{"gene":"NECTIN3","run_date":"2026-06-10T05:19:52","timeline":{"discoveries":[{"year":2000,"finding":"Nectin-3alpha forms a cis-homodimer and undergoes Ca2+-independent trans-homo-interaction to cause homophilic cell-cell adhesion; it also undergoes trans-hetero-interaction with nectin-1 or nectin-2 (but does not form cis-heterodimers with them). Nectin-3alpha co-localizes with nectin-2 at cadherin-based adherens junctions and interacts with afadin, an actin filament-binding protein that connects nectin to the actin cytoskeleton.","method":"Cell-based adhesion assays, co-immunoprecipitation, immunofluorescence colocalization","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP and cell adhesion assays, replicated across multiple nectin family members in the same study, foundational characterization paper","pmids":["10744716"],"is_preprint":false},{"year":2000,"finding":"Nectin-3/PRR3 carries the C-terminal A/EXYV consensus motif and interacts in vivo with both long and short isoforms of afadin via this motif.","method":"In vivo co-immunoprecipitation, sequence analysis","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP demonstrated in vivo, single lab, corroborated by sequence motif analysis","pmids":["11024295"],"is_preprint":false},{"year":2002,"finding":"The trans-hetero-interaction of nectin-3 with nectin-1 is mediated through V-to-V domain contacts (KD ~1 nM), with C domains contributing to increased affinity. The minimal nectin-3 binding region on nectin-1 was mapped to the C-C'-C\"-D beta-strands of the V domain using chimeric nectin1/PVR receptors.","method":"Surface plasmon resonance binding assays, chimeric receptor domain-swap experiments, competition assays with blocking antibodies and HSV-1 glycoprotein D","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro binding assays with mutagenesis/chimeras plus multiple orthogonal competition experiments","pmids":["12011057"],"is_preprint":false},{"year":2003,"finding":"Necl-5/Tage4 (later renamed nectin-like molecule-5) heterophilically trans-interacts with nectin-3 but not homophilically, and this trans-interaction enhances motility of V12Ras-NIH3T3 cells. Unlike nectins, Tage4/Necl-5 does not bind afadin.","method":"Cell-based ligand binding assays, cell motility assays, co-immunoprecipitation","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-based binding assay plus functional motility readout, single lab","pmids":["12740392"],"is_preprint":false},{"year":2003,"finding":"Nectin-3 binds CD155 (PVR) and its mouse homologue Tage4 in cell-based ligand binding assays. Coculture of nectin-3- and CD155-expressing cells led to CD155-dependent recruitment of nectin-3 to cell-cell contacts. CD155 co-distributes with alpha(v) integrin microdomains, suggesting a trans-interaction between cell-cell (nectin) and cell-matrix (integrin/CD155) adhesion systems at junctions.","method":"Cell-based ligand binding assays, immunofluorescence colocalization, heterologous coculture system","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-based binding assay and colocalization, single lab, multiple cell contexts tested","pmids":["12759359"],"is_preprint":false},{"year":2004,"finding":"Necl-5 enhances cell migration in an integrin alpha(V)beta(3)-dependent, nectin-3-independent manner when cells are not in contact; Necl-5 colocalizes with integrin alpha(V)beta(3) at leading edges. Necl-5-enhanced migration requires activation of Cdc42 and Rac small GTPases.","method":"Mutant Necl-5 constructs in L fibroblasts and NIH3T3 cells, integrin inhibitor/activator assays, dominant-negative mutants, small GTPase activation assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple mutant constructs and pharmacological tools, single lab","pmids":["14871893"],"is_preprint":false},{"year":2004,"finding":"Upon Necl-5/nectin-3 heterophilic trans-interaction, afadin, E-cadherin, and catenins are recruited to the nectin-3 side (not the Necl-5 side) of the contact site, facilitating adherens junction formation. A monoclonal antibody blocking Necl-5/nectin-3 interaction inhibited E-cadherin-based AJ formation.","method":"Stable cell lines expressing Necl-5, nectin-3, and E-cadherin; immunofluorescence; blocking antibody experiments","journal":"Genes to cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined cellular reconstitution with blocking antibody, single lab","pmids":["15330856"],"is_preprint":false},{"year":2005,"finding":"Nectin-1 and nectin-3 heterophilic trans-interaction is required for establishing apex-apex adhesion between pigment and non-pigment cell layers of the ciliary epithelia; nectin-1-/- and nectin-3-/- mice both show microphthalmia with separation of this contact layer, while apicolateral junctions are unaffected.","method":"Genetic knockout mice (nectin-1-/- and nectin-3-/-), immunofluorescence and immunoelectron microscopy","journal":"Development","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic loss-of-function in two independent knockouts with specific morphological phenotype and localization confirmed by electron microscopy","pmids":["15728677"],"is_preprint":false},{"year":2005,"finding":"Upon cell-cell contact, Necl-5 is down-regulated from the cell surface via clathrin-dependent endocytosis initiated by its interaction with nectin-3; this down-regulation reduces cell movement and proliferation, representing a mechanism for contact inhibition.","method":"Cell-surface down-regulation assays, clathrin inhibitor experiments, nectin-3-dependent coculture assays","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — mechanistic dissection with pharmacological inhibition of endocytosis and specific nectin-3 interaction requirement, multiple orthogonal readouts","pmids":["16216929"],"is_preprint":false},{"year":2006,"finding":"Nectin-3 localizes asymmetrically to the spermatid side of Sertoli-spermatid junctions and its heterophilic trans-interaction with nectin-2 (on Sertoli cells) is essential for spermatid development. Nectin-3-/- mice are male-infertile with distorted sperm nuclei, abnormal mitochondrial distribution, and mislocalized nectin-2; wild-type stem cell transplantation partially rescues these defects.","method":"Genetic knockout mice (nectin-3-/-), immunolocalization, spermatogenic stem cell transplantation rescue experiment","journal":"Genes to cells","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with specific phenotype, rescue by transplantation, and localization studies in a single study","pmids":["16923130"],"is_preprint":false},{"year":2012,"finding":"CADM1 on mast cells mediates attachment to dorsal root ganglion (DRG) neurites and subsequent calcium responses via heterophilic binding to nectin-3 expressed on DRG neurons; a neutralizing antibody to nectin-3 inhibited both mast cell attachment and calcium signaling.","method":"Neutralizing antibody blocking assay, co-culture attachment assays, calcium imaging","journal":"Journal of neuroimmunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional blocking antibody with two readouts (adhesion and calcium), single lab","pmids":["22703826"],"is_preprint":false},{"year":2012,"finding":"sFRP1 regulates spermatid adhesion and spermiation by suppressing phosphorylation of FAK (Tyr397), which in turn reduces phosphorylation and promotes retention of nectin-3 at the apical ectoplasmic specialization. In vivo administration of recombinant sFRP1 delayed spermiation with concurrent nectin-3 retention; overexpression in Sertoli-germ cell coculture confirmed FAK-nectin-3 phosphorylation axis.","method":"In vivo recombinant protein administration, lentiviral overexpression in coculture, Western blotting for phospho-FAK and phospho-nectin-3","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo and in vitro experiments with phosphorylation readouts, single lab","pmids":["23073828"],"is_preprint":false},{"year":2013,"finding":"Hippocampal nectin-3 is necessary for stress effects on spatial memory and dendritic spine density. Acute and chronic stress reduce hippocampal nectin-3 levels via CRH-CRHR1 signaling (not glucocorticoid receptor). Knockdown of hippocampal nectin-3 caused spatial memory deficits and spine loss; restoration of nectin-3 rescued early-life stress effects on memory and spine density in adulthood.","method":"AAV-mediated knockdown and overexpression, CRHR1 knockout mice, CRH-overexpressing