{"gene":"DLG3","run_date":"2026-06-09T23:54:42","timeline":{"discoveries":[{"year":1996,"finding":"SAP102 interacts in vivo with NMDA receptor complexes: antibodies against NMDA receptors co-immunoprecipitate SAP102 from rat brain synaptosomes, and all three PDZ domains of SAP102 bind the cytoplasmic tail of NR2B in vitro, linking NMDA receptors to the postsynaptic cytomatrix.","method":"Co-immunoprecipitation from rat brain synaptosomes; in vitro binding with recombinant proteins containing NR2B carboxy-terminal tail","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — reciprocal Co-IP and in vitro PDZ-domain binding assays, replicated independently by a second lab in the same year (PMID:8702950)","pmids":["8780649","8702950"],"is_preprint":false},{"year":1996,"finding":"SAP102 specifically interacts with the NMDA receptor complex (but not AMPA receptor subunit GluR1) via the last 20 amino acids of the NR2 subunit C-terminal tail, as demonstrated in cortical synaptic plasma membranes.","method":"Co-immunoprecipitation from cortical synaptic plasma membranes; hexahistidine fusion protein overlay; synthetic peptide interaction assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple in vitro binding methods plus in vivo Co-IP, replicated by concurrent Müller et al. paper","pmids":["8702950"],"is_preprint":false},{"year":1997,"finding":"NE-dlg/SAP102 interacts with the carboxyl-terminal region of the APC tumor suppressor protein, as revealed by yeast two-hybrid screening and in vitro binding assays, and is expressed in non-proliferating neuronal and endocrine cells.","method":"Yeast two-hybrid screening; in vitro binding assay","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two orthogonal methods (yeast two-hybrid + in vitro binding) in a single lab","pmids":["9188857"],"is_preprint":false},{"year":1997,"finding":"SAP102 functionally substitutes for Drosophila DlgA: when expressed in dlg-1 mutant flies, SAP102 suppresses tumor formation and restores synaptic bouton morphology at larval neuromuscular junctions, requiring neuronal expression.","method":"Heterologous expression in Drosophila dlg-1 mutants; morphological analysis of synaptic boutons","journal":"Mechanisms of development","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic complementation in vivo with defined phenotypic readout, single lab","pmids":["9152008"],"is_preprint":false},{"year":1999,"finding":"NE-dlg/SAP102 interacts with calmodulin in a Ca2+-dependent manner (Kd ~44 nM) via a basic alpha-helix region near the SH3 domain, and also interacts with the GUK-like domain of PSD-95/SAP90 in the presence of Ca2+/calmodulin; Ca2+/calmodulin binding does not modulate the PDZ–NR2B interaction.","method":"Surface plasmon resonance; pull-down assay; yeast two-hybrid screening","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — SPR provides quantitative binding constant, complemented by pull-down and two-hybrid, multiple orthogonal methods in single lab","pmids":["10026200"],"is_preprint":false},{"year":1999,"finding":"A novel SAP102-binding protein, p51-nedasin (predominantly the S splice form), interacts with SAP102 in cell bodies and interferes with the association between SAP102 and NMDA receptor NR2B in vitro, suggesting a regulatory role in NMDA receptor clustering at synapses.","method":"Yeast two-hybrid; co-immunoprecipitation; in vitro competition assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and in vitro competition with yeast two-hybrid, single lab, multiple methods","pmids":["10542258"],"is_preprint":false},{"year":2000,"finding":"Overexpression of NE-dlg/SAP102 in cancer cell lines induces growth suppression, impairment of cell adhesion, and downregulation of beta-catenin through an APC-independent pathway; the PDZ domains of NE-dlg are required for these effects.","method":"Overexpression in cancer cell lines; domain deletion analysis; Western blotting for beta-catenin","journal":"International journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function domain analysis with specific phenotypic readout, single lab","pmids":["10797259"],"is_preprint":false},{"year":2001,"finding":"By electron microscopic immunocytochemistry, SAP102 is localized at postsynaptic densities of spines but also diffusely along presynaptic membranes and in axonal cytoplasm of rat visual cortex, suggesting roles in both receptor anchoring at synapses and receptor shuttling between nonsynaptic and synaptic sites.","method":"Electron microscopic immunocytochemistry (quantitative EM-ICC) in rat visual cortex","journal":"Synapse","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct subcellular localization by EM with quantitative analysis, single lab","pmids":["11309840"],"is_preprint":false},{"year":2003,"finding":"The proline-rich regions of Pyk2 bind the SH3 domain of SAP102 (and PSD-95), recruiting Pyk2 to the NMDA receptor complex; the intramolecular SH3–GK domain interaction in SAP102 restricts Pyk2 binding to the SH3 domain, revealed when the GK domain is removed.","method":"Co-immunoprecipitation; pull-down; immunofluorescence co-localization; domain deletion analysis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and pull-down with domain mapping, single lab","pmids":["12576483"],"is_preprint":false},{"year":2005,"finding":"mPins (mammalian partner of inscuteable) interacts with SAP102 and functions in forming the NMDAR-MAGUK complex; mPins enhances trafficking of SAP102 and NMDARs to the plasma membrane, and dominant-negative mPins or siRNA knockdown of mPins decreases SAP102 in dendrites and reduces NMDAR surface expression.","method":"Co-immunoprecipitation; siRNA knockdown; dominant-negative expression; surface expression assays in neurons","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — Co-IP with functional siRNA knockdown and dominant-negative phenotype in neurons, multiple orthogonal methods","pmids":["16299499"],"is_preprint":false},{"year":2008,"finding":"SAP102 mediates synaptic trafficking of both AMPA and NMDA receptors during synaptogenesis; after synaptogenesis, PSD-95 assumes these functions. This temporal division was established by in utero electroporation with dual whole-cell electrophysiology at two developmental stages.","method":"In utero electroporation; dual whole-cell patch-clamp electrophysiology at distinct developmental stages; knockout mice","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetic manipulation with direct electrophysiological readout, independently consistent with PSD-95/PSD-93 double-KO data","pmids":["19104036"],"is_preprint":false},{"year":2011,"finding":"SAP102 contains a novel N-terminal NMDA receptor binding site specific for NR2B that is PDZ-domain independent and is regulated by alternative splicing; the N-terminal insert splice variant promotes dendritic spine lengthening and synapse formation at long spines, and blocking NMDA receptor activity prevents this spine lengthening.","method":"Co-immunoprecipitation; domain mapping; shRNA knockdown; morphological analysis of dendritic spines; pharmacological NMDA receptor blockade","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Moderate — Co-IP domain mapping combined with shRNA KD and morphological phenotype, multiple orthogonal methods in single lab","pmids":["21209193"],"is_preprint":false},{"year":2011,"finding":"Dlg3 contributes to apical-basal polarity and