{"gene":"PTPRF","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":1990,"finding":"The first of the two intracellular PTPase-like domains of LAR has catalytic enzyme activity, while the second domain lacks detectable catalytic activity. A single conserved cysteine residue in domain 1 is absolutely required for activity; substitution at this position abolished activity. Sequences in domain 2 influence substrate specificity.","method":"Deletion and point mutations in cytoplasmic region; in vitro phosphatase activity assays with multiple substrates","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro enzymatic assay combined with systematic mutagenesis of both domains, replicated across multiple substrates","pmids":["1695146"],"is_preprint":false},{"year":1991,"finding":"The cytoplasmic domain of rat LAR expressed in bacteria has protein tyrosine phosphatase activity. Cys-1522 in domain 1 is the catalytic cysteine; C1522S mutation causes >99% loss of activity. A covalent phosphoenzyme intermediate was trapped with 32P-labeled substrate, establishing the catalytic mechanism. The inactive C1522S mutant could be phosphorylated in vitro by PKC and v-abl tyrosine kinase.","method":"Bacterial expression, purification, site-directed mutagenesis, phosphoenzyme intermediate trapping by SDS-PAGE autoradiography, in vitro kinase assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted in vitro with mutagenesis and mechanistic intermediate trapping in a single rigorous study","pmids":["1918076"],"is_preprint":false},{"year":1991,"finding":"Temperature-sensitive and thermostable missense mutations in LAR domain 1 cluster between amino acid positions 1329–1407, identifying a structurally critical region for enzyme folding and activity. A second-site revertant (C1446-Y) suppresses multiple temperature-sensitive mutations, suggesting structural interactions within this region.","method":"Bacterial expression of LAR domain 1; hydroxylamine and MNNG mutagenesis; biochemical characterization of mutants at permissive and restrictive temperatures; second-site reversion analysis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic characterization of multiple mutants, single lab","pmids":["1645351"],"is_preprint":false},{"year":1992,"finding":"LAR is expressed on the cell surface as a complex of two non-covalently associated subunits (E-subunit ~150 kDa extracellular; P-subunit ~85 kDa transmembrane+cytoplasmic) derived from a proprotein. Proprotein cleavage occurs intracellularly at a paired basic amino acid site by a subtilisin-like endoprotease; mutation of key arginine residues blocks cleavage. The E-subunit is shed from the cell surface during cell growth, providing a mechanism to regulate LAR phosphatase function.","method":"Mutational analysis of cleavage site; biochemical characterization of subunit expression; cell surface shedding assays","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — mutagenesis identifying specific residues required for cleavage, combined with biochemical demonstration of shedding and subunit structure","pmids":["1547787"],"is_preprint":false},{"year":1992,"finding":"The E. coli-expressed LAR two-domain fragment (D1D2) has almost identical specific activity to the single domain (D1) fragment, confirming a single functional active site in domain 1. 18O exchange from [18O4]-inorganic phosphate into water and 32P-phosphoenzyme labeling established a phosphoenzyme intermediate mechanism. Polycationic polypeptides stimulate D1D2 but not D1 PTPase activity via domain 2, indicating domain 2 has a regulatory function.","method":"E. coli expression and purification; isotope exchange assay (18O); phosphoenzyme intermediate labeling; substrate specificity comparison; polycation stimulation assay","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal mechanistic assays (isotope exchange, phosphoenzyme trapping, domain deletion) in single rigorous study","pmids":["1370625"],"is_preprint":false},{"year":1992,"finding":"Basic polypeptides stimulate the PTPase activity of LAR D1D2 but not D1 alone using peptide substrate Raytide, indicating that domain 2 has a regulatory function on domain 1 catalytic activity. Polypeptides containing high proportions of tyrosine are inhibitory to LAR and related phosphatases.","method":"Purified recombinant LAR fragments from E. coli; peptide substrate assays with modulatory compounds","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro biochemical assay with purified domains, single lab, two orthogonal approaches (stimulation and inhibition)","pmids":["1318316"],"is_preprint":false},{"year":1994,"finding":"Functional regions for LAR proprotein processing, subunit association, and shedding were mapped by scanning mutagenesis. Three residues (two in a penta-arginine sequence and one C-terminal to the cleavage site) are essential for proprotein cleavage. Several non-contiguous residues in the P-subunit ectodomain are required for subunit association. Shedding involves a second proteolytic cleavage within the P-subunit ectodomain near the transmembrane peptide.","method":"Site-directed and scanning mutagenesis; biochemical analysis of processing, subunit association, and shedding in transfected cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — systematic mutagenesis identifying specific residues for each processing step, multiple orthogonal readouts","pmids":["8089133"],"is_preprint":false},{"year":1995,"finding":"LAR co-localizes with the novel cytoplasmic 160 kDa phosphoserine protein LIP.1 (LAR-interacting protein 1) at the ends of focal adhesions most proximal to the cell nucleus. LIP.1 binds specifically to the membrane-distal D2 PTPase domain of LAR and appears to localize LAR to focal adhesions, implicating this complex in regulation of focal adhesion disassembly.","method":"Identification of LIP.1 by interaction-trap assay; co-localization by immunofluorescence; domain-binding analysis","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — binding partner identified by interaction trap, co-localization demonstrated, domain mapped, functional context established","pmids":["7796809"],"is_preprint":false},{"year":1995,"finding":"Antisense-mediated suppression of LAR in McA-RH7777 hepatoma cells (63% reduction) increased insulin-dependent insulin receptor autophosphorylation (~150%), receptor tyrosine kinase activity (35%), and insulin-dependent PI3-kinase activity (350%), establishing LAR as a negative regulator of insulin receptor signaling in intact cells.","method":"Antisense RNA expression in hepatoma cells; insulin receptor autophosphorylation and kinase assays; PI3-kinase activity assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — specific loss-of-function with defined molecular phenotype at multiple pathway nodes, consistent across insulin concentrations","pmids":["7852302"],"is_preprint":false},{"year":1995,"finding":"LAR, PTPδ, and PTPσ all interact with LIP.1 via their membrane-distal phosphatase domains. All three phosphatases exhibit similar in vitro PTPase activities and share alternative splicing of mini-exons, establishing them as a subfamily with conserved structure, activity, and interacting proteins.","method":"Cloning; in vitro PTPase activity assays; LIP.1 binding/interaction analysis across family members","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical characterization of multiple family members, interaction with LIP.1 demonstrated, single study","pmids":["8524829"],"is_preprint":false},{"year":1995,"finding":"Overexpression of full-length LAR in McA-RH7777 hepatoma cells (2.4-fold increase) reduced insulin receptor autophosphorylation 40% in intact cells, decreased IRS-1 and Shc tyrosine phosphorylation, and reduced IRS-1-associated PI3-kinase activity to 47% of control. Overexpression of the cytoplasmic domain alone (cytosolic, not membrane-localized) had no significant effect, indicating transmembrane localization is required for LAR to act on the insulin receptor.","method":"Stable transfection with full-length vs. cytoplasmic-only LAR constructs; insulin receptor autophosphorylation; substrate phosphorylation; kinase assays; cell fractionation","journal":"Molecular endocrinology","confidence":"High","confidence_rationale":"Tier 2 / Strong — gain-of-function with domain-specific controls (full-length vs. cytoplasmic), multiple orthogonal readouts, requirement for membrane localization established","pmids":["8732688"],"is_preprint":false},{"year":1996,"finding":"Trio, a 2861-amino acid multidomain protein, was identified as a LAR-interacting protein via the interaction-trap assay. Trio contains two GEF domains (one Rac-specific, one Rho-specific) and a serine/threonine kinase domain. Trio appears phosphorylated only on serine residues, suggesting it is not a LAR substrate but forms a signaling complex with LAR at focal adhesions.","method":"Interaction-trap (yeast two-hybrid) assay; GEF activity assays for Rac and Rho specificity; phosphorylation analysis; co-localization at focal adhesions","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — binding partner identified by two-hybrid and confirmed biochemically, GEF activities directly demonstrated, multiple orthogonal methods","pmids":["8643598"],"is_preprint":false},{"year":1996,"finding":"Antisense suppression of LAR in McA-RH7777 cells increased EGF receptor autophosphorylation by >300%, HGF receptor autophosphorylation by >250%, downstream IRS-1 and Shc phosphorylation, MAP kinase activation, and PI3-kinase activation in response to all three growth factors, demonstrating LAR modulates signaling by multiple receptor tyrosine kinases.","method":"Antisense RNA suppression; receptor autophosphorylation assays; substrate phosphorylation; MAP kinase and PI3-kinase activity assays for EGF, HGF, and insulin receptors","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function across three RTK pathways with multiple readouts, consistent results","pmids":["8557682"],"is_preprint":false},{"year":1997,"finding":"LAR co-immunoprecipitates with the insulin receptor in intact CHO cells overexpressing both proteins; up to 11.8% of LAR co-precipitates with the insulin receptor. The association was increased by cross-linking and 3.9-fold by insulin treatment. In insulin-stimulated rat liver, LAR was enriched in endosomes with the insulin receptor, and LAR-neutralizing antibodies decreased endosomal insulin receptor dephosphorylation by 28%, demonstrating a direct physical and functional association.","method":"Co-immunoprecipitation; chemical cross-linking; subcellular fractionation of rat liver; in situ endosomal dephosphorylation with neutralizing antibodies","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP, endosomal co-localization in vivo, neutralizing antibody functional assay — multiple orthogonal approaches","pmids":["8995282"],"is_preprint":false},{"year":1997,"finding":"LAR and PTPσ undergo induced proteolytic processing (shedding of extracellular domains) upon treatment with calcium ionophore A23187 or phorbol ester TPA; TPA-induced LAR processing required PKCα overexpression in 293 cells. Both phosphatases localize preferentially to adherens junctions and desmosomes, co-localizing with plakoglobin. Direct association of plakoglobin and β-catenin with the intracellular domain of LAR was demonstrated in vitro. After ectodomain shedding, catalytically active intracellular portions are internalized away from cell-cell contacts.","method":"Inducible proteolytic processing; confocal microscopy; in vitro binding assay for β-catenin and plakoglobin; PKCα overexpression; inhibitor studies; cell fractionation","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple methods: in vitro binding, localization by confocal, inducible processing with kinase requirement identified","pmids":["9245795"],"is_preprint":false},{"year":1997,"finding":"LAR antisense suppression in McA-RH7777 cells prolonged insulin receptor dephosphorylation 2.6-fold (t½ increased from 34 to 87 s), providing direct kinetic evidence that LAR is a major physiological regulator of insulin receptor dephosphorylation in situ. EGF receptor dephosphorylation was also prolonged in LAR-deficient cells.","method":"Antisense RNA suppression; kinetic dephosphorylation assay following acid elution of surface-bound insulin; EGF receptor dephosphorylation assay","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — specific loss-of-function with kinetic mechanistic readout, consistent with multiple prior studies","pmids":["9207225"],"is_preprint":false},{"year":1997,"finding":"LAR deficiency in transgenic mice (gene trap) results in reduced size of basal forebrain cholinergic neurons and markedly decreased cholinergic innervation of the dentate gyrus, establishing LAR as required for formation and/or maintenance of cholinergic neuronal networks in mammals.","method":"Gene trap transgenic mice with reduced LAR expression; histomorphometry of basal forebrain cholinergic neurons; immunohistochemistry of hippocampal cholinergic innervation","journal":"Journal of neuroscience research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo loss-of-function with defined neuroanatomical phenotype, single lab","pmids":["9039657"],"is_preprint":false},{"year":1997,"finding":"Knockout mice lacking both LAR phosphatase domains (LAR−/−) develop impaired terminal differentiation of mammary gland alveoli during late pregnancy, failing to switch to a lactational state and showing rapid postpartum involution. LAR expression peaks around day 16 of gestation in wild-type mice, establishing LAR-mediated signaling as required for mammary gland development and lactation.","method":"Gene targeting in mouse ES cells; histological analysis of mammary gland; Northern blot for LAR expression during pregnancy; neonatal survival assessment","journal":"Developmental biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean knockout with specific tissue phenotype and developmental expression correlation, multiple readouts","pmids":["9245518"],"is_preprint":false},{"year":1998,"finding":"Overexpression of wild-type LAR (but not a truncated extracellular-only form) in mammalian cells activates the caspase pathway and induces p53-independent apoptosis, establishing a role for LAR's phosphatase-active intracellular region in cell-death control.","method":"Inducible expression system; caspase activity assays; cell viability assays comparing full-length vs. extracellular-only truncation mutant","journal":"Current biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — inducible expression with domain-specific control, caspase pathway activation measured, single lab","pmids":["9501065"],"is_preprint":false},{"year":1998,"finding":"Alpha-liprins (a family of seven LAR-interacting proteins) bind to the membrane-distal phosphatase domains of LAR family members via their C-terminal non-coiled coil regions; beta-liprins interact with alpha-liprins. Co-expression of liprin-α2 alters LAR cellular localization and induces LAR clustering, establishing liprins as regulators of LAR localization at specific plasma membrane sites.","method":"Yeast two-hybrid and biochemical binding assays; co-expression localization studies by immunofluorescence; family-wide interaction mapping","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — binding demonstrated biochemically and functionally confirmed by co-expression localization changes; multiple family members tested","pmids":["9624153"],"is_preprint":false},{"year":1998,"finding":"LAR-deficient mice exhibit significantly lower fasting plasma insulin and glucose and a reduced rate of hepatic glucose production, but display paradoxical resistance to insulin-stimulated glucose disposal and a 47% reduction in insulin-stimulated PI3-kinase activity in liver, demonstrating LAR has a physiological role in insulin action and glucose homeostasis in vivo.","method":"Insertional mutagenesis knockout mice; euglycemic clamp studies; hepatic PI3-kinase activity; glucose disposal measurements","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo knockout with