{"gene":"PATJ","run_date":"2026-06-10T05:19:53","timeline":{"discoveries":[{"year":2002,"finding":"PATJ (hINADL) interacts with human Crumbs3 (CRB3) through the CRB3 C-terminal end binding to the N-terminal domain of PATJ, and localizes to tight junctions and apical plasma membrane in human intestinal epithelial cells; overexpression of PATJ disrupted ZO-1 and ZO-3 tight junction localization.","method":"Co-immunoprecipitation, overexpression/dominant-negative experiment, immunofluorescence localization in Caco-2 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal interaction mapped, localization confirmed, functional consequence of overexpression documented, single lab with multiple orthogonal methods","pmids":["11964389"],"is_preprint":false},{"year":2005,"finding":"PATJ is targeted to the apical region and tight junctions upon initiation of cell polarization; RNAi-mediated reduction of PATJ delays tight junction formation and causes cell polarity defects, which are reversed by PATJ reintroduction, establishing PATJ as a functional polarity protein in mammalian epithelial cells.","method":"RNAi knockdown, rescue by reintroduction, immunofluorescence, tight junction formation assay in MDCK cells","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — loss-of-function with defined phenotype plus rescue experiment, single lab with multiple orthogonal methods","pmids":["15738264"],"is_preprint":false},{"year":2005,"finding":"PATJ knockdown in Caco2 cells causes Pals1 to dissociate from tight junctions, Crumbs3 to accumulate in an early endosome-related compartment near the apical membrane, and mislocalization of occludin and ZO-3 to the lateral membrane, demonstrating that PATJ connects and stabilizes apical and lateral components of tight junctions.","method":"Stable shRNA knockdown, immunofluorescence, subcellular fractionation in Caco2 cells","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Moderate — stable knockdown with multiple defined molecular readouts, single lab","pmids":["16129888"],"is_preprint":false},{"year":2005,"finding":"The L27 domain of PATJ forms a heterodimeric complex with the L27N domain of Pals1, assembling into a tetrameric structure (two heterodimer units); the C-terminal alpha-helix of each L27 domain is a critical specificity determinant for partner selection.","method":"NMR solution structure determination, biochemical binding assays, site-directed analysis of L27 domain complexes","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution NMR structure plus biochemical validation, establishes structural mechanism of PATJ-Pals1 L27 complex assembly","pmids":["15863617"],"is_preprint":false},{"year":2007,"finding":"PATJ is required for directional migration of epithelial cells; PATJ RNAi in MDCKII cells disrupts localization of aPKC and Par3 to the leading edge and disorganizes the microtubule-organizing center orientation during wound-induced migration.","method":"RNAi knockdown, wound-induced migration assay, immunofluorescence of aPKC/Par3 at leading edge, MTOC orientation analysis","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — clean loss-of-function with specific cellular phenotype and molecular readouts (aPKC/Par3 mislocalization, MTOC defect), single lab with multiple orthogonal assays","pmids":["17235357"],"is_preprint":false},{"year":2007,"finding":"HPV16 and HPV18 E6 proteins bind PATJ through E6's C-terminal PDZ-binding motif and target PATJ for degradation; additionally, the alternatively spliced 18 E6* isoform (lacking a C-terminal PDZ-binding motif) also associates with and degrades PATJ independently, and 18 E6-mediated PATJ degradation is not inhibited by shRNA silencing of E6AP.","method":"Co-immunoprecipitation, protein degradation assays, shRNA silencing of E6AP, isoform comparison experiments in epithelial cells","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple binding/degradation assays with isoform dissection and E6AP genetic test, single lab, multiple orthogonal methods","pmids":["17287269"],"is_preprint":false},{"year":2008,"finding":"PATJ (and its paralogue Mupp1) forms a ternary complex with angiomotin (Amot) and the RhoA GEF Syx; this Amot:Patj/Mupp1:Syx complex controls spatial targeting of RhoA activity to lamellipodia in migrating endothelial cells.","method":"Peptide pull-down, yeast two-hybrid screening, FRET analysis of RhoA activity in lamellipodia, morpholino knockdown in zebrafish","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Moderate — ternary complex identified by multiple methods (pull-down, Y2H), RhoA activity measured by FRET, in vivo zebrafish validation; single lab but orthogonal methods","pmids":["18824598"],"is_preprint":false},{"year":1998,"finding":"CIPP (PATJ/INADL) selectively binds via its PDZ domains to Kir4.1 and Kir4.2 inward rectifier K+ channels, NMDA receptor subunits, neurexins, and neuroligins; co-expression of CIPP with Kir4.1 in COS-7 cells doubles Kir4.1 current density.","method":"Yeast two-hybrid, GST pull-down, whole-cell voltage clamp electrophysiology in COS-7 cells","journal":"Molecular and cellular neurosciences","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro binding assays combined with functional electrophysiological readout (current density), single lab with multiple orthogonal methods","pmids":["9647694"],"is_preprint":false},{"year":2002,"finding":"CIPP (PATJ/INADL) PDZ4 domain interacts with ASIC3 C-terminal region; co-expression of CIPP with ASIC3 in COS cells increases ASIC3 peak current density 5-fold and slightly shifts pH0.5 from 6.2 to 6.4, consistent with enhanced surface expression of ASIC3.","method":"Yeast two-hybrid, co-immunoprecipitation, whole-cell patch-clamp electrophysiology in COS cells, in situ hybridization","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — PDZ domain-substrate interaction mapped and functional consequence (increased current) measured electrophysiologically, single lab with multiple orthogonal methods","pmids":["11872753"],"is_preprint":false},{"year":2001,"finding":"The seven PDZ domains of human INADL (PATJ) each have distinct binding specificities for C-terminal peptide ligands, falling into class I, class II, and a novel class IV (characterized by an acidic residue at the C-terminal position); site-directed mutagenesis of contact residues confirmed involvement of specific pocket residues in binding preference.","method":"Combinatorial phage-display peptide library screening, homology modeling, site-directed mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — peptide binding preferences determined experimentally by phage display, confirmed by mutagenesis; single lab with multiple orthogonal methods","pmids":["11509564"],"is_preprint":false},{"year":2009,"finding":"PATJ shares binding partners with MUPP1 including JAM1, ZO-3, Pals1, Par6, and nectins, and uses overlapping mechanisms for tight junction localization; however, unlike MUPP1, PATJ is indispensable for tight junction establishment and epithelial polarization, with Pals1 showing higher affinity for PATJ than MUPP1, and Pals1-mediated activation of the Par6-aPKC complex being critical for PATJ function.","method":"Co-immunoprecipitation, binding affinity comparison, RNAi knockdown of PATJ vs MUPP1, immunofluorescence","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — comparative knockdown of paralogs with defined molecular phenotypes, binding affinity measurements, multiple orthogonal methods, single