tight junction formation in polarized epithelial cells; Dlg3 recruits E3 ubiquitin ligases Nedd4 and Nedd4-2 through its PPxY motifs, leading to Dlg3 monoubiquitination, apical membrane recruitment, and tight junction consolidation.","method":"Affinity purification/mass spectrometry of Dlg3 complexes; co-immunoprecipitation; mouse knockout; immunofluorescence; ubiquitination assays","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — AP-MS complex purification + Co-IP + KO mouse + ubiquitination biochemistry, multiple orthogonal methods","pmids":["21920314"],"is_preprint":false},{"year":2011,"finding":"SAP102 PDZ domain ligand-binding is not essential for its own synaptic clustering; however, direct PDZ-mediated binding of NMDARs to SAP102 is required for efficient synaptic targeting of NMDA receptor subunits GluN2A and GluN2B.","method":"Expression of SAP102 PDZ-binding-deficient mutants in hippocampal neurons; co-expression with GluN2A/GluN2B; synaptic clustering analysis","journal":"Neuroscience letters","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — single lab, single primary method (mutant expression + imaging), clear mechanistic conclusion","pmids":["23178474"],"is_preprint":false},{"year":2012,"finding":"SAP102 mediates synaptic clearance of GluN2B-containing NMDARs through a secondary non-PDZ interaction; two critical residues on GluN2B responsible for non-PDZ binding to SAP102 were identified, and mutation of these residues or SAP102 knockdown rescues defective surface/synaptic expression of PDZ-binding-deficient GluN2B.","method":"Mutagenesis of GluN2B residues; SAP102 siRNA knockdown; surface biotinylation; electrophysiology","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — site-directed mutagenesis combined with knockdown and surface expression assays, multiple orthogonal methods","pmids":["23103165"],"is_preprint":false},{"year":2012,"finding":"SAP102 binds to the C-terminal part of neurobeachin (Nbea) containing the DUF, PH, BEACH, and WD40 domains; a mutation in Nbea's PH domain that disrupts its PH-BEACH interaction abolishes SAP102 binding.","method":"Mass spectrometry identification from mouse brain; co-immunoprecipitation in heterologous cells; domain mapping with mutations","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS discovery + heterologous Co-IP + domain mutagenesis, single lab","pmids":["22745750"],"is_preprint":false},{"year":2013,"finding":"SAP102 regulates cortical synapse development through EphB and PAK signaling: SAP102 co-immunoprecipitates EphB2 and Kalirin-7 in neonatal cortex; SAP102 knockdown reduces EphB surface expression, prevents actin reorganization and synapse formation in response to ephrinB, and downregulates PAK activity.","method":"Lentivirus shRNA knockdown; co-immunoprecipitation; surface expression analysis; EphB activation assays; actin cytoskeleton analysis","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Moderate — Co-IP + shRNA KD with multiple downstream phenotypic readouts (actin, AMPAR, PAK), multiple orthogonal methods in single lab","pmids":["23486974"],"is_preprint":false},{"year":2014,"finding":"SAP102 interacts with the A2A adenosine receptor C-terminus (via the SH3 and GK domains of SAP102); SAP102 overexpression prevents the A2A receptor from accessing a compartment with restricted (slow) mobility, dependent on a DVELL motif in the A2A receptor C-terminus.","method":"Single particle tracking (quantum dot); co-immunoprecipitation; hidden Markov model analysis of diffusion; dominant-negative fragment expression","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus single-particle tracking with domain-specific mutant, single lab","pmids":["24509856"],"is_preprint":false},{"year":2015,"finding":"Synaptic localization of SAP102 is regulated by C-terminal alternative splicing: the I2 splice variant (insert between SH3 and GK domains) is highly enriched at dendritic spines and is developmentally regulated; knockdown of I2-containing SAP102 isoforms differentially affects NMDAR surface expression in a subunit-specific manner.","method":"Expression of splice variant constructs; shRNA knockdown of specific isoforms; surface biotinylation; spine morphology analysis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — isoform-specific knockdown with surface expression readout, single lab","pmids":["25555912"],"is_preprint":false},{"year":2017,"finding":"SAP102 synaptic targeting is regulated by phosphorylation at serine 632 by casein kinase II (CK2): Ser632 phosphorylation increases synaptic enrichment of SAP102 and decreases its mobility; elevation of synaptic activity suppresses Ser632 phosphorylation and reduces synaptic enrichment.","method":"In vitro kinase assay; phospho-specific analysis in heterologous cells and neurons; FRAP; activity manipulation","journal":"Molecular neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro and in-neuron phosphorylation with FRAP mobility assay, single lab","pmids":["29282697"],"is_preprint":false},{"year":2018,"finding":"SAP102 regulates synaptic AMPAR function through a CNIH-2 (cornichon-2)-dependent mechanism: SAP102 rescues AMPAR eEPSCs and increases AMPAR mEPSC decay time upon PSD-95 knockdown, and this rescue requires the AMPAR auxiliary subunit cornichon-2.","method":"Molecular replacement (shRNA KD of PSD-95 + SAP102 expression); whole-cell patch-clamp electrophysiology; cornichon-2 knockdown","journal":"Journal of neurophysiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — electrophysiology with molecular replacement strategy and auxiliary subunit manipulation, single lab","pmids":["30067114"],"is_preprint":false},{"year":2020,"finding":"MIAT lncRNA promotes methylation of CpG islands in the DLG3 promoter by binding to DNMT1, DNMT3A, and DNMT3B, suppressing DLG3 expression; DLG3 binds MST2 and regulates LATS1, preventing nuclear translocation of YAP to activate the Hippo pathway in breast cancer cells.","method":"MS-PCR; RIP assay; dual luciferase reporter; siRNA knockdown; co-immunoprecipitation; in vivo tumor models","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple methods (RIP, Co-IP, reporter, in vivo), single lab; note this is in cancer context not neurons","pmids":["32593652"],"is_preprint":false},{"year":2023,"finding":"COP1 E3 ubiquitin ligase binds DLG3 protein and enhances its ubiquitination, promoting glioma cell proliferation, invasion, and migration; DLG3 silencing reverses the inhibitory effect of COP1 knockdown.","method":"Co-immunoprecipitation; ubiquitination assay (MG132 treatment); siRNA knockdown; CCK-8, EdU, Transwell assays","journal":"Neurological research","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — Co-IP + ubiquitination assay + rescue experiment, single lab, single paper","pmids":["37356109"],"is_preprint":false},{"year":2023,"finding":"Sec8 (exocyst subunit) preferentially binds PDZ2 over PDZ1 and PDZ3 of SAP102 via its C-terminal ITTV motif; a 14-residue 'spacer' bridging ITTV to the Sec8 core is essential, as its deletion abolishes SAP102 binding.","method":"2.5 Å crystal structure of Sec8 C-terminus; in vitro binding assays; domain deletion analysis; molecular modeling","journal":"Frontiers in cell and developmental biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure plus biochemical binding assays with domain deletion mutagenesis, single lab but structural