transgenic mice, fear conditioning and spatial memory tasks, dendritic spine analysis","journal":"Nature neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple genetic models (KO, transgenic, AAV), bidirectional manipulation (KD and OE), multiple orthogonal behavioral and structural readouts","pmids":["23644483"],"is_preprint":false},{"year":2013,"finding":"Nectin-3 expressed on T lymphocytes trans-interacts with nectin-2 on high endothelial venules; blocking either nectin-3 (on lymphocytes) or nectin-2 (on ECs) with monoclonal antibodies inhibits lymphocyte transendothelial migration in vitro.","method":"Soluble nectin-3 binding assays, blocking monoclonal antibodies, transendothelial migration assay","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional blocking antibody approach with specific migration readout, single lab","pmids":["24116228"],"is_preprint":false},{"year":2014,"finding":"MMP-9 proteolytically cleaves nectin-3 in the perisynaptic CA1 region following chronic restraint stress; this process involves NMDA receptor activation and is responsible for stress-induced social and cognitive alterations. Nectin-3 reduction was specific to CA1, not CA3.","method":"Gelatinase activity assays, MMP-9 inhibition, NMDA receptor antagonism, immunohistochemistry, behavioral assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — enzymatic cleavage assay plus pharmacological dissection of upstream pathway and behavioral readouts, multiple orthogonal methods","pmids":["25232752"],"is_preprint":false},{"year":2014,"finding":"In Nectin-3-deficient mice, hair cells aberrantly contact each other and form abnormal junctions; this leads to disturbed hair bundle orientation and morphology, abnormal kinocilium positioning, and mislocalization of cadherin-catenin complexes and polarity proteins Pals1 and Par-3 specifically in the aberrantly attached (not unattached) HCs.","method":"Nectin-3 knockout mice, immunofluorescence, confocal and electron microscopy","journal":"Development","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with specific structural phenotype, mechanistic link between aberrant junction formation and polarity protein mislocalization demonstrated","pmids":["24381198"],"is_preprint":false},{"year":2015,"finding":"Crystal structure of the afadin PDZ domain (AFPDZ) in complex with the nectin-3 C-terminal peptide revealed that the last three C-terminal amino acids of nectin-3 (containing two hydrophobic residues of the class II motif) are sufficient for AFPDZ binding, and binding induces a ~2.5 Å-wider ligand-binding groove in AFPDZ compared to unliganded structures.","method":"X-ray crystallography of AFPDZ-nectin-3 fusion protein complex","journal":"Protein science","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with defined binding interface, single lab","pmids":["25534554"],"is_preprint":false},{"year":2015,"finding":"Nectin-3 sialylation is regulated by TGFBR2 signaling in colon cancer cells; upon TGFBR2 reconstitution, nectin-3 loses sialic acid incorporation, identifying nectin-3 as a glycoprotein target of TGFBR2-dependent glycome regulation.","method":"RMCE-based TGFBR2 reconstitution, Click-It chemistry for sialic acid labeling, mass spectrometry","journal":"Protein science","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — mass spectrometry-based glycoproteomics with reconstitution, single lab, single method for nectin-3 specifically","pmids":["26177744"],"is_preprint":false},{"year":2016,"finding":"Nectin-3 is present in rat uterine epithelial cells as three isoforms (80, 60, 32 kDa) and redistributes from basal cytoplasmic localization to cell junctions at the time of implantation (day 6); this junctional localization is regulated by progesterone. At implantation, nectin-3 localizes to the tight junction but does not interact with occludin or l-afadin.","method":"Immunofluorescence, Western blotting, co-immunoprecipitation, progesterone manipulation","journal":"Reproductive sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP (negative for occludin/l-afadin), immunofluorescence with hormonal manipulation, multiple methods in single lab","pmids":["27217376"],"is_preprint":false},{"year":2017,"finding":"Nectin-3 protein in spermatids is internalized at tubulobulbar complexes (clathrin/actin-based junction-internalizing structures) at Sertoli-spermatid junctions; nectin-3 labeling occurs at junctions, tubulobulbar complex bulbs, and associated double-membrane vesicles, with Rab5 associating with bulbs before scission.","method":"Pre-embedding immunoelectron microscopy with Rab5, EEA1, and nectin-3 antibodies","journal":"Anatomical record","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — high-resolution immunoelectron microscopy localizing nectin-3 to specific endocytic structures, single lab","pmids":["28176461"],"is_preprint":false},{"year":2017,"finding":"AAV-mediated knockdown of nectin-3 in dentate gyrus neurons impaired long-term spatial memory and temporal order memory, increased density of immature doublecortin+ and calretinin+ neurons but decreased calbindin immunoreactivity, indicating nectin-3 modulates differentiation/maturation of adult-born granule cells. Selective nectin-3 knockdown in new DG neurons via retrovirus reduced thin dendritic spines.","method":"AAV-mediated knockdown, retroviral labeling of newborn neurons, immunohistochemistry for neurogenesis markers, behavioral testing","journal":"Translational psychiatry","confidence":"High","confidence_rationale":"Tier 2 / Strong — two targeting strategies (AAV broad and retroviral newborn-specific), multiple orthogonal cellular and behavioral readouts, single lab","pmids":["28872640"],"is_preprint":false},{"year":2020,"finding":"ZNF582 directly regulates transcription of nectin-3 (and NRXN3) as shown by ChIP-seq and ChIP-qPCR; restoration or abrogation of nectin-3 reversed the tumor suppressor effect of ZNF582 on NPC migration and invasion in vitro and in vivo.","method":"ChIP-seq, ChIP-qPCR, luciferase reporter assay, rescue/epistasis experiments with nectin-3 overexpression/knockdown","journal":"Cancer communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP-seq with functional epistasis rescue, single lab","pmids":["33038291"],"is_preprint":false},{"year":2020,"finding":"AAV-mediated knockdown of nectin-3 in mouse medial prefrontal cortex (mPFC) during adolescence reproduced chronic stress-induced impairments in social recognition and spatial working memory, and reduced dendritic complexity and spine density; membrane localization of nectin-3 was significantly correlated with behavioral performance.","method":"AAV-mediated knockdown, behavioral testing, dendritic morphology analysis, membrane fractionation","journal":"Neuroscience bulletin","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with specific behavioral and structural readouts, single lab","pmids":["32385776"],"is_preprint":false},{"year":2020,"finding":"Precise levels of nectin-3 in visual cortex layer 2/3 neurons regulate dendritic spine density during synaptogenesis. Knockdown increased dendritic spine density at P21/P35; overexpression decreased it. Overexpression of nectin-3 lacking its afadin-binding domain caused an even greater decrease in spine density on basal dendrites, indicating the afadin-binding domain is important for nectin-3's role in spine formation.","method":"In utero electroporation with shRNA knockdown and full-length/truncated overexpression constructs; spine density analysis at multiple developmental timepoints","journal":"Neural development","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — bidirectional manipulation with domain-deletion mutant, multiple timepoints, single lab","pmids":["33160402"],"is_preprint":false},{"year":2023,"finding":"Nectin-3, previously characterized as an adherens junction protein, is also localized to the brush border of colonocytes and can serve as a cell surface receptor for Clostridioides difficile toxin B (TcdB) on colonic epithelial cells.","method":"Immunofluorescence microscopy on colonic tissue, receptor localization studies","journal":"mBio","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — immunofluorescence localization establishing unexpected receptor site, single lab, limited mechanistic depth on binding mechanism","pmids":["37747247"],"is_preprint":false},{"year":2024,"finding":"Knockdown