{"gene":"PTPRZ1","run_date":"2026-04-28T19:45:45","timeline":{"discoveries":[{"year":1994,"finding":"Phosphacan (the extracellular domain of PTPRZ1/RPTPζ/β) binds with high affinity (Kd ~0.1 nM) to neural cell adhesion molecules N-CAM and Ng-CAM/L1 via its core glycoprotein (not chondroitin sulfate chains), and inhibits neuronal adhesion and neurite outgrowth when neurons are incubated on dishes co-coated with phosphacan and Ng-CAM.","method":"Radioligand binding assay (125I-phosphacan), Scatchard analysis, chondroitinase treatment, antibody inhibition, neurite outgrowth assay","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 — in vitro binding reconstitution with multiple orthogonal methods (radioligand binding, Scatchard, enzyme digestion, antibody blocking) and functional readout","pmids":["7528221"],"is_preprint":false},{"year":1994,"finding":"Phosphacan represents an mRNA splicing variant encoding the entire extracellular portion of the transmembrane receptor-type protein tyrosine phosphatase RPTP zeta/beta (PTPRZ1), established by cDNA cloning and peptide sequencing showing 76% identity to human RPTP zeta/beta extracellular domain; the N-terminal domain is homologous to carbonic anhydrases.","method":"cDNA cloning, peptide sequencing (CNBr, tryptic, endoproteinase Lys-C fragments), RNA analysis with domain-specific probes","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 — direct sequence identification with multiple peptide verifications; foundational molecular characterization","pmids":["7511813"],"is_preprint":false},{"year":1994,"finding":"Phosphacan (PTPRZ1 extracellular domain) binds specifically and with high affinity to tenascin-C via the core glycoprotein (not chondroitin sulfate chains), as demonstrated by bead co-aggregation and solid-phase radioligand binding, and inhibits C6 glioma cell adhesion to tenascin.","method":"Fluorescent microbead co-aggregation, solid-phase radioligand binding, Scatchard analysis, chondroitinase treatment, Fab' antibody inhibition, cell adhesion assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstituted binding with multiple orthogonal methods and functional readout","pmids":["7512960"],"is_preprint":false},{"year":1995,"finding":"The interactions of phosphacan/PTPRZ1 with neural cell adhesion molecules (Ng-CAM/L1, N-CAM) and tenascin are mediated by asparagine-linked complex-type oligosaccharides located in the carbonic anhydrase-like and fibronectin type III-like domains (at Asn-232 and Asn-381), rather than by the proteoglycan chains.","method":"Tryptic digest radioligand binding, peptide N-glycosidase F treatment under non-denaturing conditions, endo-β-N-acetylglucosaminidase H treatment, size analysis of glycopeptides","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — enzymatic dissection with multiple glycosidases and binding assays identifying specific glycosylation sites","pmids":["7559574"],"is_preprint":false},{"year":1996,"finding":"6B4 proteoglycan/phosphacan (PTPRZ1 extracellular domain) binds pleiotrophin/HB-GAM with high affinity (Kd = 0.25 nM high-affinity site, 3 nM low-affinity site); chondroitin sulfate chains mediate differential binding affinities, and heparin potently inhibits binding (IC50 = 3.5 ng/ml). Anti-6B4 antibody added to cortical neuron cultures suppressed pleiotrophin-induced neurite outgrowth, indicating the interaction is required for pleiotrophin action.","method":"Affinity chromatography purification, N-terminal amino acid sequencing, Scatchard analysis, chondroitinase ABC digestion, heparin competition assay, neurite outgrowth assay with antibody blockade","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — biochemical purification, quantitative binding assays, and functional validation in neurons","pmids":["8702927"],"is_preprint":false},{"year":1996,"finding":"Phosphacan/PTPRZ1 adsorbed as substrate exerts repulsive effects on cortical and thalamic neurons, preventing adhesion, but when sparsely seeded on poly-L-lysine co-coated with phosphacan it promotes neurite outgrowth and dendrite development of cortical neurons (not thalamic neurons) through a protein moiety (chondroitinase- and keratanase-resistant activity); this effect correlates with transient tyrosine phosphorylation of an 85 kDa protein in cortical neurons.","method":"Stripe/pattern substrate assay, chondroitinase/keratanase treatment, antibody neutralization, Western blot for tyrosine phosphorylation","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 1–2 — multiple substrate presentation modes, enzyme digestion controls, and phosphorylation readout establish mechanism","pmids":["8625816"],"is_preprint":false},{"year":1996,"finding":"Phosphacan/PTPRZ1 binds TAG-1/axonin-1 with very high affinity (Kd ~0.04 nM); approximately 70% of binding is mediated by chondroitin sulfate chains (opposite to binding of Ng-CAM/L1 and N-CAM where core protein dominates); N-deglycosylation does not affect binding to TAG-1.","method":"Radioligand binding assay, chondroitinase treatment, N-deglycosylation, Scatchard analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — quantitative binding with enzymatic dissection of glycan vs. core protein contributions","pmids":["8663515"],"is_preprint":false},{"year":1997,"finding":"Phosphacan/PTPRZ1 binds to the fibrinogen-like globe of tenascin-C (Kd ~12 nM for this single domain, nearly same as native tenascin-C); binding is calcium-dependent and mediated by the proteoglycan core protein rather than glycosaminoglycan chains; rotary shadowing EM shows phosphacan apposed to the fibrinogen globe.","method":"Recombinant tenascin-C deletion variants, radioligand binding, inhibition studies, calcium chelation, chondroitinase treatment, rotary shadowing electron microscopy","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstituted with recombinant protein domains, structural imaging, and multiple enzymatic controls","pmids":["9182584"],"is_preprint":false},{"year":1998,"finding":"Phosphacan/PTPRZ1 binds tenascin-R with high affinity (Kd 2–7 nM) via its core glycoprotein, and also binds amphoterin and HB-GAM (Kd 0.3–8 nM) predominantly through its chondroitin sulfate chains (>80% of binding); amphoterin increases phosphacan binding to contactin 5-fold.","method":"Radioligand binding assay, chondroitinase treatment, calcium chelation, Scatchard analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — quantitative binding with systematic glycan/core protein dissection for multiple ligands","pmids":["9507007"],"is_preprint":false},{"year":1998,"finding":"Phosphacan/PTPRZ1 core protein (not chondroitin sulfate chains) binds fibroblast growth factor-2 (FGF-2) with high affinity (Kd ~6 nM) and potentiates FGF-2 mitogenic activity on NIH/3T3 cells by 75–90%, comparable to heparin.","method":"Radioligand binding assay, chondroitinase treatment, Scatchard analysis, [3H]thymidine incorporation mitogenic assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstituted binding with quantitative assay and functional mitogenic readout","pmids":["9705269"],"is_preprint":false},{"year":2003,"finding":"The chondroitin sulfate heterogeneity on phosphacan/PTPRZ1 regulates binding affinity for pleiotrophin: adult brain phosphacan containing the D unit (GlcA(2S)-GalNAc(6S)) binds pleiotrophin ~5-fold more strongly (KD = 0.14 nM) than postnatal phosphacan lacking D units (KD ~1.5 nM); chondroitinase treatment abolishes this difference.","method":"Surface plasmon resonance biosensor, chondroitinase ABC digestion, immunochemical characterization of CS disaccharide composition","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — quantitative SPR with defined CS structures and enzyme digestion","pmids":["12840014"],"is_preprint":false},{"year":2003,"finding":"A novel truncated isoform of PTPRZ1 (phosphacan short isoform, PSI), corresponding to N-terminal carbonic anhydrase- and fibronectin type III-like domains, is expressed in the CNS and can interact with Ig-CAMs F3/contactin and L1, and promotes neurite outgrowth of cortical neurons as a coated substrate; PSI is not a proteoglycan (lacks GAG chains) but carries HNK-1 oligosaccharides.","method":"cDNA library screening, Northern blot, Western blot with N-terminal sequencing, co-immunoprecipitation/binding assays with F3/contactin and L1, neurite outgrowth assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 — cDNA identification, biochemical characterization, and functional neurite assay","pmids":["12700241"],"is_preprint":false},{"year":2007,"finding":"PTPRZ1 (RPTPβ/ζ) forms a functional complex with ERBB4 bridged by MAGI scaffolding proteins: MAGI interacts with both ERBB4 and RPTPβ; ERBB4 expression leads to tyrosine phosphorylation of MAGI proteins that is enhanced by neuregulin, and RPTPβ shows spatial and functional association with ERBB4/MAGI in cultured cells.","method":"Yeast two-hybrid, co-immunoprecipitation in mammalian cells, tyrosine phosphorylation assay, neuregulin stimulation","journal":"Molecular psychiatry","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal co-IP and functional phosphorylation assay in single study","pmids":["17579610"],"is_preprint":false},{"year":2007,"finding":"PTPRZ1 amplification and overexpression in renal cell carcinoma activates the beta-catenin pathway: PTPRZ1 knockdown (siRNA) in RCC cell lines decreases nuclear beta-catenin and suppresses expression of target genes (cyclin D1, c-myc, c-jun, fra-1, CD44) and cellular proliferation, without involvement of Wnt signaling.","method":"Gene expression microarray, CGH array, siRNA knockdown, Western blot for nuclear beta-catenin, gene expression analysis","journal":"The American journal of pathology","confidence":"Medium","confidence_rationale":"Tier 2 — siRNA knockdown with multiple downstream readouts in single study","pmids":["18055543"],"is_preprint":false},{"year":2008,"finding":"The transcription factor Egr-1 directly regulates PTPRZ1 (phosphacan) expression in astrocytes after ischemic injury: Egr-1 binds to a site within the phosphacan promoter and transactivates its expression; Egr-1-deficient mice show reduced phosphacan RNA and protein after experimental stroke.","method":"Gain/loss-of-function in primary astrocytes, promoter-reporter assay, chromatin immunoprecipitation (ChIP), knockout mouse model, RT-PCR, Western blot","journal":"The American journal of pathology","confidence":"High","confidence_rationale":"Tier 