lab","pmids":["19255144"],"is_preprint":false},{"year":2009,"finding":"PATJ physically interacts with nephrocystin-1 (NPHP1) and nephrocystin-4 (NPHP4) and co-localizes with them in human renal tubules; knockdown of NPHP1 or NPHP4 phenocopies loss of PALS1/Par3, producing tight junction formation defects similar to those seen with PATJ/PALS1 depletion.","method":"Co-immunoprecipitation, shRNA knockdown in MDCK cells, immunofluorescence, 3D collagen matrix culture","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — physical interaction shown by co-IP and co-localization, but the functional linkage to PATJ is inferred from epistasis/phenotypic similarity rather than direct PATJ epistasis experiment; single lab","pmids":["19755384"],"is_preprint":false},{"year":2012,"finding":"Drosophila PATJ directly binds the Myosin-binding subunit (MBS) of Myosin phosphatase and decreases Myosin dephosphorylation, resulting in activated (phosphorylated) Myosin; this supports stability of the Zonula Adherens, and loss of PATJ leads sequentially to Myosin loss from AJ, AJ disassembly, and loss of apical-basal polarity.","method":"Direct binding assay (pull-down), Myosin phosphorylation assays, PATJ mutant analysis in Drosophila epithelium, immunofluorescence","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct binding demonstrated, enzymatic (phosphatase inhibition) mechanism established, in vivo genetic loss-of-function with ordered phenotypic readouts; single lab, multiple orthogonal methods","pmids":["23128243"],"is_preprint":false},{"year":2012,"finding":"In Drosophila, the first PDZ domain of Patj together with its Stardust-binding (L27) domain are sufficient to fully rescue viability and Crumbs localization in null Patj mutants; Patj null mutants are lethal but Patj is dispensable for ectoderm polarity while being required in follicular epithelium where it supports Crumbs complex apical localization. Gain-of-function of Crumbs and Patj mutation genetically suppress each other in follicular cells.","method":"Generation of null Drosophila Patj mutants, domain truncation rescue experiments, genetic epistasis (Crumbs gain-of-function × Patj mutant), immunofluorescence","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Moderate — null mutant with domain rescue and genetic epistasis, multiple orthogonal methods, single lab","pmids":["23136386"],"is_preprint":false},{"year":2012,"finding":"Crystal structure of the L27(PATJ)-(L27N,L27C)(Pals1)-L27(MALS2) heterotrimer reveals two cognate pairs of heterodimeric L27 domains that assemble mutually independently; biochemical data confirm this independent assembly mode also applies to DLG1/CASK/Mals2.","method":"X-ray crystallography (2.05 Å resolution), biochemical binding assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with biochemical validation, defines molecular mechanism of tripartite complex assembly","pmids":["22337881"],"is_preprint":false},{"year":2013,"finding":"MUPP-1 levels inversely regulate PATJ protein levels by controlling stability of the PATJ/PALS-1 complex; upon MUPP-1 depletion, increased PATJ localizes at the migrating front and recruits more PAR3, indicating at least two distinct pools of PALS-1 complexes (PALS-1/MUPP-1 and PALS-1/PATJ) co-exist in epithelial cells.","method":"siRNA depletion, co-immunoprecipitation, immunofluorescence, western blotting in MCF10A cells","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — knockdown with defined molecular and localization readouts, single lab, single set of experiments","pmids":["23880463"],"is_preprint":false},{"year":2010,"finding":"CIPP (PATJ/INADL) forms a tripartite complex with IRSp53 and Cypin in neuronal cells; CIPP acts as a bridge linking the C-termini of IRSp53 and Cypin via its PDZ domains, and IRSp53 connects to Cypin via an SH3-mediated interaction requiring two positively charged Cypin residues; the three proteins co-localize at the tips of neuronal protrusions.","method":"Co-immunoprecipitation in cultured cells, domain mapping with PDZ domains, SH3-domain interaction mutagenesis, co-localization by immunofluorescence in neuronal cells","journal":"Biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — complex demonstrated by co-IP, interaction domains mapped by mutagenesis, localization confirmed; single lab","pmids":["20707603"],"is_preprint":false},{"year":2009,"finding":"CIPP (PATJ/INADL) PDZ2 directly binds IRSp53 C-terminus; co-transfection of CIPP with IRSp53 in mammalian cells induces reorganization of CIPP into large punctate multi-protein assemblies that are not cytoplasmic vesicles.","method":"GST pull-down with individual PDZ domains, co-transfection/co-localization, endocytic marker co-staining","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — PDZ domain mapped by pull-down, localization effect documented; single lab, single method per finding","pmids":["19138174"],"is_preprint":false},{"year":2023,"finding":"PATJ knockout in epithelial cells causes tight junction defects, disturbed apical-basal polarity, and impaired lumen formation in 3D cysts; mechanistically, PATJ associates with and inhibits HDAC7, and HDAC7 inhibition/knockdown rescues the polarity and lumen phenotypes; PATJ-mediated regulation of HDAC7 controls expression of genes involved in cell junction assembly and membrane organization; this HDAC7-regulatory function is independent of Pals1 binding.","method":"CRISPR-Cas9 knockout, 3D cyst assay, co-immunoprecipitation (PATJ-HDAC7), HDAC7 inhibitor/siRNA rescue, RNA-seq gene expression analysis","journal":"Cellular and molecular life sciences : CMLS","confidence":"High","confidence_rationale":"Tier 2 / Moderate — CRISPR KO with multiple phenotypic readouts, novel interaction mapped by co-IP, pharmacologic and genetic rescue with orthogonal approaches; single lab","pmids":["37878054"],"is_preprint":false},{"year":2023,"finding":"In mouse preimplantation embryos, PATJ and MPDZ together are required for blastocyst formation and trophectoderm lineage specification; double depletion disrupts the apical CRB and PAR polarity complexes, tight junctions, and actin filaments in outer cells, leading to ectopic Hippo signaling activation, reduced YAP nuclear localization, suppressed Cdx2 expression, and failure of trophectoderm differentiation.","method":"Zygote microinjection of RNAi constructs, immunofluorescence for polarity/junction markers, Hippo pathway readouts (YAP phosphorylation/localization), transcription factor expression analysis","journal":"Reproduction (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — loss-of-function in vivo with multiple molecular readouts linking PATJ to polarity complex integrity and Hippo/YAP signaling; single lab, single organism model","pmids":["37318097"],"is_preprint":false},{"year":2021,"finding":"CIPP (PATJ/INADL) interacts via its PDZ domains with the C-terminal PDZ-binding motif of the serotonin 5-HT2B receptor; co-expression of CIPP increases 5-HT2B receptor clustering at neuronal surfaces, prevents receptor dispersion after agonist stimulation, and potentiates inositol phosphate production and calcium mobilization; CIPP, 5-HT2B, and NMDA receptor NR1 subunit form a macromolecular complex.","method":"Peptide affinity chromatography/mass spectrometry, co-immunoprecipitation in COS-7 cells, IP measurement, calcium imaging, immunofluorescence in hippocampal neurons","journal":"ACS chemical neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ternary complex identified by co-IP, functional consequences measured by IP/calcium