validation","pmids":["37849738"],"is_preprint":false},{"year":2024,"finding":"JNK3 directly phosphorylates SAP102, negatively regulating its synaptic dynamics; JNK activity modulates SAP102 and kainate receptor subunit GluK2 surface expression and trafficking to postsynaptic sites in a neuronal context.","method":"In vitro phosphorylation assay; live-cell imaging; pharmacological JNK inhibition; surface expression assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro kinase assay + live imaging + pharmacology, single lab","pmids":["38582451"],"is_preprint":false},{"year":2024,"finding":"SAP102 accumulates in high-density subsynaptic nanoclusters that are smaller and denser than PSD-95 nanoclusters; only a subset of SAP102 nanoclusters co-organize with PSD-95, revealing distinct MAGUK nanodomains within individual synapses that differentially associate with the presynaptic release protein Munc13-1.","method":"DNA-PAINT super-resolution microscopy in cultured rat neurons","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — super-resolution imaging with quantitative nanocluster analysis, single lab","pmids":["38777601"],"is_preprint":false},{"year":2016,"finding":"Genetic deletion of SAP102 (Dlg3 knockout) in mice reduces the number of thalamocortical axons innervating the somatosensory cortex, causes a transient speeding of NMDA receptor kinetics during the critical period without reducing GluN2B-mediated transmission, and reduces divergence of TC connectivity after the critical period.","method":"Dlg3 knockout mouse; in vivo and in vitro electrophysiology; axon quantification","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 / Moderate — KO mouse with direct electrophysiological and anatomical readouts, multiple phenotypic measures","pmids":["27466188"],"is_preprint":false},{"year":2016,"finding":"A 5' UTR duplication variant in DLG3 (dupG, 7 nt upstream of the start codon) attenuates protein translation without affecting mRNA levels, causing intellectual disability; demonstrated by dual luciferase reporter assay and reduced protein in patient blood cells.","method":"Dual luciferase reporter assay; Western blot of patient-derived cells; mRNA level analysis","journal":"European journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reporter assay + patient-derived cell validation, two orthogonal methods, single lab","pmids":["27222290"],"is_preprint":false}],"current_model":"DLG3/SAP102 is a postsynaptic MAGUK scaffold protein that links NMDA receptors (via PDZ-domain binding to the NR2B C-terminal tail and a secondary non-PDZ N-terminal interaction) to the submembraneous cytomatrix at excitatory synapses; it mediates developmental trafficking of AMPA and NMDA receptors during synaptogenesis, regulates dendritic spine morphology through NMDA receptor–dependent and alternative-splicing–controlled mechanisms, recruits signaling molecules including Pyk2 (via its SH3 domain), mPins (a G-protein regulator), EphB2/Kalirin-7 (linking to PAK and actin remodeling), JNK3 (which phosphorylates SAP102 to control its synaptic mobility), and the exocyst subunit Sec8 (preferentially to PDZ2); its synaptic targeting is further regulated by CK2-mediated phosphorylation at Ser632 and by C-terminal alternative splicing; in epithelial cells it recruits Nedd4/Nedd4-2 E3 ligases via PPxY motifs to undergo monoubiquitination required for apical membrane recruitment and tight junction formation, while in cancer contexts COP1 ubiquitinates DLG3 to promote tumor cell proliferation."},"narrative":{"mechanistic_narrative":"DLG3/SAP102 is a postsynaptic MAGUK scaffold that links NMDA receptors to the submembranous cytomatrix at excitatory synapses, coordinating receptor trafficking and dendritic spine remodeling during synaptogenesis [PMID:8780649, PMID:8702950, PMID:19104036]. It binds the C-terminal tail of the NR2/GluN2 subunit through its PDZ domains and recognizes GluN2B through a second, PDZ-independent N-terminal site, and this dual mode of engagement governs both synaptic targeting and synaptic clearance of GluN2B-containing receptors [PMID:8702950, PMID:21209193, PMID:23103165]. SAP102 mediates synaptic delivery of AMPA and NMDA receptors selectively during early development, after which PSD-95 assumes these functions, and it can sustain AMPAR transmission through a cornichon-2–dependent mechanism [PMID:19104036, PMID:30067114]. Beyond receptor anchoring, SAP102 nucleates a signaling platform: it recruits Pyk2 and the A2A adenosine receptor through its SH3/GK module, mPins to promote NMDAR surface delivery, EphB2/Kalirin-7 to drive PAK-dependent actin reorganization and synapse formation, and the exocyst subunit Sec8 preferentially via PDZ2 [PMID:12576483, PMID:16299499, PMID:23486974, PMID:24509856, PMID:37849738]. Its synaptic enrichment and mobility are tuned by CK2 phosphorylation at Ser632 and by JNK3 phosphorylation, and by C-terminal alternative splicing that generates spine-enriched isoforms [PMID:21209193, PMID:25555912, PMID:29282697, PMID:38582451]. In polarized epithelia DLG3 recruits the Nedd4/Nedd4-2 E3 ligases via PPxY motifs to drive its own monoubiquitination, apical recruitment and tight-junction formation, while in cancer it engages MST2/LATS1 Hippo signaling and is regulated by COP1-mediated ubiquitination [PMID:21920314, PMID:32593652, PMID:37356109]. Loss-of-function variants in DLG3, including a 5'UTR duplication that attenuates translation, cause intellectual disability [PMID:27222290].","teleology":[{"year":1996,"claim":"Established that SAP102 is a bona fide NMDA receptor-associated scaffold, defining the founding molecular interaction that placed it at the postsynaptic cytomatrix.","evidence":"Reciprocal co-immunoprecipitation from rat brain synaptosomes and cortical synaptic membranes plus in vitro PDZ-domain binding to the NR2B C-terminal tail","pmids":["8780649","8702950"],"confidence":"High","gaps":["Did not establish functional consequence of the interaction in vivo","Did not resolve which PDZ domain dominates binding in cells"]},{"year":1997,"claim":"Showed SAP102 has functions beyond receptor anchoring by linking it to the APC tumor suppressor and demonstrating cross-species functional conservation with Drosophila Dlg.","evidence":"Yeast two-hybrid and in vitro binding to APC; heterologous rescue of dlg-1 mutant flies","pmids":["9188857","9152008"],"confidence":"Medium","gaps":["APC interaction not validated in mammalian neurons","Mechanism of tumor/bouton rescue not resolved at the molecular level"]},{"year":1999,"claim":"Identified Ca2+/calmodulin and p51-nedasin as regulators that can modulate SAP102 interactions, introducing the idea that NMDAR clustering by SAP102 is dynamically controlled.","evidence":"Surface plasmon resonance, pull-down, yeast two-hybrid, and in vitro competition assays","pmids":["10026200","10542258"],"confidence":"Medium","gaps":["Regulatory effects shown largely in vitro","Physiological calmodulin-dependent switching not demonstrated at synapses"]},{"year":2000,"claim":"Demonstrated a PDZ-dependent growth-suppressive and adhesion-regulating role for SAP102 in non-neuronal cells, extending its function to cell polarity and proliferation control.","evidence":"Overexpression and domain-deletion analysis in cancer cell lines with beta-catenin readout","pmids":["10797259"],"confidence":"Medium","gaps":["Overexpression system may not