multiple metabolic phenotypic readouts and defined post-receptor signaling defect","pmids":["9519761"],"is_preprint":false},{"year":1999,"finding":"LAR overexpression specifically decreases the steady-state level and tyrosine phosphorylation of p130Cas by dephosphorylating it, reducing its protein stability. This is blocked by tyrosine phosphatase inhibitors and phosphatase-domain deletion mutants of LAR. LAR preferentially dephosphorylates p130Cas in vitro. LAR and p130Cas co-localize along stress fibers and at focal adhesions. Restoring p130Cas levels alleviates LAR-induced apoptosis, establishing p130Cas as an in vivo substrate of LAR mediating apoptosis.","method":"Overexpression of LAR and phosphatase-dead mutants; in vitro phosphatase assay; immunofluorescence co-localization; p130Cas rescue experiment; pharmacological inhibition","journal":"Genes to cells","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro dephosphorylation assay, in vivo substrate identification with multiple controls, rescue experiment, co-localization","pmids":["10320483"],"is_preprint":false},{"year":1999,"finding":"LAR is irreversibly inactivated by peroxynitrite (IC50 ≤0.9 µM) with a bimolecular rate constant of 2.3 × 10^7 M^−1 s^−1, among the fastest reactions of peroxynitrite with biological molecules. The inactivation was essentially irreversible (DTT restores <10% activity), consistent with oxidation of the essential active-site thiolate. Nitric oxide and S-nitrosoglutathione caused only partial, reversible inhibition.","method":"In vitro phosphatase activity assays; competition kinetics with cysteine; treatment with peroxynitrite, NO donors, and GSNO; DTT reversal experiments","journal":"Archives of biochemistry and biophysics","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinetic assays with multiple reagents, quantitative rate constants determined, single lab","pmids":["10486138"],"is_preprint":false},{"year":2000,"finding":"Stable antisense-mediated knockdown of LAR in PC12 cells results in a two-fold increase specifically in NGF-induced (but not FGF-induced) neurite outgrowth and a two- to three-fold decrease in serum-deprivation-induced cell death, demonstrating that endogenous LAR negatively regulates neurotrophin responses and promotes cell death.","method":"Stable antisense transfection; neurite outgrowth quantification; serum deprivation cell death assay; comparison of NGF vs. FGF responses","journal":"Journal of neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — specific loss-of-function with defined molecular readouts, ligand specificity established, single lab","pmids":["10699984"],"is_preprint":false},{"year":2001,"finding":"Overexpression of LAR specifically in muscle of transgenic mice causes whole-body insulin resistance: fasting insulin elevated 2.5-fold, glucose disposal reduced 39–50%, IRS-2 phosphorylation reduced 62%, and PI3-kinase associated with phosphotyrosine, IRS-1, and IRS-2 reduced 34–57%. Normal insulin receptor and IRS-1 phosphorylation was observed, suggesting dephosphorylation of specific IRS protein regulatory phosphotyrosines as the mechanism.","method":"Muscle-specific transgenic mice overexpressing human LAR; euglycemic clamp; insulin receptor and IRS phosphorylation; PI3-kinase activity assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — tissue-specific gain-of-function in vivo with multiple metabolic and signaling readouts identifying IRS proteins as the mechanistic target","pmids":["11309481"],"is_preprint":false},{"year":2001,"finding":"Domain 2 of LAR mediates substrate (insulin receptor) association (C1813S mutation weakened association), while domain 1 catalytic activity (C1522S mutation) is required for dephosphorylation. The extracellular domains of both LAR and insulin receptor also contribute to their association. LAR is phosphorylated by insulin receptor tyrosine kinase and autodephosphorylates via domain 1.","method":"Cysteine-to-serine active-site mutants of each domain; co-immunoprecipitation with insulin receptor; phosphorylation assays; domain deletion analysis","journal":"Molecular endocrinology","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — systematic domain mutagenesis with substrate co-IP, multiple domain combinations tested, identifies distinct roles for each domain","pmids":["11158333"],"is_preprint":false},{"year":2005,"finding":"LAR-RPTP is concentrated at mature excitatory synapses in hippocampal neurons. RNAi knockdown of LAR or dominant-negative disruption causes loss of excitatory synapses and dendritic spines, reduction of surface AMPA receptors, impaired dendritic targeting of the cadherin–β-catenin complex, and reduced mEPSC amplitude and frequency. β-catenin and GluR2/3 co-immunoprecipitate with liprin-α and GRIP from rat brain, establishing LAR as required for excitatory synapse development and AMPA receptor trafficking.","method":"RNAi knockdown; dominant-negative expression; immunofluorescence; electrophysiology (mEPSC recording); co-immunoprecipitation from brain extracts; surface receptor biotinylation","journal":"Nature neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal approaches (RNAi, dominant-negative, co-IP, electrophysiology), defined synaptic phenotypes, confirmed in rat brain","pmids":["15750591"],"is_preprint":false},{"year":2006,"finding":"Drosophila HSPGs Syndecan (Sdc) and Dallylike (Dlp) both bind at high affinity to the receptor tyrosine phosphatase LAR. Double mutant analysis showed LAR is required for actions of both HSPGs at the NMJ: Sdc promotes LAR-dependent presynaptic terminal growth, while Dlp inhibits LAR activity. These results establish HSPGs as extracellular ligands that differentially regulate LAR.","method":"High-affinity binding assays; Drosophila genetics with single and double mutants; NMJ morphological analysis; epistasis analysis","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct binding assays combined with in vivo epistasis in Drosophila, defining LAR-dependent vs. -independent phenotypes","pmids":["16476662"],"is_preprint":false},{"year":2006,"finding":"LAR associates with c-Met/HGF receptor specifically in confluent (contact-inhibited) hepatocytes. LAR activity and expression increase after HGF stimulation in confluent but not sparse cells. Purified LAR dephosphorylates tyrosine-phosphorylated c-Met in vitro. Antisense knockdown of LAR in confluent cells restores prolonged c-Met phosphorylation and mitogenic response, establishing LAR as mediating contact-inhibition of HGF/c-Met signaling via dephosphorylation.","method":"Co-immunoprecipitation; in vitro LAR phosphatase assay with c-Met substrate; antisense oligonucleotides; cell density-dependent signaling assays; kinase activity measurements","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro dephosphorylation assay, co-IP, antisense loss-of-function with defined phenotype, multiple methods in single study","pmids":["16415345"],"is_preprint":false},{"year":2006,"finding":"EGFR associates with LAR and induces proteolytic processing (cleavage) of the LAR P-subunit via an ERK1/2-dependent pathway. EGFR-induced LAR shedding is mediated by the metalloproteinase ADAM-17/TACE (established by TACE-knockout fibroblasts and dominant-negative TACE). Cleavage results in degradation of the catalytic LAR P-subunit and significantly reduced cellular phosphatase activity.","method":"EGFR overexpression and stimulation; TACE-knockout fibroblasts; dominant-negative TACE; metalloproteinase inhibitor (Batimastat); PKC inhibitors; ERK inhibitors; immunoblotting for LAR cleavage products; phosphatase activity assay","journal":"Cellular signalling","confidence":"High","confidence_rationale":"Tier 2 / Strong — specific protease identified using knockout cells and dominant-negative, kinase pathway requirements mapped, functional consequence (reduced phosphatase activity) quantified","pmids":["16478662"],"is_preprint":false},{"year":2006,"finding":"LAR co-immunoprecipitates with TrkB and this interaction is increased by BDNF. In LAR-deficient neurons, BDNF-induced activation of TrkB, Shc, AKT, ERK, and CREB was significantly decreased. LAR promotes neurotrophic signaling via Src: LAR-deficient neurons show increased Src regulatory domain phosphorylation (indicating Src inactivation), Src co-immunoprecipitates with LAR, and Src inhibitor PP2 blocks LAR's ability to augment TrkB signaling.","method":"Co-immunoprecipitation; LAR knockout neurons; LAR siRNA; LAR transfection; BDNF-stimulated signaling assays; Src inhibitor PP2; immunostaining","journal":"Journal of neurobiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP, multiple loss- and gain-of-function, defined pathway through Src, consistent results across KO and siRNA approaches","pmids":["17013927"],"is_preprint":false},{"year":2007,"finding":"LAR dephosphorylates DAPK at pY491/492 to stimulate DAPK catalytic, pro-apoptotic, and anti-adhesion/anti-migration activities. Conversely, Src phosphorylates DAPK at Y491/492 to inactivate it. Upon EGF stimulation, Src activation followed by LAR downregulation synergistically inactivate DAPK, facilitating tumor cell migration. These results establish DAPK as a substrate of LAR and identify reciprocal regulation by LAR and Src.","method":"In vitro dephosphorylation assays; site-directed mutagenesis of DAPK Y491/492; kinase activity assays; DAPK apoptosis and migration readouts; EGF stimulation experiments; LAR knockdown","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro dephosphorylation with specific site identified, mutagenesis confirming residues, functional rescue and cellular readouts, mechanistic pathway defined","pmids":["17803936"],"is_preprint":false},{"year":2007,"finding":"CaMKII-mediated degradation of liprin-α1 (via the ubiquitin-proteasome system activated by synaptic activity) reduces liprin-α1 protein levels and impairs dendritic targeting of LAR. Liprin-α1 mutants immune to CaMKII degradation impair dendrite arborization, reduce spine and synapse numbers, and inhibit LAR dendritic targeting, establishing that regulated liprin-α1 degradation controls LAR distribution and downstream dendrite development.","method":"CaMKII overexpression; proteasome inhibitors; liprin-α1 CaMKII-resistant mutants; hippocampal neuron imaging; dendrite, spine, synapse quantification","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — specific kinase-substrate relationship, dominant mutant rescue, multiple readouts, mechanistic pathway from activity to LAR localization established","pmids":["17419996"],"is_preprint":false},{"year":2007,"finding":"LAR is sequentially cleaved by alpha-secretase and then presenilin/gamma-secretase to generate a LAR intracellular domain (LICD). Inhibition of gamma-secretase increases LAR C-terminal fragments; prior ectodomain shedding by alpha-secretase is required (TAPI-1 blocks C-terminal fragment accumulation). Endogenous tyrosine-phosphorylated β-catenin co-immunoprecipitates with LAR; when gamma-secretase is inhibited, LAR–β-catenin association diminishes. LICD significantly decreased transcription of cyclin D1, a β-catenin target gene.","method":"Gamma-secretase inhibitors; presenilin-deficient cells; TAPI-1 alpha-secretase inhibitor; co-immunoprecipitation; in vitro cleavage; reporter gene assay for cyclin D1 transcription; immunoblotting for cleavage products","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — sequential cleavage mechanism established with multiple inhibitors and knockout cells, co-IP of β-catenin, transcriptional functional consequence measured","pmids":["17259169"],"is_preprint":false},{"year":2009,"finding":"NGL-3 (netrin-G ligand-3) interacts directly with LAR via a trans-synaptic interaction. NGL-3 and LAR expressed in heterologous cells induce pre- and postsynaptic differentiation bidirectionally in co-cultured hippocampal neurons. Knockdown of NGL-3 reduced excitatory synapse number and function. Competitive inhibition by soluble LAR reduced NGL-3-induced presynaptic differentiation, establishing the trans-synaptic NGL-3–LAR adhesion as regulating excitatory synapse formation.","method":"Co-culture synaptogenesis assay; heterologous cell expression; RNAi knockdown of NGL-3; soluble receptor competition; immunofluorescence; electrophysiology","journal":"Nature neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct binding interaction, bidirectional synaptogenesis assay, loss-of-function and competitive inhibition, electrophysiology","pmids":["19252495"],"is_preprint":false},{"year":2009,"finding":"Loss-of-function in both Ptprs and Ptprf (LAR) causes severe urogenital malformations (hydroureter, ureterocele) and craniofacial defects in mice. In cell culture, PTPσ (Ptprs) bound to and negatively regulated phosphorylation and signaling of the Ret receptor tyrosine kinase; Ret expression inhibited PTPσ-induced apoptosis. These results establish LAR family phosphatases as regulators of Ret-mediated apoptotic tissue morphogenesis during ureter maturation.","method":"Double knockout mice (Ptprs and Ptprf); histological and morphological analysis; cell culture binding and phosphorylation assays for Ret; apoptosis measurements","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo double knockout phenotype, in vitro binding and signaling assays for Ret, multiple phenotypic readouts","pmids":["19273906"],"is_preprint":false},{"year":2010,"finding":"The LRR domain of NGL-3 (nine LRRs) binds to the first two fibronectin III domains of LAR to induce bidirectional synapse formation. Gln-96 in the first LRR of NGL-3 is critical for LAR binding and presynaptic differentiation. PTPδ and PTPσ also bind NGL-3 via their first two FNIII domains with distinct synaptogenic outcomes.","method":"Domain-deletion and point mutation analysis; co-culture synaptogenesis assay; synapse induction quantification","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — domain mapping with mutagenesis identifying specific residues and domains, functional synaptogenesis readout, multiple LAR family members compared","pmids":["20139422"],"is_preprint":false},{"year":2013,"finding":"LAR dephosphorylates EphA2 specifically at phosphotyrosine 930, uncoupling Nck1 from EphA2 and attenuating EphA2-mediated cell migration. A siRNA screen of all human RPTPs identified EphA2 as a novel LAR substrate from a panel of 42 RTKs.","method":"siRNA screen of RPTPs; phosphorylation site-specific analysis (pY930 of EphA2); Nck1 co-immunoprecipitation; cell migration assay; site-directed mutagenesis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — systematic RPTP screen, site-specific dephosphorylation identified, downstream signaling (Nck1 uncoupling) and functional consequence (cell migration) defined","pmids":["23358419"],"is_preprint":false},{"year":2013,"finding":"Slitrks interact with LAR-RPTP family members to regulate synapse formation; PTPσ is specifically required for excitatory synaptic differentiation by Slitrks, whereas PTPδ is required for inhibitory synapse differentiation. Slitrks are enriched in postsynaptic densities and their overexpression promotes, while RNAi knockdown decreases, synapse density.","method":"RNAi knockdown; overexpression; co-culture synaptogenesis assay; immunofluorescence; family-member-specific interaction analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — specific isoform–receptor pairing for excitatory vs. inhibitory synapses established, loss- and gain-of-function, co-culture assays","pmids":["23345436"],"is_preprint":false},{"year":2013,"finding":"miR-24 directly targets PTPRF (LAR) mRNA to suppress its expression, leading to elevated EGFR phosphorylation. Ectopic re-expression of PTPRF (LAR) decreased pEGFR levels, cell invasion and migration, and tumor metastasis in vivo, establishing LAR as a direct negative regulator of EGFR signaling in breast cancer cells.","method":"miRNA target validation; ectopic PTPRF overexpression; EGFR phosphorylation assays; cell invasion/migration assays; in vivo mouse tumor metastasis model","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct target validation and functional