1–2 — ChIP, promoter assay, and in vivo knockout validation together establish transcriptional mechanism","pmids":["18556777"],"is_preprint":false},{"year":2010,"finding":"Crystal structures of the carbonic anhydrase-like domain of PTPRZ show it interacts directly with the second and third Ig repeats of CNTN1; PTPRZ binds specifically CNTN1 (but not CNTN3/4/5/6), establishing binding specificity determined by the carbonic anhydrase-like domain.","method":"X-ray crystallography, direct binding assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with functional binding validation","pmids":["20133774"],"is_preprint":false},{"year":2011,"finding":"PTPRZ binds specifically to CNTN1 expressed at the surface of oligodendrocyte precursor cells (OPCs); this PTPRZ/CNTN1 complex inhibits OPC proliferation and promotes their differentiation into mature oligodendrocytes, as shown in PTPRZ-deficient mice.","method":"Cocrystal structure of PTPRZ carbonic anhydrase-like domain with CNTN1 Ig repeats, surface binding assays, glial cell population analysis in Ptprz-/- vs. wild-type mice","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 — crystal structure plus knockout mouse with defined cellular phenotype","pmids":["21969550"],"is_preprint":false},{"year":2012,"finding":"RPTPζ/phosphacan (PTPRZ1) undergoes aberrant O-mannosyl glycosylation in the brain: it is a major substrate for POMGnT1-mediated O-mannosylation; in POMGnT1-knockout mice modeling muscle-eye-brain disease, RPTPζ/phosphacan shifts to lower molecular weight and loses HNK-1 epitopes.","method":"Western blot, immunoprecipitation, glycan epitope analysis in POMGnT1 knockout mouse brain","journal":"Neuroscience","confidence":"High","confidence_rationale":"Tier 2 — knockout mouse model with biochemical characterization demonstrating specific glycan modification","pmids":["22728091"],"is_preprint":false},{"year":2013,"finding":"Phosphacan/PTPRZ1 is identified as the major carrier of O-mannose-linked HNK-1 glycan in developing mouse brain; GlcAT-P specifically synthesizes O-linked HNK-1 onto phosphacan; the 6B4 monoclonal antibody epitope is O-mannose-linked HNK-1 on phosphacan, as shown in GlcAT-P-deficient mice.","method":"Mass spectrometric glycan analysis, GlcAT-P knockout mice, co-expression in cultured cells, immunoblot","journal":"Glycobiology","confidence":"High","confidence_rationale":"Tier 1 — mass spectrometry with knockout mouse validation and cell expression experiments","pmids":["24352591"],"is_preprint":false},{"year":2014,"finding":"PTPRZ1-MET (ZM) fusion transcripts arise from chromosomal translocation involving introns 3 or 8 of PTPRZ1 and intron 1 of MET in secondary glioblastomas; exogenous expression of ZM fusion in U87MG cells enhances cell migration and invasion.","method":"RNA-seq, RT-PCR, Sanger sequencing, genomic translocation analysis, cell migration/invasion assay after ZM overexpression","journal":"Genome research","confidence":"High","confidence_rationale":"Tier 2 — recurrent fusion identified by sequencing in multiple cohorts, functional overexpression assay with migration readout","pmids":["25135958"],"is_preprint":false},{"year":2015,"finding":"ZM fusion proteins preserve wild-type MET processing and dimerization properties, and enhance MET phosphorylation in both HGF-dependent and HGF-independent manners, with increased MET mRNA expression induced by fusion with PTPRZ1 promoter.","method":"Western blot for phospho-MET, HGF stimulation assays, dimerization analysis, mRNA expression analysis in patient samples and transfected cells","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 — multiple biochemical assays in single study establishing fusion mechanism","pmids":["25935522"],"is_preprint":false},{"year":2015,"finding":"PTPRZ specifically dephosphorylates GIT1 at Tyr-554 in vitro and in HEK293T cells; this dephosphorylation promotes GIT1 association with paxillin and Hic-5; in Ptprz-deficient mice, GIT1 Tyr-554 phosphorylation is higher and paxillin binding is lower; cyclic phosphorylation-dephosphorylation at GIT1 Tyr-554 is critical for cell motility.","method":"In vitro phosphatase assay, site-directed mutagenesis of GIT1 Tyr-554, co-immunoprecipitation, Ptprz-/- mouse brain biochemistry, random motility/wound healing/Boyden chamber assays with GIT1 mutants","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1 — in vitro substrate assay with mutagenesis, in vivo knockout validation, and functional cell motility readout","pmids":["25742295"],"is_preprint":false},{"year":2016,"finding":"The chondroitin sulfate (CS) moiety of PTPRZ-A maintains it in a monomeric active (dephosphorylated-substrate) state by electrostatic repulsion between CS chains, preventing spontaneous clustering; pleiotrophin (PTN) binding induces receptor clustering/inactivation by neutralizing CS repulsion, thereby promoting OPC differentiation. CS removal by chondroitinase ABC similarly inactivates PTPRZ and promotes OPC differentiation.","method":"Surface receptor localization imaging (punctate vs. diffuse distribution), chondroitinase ABC treatment of OPCs, PTN ligand application, oligodendrocyte differentiation assay, Ptn-deficient mouse analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 — mechanistic model tested with enzyme treatment, knockout mice, and imaging in single study","pmids":["27445335"],"is_preprint":false},{"year":2016,"finding":"Crystal structure of the PTPRZ catalytic domain was determined; SCB4380 binds stoichiometrically to the catalytic pocket and inhibits PTPRZ phosphatase activity; site-directed mutagenesis validated the docking-predicted binding mode; intracellular delivery of SCB4380 in C6 glioblastoma cells inhibits PTPRZ activity, suppresses migration and proliferation in vitro, and reduces tumor growth in vivo.","method":"X-ray crystallography, biochemical phosphatase assay, mass spectrometry, molecular docking, site-directed mutagenesis, liposome drug delivery, in vitro migration/proliferation assay, rat allograft tumor model","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with mutagenesis and in vivo functional validation","pmids":["26857455"],"is_preprint":false},{"year":2017,"finding":"TAMs secrete pleiotrophin (PTN) to activate PTPRZ1 signaling in glioma stem cells (GSCs); disrupting PTPRZ1 (shRNA or anti-PTPRZ1 antibody) abrogates GSC maintenance and tumorigenicity; silencing PTN in M2-like macrophages reduces their pro-tumorigenic activity; PTPRZ1 is preferentially expressed on GSCs.","method":"GSC co-implantation with M2 macrophages, shRNA knockdown, antibody blockade, neurosphere formation assay, in vivo tumor growth assay","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — multiple loss-of-function approaches (shRNA + antibody) with in vivo tumor readout establishing paracrine signaling mechanism","pmids":["28569747"],"is_preprint":false},{"year":2017,"finding":"PTPRZ knockdown in C6 and U251 glioblastoma sphere-forming cells alters expression of stem cell transcription factors SOX2, OLIG2, and POU3F2 and decreases sphere-forming ability; the small-molecule allosteric inhibitor NAZ2329 reduces SOX2 expression and sphere-forming ability, and slows tumor growth in xenograft model when combined with temozolomide.","method":"Stable PTPRZ shRNA knockdown, small-molecule inhibitor (NAZ2329) treatment, sphere-forming assay, Western blot for transcription factors, C6 xenograft mouse model","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 — genetic knockdown and pharmacological inhibition with in vivo tumor model","pmids":["28717188"],"is_preprint":false},{"year":2019,"finding":"PTPRZ dephosphorylates AFAP1L2 at tyrosine residues in vitro and in HEK293T cells; PTN-PTPRZ signaling enhances phosphorylation of AFAP1L2, AKT, and mTOR in OPC-like cells to activate the PI3K-AKT pathway for OPC differentiation; catalytically inactive PTPRZ knock-in mice (CS mutation) show higher AFAP1L2/AKT/mTOR phosphorylation and accelerated OPC differentiation and remyelination.","method":"In vitro phosphatase assay with AFAP1L2 substrate, HEK293T cell transfection, PTN stimulation of OL1 cells, PTPRZ catalytic dead knock-in mouse (Cys-to-Ser), cuprizone demyelination model, Western blot for phosphoproteins","journal":"Glia","confidence":"High","confidence_rationale":"Tier 1 — in vitro substrate assay combined with knock-in mouse and demyelination model","pmids":["30667096"],"is_preprint":false},{"year":2019,"finding":"RPTPζ/PTPRZ1 is required for perineuronal net (PNN) reticulated structure: in Ptprz1-/- mice, PNNs lose their reticular lattice and form puncta, phenocopying tenascin-R knockout; RPTPζ mediates one of two distinct modes of PNN component anchoring to the neuronal surface (the other requiring hyaluronan).","method":"Ptprz1-/- mouse analysis, immunostaining of PNN components, biochemical fractionation, neuronal culture experiments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — knockout mouse with defined structural phenotype and biochemical analysis","pmids":["31822561"],"is_preprint":false},{"year":2019,"finding":"Ptprz-knockout mice lacking all three isoforms show increased exploratory activity, deficits in spatial and contextual learning, and reduced responses to methamphetamine including reduced methamphetamine-evoked dopamine release in nucleus accumbens; phosphatase activity of PTPRZ receptor isoforms (CS mutant mice) is specifically required for dopaminergic regulation, while the extracellular region (including secretory isoform) mediates behavioral responses to novelty and aversive memory.","method":"Behavioral testing (open field, inhibitory avoidance), Ptprz-KO and knock-in mouse lines (CS catalytic dead, ΔD2 domain deletion), microdialysis for dopamine measurement","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 — multiple genetic mouse models with domain-specific behavioral and neurochemical readouts","pmids":["31194769"],"is_preprint":false},{"year":2019,"finding":"GlcNAc6ST3 (encoded by Chst5, expressed in oligodendrocytes in adult brain) is a major keratan sulfate sulfotransferase for PTPRZ1; a KS-modified isoform of PTPRZ1 is a major R-10G-reactive KS proteoglycan associated with perineuronal nets in adult brain.","method":"Immunostaining with R-10G anti-KS antibody, Chst5-specific in situ hybridization, mass spectrometry-based proteoglycan identification, adult visual cortex