of dorsal CA1 nectin-3 impaired object recognition memory in adolescent female mice, while overexpression of dorsal CA1 nectin-3 reversed early-life stress-induced recognition memory deficits. Systemic CRHR1 antagonism (antalarmin) upregulated hippocampal nectin-3 levels and rescued memory deficits, placing nectin-3 downstream of CRHR1 signaling.","method":"AAV-mediated knockdown and overexpression, pharmacological CRHR1 antagonism, novel object recognition behavioral testing","journal":"Neuroscience bulletin","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — bidirectional AAV manipulation plus pharmacological epistasis, single lab","pmids":["39395912"],"is_preprint":false},{"year":2025,"finding":"PCP signaling (via Vangl2) regulates the junctional localization of Nectin-3 in cochlear supporting cells; loss of Nectin-3 partially phenocopies SGNII peripheral afferent turning defects seen in Vangl2 mutants. Epistasis analysis indicates Nectin-3 and Rac1 act in the same genetic pathway downstream of PCP to control SGNII axon guidance, with Nectin-3 likely providing a cell adhesion function for afferent turning.","method":"Genetic loss-of-function (Nectin-3 and Rac1 conditional knockouts), epistasis with Vangl2 mutants, immunofluorescence of junctional protein localization","journal":"Development","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with two genes in the same pathway, specific axon guidance phenotype, single lab","pmids":["40207531"],"is_preprint":false}],"current_model":"NECTIN-3 is a Ca2+-independent immunoglobulin-like cell adhesion molecule that forms cis-homodimers and engages in trans-homo- and trans-hetero-interactions (with nectin-1, nectin-2, Necl-5/CD155, and CADM1) through its V-domain to organize adherens junctions, Sertoli-spermatid junctions, and synaptic contacts; its cytoplasmic C-terminal class II PDZ-binding motif (EXYV) binds the afadin PDZ domain to link it to the actin cytoskeleton, and its junctional retention/removal is regulated by FAK phosphorylation, MMP-9 proteolytic cleavage, and clathrin-dependent endocytosis triggered by Necl-5 interaction, while in the hippocampus and prefrontal cortex it is transcriptionally and post-translationally regulated downstream of CRH-CRHR1 signaling to control dendritic spine density, adult neurogenesis, and memory."},"narrative":{"mechanistic_narrative":"NECTIN3 is a Ca2+-independent immunoglobulin-like cell adhesion molecule that organizes cell-cell junctions across epithelial, germ cell, and neuronal tissues by forming cis-homodimers and engaging trans-homophilic and trans-heterophilic contacts through its membrane-distal V domain [PMID:10744716, PMID:12011057]. Its heterophilic partnerships are functionally specialized: high-affinity V-to-V trans-interaction with nectin-1 mediates apex-apex adhesion of ciliary epithelia [PMID:12011057, PMID:15728677], trans-interaction with nectin-2 builds Sertoli-spermatid junctions required for spermatid development and lymphocyte transendothelial migration [PMID:16923130, PMID:24116228], and heterophilic engagement with Necl-5/CD155 recruits afadin, E-cadherin, and catenins to nucleate adherens junctions [PMID:12759359, PMID:15330856]. The cytoplasmic C-terminal class II PDZ-binding motif (EXYV) binds the afadin PDZ domain — the terminal residues are sufficient for binding and widen the PDZ groove — linking nectin-3 to the actin cytoskeleton [PMID:11024295, PMID:25534554]. Junctional retention versus removal of nectin-3 is dynamically regulated: FAK (Tyr397)-dependent phosphorylation controls retention at the apical ectoplasmic specialization [PMID:23073828], clathrin-dependent endocytosis triggered by Necl-5 interaction down-regulates surface levels to enforce contact inhibition [PMID:16216929], and MMP-9 proteolytically cleaves perisynaptic nectin-3 [PMID:25232752]. Through these mechanisms nectin-3 enforces correct junctional geometry and polarity protein localization in hair cells and cochlear supporting cells downstream of PCP/Vangl2-Rac1 signaling [PMID:24381198, PMID:40207531]. In the hippocampus and prefrontal cortex, nectin-3 acts downstream of CRH-CRHR1 signaling to control dendritic spine density, adult neurogenesis, and memory, with its afadin-binding domain required for spine regulation [PMID:23644483, PMID:28872640, PMID:33160402, PMID:37747247]. Nectin-3 also serves as a brush-border receptor for Clostridioides difficile toxin B on colonic epithelium [PMID:37747247].","teleology":[{"year":2000,"claim":"Establishing nectin-3 as an adhesion molecule required defining how it self-associates and partners with other nectins; this showed it drives homophilic adhesion and links to the cytoskeleton via afadin.","evidence":"Cell adhesion assays, reciprocal Co-IP, and immunofluorescence colocalization across nectin family members","pmids":["10744716","11024295"],"confidence":"High","gaps":["Structural basis of trans-interaction not resolved","Quantitative affinities of homo- vs hetero-interaction not measured at this stage"]},{"year":2002,"claim":"It was unknown which structural elements drive nectin-3/nectin-1 binding; domain-swap and SPR work mapped a high-affinity (~1 nM) V-to-V interface with C-domain affinity contributions.","evidence":"Surface plasmon resonance, chimeric nectin1/PVR domain-swaps, and antibody/glycoprotein D competition","pmids":["12011057"],"confidence":"High","gaps":["Co-crystal structure of the trans-dimer not determined","Whether the same interface governs nectin-2 and Necl-5 binding not tested"]},{"year":2003,"claim":"Defining the partner repertoire beyond nectins, nectin-3 was shown to trans-interact heterophilically with Necl-5/CD155 (but not homophilically), promoting cell motility and bridging cell-cell to cell-matrix adhesion.","evidence":"Cell-based ligand binding, motility assays, Co-IP, and integrin microdomain colocalization","pmids":["12740392","12759359"],"confidence":"Medium","gaps":["Necl-5 does not bind afadin, leaving its cytoplasmic coupling unclear","Direct physical link between nectin and integrin systems inferred from colocalization"]},{"year":2004,"claim":"The downstream consequence of Necl-5/nectin-3 engagement was unresolved; reconstitution showed afadin, E-cadherin, and catenins are recruited specifically to the nectin-3 side to nucleate adherens junctions.","evidence":"Stable reconstituted cell lines, immunofluorescence, and blocking antibodies; parallel work mapped Necl-5-driven migration to integrin alphaVbeta3/Cdc42/Rac","pmids":["15330856","14871893"],"confidence":"Medium","gaps":["Why recruitment is asymmetric to the nectin-3 side mechanistically unexplained","Migration arm is nectin-3-independent, so two functions are coupled only at the receptor level"]},{"year":2005,"claim":"How nectins regulate contact inhibition was unknown; nectin-3 was shown to trigger clathrin-dependent endocytic down-regulation of Necl-5, reducing movement and proliferation, while in vivo two knockouts established a requirement for nectin-1/nectin-3 apex-apex adhesion in ciliary epithelia.","evidence":"Surface down-regulation assays with clathrin inhibitors; nectin-1-/- and nectin-3-/- mice with immuno-EM","pmids":["16216929","15728677"],"confidence":"High","gaps":["Adaptor machinery driving clathrin recruitment to nectin-3 not identified","Generality of endocytic regulation beyond Necl-5 untested"]},{"year":2006,"claim":"The physiological role of nectin-3 heterophilic adhesion was tested genetically; nectin-3-/- mice are male-infertile with disrupted Sertoli-spermatid junctions and mislocalized nectin-2, rescued by wild-type stem cell transplantation.","evidence":"Nectin-3 knockout mice, immunolocalization, spermatogenic stem cell transplantation rescue","pmids":["16923130"],"confidence":"High","gaps":["Cell-autonomous vs non-autonomous contribution only partly resolved by transplantation","Signaling consequences of junction loss not defined"]},{"year":2012,"claim":"Mechanisms controlling junctional retention and new partner contexts were addressed; FAK(Tyr397)/sFRP1 signaling controls nectin-3 retention at the apical ectoplasmic specialization, and CADM1-nectin-3 mediates mast cell-neurite attachment with calcium signaling.","evidence":"In vivo recombinant sFRP1, coculture overexpression with phospho-FAK/phospho-nectin-3 blots; neutralizing-antibody adhesion and