overexpression, in vitro and in vivo readouts, single lab","pmids":["23418360"],"is_preprint":false},{"year":2014,"finding":"Crystal structures of LAR-RPTP Ig1-3 in complex with Slitrk LRR1 reveal that splicing inserts in LAR-RPTP Ig domains are key molecular determinants for Slitrk binding and synapse formation. Unique properties on the concave surface of Slitrk1 LRR1 mediate specific binding to LAR-RPTPs. Lateral interactions between adjacent trans-synaptic LAR-RPTP/Slitrk complexes in crystal lattices are critical for higher-order assembly and synaptogenic activity.","method":"X-ray crystallography; structure-guided mutagenesis; co-culture synaptogenesis assay; biochemical binding assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with functional validation by mutagenesis and synaptogenesis assay, multiple orthogonal methods","pmids":["25394468"],"is_preprint":false},{"year":2015,"finding":"SALM3 interacts with LAR-RPTPs (LAR, PTPσ, PTPδ) and this interaction requires the mini-exon B splice insert in LAR-RPTPs. SALM3-dependent presynaptic differentiation requires all three types of LAR-RPTPs. Salm3-knockout mice show markedly reduced excitatory synapse numbers in hippocampal CA1 and hypoactivity behavior, establishing SALM3–LAR-RPTP trans-synaptic adhesion as regulating excitatory synapse development.","method":"Biochemical binding assays; splice insert requirement analysis; co-culture synaptogenesis assay; Salm3 knockout mice; hippocampal synapse quantification; behavioral testing","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — splice-dependent interaction mechanism, in vivo knockout with defined synaptic and behavioral phenotype, multiple orthogonal methods","pmids":["26321637"],"is_preprint":false},{"year":2016,"finding":"Loss of LAR phosphatase activity in mouse embryonic fibroblasts results in reduced focal adhesion numbers and decreased adhesion to fibronectin. Phosphoproteomic analysis identified CDK1 as a kinase regulated by LAR; LAR activity is required for CDK1 activity, and CDK1 activity is required for focal adhesion complex formation. LAR regulates CDK1 through c-Abl and Akt family proteins.","method":"Phosphatase-deficient LAR knock-in MEFs; phosphoproteomics; kinase prediction analysis; CDK1 activity assays; focal adhesion quantification; adhesion assays; pharmacological inhibition of CDK1, c-Abl, Akt","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — phosphoproteomics plus targeted functional validation, defined signaling pathway through c-Abl/Akt/CDK1, multiple orthogonal approaches","pmids":["27352860"],"is_preprint":false},{"year":2017,"finding":"Drosophila Lar (LAR ortholog) and Fat2 function in a planar signaling system at the basal domain of follicular epithelial cells to coordinate collective cell migration. Fat2 signals from each cell's trailing edge to stabilize Lar localization and induce leading-edge protrusions in the cell behind; Lar signals from the leading edge to stimulate trailing-edge retraction in the cell ahead. Fat2/Lar signaling mediates short-range communication between neighboring cells.","method":"Live imaging of Drosophila follicular epithelium; genetic loss-of-function; subcellular localization analysis; mosaic analysis","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — live imaging combined with genetic analysis, specific cell-non-autonomous signaling directions defined, functional subcellular localization established","pmids":["28292425"],"is_preprint":false},{"year":2015,"finding":"CSPGs signal through LAR and RPTPσ receptors in spinal cord neural precursor cells (NPCs) to inhibit growth, survival, proliferation, and oligodendrocyte differentiation. These inhibitory effects are mediated intracellularly through the Rho/ROCK pathway and inhibition of Akt and Erk1/2 phosphorylation. Genetic knockdown of LAR and RPTPσ, or blockade of ROCK, attenuates CSPG inhibition of NPCs.","method":"In vitro NPC cultures with CSPG substrate; genetic models (LAR/RPTPσ knockdown); Rho/ROCK inhibitors; Akt and Erk1/2 phosphorylation assays; proliferation and differentiation assays","journal":"Stem cells","confidence":"High","confidence_rationale":"Tier 2 / Strong — receptor-specific genetic knockdown, defined downstream pathway (Rho/ROCK, Akt, Erk), multiple cellular phenotypic readouts","pmids":["25703008"],"is_preprint":false},{"year":2020,"finding":"Crystal structure of LAR D1D2 in complex with SAM repeats of liprin-α3 reveals a conserved two-site binding mode. Liprin-αs promote LAR clustering in cells via the liprin-α/LAR interaction and liprin-α oligomerization. A unique homophilic D1/D1 interaction of LAR was identified; disruption of D1/D1 interaction diminishes liprin-α-promoted clustering and increases tyrosine dephosphorylation, establishing that LAR forms clusters in which phosphatase activity is negatively regulated. Additionally, LAR binding to liprin-α allosterically regulates the liprin-α/liprin-β interaction.","method":"X-ray crystallography; cellular clustering assays; mutagenesis of D1/D1 interface; tyrosine dephosphorylation assays; biochemical binding assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with multiple functional validations: mutagenesis, cellular clustering, phosphatase activity regulation, allosteric effects demonstrated","pmids":["31924785"],"is_preprint":false},{"year":2020,"finding":"Conditional deletion of all three LAR-RPTPs (PTPδ, PTPσ, LAR) in mice did not affect synaptic connectivity or synapse number in vivo or in cultured neurons, but decreased NMDA receptor-mediated synaptic responses via a trans-synaptic mechanism without changing NMDA receptor protein levels or subunit composition.","method":"Conditional triple knockout mice (LAR-RPTPs); electrophysiology (AMPA- and NMDA-receptor EPSCs at Schaffer collateral synapses); protein level analysis; synapse counting in cultured neurons","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — triple conditional knockout with electrophysiological readouts in vivo and in vitro, specific effect on NMDA receptor function, no effect on synapse number established","pmids":["31985401"],"is_preprint":false},{"year":2021,"finding":"Superresolution microscopy reveals that PTPδ (a LAR-RPTP family member) localizes precisely to the synaptic cleft, apposed to postsynaptic scaffolds at both excitatory and inhibitory synapses. Triple conditional knockout of PTPδ, PTPσ, and LAR showed only mild effects on synaptic vesicle clustering and active zone architecture, with no effect on synapse number, membrane anchoring of the active zone, or vesicle docking and release.","method":"STORM/superresolution microscopy; triple-conditional knockout mice; electron microscopy; synaptic vesicle docking and release assays","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — superresolution localization combined with comprehensive triple-KO structural and functional analysis, complemented by independent study (Sclip & Südhof 2020)","pmids":["33656439"],"is_preprint":false},{"year":2019,"finding":"PPARγ directly binds to a consensus AGGTCA site in the PTPRF (LAR) promoter, demonstrated by electrophoretic mobility shift assay. PPARγ activation induces PTPRF expression, and ectopic PTPRF overexpression in breast cancer cells suppresses proliferation, migration, invasion, and colony formation, while a PTP inhibitor (NSC87877) abrogates PPARγ-mediated suppression, establishing PTPRF as a downstream effector of PPARγ tumor-suppressor activity.","method":"Electrophoretic mobility shift assay (EMSA); PPARγ overexpression/agonist treatment; PTPRF overexpression; PTP inhibitor (NSC87877); in vitro cell migration/invasion assays; in vivo mouse tumor model","journal":"European review for medical and pharmacological sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct promoter binding by EMSA, functional rescue by overexpression, PTP inhibitor abrogation, in vivo confirmation; single lab","pmids":["31799666"],"is_preprint":false},{"year":2013,"finding":"Loss of both Ptprs and Ptprf (LAR) in mouse embryos leads to craniofacial malformations resembling Pierre-Robin sequence. Signaling analysis in embryonic tissues and MEFs identifies increased BMP-Smad signaling and abrogated canonical Wnt signaling in LAR family phosphatase-deficient cells. Chemical inhibition of GSK3β reactivates β-catenin signaling in deficient cells, establishing LAR-RPTPs as necessary for normal Wnt/β-catenin pathway activation.","method":"Double knockout mice; histological and cell proliferation analysis; Smad and β-catenin signaling pathway analysis; GSK3β inhibitor rescue in MEFs","journal":"Development","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo knockout phenotype, signaling pathway analysis in embryonic tissue and MEFs, pharmacological rescue identifying GSK3β/Wnt axis","pmids":["23863482"],"is_preprint":false},{"year":2020,"finding":"Nrxn1α interacts with PTPσ (LAR-RPTP family) via heparan sulfate (HS)-dependent, high-affinity binding to Ig domains of PTPσ, regulated by PTPσ splicing status. Nrxn1α WT (but not ΔHS mutant lacking HS) inhibited PTPσ-mediated postsynapse-inducing activity at excitatory synapses and suppressed PTPσ-mediated maintenance of excitatory postsynaptic specializations. Drosophila epistasis of Dlar and Dnrx confirmed functional interactions controlling NMJ synapse formation and synaptic transmission.","method":"Biochemical binding assays; co-culture synaptogenesis assay; HS-deletion mutant analysis; hippocampal neuron imaging; Drosophila double-mutant epistasis at NMJ","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — HS-dependent binding mechanism, functional epistasis in vivo (Drosophila), cellular competition experiments in mammalian neurons, multiple orthogonal methods","pmids":["33037075"],"is_preprint":false},{"year":2018,"finding":"Blocking LAR and PTPσ receptors in spinal cord injury reduces M1 microglia/macrophage populations while promoting M2 and T regulatory cells, and harnesses microglia phagocytosis and mobilization. CSPGs regulate microglia, at least in part, through the Rho/ROCK pathway downstream of LAR and PTPσ, establishing LAR as a mediator of CSPG-dependent neuroinflammation.","method":"Intrathecal peptide delivery (ILP/ISP blocking peptides); flow cytometry; immunohistochemistry; Western blotting; primary microglia in vitro cultures; Rho/ROCK pathway inhibition","journal":"Journal of neuroinflammation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — receptor-specific blocking peptides with in vivo and in vitro parallel approaches, Rho/ROCK pathway identified as downstream effector","pmids":["29558941"],"is_preprint":false},{"year":2011,"finding":"The SAM domain-containing cytoplasmic adaptor protein Caskin mediates LAR signal transduction during Drosophila motor axon guidance. Caskin physically interacts with LAR via its N-terminal SAM domain in vivo and in vitro. Caskin and Liprin-α do not bind LAR concurrently, suggesting they form distinct signaling complexes. The SH2/SH3 adaptor Dock is a second Caskin binding partner. A vertebrate Caskin homolog also interacts with LAR family members.","method":"Drosophila genetics; yeast two-hybrid and in vitro binding assays; genetic interaction/epistasis with LAR alleles; competition binding between Caskin and Liprin-α; vertebrate homolog interaction assays","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetics, in vitro binding with domain specificity, competition assay, evolutionary conservation confirmed in vertebrates","pmids":["21430143"],"is_preprint":false}],"current_model":"PTPRF (LAR) is a transmembrane receptor protein tyrosine phosphatase whose membrane-proximal D1 domain catalyzes dephosphorylation via a covalent phosphoenzyme intermediate at an essential active-site cysteine (C1522), while the membrane-distal D2 domain lacks catalytic activity but mediates substrate association, regulatory interactions (with liprin-α/LIP.1), and allosteric modulation of D1 activity; LAR undergoes sequential proprotein cleavage by a subtilisin-like protease and regulated ectodomain shedding/internalization governed by PKC, EGFR/TACE/ADAM-17, and presenilin/γ-secretase to generate an intracellular domain; at the plasma membrane LAR forms clusters whose phosphatase activity is negatively regulated by homophilic D1–D1 interactions stabilized by liprin-α binding; LAR dephosphorylates multiple substrates including the insulin receptor (reducing PI3-kinase and MAP kinase signaling), IRS proteins, EphA2-pY930 (uncoupling Nck1 to attenuate cell migration), DAPK-pY491/492 (activating its pro-apoptotic and anti-migratory functions), c-Met (mediating contact-inhibition of HGF signaling), and p130Cas (destabilizing it to induce apoptosis); LAR promotes neurotrophic signaling by dephosphorylating the Src inhibitory site to activate Src, which in turn transactivates TrkB; at synapses, presynaptic LAR acts as a trans-synaptic adhesion hub that binds postsynaptic partners (NGL-3, Slitrks, SALMs, neurexins via heparan sulfate) through its Ig/FNIII extracellular domains in an alternative-splicing-dependent manner and is required for NMDA receptor-mediated synaptic transmission through a trans-synaptic mechanism; intracellularly, LAR signals through liprin-α and the adaptor Caskin to regulate active zone morphology and axon guidance, and through the Rho/ROCK pathway as a receptor for chondroitin sulfate proteoglycans to restrict axon regeneration and NPC neurogenesis."},"narrative":{"mechanistic_narrative":"PTPRF (LAR) is a transmembrane receptor protein tyrosine phosphatase that couples cell-surface adhesion to intracellular tyrosine dephosphorylation, governing growth-factor signaling, cell adhesion/apoptosis, and synapse organization [PMID:1695146, PMID:7852302, PMID:15750591]. Its tandem cytoplasmic domains are functionally divided: the membrane-proximal D1 domain is the catalytic unit, acting through a covalent phosphoenzyme intermediate that depends on an essential active-site cysteine (C1522), whose oxidation by peroxynitrile irreversibly inactivates the enzyme, while the membrane-distal D2 domain lacks catalytic activity but regulates D1 activity and mediates substrate and partner association [PMID:1918076, PMID:1370625, PMID:10486138, PMID:11158333]. LAR is expressed as a non-covalently associated two-subunit complex generated by subtilisin-like proprotein cleavage, and its phosphatase function is downregulated by regulated ectodomain shedding and sequential proteolysis—via PKC, EGFR/ERK-driven ADAM-17/TACE cleavage, and presenilin/γ-secretase processing that liberates a LAR intracellular domain (LICD) repressing β-catenin target transcription [PMID:1547787, PMID:8089133, PMID:9245795, PMID:16478662, PMID:17259169]. As a phosphatase, LAR negatively regulates multiple receptor tyrosine kinases, dephosphorylating and physically associating with the insulin receptor to restrain PI3-kinase and downstream signaling (with in vivo roles in glucose homeostasis and insulin action) and acting on EGFR, c-Met (contact inhibition of HGF signaling), and IRS proteins [PMID:7852302, PMID:8732688, PMID:8995282, PMID:9519761, PMID:11309481, PMID:16415345]; it also dephosphorylates EphA2-pY930 to uncouple Nck1 and attenuate migration, dephosphorylates and destabilizes p130Cas to induce apoptosis, and activates DAPK by removing inhibitory pY491/492 [PMID:10320483, PMID:17803936, PMID:23358419]. LAR organizes signaling at focal adhesions through liprin-α/LIP.1 and the Trio GEF, and crystallographic and cellular work shows liprin-α promotes LAR clustering via a homophilic D1–D1 interaction that negatively regulates phosphatase activity [PMID:7796809, PMID:8643598, PMID:9624153, PMID:31924785]. At synapses, presynaptic LAR functions as a trans-synaptic adhesion hub whose Ig/FNIII ectodomains engage postsynaptic partners NGL-3, Slitrks, SALM3, and heparan-sulfate-modified neurexins in a splicing-dependent manner to drive bidirectional synaptic differentiation and NMDA receptor-mediated transmission, signaling intracellularly through liprin-α and the adaptor Caskin to control synapse and active-zone organization