analysis","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 — enzyme identification with biochemical proteoglycan characterization in single study","pmids":["30867513"],"is_preprint":false},{"year":2021,"finding":"ZM fusion protein activates MET kinase in a ligand-independent manner, attributed to a coiled-coil motif from the PTPRZ1 fusion partner that promotes dimerization/activation of the MET extracellular domain; ZM-positive clinical specimens show hyperactivation of MET signaling.","method":"3D structural prediction, coiled-coil motif analysis, cell line experiments with ZM expression, phospho-MET analysis in patient specimens","journal":"CNS neuroscience & therapeutics","confidence":"Medium","confidence_rationale":"Tier 3 — structural prediction with supporting cell line and clinical data; single study","pmids":["33645009"],"is_preprint":false},{"year":2023,"finding":"RPTPζ/PTPRZ1 ectodomain forms direct protein-protein complexes with tenascin-R and tenascin-C; structural basis for these interactions was determined; mutations at the RPTPζ-TNR interface impair PNN formation in dissociated neuronal cultures; TNR is absent from net structures in Ptprz1-/- neuronal cultures.","method":"Structural determination of PTPRZ1 ectodomain-TNR complex, binding assays, Ptprz1-/- neuronal cultures, site-directed mutagenesis at interface residues, immunostaining of PNN components","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — structure with mutagenesis and knockout culture validation","pmids":["37356715"],"is_preprint":false},{"year":2023,"finding":"PTPRZ1 deletion or pharmacological inhibition of its phosphatase activity in endothelial cells activates c-Met and Akt kinase, increasing angiogenesis; PTPRZ1 mediates c-Met activation by VEGFA165 and pleiotrophin in endothelial cells, and this effect is abolished by the c-Met inhibitor crizotinib; Ptprz1-/- mice show enhanced LUAD growth and lung angiogenesis.","method":"Ptprz1-/- mouse model, lung microvascular endothelial cell isolation, PTPRZ1 pharmacological inhibitor, Western blot for c-Met/Akt phosphorylation, in vitro angiogenesis assay, LUAD urethane model, crizotinib rescue experiment","journal":"International journal of cancer","confidence":"High","confidence_rationale":"Tier 2 — genetic and pharmacological loss-of-function with in vivo tumor model and rescue experiment","pmids":["37260355"],"is_preprint":false},{"year":2024,"finding":"PTPRZ1-MET (ZM) fusion in GSCs activates MET-STAT3-ISG20 axis; ZM-positive GSCs secrete ISG20 extracellularly to recruit macrophages and drive their polarization toward an immunosuppressive M2-like phenotype, thereby promoting tumor progression.","method":"RNA-seq of sGBM patient tissues, GSC sphere cultures with ZM, ISG20 knockdown/overexpression, macrophage polarization assays, conditioned medium experiments","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 2 — pathway identification with functional knockdown and macrophage polarization readout in single study","pmids":["38685521"],"is_preprint":false},{"year":2025,"finding":"Curcumin directly interacts with PTPRZ1 to maintain its enzymatic phosphatase activity, which in turn regulates phosphorylation of the m6A-reader YTHDF2; this PTPRZ1-YTHDF2 axis modulates expression of inflammatory genes to reduce microglial inflammatory responses.","method":"Binding assay of curcumin with PTPRZ1, phosphatase activity assay, phosphorylation analysis of YTHDF2, gene expression analysis, microglial inflammatory assay","journal":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","confidence":"Medium","confidence_rationale":"Tier 2 — enzymatic activity maintained by curcumin with downstream phosphorylation readout; single study","pmids":["39921492"],"is_preprint":false}],"current_model":"PTPRZ1 encodes a receptor-type protein tyrosine phosphatase whose extracellular domain (phosphacan) functions as a chondroitin sulfate proteoglycan that binds pleiotrophin, midkine, tenascins, neural cell adhesion molecules (L1/Ng-CAM, N-CAM, TAG-1/contactin-1), and FGF-2 to regulate neurite outgrowth, cell adhesion, and oligodendrocyte precursor differentiation; its negatively charged chondroitin sulfate chains keep the receptor in a monomeric active state until pleiotrophin binding induces clustering and receptor inactivation, activating the AFAP1L2-PI3K-AKT pathway to promote OPC differentiation; the intracellular phosphatase domain dephosphorylates substrates including GIT1 (Tyr-554), AFAP1L2, ALK, and TrkA to regulate cell motility, dopaminergic signaling, and chemoresistance, while the PTPRZ1-MET fusion activates MET kinase in a ligand-independent, coiled-coil-mediated manner to drive glioma progression."},"narrative":{"teleology":[{"year":1994,"claim":"Establishing PTPRZ1's molecular identity: phosphacan was shown to be the secreted extracellular domain splice variant of receptor-type phosphatase RPTPζ/β, with an N-terminal carbonic anhydrase-like domain, resolving whether the abundant brain proteoglycan was related to a transmembrane signaling receptor.","evidence":"cDNA cloning and peptide sequencing of phosphacan showing 76% identity to RPTPζ/β extracellular domain","pmids":["7511813"],"confidence":"High","gaps":["Full-length transmembrane isoform function not yet tested","Relationship between secreted and transmembrane isoforms in vivo unclear"]},{"year":1994,"claim":"Defining the extracellular ligand repertoire: phosphacan was found to bind N-CAM, Ng-CAM/L1, and tenascin-C with high affinity via its core glycoprotein (not CS chains), and to inhibit neurite outgrowth on Ng-CAM substrates, establishing PTPRZ1 as a multivalent neural adhesion regulator.","evidence":"Radioligand binding, Scatchard analysis, chondroitinase treatment, neurite outgrowth assays on coated substrates","pmids":["7528221","7512960"],"confidence":"High","gaps":["Signaling consequences of these interactions on intracellular phosphatase activity unknown","In vivo relevance of individual ligand interactions not tested"]},{"year":1996,"claim":"Identifying pleiotrophin as a key regulatory ligand: pleiotrophin/HB-GAM bound phosphacan with sub-nanomolar affinity predominantly through chondroitin sulfate chains, and antibody blockade showed this interaction was required for pleiotrophin-induced neurite outgrowth, establishing the ligand–receptor pair central to PTPRZ1 biology.","evidence":"Affinity chromatography, Scatchard analysis, chondroitinase digestion, heparin competition, neurite outgrowth antibody blockade in cortical neurons","pmids":["8702927"],"confidence":"High","gaps":["Whether pleiotrophin binding regulates phosphatase activity was unknown","In vivo requirement not yet tested in knockout"]},{"year":1996,"claim":"Resolving glycan versus core protein contributions to distinct ligands: TAG-1/contactin binding was ~70% CS-mediated while N-CAM/L1 binding was core-protein-mediated, and asparagine-linked complex oligosaccharides at specific sites (Asn-232, Asn-381) were identified as the core determinants for CAM and tenascin interactions.","evidence":"Chondroitinase treatment, N-glycosidase F/Endo H digestion, tryptic fragment binding assays","pmids":["8663515","7559574"],"confidence":"High","gaps":["Structural basis of selective glycan recognition not resolved","Functional consequence of glycan heterogeneity on signaling not addressed"]},{"year":1998,"claim":"Expanding the ligand network to include tenascin-R, amphoterin, and FGF-2: phosphacan core protein bound tenascin-R and FGF-2 with nanomolar affinity, with FGF-2 binding potentiating its mitogenic activity comparably to heparin, broadening PTPRZ1's role beyond adhesion to growth factor co-receptor function.","evidence":"Radioligand binding with chondroitinase treatment, Scatchard analysis, thymidine incorporation mitogenesis assay","pmids":["9507007","9705269"],"confidence":"High","gaps":["Whether FGF-2 co-receptor activity operates in CNS cells specifically was not tested","Signaling downstream of PTPRZ1-FGF-2 not characterized"]},{"year":2003,"claim":"Demonstrating that CS sulfation pattern developmentally tunes ligand affinity: adult brain phosphacan carrying D-unit disaccharides bound pleiotrophin ~5-fold more tightly than postnatal phosphacan lacking D-units, providing a glycan-code mechanism for age-dependent signaling regulation.","evidence":"Surface plasmon resonance with chondroitinase digestion and immunochemical CS disaccharide profiling","pmids":["12840014"],"confidence":"High","gaps":["Enzymes responsible for D-unit synthesis on PTPRZ1 not identified","Functional consequence of age-dependent affinity shift on OPC biology not tested"]},{"year":2010,"claim":"Structural determination of the carbonic anhydrase-like domain revealed the molecular basis of CNTN1-selective binding: crystal structures showed direct interaction with Ig repeats 2–3 of CNTN1 but not other contactins, resolving how PTPRZ1 achieves ligand specificity.","evidence":"X-ray crystallography of PTPRZ1 CA domain, direct binding assays with contactin family members","pmids":["20133774","21969550"],"confidence":"High","gaps":["Whether CS chains modulate CNTN1 interaction in vivo was unclear","Full ectodomain structure not resolved"]},{"year":2011,"claim":"Connecting PTPRZ1–CNTN1 binding to oligodendrocyte biology: PTPRZ1 binds CNTN1 on OPC surfaces and this complex inhibits OPC proliferation while promoting differentiation, with Ptprz-deficient mice showing altered glial populations.","evidence":"Co-crystal structure, surface binding assays, Ptprz−/− mouse glial cell analysis","pmids":["21969550"],"confidence":"High","gaps":["Intracellular phosphatase substrates mediating OPC differentiation unknown at this point","Whether CNTN1 interaction affects phosphatase activity not tested"]},{"year":2015,"claim":"Identifying the first specific intracellular substrate: PTPRZ dephosphorylates GIT1 at Tyr-554, regulating its association with paxillin/Hic-5 and cell motility, validated by elevated GIT1 phosphorylation in Ptprz-knockout mouse brain.","evidence":"In vitro phosphatase assay, Tyr-554 mutagenesis, co-immunoprecipitation, Ptprz−/− mouse biochemistry, wound healing and Boyden chamber assays","pmids":["25742295"],"confidence":"High","gaps":["Whether GIT1 dephosphorylation mediates PTPRZ1's neural functions not tested","Full substrate repertoire unknown"]},{"year":2016,"claim":"Elucidating the CS-mediated autoinhibition mechanism: chondroitin sulfate chains maintain PTPRZ in a monomeric active state through electrostatic repulsion; pleiotrophin neutralizes this repulsion to induce clustering and phosphatase inactivation, thereby promoting OPC differentiation — a unified model linking ligand binding to phosphatase regulation.","evidence":"Receptor distribution imaging, chondroitinase treatment of OPCs, pleiotrophin stimulation, OPC differentiation assay, Ptn−/− mouse","pmids":["27445335"],"confidence":"High","gaps":["Direct biophysical measurement of clustering (e.g., FRET, single-molecule) not provided","Whether other ligands similarly cluster the receptor unknown"]},{"year":2019,"claim":"Identifying the downstream signaling axis for OPC differentiation: PTPRZ dephosphorylates AFAP1L2, and pleiotrophin-induced receptor inactivation activates the AFAP1L2–PI3K–AKT–mTOR pathway; catalytically inactive PTPRZ knock-in mice show accelerated OPC differentiation and remyelination after cuprizone demyelination.","evidence":"In vitro phosphatase assay, PTN stimulation in OL1 cells, PTPRZ catalytic-dead knock-in mouse, cuprizone demyelination model","pmids":["30667096"],"confidence":"High","gaps":["Whether AFAP1L2 is the sole mediator or acts with other substrates not resolved","Therapeutic potential of PTPRZ inhibition for remyelination not tested in disease models beyond cuprizone"]},{"year":2019,"claim":"Establishing PTPRZ1's structural role in perineuronal nets: Ptprz1-knockout mice lose the reticular PNN lattice phenocopying tenascin-R loss, demonstrating that PTPRZ1 anchors PNN components to neuronal surfaces via one of two distinct mechanisms.","evidence":"Ptprz1−/− mouse immunostaining of PNN components, biochemical fractionation, neuronal cultures","pmids":["31822561"],"confidence":"High","gaps":["Molecular details of how PTPRZ1 organizes PNN lattice versus punctate structures unclear","Functional consequences for synaptic plasticity not directly measured"]},{"year":2019,"claim":"Dissecting phosphatase-dependent versus ectodomain-dependent behavioral functions: using domain-specific knock-in mice, phosphatase activity was shown to be required for dopaminergic regulation (methamphetamine-evoked DA release), while the extracellular domain mediates behavioral responses to novelty and aversive memory.","evidence":"Ptprz-KO, catalytic-dead, and ΔD2 knock-in mice; behavioral testing; nucleus accumbens microdialysis","pmids":["31194769"],"confidence":"High","gaps":["Specific phosphatase substrates mediating dopaminergic regulation not identified","Neural circuit basis of behavioral phenotypes not mapped"]},{"year":2014,"claim":"Discovery of oncogenic PTPRZ1-MET fusion: recurrent PTPRZ1-MET translocation-derived fusions were identified in secondary glioblastomas and shown to enhance glioma cell migration and invasion upon expression.","evidence":"RNA-seq and genomic analysis of glioblastoma cohorts, RT-PCR validation, Sanger sequencing, migration/invasion assay in U87MG cells","pmids":["25135958"],"confidence":"High","gaps":["Mechanism of constitutive MET activation by fusion not resolved","In vivo tumorigenicity of fusion not demonstrated"]},{"year":2021,"claim":"Mechanism of fusion-driven MET activation clarified: a coiled-coil motif from the PTPRZ1 portion of ZM fusion was proposed to mediate ligand-independent dimerization and constitutive MET kinase activation.","evidence":"3D structural prediction, coiled-coil analysis, phospho-MET in ZM-expressing cells and clinical specimens","pmids":["33645009"],"confidence":"Medium","gaps":["Coiled-coil model based on prediction, not experimentally validated structure","Mutagenesis of coiled-coil not performed"]},{"year":2023,"claim":"Structural basis for PNN assembly resolved: the PTPRZ1 ectodomain–tenascin-R complex structure was determined, and interface mutations disrupted PNN formation in neuronal cultures, directly linking structural interactions to extracellular matrix organization.","evidence":"Structural determination of PTPRZ1-TNR complex, site-directed mutagenesis, Ptprz1−/− neuronal culture PNN analysis","pmids":["37356715"],"confidence":"High","gaps":["In vivo validation of interface mutations not performed","Whether tenascin-C binding uses the same or different interface not resolved"]},{"year":2024,"claim":"ZM fusion drives immunosuppressive tumor microenvironment: PTPRZ1-MET fusion in GSCs activates MET–STAT3–ISG20 signaling, with secreted ISG20 recruiting macrophages and polarizing them to immunosuppressive M2 phenotype.","evidence":"RNA-seq of sGBM tissues, ISG20 knockdown/overexpression, macrophage polarization assays, conditioned medium experiments","pmids":["38685521"],"confidence":"Medium","gaps":["In vivo immune phenotype of ZM-positive tumors not validated in immunocompetent models","Whether ISG20 secretion is the dominant immunosuppressive mechanism unclear"]},{"year":null,"claim":"Key unresolved questions include the full substrate repertoire of PTPRZ1 phosphatase in neural and non-neural contexts, the structural basis of CS-mediated receptor clustering upon pleiotrophin binding, whether pharmacological PTPRZ1 inhibition can promote remyelination in human demyelinating disease, and the therapeutic vulnerability of PTPRZ1-MET fusion-driven gliomas to targeted MET inhibition in clinical settings.","evidence":"","pmids":[],"confidence":"Low","gaps":["Complete phosphatase substrate repertoire not systematically identified","No high-resolution structure of full-length transmembrane PTPRZ1","Clinical translation of PTPRZ1 inhibitors for remyelination or glioma therapy untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[21,26,23,34]},{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[0,2,6]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[22,32]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[16,22,27]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[1,4,8,9,11]},{"term_id":"GO:0031012","term_label":"extracellular matrix","supporting_discovery_ids":[27,31]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[22,26,32]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[16,26]},{"term_id":"R-HSA-1474244","term_label":"Extracellular matrix organization","supporting_discovery_ids":[27,31]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[28]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[19,24,25,33]}],"complexes":[],"partners":["PTN","CNTN1","GIT1","AFAP1L2","TNC","TNR","NCAM1","L1CAM"],"other_free_text":[]},"mechanistic_narrative":"PTPRZ1 encodes a receptor-type protein tyrosine phosphatase that functions as a major chondroitin sulfate proteoglycan of the central nervous system, regulating neural cell adhesion, neurite outgrowth, oligodendrocyte precursor cell (OPC) differentiation, perineuronal net assembly, and dopaminergic signaling. Its extracellular domain (shed as phosphacan) binds pleiotrophin, midkine, tenascins (C and R), neural cell adhesion molecules (N-CAM, L1/Ng-CAM, TAG-1/contactin-1), and FGF-2 through distinct glycan- and core-protein-mediated interactions, with chondroitin sulfate chains maintaining the receptor in a monomeric active state via electrostatic repulsion until pleiotrophin binding neutralizes this repulsion, induces receptor clustering/inactivation, and activates the AFAP1L2–PI3K–AKT pathway to promote OPC differentiation and remyelination [PMID:27445335, PMID:30667096, PMID:7528221, PMID:8702927]. The intracellular phosphatase domain dephosphorylates substrates including GIT1 at Tyr-554 and AFAP1L2 to regulate cell motility and myelination, while PTPRZ1 interactions with tenascin-R are structurally required for perineuronal net lattice formation [PMID:25742295, PMID:31822561, PMID:37356715]. Oncogenic PTPRZ1-MET fusion transcripts arising from chromosomal translocation in glioblastoma activate MET kinase in a ligand-independent, coiled-coil-mediated manner, driving glioma stem cell maintenance, migration, and immunosuppressive macrophage polarization [PMID:25135958, PMID:33645009, PMID:38685521]."},"prefetch_data":{"uniprot":{"accession":"P23471","full_name":"Receptor-type tyrosine-protein phosphatase zeta","aliases":["Protein-tyrosine phosphatase receptor type Z polypeptide 1","Protein-tyrosine phosphatase receptor type Z polypeptide 2","R-PTP-zeta-2"],"length_aa":2315,"mass_kda":254.6,"function":"Protein tyrosine phosphatase that negatively regulates oligodendrocyte precursor proliferation in the embryonic spinal cord. Required for normal differentiation of the precursor cells into mature, fully myelinating oligodendrocytes. May play a role in protecting oligondendrocytes against apoptosis. May play a role in the establishment of contextual memory, probably via the dephosphorylation of proteins that are part of important signaling cascades (By similarity)","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/P23471/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PTPRZ1","classification":"Not Classified","n_dependent_lines":14,"n_total_lines":1208,"dependency_fraction":0.011589403973509934},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PTPRZ1","total_profiled":1310},"omim":[{"mim_id":"604008","title":"PROTEIN-TYROSINE PHOSPHATASE, RECEPTOR-TYPE, ZETA-2; PTPRZ2","url":"https://www.omim.org/entry/604008"},{"mim_id":"602346","title":"CONTACTIN-ASSOCIATED PROTEIN 1; CNTNAP1","url":"https://www.omim.org/entry/602346"},{"mim_id":"176891","title":"PROTEIN-TYROSINE PHOSPHATASE, RECEPTOR-TYPE, ZETA-1; PTPRZ1","url":"https://www.omim.org/entry/176891"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"},{"location":"Vesicles","reliability":"Additional"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":150.5}],"url":"https://www.proteinatlas.org/search/PTPRZ1"},"hgnc":{"alias_symbol":["PTP18","RPTPB","phosphacan"],"prev_symbol":["PTPZ","PTPRZ"]},"alphafold":{"accession":"P23471","domains":[{"cath_id":"3.10.200.10","chopping":"62-299","consensus_level":"high","plddt":85.8434,"start":62,"end":299},{"cath_id":"2.60.40.10","chopping":"316-409","consensus_level":"high","plddt":80.4438,"start":316,"end":409},{"cath_id":"3.90.190.10","chopping":"1700-1996","consensus_level":"medium","plddt":88.7486,"start":1700,"end":1996},{"cath_id":"3.90.190.10","chopping":"2031-2067_2077-2290","consensus_level":"high","plddt":88.771,"start":2031,"end":2290}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P23471","model_url":"https://alphafold.ebi.ac.uk/files/AF-P23471-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P23471-F1-predicted_aligned_error_v6.png","plddt_mean":54.16},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PTPRZ1","jax_strain_url":"https://www.jax.org/strain/search?query=PTPRZ1"},"sequence":{"accession":"P23471","fasta_url":"https://rest.uniprot.org/uniprotkb/P23471.