reflect endogenous role","APC-independent pathway not molecularly defined"]},{"year":2005,"claim":"Defined mPins as a trafficking partner that drives SAP102 and NMDAR delivery to the membrane, linking the scaffold to G-protein regulatory machinery.","evidence":"Co-IP, siRNA knockdown, dominant-negative expression and surface assays in neurons","pmids":["16299499"],"confidence":"High","gaps":["Step in the secretory/trafficking pathway not pinpointed","Relationship to PDZ-mediated NMDAR binding not resolved"]},{"year":2008,"claim":"Resolved the developmental logic of MAGUK function by showing SAP102 mediates AMPA/NMDA receptor trafficking during synaptogenesis before PSD-95 takes over.","evidence":"In utero electroporation with dual whole-cell electrophysiology at distinct developmental stages in knockout mice","pmids":["19104036"],"confidence":"High","gaps":["Molecular basis of the developmental hand-off to PSD-95 unknown","Does not define which interactions drive AMPAR versus NMDAR trafficking"]},{"year":2011,"claim":"Uncovered a PDZ-independent N-terminal GluN2B binding site under alternative-splicing control that shapes spine morphology, and showed PDZ binding is required for receptor targeting but not SAP102 clustering itself.","evidence":"Co-IP domain mapping, shRNA knockdown, spine morphology and pharmacological NMDAR blockade; PDZ-mutant expression in neurons","pmids":["21209193","23178474"],"confidence":"High","gaps":["How the N-terminal site and PDZ binding are coordinated is unclear","Splicing regulation upstream signals not identified"]},{"year":2011,"claim":"Established a non-neuronal mechanism whereby DLG3 recruits Nedd4/Nedd4-2 via PPxY motifs to undergo monoubiquitination required for apical membrane recruitment and tight-junction formation.","evidence":"AP-MS, co-IP, knockout mouse, immunofluorescence and ubiquitination assays in polarized epithelia","pmids":["21920314"],"confidence":"High","gaps":["Whether ubiquitin-dependent targeting operates in neurons is unknown","Deubiquitinase counterpart not identified"]},{"year":2012,"claim":"Showed the secondary non-PDZ interaction mediates synaptic clearance of GluN2B receptors and identified the GluN2B residues responsible, defining a dual binding/clearance mechanism.","evidence":"GluN2B mutagenesis, SAP102 knockdown, surface biotinylation and electrophysiology; plus neurobeachin domain-mapping interaction","pmids":["23103165","22745750"],"confidence":"High","gaps":["Trafficking machinery executing clearance not defined","Functional role of neurobeachin binding not established"]},{"year":2013,"claim":"Connected SAP102 to EphB/PAK signaling and actin remodeling, showing it is required for ephrinB-driven synapse formation in developing cortex.","evidence":"shRNA knockdown, co-IP of EphB2/Kalirin-7, surface expression, EphB activation and actin analyses","pmids":["23486974"],"confidence":"High","gaps":["Direct versus indirect EphB2 binding not distinguished","Link between actin remodeling and receptor trafficking not integrated"]},{"year":2016,"claim":"Defined in vivo developmental roles via knockout and linked DLG3 to human intellectual disability through a translation-attenuating 5'UTR variant.","evidence":"Dlg3 knockout mouse electrophysiology and axon quantification; dual luciferase reporter and patient-cell Western blot","pmids":["27466188","27222290"],"confidence":"High","gaps":["Cellular mechanism linking reduced SAP102 to cognitive deficit unresolved","KO phenotypes are subtle, indicating redundancy with other MAGUKs"]},{"year":2018,"claim":"Identified cornichon-2 as the auxiliary subunit required for SAP102 to rescue AMPAR transmission, refining the MAGUK-AMPAR functional link.","evidence":"Molecular replacement of PSD-95, whole-cell electrophysiology and cornichon-2 knockdown","pmids":["30067114"],"confidence":"Medium","gaps":["Direct SAP102–CNIH-2 binding not demonstrated","Physiological relevance outside replacement paradigm unclear"]},{"year":2024,"claim":"Consolidated post-translational and structural control of SAP102 synaptic dynamics through CK2/JNK3 phosphorylation, splice-variant enrichment, Sec8/PDZ2 binding, and distinct subsynaptic nanocluster organization.","evidence":"In vitro kinase/FRAP/live-imaging assays; isoform knockdown; Sec8 crystal structure with binding assays; DNA-PAINT super-resolution","pmids":["29282697","38582451","25555912","37849738","38777601"],"confidence":"Medium","gaps":["How phosphorylation, splicing and nanocluster positioning integrate is unknown","Functional consequence of SAP102-specific nanodomains not established"]},{"year":2023,"claim":"Extended DLG3 into cancer signaling, implicating it in Hippo-pathway control and COP1-mediated ubiquitination affecting tumor cell proliferation.","evidence":"RIP, co-IP, luciferase reporter, ubiquitination assays and in vivo tumor/proliferation models in breast cancer and glioma cells","pmids":["32593652","37356109"],"confidence":"Medium","gaps":["Whether MST2/Hippo and COP1 roles operate in neurons is unknown","Direct DLG3–MST2 binding interface not mapped"]},{"year":null,"claim":"How the multiple regulatory layers (phosphorylation, ubiquitination, alternative splicing, nanocluster positioning) are integrated to control SAP102 function in vivo, and how this maps onto cognitive phenotypes, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model linking PTMs and splicing to physiological output","Mechanism connecting SAP102 loss to intellectual disability undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,9,16,23]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[9,12]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[7]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,10,16]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[10,12,26]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[16,21]}],"complexes":["NMDA receptor–MAGUK complex","exocyst (via Sec8)"],"partners":["GRIN2B","DLG4","PTK2B","GPSM2","EPHB2","KALRN","EXOC4","NEDD4"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q92796","full_name":"Disks large homolog 3","aliases":["Neuroendocrine-DLG","Synapse-associated protein 102","SAP-102","SAP102","XLMR"],"length_aa":817,"mass_kda":90.3,"function":"Required for learning most likely through its role in synaptic plasticity following NMDA receptor signaling","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q92796/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/DLG3","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/DLG3","total_profiled":1310},"omim":[{"mim_id":"612808","title":"LEUCINE-RICH REPEAT AND FIBRONECTIN TYPE III DOMAIN-CONTAINING PROTEIN 2; LRFN2","url":"https://www.omim.org/entry/612808"},{"mim_id":"609743","title":"CELL ADHESION MOLECULE 3; CADM3","url":"https://www.omim.org/entry/609743"},{"mim_id":"609425","title":"CHROMOSOME 3q29 DELETION SYNDROME","url":"https://www.omim.org/entry/609425"},{"mim_id":"605022","title":"p21 PROTEIN-ACTIVATED KINASE 2; PAK2","url":"https://www.omim.org/entry/605022"},{"mim_id":"601114","title":"MEMBRANE PROTEIN, PALMITOYLATED 3; MPP3","url":"https://www.omim.org/entry/601114"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Nucleoli","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in 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from rat brain synaptosomes; in vitro binding with recombinant proteins containing NR2B carboxy-terminal tail\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — reciprocal Co-IP and in vitro PDZ-domain binding assays, replicated independently by a second lab in the same year (PMID:8702950)\",\n      \"pmids\": [\"8780649\", \"8702950\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"SAP102 specifically interacts with the NMDA receptor complex (but not AMPA receptor subunit GluR1) via the last 20 amino acids of the NR2 subunit C-terminal tail, as demonstrated in cortical synaptic plasma membranes.