and axon guidance [PMID:15750591, PMID:19252495, PMID:20139422, PMID:26321637, PMID:31985401, PMID:33037075, PMID:21430143]. LAR is additionally a receptor for chondroitin sulfate proteoglycans that signals through Rho/ROCK to restrict neural precursor neurogenesis and modulate neuroinflammation [PMID:25703008, PMID:29558941].","teleology":[{"year":1991,"claim":"Established the catalytic logic of LAR's two cytoplasmic domains—answering whether both phosphatase-like domains are active and how catalysis proceeds.","evidence":"Bacterial expression, site-directed mutagenesis, and phosphoenzyme intermediate trapping defining C1522 as the catalytic cysteine and D1 as the sole active domain","pmids":["1695146","1918076","1370625"],"confidence":"High","gaps":["Physiological substrates not yet identified in this period","Regulatory role of D2 only inferred, not mechanistically resolved"]},{"year":1992,"claim":"Defined D2 as a non-catalytic regulatory domain modulating D1 activity, refining the division of labor between the tandem domains.","evidence":"Purified recombinant D1 vs. D1D2 fragments with polycation stimulation and substrate-specificity comparison","pmids":["1370625","1318316","1645351"],"confidence":"Medium","gaps":["Endogenous regulators substituting for polycations not identified","Structural basis of D2 modulation unresolved at this stage"]},{"year":1994,"claim":"Established that LAR is a proteolytically processed two-subunit receptor whose ectodomain shedding regulates its function, linking processing to phosphatase regulation.","evidence":"Scanning and site-directed mutagenesis mapping proprotein cleavage, subunit association, and shedding sites in transfected cells","pmids":["1547787","8089133"],"confidence":"High","gaps":["The shedding protease and physiological triggers not identified here","Fate of the cytoplasmic fragment after shedding unknown"]},{"year":1997,"claim":"Identified the insulin receptor as a direct physical and functional LAR substrate and placed LAR control at growth-factor signaling, defining its role as a negative RTK regulator in cells and in vivo.","evidence":"Antisense knockdown, overexpression with domain-specific controls, reciprocal co-IP, endosomal fractionation, and kinetic dephosphorylation assays across insulin/EGF/HGF receptors","pmids":["7852302","8732688","8557682","8995282","9207225"],"confidence":"High","gaps":["Site-specific dephosphorylation residues on the receptors not mapped","Whether association is constitutive or signaling-dependent only partially resolved"]},{"year":1998,"claim":"Identified liprin-α/LIP.1 and Trio as D2-binding partners that localize and assemble LAR into adhesion and clustering complexes, establishing the scaffolding arm of LAR signaling.","evidence":"Interaction-trap/yeast two-hybrid identification, co-localization at focal adhesions, GEF activity assays, and co-expression-induced LAR clustering","pmids":["7796809","8643598","9624153"],"confidence":"High","gaps":["Functional consequence of clustering on catalytic activity not yet resolved in this period","Whether Trio is a substrate or pure complex partner left open"]},{"year":1998,"claim":"Defined in vivo developmental and metabolic roles via mouse knockouts—mammary alveolar differentiation, glucose homeostasis, and cholinergic neuron networks—establishing LAR as physiologically required across tissues.","evidence":"Gene-trap and gene-targeted knockout mice with histological, neuroanatomical, and euglycemic-clamp metabolic phenotyping","pmids":["9039657","9245518","9519761"],"confidence":"High","gaps":["Cell-autonomous vs. systemic contributions not fully separated","Specific substrates underlying each tissue phenotype not identified in these studies"]},{"year":1999,"claim":"Established p130Cas as an in vivo substrate whose LAR-mediated dephosphorylation and destabilization drives apoptosis, linking LAR catalysis to cell-death control.","evidence":"Overexpression with phosphatase-dead mutants, in vitro dephosphorylation, co-localization, and p130Cas rescue of LAR-induced apoptosis","pmids":["10320483","9501065"],"confidence":"High","gaps":["Mechanism linking p130Cas destabilization to caspase activation not detailed","Context determining apoptotic vs. signaling outcomes unresolved"]},{"year":1999,"claim":"Showed the catalytic cysteine is a redox target irreversibly inactivated by peroxynitrite, identifying a chemical mode of LAR regulation.","evidence":"In vitro kinetic phosphatase assays with peroxynitrite, NO donors, GSNO, and DTT reversal tests","pmids":["10486138"],"confidence":"High","gaps":["Physiological relevance of peroxynitrite inactivation in cells not established","No demonstration of reversible redox cycling in vivo"]},{"year":2006,"claim":"Resolved the proteases and kinase pathways driving regulated LAR processing and intracellular-domain generation, connecting RTK activity to LAR downregulation and β-catenin-dependent transcription.","evidence":"TACE-knockout fibroblasts, dominant-negative TACE, γ-secretase and α-secretase inhibitors, presenilin-deficient cells, co-IP, and a cyclin D1 reporter","pmids":["16478662","17259169","9245795"],"confidence":"High","gaps":["Quantitative contribution of LICD to nuclear signaling in vivo unknown","Whether shed ectodomain has independent signaling activity not addressed"]},{"year":2007,"claim":"Expanded the LAR substrate/effector network to neurotrophic and migration control—activating Src to transactivate TrkB and reciprocally regulating DAPK with Src—establishing context-dependent pro- and anti-migratory roles.","evidence":"LAR-knockout/siRNA neurons, reciprocal co-IP, Src inhibitor PP2, in vitro DAPK dephosphorylation with site mutagenesis, and migration/apoptosis readouts","pmids":["17013927","17803936"],"confidence":"High","gaps":["Direct LAR target site on Src (regulatory tyrosine) inferred but not crystallographically mapped","Switch determining LAR vs. Src dominance over DAPK not fully defined"]},{"year":2009,"claim":"Identified LAR as a presynaptic trans-synaptic adhesion receptor engaging postsynaptic NGL-3 to induce bidirectional synaptic differentiation, opening LAR's synaptic organizer function.","evidence":"Co-culture synaptogenesis assays, heterologous expression, NGL-3 RNAi, soluble-LAR competition, and electrophysiology","pmids":["19252495","15750591"],"confidence":"High","gaps":["How synaptic adhesion couples to or operates independently of phosphatase activity not resolved","Endogenous splicing isoform requirements not yet mapped here"]},{"year":2015,"claim":"Defined a splicing-dependent code for LAR's postsynaptic partner selection (Slitrks, SALM3, HS-neurexins) and mapped the extracellular domains and residues mediating these interactions structurally.","evidence":"Domain/point mutagenesis, crystal structures of Ig/FNIII–ligand complexes, splice-insert requirement analysis, knockout mice, and co-culture synaptogenesis","pmids":["20139422","23345436","26321637","25394468","33037075"],"confidence":"High","gaps":["In vivo necessity of individual partners separable from redundancy across LAR-RPTPs not fully dissected","Higher-order assembly seen in crystals not directly visualized at native synapses"]},{"year":2016,"claim":"Linked LAR catalytic activity to adhesion and cell-cycle signaling through a c-Abl/Akt/CDK1 axis, and identified EphA2-pY930 as a site-specific substrate uncoupling Nck1 to limit migration.","evidence":"Phosphatase-deficient knock-in MEFs with phosphoproteomics and kinase inhibition; siRNA RPTP screen with site-specific EphA2 dephosphorylation and migration assays","pmids":["27352860","23358419","23418360","31799666"],"confidence":"High","gaps":["Direct vs. indirect dephosphorylation steps in the CDK1 axis not fully separated","Transcriptional regulation of PTPRF (miR-24, PPARγ) integration with phosphatase output incompletely mapped"]},{"year":2020,"claim":"Resolved the structural and functional basis of LAR clustering—a homophilic D1–D1 interaction stabilized by liprin-α oligomerization that negatively regulates phosphatase activity—unifying scaffolding and catalytic control.","evidence":"Crystal structure of LAR D1D2–liprin-α3 SAM complex, D1/D1 interface mutagenesis, cellular clustering, and dephosphorylation assays","pmids":["31924785"],"confidence":"High","gaps":["Whether activity-suppressing clustering operates at synapses vs. adhesions not directly compared","Triggers shifting LAR between clustered (low-activity) and dispersed states unknown"]},{"year":2020,"claim":"Dissociated LAR-RPTP synaptic adhesion from synapse number in vivo—triple knockouts preserve synapse count but selectively impair NMDA receptor-mediated transmission—refining the synaptic role to functional modulation.","evidence":"Conditional triple-knockout mice with electrophysiology, superresolution synaptic-cleft localization, and EM of active-zone architecture","pmids":["31985401","33656439","16476662","21430143"],"confidence":"High","gaps":["Mechanism linking trans-synaptic LAR to NMDA receptor function unresolved","Redundancy among LAR-RPTP family members complicates attributing roles to PTPRF specifically"]},{"year":null,"claim":"How LAR integrates its dual identity—catalytic phosphatase versus phosphatase-independent adhesion organizer—and what switches it between activity states across adhesion, growth-factor, and synaptic contexts remains unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No unified model of when adhesion engagement modulates catalytic output","In vivo substrate repertoire of PTPRF in distinct tissues incompletely defined","Functional separation of PTPRF from paralogs PTPσ/PTPδ in shared phenotypes still limited"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,4,21,28,31,37]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[1,4]},{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[34,41,50]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[27,44]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[7,19,52]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[3,13,19,45]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[33]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[13,14]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[33]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[8,10,12,28,37]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[26,34,41,46,50]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[18,21]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[17,35,49]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[3,6,29,33]}],"complexes":["LAR E-subunit/P-subunit receptor complex","LAR–liprin-α cluster"],"partners":["PPFIA1/LIPRIN-Α (LIP.1)","TRIO","INSR","MET","CASKIN1","NGL-3 (LRRC4B)","SLITRK","NRXN1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P10586","full_name":"Receptor-type tyrosine-protein phosphatase F","aliases":["Leukocyte common antigen related","LAR"],"length_aa":1907,"mass_kda":212.9,"function":"Possible cell adhesion receptor. It possesses an intrinsic protein tyrosine phosphatase activity (PTPase) and dephosphorylates EPHA2 regulating its activity The first PTPase domain has enzymatic activity, while the second one seems to affect the substrate specificity of the first one","subcellular_location":"Membrane","url":"https://www.uniprot.org/uniprotkb/P10586/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PTPRF","classification":"Not Classified","n_dependent_lines":29,"n_total_lines":1208,"dependency_fraction":0.024006622516556293},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PTPRF","total_profiled":1310},"omim":[{"mim_id":"621122","title":"PAUL-CHAO NEURODEVELOPMENTAL SYNDROME; NEDPACH","url":"https://www.omim.org/entry/621122"},{"mim_id":"620363","title":"RNA, U5F SMALL NUCLEAR 1; RNU5F-1","url":"https://www.omim.org/entry/620363"},{"mim_id":"618301","title":"KAZRIN, PERIPLAKIN-INTERACTING PROTEIN; KAZN","url":"https://www.omim.org/entry/618301"},{"mim_id":"616001","title":"BREASTS AND/OR NIPPLES, APLASIA OR HYPOPLASIA OF, 2; BNAH2","url":"https://www.omim.org/entry/616001"},{"mim_id":"611054","title":"PTPRF-INTERACTING PROTEIN ALPHA-1; PPFIA1","url":"https://www.omim.org/entry/611054"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Golgi apparatus","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in 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hyperactivity in multiple behavioural tests.","date":"2004","source":"Behavioural brain research","url":"https://pubmed.ncbi.nlm.nih.gov/15302123","citation_count":36,"is_preprint":false},{"pmid":"21430143","id":"PMC_21430143","title":"The cytoplasmic adaptor protein Caskin mediates Lar signal transduction during Drosophila motor axon guidance.","date":"2011","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/21430143","citation_count":35,"is_preprint":false},{"pmid":"33037075","id":"PMC_33037075","title":"LAR-RPTPs Directly Interact with Neurexins to Coordinate Bidirectional Assembly of Molecular Machineries.","date":"2020","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/33037075","citation_count":34,"is_preprint":false},{"pmid":"22326027","id":"PMC_22326027","title":"LAR receptor tyrosine phosphatases and HSPGs guide peripheral sensory axons to the skin.","date":"2012","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/22326027","citation_count":34,"is_preprint":false},{"pmid":"9207225","id":"PMC_9207225","title":"The protein tyrosine phosphatase LAR has a major impact on insulin receptor dephosphorylation.","date":"1997","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/9207225","citation_count":34,"is_preprint":false},{"pmid":"22378638","id":"PMC_22378638","title":"The receptor tyrosine phosphatase Lar regulates adhesion between Drosophila male germline stem cells and the niche.","date":"2012","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/22378638","citation_count":29,"is_preprint":false},{"pmid":"15555919","id":"PMC_15555919","title":"Stimulated regeneration of the crushed adult rat optic nerve correlates with attenuated expression of the protein tyrosine phosphatases RPTPalpha, STEP, and LAR.","date":"2004","source":"Molecular and cellular neurosciences","url":"https://pubmed.ncbi.nlm.nih.gov/15555919","citation_count":29,"is_preprint":false},{"pmid":"27480238","id":"PMC_27480238","title":"SALM4 suppresses excitatory synapse development by cis-inhibiting trans-synaptic SALM3-LAR adhesion.","date":"2016","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/27480238","citation_count":29,"is_preprint":false},{"pmid":"27352860","id":"PMC_27352860","title":"LAR protein tyrosine phosphatase regulates focal adhesions through CDK1.","date":"2016","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/27352860","citation_count":27,"is_preprint":false},{"pmid":"33907985","id":"PMC_33907985","title":"Glucose metabolism outcomes in acromegaly patients on treatment with pasireotide-LAR or pasireotide-LAR plus Pegvisomant.","date":"2021","source":"Endocrine","url":"https://pubmed.ncbi.nlm.nih.gov/33907985","citation_count":27,"is_preprint":false},{"pmid":"20731479","id":"PMC_20731479","title":"Octreotide long-acting release (LAR): a review of its use in the management of acromegaly.","date":"2010","source":"Drugs","url":"https://pubmed.ncbi.nlm.nih.gov/20731479","citation_count":27,"is_preprint":false},{"pmid":"12095414","id":"PMC_12095414","title":"Expression of the leucocyte common antigen-related (LAR) tyrosine phosphatase is regulated by cell density through functional E-cadherin complexes.","date":"2002","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/12095414","citation_count":27,"is_preprint":false},{"pmid":"31518993","id":"PMC_31518993","title":"Pasireotide-LAR in acromegaly patients treated with a combination therapy: a real-life study.","date":"2019","source":"Endocrine connections","url":"https://pubmed.ncbi.nlm.nih.gov/31518993","citation_count":27,"is_preprint":false},{"pmid":"23863482","id":"PMC_23863482","title":"Inactivation of LAR family phosphatase genes Ptprs and Ptprf causes craniofacial malformations resembling Pierre-Robin