-B KO mice, Fasˡᵖʳ double-mutant, TLR9 stimulation, Btk phosphorylation assays, NF-κB activation assay\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with double mutant + multiple biochemical readouts\",\n      \"pmids\": [\"19687229\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PIR-B negatively regulates macrophage MAPK and NF-κB activation in response to bacterial stimulation; PIR-B−/− mice are more susceptible to DSS-induced colitis; adoptive transfer of PIR-B−/− macrophages into WT mice is sufficient to increase disease susceptibility.\",\n      \"method\": \"PIR-B KO mice, DSS colitis model, macrophage adoptive transfer, cytokine ELISA, MAPK/NF-κB Western blot\",\n      \"journal\": \"Gastroenterology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO + adoptive transfer rescue experiment + biochemical pathway analysis\",\n      \"pmids\": [\"20398663\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PIR-B mediates axon growth inhibition by myelin-derived inhibitors (MAG, Nogo, OMgp); MAG binding to PIR-B leads to PIR-B association with Trk neurotrophin receptors, recruiting SHP-1 and SHP-2 which act as Trk tyrosine phosphatases, reducing basal and neurotrophin-stimulated Trk activity; siRNA knockdown of SHP-1 or SHP-2 in vivo promotes axonal regeneration after optic nerve injury.\",\n      \"method\": \"Co-immunoprecipitation, in vitro phosphatase assays, siRNA knockdown in vivo, optic nerve crush model\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — Co-IP + enzymatic assay + in vivo siRNA with functional readout\",\n      \"pmids\": [\"21364532\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"p75 neurotrophin receptor interacts with PIR-B upon ligand binding and is required for PIR-B-mediated SHP activation and axon growth inhibition; p75 mutant mice show promotion of axonal regeneration after optic nerve injury.\",\n      \"method\": \"Co-immunoprecipitation, p75 gene mutant mice, optic nerve crush model, SHP activation assay\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP + genetic KO with defined in vivo phenotype\",\n      \"pmids\": [\"21881600\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PIR-B binds Nogo with higher affinity than MHC class I; MHCI binding is restricted to N-terminal PIR-B ectodomains, whereas Nogo binds either N- or C-terminal ectodomains; Nogo and MHCI binding to PIR-B is competitive; endogenous Nogo intensifies PIR-B-mediated suppression of IL-6 release from mast cells.\",\n      \"method\": \"Surface plasmon resonance (kinetic analysis), recombinant PIR-B ectodomain fragments, PIR-B KO mast cells, IL-6 assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted SPR with defined binding domains + KO functional validation\",\n      \"pmids\": [\"21636572\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Basal transcription of the human PIR (Pirin) gene is driven by NRF2 via a highly conserved antioxidant response element (ARE) located 281 bp downstream of the transcription start site; NRF2 was shown to bind this element in vivo.\",\n      \"method\": \"Luciferase reporter assay with PIR promoter constructs, ChIP (NRF2 binding), chromatin immunoprecipitation\",\n      \"journal\": \"Molecular and cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reporter assay + ChIP, single lab study\",\n      \"pmids\": [\"24390086\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Pirin (PIR) protein activates E2F1 transcription by directly binding to the E2F1 promoter region; PIR knockdown downregulates E2F1 and its target genes (CDK4, CDK6, cyclin E, cyclin D, DDR1) causing G1/S arrest and reduced proliferation; PIR knockdown also reduces cell migration and invasion in breast cancer cells.\",\n      \"method\": \"Luciferase reporter assay, ChIP, PIR knockdown (siRNA/shRNA), xenograft mouse model, cell cycle analysis\",\n      \"journal\": \"Cell cycle\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP + reporter assay + KO phenotype, single lab\",\n      \"pmids\": [\"31500513\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"HPV16 E7 oncoprotein promotes Pirin (PIR) upregulation through the EGFR/PI3K/AKT1/NRF2 signaling pathway, resulting in PIR/NF-κB activation in oral cancer cells.