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P23471/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P23471"}},"corpus_meta":[{"pmid":"12895450","id":"PMC_12895450","title":"The 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chondroitinase treatment, antibody inhibition, neurite outgrowth assay\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro binding reconstitution with multiple orthogonal methods (radioligand binding, Scatchard, enzyme digestion, antibody blocking) and functional readout\",\n      \"pmids\": [\"7528221\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Phosphacan represents an mRNA splicing variant encoding the entire extracellular portion of the transmembrane receptor-type protein tyrosine phosphatase RPTP zeta/beta (PTPRZ1), established by cDNA cloning and peptide sequencing showing 76% identity to human RPTP zeta/beta extracellular domain; the N-terminal domain is homologous to carbonic anhydrases.\",\n      \"method\": \"cDNA cloning, peptide sequencing (CNBr, tryptic, endoproteinase Lys-C fragments), RNA analysis with domain-specific probes\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct sequence identification with multiple peptide verifications; foundational molecular characterization\",\n      \"pmids\": [\"7511813\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Phosphacan (PTPRZ1 extracellular domain) binds specifically and with high affinity to tenascin-C via the core glycoprotein (not chondroitin sulfate chains), as demonstrated by bead co-aggregation and solid-phase radioligand binding, and inhibits C6 glioma cell adhesion to tenascin.\",\n      \"method\": \"Fluorescent microbead co-aggregation, solid-phase radioligand binding, Scatchard analysis, chondroitinase treatment, Fab' antibody inhibition, cell adhesion assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted binding with multiple orthogonal methods and functional readout\",\n      \"pmids\": [\"7512960\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"The interactions of phosphacan/PTPRZ1 with neural cell adhesion molecules (Ng-CAM/L1, N-CAM) and tenascin are mediated by asparagine-linked complex-type oligosaccharides located in the carbonic anhydrase-like and fibronectin type III-like domains (at Asn-232 and Asn-381), rather than by the proteoglycan chains.\",\n      \"method\": \"Tryptic digest radioligand binding, peptide N-glycosidase F treatment under non-denaturing conditions, endo-β-N-acetylglucosaminidase H treatment, size analysis of glycopeptides\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — enzymatic dissection with multiple glycosidases and binding assays identifying specific glycosylation sites\",\n      \"pmids\": [\"7559574\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"6B4 proteoglycan/phosphacan (PTPRZ1 extracellular domain) binds pleiotrophin/HB-GAM with high affinity (Kd = 0.25 nM high-affinity site, 3 nM low-affinity site); chondroitin sulfate chains mediate differential binding affinities, and heparin potently inhibits binding (IC50 = 3.5 ng/ml). Anti-6B4 antibody added to cortical neuron cultures suppressed pleiotrophin-induced neurite outgrowth, indicating the interaction is required for pleiotrophin action.\",\n      \"method\": \"Affinity chromatography purification, N-terminal amino acid sequencing, Scatchard analysis, chondroitinase ABC digestion, heparin competition assay, neurite outgrowth assay with antibody blockade\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — biochemical purification, quantitative binding assays, and functional validation in neurons\",\n      \"pmids\": [\"8702927\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Phosphacan/PTPRZ1 adsorbed as substrate exerts repulsive effects on cortical and thalamic neurons, preventing adhesion, but when sparsely seeded on poly-L-lysine co-coated with phosphacan it promotes neurite outgrowth and dendrite development of cortical neurons (not thalamic neurons) through a protein moiety (chondroitinase- and keratanase-resistant activity); this effect correlates with transient tyrosine phosphorylation of an 85 kDa protein in cortical neurons.\",\n      \"method\": \"Stripe/pattern substrate assay, chondroitinase/keratanase treatment, antibody neutralization, Western blot for tyrosine phosphorylation\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple substrate presentation modes, enzyme digestion controls, and phosphorylation readout establish mechanism\",\n      \"pmids\": [\"8625816\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Phosphacan/PTPRZ1 binds TAG-1/axonin-1 with very high affinity (Kd ~0.04 nM); approximately 70% of binding is mediated by chondroitin sulfate chains (opposite to binding of Ng-CAM/L1 and N-CAM where core protein dominates); N-deglycosylation does not affect binding to TAG-1.\",\n      \"method\": \"Radioligand binding assay, chondroitinase treatment, N-deglycosylation, Scatchard analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — quantitative binding with enzymatic dissection of glycan vs. core protein contributions\",\n      \"pmids\": [\"8663515\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Phosphacan/PTPRZ1 binds to the fibrinogen-like globe of tenascin-C (Kd ~12 nM for this single domain, nearly same as native tenascin-C); binding is calcium-dependent and mediated by the proteoglycan core protein rather than glycosaminoglycan chains; rotary shadowing EM shows phosphacan apposed to the fibrinogen globe.\",\n      \"method\": \"Recombinant tenascin-C deletion variants, radioligand binding, inhibition studies, calcium chelation, chondroitinase treatment, rotary shadowing electron microscopy\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted with recombinant protein domains, structural imaging, and multiple enzymatic controls\",\n      \"pmids\": [\"9182584\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Phosphacan/PTPRZ1 binds tenascin-R with high affinity (Kd 2–7 nM) via its core glycoprotein, and also binds amphoterin and HB-GAM (Kd 0.3–8 nM) predominantly through its chondroitin sulfate chains (>80% of binding); amphoterin increases phosphacan binding to contactin 5-fold.\",\n      \"method\": \"Radioligand binding assay, chondroitinase treatment, calcium chelation, Scatchard analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — quantitative binding with systematic glycan/core protein dissection for multiple ligands\",\n      \"pmids\": [\"9507007\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Phosphacan/PTPRZ1 core protein (not chondroitin sulfate chains) binds fibroblast growth factor-2 (FGF-2) with high affinity (Kd ~6 nM) and potentiates FGF-2 mitogenic activity on NIH/3T3 cells by 75–90%, comparable to heparin.\",\n      \"method\": \"Radioligand binding assay, chondroitinase treatment, Scatchard analysis, [3H]thymidine incorporation mitogenic assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted binding with quantitative assay and functional mitogenic readout\",\n      \"pmids\": [\"9705269\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The chondroitin sulfate heterogeneity on phosphacan/PTPRZ1 regulates binding affinity for pleiotrophin: adult brain phosphacan containing the D unit (GlcA(2S)-GalNAc(6S)) binds pleiotrophin ~5-fold more strongly (KD = 0.14 nM) than postnatal phosphacan lacking D units (KD ~1.5 nM); chondroitinase treatment abolishes this difference.\",\n      \"method\": \"Surface plasmon resonance biosensor, chondroitinase ABC digestion, immunochemical characterization of CS disaccharide composition\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — quantitative SPR with defined CS structures and enzyme digestion\",\n      \"pmids\": [\"12840014\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"A novel truncated isoform of PTPRZ1 (phosphacan short isoform, PSI), corresponding to N-terminal carbonic anhydrase- and fibronectin type III-like domains, is expressed in the CNS and can interact with Ig-CAMs F3/contactin and L1, and promotes neurite outgrowth of cortical neurons as a coated substrate; PSI is not a proteoglycan (lacks GAG chains) but carries HNK-1 oligosaccharides.\",\n      \"method\": \"cDNA library screening, Northern blot, Western blot with N-terminal sequencing, co-immunoprecipitation/binding assays with F3/contactin and L1, neurite outgrowth assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — cDNA identification, biochemical characterization, and functional neurite assay\",\n      \"pmids\": [\"12700241\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PTPRZ1 (RPTPβ/ζ) forms a functional complex with ERBB4 bridged by MAGI scaffolding proteins: MAGI interacts with both ERBB4 and RPTPβ; ERBB4 expression leads to tyrosine phosphorylation of MAGI proteins that is enhanced by neuregulin, and RPTPβ shows spatial and functional association with ERBB4/MAGI in cultured cells.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation in mammalian cells, tyrosine phosphorylation assay, neuregulin stimulation\",\n      \"journal\": \"Molecular psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP and functional phosphorylation assay in single study\",\n      \"pmids\": [\"17579610\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PTPRZ1 amplification and overexpression in renal cell carcinoma activates the beta-catenin pathway: PTPRZ1 knockdown (siRNA) in RCC cell lines decreases nuclear beta-catenin and suppresses expression of target genes (cyclin D1, c-myc, c-jun, fra-1, CD44) and cellular proliferation, without involvement of Wnt signaling.\",\n      \"method\": \"Gene expression microarray, CGH array, siRNA knockdown, Western blot for nuclear beta-catenin, gene expression analysis\",\n      \"journal\": \"The American journal of pathology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — siRNA knockdown with multiple downstream readouts in single study\",\n      \"pmids\": [\"18055543\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The transcription factor Egr-1 directly regulates PTPRZ1 (phosphacan) expression in astrocytes after ischemic injury: Egr-1 binds to a site within the phosphacan promoter and transactivates its expression; Egr-1-deficient mice show reduced phosphacan RNA and protein after experimental stroke.