calcium imaging","pmids":["23073828","22703826"],"confidence":"Medium","gaps":["Direct phosphorylation site on nectin-3 not mapped","Whether FAK acts directly on nectin-3 or via intermediates unresolved"]},{"year":2013,"claim":"A neuronal function was established; hippocampal nectin-3 is required for stress effects on spatial memory and spine density, with stress reducing nectin-3 via CRH-CRHR1 (not glucocorticoid receptor) signaling, and restoration rescuing early-life stress deficits.","evidence":"AAV knockdown/overexpression, CRHR1 KO and CRH-transgenic mice, behavioral and spine analyses; parallel nectin-2/nectin-3 blockade inhibited lymphocyte transendothelial migration","pmids":["23644483","24116228"],"confidence":"High","gaps":["Molecular link from CRHR1 signaling to nectin-3 transcription/turnover not fully defined","Synaptic partner mediating spine effects in vivo not identified"]},{"year":2014,"claim":"Post-translational removal of synaptic nectin-3 and its role in tissue patterning were resolved; MMP-9 cleaves perisynaptic CA1 nectin-3 downstream of NMDA receptor activation under chronic stress, and nectin-3 loss causes aberrant hair-cell contacts with polarity protein mislocalization.","evidence":"Gelatinase assays, MMP-9/NMDAR pharmacology, behavior; nectin-3 KO mice with confocal/EM and polarity protein staining","pmids":["25232752","24381198"],"confidence":"High","gaps":["Cleavage site on nectin-3 not mapped","How aberrant adhesion drives polarity protein mislocalization mechanistically unclear"]},{"year":2015,"claim":"The structural basis of cytoskeletal coupling and a glycosylation control point were defined; the nectin-3 C-terminal triresidue is sufficient for afadin PDZ binding and widens the groove, while TGFBR2 signaling controls nectin-3 sialylation in colon cancer.","evidence":"X-ray crystallography of AFPDZ-nectin-3 complex; TGFBR2 reconstitution with click-chemistry sialic acid labeling and mass spectrometry","pmids":["25534554","26177744"],"confidence":"High","gaps":["Functional consequence of nectin-3 sialylation change not established","Single-method evidence for the glycosylation finding"]},{"year":2017,"claim":"The trafficking route for nectin-3 removal and an additional neuronal role were characterized; nectin-3 is internalized via Rab5-associated tubulobulbar complexes at Sertoli-spermatid junctions, and dentate gyrus nectin-3 modulates adult-born neuron maturation and memory.","evidence":"Immuno-EM with Rab5/EEA1; AAV and retroviral newborn-neuron-specific knockdown with neurogenesis markers and behavior","pmids":["28176461","28872640"],"confidence":"Medium","gaps":["Endocytic adaptors linking nectin-3 to tubulobulbar complexes not identified","Molecular targets coupling nectin-3 to differentiation markers unknown"]},{"year":2020,"claim":"Transcriptional and circuit-level regulation were extended; ZNF582 directly represses nectin-3 to suppress nasopharyngeal carcinoma invasion, mPFC nectin-3 mediates adolescent stress effects on behavior and spines, and the afadin-binding domain was shown to be required for nectin-3's spine-density control in visual cortex.","evidence":"ChIP-seq/ChIP-qPCR with rescue epistasis; AAV mPFC knockdown with membrane fractionation; in utero electroporation with afadin-binding-deletion constructs","pmids":["33038291","32385776","33160402"],"confidence":"Medium","gaps":["Whether ZNF582 regulation operates outside NPC unknown","Direct synaptic mechanism by which afadin coupling shapes spines not resolved"]},{"year":2023,"claim":"An unexpected functional role at the colonic surface was identified; nectin-3 localizes to the colonocyte brush border and serves as a receptor for Clostridioides difficile toxin B.","evidence":"Immunofluorescence on colonic tissue and receptor localization studies","pmids":["37747247"],"confidence":"Medium","gaps":["Binding interface between TcdB and nectin-3 not mapped","Functional contribution to in vivo toxin entry not quantified"]},{"year":2024,"claim":"Causal placement of nectin-3 downstream of CRHR1 in memory was strengthened, and a PCP-Rac1 axis controlling its junctional localization in axon guidance was defined.","evidence":"AAV bidirectional manipulation with CRHR1 antagonism (antalarmin); Nectin-3/Rac1 conditional KO epistasis with Vangl2 mutants and junctional protein staining","pmids":["39395912","40207531"],"confidence":"Medium","gaps":["Direct molecular signal from CRHR1 to nectin-3 still indirect","How PCP signaling positions nectin-3 at the junction mechanistically unresolved"]},{"year":null,"claim":"How the same V-domain adhesion code is selectively read out into distinct outcomes (junction assembly, endocytic contact inhibition, spine regulation, toxin entry) across tissues remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model linking partner choice to downstream signaling output","Tissue-specific regulators of nectin-3 turnover incompletely defined","Structure of full trans-adhesion complex unsolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[0,2,7,9]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,16]},{"term_id":"GO:0001618","term_label":"virus receptor activity","supporting_discovery_ids":[24]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,4,18,24]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,1,16]}],"pathway":[{"term_id":"R-HSA-1500931","term_label":"Cell-Cell communication","supporting_discovery_ids":[0,6,7]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[12,20,23]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[7,9,15,26]}],"complexes":["nectin-afadin adhesion complex","adherens junction"],"partners":["AFDN","NECTIN1","NECTIN2","PVR","CADM1","PTK2","MMP9"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NQS3","full_name":"Nectin-3","aliases":["CDw113","Nectin cell adhesion molecule 3","Poliovirus receptor-related protein 3"],"length_aa":549,"mass_kda":61.0,"function":"Cell adhesion molecule that promotes cell-cell adhesion through heterophilic trans-interactions with nectins-like or other nectins, such as trans-interaction with NECTIN2 at Sertoli-spermatid junctions (PubMed:16216929). Trans-interaction with PVR induces activation of CDC42 and RAC small G proteins through common signaling molecules such as SRC and RAP1 (PubMed:16216929). Induces endocytosis-mediated down-regulation of PVR from the cell surface, resulting in reduction of cell movement and proliferation (PubMed:16216929). Involved in axon guidance by promoting contacts between the commissural axons and the floor plate cells (By similarity). Also involved in the formation of cell-cell junctions, including adherens junctions and synapses (By similarity). Promotes formation of checkerboard-like cellular pattern of hair cells and supporting cells in the auditory epithelium via heterophilic interaction with NECTIN1: NECTIN1 is present in the membrane of hair cells and associates with NECTIN3 on supporting cells, thereby mediating heterotypic adhesion between these two cell types (By similarity). Plays a role in the morphology of the ciliary body (By similarity)","subcellular_location":"Cell membrane; Postsynaptic cell membrane; Cell junction, adherens junction","url":"https://www.uniprot.org/uniprotkb/Q9NQS3/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/NECTIN3","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/NECTIN3","total_profiled":1310},"omim":[{"mim_id":"621139","title":"COILED-COIL DOMAIN-CONTAINING PROTEIN 178; CCDC178","url":"https://www.omim.org/entry/621139"},{"mim_id":"607147","title":"NECTIN CELL ADHESION MOLECULE 3; NECTIN3","url":"https://www.omim.org/entry/607147"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Uncertain","locations":[{"location":"Cell Junctions","reliability":"Uncertain"},{"location":"Cytosol","reliability":"Uncertain"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"testis","ntpm":51.0}],"url":"https://www.proteinatlas.org/search/NECTIN3"},"hgnc":{"alias_symbol":["nectin-3","PPR3","PVRR3","DKFZP566B0846","CDw113","CD113"],"prev_symbol":["PVRL3"]},"alphafold":{"accession":"Q9NQS3","domains":[{"cath_id":"2.60.40.10","chopping":"59-166","consensus_level":"high","plddt":93.3954,"start":59,"end":166},{"cath_id":"2.60.40.10","chopping":"170-265","consensus_level":"high","plddt":96.3629,"start":170,"end":265},{"cath_id":"2.60.40.10","chopping":"268-352","consensus_level":"high","plddt":94.4145,"start":268,"end":352}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NQS3","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NQS3-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NQS3-F1-predicted_aligned_error_v6.png","plddt_mean":73.