\",\n      \"method\": \"Pathway inhibitor experiments, Western blot, reporter assays for NF-κB activity\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — pathway inhibition + reporter assay, single lab, limited mechanistic depth for PIR specifically\",\n      \"pmids\": [\"32679705\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The PIR domain of IRS-1 (phosphorylation insulin resistance domain, C-terminal to the PTB domain) containing Ser307, Ser312, Ser315, and Ser323 interacts with the N-terminal lobe and hinge region of the IR kinase domain; this interaction strengthens IRS-1 binding to IR and may protect IR from PTP1B-mediated dephosphorylation; phosphorylation of these serines abrogates IRS-1/IR interaction and reduces downstream AKT signaling.\",\n      \"method\": \"Surface plasmon resonance, hydrogen-deuterium exchange mass spectrometry, phosphomimetic mutagenesis, cell-based insulin signaling assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — SPR + HDX-MS structural mapping + mutagenesis + cell signaling readout in single study\",\n      \"pmids\": [\"38625937\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Grb7 binds activated, tyrosine-phosphorylated insulin receptor through two domains: the SH2 domain and the PIR (phosphotyrosine interacting region) domain; the PIR domain binds the activated tyrosine kinase loop of the insulin receptor; Grb7 is not a substrate of the insulin receptor kinase.\",\n      \"method\": \"Two-hybrid, GST pull-down, co-immunoprecipitation, domain mapping\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple binding assays (two-hybrid + pulldown + Co-IP) in single study\",\n      \"pmids\": [\"10803466\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The PIR domain of Grb14 is an intrinsically unstructured/disordered protein by NMR; despite lacking secondary structure, isolated PIR and PIR-SH2 domains inhibit insulin-induced meiosis reinitiation in Xenopus oocytes, demonstrating functional activity in the absence of folded structure.\",\n      \"method\": \"NMR spectroscopy (15N-labeled PIR), Xenopus oocyte functional assay\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — NMR structural characterization + functional assay, orthogonal methods\",\n      \"pmids\": [\"14623073\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The PIR domain of Grb14 is natively unfolded in solution (confirmed by SAXS and CD); a short stretch (residues 399-407) may be transiently structured and could mediate binding to the insulin receptor kinase.\",\n      \"method\": \"Small-angle X-ray scattering (SAXS), circular dichroism, computational ensemble modeling\",\n      \"journal\": \"Biophysical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — SAXS + CD structural characterization, single study\",\n      \"pmids\": [\"15465854\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"C. elegans PIR-1 (ortholog of mammalian PIR-1/DUSP11 RNA phosphatase family) dephosphorylates 5'-triphosphorylated RNAs produced by cellular RNA-dependent RNA polymerases and is required for maturation of Dicer-dependent 26G-RNAs during spermatogenesis and embryogenesis; PIR-1 also regulates the CSR-1 22G-RNA pathway.\",\n      \"method\": \"Genetic KO/depletion, small RNA sequencing, biochemical dephosphorylation assays\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic loss-of-function + biochemical assay, C. elegans ortholog\",\n      \"pmids\": [\"33378643\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PIR-B (the murine paired immunoglobulin-like inhibitory receptor) functions as an ITIM-bearing cell-surface receptor that, upon constitutive or ligand-induced tyrosine phosphorylation by Lyn kinase, recruits SHP-1 and SHP-2 phosphatases to dephosphorylate and inactivate BCR/FcεRI/TLR9/integrin signaling components (including Syk, Btk, and Trk), negatively regulating B cell, mast cell, DC, macrophage, and neutrophil activation; its activating counterpart PIR-A signals through an ITAM-bearing FcRγ chain associated via a transmembrane arginine; in neurons, PIR-B binds myelin inhibitors (MAG/Nogo/OMgp) and associates with Trk receptors, suppressing axon regeneration via SHP-1/2-mediated Trk dephosphorylation; in the IRS-1/insulin receptor context, the PIR (phosphorylation insulin resistance) domain of IRS-1 directly engages the IR kinase domain and serine phosphorylation within it abrogates this interaction to cause insulin resistance.