\",\n      \"method\": \"Gain/loss-of-function in primary astrocytes, promoter-reporter assay, chromatin immunoprecipitation (ChIP), knockout mouse model, RT-PCR, Western blot\",\n      \"journal\": \"The American journal of pathology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — ChIP, promoter assay, and in vivo knockout validation together establish transcriptional mechanism\",\n      \"pmids\": [\"18556777\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Crystal structures of the carbonic anhydrase-like domain of PTPRZ show it interacts directly with the second and third Ig repeats of CNTN1; PTPRZ binds specifically CNTN1 (but not CNTN3/4/5/6), establishing binding specificity determined by the carbonic anhydrase-like domain.\",\n      \"method\": \"X-ray crystallography, direct binding assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with functional binding validation\",\n      \"pmids\": [\"20133774\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PTPRZ binds specifically to CNTN1 expressed at the surface of oligodendrocyte precursor cells (OPCs); this PTPRZ/CNTN1 complex inhibits OPC proliferation and promotes their differentiation into mature oligodendrocytes, as shown in PTPRZ-deficient mice.\",\n      \"method\": \"Cocrystal structure of PTPRZ carbonic anhydrase-like domain with CNTN1 Ig repeats, surface binding assays, glial cell population analysis in Ptprz-/- vs. wild-type mice\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure plus knockout mouse with defined cellular phenotype\",\n      \"pmids\": [\"21969550\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"RPTPζ/phosphacan (PTPRZ1) undergoes aberrant O-mannosyl glycosylation in the brain: it is a major substrate for POMGnT1-mediated O-mannosylation; in POMGnT1-knockout mice modeling muscle-eye-brain disease, RPTPζ/phosphacan shifts to lower molecular weight and loses HNK-1 epitopes.\",\n      \"method\": \"Western blot, immunoprecipitation, glycan epitope analysis in POMGnT1 knockout mouse brain\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — knockout mouse model with biochemical characterization demonstrating specific glycan modification\",\n      \"pmids\": [\"22728091\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Phosphacan/PTPRZ1 is identified as the major carrier of O-mannose-linked HNK-1 glycan in developing mouse brain; GlcAT-P specifically synthesizes O-linked HNK-1 onto phosphacan; the 6B4 monoclonal antibody epitope is O-mannose-linked HNK-1 on phosphacan, as shown in GlcAT-P-deficient mice.\",\n      \"method\": \"Mass spectrometric glycan analysis, GlcAT-P knockout mice, co-expression in cultured cells, immunoblot\",\n      \"journal\": \"Glycobiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mass spectrometry with knockout mouse validation and cell expression experiments\",\n      \"pmids\": [\"24352591\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PTPRZ1-MET (ZM) fusion transcripts arise from chromosomal translocation involving introns 3 or 8 of PTPRZ1 and intron 1 of MET in secondary glioblastomas; exogenous expression of ZM fusion in U87MG cells enhances cell migration and invasion.\",\n      \"method\": \"RNA-seq, RT-PCR, Sanger sequencing, genomic translocation analysis, cell migration/invasion assay after ZM overexpression\",\n      \"journal\": \"Genome research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — recurrent fusion identified by sequencing in multiple cohorts, functional overexpression assay with migration readout\",\n      \"pmids\": [\"25135958\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"ZM fusion proteins preserve wild-type MET processing and dimerization properties, and enhance MET phosphorylation in both HGF-dependent and HGF-independent manners, with increased MET mRNA expression induced by fusion with PTPRZ1 promoter.\",\n      \"method\": \"Western blot for phospho-MET, HGF stimulation assays, dimerization analysis, mRNA expression analysis in patient samples and transfected cells\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple biochemical assays in single study establishing fusion mechanism\",\n      \"pmids\": [\"25935522\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PTPRZ specifically dephosphorylates GIT1 at Tyr-554 in vitro and in HEK293T cells; this dephosphorylation promotes GIT1 association with paxillin and Hic-5; in Ptprz-deficient mice, GIT1 Tyr-554 phosphorylation is higher and paxillin binding is lower; cyclic phosphorylation-dephosphorylation at GIT1 Tyr-554 is critical for cell motility.\",\n      \"method\": \"In vitro phosphatase assay, site-directed mutagenesis of GIT1 Tyr-554, co-immunoprecipitation, Ptprz-/- mouse brain biochemistry, random motility/wound healing/Boyden chamber assays with GIT1 mutants\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro substrate assay with mutagenesis, in vivo knockout validation, and functional cell motility readout\",\n      \"pmids\": [\"25742295\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The chondroitin sulfate (CS) moiety of PTPRZ-A maintains it in a monomeric active (dephosphorylated-substrate) state by electrostatic repulsion between CS chains, preventing spontaneous clustering; pleiotrophin (PTN) binding induces receptor clustering/inactivation by neutralizing CS repulsion, thereby promoting OPC differentiation. CS removal by chondroitinase ABC similarly inactivates PTPRZ and promotes OPC differentiation.\",\n      \"method\": \"Surface receptor localization imaging (punctate vs. diffuse distribution), chondroitinase ABC treatment of OPCs, PTN ligand application, oligodendrocyte differentiation assay, Ptn-deficient mouse analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — mechanistic model tested with enzyme treatment, knockout mice, and imaging in single study\",\n      \"pmids\": [\"27445335\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Crystal structure of the PTPRZ catalytic domain was determined; SCB4380 binds stoichiometrically to the catalytic pocket and inhibits PTPRZ phosphatase activity; site-directed mutagenesis validated the docking-predicted binding mode; intracellular delivery of SCB4380 in C6 glioblastoma cells inhibits PTPRZ activity, suppresses migration and proliferation in vitro, and reduces tumor growth in vivo.\",\n      \"method\": \"X-ray crystallography, biochemical phosphatase assay, mass spectrometry, molecular docking, site-directed mutagenesis, liposome drug delivery, in vitro migration/proliferation assay, rat allograft tumor model\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with mutagenesis and in vivo functional validation\",\n      \"pmids\": [\"26857455\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TAMs secrete pleiotrophin (PTN) to activate PTPRZ1 signaling in glioma stem cells (GSCs); disrupting PTPRZ1 (shRNA or anti-PTPRZ1 antibody) abrogates GSC maintenance and tumorigenicity; silencing PTN in M2-like macrophages reduces their pro-tumorigenic activity; PTPRZ1 is preferentially expressed on GSCs.\",\n      \"method\": \"GSC co-implantation with M2 macrophages, shRNA knockdown, antibody blockade, neurosphere formation assay, in vivo tumor growth assay\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple loss-of-function approaches (shRNA + antibody) with in vivo tumor readout establishing paracrine signaling mechanism\",\n      \"pmids\": [\"28569747\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PTPRZ knockdown in C6 and U251 glioblastoma sphere-forming cells alters expression of stem cell transcription factors SOX2, OLIG2, and POU3F2 and decreases sphere-forming ability; the small-molecule allosteric inhibitor NAZ2329 reduces SOX2 expression and sphere-forming ability, and slows tumor growth in xenograft model when combined with temozolomide.\",\n      \"method\": \"Stable PTPRZ shRNA knockdown, small-molecule inhibitor (NAZ2329) treatment, sphere-forming assay, Western blot for transcription factors, C6 xenograft mouse model\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic knockdown and pharmacological inhibition with in vivo tumor model\",\n      \"pmids\": [\"28717188\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PTPRZ dephosphorylates AFAP1L2 at tyrosine residues in vitro and in HEK293T cells; PTN-PTPRZ signaling enhances phosphorylation of AFAP1L2, AKT, and mTOR in OPC-like cells to activate the PI3K-AKT pathway for OPC differentiation; catalytically inactive PTPRZ knock-in mice (CS mutation) show higher AFAP1L2/AKT/mTOR phosphorylation and accelerated OPC differentiation and remyelination.\",\n      \"method\": \"In vitro phosphatase assay with AFAP1L2 substrate, HEK293T cell transfection, PTN stimulation of OL1 cells, PTPRZ catalytic dead knock-in mouse (Cys-to-Ser), cuprizone demyelination model, Western blot for phosphoproteins\",\n      \"journal\": \"Glia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro substrate assay combined with knock-in mouse and demyelination model\",\n      \"pmids\": [\"30667096\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"RPTPζ/PTPRZ1 is required for perineuronal net (PNN) reticulated structure: in Ptprz1-/- mice, PNNs lose their reticular lattice and form puncta, phenocopying tenascin-R knockout; RPTPζ mediates one of two distinct modes of PNN component anchoring to the neuronal surface (the other requiring hyaluronan).\",\n      \"method\": \"Ptprz1-/- mouse analysis, immunostaining of PNN components, biochemical fractionation, neuronal culture experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — knockout mouse with defined structural phenotype and biochemical analysis\",\n      \"pmids\": [\"31822561\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Ptprz-knockout mice lacking all three isoforms show increased exploratory activity, deficits in spatial and contextual learning, and reduced responses to methamphetamine including reduced methamphetamine-evoked dopamine release in nucleus accumbens; phosphatase activity of PTPRZ receptor isoforms (CS mutant mice) is specifically required for dopaminergic regulation, while the extracellular region (including secretory isoform) mediates behavioral responses to novelty and aversive memory.