sequence.","date":"2013","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/23863482","citation_count":26,"is_preprint":false},{"pmid":"31799666","id":"PMC_31799666","title":"PPARγ inhibits breast cancer progression by upregulating PTPRF expression.","date":"2019","source":"European review for medical and pharmacological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/31799666","citation_count":26,"is_preprint":false},{"pmid":"23358419","id":"PMC_23358419","title":"Receptor protein tyrosine phosphatase-receptor tyrosine kinase substrate screen identifies EphA2 as a target for LAR in cell migration.","date":"2013","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/23358419","citation_count":26,"is_preprint":false},{"pmid":"33656439","id":"PMC_33656439","title":"Intact synapse structure and function after combined knockout of PTPδ, PTPσ, and LAR.","date":"2021","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/33656439","citation_count":25,"is_preprint":false},{"pmid":"29081732","id":"PMC_29081732","title":"LAR-RPTP Clustering Is Modulated by Competitive Binding between Synaptic Adhesion Partners and Heparan Sulfate.","date":"2017","source":"Frontiers in molecular neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/29081732","citation_count":25,"is_preprint":false},{"pmid":"10727868","id":"PMC_10727868","title":"Expression of CRYP-alpha, LAR, PTP-delta, and PTP-rho in the developing Xenopus visual system.","date":"2000","source":"Mechanisms of development","url":"https://pubmed.ncbi.nlm.nih.gov/10727868","citation_count":25,"is_preprint":false},{"pmid":"35953756","id":"PMC_35953756","title":"Luminal androgen receptor (LAR) subtype of triple-negative breast cancer: molecular, morphological, and clinical features.","date":"2022","source":"Journal of Zhejiang University. Science. B","url":"https://pubmed.ncbi.nlm.nih.gov/35953756","citation_count":24,"is_preprint":false},{"pmid":"35256527","id":"PMC_35256527","title":"Suppressing CSPG/LAR/PTPσ Axis Facilitates Neuronal Replacement and Synaptogenesis by Human Neural Precursor Grafts and Improves Recovery after Spinal Cord Injury.","date":"2022","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/35256527","citation_count":24,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":49555,"output_tokens":14708,"usd":0.184642,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":27703,"output_tokens":5958,"usd":0.143733,"stage2_stop_reason":"end_turn"},"total_usd":0.328375,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1990,\n      \"finding\": \"The first of the two intracellular PTPase-like domains of LAR has catalytic enzyme activity, while the second domain lacks detectable catalytic activity. A single conserved cysteine residue in domain 1 is absolutely required for activity; substitution at this position abolished activity. Sequences in domain 2 influence substrate specificity.\",\n      \"method\": \"Deletion and point mutations in cytoplasmic region; in vitro phosphatase activity assays with multiple substrates\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro enzymatic assay combined with systematic mutagenesis of both domains, replicated across multiple substrates\",\n      \"pmids\": [\"1695146\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"The cytoplasmic domain of rat LAR expressed in bacteria has protein tyrosine phosphatase activity. Cys-1522 in domain 1 is the catalytic cysteine; C1522S mutation causes >99% loss of activity. A covalent phosphoenzyme intermediate was trapped with 32P-labeled substrate, establishing the catalytic mechanism. The inactive C1522S mutant could be phosphorylated in vitro by PKC and v-abl tyrosine kinase.\",\n      \"method\": \"Bacterial expression, purification, site-directed mutagenesis, phosphoenzyme intermediate trapping by SDS-PAGE autoradiography, in vitro kinase assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted in vitro with mutagenesis and mechanistic intermediate trapping in a single rigorous study\",\n      \"pmids\": [\"1918076\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"Temperature-sensitive and thermostable missense mutations in LAR domain 1 cluster between amino acid positions 1329–1407, identifying a structurally critical region for enzyme folding and activity. A second-site revertant (C1446-Y) suppresses multiple temperature-sensitive mutations, suggesting structural interactions within this region.\",\n      \"method\": \"Bacterial expression of LAR domain 1; hydroxylamine and MNNG mutagenesis; biochemical characterization of mutants at permissive and restrictive temperatures; second-site reversion analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic characterization of multiple mutants, single lab\",\n      \"pmids\": [\"1645351\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"LAR is expressed on the cell surface as a complex of two non-covalently associated subunits (E-subunit ~150 kDa extracellular; P-subunit ~85 kDa transmembrane+cytoplasmic) derived from a proprotein. Proprotein cleavage occurs intracellularly at a paired basic amino acid site by a subtilisin-like endoprotease; mutation of key arginine residues blocks cleavage. The E-subunit is shed from the cell surface during cell growth, providing a mechanism to regulate LAR phosphatase function.\",\n      \"method\": \"Mutational analysis of cleavage site; biochemical characterization of subunit expression; cell surface shedding assays\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — mutagenesis identifying specific residues required for cleavage, combined with biochemical demonstration of shedding and subunit structure\",\n      \"pmids\": [\"1547787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"The E. coli-expressed LAR two-domain fragment (D1D2) has almost identical specific activity to the single domain (D1) fragment, confirming a single functional active site in domain 1. 18O exchange from [18O4]-inorganic phosphate into water and 32P-phosphoenzyme labeling established a phosphoenzyme intermediate mechanism. Polycationic polypeptides stimulate D1D2 but not D1 PTPase activity via domain 2, indicating domain 2 has a regulatory function.\",\n      \"method\": \"E. coli expression and purification; isotope exchange assay (18O); phosphoenzyme intermediate labeling; substrate specificity comparison; polycation stimulation assay\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal mechanistic assays (isotope exchange, phosphoenzyme trapping, domain deletion) in single rigorous study\",\n      \"pmids\": [\"1370625\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"Basic polypeptides stimulate the PTPase activity of LAR D1D2 but not D1 alone using peptide substrate Raytide, indicating that domain 2 has a regulatory function on domain 1 catalytic activity. Polypeptides containing high proportions of tyrosine are inhibitory to LAR and related phosphatases.\",\n      \"method\": \"Purified recombinant LAR fragments from E. coli; peptide substrate assays with modulatory compounds\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro biochemical assay with purified domains, single lab, two orthogonal approaches (stimulation and inhibition)\",\n      \"pmids\": [\"1318316\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Functional regions for LAR proprotein processing, subunit association, and shedding were mapped by scanning mutagenesis. Three residues (two in a penta-arginine sequence and one C-terminal to the cleavage site) are essential for proprotein cleavage. Several non-contiguous residues in the P-subunit ectodomain are required for subunit association. Shedding involves a second proteolytic cleavage within the P-subunit ectodomain near the transmembrane peptide.\",\n      \"method\": \"Site-directed and scanning mutagenesis; biochemical analysis of processing, subunit association, and shedding in transfected cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — systematic mutagenesis identifying specific residues for each processing step, multiple orthogonal readouts\",\n      \"pmids\": [\"8089133\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"LAR co-localizes with the novel cytoplasmic 160 kDa phosphoserine protein LIP.1 (LAR-interacting protein 1) at the ends of focal adhesions most proximal to the cell nucleus. LIP.1 binds specifically to the membrane-distal D2 PTPase domain of LAR and appears to localize LAR to focal adhesions, implicating this complex in regulation of focal adhesion disassembly.\",\n      \"method\": \"Identification of LIP.1 by interaction-trap assay; co-localization by immunofluorescence; domain-binding analysis\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — binding partner identified by interaction trap, co-localization demonstrated, domain mapped, functional context established\",\n      \"pmids\": [\"7796809\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Antisense-mediated suppression of LAR in McA-RH7777 hepatoma cells (63% reduction) increased insulin-dependent insulin receptor autophosphorylation (~150%), receptor tyrosine kinase activity (35%), and insulin-dependent PI3-kinase activity (350%), establishing LAR as a negative regulator of insulin receptor signaling in intact cells.\",\n      \"method\": \"Antisense RNA expression in hepatoma cells; insulin receptor autophosphorylation and kinase assays; PI3-kinase activity assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — specific loss-of-function with defined molecular phenotype at multiple pathway nodes, consistent across insulin concentrations\",\n      \"pmids\": [\"7852302\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"LAR, PTPδ, and PTPσ all interact with LIP.1 via their membrane-distal phosphatase domains. All three phosphatases exhibit similar in vitro PTPase activities and share alternative splicing of mini-exons, establishing them as a subfamily with conserved structure, activity, and interacting proteins.\",\n      \"method\": \"Cloning; in vitro PTPase activity assays; LIP.1 binding/interaction analysis across family members\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical characterization of multiple family members, interaction with LIP.1 demonstrated, single study\",\n      \"pmids\": [\"8524829\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Overexpression of full-length LAR in McA-RH7777 hepatoma cells (2.4-fold increase) reduced insulin receptor autophosphorylation 40% in intact cells, decreased IRS-1 and Shc tyrosine phosphorylation, and reduced IRS-1-associated PI3-kinase activity to 47% of control. Overexpression of the cytoplasmic domain alone (cytosolic, not membrane-localized) had no significant effect, indicating transmembrane localization is required for LAR to act on the insulin receptor.\",\n      \"method\": \"Stable transfection with full-length vs. cytoplasmic-only LAR constructs; insulin receptor autophosphorylation; substrate phosphorylation; kinase assays; cell fractionation\",\n      \"journal\": \"Molecular endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — gain-of-function with domain-specific controls (full-length vs. cytoplasmic), multiple orthogonal readouts, requirement for membrane localization established\",\n      \"pmids\": [\"8732688\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Trio, a 2861-amino acid multidomain protein, was identified as a LAR-interacting protein via the interaction-trap assay. Trio contains two GEF domains (one Rac-specific, one Rho-specific) and a serine/threonine kinase domain. Trio appears phosphorylated only on serine residues, suggesting it is not a LAR substrate but forms a signaling complex with LAR at focal adhesions.\",\n      \"method\": \"Interaction-trap (yeast two-hybrid) assay; GEF activity assays for Rac and Rho specificity; phosphorylation analysis; co-localization at focal adhesions\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — binding partner identified by two-hybrid and confirmed biochemically, GEF activities directly demonstrated, multiple orthogonal methods\",\n      \"pmids\": [\"8643598\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Antisense suppression of LAR in McA-RH7777 cells increased EGF receptor autophosphorylation by >300%, HGF receptor autophosphorylation by >250%, downstream IRS-1 and Shc phosphorylation, MAP kinase activation, and PI3-kinase activation in response to all three growth factors, demonstrating LAR modulates signaling by multiple receptor tyrosine kinases.\",\n      \"method\": \"Antisense RNA suppression; receptor autophosphorylation assays; substrate phosphorylation; MAP kinase and PI3-kinase activity assays for EGF, HGF, and insulin receptors\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function across three RTK pathways with multiple readouts, consistent results\",\n      \"pmids\": [\"8557682\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"LAR co-immunoprecipitates with the insulin receptor in intact CHO cells overexpressing both proteins; up to 11.8% of LAR co-precipitates with the insulin receptor. The association was increased by cross-linking and 3.9-fold by insulin treatment. In insulin-stimulated rat liver, LAR was enriched in endosomes with the insulin receptor, and LAR-neutralizing antibodies decreased endosomal insulin receptor dephosphorylation by 28%, demonstrating a direct physical and functional association.\",\n      \"method\": \"Co-immunoprecipitation; chemical cross-linking; subcellular fractionation of rat liver; in situ endosomal dephosphorylation with neutralizing antibodies\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP, endosomal co-localization in vivo, neutralizing antibody functional assay — multiple orthogonal approaches\",\n      \"pmids\": [\"8995282\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"LAR and PTPσ undergo induced proteolytic processing (shedding of extracellular domains) upon treatment with calcium ionophore A23187 or phorbol ester TPA; TPA-induced LAR processing required PKCα overexpression in 293 cells. Both phosphatases localize preferentially to adherens junctions and desmosomes, co-localizing with plakoglobin. Direct association of plakoglobin and β-catenin with the intracellular domain of LAR was demonstrated in vitro. After ectodomain shedding, catalytically active intracellular portions are internalized away from cell-cell contacts.\",\n      \"method\": \"Inducible proteolytic processing; confocal microscopy; in vitro binding assay for β-catenin and plakoglobin; PKCα overexpression; inhibitor studies; cell fractionation\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple methods: in vitro binding, localization by confocal, inducible processing with kinase requirement identified\",\n      \"pmids\": [\"9245795\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"LAR antisense suppression in McA-RH7777 cells prolonged insulin receptor dephosphorylation 2.6-fold (t½ increased from 34 to 87 s), providing direct kinetic evidence that LAR is a major physiological regulator of insulin receptor dephosphorylation in situ. EGF receptor dephosphorylation was also prolonged in LAR-deficient cells.\",\n      \"method\": \"Antisense RNA suppression; kinetic dephosphorylation assay following acid elution of surface-bound insulin; EGF receptor dephosphorylation assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — specific loss-of-function with kinetic mechanistic readout, consistent with multiple prior studies\",\n      \"pmids\": [\"9207225\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"LAR deficiency in transgenic mice (gene trap) results in reduced size of basal forebrain cholinergic neurons and markedly decreased cholinergic innervation of the dentate gyrus, establishing LAR as required for formation and/or maintenance of cholinergic neuronal networks in mammals.