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PIR encompasses multiple distinct molecular entities studied under the same gene symbol: (1) PIR-B, a murine ITIM-bearing inhibitory receptor that, upon constitutive Lyn/Hck/Fgr-mediated tyrosine phosphorylation, recruits SHP-1 and SHP-2 phosphatases to negatively regulate BCR, FcεRI, TLR9, integrin, and chemokine signaling in B cells, mast cells, macrophages, neutrophils, dendritic cells, and osteoclast precursors, with its activating counterpart PIR-A signaling through FcRγ chain ITAM-dependent pathways [PMID:9547347, PMID:9780174, PMID:12021780, PMID:15723811]; (2) Pirin, a nuclear protein whose transcription is driven by NRF2 via an antioxidant response element and which activates E2F1 transcription by directly binding the E2F1 promoter, promoting cell cycle progression [PMID:24390086, PMID:31500513]; and (3) the PIR (phosphorylation insulin resistance) domain found in IRS-1 and Grb7/Grb14 adapter proteins, an intrinsically disordered region that engages the insulin receptor kinase domain and whose serine phosphorylation disrupts this interaction to attenuate insulin signaling [PMID:38625937, PMID:14623073]. In neurons, PIR-B binds myelin inhibitors (MAG, Nogo, OMgp) and associates with Trk receptors via p75NTR, recruiting SHP-1/SHP-2 to dephosphorylate Trk and suppress axon regeneration [PMID:21364532, PMID:21881600].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Establishing the core inhibitory mechanism of PIR-B: the discovery that PIR-B ITIM tyrosines (especially Y771) recruit SHP-1/SHP-2 to suppress B cell activation resolved how this receptor transduces inhibitory signals, distinguishing it from SHIP-dependent pathways.\",\n      \"evidence\": \"Tyrosine mutagenesis in PIR-B cytoplasmic domain and SHP-1/SHP-2 double-KO DT40 B cells with functional activation readouts\",\n      \"pmids\": [\"9547347\", \"9482905\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Crystal structure of PIR-B ITIM–SHP-1 complex not determined\", \"Relative contribution of individual ITIMs beyond Y771 not fully resolved\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Defining the activating counterpart: PIR-A was shown to associate with FcRγ chain via a transmembrane Arg residue, enabling ITAM-dependent calcium mobilization and mast cell activation, establishing the paired receptor paradigm.\",\n      \"evidence\": \"Chimeric receptor cotransfection in RBL-2H3 and 293T cells, FcRγ KO mice, degranulation and calcium flux assays, Arg mutagenesis\",\n      \"pmids\": [\"9780174\", \"9892613\", \"9730901\", \"10477705\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Ligand specificity distinguishing PIR-A from PIR-B engagement not clarified\", \"Stoichiometry of PIR-A/FcRγ complex unknown\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Identifying the upstream kinase and downstream substrates: Lyn kinase was shown to phosphorylate PIR-B ITIMs, and SHP-1 recruited to PIR-B was shown to dephosphorylate Syk and Btk, explaining how PIR-B intercepts proximal BCR signaling.\",\n      \"evidence\": \"Dominant-negative SHP-1, co-IP, Lyn-KO mice, kinase/phosphorylation assays\",\n      \"pmids\": [\"10327049\", \"10611342\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PIR-B directly dephosphorylates Igα/Igβ or acts only through Syk/Btk not resolved\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Identifying MHC class I as an endogenous PIR-B ligand: reduced PIR-B phosphorylation in MHC-I-deficient mice established that MHC-I molecules provide tonic signals maintaining constitutive PIR-B activation.\",\n      \"evidence\": \"MHC-I KO mice, phosphorylation Western blot, co-IP\",\n      \"pmids\": [\"10611342\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise MHC-I allele specificity for PIR-B binding not mapped\", \"Whether soluble vs membrane-bound MHC-I differentially regulate PIR-B unknown\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Extending PIR-B inhibition to mast cells and revealing SHP-independent ITIM function: PIR-B coligation with FcεRI inhibited IgE-mediated mast cell degranulation, and a third ITIM was found to function independently of SHP-1, SHP-2, and SHIP.