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NECTIN3","jax_strain_url":"https://www.jax.org/strain/search?query=NECTIN3"},"sequence":{"accession":"Q9NQS3","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NQS3.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NQS3/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NQS3"}},"corpus_meta":[{"pmid":"10744716","id":"PMC_10744716","title":"Nectin-3, a new member of immunoglobulin-like cell adhesion molecules that shows homophilic and heterophilic cell-cell adhesion activities.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10744716","citation_count":247,"is_preprint":false},{"pmid":"12011057","id":"PMC_12011057","title":"Prominent role of the Ig-like V domain in trans-interactions of nectins. 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Nectin-3alpha co-localizes with nectin-2 at cadherin-based adherens junctions and interacts with afadin, an actin filament-binding protein that connects nectin to the actin cytoskeleton.\",\n      \"method\": \"Cell-based adhesion assays, co-immunoprecipitation, immunofluorescence colocalization\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP and cell adhesion assays, replicated across multiple nectin family members in the same study, foundational characterization paper\",\n      \"pmids\": [\"10744716\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Nectin-3/PRR3 carries the C-terminal A/EXYV consensus motif and interacts in vivo with both long and short isoforms of afadin via this motif.\",\n      \"method\": \"In vivo co-immunoprecipitation, sequence analysis\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP demonstrated in vivo, single lab, corroborated by sequence motif analysis\",\n      \"pmids\": [\"11024295\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"The trans-hetero-interaction of nectin-3 with nectin-1 is mediated through V-to-V domain contacts (KD ~1 nM), with C domains contributing to increased affinity. The minimal nectin-3 binding region on nectin-1 was mapped to the C-C'-C\\\"-D beta-strands of the V domain using chimeric nectin1/PVR receptors.\",\n      \"method\": \"Surface plasmon resonance binding assays, chimeric receptor domain-swap experiments, competition assays with blocking antibodies and HSV-1 glycoprotein D\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro binding assays with mutagenesis/chimeras plus multiple orthogonal competition experiments\",\n      \"pmids\": [\"12011057\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Necl-5/Tage4 (later renamed nectin-like molecule-5) heterophilically trans-interacts with nectin-3 but not homophilically, and this trans-interaction enhances motility of V12Ras-NIH3T3 cells. Unlike nectins, Tage4/Necl-5 does not bind afadin.\",\n      \"method\": \"Cell-based ligand binding assays, cell motility assays, co-immunoprecipitation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-based binding assay plus functional motility readout, single lab\",\n      \"pmids\": [\"12740392\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Nectin-3 binds CD155 (PVR) and its mouse homologue Tage4 in cell-based ligand binding assays. Coculture of nectin-3- and CD155-expressing cells led to CD155-dependent recruitment of nectin-3 to cell-cell contacts. CD155 co-distributes with alpha(v) integrin microdomains, suggesting a trans-interaction between cell-cell (nectin) and cell-matrix (integrin/CD155) adhesion systems at junctions.\",\n      \"method\": \"Cell-based ligand binding assays, immunofluorescence colocalization, heterologous coculture system\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-based binding assay and colocalization, single lab, multiple cell contexts tested\",\n      \"pmids\": [\"12759359\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Necl-5 enhances cell migration in an integrin alpha(V)beta(3)-dependent, nectin-3-independent manner when cells are not in contact; Necl-5 colocalizes with integrin alpha(V)beta(3) at leading edges. Necl-5-enhanced migration requires activation of Cdc42 and Rac small GTPases.\",\n      \"method\": \"Mutant Necl-5 constructs in L fibroblasts and NIH3T3 cells, integrin inhibitor/activator assays, dominant-negative mutants, small GTPase activation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple mutant constructs and pharmacological tools, single lab\",\n      \"pmids\": [\"14871893\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Upon Necl-5/nectin-3 heterophilic trans-interaction, afadin, E-cadherin, and catenins are recruited to the nectin-3 side (not the Necl-5 side) of the contact site, facilitating adherens junction formation. A monoclonal antibody blocking Necl-5/nectin-3 interaction inhibited E-cadherin-based AJ formation.\",\n      \"method\": \"Stable cell lines expressing Necl-5, nectin-3, and E-cadherin; immunofluorescence; blocking antibody experiments\",\n      \"journal\": \"Genes to cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined cellular reconstitution with blocking antibody, single lab\",\n      \"pmids\": [\"15330856\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Nectin-1 and nectin-3 heterophilic trans-interaction is required for establishing apex-apex adhesion between pigment and non-pigment cell layers of the ciliary epithelia; nectin-1-/- and nectin-3-/- mice both show microphthalmia with separation of this contact layer, while apicolateral junctions are unaffected.\",\n      \"method\": \"Genetic knockout mice (nectin-1-/- and nectin-3-/-), immunofluorescence and immunoelectron microscopy\",\n      \"journal\": \"Development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic loss-of-function in two independent knockouts with specific morphological phenotype and localization confirmed by electron microscopy\",\n      \"pmids\": [\"15728677\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Upon cell-cell contact, Necl-5 is down-regulated from the cell surface via clathrin-dependent endocytosis initiated by its interaction with nectin-3; this down-regulation reduces cell movement and proliferation, representing a mechanism for contact inhibition.\",\n      \"method\": \"Cell-surface down-regulation assays, clathrin inhibitor experiments, nectin-3-dependent coculture assays\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mechanistic dissection with pharmacological inhibition of endocytosis and specific nectin-3 interaction requirement, multiple orthogonal readouts\",\n      \"pmids\": [\"16216929\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Nectin-3 localizes asymmetrically to the spermatid side of Sertoli-spermatid junctions and its heterophilic trans-interaction with nectin-2 (on Sertoli cells) is essential for spermatid development. Nectin-3-/- mice are male-infertile with distorted sperm nuclei, abnormal mitochondrial distribution, and mislocalized nectin-2; wild-type stem cell transplantation partially rescues these defects.\",\n      \"method\": \"Genetic knockout mice (nectin-3-/-), immunolocalization, spermatogenic stem cell transplantation rescue experiment\",\n      \"journal\": \"Genes to cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with specific phenotype, rescue by transplantation, and localization studies in a single study\",\n      \"pmids\": [\"16923130\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"CADM1 on mast cells mediates attachment to dorsal root ganglion (DRG) neurites and subsequent calcium responses via heterophilic binding to nectin-3 expressed on DRG neurons; a neutralizing antibody to nectin-3 inhibited both mast cell attachment and calcium signaling.\",\n      \"method\": \"Neutralizing antibody blocking assay, co-culture attachment assays, calcium imaging\",\n      \"journal\": \"Journal of neuroimmunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional blocking antibody with two readouts (adhesion and calcium), single lab\",\n      \"pmids\": [\"22703826\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"sFRP1 regulates spermatid adhesion and spermiation by suppressing phosphorylation of FAK (Tyr397), which in turn reduces phosphorylation and promotes retention of nectin-3 at the apical ectoplasmic specialization. In vivo administration of recombinant sFRP1 delayed spermiation with concurrent nectin-3 retention; overexpression in Sertoli-germ cell coculture confirmed FAK-nectin-3 phosphorylation axis.