assays, localization by immunofluorescence; single lab with multiple orthogonal methods","pmids":["33739808"],"is_preprint":false},{"year":2025,"finding":"PATJ knockout in HEK293 cells alters YAP1 nuclear translocation, and PATJ deletion causes transcriptional reprogramming including dysregulation of vascular/stress-response genes (RUNX1, HEY1, NUPR1, HK2); in C. elegans, the PATJ homolog mpz-1 is upregulated under hypoxia and its knockdown causes abnormal neuronal morphology and increased mortality exacerbated by hypoxia.","method":"CRISPR-Cas9 knockout, YAP1 nuclear translocation assay, RNA-seq, C. elegans mpz-1 knockdown/hypoxia experiments","journal":"Redox biology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — CRISPR KO with defined YAP1 localization readout and transcriptional analysis; C. elegans ortholog loss-of-function; single lab","pmids":["40472775"],"is_preprint":false},{"year":2025,"finding":"PATJ conditional knockout in T cells impairs immunological synapse (IS) formation and T cell activation in vitro and in vivo; PATJ expression increases rapidly upon T cell activation; a specific minimal PDZ domain combination within PATJ is sufficient to support TCR signaling and, when engineered into a CAR construct, enhances CAR-T cell cytotoxicity against solid tumors.","method":"Conditional T cell-specific Patj knockout mice, confocal microscopy of IS formation, in vitro/in vivo T cell activation assays, PATJ truncation domain mapping, CAR-T cell cytotoxicity assay","journal":"Journal for immunotherapy of cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional KO with defined cellular phenotype, domain truncation mapping, functional assays; single lab, multiple orthogonal approaches","pmids":["40341028"],"is_preprint":false},{"year":2025,"finding":"PatJ (PATJ) is required for lumen initiation in MDCK-II cells; PatJ controls the architecture of the apical-lateral border and connects the tight junction to the apical cortex, and its loss impairs fusion of vacuolar apical compartments (VACs) at the apical membrane initiation site (AMIS) to generate a nascent lumen.","method":"Quantitative light and electron microscopy, proximity proteomics (BioID), loss-of-function experiments in MDCK-II cells, apical cargo trafficking assays","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — preprint, loss-of-function with defined ultrastructural and trafficking readouts; single lab","pmids":[],"is_preprint":true},{"year":2025,"finding":"PATJ zebrafish knockout (via homozygous truncating PATJ variant c.830delC validated in patient and zebrafish model) produces a ciliopathy phenotype including polycystic kidney disease and hydrocephalus, demonstrating an essential role for PATJ in cilia formation and function.","method":"Massively parallel sequencing (patient), zebrafish in vivo loss-of-function validation, ciliopathy phenotype characterization","journal":"HGG advances","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — human variant identified and validated in zebrafish model with defined ciliopathy phenotype; single lab, single variant","pmids":["40931526"],"is_preprint":false}],"current_model":"PATJ is a multi-PDZ domain scaffold protein that localizes to tight junctions and the apical membrane in polarized epithelial cells, where it forms the Crumbs-Pals1-PATJ complex via L27 domain heterodimerization with Pals1; it is required for tight junction formation, apical-basal polarity, directional cell migration, and lumen formation by connecting apical and lateral junction components, stabilizing Crumbs3, regulating aPKC/Par3 localization, and inhibiting HDAC7 to control epithelial gene expression; in neurons it acts as a synaptic scaffold (CIPP) clustering ion channels (Kir4.1, ASIC3) and receptors (NMDA, 5-HT2B) to modulate their surface expression and activity; in endothelial cells it anchors the Amot-Syx complex to spatially control RhoA GTPase activity; and in T cells its PDZ domains support immunological synapse formation and TCR signaling."},"narrative":{"mechanistic_narrative":"PATJ (also INADL/CIPP/hINADL) is a multi-PDZ-domain scaffold protein that organizes apical-basal polarity and tight junctions in epithelial cells by assembling the Crumbs3–Pals1–PATJ complex [PMID:11964389, PMID:16129888]. Its N-terminal L27 domain forms a heterodimer with the L27N domain of Pals1, and structural analysis shows these L27 modules build a tetrameric assembly in which cognate L27 pairs dock independently, providing the architectural basis for tripartite scaffold formation with partners such as MALS2 [PMID:15863617, PMID:22337881]. Through this scaffold PATJ connects and stabilizes apical and lateral junction components: its loss displaces Pals1 from junctions, traps Crumbs3 in an apical endosomal compartment, and mislocalizes occludin and ZO-3 to the lateral membrane, delaying tight junction formation and disrupting polarity in a manner rescued by re-expression [PMID:15738264, PMID:16129888]. PATJ is required for directional epithelial migration, positioning aPKC, Par3 and the MTOC at the leading edge [PMID:17235357], and for lumen formation in 3D cysts, where it shapes the apical-lateral border and connects the tight junction to the apical cortex. Beyond scaffolding, PATJ associates with and inhibits HDAC7 to control transcription of cell-junction and membrane-organization genes, a function independent of Pals1 binding [PMID:37878054]. The seven PDZ domains have distinct C-terminal peptide specificities spanning class I, II, and a novel class IV [PMID:11509564], underlying a diverse partner repertoire: in neurons (as CIPP) PATJ clusters and increases surface activity of Kir4.1 channels, ASIC3, NMDA receptor subunits, and the 5-HT2B receptor [PMID:9647694, PMID:11872753, PMID:33739808]; in endothelial cells it forms an Amot–PATJ–Syx complex that spatially targets RhoA activity to lamellipodia [PMID:18824598]; and in T cells it supports immunological synapse formation and TCR signaling [PMID:40341028]. PATJ is also a target of oncogenic HPV E6 proteins, which bind and degrade it [PMID:17287269]. A homozygous truncating PATJ variant produces a ciliopathy with polycystic kidney disease and hydrocephalus in patient and zebrafish, establishing an essential role in cilia [PMID:40931526].","teleology":[{"year":1998,"claim":"Established that the protein (CIPP) is a multi-PDZ scaffold that selectively binds and functionally regulates neuronal ion channels and receptors, defining its earliest molecular identity.","evidence":"Yeast two-hybrid, GST pull-down, and whole-cell voltage clamp of Kir4.1/NMDA partners in COS-7 cells","pmids":["9647694"],"confidence":"High","gaps":["Did not address epithelial junction roles","No structural basis for partner selection"]},{"year":2001,"claim":"Resolved how the seven PDZ domains achieve binding diversity, defining class I, II and a novel class IV specificity and explaining the protein's broad partner repertoire.","evidence":"Combinatorial phage-display peptide screening, homology modeling, and site-directed mutagenesis","pmids":["11509564"],"confidence":"High","gaps":["Peptide preferences not all matched to physiological partners","No domain occupancy in cells"]},{"year":2002,"claim":"Connected PATJ to epithelial apical junctions by showing it binds Crumbs3 and localizes to tight junctions, recasting the neuronal scaffold as a polarity component.","evidence":"Co-IP, overexpression/dominant-negative, and immunofluorescence in Caco-2 cells; ASIC3 binding/electrophysiology