\",\n      \"method\": \"Behavioral testing (open field, inhibitory avoidance), Ptprz-KO and knock-in mouse lines (CS catalytic dead, ΔD2 domain deletion), microdialysis for dopamine measurement\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple genetic mouse models with domain-specific behavioral and neurochemical readouts\",\n      \"pmids\": [\"31194769\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"GlcNAc6ST3 (encoded by Chst5, expressed in oligodendrocytes in adult brain) is a major keratan sulfate sulfotransferase for PTPRZ1; a KS-modified isoform of PTPRZ1 is a major R-10G-reactive KS proteoglycan associated with perineuronal nets in adult brain.\",\n      \"method\": \"Immunostaining with R-10G anti-KS antibody, Chst5-specific in situ hybridization, mass spectrometry-based proteoglycan identification, adult visual cortex analysis\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — enzyme identification with biochemical proteoglycan characterization in single study\",\n      \"pmids\": [\"30867513\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"ZM fusion protein activates MET kinase in a ligand-independent manner, attributed to a coiled-coil motif from the PTPRZ1 fusion partner that promotes dimerization/activation of the MET extracellular domain; ZM-positive clinical specimens show hyperactivation of MET signaling.\",\n      \"method\": \"3D structural prediction, coiled-coil motif analysis, cell line experiments with ZM expression, phospho-MET analysis in patient specimens\",\n      \"journal\": \"CNS neuroscience & therapeutics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — structural prediction with supporting cell line and clinical data; single study\",\n      \"pmids\": [\"33645009\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"RPTPζ/PTPRZ1 ectodomain forms direct protein-protein complexes with tenascin-R and tenascin-C; structural basis for these interactions was determined; mutations at the RPTPζ-TNR interface impair PNN formation in dissociated neuronal cultures; TNR is absent from net structures in Ptprz1-/- neuronal cultures.\",\n      \"method\": \"Structural determination of PTPRZ1 ectodomain-TNR complex, binding assays, Ptprz1-/- neuronal cultures, site-directed mutagenesis at interface residues, immunostaining of PNN components\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — structure with mutagenesis and knockout culture validation\",\n      \"pmids\": [\"37356715\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PTPRZ1 deletion or pharmacological inhibition of its phosphatase activity in endothelial cells activates c-Met and Akt kinase, increasing angiogenesis; PTPRZ1 mediates c-Met activation by VEGFA165 and pleiotrophin in endothelial cells, and this effect is abolished by the c-Met inhibitor crizotinib; Ptprz1-/- mice show enhanced LUAD growth and lung angiogenesis.\",\n      \"method\": \"Ptprz1-/- mouse model, lung microvascular endothelial cell isolation, PTPRZ1 pharmacological inhibitor, Western blot for c-Met/Akt phosphorylation, in vitro angiogenesis assay, LUAD urethane model, crizotinib rescue experiment\",\n      \"journal\": \"International journal of cancer\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic and pharmacological loss-of-function with in vivo tumor model and rescue experiment\",\n      \"pmids\": [\"37260355\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PTPRZ1-MET (ZM) fusion in GSCs activates MET-STAT3-ISG20 axis; ZM-positive GSCs secrete ISG20 extracellularly to recruit macrophages and drive their polarization toward an immunosuppressive M2-like phenotype, thereby promoting tumor progression.\",\n      \"method\": \"RNA-seq of sGBM patient tissues, GSC sphere cultures with ZM, ISG20 knockdown/overexpression, macrophage polarization assays, conditioned medium experiments\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pathway identification with functional knockdown and macrophage polarization readout in single study\",\n      \"pmids\": [\"38685521\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Curcumin directly interacts with PTPRZ1 to maintain its enzymatic phosphatase activity, which in turn regulates phosphorylation of the m6A-reader YTHDF2; this PTPRZ1-YTHDF2 axis modulates expression of inflammatory genes to reduce microglial inflammatory responses.\",\n      \"method\": \"Binding assay of curcumin with PTPRZ1, phosphatase activity assay, phosphorylation analysis of YTHDF2, gene expression analysis, microglial inflammatory assay\",\n      \"journal\": \"Advanced science (Weinheim, Baden-Wurttemberg, Germany)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — enzymatic activity maintained by curcumin with downstream phosphorylation readout; single study\",\n      \"pmids\": [\"39921492\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PTPRZ1 encodes a receptor-type protein tyrosine phosphatase whose extracellular domain (phosphacan) functions as a chondroitin sulfate proteoglycan that binds pleiotrophin, midkine, tenascins, neural cell adhesion molecules (L1/Ng-CAM, N-CAM, TAG-1/contactin-1), and FGF-2 to regulate neurite outgrowth, cell adhesion, and oligodendrocyte precursor differentiation; its negatively charged chondroitin sulfate chains keep the receptor in a monomeric active state until pleiotrophin binding induces clustering and receptor inactivation, activating the AFAP1L2-PI3K-AKT pathway to promote OPC differentiation; the intracellular phosphatase domain dephosphorylates substrates including GIT1 (Tyr-554), AFAP1L2, ALK, and TrkA to regulate cell motility, dopaminergic signaling, and chemoresistance, while the PTPRZ1-MET fusion activates MET kinase in a ligand-independent, coiled-coil-mediated manner to drive glioma progression.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PTPRZ1 encodes a receptor-type protein tyrosine phosphatase that functions as a major chondroitin sulfate proteoglycan of the central nervous system, regulating neural cell adhesion, neurite outgrowth, oligodendrocyte precursor cell (OPC) differentiation, perineuronal net assembly, and dopaminergic signaling. Its extracellular domain (shed as phosphacan) binds pleiotrophin, midkine, tenascins (C and R), neural cell adhesion molecules (N-CAM, L1/Ng-CAM, TAG-1/contactin-1), and FGF-2 through distinct glycan- and core-protein-mediated interactions, with chondroitin sulfate chains maintaining the receptor in a monomeric active state via electrostatic repulsion until pleiotrophin binding neutralizes this repulsion, induces receptor clustering/inactivation, and activates the AFAP1L2–PI3K–AKT pathway to promote OPC differentiation and remyelination [PMID:27445335, PMID:30667096, PMID:7528221, PMID:8702927]. The intracellular phosphatase domain dephosphorylates substrates including GIT1 at Tyr-554 and AFAP1L2 to regulate cell motility and myelination, while PTPRZ1 interactions with tenascin-R are structurally required for perineuronal net lattice formation [PMID:25742295, PMID:31822561, PMID:37356715]. Oncogenic PTPRZ1-MET fusion transcripts arising from chromosomal translocation in glioblastoma activate MET kinase in a ligand-independent, coiled-coil-mediated manner, driving glioma stem cell maintenance, migration, and immunosuppressive macrophage polarization [PMID:25135958, PMID:33645009, PMID:38685521].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"Establishing PTPRZ1's molecular identity: phosphacan was shown to be the secreted extracellular domain splice variant of receptor-type phosphatase RPTPζ/β, with an N-terminal carbonic anhydrase-like domain, resolving whether the abundant brain proteoglycan was related to a transmembrane signaling receptor.\",\n      \"evidence\": \"cDNA cloning and peptide sequencing of phosphacan showing 76% identity to RPTPζ/β extracellular domain\",\n      \"pmids\": [\"7511813\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length transmembrane isoform function not yet tested\", \"Relationship between secreted and transmembrane isoforms in vivo unclear\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Defining the extracellular ligand repertoire: phosphacan was found to bind N-CAM, Ng-CAM/L1, and tenascin-C with high affinity via its core glycoprotein (not CS chains), and to inhibit neurite outgrowth on Ng-CAM substrates, establishing PTPRZ1 as a multivalent neural adhesion regulator.\",\n      \"evidence\": \"Radioligand binding, Scatchard analysis, chondroitinase treatment, neurite outgrowth assays on coated substrates\",\n      \"pmids\": [\"7528221\", \"7512960\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signaling consequences of these interactions on intracellular phosphatase activity unknown\", \"In vivo relevance of individual ligand interactions not tested\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Identifying pleiotrophin as a key regulatory ligand: pleiotrophin/HB-GAM bound phosphacan with sub-nanomolar affinity predominantly through chondroitin sulfate chains, and antibody blockade showed this interaction was required for pleiotrophin-induced neurite outgrowth, establishing the ligand–receptor pair central to PTPRZ1 biology.\",\n      \"evidence\": \"Affinity chromatography, Scatchard analysis, chondroitinase digestion, heparin competition, neurite outgrowth antibody blockade in cortical neurons\",\n      \"pmids\": [\"8702927\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether pleiotrophin binding regulates phosphatase activity was unknown\", \"In vivo requirement not yet tested in knockout\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Resolving glycan versus core protein contributions to distinct ligands: TAG-1/contactin binding was ~70% CS-mediated while N-CAM/L1 binding was core-protein-mediated, and asparagine-linked complex oligosaccharides at specific sites (Asn-232, Asn-381) were identified as the core determinants for CAM and tenascin interactions.\",\n      \"evidence\": \"Chondroitinase treatment, N-glycosidase F/Endo H digestion, tryptic fragment binding assays\",\n      \"pmids\": [\"8663515\", \"7559574\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of selective glycan recognition not resolved\", \"Functional consequence of glycan heterogeneity on signaling not addressed\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Expanding the ligand network to include tenascin-R, amphoterin, and FGF-2: phosphacan core protein bound tenascin-R and FGF-2 with nanomolar affinity, with FGF-2 binding potentiating its mitogenic activity comparably to heparin, broadening PTPRZ1's role beyond adhesion to growth factor co-receptor function.