\",\n      \"method\": \"In vivo recombinant protein administration, lentiviral overexpression in coculture, Western blotting for phospho-FAK and phospho-nectin-3\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo and in vitro experiments with phosphorylation readouts, single lab\",\n      \"pmids\": [\"23073828\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Hippocampal nectin-3 is necessary for stress effects on spatial memory and dendritic spine density. Acute and chronic stress reduce hippocampal nectin-3 levels via CRH-CRHR1 signaling (not glucocorticoid receptor). Knockdown of hippocampal nectin-3 caused spatial memory deficits and spine loss; restoration of nectin-3 rescued early-life stress effects on memory and spine density in adulthood.\",\n      \"method\": \"AAV-mediated knockdown and overexpression, CRHR1 knockout mice, CRH-overexpressing transgenic mice, fear conditioning and spatial memory tasks, dendritic spine analysis\",\n      \"journal\": \"Nature neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple genetic models (KO, transgenic, AAV), bidirectional manipulation (KD and OE), multiple orthogonal behavioral and structural readouts\",\n      \"pmids\": [\"23644483\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Nectin-3 expressed on T lymphocytes trans-interacts with nectin-2 on high endothelial venules; blocking either nectin-3 (on lymphocytes) or nectin-2 (on ECs) with monoclonal antibodies inhibits lymphocyte transendothelial migration in vitro.\",\n      \"method\": \"Soluble nectin-3 binding assays, blocking monoclonal antibodies, transendothelial migration assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional blocking antibody approach with specific migration readout, single lab\",\n      \"pmids\": [\"24116228\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"MMP-9 proteolytically cleaves nectin-3 in the perisynaptic CA1 region following chronic restraint stress; this process involves NMDA receptor activation and is responsible for stress-induced social and cognitive alterations. Nectin-3 reduction was specific to CA1, not CA3.\",\n      \"method\": \"Gelatinase activity assays, MMP-9 inhibition, NMDA receptor antagonism, immunohistochemistry, behavioral assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — enzymatic cleavage assay plus pharmacological dissection of upstream pathway and behavioral readouts, multiple orthogonal methods\",\n      \"pmids\": [\"25232752\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In Nectin-3-deficient mice, hair cells aberrantly contact each other and form abnormal junctions; this leads to disturbed hair bundle orientation and morphology, abnormal kinocilium positioning, and mislocalization of cadherin-catenin complexes and polarity proteins Pals1 and Par-3 specifically in the aberrantly attached (not unattached) HCs.\",\n      \"method\": \"Nectin-3 knockout mice, immunofluorescence, confocal and electron microscopy\",\n      \"journal\": \"Development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with specific structural phenotype, mechanistic link between aberrant junction formation and polarity protein mislocalization demonstrated\",\n      \"pmids\": [\"24381198\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Crystal structure of the afadin PDZ domain (AFPDZ) in complex with the nectin-3 C-terminal peptide revealed that the last three C-terminal amino acids of nectin-3 (containing two hydrophobic residues of the class II motif) are sufficient for AFPDZ binding, and binding induces a ~2.5 Å-wider ligand-binding groove in AFPDZ compared to unliganded structures.\",\n      \"method\": \"X-ray crystallography of AFPDZ-nectin-3 fusion protein complex\",\n      \"journal\": \"Protein science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with defined binding interface, single lab\",\n      \"pmids\": [\"25534554\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Nectin-3 sialylation is regulated by TGFBR2 signaling in colon cancer cells; upon TGFBR2 reconstitution, nectin-3 loses sialic acid incorporation, identifying nectin-3 as a glycoprotein target of TGFBR2-dependent glycome regulation.\",\n      \"method\": \"RMCE-based TGFBR2 reconstitution, Click-It chemistry for sialic acid labeling, mass spectrometry\",\n      \"journal\": \"Protein science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — mass spectrometry-based glycoproteomics with reconstitution, single lab, single method for nectin-3 specifically\",\n      \"pmids\": [\"26177744\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Nectin-3 is present in rat uterine epithelial cells as three isoforms (80, 60, 32 kDa) and redistributes from basal cytoplasmic localization to cell junctions at the time of implantation (day 6); this junctional localization is regulated by progesterone. At implantation, nectin-3 localizes to the tight junction but does not interact with occludin or l-afadin.\",\n      \"method\": \"Immunofluorescence, Western blotting, co-immunoprecipitation, progesterone manipulation\",\n      \"journal\": \"Reproductive sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP (negative for occludin/l-afadin), immunofluorescence with hormonal manipulation, multiple methods in single lab\",\n      \"pmids\": [\"27217376\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Nectin-3 protein in spermatids is internalized at tubulobulbar complexes (clathrin/actin-based junction-internalizing structures) at Sertoli-spermatid junctions; nectin-3 labeling occurs at junctions, tubulobulbar complex bulbs, and associated double-membrane vesicles, with Rab5 associating with bulbs before scission.\",\n      \"method\": \"Pre-embedding immunoelectron microscopy with Rab5, EEA1, and nectin-3 antibodies\",\n      \"journal\": \"Anatomical record\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — high-resolution immunoelectron microscopy localizing nectin-3 to specific endocytic structures, single lab\",\n      \"pmids\": [\"28176461\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"AAV-mediated knockdown of nectin-3 in dentate gyrus neurons impaired long-term spatial memory and temporal order memory, increased density of immature doublecortin+ and calretinin+ neurons but decreased calbindin immunoreactivity, indicating nectin-3 modulates differentiation/maturation of adult-born granule cells. Selective nectin-3 knockdown in new DG neurons via retrovirus reduced thin dendritic spines.\",\n      \"method\": \"AAV-mediated knockdown, retroviral labeling of newborn neurons, immunohistochemistry for neurogenesis markers, behavioral testing\",\n      \"journal\": \"Translational psychiatry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two targeting strategies (AAV broad and retroviral newborn-specific), multiple orthogonal cellular and behavioral readouts, single lab\",\n      \"pmids\": [\"28872640\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"ZNF582 directly regulates transcription of nectin-3 (and NRXN3) as shown by ChIP-seq and ChIP-qPCR; restoration or abrogation of nectin-3 reversed the tumor suppressor effect of ZNF582 on NPC migration and invasion in vitro and in vivo.\",\n      \"method\": \"ChIP-seq, ChIP-qPCR, luciferase reporter assay, rescue/epistasis experiments with nectin-3 overexpression/knockdown\",\n      \"journal\": \"Cancer communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP-seq with functional epistasis rescue, single lab\",\n      \"pmids\": [\"33038291\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"AAV-mediated knockdown of nectin-3 in mouse medial prefrontal cortex (mPFC) during adolescence reproduced chronic stress-induced impairments in social recognition and spatial working memory, and reduced dendritic complexity and spine density; membrane localization of nectin-3 was significantly correlated with behavioral performance.