\",\n      \"method\": \"Co-immunoprecipitation from cortical synaptic plasma membranes; hexahistidine fusion protein overlay; synthetic peptide interaction assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple in vitro binding methods plus in vivo Co-IP, replicated by concurrent Müller et al. paper\",\n      \"pmids\": [\"8702950\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"NE-dlg/SAP102 interacts with the carboxyl-terminal region of the APC tumor suppressor protein, as revealed by yeast two-hybrid screening and in vitro binding assays, and is expressed in non-proliferating neuronal and endocrine cells.\",\n      \"method\": \"Yeast two-hybrid screening; in vitro binding assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two orthogonal methods (yeast two-hybrid + in vitro binding) in a single lab\",\n      \"pmids\": [\"9188857\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"SAP102 functionally substitutes for Drosophila DlgA: when expressed in dlg-1 mutant flies, SAP102 suppresses tumor formation and restores synaptic bouton morphology at larval neuromuscular junctions, requiring neuronal expression.\",\n      \"method\": \"Heterologous expression in Drosophila dlg-1 mutants; morphological analysis of synaptic boutons\",\n      \"journal\": \"Mechanisms of development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic complementation in vivo with defined phenotypic readout, single lab\",\n      \"pmids\": [\"9152008\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"NE-dlg/SAP102 interacts with calmodulin in a Ca2+-dependent manner (Kd ~44 nM) via a basic alpha-helix region near the SH3 domain, and also interacts with the GUK-like domain of PSD-95/SAP90 in the presence of Ca2+/calmodulin; Ca2+/calmodulin binding does not modulate the PDZ–NR2B interaction.\",\n      \"method\": \"Surface plasmon resonance; pull-down assay; yeast two-hybrid screening\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — SPR provides quantitative binding constant, complemented by pull-down and two-hybrid, multiple orthogonal methods in single lab\",\n      \"pmids\": [\"10026200\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"A novel SAP102-binding protein, p51-nedasin (predominantly the S splice form), interacts with SAP102 in cell bodies and interferes with the association between SAP102 and NMDA receptor NR2B in vitro, suggesting a regulatory role in NMDA receptor clustering at synapses.\",\n      \"method\": \"Yeast two-hybrid; co-immunoprecipitation; in vitro competition assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and in vitro competition with yeast two-hybrid, single lab, multiple methods\",\n      \"pmids\": [\"10542258\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Overexpression of NE-dlg/SAP102 in cancer cell lines induces growth suppression, impairment of cell adhesion, and downregulation of beta-catenin through an APC-independent pathway; the PDZ domains of NE-dlg are required for these effects.\",\n      \"method\": \"Overexpression in cancer cell lines; domain deletion analysis; Western blotting for beta-catenin\",\n      \"journal\": \"International journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function domain analysis with specific phenotypic readout, single lab\",\n      \"pmids\": [\"10797259\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"By electron microscopic immunocytochemistry, SAP102 is localized at postsynaptic densities of spines but also diffusely along presynaptic membranes and in axonal cytoplasm of rat visual cortex, suggesting roles in both receptor anchoring at synapses and receptor shuttling between nonsynaptic and synaptic sites.\",\n      \"method\": \"Electron microscopic immunocytochemistry (quantitative EM-ICC) in rat visual cortex\",\n      \"journal\": \"Synapse\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct subcellular localization by EM with quantitative analysis, single lab\",\n      \"pmids\": [\"11309840\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The proline-rich regions of Pyk2 bind the SH3 domain of SAP102 (and PSD-95), recruiting Pyk2 to the NMDA receptor complex; the intramolecular SH3–GK domain interaction in SAP102 restricts Pyk2 binding to the SH3 domain, revealed when the GK domain is removed.\",\n      \"method\": \"Co-immunoprecipitation; pull-down; immunofluorescence co-localization; domain deletion analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and pull-down with domain mapping, single lab\",\n      \"pmids\": [\"12576483\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"mPins (mammalian partner of inscuteable) interacts with SAP102 and functions in forming the NMDAR-MAGUK complex; mPins enhances trafficking of SAP102 and NMDARs to the plasma membrane, and dominant-negative mPins or siRNA knockdown of mPins decreases SAP102 in dendrites and reduces NMDAR surface expression.\",\n      \"method\": \"Co-immunoprecipitation; siRNA knockdown; dominant-negative expression; surface expression assays in neurons\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with functional siRNA knockdown and dominant-negative phenotype in neurons, multiple orthogonal methods\",\n      \"pmids\": [\"16299499\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"SAP102 mediates synaptic trafficking of both AMPA and NMDA receptors during synaptogenesis; after synaptogenesis, PSD-95 assumes these functions. This temporal division was established by in utero electroporation with dual whole-cell electrophysiology at two developmental stages.\",\n      \"method\": \"In utero electroporation; dual whole-cell patch-clamp electrophysiology at distinct developmental stages; knockout mice\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetic manipulation with direct electrophysiological readout, independently consistent with PSD-95/PSD-93 double-KO data\",\n      \"pmids\": [\"19104036\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"SAP102 contains a novel N-terminal NMDA receptor binding site specific for NR2B that is PDZ-domain independent and is regulated by alternative splicing; the N-terminal insert splice variant promotes dendritic spine lengthening and synapse formation at long spines, and blocking NMDA receptor activity prevents this spine lengthening.\",\n      \"method\": \"Co-immunoprecipitation; domain mapping; shRNA knockdown; morphological analysis of dendritic spines; pharmacological NMDA receptor blockade\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP domain mapping combined with shRNA KD and morphological phenotype, multiple orthogonal methods in single lab\",\n      \"pmids\": [\"21209193\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Dlg3 contributes to apical-basal polarity and tight junction formation in polarized epithelial cells; Dlg3 recruits E3 ubiquitin ligases Nedd4 and Nedd4-2 through its PPxY motifs, leading to Dlg3 monoubiquitination, apical membrane recruitment, and tight junction consolidation.