in COS cells","pmids":["11964389","11872753"],"confidence":"High","gaps":["Loss-of-function phenotype not yet tested","Mechanism of junction stabilization unknown"]},{"year":2005,"claim":"Demonstrated PATJ is functionally required for tight junction formation and polarity, and defined the structural L27–L27N heterodimer mechanism by which it binds Pals1.","evidence":"RNAi with rescue in MDCK/Caco2 cells, subcellular fractionation, and NMR solution structure of the L27 complex","pmids":["15738264","16129888","15863617"],"confidence":"High","gaps":["How PATJ stabilizes lateral occludin/ZO-3 mechanistically unresolved","Stoichiometry of full complex in vivo unclear"]},{"year":2007,"claim":"Extended PATJ function to directional migration and identified it as a target of oncogenic HPV E6, linking polarity scaffold loss to viral pathogenesis.","evidence":"RNAi migration/MTOC assays in MDCKII cells; E6 binding/degradation and E6AP silencing in epithelial cells","pmids":["17235357","17287269"],"confidence":"High","gaps":["E6AP-independent degradation pathway not identified","Direct link between migration defect and tumor phenotype untested"]},{"year":2008,"claim":"Showed PATJ spatially controls RhoA signaling by forming an Amot–PATJ–Syx complex in endothelial lamellipodia, generalizing its scaffolding role to GTPase regulation.","evidence":"Peptide pull-down, yeast two-hybrid, FRET RhoA biosensor, and zebrafish morpholino knockdown","pmids":["18824598"],"confidence":"High","gaps":["Overlap/distinction from Mupp1-containing complexes not fully resolved","Mechanism of RhoA spatial restriction incomplete"]},{"year":2012,"claim":"Established direct enzymatic and structural mechanisms: Drosophila PATJ inhibits Myosin phosphatase to maintain junction-stabilizing Myosin activation, and crystallography defined independent L27 pair assembly in the tripartite complex.","evidence":"Pull-down/phosphorylation assays and genetic rescue in Drosophila; X-ray crystallography of L27 heterotrimer; domain-rescue and epistasis in Drosophila","pmids":["23128243","22337881","23136386"],"confidence":"High","gaps":["Whether mammalian PATJ regulates Myosin phosphatase similarly untested","Tissue-specific dispensability (ectoderm vs follicle) mechanism unclear"]},{"year":2009,"claim":"Distinguished PATJ from its paralog MUPP1, showing shared partners but a non-redundant, indispensable PATJ role tied to higher Pals1 affinity, and linked PATJ to nephrocystins NPHP1/NPHP4.","evidence":"Comparative RNAi, affinity comparison, co-IP and 3D culture in epithelial/renal cells","pmids":["19255144","19138174","19755384"],"confidence":"High","gaps":["NPHP linkage inferred from phenotypic similarity rather than direct PATJ epistasis","Functional consequence of PATJ–IRSp53 binding not resolved"]},{"year":2013,"claim":"Revealed reciprocal regulation between PATJ and MUPP1 pools and assembled neuronal CIPP–IRSp53–Cypin tripartite complexes at protrusion tips, expanding the scaffold model.","evidence":"siRNA depletion and co-IP in MCF10A cells; domain-mapped co-IP in neuronal cells","pmids":["23880463","20707603"],"confidence":"Medium","gaps":["Single-lab, single experimental set for MUPP1/PATJ stability interplay","Physiological role of IRSp53–Cypin–CIPP complex untested"]},{"year":2023,"claim":"Uncovered a Pals1-independent transcriptional arm: PATJ inhibits HDAC7 to control junction/membrane gene expression and lumen formation, and PATJ/MPDZ govern blastocyst trophectoderm via Hippo/YAP.","evidence":"CRISPR KO with 3D cyst assay, PATJ–HDAC7 co-IP, inhibitor/siRNA rescue, RNA-seq; embryo RNAi with polarity and YAP readouts","pmids":["37878054","37318097"],"confidence":"Medium","gaps":["How PATJ inhibits HDAC7 mechanistically unknown","Embryo study limited to single organism and double-depletion design"]},{"year":2025,"claim":"Connected PATJ to lumen ultrastructure, T-cell immunological synapse signaling, YAP1-linked stress transcription, and a human ciliopathy, broadening its physiological and disease relevance.","evidence":"BioID/EM lumen analysis in MDCK-II (preprint); conditional T-cell KO and CAR engineering; CRISPR KO/RNA-seq and C. elegans hypoxia; patient variant validated in zebrafish","pmids":["40341028","40472775","40931526"],"confidence":"Medium","gaps":["Lumen role rests on a single preprint","Ciliopathy link based on a single variant/family","Mechanism connecting PATJ to ciliogenesis undefined"]},{"year":null,"claim":"How PATJ's distinct functional modules — Pals1-dependent junction scaffolding, Pals1-independent HDAC7 transcriptional control, RhoA/Myosin cytoskeletal regulation, and neuronal channel clustering — are partitioned and coordinated within a single cell remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No integrated model of how separate PATJ pools/domains are deployed","Mechanism of PATJ's role in ciliogenesis unknown","Direct enzymatic regulation of HDAC7 not characterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[3,14,16,0]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[9,7]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[12,18,7,8,20]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,23]},{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[24]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[6,19,22]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[4,19,13]}],"complexes":["Crumbs3-Pals1-PATJ apical polarity complex","Amot-PATJ-Syx complex","L27 PATJ-Pals1-MALS2 heterotrimer"],"partners":["PALS1","CRB3","HDAC7","AMOT","KCNJ10","ASIC3","IRSP53","MPDZ"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8NI35","full_name":"InaD-like protein","aliases":["Channel-interacting PDZ domain-containing protein","Pals1-associated tight junction protein","Protein associated to tight junctions"],"length_aa":1801,"mass_kda":196.4,"function":"Scaffolding protein that facilitates the localization of proteins to the cell membrane (PubMed:11927608, PubMed:16678097, PubMed:22006950). Required for the correct formation of tight junctions and epithelial apico-basal polarity (PubMed:11927608, PubMed:16678097). Acts (via its L27 domain) as an apical connector and elongation factor for multistranded TJP1/ZO1 condensates that form a tight junction belt, thereby required for the formation of the tight junction-mediated cell barrier (By similarity). Positively regulates epithelial cell microtubule elongation and cell migration, possibly via facilitating localization of PRKCI/aPKC and PAR3D/PAR3 at the leading edge of migrating cells (By similarity). Plays a role in the correct reorientation of the microtubule-organizing center during epithelial migration (By similarity). May regulate the surface expression and/or function of ASIC3 in sensory neurons (By similarity). May recruit ARHGEF18 to apical cell-cell boundaries (PubMed:22006950)","subcellular_location":"Cell junction, tight junction; Apical cell membrane; Cytoplasm, perinuclear region","url":"https://www.uniprot.org/uniprotkb/Q8NI35/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PATJ","classification":"Not Classified","n_dependent_lines":4,"n_total_lines":1208,"dependency_fraction":0.0033112582781456954},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PATJ","total_profiled":1310},"omim":[{"mim_id":"612689","title":"TIGHT JUNCTION PROTEIN 3; TJP3","url":"https://www.omim.org/entry/612689"},{"mim_id":"611730","title":"ERYTHROCYTE MEMBRANE PROTEIN BAND 4.1-LIKE 5; EPB41L5","url":"https://www.omim.org/entry/611730"},{"mim_id":"609737","title":"CRUMBS CELL POLARITY COMPLEX COMPONENT 3; CRB3","url":"https://www.omim.org/entry/609737"},{"mim_id":"608293","title":"RHO GTPase-ACTIVATING PROTEIN 17; ARHGAP17","url":"https://www.omim.org/entry/608293"},{"mim_id":"607465","title":"CODANIN 1; CDAN1","url":"https://www.omim.org/entry/607465"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cell Junctions","reliability":"Supported"},{"location":"Centriolar satellite","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in 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overexpression of PATJ disrupted ZO-1 and ZO-3 tight junction localization.