\",\n      \"method\": \"Gene trap transgenic mice with reduced LAR expression; histomorphometry of basal forebrain cholinergic neurons; immunohistochemistry of hippocampal cholinergic innervation\",\n      \"journal\": \"Journal of neuroscience research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo loss-of-function with defined neuroanatomical phenotype, single lab\",\n      \"pmids\": [\"9039657\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Knockout mice lacking both LAR phosphatase domains (LAR−/−) develop impaired terminal differentiation of mammary gland alveoli during late pregnancy, failing to switch to a lactational state and showing rapid postpartum involution. LAR expression peaks around day 16 of gestation in wild-type mice, establishing LAR-mediated signaling as required for mammary gland development and lactation.\",\n      \"method\": \"Gene targeting in mouse ES cells; histological analysis of mammary gland; Northern blot for LAR expression during pregnancy; neonatal survival assessment\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean knockout with specific tissue phenotype and developmental expression correlation, multiple readouts\",\n      \"pmids\": [\"9245518\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Overexpression of wild-type LAR (but not a truncated extracellular-only form) in mammalian cells activates the caspase pathway and induces p53-independent apoptosis, establishing a role for LAR's phosphatase-active intracellular region in cell-death control.\",\n      \"method\": \"Inducible expression system; caspase activity assays; cell viability assays comparing full-length vs. extracellular-only truncation mutant\",\n      \"journal\": \"Current biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — inducible expression with domain-specific control, caspase pathway activation measured, single lab\",\n      \"pmids\": [\"9501065\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Alpha-liprins (a family of seven LAR-interacting proteins) bind to the membrane-distal phosphatase domains of LAR family members via their C-terminal non-coiled coil regions; beta-liprins interact with alpha-liprins. Co-expression of liprin-α2 alters LAR cellular localization and induces LAR clustering, establishing liprins as regulators of LAR localization at specific plasma membrane sites.\",\n      \"method\": \"Yeast two-hybrid and biochemical binding assays; co-expression localization studies by immunofluorescence; family-wide interaction mapping\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — binding demonstrated biochemically and functionally confirmed by co-expression localization changes; multiple family members tested\",\n      \"pmids\": [\"9624153\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"LAR-deficient mice exhibit significantly lower fasting plasma insulin and glucose and a reduced rate of hepatic glucose production, but display paradoxical resistance to insulin-stimulated glucose disposal and a 47% reduction in insulin-stimulated PI3-kinase activity in liver, demonstrating LAR has a physiological role in insulin action and glucose homeostasis in vivo.\",\n      \"method\": \"Insertional mutagenesis knockout mice; euglycemic clamp studies; hepatic PI3-kinase activity; glucose disposal measurements\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo knockout with multiple metabolic phenotypic readouts and defined post-receptor signaling defect\",\n      \"pmids\": [\"9519761\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"LAR overexpression specifically decreases the steady-state level and tyrosine phosphorylation of p130Cas by dephosphorylating it, reducing its protein stability. This is blocked by tyrosine phosphatase inhibitors and phosphatase-domain deletion mutants of LAR. LAR preferentially dephosphorylates p130Cas in vitro. LAR and p130Cas co-localize along stress fibers and at focal adhesions. Restoring p130Cas levels alleviates LAR-induced apoptosis, establishing p130Cas as an in vivo substrate of LAR mediating apoptosis.\",\n      \"method\": \"Overexpression of LAR and phosphatase-dead mutants; in vitro phosphatase assay; immunofluorescence co-localization; p130Cas rescue experiment; pharmacological inhibition\",\n      \"journal\": \"Genes to cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro dephosphorylation assay, in vivo substrate identification with multiple controls, rescue experiment, co-localization\",\n      \"pmids\": [\"10320483\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"LAR is irreversibly inactivated by peroxynitrite (IC50 ≤0.9 µM) with a bimolecular rate constant of 2.3 × 10^7 M^−1 s^−1, among the fastest reactions of peroxynitrite with biological molecules. The inactivation was essentially irreversible (DTT restores <10% activity), consistent with oxidation of the essential active-site thiolate. Nitric oxide and S-nitrosoglutathione caused only partial, reversible inhibition.\",\n      \"method\": \"In vitro phosphatase activity assays; competition kinetics with cysteine; treatment with peroxynitrite, NO donors, and GSNO; DTT reversal experiments\",\n      \"journal\": \"Archives of biochemistry and biophysics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinetic assays with multiple reagents, quantitative rate constants determined, single lab\",\n      \"pmids\": [\"10486138\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Stable antisense-mediated knockdown of LAR in PC12 cells results in a two-fold increase specifically in NGF-induced (but not FGF-induced) neurite outgrowth and a two- to three-fold decrease in serum-deprivation-induced cell death, demonstrating that endogenous LAR negatively regulates neurotrophin responses and promotes cell death.\",\n      \"method\": \"Stable antisense transfection; neurite outgrowth quantification; serum deprivation cell death assay; comparison of NGF vs. FGF responses\",\n      \"journal\": \"Journal of neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — specific loss-of-function with defined molecular readouts, ligand specificity established, single lab\",\n      \"pmids\": [\"10699984\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Overexpression of LAR specifically in muscle of transgenic mice causes whole-body insulin resistance: fasting insulin elevated 2.5-fold, glucose disposal reduced 39–50%, IRS-2 phosphorylation reduced 62%, and PI3-kinase associated with phosphotyrosine, IRS-1, and IRS-2 reduced 34–57%. Normal insulin receptor and IRS-1 phosphorylation was observed, suggesting dephosphorylation of specific IRS protein regulatory phosphotyrosines as the mechanism.\",\n      \"method\": \"Muscle-specific transgenic mice overexpressing human LAR; euglycemic clamp; insulin receptor and IRS phosphorylation; PI3-kinase activity assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — tissue-specific gain-of-function in vivo with multiple metabolic and signaling readouts identifying IRS proteins as the mechanistic target\",\n      \"pmids\": [\"11309481\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Domain 2 of LAR mediates substrate (insulin receptor) association (C1813S mutation weakened association), while domain 1 catalytic activity (C1522S mutation) is required for dephosphorylation. The extracellular domains of both LAR and insulin receptor also contribute to their association. LAR is phosphorylated by insulin receptor tyrosine kinase and autodephosphorylates via domain 1.\",\n      \"method\": \"Cysteine-to-serine active-site mutants of each domain; co-immunoprecipitation with insulin receptor; phosphorylation assays; domain deletion analysis\",\n      \"journal\": \"Molecular endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — systematic domain mutagenesis with substrate co-IP, multiple domain combinations tested, identifies distinct roles for each domain\",\n      \"pmids\": [\"11158333\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"LAR-RPTP is concentrated at mature excitatory synapses in hippocampal neurons. RNAi knockdown of LAR or dominant-negative disruption causes loss of excitatory synapses and dendritic spines, reduction of surface AMPA receptors, impaired dendritic targeting of the cadherin–β-catenin complex, and reduced mEPSC amplitude and frequency. β-catenin and GluR2/3 co-immunoprecipitate with liprin-α and GRIP from rat brain, establishing LAR as required for excitatory synapse development and AMPA receptor trafficking.\",\n      \"method\": \"RNAi knockdown; dominant-negative expression; immunofluorescence; electrophysiology (mEPSC recording); co-immunoprecipitation from brain extracts; surface receptor biotinylation\",\n      \"journal\": \"Nature neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal approaches (RNAi, dominant-negative, co-IP, electrophysiology), defined synaptic phenotypes, confirmed in rat brain\",\n      \"pmids\": [\"15750591\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Drosophila HSPGs Syndecan (Sdc) and Dallylike (Dlp) both bind at high affinity to the receptor tyrosine phosphatase LAR. Double mutant analysis showed LAR is required for actions of both HSPGs at the NMJ: Sdc promotes LAR-dependent presynaptic terminal growth, while Dlp inhibits LAR activity. These results establish HSPGs as extracellular ligands that differentially regulate LAR.\",\n      \"method\": \"High-affinity binding assays; Drosophila genetics with single and double mutants; NMJ morphological analysis; epistasis analysis\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct binding assays combined with in vivo epistasis in Drosophila, defining LAR-dependent vs. -independent phenotypes\",\n      \"pmids\": [\"16476662\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"LAR associates with c-Met/HGF receptor specifically in confluent (contact-inhibited) hepatocytes. LAR activity and expression increase after HGF stimulation in confluent but not sparse cells. Purified LAR dephosphorylates tyrosine-phosphorylated c-Met in vitro. Antisense knockdown of LAR in confluent cells restores prolonged c-Met phosphorylation and mitogenic response, establishing LAR as mediating contact-inhibition of HGF/c-Met signaling via dephosphorylation.\",\n      \"method\": \"Co-immunoprecipitation; in vitro LAR phosphatase assay with c-Met substrate; antisense oligonucleotides; cell density-dependent signaling assays; kinase activity measurements\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro dephosphorylation assay, co-IP, antisense loss-of-function with defined phenotype, multiple methods in single study\",\n      \"pmids\": [\"16415345\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"EGFR associates with LAR and induces proteolytic processing (cleavage) of the LAR P-subunit via an ERK1/2-dependent pathway. EGFR-induced LAR shedding is mediated by the metalloproteinase ADAM-17/TACE (established by TACE-knockout fibroblasts and dominant-negative TACE). Cleavage results in degradation of the catalytic LAR P-subunit and significantly reduced cellular phosphatase activity.\",\n      \"method\": \"EGFR overexpression and stimulation; TACE-knockout fibroblasts; dominant-negative TACE; metalloproteinase inhibitor (Batimastat); PKC inhibitors; ERK inhibitors; immunoblotting for LAR cleavage products; phosphatase activity assay\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — specific protease identified using knockout cells and dominant-negative, kinase pathway requirements mapped, functional consequence (reduced phosphatase activity) quantified\",\n      \"pmids\": [\"16478662\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"LAR co-immunoprecipitates with TrkB and this interaction is increased by BDNF. In LAR-deficient neurons, BDNF-induced activation of TrkB, Shc, AKT, ERK, and CREB was significantly decreased. LAR promotes neurotrophic signaling via Src: LAR-deficient neurons show increased Src regulatory domain phosphorylation (indicating Src inactivation), Src co-immunoprecipitates with LAR, and Src inhibitor PP2 blocks LAR's ability to augment TrkB signaling.\",\n      \"method\": \"Co-immunoprecipitation; LAR knockout neurons; LAR siRNA; LAR transfection; BDNF-stimulated signaling assays; Src inhibitor PP2; immunostaining\",\n      \"journal\": \"Journal of neurobiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP, multiple loss- and gain-of-function, defined pathway through Src, consistent results across KO and siRNA approaches\",\n      \"pmids\": [\"17013927\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"LAR dephosphorylates DAPK at pY491/492 to stimulate DAPK catalytic, pro-apoptotic, and anti-adhesion/anti-migration activities. Conversely, Src phosphorylates DAPK at Y491/492 to inactivate it. Upon EGF stimulation, Src activation followed by LAR downregulation synergistically inactivate DAPK, facilitating tumor cell migration. These results establish DAPK as a substrate of LAR and identify reciprocal regulation by LAR and Src.\",\n      \"method\": \"In vitro dephosphorylation assays; site-directed mutagenesis of DAPK Y491/492; kinase activity assays; DAPK apoptosis and migration readouts; EGF stimulation experiments; LAR knockdown\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro dephosphorylation with specific site identified, mutagenesis confirming residues, functional rescue and cellular readouts, mechanistic pathway defined\",\n      \"pmids\": [\"17803936\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"CaMKII-mediated degradation of liprin-α1 (via the ubiquitin-proteasome system activated by synaptic activity) reduces liprin-α1 protein levels and impairs dendritic targeting of LAR. Liprin-α1 mutants immune to CaMKII degradation impair dendrite arborization, reduce spine and synapse numbers, and inhibit LAR dendritic targeting, establishing that regulated liprin-α1 degradation controls LAR distribution and downstream dendrite development.\",\n      \"method\": \"CaMKII overexpression; proteasome inhibitors; liprin-α1 CaMKII-resistant mutants; hippocampal neuron imaging; dendrite, spine, synapse quantification\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — specific kinase-substrate relationship, dominant mutant rescue, multiple readouts, mechanistic pathway from activity to LAR localization established\",\n      \"pmids\": [\"17419996\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"LAR is sequentially cleaved by alpha-secretase and then presenilin/gamma-secretase to generate a LAR intracellular domain (LICD). Inhibition of gamma-secretase increases LAR C-terminal fragments; prior ectodomain shedding by alpha-secretase is required (TAPI-1 blocks C-terminal fragment accumulation). Endogenous tyrosine-phosphorylated β-catenin co-immunoprecipitates with LAR; when gamma-secretase is inhibited, LAR–β-catenin association diminishes. LICD significantly decreased transcription of cyclin D1, a β-catenin target gene.\",\n      \"method\": \"Gamma-secretase inhibitors; presenilin-deficient cells; TAPI-1 alpha-secretase inhibitor; co-immunoprecipitation; in vitro cleavage; reporter gene assay for cyclin D1 transcription; immunoblotting for cleavage products\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — sequential cleavage mechanism established with multiple inhibitors and knockout cells, co-IP of β-catenin, transcriptional functional consequence measured\",\n      \"pmids\": [\"17259169\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"NGL-3 (netrin-G ligand-3) interacts directly with LAR via a trans-synaptic interaction. NGL-3 and LAR expressed in heterologous cells induce pre- and postsynaptic differentiation bidirectionally in co-cultured hippocampal neurons. Knockdown of NGL-3 reduced excitatory synapse number and function. Competitive inhibition by soluble LAR reduced NGL-3-induced presynaptic differentiation, establishing the trans-synaptic NGL-3–LAR adhesion as regulating excitatory synapse formation.\",\n      \"method\": \"Co-culture synaptogenesis assay; heterologous cell expression; RNAi knockdown of NGL-3; soluble receptor competition; immunofluorescence; electrophysiology\",\n      \"journal\": \"Nature neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct binding interaction, bidirectional synaptogenesis assay, loss-of-function and competitive inhibition, electrophysiology\",\n      \"pmids\": [\"19252495\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Loss-of-function in both Ptprs and Ptprf (LAR) causes severe urogenital malformations (hydroureter, ureterocele) and craniofacial defects in mice. In cell culture, PTPσ (Ptprs) bound to and negatively regulated phosphorylation and signaling of the Ret receptor tyrosine kinase; Ret expression inhibited PTPσ-induced apoptosis. These results establish LAR family phosphatases as regulators of Ret-mediated apoptotic tissue morphogenesis during ureter maturation.