\",\n      \"method\": \"Affinity purification/mass spectrometry of Dlg3 complexes; co-immunoprecipitation; mouse knockout; immunofluorescence; ubiquitination assays\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — AP-MS complex purification + Co-IP + KO mouse + ubiquitination biochemistry, multiple orthogonal methods\",\n      \"pmids\": [\"21920314\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"SAP102 PDZ domain ligand-binding is not essential for its own synaptic clustering; however, direct PDZ-mediated binding of NMDARs to SAP102 is required for efficient synaptic targeting of NMDA receptor subunits GluN2A and GluN2B.\",\n      \"method\": \"Expression of SAP102 PDZ-binding-deficient mutants in hippocampal neurons; co-expression with GluN2A/GluN2B; synaptic clustering analysis\",\n      \"journal\": \"Neuroscience letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — single lab, single primary method (mutant expression + imaging), clear mechanistic conclusion\",\n      \"pmids\": [\"23178474\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"SAP102 mediates synaptic clearance of GluN2B-containing NMDARs through a secondary non-PDZ interaction; two critical residues on GluN2B responsible for non-PDZ binding to SAP102 were identified, and mutation of these residues or SAP102 knockdown rescues defective surface/synaptic expression of PDZ-binding-deficient GluN2B.\",\n      \"method\": \"Mutagenesis of GluN2B residues; SAP102 siRNA knockdown; surface biotinylation; electrophysiology\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — site-directed mutagenesis combined with knockdown and surface expression assays, multiple orthogonal methods\",\n      \"pmids\": [\"23103165\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"SAP102 binds to the C-terminal part of neurobeachin (Nbea) containing the DUF, PH, BEACH, and WD40 domains; a mutation in Nbea's PH domain that disrupts its PH-BEACH interaction abolishes SAP102 binding.\",\n      \"method\": \"Mass spectrometry identification from mouse brain; co-immunoprecipitation in heterologous cells; domain mapping with mutations\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS discovery + heterologous Co-IP + domain mutagenesis, single lab\",\n      \"pmids\": [\"22745750\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"SAP102 regulates cortical synapse development through EphB and PAK signaling: SAP102 co-immunoprecipitates EphB2 and Kalirin-7 in neonatal cortex; SAP102 knockdown reduces EphB surface expression, prevents actin reorganization and synapse formation in response to ephrinB, and downregulates PAK activity.\",\n      \"method\": \"Lentivirus shRNA knockdown; co-immunoprecipitation; surface expression analysis; EphB activation assays; actin cytoskeleton analysis\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP + shRNA KD with multiple downstream phenotypic readouts (actin, AMPAR, PAK), multiple orthogonal methods in single lab\",\n      \"pmids\": [\"23486974\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"SAP102 interacts with the A2A adenosine receptor C-terminus (via the SH3 and GK domains of SAP102); SAP102 overexpression prevents the A2A receptor from accessing a compartment with restricted (slow) mobility, dependent on a DVELL motif in the A2A receptor C-terminus.\",\n      \"method\": \"Single particle tracking (quantum dot); co-immunoprecipitation; hidden Markov model analysis of diffusion; dominant-negative fragment expression\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus single-particle tracking with domain-specific mutant, single lab\",\n      \"pmids\": [\"24509856\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Synaptic localization of SAP102 is regulated by C-terminal alternative splicing: the I2 splice variant (insert between SH3 and GK domains) is highly enriched at dendritic spines and is developmentally regulated; knockdown of I2-containing SAP102 isoforms differentially affects NMDAR surface expression in a subunit-specific manner.\",\n      \"method\": \"Expression of splice variant constructs; shRNA knockdown of specific isoforms; surface biotinylation; spine morphology analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — isoform-specific knockdown with surface expression readout, single lab\",\n      \"pmids\": [\"25555912\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"SAP102 synaptic targeting is regulated by phosphorylation at serine 632 by casein kinase II (CK2): Ser632 phosphorylation increases synaptic enrichment of SAP102 and decreases its mobility; elevation of synaptic activity suppresses Ser632 phosphorylation and reduces synaptic enrichment.\",\n      \"method\": \"In vitro kinase assay; phospho-specific analysis in heterologous cells and neurons; FRAP; activity manipulation\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro and in-neuron phosphorylation with FRAP mobility assay, single lab\",\n      \"pmids\": [\"29282697\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"SAP102 regulates synaptic AMPAR function through a CNIH-2 (cornichon-2)-dependent mechanism: SAP102 rescues AMPAR eEPSCs and increases AMPAR mEPSC decay time upon PSD-95 knockdown, and this rescue requires the AMPAR auxiliary subunit cornichon-2.\",\n      \"method\": \"Molecular replacement (shRNA KD of PSD-95 + SAP102 expression); whole-cell patch-clamp electrophysiology; cornichon-2 knockdown\",\n      \"journal\": \"Journal of neurophysiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — electrophysiology with molecular replacement strategy and auxiliary subunit manipulation, single lab\",\n      \"pmids\": [\"30067114\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"MIAT lncRNA promotes methylation of CpG islands in the DLG3 promoter by binding to DNMT1, DNMT3A, and DNMT3B, suppressing DLG3 expression; DLG3 binds MST2 and regulates LATS1, preventing nuclear translocation of YAP to activate the Hippo pathway in breast cancer cells.\",\n      \"method\": \"MS-PCR; RIP assay; dual luciferase reporter; siRNA knockdown; co-immunoprecipitation; in vivo tumor models\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple methods (RIP, Co-IP, reporter, in vivo), single lab; note this is in cancer context not neurons\",\n      \"pmids\": [\"32593652\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"COP1 E3 ubiquitin ligase binds DLG3 protein and enhances its ubiquitination, promoting glioma cell proliferation, invasion, and migration; DLG3 silencing reverses the inhibitory effect of COP1 knockdown.\",\n      \"method\": \"Co-immunoprecipitation; ubiquitination assay (MG132 treatment); siRNA knockdown; CCK-8, EdU, Transwell assays\",\n      \"journal\": \"Neurological research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — Co-IP + ubiquitination assay + rescue experiment, single lab, single paper\",\n      \"pmids\": [\"37356109\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Sec8 (exocyst subunit) preferentially binds PDZ2 over PDZ1 and PDZ3 of SAP102 via its C-terminal ITTV motif; a 14-residue 'spacer' bridging ITTV to the Sec8 core is essential, as its deletion abolishes SAP102 binding.