\",\n      \"method\": \"Co-immunoprecipitation, overexpression/dominant-negative experiment, immunofluorescence localization in Caco-2 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal interaction mapped, localization confirmed, functional consequence of overexpression documented, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"11964389\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"PATJ is targeted to the apical region and tight junctions upon initiation of cell polarization; RNAi-mediated reduction of PATJ delays tight junction formation and causes cell polarity defects, which are reversed by PATJ reintroduction, establishing PATJ as a functional polarity protein in mammalian epithelial cells.\",\n      \"method\": \"RNAi knockdown, rescue by reintroduction, immunofluorescence, tight junction formation assay in MDCK cells\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with defined phenotype plus rescue experiment, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"15738264\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"PATJ knockdown in Caco2 cells causes Pals1 to dissociate from tight junctions, Crumbs3 to accumulate in an early endosome-related compartment near the apical membrane, and mislocalization of occludin and ZO-3 to the lateral membrane, demonstrating that PATJ connects and stabilizes apical and lateral components of tight junctions.\",\n      \"method\": \"Stable shRNA knockdown, immunofluorescence, subcellular fractionation in Caco2 cells\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — stable knockdown with multiple defined molecular readouts, single lab\",\n      \"pmids\": [\"16129888\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The L27 domain of PATJ forms a heterodimeric complex with the L27N domain of Pals1, assembling into a tetrameric structure (two heterodimer units); the C-terminal alpha-helix of each L27 domain is a critical specificity determinant for partner selection.\",\n      \"method\": \"NMR solution structure determination, biochemical binding assays, site-directed analysis of L27 domain complexes\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution NMR structure plus biochemical validation, establishes structural mechanism of PATJ-Pals1 L27 complex assembly\",\n      \"pmids\": [\"15863617\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PATJ is required for directional migration of epithelial cells; PATJ RNAi in MDCKII cells disrupts localization of aPKC and Par3 to the leading edge and disorganizes the microtubule-organizing center orientation during wound-induced migration.\",\n      \"method\": \"RNAi knockdown, wound-induced migration assay, immunofluorescence of aPKC/Par3 at leading edge, MTOC orientation analysis\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean loss-of-function with specific cellular phenotype and molecular readouts (aPKC/Par3 mislocalization, MTOC defect), single lab with multiple orthogonal assays\",\n      \"pmids\": [\"17235357\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"HPV16 and HPV18 E6 proteins bind PATJ through E6's C-terminal PDZ-binding motif and target PATJ for degradation; additionally, the alternatively spliced 18 E6* isoform (lacking a C-terminal PDZ-binding motif) also associates with and degrades PATJ independently, and 18 E6-mediated PATJ degradation is not inhibited by shRNA silencing of E6AP.\",\n      \"method\": \"Co-immunoprecipitation, protein degradation assays, shRNA silencing of E6AP, isoform comparison experiments in epithelial cells\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple binding/degradation assays with isoform dissection and E6AP genetic test, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"17287269\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PATJ (and its paralogue Mupp1) forms a ternary complex with angiomotin (Amot) and the RhoA GEF Syx; this Amot:Patj/Mupp1:Syx complex controls spatial targeting of RhoA activity to lamellipodia in migrating endothelial cells.\",\n      \"method\": \"Peptide pull-down, yeast two-hybrid screening, FRET analysis of RhoA activity in lamellipodia, morpholino knockdown in zebrafish\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ternary complex identified by multiple methods (pull-down, Y2H), RhoA activity measured by FRET, in vivo zebrafish validation; single lab but orthogonal methods\",\n      \"pmids\": [\"18824598\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"CIPP (PATJ/INADL) selectively binds via its PDZ domains to Kir4.1 and Kir4.2 inward rectifier K+ channels, NMDA receptor subunits, neurexins, and neuroligins; co-expression of CIPP with Kir4.1 in COS-7 cells doubles Kir4.1 current density.\",\n      \"method\": \"Yeast two-hybrid, GST pull-down, whole-cell voltage clamp electrophysiology in COS-7 cells\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro binding assays combined with functional electrophysiological readout (current density), single lab with multiple orthogonal methods\",\n      \"pmids\": [\"9647694\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"CIPP (PATJ/INADL) PDZ4 domain interacts with ASIC3 C-terminal region; co-expression of CIPP with ASIC3 in COS cells increases ASIC3 peak current density 5-fold and slightly shifts pH0.5 from 6.2 to 6.4, consistent with enhanced surface expression of ASIC3.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, whole-cell patch-clamp electrophysiology in COS cells, in situ hybridization\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — PDZ domain-substrate interaction mapped and functional consequence (increased current) measured electrophysiologically, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"11872753\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The seven PDZ domains of human INADL (PATJ) each have distinct binding specificities for C-terminal peptide ligands, falling into class I, class II, and a novel class IV (characterized by an acidic residue at the C-terminal position); site-directed mutagenesis of contact residues confirmed involvement of specific pocket residues in binding preference.\",\n      \"method\": \"Combinatorial phage-display peptide library screening, homology modeling, site-directed mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — peptide binding preferences determined experimentally by phage display, confirmed by mutagenesis; single lab with multiple orthogonal methods\",\n      \"pmids\": [\"11509564\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PATJ shares binding partners with MUPP1 including JAM1, ZO-3, Pals1, Par6, and nectins, and uses overlapping mechanisms for tight junction localization; however, unlike MUPP1, PATJ is indispensable for tight junction establishment and epithelial polarization, with Pals1 showing higher affinity for PATJ than MUPP1, and Pals1-mediated activation of the Par6-aPKC complex being critical for PATJ function.