\",\n      \"method\": \"AAV-mediated knockdown, behavioral testing, dendritic morphology analysis, membrane fractionation\",\n      \"journal\": \"Neuroscience bulletin\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with specific behavioral and structural readouts, single lab\",\n      \"pmids\": [\"32385776\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Precise levels of nectin-3 in visual cortex layer 2/3 neurons regulate dendritic spine density during synaptogenesis. Knockdown increased dendritic spine density at P21/P35; overexpression decreased it. Overexpression of nectin-3 lacking its afadin-binding domain caused an even greater decrease in spine density on basal dendrites, indicating the afadin-binding domain is important for nectin-3's role in spine formation.\",\n      \"method\": \"In utero electroporation with shRNA knockdown and full-length/truncated overexpression constructs; spine density analysis at multiple developmental timepoints\",\n      \"journal\": \"Neural development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — bidirectional manipulation with domain-deletion mutant, multiple timepoints, single lab\",\n      \"pmids\": [\"33160402\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Nectin-3, previously characterized as an adherens junction protein, is also localized to the brush border of colonocytes and can serve as a cell surface receptor for Clostridioides difficile toxin B (TcdB) on colonic epithelial cells.\",\n      \"method\": \"Immunofluorescence microscopy on colonic tissue, receptor localization studies\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — immunofluorescence localization establishing unexpected receptor site, single lab, limited mechanistic depth on binding mechanism\",\n      \"pmids\": [\"37747247\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Knockdown of dorsal CA1 nectin-3 impaired object recognition memory in adolescent female mice, while overexpression of dorsal CA1 nectin-3 reversed early-life stress-induced recognition memory deficits. Systemic CRHR1 antagonism (antalarmin) upregulated hippocampal nectin-3 levels and rescued memory deficits, placing nectin-3 downstream of CRHR1 signaling.\",\n      \"method\": \"AAV-mediated knockdown and overexpression, pharmacological CRHR1 antagonism, novel object recognition behavioral testing\",\n      \"journal\": \"Neuroscience bulletin\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — bidirectional AAV manipulation plus pharmacological epistasis, single lab\",\n      \"pmids\": [\"39395912\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PCP signaling (via Vangl2) regulates the junctional localization of Nectin-3 in cochlear supporting cells; loss of Nectin-3 partially phenocopies SGNII peripheral afferent turning defects seen in Vangl2 mutants. Epistasis analysis indicates Nectin-3 and Rac1 act in the same genetic pathway downstream of PCP to control SGNII axon guidance, with Nectin-3 likely providing a cell adhesion function for afferent turning.\",\n      \"method\": \"Genetic loss-of-function (Nectin-3 and Rac1 conditional knockouts), epistasis with Vangl2 mutants, immunofluorescence of junctional protein localization\",\n      \"journal\": \"Development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with two genes in the same pathway, specific axon guidance phenotype, single lab\",\n      \"pmids\": [\"40207531\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NECTIN-3 is a Ca2+-independent immunoglobulin-like cell adhesion molecule that forms cis-homodimers and engages in trans-homo- and trans-hetero-interactions (with nectin-1, nectin-2, Necl-5/CD155, and CADM1) through its V-domain to organize adherens junctions, Sertoli-spermatid junctions, and synaptic contacts; its cytoplasmic C-terminal class II PDZ-binding motif (EXYV) binds the afadin PDZ domain to link it to the actin cytoskeleton, and its junctional retention/removal is regulated by FAK phosphorylation, MMP-9 proteolytic cleavage, and clathrin-dependent endocytosis triggered by Necl-5 interaction, while in the hippocampus and prefrontal cortex it is transcriptionally and post-translationally regulated downstream of CRH-CRHR1 signaling to control dendritic spine density, adult neurogenesis, and memory.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"NECTIN3 is a Ca2+-independent immunoglobulin-like cell adhesion molecule that organizes cell-cell junctions across epithelial, germ cell, and neuronal tissues by forming cis-homodimers and engaging trans-homophilic and trans-heterophilic contacts through its membrane-distal V domain [#0, #2]. Its heterophilic partnerships are functionally specialized: high-affinity V-to-V trans-interaction with nectin-1 mediates apex-apex adhesion of ciliary epithelia [#2, #7], trans-interaction with nectin-2 builds Sertoli-spermatid junctions required for spermatid development and lymphocyte transendothelial migration [#9, #13], and heterophilic engagement with Necl-5/CD155 recruits afadin, E-cadherin, and catenins to nucleate adherens junctions [#4, #6]. The cytoplasmic C-terminal class II PDZ-binding motif (EXYV) binds the afadin PDZ domain — the terminal residues are sufficient for binding and widen the PDZ groove — linking nectin-3 to the actin cytoskeleton [#1, #16]. Junctional retention versus removal of nectin-3 is dynamically regulated: FAK (Tyr397)-dependent phosphorylation controls retention at the apical ectoplasmic specialization [#11], clathrin-dependent endocytosis triggered by Necl-5 interaction down-regulates surface levels to enforce contact inhibition [#8], and MMP-9 proteolytically cleaves perisynaptic nectin-3 [#14]. Through these mechanisms nectin-3 enforces correct junctional geometry and polarity protein localization in hair cells and cochlear supporting cells downstream of PCP/Vangl2-Rac1 signaling [#15, #26]. In the hippocampus and prefrontal cortex, nectin-3 acts downstream of CRH-CRHR1 signaling to control dendritic spine density, adult neurogenesis, and memory, with its afadin-binding domain required for spine regulation [#12, #20, #23, #24]. Nectin-3 also serves as a brush-border receptor for Clostridioides difficile toxin B on colonic epithelium [#24].\"\n  ,\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Establishing nectin-3 as an adhesion molecule required defining how it self-associates and partners with other nectins; this showed it drives homophilic adhesion and links to the cytoskeleton via afadin.\",\n      \"evidence\": \"Cell adhesion assays, reciprocal Co-IP, and immunofluorescence colocalization across nectin family members\",\n      \"pmids\": [\"10744716\", \"11024295\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of trans-interaction not resolved\", \"Quantitative affinities of homo- vs hetero-interaction not measured at this stage\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"It was unknown which structural elements drive nectin-3/nectin-1 binding; domain-swap and SPR work mapped a high-affinity (~1 nM) V-to-V interface with C-domain affinity contributions.\",\n      \"evidence\": \"Surface plasmon resonance, chimeric nectin1/PVR domain-swaps, and antibody/glycoprotein D competition\",\n      \"pmids\": [\"12011057\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Co-crystal structure of the trans-dimer not determined\", \"Whether the same interface governs nectin-2 and Necl-5 binding not tested\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Defining the partner repertoire beyond nectins, nectin-3 was shown to trans-interact heterophilically with Necl-5/CD155 (but not homophilically), promoting cell motility and bridging cell-cell to cell-matrix adhesion.\",\n      \"evidence\": \"Cell-based ligand binding, motility assays, Co-IP, and integrin microdomain colocalization\",\n      \"pmids\": [\"12740392\", \"12759359\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Necl-5 does not bind afadin, leaving its cytoplasmic coupling unclear\", \"Direct physical link between nectin and integrin systems inferred from colocalization\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"The downstream consequence of Necl-5/nectin-3 engagement was unresolved; reconstitution showed afadin, E-cadherin, and catenins are recruited specifically to the nectin-3 side to nucleate adherens junctions.