\",\n      \"evidence\": \"PIR-B cytoplasmic mutant transfection in RBL cells, SHP-1-deficient mast cells, serotonin release assay\",\n      \"pmids\": [\"11581305\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Effector recruited by the third ITIM not identified\", \"Relevance of SHP-independent pathway in vivo not tested\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Establishing in vivo physiological consequences: PIR-B KO mice displayed constitutively activated B2 cells, impaired DC maturation, augmented TH2 responses, and increased B1 cells, demonstrating PIR-B as a critical immune checkpoint.\",\n      \"evidence\": \"PIR-B knockout mice, B cell activation assays, cytokine ELISA, T-dependent antigen immunization\",\n      \"pmids\": [\"12021780\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of DC maturation impairment not fully delineated at the signaling level\", \"Role of PIR-B in human immune regulation via LILRB orthologs not directly tested\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Broadening PIR-B's inhibitory reach to innate immunity: PIR-B was shown to suppress neutrophil and macrophage integrin signaling and chemokine responses, with Src kinases Hck/Fgr maintaining tonic PIR-B phosphorylation.\",\n      \"evidence\": \"Hck/Fgr double-KO and PIR-B KO mice, respiratory burst, chemotaxis, Ca2+ flux, MAPK activation assays\",\n      \"pmids\": [\"15723811\", \"15494528\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct substrate(s) of SHP-1 downstream of PIR-B in integrin signaling not identified\", \"Contribution of individual Src kinases not separated\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Demonstrating cis-interaction with MHC-I and extending to osteoclastogenesis: FRET analysis showed constitutive cis-binding of PIR-B to MHC-I on the same cell, and PIR-B suppressed osteoclast differentiation, linking immune receptor biology to bone homeostasis.\",\n      \"evidence\": \"FRET, co-IP, in vitro osteoclast differentiation assay, SPR for MHC-I binding, PIR-B KO\",\n      \"pmids\": [\"18802077\", \"18787130\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How cis-MHC-I engagement is regulated during activation not determined\", \"In vivo bone phenotype of PIR-B KO not characterized\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Connecting PIR-B to TLR9 signaling and autoimmunity: PIR-B on B-1 cells suppressed TLR9-driven Btk phosphorylation and NF-κB activation, preventing natural IgM autoantibody (including rheumatoid factor) production.\",\n      \"evidence\": \"PIR-B KO × Faslpr double-mutant mice, TLR9 stimulation, Btk/NF-κB biochemistry\",\n      \"pmids\": [\"19687229\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PIR-B modulates other TLR pathways beyond TLR9 not systematically tested\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Demonstrating PIR-B's role in intestinal immune homeostasis: PIR-B KO mice showed increased susceptibility to DSS colitis, and adoptive transfer of PIR-B-deficient macrophages was sufficient to transfer susceptibility, pinpointing macrophage PIR-B as a disease-relevant checkpoint.\",\n      \"evidence\": \"PIR-B KO mice, DSS colitis model, macrophage adoptive transfer, MAPK/NF-κB Western blot\",\n      \"pmids\": [\"20398663\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific ligand driving PIR-B activation in gut mucosa not identified\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Revealing a neuronal function: PIR-B was shown to bind myelin inhibitors (MAG, Nogo, OMgp), associate with Trk receptors via p75NTR, and recruit SHP-1/SHP-2 to dephosphorylate Trk, suppressing axon regeneration; in vivo SHP knockdown promoted regeneration after optic nerve crush.\",\n      \"evidence\": \"Co-IP, in vitro phosphatase assays, SPR for Nogo/MHC-I binding kinetics, p75 mutant mice, in vivo siRNA, optic nerve crush model\",\n      \"pmids\": [\"21364532\", \"21881600\", \"21636572\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PIR-B operates through identical ITIM/SHP mechanism in neurons as in immune cells not fully confirmed\", \"Nogo receptor complex hierarchy (NgR1 vs PIR-B) in regeneration not resolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identifying NRF2 as the transcriptional driver of human Pirin (PIR): NRF2 was found to bind a conserved ARE downstream of the PIR transcription start site, establishing how Pirin expression is regulated under oxidative stress conditions.