\",\n      \"method\": \"Co-immunoprecipitation, binding affinity comparison, RNAi knockdown of PATJ vs MUPP1, immunofluorescence\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — comparative knockdown of paralogs with defined molecular phenotypes, binding affinity measurements, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"19255144\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PATJ physically interacts with nephrocystin-1 (NPHP1) and nephrocystin-4 (NPHP4) and co-localizes with them in human renal tubules; knockdown of NPHP1 or NPHP4 phenocopies loss of PALS1/Par3, producing tight junction formation defects similar to those seen with PATJ/PALS1 depletion.\",\n      \"method\": \"Co-immunoprecipitation, shRNA knockdown in MDCK cells, immunofluorescence, 3D collagen matrix culture\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — physical interaction shown by co-IP and co-localization, but the functional linkage to PATJ is inferred from epistasis/phenotypic similarity rather than direct PATJ epistasis experiment; single lab\",\n      \"pmids\": [\"19755384\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Drosophila PATJ directly binds the Myosin-binding subunit (MBS) of Myosin phosphatase and decreases Myosin dephosphorylation, resulting in activated (phosphorylated) Myosin; this supports stability of the Zonula Adherens, and loss of PATJ leads sequentially to Myosin loss from AJ, AJ disassembly, and loss of apical-basal polarity.\",\n      \"method\": \"Direct binding assay (pull-down), Myosin phosphorylation assays, PATJ mutant analysis in Drosophila epithelium, immunofluorescence\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct binding demonstrated, enzymatic (phosphatase inhibition) mechanism established, in vivo genetic loss-of-function with ordered phenotypic readouts; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"23128243\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"In Drosophila, the first PDZ domain of Patj together with its Stardust-binding (L27) domain are sufficient to fully rescue viability and Crumbs localization in null Patj mutants; Patj null mutants are lethal but Patj is dispensable for ectoderm polarity while being required in follicular epithelium where it supports Crumbs complex apical localization. Gain-of-function of Crumbs and Patj mutation genetically suppress each other in follicular cells.\",\n      \"method\": \"Generation of null Drosophila Patj mutants, domain truncation rescue experiments, genetic epistasis (Crumbs gain-of-function × Patj mutant), immunofluorescence\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — null mutant with domain rescue and genetic epistasis, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"23136386\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Crystal structure of the L27(PATJ)-(L27N,L27C)(Pals1)-L27(MALS2) heterotrimer reveals two cognate pairs of heterodimeric L27 domains that assemble mutually independently; biochemical data confirm this independent assembly mode also applies to DLG1/CASK/Mals2.\",\n      \"method\": \"X-ray crystallography (2.05 Å resolution), biochemical binding assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with biochemical validation, defines molecular mechanism of tripartite complex assembly\",\n      \"pmids\": [\"22337881\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"MUPP-1 levels inversely regulate PATJ protein levels by controlling stability of the PATJ/PALS-1 complex; upon MUPP-1 depletion, increased PATJ localizes at the migrating front and recruits more PAR3, indicating at least two distinct pools of PALS-1 complexes (PALS-1/MUPP-1 and PALS-1/PATJ) co-exist in epithelial cells.\",\n      \"method\": \"siRNA depletion, co-immunoprecipitation, immunofluorescence, western blotting in MCF10A cells\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — knockdown with defined molecular and localization readouts, single lab, single set of experiments\",\n      \"pmids\": [\"23880463\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CIPP (PATJ/INADL) forms a tripartite complex with IRSp53 and Cypin in neuronal cells; CIPP acts as a bridge linking the C-termini of IRSp53 and Cypin via its PDZ domains, and IRSp53 connects to Cypin via an SH3-mediated interaction requiring two positively charged Cypin residues; the three proteins co-localize at the tips of neuronal protrusions.\",\n      \"method\": \"Co-immunoprecipitation in cultured cells, domain mapping with PDZ domains, SH3-domain interaction mutagenesis, co-localization by immunofluorescence in neuronal cells\",\n      \"journal\": \"Biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — complex demonstrated by co-IP, interaction domains mapped by mutagenesis, localization confirmed; single lab\",\n      \"pmids\": [\"20707603\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"CIPP (PATJ/INADL) PDZ2 directly binds IRSp53 C-terminus; co-transfection of CIPP with IRSp53 in mammalian cells induces reorganization of CIPP into large punctate multi-protein assemblies that are not cytoplasmic vesicles.\",\n      \"method\": \"GST pull-down with individual PDZ domains, co-transfection/co-localization, endocytic marker co-staining\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — PDZ domain mapped by pull-down, localization effect documented; single lab, single method per finding\",\n      \"pmids\": [\"19138174\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PATJ knockout in epithelial cells causes tight junction defects, disturbed apical-basal polarity, and impaired lumen formation in 3D cysts; mechanistically, PATJ associates with and inhibits HDAC7, and HDAC7 inhibition/knockdown rescues the polarity and lumen phenotypes; PATJ-mediated regulation of HDAC7 controls expression of genes involved in cell junction assembly and membrane organization; this HDAC7-regulatory function is independent of Pals1 binding.\",\n      \"method\": \"CRISPR-Cas9 knockout, 3D cyst assay, co-immunoprecipitation (PATJ-HDAC7), HDAC7 inhibitor/siRNA rescue, RNA-seq gene expression analysis\",\n      \"journal\": \"Cellular and molecular life sciences : CMLS\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR KO with multiple phenotypic readouts, novel interaction mapped by co-IP, pharmacologic and genetic rescue with orthogonal approaches; single lab\",\n      \"pmids\": [\"37878054\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"In mouse preimplantation embryos, PATJ and MPDZ together are required for blastocyst formation and trophectoderm lineage specification; double depletion disrupts the apical CRB and PAR polarity complexes, tight junctions, and actin filaments in outer cells, leading to ectopic Hippo signaling activation, reduced YAP nuclear localization, suppressed Cdx2 expression, and failure of trophectoderm differentiation.\",\n      \"method\": \"Zygote microinjection of RNAi constructs, immunofluorescence for polarity/junction markers, Hippo pathway readouts (YAP phosphorylation/localization), transcription factor expression analysis\",\n      \"journal\": \"Reproduction (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — loss-of-function in vivo with multiple molecular readouts linking PATJ to polarity complex integrity and Hippo/YAP signaling; single lab, single organism model\",\n      \"pmids\": [\"37318097\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CIPP (PATJ/INADL) interacts via its PDZ domains with the C-terminal PDZ-binding motif of the serotonin 5-HT2B receptor; co-expression of CIPP increases 5-HT2B receptor clustering at neuronal surfaces, prevents receptor dispersion after agonist stimulation, and potentiates inositol phosphate production and calcium mobilization; CIPP, 5-HT2B, and NMDA receptor NR1 subunit form a macromolecular complex.