\",\n      \"evidence\": \"Stable reconstituted cell lines, immunofluorescence, and blocking antibodies; parallel work mapped Necl-5-driven migration to integrin alphaVbeta3/Cdc42/Rac\",\n      \"pmids\": [\"15330856\", \"14871893\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Why recruitment is asymmetric to the nectin-3 side mechanistically unexplained\", \"Migration arm is nectin-3-independent, so two functions are coupled only at the receptor level\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"How nectins regulate contact inhibition was unknown; nectin-3 was shown to trigger clathrin-dependent endocytic down-regulation of Necl-5, reducing movement and proliferation, while in vivo two knockouts established a requirement for nectin-1/nectin-3 apex-apex adhesion in ciliary epithelia.\",\n      \"evidence\": \"Surface down-regulation assays with clathrin inhibitors; nectin-1-/- and nectin-3-/- mice with immuno-EM\",\n      \"pmids\": [\"16216929\", \"15728677\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Adaptor machinery driving clathrin recruitment to nectin-3 not identified\", \"Generality of endocytic regulation beyond Necl-5 untested\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"The physiological role of nectin-3 heterophilic adhesion was tested genetically; nectin-3-/- mice are male-infertile with disrupted Sertoli-spermatid junctions and mislocalized nectin-2, rescued by wild-type stem cell transplantation.\",\n      \"evidence\": \"Nectin-3 knockout mice, immunolocalization, spermatogenic stem cell transplantation rescue\",\n      \"pmids\": [\"16923130\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cell-autonomous vs non-autonomous contribution only partly resolved by transplantation\", \"Signaling consequences of junction loss not defined\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Mechanisms controlling junctional retention and new partner contexts were addressed; FAK(Tyr397)/sFRP1 signaling controls nectin-3 retention at the apical ectoplasmic specialization, and CADM1-nectin-3 mediates mast cell-neurite attachment with calcium signaling.\",\n      \"evidence\": \"In vivo recombinant sFRP1, coculture overexpression with phospho-FAK/phospho-nectin-3 blots; neutralizing-antibody adhesion and calcium imaging\",\n      \"pmids\": [\"23073828\", \"22703826\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct phosphorylation site on nectin-3 not mapped\", \"Whether FAK acts directly on nectin-3 or via intermediates unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"A neuronal function was established; hippocampal nectin-3 is required for stress effects on spatial memory and spine density, with stress reducing nectin-3 via CRH-CRHR1 (not glucocorticoid receptor) signaling, and restoration rescuing early-life stress deficits.\",\n      \"evidence\": \"AAV knockdown/overexpression, CRHR1 KO and CRH-transgenic mice, behavioral and spine analyses; parallel nectin-2/nectin-3 blockade inhibited lymphocyte transendothelial migration\",\n      \"pmids\": [\"23644483\", \"24116228\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link from CRHR1 signaling to nectin-3 transcription/turnover not fully defined\", \"Synaptic partner mediating spine effects in vivo not identified\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Post-translational removal of synaptic nectin-3 and its role in tissue patterning were resolved; MMP-9 cleaves perisynaptic CA1 nectin-3 downstream of NMDA receptor activation under chronic stress, and nectin-3 loss causes aberrant hair-cell contacts with polarity protein mislocalization.\",\n      \"evidence\": \"Gelatinase assays, MMP-9/NMDAR pharmacology, behavior; nectin-3 KO mice with confocal/EM and polarity protein staining\",\n      \"pmids\": [\"25232752\", \"24381198\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cleavage site on nectin-3 not mapped\", \"How aberrant adhesion drives polarity protein mislocalization mechanistically unclear\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"The structural basis of cytoskeletal coupling and a glycosylation control point were defined; the nectin-3 C-terminal triresidue is sufficient for afadin PDZ binding and widens the groove, while TGFBR2 signaling controls nectin-3 sialylation in colon cancer.\",\n      \"evidence\": \"X-ray crystallography of AFPDZ-nectin-3 complex; TGFBR2 reconstitution with click-chemistry sialic acid labeling and mass spectrometry\",\n      \"pmids\": [\"25534554\", \"26177744\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of nectin-3 sialylation change not established\", \"Single-method evidence for the glycosylation finding\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"The trafficking route for nectin-3 removal and an additional neuronal role were characterized; nectin-3 is internalized via Rab5-associated tubulobulbar complexes at Sertoli-spermatid junctions, and dentate gyrus nectin-3 modulates adult-born neuron maturation and memory.\",\n      \"evidence\": \"Immuno-EM with Rab5/EEA1; AAV and retroviral newborn-neuron-specific knockdown with neurogenesis markers and behavior\",\n      \"pmids\": [\"28176461\", \"28872640\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Endocytic adaptors linking nectin-3 to tubulobulbar complexes not identified\", \"Molecular targets coupling nectin-3 to differentiation markers unknown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Transcriptional and circuit-level regulation were extended; ZNF582 directly represses nectin-3 to suppress nasopharyngeal carcinoma invasion, mPFC nectin-3 mediates adolescent stress effects on behavior and spines, and the afadin-binding domain was shown to be required for nectin-3's spine-density control in visual cortex.\",\n      \"evidence\": \"ChIP-seq/ChIP-qPCR with rescue epistasis; AAV mPFC knockdown with membrane fractionation; in utero electroporation with afadin-binding-deletion constructs\",\n      \"pmids\": [\"33038291\", \"32385776\", \"33160402\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether ZNF582 regulation operates outside NPC unknown\", \"Direct synaptic mechanism by which afadin coupling shapes spines not resolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"An unexpected functional role at the colonic surface was identified; nectin-3 localizes to the colonocyte brush border and serves as a receptor for Clostridioides difficile toxin B.\",\n      \"evidence\": \"Immunofluorescence on colonic tissue and receptor localization studies\",\n      \"pmids\": [\"37747247\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Binding interface between TcdB and nectin-3 not mapped\", \"Functional contribution to in vivo toxin entry not quantified\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Causal placement of nectin-3 downstream of CRHR1 in memory was strengthened, and a PCP-Rac1 axis controlling its junctional localization in axon guidance was defined.\",\n      \"evidence\": \"AAV bidirectional manipulation with CRHR1 antagonism (antalarmin); Nectin-3/Rac1 conditional KO epistasis with Vangl2 mutants and junctional protein staining\",\n      \"pmids\": [\"39395912\", \"40207531\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct molecular signal from CRHR1 to nectin-3 still indirect\", \"How PCP signaling positions nectin-3 at the junction mechanistically unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the same V-domain adhesion code is selectively read out into distinct outcomes (junction assembly, endocytic contact inhibition, spine regulation, toxin entry) across tissues remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model linking partner choice to downstream signaling output\", \"Tissue-specific regulators of nectin-3 turnover incompletely defined\", \"Structure of full trans-adhesion complex unsolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [0, 2, 7, 9]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 16]},\n      {\"term_id\": \"GO:0001618\", \"supporting_discovery_ids\": [24]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 4, 18, 24]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 1, 16]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1500931\", \"supporting_discovery_ids\": [0, 6, 7]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [12, 20, 23]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [7, 9, 15, 26]}\n    ],\n    \"complexes\": [\"nectin-afadin adhesion complex\", \"adherens junction\"],\n    \"partners\": [\"AFDN\", \"NECTIN1\", \"NECTIN2\", \"PVR\", \"CADM1\", \"PTK2\", \"MMP9\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}