\",\n      \"method\": \"Double knockout mice (Ptprs and Ptprf); histological and morphological analysis; cell culture binding and phosphorylation assays for Ret; apoptosis measurements\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo double knockout phenotype, in vitro binding and signaling assays for Ret, multiple phenotypic readouts\",\n      \"pmids\": [\"19273906\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The LRR domain of NGL-3 (nine LRRs) binds to the first two fibronectin III domains of LAR to induce bidirectional synapse formation. Gln-96 in the first LRR of NGL-3 is critical for LAR binding and presynaptic differentiation. PTPδ and PTPσ also bind NGL-3 via their first two FNIII domains with distinct synaptogenic outcomes.\",\n      \"method\": \"Domain-deletion and point mutation analysis; co-culture synaptogenesis assay; synapse induction quantification\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — domain mapping with mutagenesis identifying specific residues and domains, functional synaptogenesis readout, multiple LAR family members compared\",\n      \"pmids\": [\"20139422\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"LAR dephosphorylates EphA2 specifically at phosphotyrosine 930, uncoupling Nck1 from EphA2 and attenuating EphA2-mediated cell migration. A siRNA screen of all human RPTPs identified EphA2 as a novel LAR substrate from a panel of 42 RTKs.\",\n      \"method\": \"siRNA screen of RPTPs; phosphorylation site-specific analysis (pY930 of EphA2); Nck1 co-immunoprecipitation; cell migration assay; site-directed mutagenesis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — systematic RPTP screen, site-specific dephosphorylation identified, downstream signaling (Nck1 uncoupling) and functional consequence (cell migration) defined\",\n      \"pmids\": [\"23358419\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Slitrks interact with LAR-RPTP family members to regulate synapse formation; PTPσ is specifically required for excitatory synaptic differentiation by Slitrks, whereas PTPδ is required for inhibitory synapse differentiation. Slitrks are enriched in postsynaptic densities and their overexpression promotes, while RNAi knockdown decreases, synapse density.\",\n      \"method\": \"RNAi knockdown; overexpression; co-culture synaptogenesis assay; immunofluorescence; family-member-specific interaction analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — specific isoform–receptor pairing for excitatory vs. inhibitory synapses established, loss- and gain-of-function, co-culture assays\",\n      \"pmids\": [\"23345436\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"miR-24 directly targets PTPRF (LAR) mRNA to suppress its expression, leading to elevated EGFR phosphorylation. Ectopic re-expression of PTPRF (LAR) decreased pEGFR levels, cell invasion and migration, and tumor metastasis in vivo, establishing LAR as a direct negative regulator of EGFR signaling in breast cancer cells.\",\n      \"method\": \"miRNA target validation; ectopic PTPRF overexpression; EGFR phosphorylation assays; cell invasion/migration assays; in vivo mouse tumor metastasis model\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct target validation and functional overexpression, in vitro and in vivo readouts, single lab\",\n      \"pmids\": [\"23418360\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Crystal structures of LAR-RPTP Ig1-3 in complex with Slitrk LRR1 reveal that splicing inserts in LAR-RPTP Ig domains are key molecular determinants for Slitrk binding and synapse formation. Unique properties on the concave surface of Slitrk1 LRR1 mediate specific binding to LAR-RPTPs. Lateral interactions between adjacent trans-synaptic LAR-RPTP/Slitrk complexes in crystal lattices are critical for higher-order assembly and synaptogenic activity.\",\n      \"method\": \"X-ray crystallography; structure-guided mutagenesis; co-culture synaptogenesis assay; biochemical binding assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with functional validation by mutagenesis and synaptogenesis assay, multiple orthogonal methods\",\n      \"pmids\": [\"25394468\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"SALM3 interacts with LAR-RPTPs (LAR, PTPσ, PTPδ) and this interaction requires the mini-exon B splice insert in LAR-RPTPs. SALM3-dependent presynaptic differentiation requires all three types of LAR-RPTPs. Salm3-knockout mice show markedly reduced excitatory synapse numbers in hippocampal CA1 and hypoactivity behavior, establishing SALM3–LAR-RPTP trans-synaptic adhesion as regulating excitatory synapse development.\",\n      \"method\": \"Biochemical binding assays; splice insert requirement analysis; co-culture synaptogenesis assay; Salm3 knockout mice; hippocampal synapse quantification; behavioral testing\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — splice-dependent interaction mechanism, in vivo knockout with defined synaptic and behavioral phenotype, multiple orthogonal methods\",\n      \"pmids\": [\"26321637\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Loss of LAR phosphatase activity in mouse embryonic fibroblasts results in reduced focal adhesion numbers and decreased adhesion to fibronectin. Phosphoproteomic analysis identified CDK1 as a kinase regulated by LAR; LAR activity is required for CDK1 activity, and CDK1 activity is required for focal adhesion complex formation. LAR regulates CDK1 through c-Abl and Akt family proteins.\",\n      \"method\": \"Phosphatase-deficient LAR knock-in MEFs; phosphoproteomics; kinase prediction analysis; CDK1 activity assays; focal adhesion quantification; adhesion assays; pharmacological inhibition of CDK1, c-Abl, Akt\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — phosphoproteomics plus targeted functional validation, defined signaling pathway through c-Abl/Akt/CDK1, multiple orthogonal approaches\",\n      \"pmids\": [\"27352860\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Drosophila Lar (LAR ortholog) and Fat2 function in a planar signaling system at the basal domain of follicular epithelial cells to coordinate collective cell migration. Fat2 signals from each cell's trailing edge to stabilize Lar localization and induce leading-edge protrusions in the cell behind; Lar signals from the leading edge to stimulate trailing-edge retraction in the cell ahead. Fat2/Lar signaling mediates short-range communication between neighboring cells.\",\n      \"method\": \"Live imaging of Drosophila follicular epithelium; genetic loss-of-function; subcellular localization analysis; mosaic analysis\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — live imaging combined with genetic analysis, specific cell-non-autonomous signaling directions defined, functional subcellular localization established\",\n      \"pmids\": [\"28292425\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CSPGs signal through LAR and RPTPσ receptors in spinal cord neural precursor cells (NPCs) to inhibit growth, survival, proliferation, and oligodendrocyte differentiation. These inhibitory effects are mediated intracellularly through the Rho/ROCK pathway and inhibition of Akt and Erk1/2 phosphorylation. Genetic knockdown of LAR and RPTPσ, or blockade of ROCK, attenuates CSPG inhibition of NPCs.\",\n      \"method\": \"In vitro NPC cultures with CSPG substrate; genetic models (LAR/RPTPσ knockdown); Rho/ROCK inhibitors; Akt and Erk1/2 phosphorylation assays; proliferation and differentiation assays\",\n      \"journal\": \"Stem cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — receptor-specific genetic knockdown, defined downstream pathway (Rho/ROCK, Akt, Erk), multiple cellular phenotypic readouts\",\n      \"pmids\": [\"25703008\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Crystal structure of LAR D1D2 in complex with SAM repeats of liprin-α3 reveals a conserved two-site binding mode. Liprin-αs promote LAR clustering in cells via the liprin-α/LAR interaction and liprin-α oligomerization. A unique homophilic D1/D1 interaction of LAR was identified; disruption of D1/D1 interaction diminishes liprin-α-promoted clustering and increases tyrosine dephosphorylation, establishing that LAR forms clusters in which phosphatase activity is negatively regulated. Additionally, LAR binding to liprin-α allosterically regulates the liprin-α/liprin-β interaction.\",\n      \"method\": \"X-ray crystallography; cellular clustering assays; mutagenesis of D1/D1 interface; tyrosine dephosphorylation assays; biochemical binding assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with multiple functional validations: mutagenesis, cellular clustering, phosphatase activity regulation, allosteric effects demonstrated\",\n      \"pmids\": [\"31924785\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Conditional deletion of all three LAR-RPTPs (PTPδ, PTPσ, LAR) in mice did not affect synaptic connectivity or synapse number in vivo or in cultured neurons, but decreased NMDA receptor-mediated synaptic responses via a trans-synaptic mechanism without changing NMDA receptor protein levels or subunit composition.\",\n      \"method\": \"Conditional triple knockout mice (LAR-RPTPs); electrophysiology (AMPA- and NMDA-receptor EPSCs at Schaffer collateral synapses); protein level analysis; synapse counting in cultured neurons\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — triple conditional knockout with electrophysiological readouts in vivo and in vitro, specific effect on NMDA receptor function, no effect on synapse number established\",\n      \"pmids\": [\"31985401\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Superresolution microscopy reveals that PTPδ (a LAR-RPTP family member) localizes precisely to the synaptic cleft, apposed to postsynaptic scaffolds at both excitatory and inhibitory synapses. Triple conditional knockout of PTPδ, PTPσ, and LAR showed only mild effects on synaptic vesicle clustering and active zone architecture, with no effect on synapse number, membrane anchoring of the active zone, or vesicle docking and release.\",\n      \"method\": \"STORM/superresolution microscopy; triple-conditional knockout mice; electron microscopy; synaptic vesicle docking and release assays\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — superresolution localization combined with comprehensive triple-KO structural and functional analysis, complemented by independent study (Sclip & Südhof 2020)\",\n      \"pmids\": [\"33656439\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PPARγ directly binds to a consensus AGGTCA site in the PTPRF (LAR) promoter, demonstrated by electrophoretic mobility shift assay. PPARγ activation induces PTPRF expression, and ectopic PTPRF overexpression in breast cancer cells suppresses proliferation, migration, invasion, and colony formation, while a PTP inhibitor (NSC87877) abrogates PPARγ-mediated suppression, establishing PTPRF as a downstream effector of PPARγ tumor-suppressor activity.\",\n      \"method\": \"Electrophoretic mobility shift assay (EMSA); PPARγ overexpression/agonist treatment; PTPRF overexpression; PTP inhibitor (NSC87877); in vitro cell migration/invasion assays; in vivo mouse tumor model\",\n      \"journal\": \"European review for medical and pharmacological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct promoter binding by EMSA, functional rescue by overexpression, PTP inhibitor abrogation, in vivo confirmation; single lab\",\n      \"pmids\": [\"31799666\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Loss of both Ptprs and Ptprf (LAR) in mouse embryos leads to craniofacial malformations resembling Pierre-Robin sequence. Signaling analysis in embryonic tissues and MEFs identifies increased BMP-Smad signaling and abrogated canonical Wnt signaling in LAR family phosphatase-deficient cells. Chemical inhibition of GSK3β reactivates β-catenin signaling in deficient cells, establishing LAR-RPTPs as necessary for normal Wnt/β-catenin pathway activation.\",\n      \"method\": \"Double knockout mice; histological and cell proliferation analysis; Smad and β-catenin signaling pathway analysis; GSK3β inhibitor rescue in MEFs\",\n      \"journal\": \"Development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo knockout phenotype, signaling pathway analysis in embryonic tissue and MEFs, pharmacological rescue identifying GSK3β/Wnt axis\",\n      \"pmids\": [\"23863482\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Nrxn1α interacts with PTPσ (LAR-RPTP family) via heparan sulfate (HS)-dependent, high-affinity binding to Ig domains of PTPσ, regulated by PTPσ splicing status. Nrxn1α WT (but not ΔHS mutant lacking HS) inhibited PTPσ-mediated postsynapse-inducing activity at excitatory synapses and suppressed PTPσ-mediated maintenance of excitatory postsynaptic specializations. Drosophila epistasis of Dlar and Dnrx confirmed functional interactions controlling NMJ synapse formation and synaptic transmission.\",\n      \"method\": \"Biochemical binding assays; co-culture synaptogenesis assay; HS-deletion mutant analysis; hippocampal neuron imaging; Drosophila double-mutant epistasis at NMJ\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — HS-dependent binding mechanism, functional epistasis in vivo (Drosophila), cellular competition experiments in mammalian neurons, multiple orthogonal methods\",\n      \"pmids\": [\"33037075\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Blocking LAR and PTPσ receptors in spinal cord injury reduces M1 microglia/macrophage populations while promoting M2 and T regulatory cells, and harnesses microglia phagocytosis and mobilization. CSPGs regulate microglia, at least in part, through the Rho/ROCK pathway downstream of LAR and PTPσ, establishing LAR as a mediator of CSPG-dependent neuroinflammation.\",\n      \"method\": \"Intrathecal peptide delivery (ILP/ISP blocking peptides); flow cytometry; immunohistochemistry; Western blotting; primary microglia in vitro cultures; Rho/ROCK pathway inhibition\",\n      \"journal\": \"Journal of neuroinflammation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — receptor-specific blocking peptides with in vivo and in vitro parallel approaches, Rho/ROCK pathway identified as downstream effector\",\n      \"pmids\": [\"29558941\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The SAM domain-containing cytoplasmic adaptor protein Caskin mediates LAR signal transduction during Drosophila motor axon guidance. Caskin physically interacts with LAR via its N-terminal SAM domain in vivo and in vitro. Caskin and Liprin-α do not bind LAR concurrently, suggesting they form distinct signaling complexes. The SH2/SH3 adaptor Dock is a second Caskin binding partner. A vertebrate Caskin homolog also interacts with LAR family members.