\",\n      \"method\": \"Peptide affinity chromatography/mass spectrometry, co-immunoprecipitation in COS-7 cells, IP measurement, calcium imaging, immunofluorescence in hippocampal neurons\",\n      \"journal\": \"ACS chemical neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ternary complex identified by co-IP, functional consequences measured by IP/calcium assays, localization by immunofluorescence; single lab with multiple orthogonal methods\",\n      \"pmids\": [\"33739808\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PATJ knockout in HEK293 cells alters YAP1 nuclear translocation, and PATJ deletion causes transcriptional reprogramming including dysregulation of vascular/stress-response genes (RUNX1, HEY1, NUPR1, HK2); in C. elegans, the PATJ homolog mpz-1 is upregulated under hypoxia and its knockdown causes abnormal neuronal morphology and increased mortality exacerbated by hypoxia.\",\n      \"method\": \"CRISPR-Cas9 knockout, YAP1 nuclear translocation assay, RNA-seq, C. elegans mpz-1 knockdown/hypoxia experiments\",\n      \"journal\": \"Redox biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — CRISPR KO with defined YAP1 localization readout and transcriptional analysis; C. elegans ortholog loss-of-function; single lab\",\n      \"pmids\": [\"40472775\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PATJ conditional knockout in T cells impairs immunological synapse (IS) formation and T cell activation in vitro and in vivo; PATJ expression increases rapidly upon T cell activation; a specific minimal PDZ domain combination within PATJ is sufficient to support TCR signaling and, when engineered into a CAR construct, enhances CAR-T cell cytotoxicity against solid tumors.\",\n      \"method\": \"Conditional T cell-specific Patj knockout mice, confocal microscopy of IS formation, in vitro/in vivo T cell activation assays, PATJ truncation domain mapping, CAR-T cell cytotoxicity assay\",\n      \"journal\": \"Journal for immunotherapy of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with defined cellular phenotype, domain truncation mapping, functional assays; single lab, multiple orthogonal approaches\",\n      \"pmids\": [\"40341028\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PatJ (PATJ) is required for lumen initiation in MDCK-II cells; PatJ controls the architecture of the apical-lateral border and connects the tight junction to the apical cortex, and its loss impairs fusion of vacuolar apical compartments (VACs) at the apical membrane initiation site (AMIS) to generate a nascent lumen.\",\n      \"method\": \"Quantitative light and electron microscopy, proximity proteomics (BioID), loss-of-function experiments in MDCK-II cells, apical cargo trafficking assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — preprint, loss-of-function with defined ultrastructural and trafficking readouts; single lab\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PATJ zebrafish knockout (via homozygous truncating PATJ variant c.830delC validated in patient and zebrafish model) produces a ciliopathy phenotype including polycystic kidney disease and hydrocephalus, demonstrating an essential role for PATJ in cilia formation and function.\",\n      \"method\": \"Massively parallel sequencing (patient), zebrafish in vivo loss-of-function validation, ciliopathy phenotype characterization\",\n      \"journal\": \"HGG advances\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — human variant identified and validated in zebrafish model with defined ciliopathy phenotype; single lab, single variant\",\n      \"pmids\": [\"40931526\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PATJ is a multi-PDZ domain scaffold protein that localizes to tight junctions and the apical membrane in polarized epithelial cells, where it forms the Crumbs-Pals1-PATJ complex via L27 domain heterodimerization with Pals1; it is required for tight junction formation, apical-basal polarity, directional cell migration, and lumen formation by connecting apical and lateral junction components, stabilizing Crumbs3, regulating aPKC/Par3 localization, and inhibiting HDAC7 to control epithelial gene expression; in neurons it acts as a synaptic scaffold (CIPP) clustering ion channels (Kir4.1, ASIC3) and receptors (NMDA, 5-HT2B) to modulate their surface expression and activity; in endothelial cells it anchors the Amot-Syx complex to spatially control RhoA GTPase activity; and in T cells its PDZ domains support immunological synapse formation and TCR signaling.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PATJ (also INADL/CIPP/hINADL) is a multi-PDZ-domain scaffold protein that organizes apical-basal polarity and tight junctions in epithelial cells by assembling the Crumbs3–Pals1–PATJ complex [#0, #2]. Its N-terminal L27 domain forms a heterodimer with the L27N domain of Pals1, and structural analysis shows these L27 modules build a tetrameric assembly in which cognate L27 pairs dock independently, providing the architectural basis for tripartite scaffold formation with partners such as MALS2 [#3, #14]. Through this scaffold PATJ connects and stabilizes apical and lateral junction components: its loss displaces Pals1 from junctions, traps Crumbs3 in an apical endosomal compartment, and mislocalizes occludin and ZO-3 to the lateral membrane, delaying tight junction formation and disrupting polarity in a manner rescued by re-expression [#1, #2]. PATJ is required for directional epithelial migration, positioning aPKC, Par3 and the MTOC at the leading edge [#4], and for lumen formation in 3D cysts, where it shapes the apical-lateral border and connects the tight junction to the apical cortex [#23]. Beyond scaffolding, PATJ associates with and inhibits HDAC7 to control transcription of cell-junction and membrane-organization genes, a function independent of Pals1 binding [#18]. The seven PDZ domains have distinct C-terminal peptide specificities spanning class I, II, and a novel class IV [#9], underlying a diverse partner repertoire: in neurons (as CIPP) PATJ clusters and increases surface activity of Kir4.1 channels, ASIC3, NMDA receptor subunits, and the 5-HT2B receptor [#7, #8, #20]; in endothelial cells it forms an Amot–PATJ–Syx complex that spatially targets RhoA activity to lamellipodia [#6]; and in T cells it supports immunological synapse formation and TCR signaling [#22]. PATJ is also a target of oncogenic HPV E6 proteins, which bind and degrade it [#5]. A homozygous truncating PATJ variant produces a ciliopathy with polycystic kidney disease and hydrocephalus in patient and zebrafish, establishing an essential role in cilia [#24].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established that the protein (CIPP) is a multi-PDZ scaffold that selectively binds and functionally regulates neuronal ion channels and receptors, defining its earliest molecular identity.\",\n      \"evidence\": \"Yeast two-hybrid, GST pull-down, and whole-cell voltage clamp of Kir4.1/NMDA partners in COS-7 cells\",\n      \"pmids\": [\"9647694\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address epithelial junction roles\", \"No structural basis for partner selection\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Resolved how the seven PDZ domains achieve binding diversity, defining class I, II and a novel class IV specificity and explaining the protein's broad partner repertoire.