\",\n      \"method\": \"2.5 Å crystal structure of Sec8 C-terminus; in vitro binding assays; domain deletion analysis; molecular modeling\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure plus biochemical binding assays with domain deletion mutagenesis, single lab but structural validation\",\n      \"pmids\": [\"37849738\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"JNK3 directly phosphorylates SAP102, negatively regulating its synaptic dynamics; JNK activity modulates SAP102 and kainate receptor subunit GluK2 surface expression and trafficking to postsynaptic sites in a neuronal context.\",\n      \"method\": \"In vitro phosphorylation assay; live-cell imaging; pharmacological JNK inhibition; surface expression assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro kinase assay + live imaging + pharmacology, single lab\",\n      \"pmids\": [\"38582451\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"SAP102 accumulates in high-density subsynaptic nanoclusters that are smaller and denser than PSD-95 nanoclusters; only a subset of SAP102 nanoclusters co-organize with PSD-95, revealing distinct MAGUK nanodomains within individual synapses that differentially associate with the presynaptic release protein Munc13-1.\",\n      \"method\": \"DNA-PAINT super-resolution microscopy in cultured rat neurons\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — super-resolution imaging with quantitative nanocluster analysis, single lab\",\n      \"pmids\": [\"38777601\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Genetic deletion of SAP102 (Dlg3 knockout) in mice reduces the number of thalamocortical axons innervating the somatosensory cortex, causes a transient speeding of NMDA receptor kinetics during the critical period without reducing GluN2B-mediated transmission, and reduces divergence of TC connectivity after the critical period.\",\n      \"method\": \"Dlg3 knockout mouse; in vivo and in vitro electrophysiology; axon quantification\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mouse with direct electrophysiological and anatomical readouts, multiple phenotypic measures\",\n      \"pmids\": [\"27466188\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"A 5' UTR duplication variant in DLG3 (dupG, 7 nt upstream of the start codon) attenuates protein translation without affecting mRNA levels, causing intellectual disability; demonstrated by dual luciferase reporter assay and reduced protein in patient blood cells.\",\n      \"method\": \"Dual luciferase reporter assay; Western blot of patient-derived cells; mRNA level analysis\",\n      \"journal\": \"European journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reporter assay + patient-derived cell validation, two orthogonal methods, single lab\",\n      \"pmids\": [\"27222290\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"DLG3/SAP102 is a postsynaptic MAGUK scaffold protein that links NMDA receptors (via PDZ-domain binding to the NR2B C-terminal tail and a secondary non-PDZ N-terminal interaction) to the submembraneous cytomatrix at excitatory synapses; it mediates developmental trafficking of AMPA and NMDA receptors during synaptogenesis, regulates dendritic spine morphology through NMDA receptor–dependent and alternative-splicing–controlled mechanisms, recruits signaling molecules including Pyk2 (via its SH3 domain), mPins (a G-protein regulator), EphB2/Kalirin-7 (linking to PAK and actin remodeling), JNK3 (which phosphorylates SAP102 to control its synaptic mobility), and the exocyst subunit Sec8 (preferentially to PDZ2); its synaptic targeting is further regulated by CK2-mediated phosphorylation at Ser632 and by C-terminal alternative splicing; in epithelial cells it recruits Nedd4/Nedd4-2 E3 ligases via PPxY motifs to undergo monoubiquitination required for apical membrane recruitment and tight junction formation, while in cancer contexts COP1 ubiquitinates DLG3 to promote tumor cell proliferation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"DLG3/SAP102 is a postsynaptic MAGUK scaffold that links NMDA receptors to the submembranous cytomatrix at excitatory synapses, coordinating receptor trafficking and dendritic spine remodeling during synaptogenesis [#0, #10]. It binds the C-terminal tail of the NR2/GluN2 subunit through its PDZ domains and recognizes GluN2B through a second, PDZ-independent N-terminal site, and this dual mode of engagement governs both synaptic targeting and synaptic clearance of GluN2B-containing receptors [#1, #11, #14]. SAP102 mediates synaptic delivery of AMPA and NMDA receptors selectively during early development, after which PSD-95 assumes these functions, and it can sustain AMPAR transmission through a cornichon-2\\u2013dependent mechanism [#10, #20]. Beyond receptor anchoring, SAP102 nucleates a signaling platform: it recruits Pyk2 and the A2A adenosine receptor through its SH3/GK module, mPins to promote NMDAR surface delivery, EphB2/Kalirin-7 to drive PAK-dependent actin reorganization and synapse formation, and the exocyst subunit Sec8 preferentially via PDZ2 [#8, #9, #16, #17, #23]. Its synaptic enrichment and mobility are tuned by CK2 phosphorylation at Ser632 and by JNK3 phosphorylation, and by C-terminal alternative splicing that generates spine-enriched isoforms [#11, #18, #19, #24]. In polarized epithelia DLG3 recruits the Nedd4/Nedd4-2 E3 ligases via PPxY motifs to drive its own monoubiquitination, apical recruitment and tight-junction formation, while in cancer it engages MST2/LATS1 Hippo signaling and is regulated by COP1-mediated ubiquitination [#12, #21, #22]. Loss-of-function variants in DLG3, including a 5'UTR duplication that attenuates translation, cause intellectual disability [#27].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Established that SAP102 is a bona fide NMDA receptor-associated scaffold, defining the founding molecular interaction that placed it at the postsynaptic cytomatrix.\",\n      \"evidence\": \"Reciprocal co-immunoprecipitation from rat brain synaptosomes and cortical synaptic membranes plus in vitro PDZ-domain binding to the NR2B C-terminal tail\",\n      \"pmids\": [\"8780649\", \"8702950\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish functional consequence of the interaction in vivo\", \"Did not resolve which PDZ domain dominates binding in cells\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Showed SAP102 has functions beyond receptor anchoring by linking it to the APC tumor suppressor and demonstrating cross-species functional conservation with Drosophila Dlg.\",\n      \"evidence\": \"Yeast two-hybrid and in vitro binding to APC; heterologous rescue of dlg-1 mutant flies\",\n      \"pmids\": [\"9188857\", \"9152008\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"APC interaction not validated in mammalian neurons\", \"Mechanism of tumor/bouton rescue not resolved at the molecular level\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Identified Ca2+/calmodulin and p51-nedasin as regulators that can modulate SAP102 interactions, introducing the idea that NMDAR clustering by SAP102 is dynamically controlled.\",\n      \"evidence\": \"Surface plasmon resonance, pull-down, yeast two-hybrid, and in vitro competition assays\",\n      \"pmids\": [\"10026200\", \"10542258\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Regulatory effects shown largely in vitro\", \"Physiological calmodulin-dependent switching not demonstrated at synapses\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Demonstrated a PDZ-dependent growth-suppressive and adhesion-regulating role for SAP102 in non-neuronal cells, extending its function to cell polarity and proliferation control.