\",\n      \"evidence\": \"Radioligand binding with chondroitinase treatment, Scatchard analysis, thymidine incorporation mitogenesis assay\",\n      \"pmids\": [\"9507007\", \"9705269\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether FGF-2 co-receptor activity operates in CNS cells specifically was not tested\", \"Signaling downstream of PTPRZ1-FGF-2 not characterized\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Demonstrating that CS sulfation pattern developmentally tunes ligand affinity: adult brain phosphacan carrying D-unit disaccharides bound pleiotrophin ~5-fold more tightly than postnatal phosphacan lacking D-units, providing a glycan-code mechanism for age-dependent signaling regulation.\",\n      \"evidence\": \"Surface plasmon resonance with chondroitinase digestion and immunochemical CS disaccharide profiling\",\n      \"pmids\": [\"12840014\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Enzymes responsible for D-unit synthesis on PTPRZ1 not identified\", \"Functional consequence of age-dependent affinity shift on OPC biology not tested\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Structural determination of the carbonic anhydrase-like domain revealed the molecular basis of CNTN1-selective binding: crystal structures showed direct interaction with Ig repeats 2–3 of CNTN1 but not other contactins, resolving how PTPRZ1 achieves ligand specificity.\",\n      \"evidence\": \"X-ray crystallography of PTPRZ1 CA domain, direct binding assays with contactin family members\",\n      \"pmids\": [\"20133774\", \"21969550\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CS chains modulate CNTN1 interaction in vivo was unclear\", \"Full ectodomain structure not resolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Connecting PTPRZ1–CNTN1 binding to oligodendrocyte biology: PTPRZ1 binds CNTN1 on OPC surfaces and this complex inhibits OPC proliferation while promoting differentiation, with Ptprz-deficient mice showing altered glial populations.\",\n      \"evidence\": \"Co-crystal structure, surface binding assays, Ptprz−/− mouse glial cell analysis\",\n      \"pmids\": [\"21969550\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Intracellular phosphatase substrates mediating OPC differentiation unknown at this point\", \"Whether CNTN1 interaction affects phosphatase activity not tested\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identifying the first specific intracellular substrate: PTPRZ dephosphorylates GIT1 at Tyr-554, regulating its association with paxillin/Hic-5 and cell motility, validated by elevated GIT1 phosphorylation in Ptprz-knockout mouse brain.\",\n      \"evidence\": \"In vitro phosphatase assay, Tyr-554 mutagenesis, co-immunoprecipitation, Ptprz−/− mouse biochemistry, wound healing and Boyden chamber assays\",\n      \"pmids\": [\"25742295\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether GIT1 dephosphorylation mediates PTPRZ1's neural functions not tested\", \"Full substrate repertoire unknown\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Elucidating the CS-mediated autoinhibition mechanism: chondroitin sulfate chains maintain PTPRZ in a monomeric active state through electrostatic repulsion; pleiotrophin neutralizes this repulsion to induce clustering and phosphatase inactivation, thereby promoting OPC differentiation — a unified model linking ligand binding to phosphatase regulation.\",\n      \"evidence\": \"Receptor distribution imaging, chondroitinase treatment of OPCs, pleiotrophin stimulation, OPC differentiation assay, Ptn−/− mouse\",\n      \"pmids\": [\"27445335\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct biophysical measurement of clustering (e.g., FRET, single-molecule) not provided\", \"Whether other ligands similarly cluster the receptor unknown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identifying the downstream signaling axis for OPC differentiation: PTPRZ dephosphorylates AFAP1L2, and pleiotrophin-induced receptor inactivation activates the AFAP1L2–PI3K–AKT–mTOR pathway; catalytically inactive PTPRZ knock-in mice show accelerated OPC differentiation and remyelination after cuprizone demyelination.\",\n      \"evidence\": \"In vitro phosphatase assay, PTN stimulation in OL1 cells, PTPRZ catalytic-dead knock-in mouse, cuprizone demyelination model\",\n      \"pmids\": [\"30667096\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether AFAP1L2 is the sole mediator or acts with other substrates not resolved\", \"Therapeutic potential of PTPRZ inhibition for remyelination not tested in disease models beyond cuprizone\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Establishing PTPRZ1's structural role in perineuronal nets: Ptprz1-knockout mice lose the reticular PNN lattice phenocopying tenascin-R loss, demonstrating that PTPRZ1 anchors PNN components to neuronal surfaces via one of two distinct mechanisms.\",\n      \"evidence\": \"Ptprz1−/− mouse immunostaining of PNN components, biochemical fractionation, neuronal cultures\",\n      \"pmids\": [\"31822561\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular details of how PTPRZ1 organizes PNN lattice versus punctate structures unclear\", \"Functional consequences for synaptic plasticity not directly measured\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Dissecting phosphatase-dependent versus ectodomain-dependent behavioral functions: using domain-specific knock-in mice, phosphatase activity was shown to be required for dopaminergic regulation (methamphetamine-evoked DA release), while the extracellular domain mediates behavioral responses to novelty and aversive memory.\",\n      \"evidence\": \"Ptprz-KO, catalytic-dead, and ΔD2 knock-in mice; behavioral testing; nucleus accumbens microdialysis\",\n      \"pmids\": [\"31194769\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific phosphatase substrates mediating dopaminergic regulation not identified\", \"Neural circuit basis of behavioral phenotypes not mapped\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Discovery of oncogenic PTPRZ1-MET fusion: recurrent PTPRZ1-MET translocation-derived fusions were identified in secondary glioblastomas and shown to enhance glioma cell migration and invasion upon expression.\",\n      \"evidence\": \"RNA-seq and genomic analysis of glioblastoma cohorts, RT-PCR validation, Sanger sequencing, migration/invasion assay in U87MG cells\",\n      \"pmids\": [\"25135958\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of constitutive MET activation by fusion not resolved\", \"In vivo tumorigenicity of fusion not demonstrated\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Mechanism of fusion-driven MET activation clarified: a coiled-coil motif from the PTPRZ1 portion of ZM fusion was proposed to mediate ligand-independent dimerization and constitutive MET kinase activation.\",\n      \"evidence\": \"3D structural prediction, coiled-coil analysis, phospho-MET in ZM-expressing cells and clinical specimens\",\n      \"pmids\": [\"33645009\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Coiled-coil model based on prediction, not experimentally validated structure\", \"Mutagenesis of coiled-coil not performed\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Structural basis for PNN assembly resolved: the PTPRZ1 ectodomain–tenascin-R complex structure was determined, and interface mutations disrupted PNN formation in neuronal cultures, directly linking structural interactions to extracellular matrix organization.\",\n      \"evidence\": \"Structural determination of PTPRZ1-TNR complex, site-directed mutagenesis, Ptprz1−/− neuronal culture PNN analysis\",\n      \"pmids\": [\"37356715\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo validation of interface mutations not performed\", \"Whether tenascin-C binding uses the same or different interface not resolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"ZM fusion drives immunosuppressive tumor microenvironment: PTPRZ1-MET fusion in GSCs activates MET–STAT3–ISG20 signaling, with secreted ISG20 recruiting macrophages and polarizing them to immunosuppressive M2 phenotype.\",\n      \"evidence\": \"RNA-seq of sGBM tissues, ISG20 knockdown/overexpression, macrophage polarization assays, conditioned medium experiments\",\n      \"pmids\": [\"38685521\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo immune phenotype of ZM-positive tumors not validated in immunocompetent models\", \"Whether ISG20 secretion is the dominant immunosuppressive mechanism unclear\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the full substrate repertoire of PTPRZ1 phosphatase in neural and non-neural contexts, the structural basis of CS-mediated receptor clustering upon pleiotrophin binding, whether pharmacological PTPRZ1 inhibition can promote remyelination in human demyelinating disease, and the therapeutic vulnerability of PTPRZ1-MET fusion-driven gliomas to targeted MET inhibition in clinical settings.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Complete phosphatase substrate repertoire not systematically identified\", \"No high-resolution structure of full-length transmembrane PTPRZ1\", \"Clinical translation of PTPRZ1 inhibitors for remyelination or glioma therapy untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [21, 26, 23, 34]},\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [0, 2, 6]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [22, 32]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [16, 22, 27]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [1, 4, 8, 9, 11]},\n      {\"term_id\": \"GO:0031012\", \"supporting_discovery_ids\": [27, 31]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [22, 26, 32]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [16, 26]},\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [27, 31]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [28]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [19, 24, 25, 33]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"PTN\",\n      \"CNTN1\",\n      \"GIT1\",\n      \"AFAP1L2\",\n      \"TNC\",\n      \"TNR\",\n      \"NCAM1\",\n      \"L1CAM\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}