\",\n      \"evidence\": \"Combinatorial phage-display peptide screening, homology modeling, and site-directed mutagenesis\",\n      \"pmids\": [\"11509564\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Peptide preferences not all matched to physiological partners\", \"No domain occupancy in cells\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Connected PATJ to epithelial apical junctions by showing it binds Crumbs3 and localizes to tight junctions, recasting the neuronal scaffold as a polarity component.\",\n      \"evidence\": \"Co-IP, overexpression/dominant-negative, and immunofluorescence in Caco-2 cells; ASIC3 binding/electrophysiology in COS cells\",\n      \"pmids\": [\"11964389\", \"11872753\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Loss-of-function phenotype not yet tested\", \"Mechanism of junction stabilization unknown\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Demonstrated PATJ is functionally required for tight junction formation and polarity, and defined the structural L27–L27N heterodimer mechanism by which it binds Pals1.\",\n      \"evidence\": \"RNAi with rescue in MDCK/Caco2 cells, subcellular fractionation, and NMR solution structure of the L27 complex\",\n      \"pmids\": [\"15738264\", \"16129888\", \"15863617\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How PATJ stabilizes lateral occludin/ZO-3 mechanistically unresolved\", \"Stoichiometry of full complex in vivo unclear\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Extended PATJ function to directional migration and identified it as a target of oncogenic HPV E6, linking polarity scaffold loss to viral pathogenesis.\",\n      \"evidence\": \"RNAi migration/MTOC assays in MDCKII cells; E6 binding/degradation and E6AP silencing in epithelial cells\",\n      \"pmids\": [\"17235357\", \"17287269\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"E6AP-independent degradation pathway not identified\", \"Direct link between migration defect and tumor phenotype untested\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Showed PATJ spatially controls RhoA signaling by forming an Amot–PATJ–Syx complex in endothelial lamellipodia, generalizing its scaffolding role to GTPase regulation.\",\n      \"evidence\": \"Peptide pull-down, yeast two-hybrid, FRET RhoA biosensor, and zebrafish morpholino knockdown\",\n      \"pmids\": [\"18824598\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Overlap/distinction from Mupp1-containing complexes not fully resolved\", \"Mechanism of RhoA spatial restriction incomplete\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Established direct enzymatic and structural mechanisms: Drosophila PATJ inhibits Myosin phosphatase to maintain junction-stabilizing Myosin activation, and crystallography defined independent L27 pair assembly in the tripartite complex.\",\n      \"evidence\": \"Pull-down/phosphorylation assays and genetic rescue in Drosophila; X-ray crystallography of L27 heterotrimer; domain-rescue and epistasis in Drosophila\",\n      \"pmids\": [\"23128243\", \"22337881\", \"23136386\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether mammalian PATJ regulates Myosin phosphatase similarly untested\", \"Tissue-specific dispensability (ectoderm vs follicle) mechanism unclear\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Distinguished PATJ from its paralog MUPP1, showing shared partners but a non-redundant, indispensable PATJ role tied to higher Pals1 affinity, and linked PATJ to nephrocystins NPHP1/NPHP4.\",\n      \"evidence\": \"Comparative RNAi, affinity comparison, co-IP and 3D culture in epithelial/renal cells\",\n      \"pmids\": [\"19255144\", \"19138174\", \"19755384\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"NPHP linkage inferred from phenotypic similarity rather than direct PATJ epistasis\", \"Functional consequence of PATJ–IRSp53 binding not resolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Revealed reciprocal regulation between PATJ and MUPP1 pools and assembled neuronal CIPP–IRSp53–Cypin tripartite complexes at protrusion tips, expanding the scaffold model.\",\n      \"evidence\": \"siRNA depletion and co-IP in MCF10A cells; domain-mapped co-IP in neuronal cells\",\n      \"pmids\": [\"23880463\", \"20707603\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab, single experimental set for MUPP1/PATJ stability interplay\", \"Physiological role of IRSp53–Cypin–CIPP complex untested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Uncovered a Pals1-independent transcriptional arm: PATJ inhibits HDAC7 to control junction/membrane gene expression and lumen formation, and PATJ/MPDZ govern blastocyst trophectoderm via Hippo/YAP.\",\n      \"evidence\": \"CRISPR KO with 3D cyst assay, PATJ–HDAC7 co-IP, inhibitor/siRNA rescue, RNA-seq; embryo RNAi with polarity and YAP readouts\",\n      \"pmids\": [\"37878054\", \"37318097\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How PATJ inhibits HDAC7 mechanistically unknown\", \"Embryo study limited to single organism and double-depletion design\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Connected PATJ to lumen ultrastructure, T-cell immunological synapse signaling, YAP1-linked stress transcription, and a human ciliopathy, broadening its physiological and disease relevance.\",\n      \"evidence\": \"BioID/EM lumen analysis in MDCK-II (preprint); conditional T-cell KO and CAR engineering; CRISPR KO/RNA-seq and C. elegans hypoxia; patient variant validated in zebrafish\",\n      \"pmids\": [\"40341028\", \"40472775\", \"40931526\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Lumen role rests on a single preprint\", \"Ciliopathy link based on a single variant/family\", \"Mechanism connecting PATJ to ciliogenesis undefined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PATJ's distinct functional modules — Pals1-dependent junction scaffolding, Pals1-independent HDAC7 transcriptional control, RhoA/Myosin cytoskeletal regulation, and neuronal channel clustering — are partitioned and coordinated within a single cell remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No integrated model of how separate PATJ pools/domains are deployed\", \"Mechanism of PATJ's role in ciliogenesis unknown\", \"Direct enzymatic regulation of HDAC7 not characterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [3, 14, 16, 0]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [9, 7]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [12, 18, 7, 8, 20]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005923\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 23]},\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [24]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0045216\", \"supporting_discovery_ids\": [0, 1, 2, 10]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [6, 19, 22]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [4, 19, 13]}\n    ],\n    \"complexes\": [\n      \"Crumbs3-Pals1-PATJ apical polarity complex\",\n      \"Amot-PATJ-Syx complex\",\n      \"L27 PATJ-Pals1-MALS2 heterotrimer\"\n    ],\n    \"partners\": [\n      \"PALS1\",\n      \"CRB3\",\n      \"HDAC7\",\n      \"AMOT\",\n      \"KCNJ10\",\n      \"ASIC3\",\n      \"IRSp53\",\n      \"MPDZ\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}