\",\n      \"evidence\": \"Overexpression and domain-deletion analysis in cancer cell lines with beta-catenin readout\",\n      \"pmids\": [\"10797259\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Overexpression system may not reflect endogenous role\", \"APC-independent pathway not molecularly defined\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Defined mPins as a trafficking partner that drives SAP102 and NMDAR delivery to the membrane, linking the scaffold to G-protein regulatory machinery.\",\n      \"evidence\": \"Co-IP, siRNA knockdown, dominant-negative expression and surface assays in neurons\",\n      \"pmids\": [\"16299499\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Step in the secretory/trafficking pathway not pinpointed\", \"Relationship to PDZ-mediated NMDAR binding not resolved\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Resolved the developmental logic of MAGUK function by showing SAP102 mediates AMPA/NMDA receptor trafficking during synaptogenesis before PSD-95 takes over.\",\n      \"evidence\": \"In utero electroporation with dual whole-cell electrophysiology at distinct developmental stages in knockout mice\",\n      \"pmids\": [\"19104036\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of the developmental hand-off to PSD-95 unknown\", \"Does not define which interactions drive AMPAR versus NMDAR trafficking\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Uncovered a PDZ-independent N-terminal GluN2B binding site under alternative-splicing control that shapes spine morphology, and showed PDZ binding is required for receptor targeting but not SAP102 clustering itself.\",\n      \"evidence\": \"Co-IP domain mapping, shRNA knockdown, spine morphology and pharmacological NMDAR blockade; PDZ-mutant expression in neurons\",\n      \"pmids\": [\"21209193\", \"23178474\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the N-terminal site and PDZ binding are coordinated is unclear\", \"Splicing regulation upstream signals not identified\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Established a non-neuronal mechanism whereby DLG3 recruits Nedd4/Nedd4-2 via PPxY motifs to undergo monoubiquitination required for apical membrane recruitment and tight-junction formation.\",\n      \"evidence\": \"AP-MS, co-IP, knockout mouse, immunofluorescence and ubiquitination assays in polarized epithelia\",\n      \"pmids\": [\"21920314\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether ubiquitin-dependent targeting operates in neurons is unknown\", \"Deubiquitinase counterpart not identified\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Showed the secondary non-PDZ interaction mediates synaptic clearance of GluN2B receptors and identified the GluN2B residues responsible, defining a dual binding/clearance mechanism.\",\n      \"evidence\": \"GluN2B mutagenesis, SAP102 knockdown, surface biotinylation and electrophysiology; plus neurobeachin domain-mapping interaction\",\n      \"pmids\": [\"23103165\", \"22745750\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trafficking machinery executing clearance not defined\", \"Functional role of neurobeachin binding not established\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Connected SAP102 to EphB/PAK signaling and actin remodeling, showing it is required for ephrinB-driven synapse formation in developing cortex.\",\n      \"evidence\": \"shRNA knockdown, co-IP of EphB2/Kalirin-7, surface expression, EphB activation and actin analyses\",\n      \"pmids\": [\"23486974\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct versus indirect EphB2 binding not distinguished\", \"Link between actin remodeling and receptor trafficking not integrated\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined in vivo developmental roles via knockout and linked DLG3 to human intellectual disability through a translation-attenuating 5'UTR variant.\",\n      \"evidence\": \"Dlg3 knockout mouse electrophysiology and axon quantification; dual luciferase reporter and patient-cell Western blot\",\n      \"pmids\": [\"27466188\", \"27222290\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cellular mechanism linking reduced SAP102 to cognitive deficit unresolved\", \"KO phenotypes are subtle, indicating redundancy with other MAGUKs\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified cornichon-2 as the auxiliary subunit required for SAP102 to rescue AMPAR transmission, refining the MAGUK-AMPAR functional link.\",\n      \"evidence\": \"Molecular replacement of PSD-95, whole-cell electrophysiology and cornichon-2 knockdown\",\n      \"pmids\": [\"30067114\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct SAP102\\u2013CNIH-2 binding not demonstrated\", \"Physiological relevance outside replacement paradigm unclear\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Consolidated post-translational and structural control of SAP102 synaptic dynamics through CK2/JNK3 phosphorylation, splice-variant enrichment, Sec8/PDZ2 binding, and distinct subsynaptic nanocluster organization.\",\n      \"evidence\": \"In vitro kinase/FRAP/live-imaging assays; isoform knockdown; Sec8 crystal structure with binding assays; DNA-PAINT super-resolution\",\n      \"pmids\": [\"29282697\", \"38582451\", \"25555912\", \"37849738\", \"38777601\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How phosphorylation, splicing and nanocluster positioning integrate is unknown\", \"Functional consequence of SAP102-specific nanodomains not established\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Extended DLG3 into cancer signaling, implicating it in Hippo-pathway control and COP1-mediated ubiquitination affecting tumor cell proliferation.\",\n      \"evidence\": \"RIP, co-IP, luciferase reporter, ubiquitination assays and in vivo tumor/proliferation models in breast cancer and glioma cells\",\n      \"pmids\": [\"32593652\", \"37356109\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether MST2/Hippo and COP1 roles operate in neurons is unknown\", \"Direct DLG3\\u2013MST2 binding interface not mapped\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the multiple regulatory layers (phosphorylation, ubiquitination, alternative splicing, nanocluster positioning) are integrated to control SAP102 function in vivo, and how this maps onto cognitive phenotypes, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model linking PTMs and splicing to physiological output\", \"Mechanism connecting SAP102 loss to intellectual disability undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 9, 16, 23]},\n      {\"term_id\": \"GO:0030674\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0014069\", \"supporting_discovery_ids\": [7, 25]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [9, 12]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 10, 16]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [10, 12, 26]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [16, 21]}\n    ],\n    \"complexes\": [\"NMDA receptor\\u2013MAGUK complex\", \"exocyst (via Sec8)\"],\n    \"partners\": [\"GRIN2B\", \"DLG4\", \"PTK2B\", \"GPSM2\", \"EPHB2\", \"KALRN\", \"EXOC4\", \"NEDD4\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}