\",\n      \"method\": \"Drosophila genetics; yeast two-hybrid and in vitro binding assays; genetic interaction/epistasis with LAR alleles; competition binding between Caskin and Liprin-α; vertebrate homolog interaction assays\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetics, in vitro binding with domain specificity, competition assay, evolutionary conservation confirmed in vertebrates\",\n      \"pmids\": [\"21430143\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PTPRF (LAR) is a transmembrane receptor protein tyrosine phosphatase whose membrane-proximal D1 domain catalyzes dephosphorylation via a covalent phosphoenzyme intermediate at an essential active-site cysteine (C1522), while the membrane-distal D2 domain lacks catalytic activity but mediates substrate association, regulatory interactions (with liprin-α/LIP.1), and allosteric modulation of D1 activity; LAR undergoes sequential proprotein cleavage by a subtilisin-like protease and regulated ectodomain shedding/internalization governed by PKC, EGFR/TACE/ADAM-17, and presenilin/γ-secretase to generate an intracellular domain; at the plasma membrane LAR forms clusters whose phosphatase activity is negatively regulated by homophilic D1–D1 interactions stabilized by liprin-α binding; LAR dephosphorylates multiple substrates including the insulin receptor (reducing PI3-kinase and MAP kinase signaling), IRS proteins, EphA2-pY930 (uncoupling Nck1 to attenuate cell migration), DAPK-pY491/492 (activating its pro-apoptotic and anti-migratory functions), c-Met (mediating contact-inhibition of HGF signaling), and p130Cas (destabilizing it to induce apoptosis); LAR promotes neurotrophic signaling by dephosphorylating the Src inhibitory site to activate Src, which in turn transactivates TrkB; at synapses, presynaptic LAR acts as a trans-synaptic adhesion hub that binds postsynaptic partners (NGL-3, Slitrks, SALMs, neurexins via heparan sulfate) through its Ig/FNIII extracellular domains in an alternative-splicing-dependent manner and is required for NMDA receptor-mediated synaptic transmission through a trans-synaptic mechanism; intracellularly, LAR signals through liprin-α and the adaptor Caskin to regulate active zone morphology and axon guidance, and through the Rho/ROCK pathway as a receptor for chondroitin sulfate proteoglycans to restrict axon regeneration and NPC neurogenesis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PTPRF (LAR) is a transmembrane receptor protein tyrosine phosphatase that couples cell-surface adhesion to intracellular tyrosine dephosphorylation, governing growth-factor signaling, cell adhesion/apoptosis, and synapse organization [#0, #8, #26]. Its tandem cytoplasmic domains are functionally divided: the membrane-proximal D1 domain is the catalytic unit, acting through a covalent phosphoenzyme intermediate that depends on an essential active-site cysteine (C1522), whose oxidation by peroxynitrile irreversibly inactivates the enzyme, while the membrane-distal D2 domain lacks catalytic activity but regulates D1 activity and mediates substrate and partner association [#1, #4, #22, #25]. LAR is expressed as a non-covalently associated two-subunit complex generated by subtilisin-like proprotein cleavage, and its phosphatase function is downregulated by regulated ectodomain shedding and sequential proteolysis—via PKC, EGFR/ERK-driven ADAM-17/TACE cleavage, and presenilin/\\u03b3-secretase processing that liberates a LAR intracellular domain (LICD) repressing \\u03b2-catenin target transcription [#3, #6, #14, #29, #33]. As a phosphatase, LAR negatively regulates multiple receptor tyrosine kinases, dephosphorylating and physically associating with the insulin receptor to restrain PI3-kinase and downstream signaling (with in vivo roles in glucose homeostasis and insulin action) and acting on EGFR, c-Met (contact inhibition of HGF signaling), and IRS proteins [#8, #10, #13, #20, #24, #28]; it also dephosphorylates EphA2-pY930 to uncouple Nck1 and attenuate migration, dephosphorylates and destabilizes p130Cas to induce apoptosis, and activates DAPK by removing inhibitory pY491/492 [#21, #31, #37]. LAR organizes signaling at focal adhesions through liprin-\\u03b1/LIP.1 and the Trio GEF, and crystallographic and cellular work shows liprin-\\u03b1 promotes LAR clustering via a homophilic D1\\u2013D1 interaction that negatively regulates phosphatase activity [#7, #11, #19, #45]. At synapses, presynaptic LAR functions as a trans-synaptic adhesion hub whose Ig/FNIII ectodomains engage postsynaptic partners NGL-3, Slitrks, SALM3, and heparan-sulfate-modified neurexins in a splicing-dependent manner to drive bidirectional synaptic differentiation and NMDA receptor-mediated transmission, signaling intracellularly through liprin-\\u03b1 and the adaptor Caskin to control synapse and active-zone organization and axon guidance [#26, #34, #36, #41, #46, #50, #52]. LAR is additionally a receptor for chondroitin sulfate proteoglycans that signals through Rho/ROCK to restrict neural precursor neurogenesis and modulate neuroinflammation [#44, #51].\",\n  \"teleology\": [\n    {\n      \"year\": 1991,\n      \"claim\": \"Established the catalytic logic of LAR's two cytoplasmic domains—answering whether both phosphatase-like domains are active and how catalysis proceeds.\",\n      \"evidence\": \"Bacterial expression, site-directed mutagenesis, and phosphoenzyme intermediate trapping defining C1522 as the catalytic cysteine and D1 as the sole active domain\",\n      \"pmids\": [\"1695146\", \"1918076\", \"1370625\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological substrates not yet identified in this period\", \"Regulatory role of D2 only inferred, not mechanistically resolved\"]\n    },\n    {\n      \"year\": 1992,\n      \"claim\": \"Defined D2 as a non-catalytic regulatory domain modulating D1 activity, refining the division of labor between the tandem domains.\",\n      \"evidence\": \"Purified recombinant D1 vs. D1D2 fragments with polycation stimulation and substrate-specificity comparison\",\n      \"pmids\": [\"1370625\", \"1318316\", \"1645351\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Endogenous regulators substituting for polycations not identified\", \"Structural basis of D2 modulation unresolved at this stage\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Established that LAR is a proteolytically processed two-subunit receptor whose ectodomain shedding regulates its function, linking processing to phosphatase regulation.\",\n      \"evidence\": \"Scanning and site-directed mutagenesis mapping proprotein cleavage, subunit association, and shedding sites in transfected cells\",\n      \"pmids\": [\"1547787\", \"8089133\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The shedding protease and physiological triggers not identified here\", \"Fate of the cytoplasmic fragment after shedding unknown\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Identified the insulin receptor as a direct physical and functional LAR substrate and placed LAR control at growth-factor signaling, defining its role as a negative RTK regulator in cells and in vivo.\",\n      \"evidence\": \"Antisense knockdown, overexpression with domain-specific controls, reciprocal co-IP, endosomal fractionation, and kinetic dephosphorylation assays across insulin/EGF/HGF receptors\",\n      \"pmids\": [\"7852302\", \"8732688\", \"8557682\", \"8995282\", \"9207225\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Site-specific dephosphorylation residues on the receptors not mapped\", \"Whether association is constitutive or signaling-dependent only partially resolved\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Identified liprin-\\u03b1/LIP.1 and Trio as D2-binding partners that localize and assemble LAR into adhesion and clustering complexes, establishing the scaffolding arm of LAR signaling.\",\n      \"evidence\": \"Interaction-trap/yeast two-hybrid identification, co-localization at focal adhesions, GEF activity assays, and co-expression-induced LAR clustering\",\n      \"pmids\": [\"7796809\", \"8643598\", \"9624153\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of clustering on catalytic activity not yet resolved in this period\", \"Whether Trio is a substrate or pure complex partner left open\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Defined in vivo developmental and metabolic roles via mouse knockouts—mammary alveolar differentiation, glucose homeostasis, and cholinergic neuron networks—establishing LAR as physiologically required across tissues.\",\n      \"evidence\": \"Gene-trap and gene-targeted knockout mice with histological, neuroanatomical, and euglycemic-clamp metabolic phenotyping\",\n      \"pmids\": [\"9039657\", \"9245518\", \"9519761\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cell-autonomous vs. systemic contributions not fully separated\", \"Specific substrates underlying each tissue phenotype not identified in these studies\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Established p130Cas as an in vivo substrate whose LAR-mediated dephosphorylation and destabilization drives apoptosis, linking LAR catalysis to cell-death control.\",\n      \"evidence\": \"Overexpression with phosphatase-dead mutants, in vitro dephosphorylation, co-localization, and p130Cas rescue of LAR-induced apoptosis\",\n      \"pmids\": [\"10320483\", \"9501065\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism linking p130Cas destabilization to caspase activation not detailed\", \"Context determining apoptotic vs. signaling outcomes unresolved\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Showed the catalytic cysteine is a redox target irreversibly inactivated by peroxynitrite, identifying a chemical mode of LAR regulation.\",\n      \"evidence\": \"In vitro kinetic phosphatase assays with peroxynitrite, NO donors, GSNO, and DTT reversal tests\",\n      \"pmids\": [\"10486138\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological relevance of peroxynitrite inactivation in cells not established\", \"No demonstration of reversible redox cycling in vivo\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Resolved the proteases and kinase pathways driving regulated LAR processing and intracellular-domain generation, connecting RTK activity to LAR downregulation and \\u03b2-catenin-dependent transcription.\",\n      \"evidence\": \"TACE-knockout fibroblasts, dominant-negative TACE, \\u03b3-secretase and \\u03b1-secretase inhibitors, presenilin-deficient cells, co-IP, and a cyclin D1 reporter\",\n      \"pmids\": [\"16478662\", \"17259169\", \"9245795\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative contribution of LICD to nuclear signaling in vivo unknown\", \"Whether shed ectodomain has independent signaling activity not addressed\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Expanded the LAR substrate/effector network to neurotrophic and migration control—activating Src to transactivate TrkB and reciprocally regulating DAPK with Src—establishing context-dependent pro- and anti-migratory roles.\",\n      \"evidence\": \"LAR-knockout/siRNA neurons, reciprocal co-IP, Src inhibitor PP2, in vitro DAPK dephosphorylation with site mutagenesis, and migration/apoptosis readouts\",\n      \"pmids\": [\"17013927\", \"17803936\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct LAR target site on Src (regulatory tyrosine) inferred but not crystallographically mapped\", \"Switch determining LAR vs. Src dominance over DAPK not fully defined\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identified LAR as a presynaptic trans-synaptic adhesion receptor engaging postsynaptic NGL-3 to induce bidirectional synaptic differentiation, opening LAR's synaptic organizer function.\",\n      \"evidence\": \"Co-culture synaptogenesis assays, heterologous expression, NGL-3 RNAi, soluble-LAR competition, and electrophysiology\",\n      \"pmids\": [\"19252495\", \"15750591\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How synaptic adhesion couples to or operates independently of phosphatase activity not resolved\", \"Endogenous splicing isoform requirements not yet mapped here\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defined a splicing-dependent code for LAR's postsynaptic partner selection (Slitrks, SALM3, HS-neurexins) and mapped the extracellular domains and residues mediating these interactions structurally.\",\n      \"evidence\": \"Domain/point mutagenesis, crystal structures of Ig/FNIII\\u2013ligand complexes, splice-insert requirement analysis, knockout mice, and co-culture synaptogenesis\",\n      \"pmids\": [\"20139422\", \"23345436\", \"26321637\", \"25394468\", \"33037075\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo necessity of individual partners separable from redundancy across LAR-RPTPs not fully dissected\", \"Higher-order assembly seen in crystals not directly visualized at native synapses\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Linked LAR catalytic activity to adhesion and cell-cycle signaling through a c-Abl/Akt/CDK1 axis, and identified EphA2-pY930 as a site-specific substrate uncoupling Nck1 to limit migration.\",\n      \"evidence\": \"Phosphatase-deficient knock-in MEFs with phosphoproteomics and kinase inhibition; siRNA RPTP screen with site-specific EphA2 dephosphorylation and migration assays\",\n      \"pmids\": [\"27352860\", \"23358419\", \"23418360\", \"31799666\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct vs. indirect dephosphorylation steps in the CDK1 axis not fully separated\", \"Transcriptional regulation of PTPRF (miR-24, PPAR\\u03b3) integration with phosphatase output incompletely mapped\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Resolved the structural and functional basis of LAR clustering—a homophilic D1\\u2013D1 interaction stabilized by liprin-\\u03b1 oligomerization that negatively regulates phosphatase activity—unifying scaffolding and catalytic control.\",\n      \"evidence\": \"Crystal structure of LAR D1D2\\u2013liprin-\\u03b13 SAM complex, D1/D1 interface mutagenesis, cellular clustering, and dephosphorylation assays\",\n      \"pmids\": [\"31924785\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether activity-suppressing clustering operates at synapses vs. adhesions not directly compared\", \"Triggers shifting LAR between clustered (low-activity) and dispersed states unknown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Dissociated LAR-RPTP synaptic adhesion from synapse number in vivo—triple knockouts preserve synapse count but selectively impair NMDA receptor-mediated transmission—refining the synaptic role to functional modulation.\",\n      \"evidence\": \"Conditional triple-knockout mice with electrophysiology, superresolution synaptic-cleft localization, and EM of active-zone architecture\",\n      \"pmids\": [\"31985401\", \"33656439\", \"16476662\", \"21430143\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism linking trans-synaptic LAR to NMDA receptor function unresolved\", \"Redundancy among LAR-RPTP family members complicates attributing roles to PTPRF specifically\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How LAR integrates its dual identity—catalytic phosphatase versus phosphatase-independent adhesion organizer—and what switches it between activity states across adhesion, growth-factor, and synaptic contexts remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No unified model of when adhesion engagement modulates catalytic output\", \"In vivo substrate repertoire of PTPRF in distinct tissues incompletely defined\", \"Functional separation of PTPRF from paralogs PTP\\u03c3/PTP\\u03b4 in shared phenotypes still limited\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 4, 21, 28, 31, 37]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [1, 4]},\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [34, 41, 50]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [27, 44]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [7, 19, 52]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3, 13, 19, 45]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [33]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [13, 14]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [33]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [8, 10, 12, 28, 37]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [26, 34, 41, 46, 50]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [18, 21]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [17, 35, 49]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [3, 6, 29, 33]}\n    ],\n    \"complexes\": [\n      \"LAR E-subunit/P-subunit receptor complex\",\n      \"LAR\\u2013liprin-\\u03b1 cluster\"\n    ],\n    \"partners\": [\n      \"PPFIA1/liprin-\\u03b1 (LIP.1)\",\n      \"TRIO\",\n      \"INSR\",\n      \"MET\",\n      \"CASKIN1\",\n      \"NGL-3 (LRRC4B)\",\n      \"SLITRK\",\n      \"NRXN1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}