\",\n      \"evidence\": \"Luciferase reporter assays with PIR promoter constructs, ChIP for NRF2 binding\",\n      \"pmids\": [\"24390086\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether other transcription factors co-regulate PIR expression not explored\", \"Functional consequence of NRF2-driven PIR upregulation on cell phenotype not directly tested in this study\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Establishing Pirin as a transcriptional activator of E2F1: Pirin directly binds the E2F1 promoter and its knockdown causes G1/S arrest and reduced proliferation, linking Pirin to cell cycle control in breast cancer.\",\n      \"evidence\": \"ChIP, luciferase reporter, siRNA/shRNA knockdown, xenograft model, cell cycle analysis\",\n      \"pmids\": [\"31500513\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism by which Pirin activates E2F1 transcription (cofactor interactions, chromatin remodeling) not defined\", \"Generalizability beyond breast cancer cell lines not tested\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Characterizing the PIR domain of Grb7/Grb14 adaptor proteins: the PIR domain was shown to bind the activated insulin receptor kinase loop independently of the SH2 domain, and NMR/SAXS revealed it is intrinsically disordered yet functionally active in inhibiting insulin signaling.\",\n      \"evidence\": \"Two-hybrid, GST pull-down, co-IP, NMR (15N-labeled PIR), SAXS, CD, Xenopus oocyte functional assay\",\n      \"pmids\": [\"10803466\", \"14623073\", \"15465854\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic-resolution structure of PIR domain bound to IR kinase not available\", \"In vivo significance of Grb7/14 PIR domain in insulin resistance not directly shown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Mapping the IRS-1 PIR domain interaction with the insulin receptor: the PIR domain containing Ser307/312/315/323 contacts the N-terminal lobe and hinge of the IR kinase, strengthening IRS-1 binding; serine phosphorylation of these residues disrupts the interaction and reduces AKT signaling, providing a structural basis for insulin resistance.\",\n      \"evidence\": \"SPR, hydrogen-deuterium exchange MS, phosphomimetic mutagenesis, cell-based insulin signaling assays\",\n      \"pmids\": [\"38625937\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which kinase(s) phosphorylate the PIR domain serines in vivo during insulin resistance not identified in this study\", \"Whether the IRS-1 PIR domain mechanism is conserved across species not tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Major open questions include: the identity of the SHP-independent effector recruited by the third PIR-B ITIM; whether the distinct PIR-B functions in immune cells versus neurons use identical downstream signaling cascades; and the precise mechanism by which Pirin activates transcription at the E2F1 promoter.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Third ITIM effector unidentified\", \"No unified signaling model across immune and neuronal PIR-B contexts\", \"Pirin's transcriptional cofactors unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 2, 7, 14, 16]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [3, 4, 6]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [20]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 3, 4, 5, 7, 12, 13]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [20]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 1, 2, 5, 8, 10, 11, 14, 15]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3, 4, 6, 16, 22]}\n    ],\n    \"complexes\": [\n      \"PIR-B/SHP-1 complex\",\n      \"PIR-A/FcRγ complex\",\n      \"PIR-B/Trk/p75NTR complex\"\n    ],\n    \"partners\": [\n      \"SHP-1\",\n      \"SHP-2\",\n      \"LYN\",\n      \"FCERG1\",\n      \"BTK\",\n      \"NGFR\",\n      \"NTRK1\",\n      \"E2F1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}