{"gene":"CLDN5","run_date":"2026-04-28T17:28:52","timeline":{"discoveries":[{"year":1999,"finding":"Claudin-5/TMVCF is an endothelial cell-specific component of tight junction (TJ) strands. When claudin-5 cDNA was introduced into mouse L fibroblasts, TJ strands were reconstituted that resembled those in endothelial cells in vivo (extracellular face-associated TJs), demonstrating that claudin-5 is sufficient to form TJ strands.","method":"Immunofluorescence microscopy, immunoreplica electron microscopy, and reconstitution of TJ strands in transfected mouse L fibroblasts","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 — reconstitution in heterologous cells plus structural visualization by immunoreplica EM; foundational paper with >700 citations","pmids":["10508865"],"is_preprint":false},{"year":2011,"finding":"TNF-α reduces CLDN5 promoter activity and mRNA expression in mouse brain endothelial cells via NFκB signaling; overexpression of the NFκB subunit p65 (RelA) alone is sufficient to repress the Cldn5 promoter, and this regulation requires a conserved promoter region.","method":"Promoter-reporter assays, p65 overexpression, TNF-α treatment of primary brain endothelial cells isolated from C57BL/6 mice","journal":"Cytokine","confidence":"Medium","confidence_rationale":"Tier 2 — multiple functional assays (reporter + protein knockdown) in one lab; single lab but orthogonal methods","pmids":["22138107"],"is_preprint":false},{"year":2012,"finding":"The ETS transcription factor ERG directly regulates CLDN5 gene expression in endothelial cells. ERG knockdown reduces CLDN5 levels and increases endothelial permeability, with increased stress fibers and gap formation, placing ERG upstream of CLDN5 in the barrier-function pathway.","method":"ERG siRNA knockdown in endothelial cells, permeability assays, reporter/ChIP assays identifying CLDN5 as downstream ERG target","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — genetic loss-of-function with defined molecular target and permeability phenotype; single lab","pmids":["22235125"],"is_preprint":false},{"year":2014,"finding":"IL-1β induces downregulation of Cldn5 in brain microvascular endothelial cells (BMECs) via nuclear translocation of β-catenin and FoxO1, and this transcriptional repression is dependent on non-muscle myosin light chain kinase (nmMlck). Primary BMECs from nmMlck-null mice are resistant to IL-1β-induced Cldn5 repression.","method":"Primary BMECs from nmMlck-knockout mice, nuclear fractionation of β-catenin/FoxO1, barrier dysfunction assays, Cldn5 promoter analysis","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — genetic KO cells with multiple orthogonal endpoints (nuclear translocation, gene repression, barrier function); moderate evidence from single lab","pmids":["24522189"],"is_preprint":false},{"year":2020,"finding":"Under hypoxia, CAV1 (caveolin-1) mediates redistribution of membranous CLDN5 into the cytosol in brain microvascular endothelial cells. Autophagy is then activated to degrade cytosolic aggregated CLDN5 and CAV1, thereby alleviating BBB breakdown. Genetic or pharmacological blockage of autophagy aggravates cytosolic CLDN5 aggregation and worsens BBB impairment.","method":"Zebrafish in vivo model, in vitro BMECs, genetic autophagy inhibition, pharmacological autophagy blockade, STED super-resolution microscopy, TEER measurements","journal":"Autophagy","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (in vivo + in vitro, genetic + pharmacological), super-resolution imaging of localization with functional consequence; strong evidence from single study","pmids":["33280500"],"is_preprint":false},{"year":2022,"finding":"A de novo G60R missense mutation in the first extracellular loop of claudin-5 converts the BBB tight junction from a barrier-forming to an anion-selective channel: stable cell lines expressing G60R claudin-5 still form tight junctions but display higher Cl⁻ permeability, lower Na⁺ permeability, and attenuated barrier against small molecules, establishing CLDN5-associated alternating hemiplegia as a channelopathy.","method":"Generation of stably transfected cell lines expressing wild-type or G60R claudin-5, ion permeability assays, protein modelling, sequence alignment","journal":"Brain : a journal of neurology","confidence":"High","confidence_rationale":"Tier 1 — active-site/domain mutagenesis equivalent (patient variant in reconstituted cell lines) with electrophysiological functional validation; single study but rigorous","pmids":["35714222"],"is_preprint":false},{"year":2022,"finding":"CLDN5 in podocytes acts as a regulator of WNT signaling: CLDN5 deletion reduces ZO1 expression and induces nuclear translocation of ZONAB, which transcriptionally downregulates WNT inhibitory factor-1 (WIF1), thereby activating WNT signaling and exacerbating podocyte injury and proteinuria. Podocyte-derived WIF1 also acts in a paracrine manner on tubular epithelial cells.","method":"Podocyte-specific Cldn5 knockout mice, diabetic nephropathy and ureteral obstruction models, nuclear fractionation of ZONAB, ChIP/reporter for WIF1 promoter, systemic WIF1 delivery","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — cell-type-specific KO mice with multiple in vivo phenotypic endpoints and defined molecular pathway; strong evidence","pmids":["35332151"],"is_preprint":false},{"year":2023,"finding":"Blue light exposure causes rapid CLDN5 degradation in retinal endothelial cells via activation of ADAM17 metalloprotease. Under basal conditions ADAM17 is sequestered by the inhibitory G protein GNAZ; blue light disrupts this interaction, freeing ADAM17 to degrade CLDN5. Pharmacological or genetic inhibition of ADAM17 prevents CLDN5 degradation and preserves inner blood-retinal barrier integrity.","method":"Pharmacological ADAM17 inhibition, genetic ADAM17 knockdown, GNAZ knockdown, in vivo mouse blue-light exposure model, TEER/permeability assays, electroretinogram","journal":"Fluids and barriers of the CNS","confidence":"High","confidence_rationale":"Tier 2 — genetic and pharmacological loss-of-function with defined enzymatic mechanism (ADAM17 as writer/eraser of CLDN5 stability) and in vivo validation; multiple orthogonal methods","pmids":["37095509"],"is_preprint":false},{"year":2017,"finding":"The long isoform of human claudin-5 (303 aa, produced by the G allele of rs885985) is retained in intracellular compartments and does not localize to the plasma membrane or intercellular junctions, in contrast to the 218 aa isoform which traffics normally to junctions. Only the 218 aa form is detected in human lung tissue.","method":"Immunoblot of genotyped human lung tissue, forced expression of long vs. short isoforms in transfected cells, immunofluorescence localization","journal":"Annals of the New York Academy of Sciences","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization experiment in transfected cells with functional implication for membrane trafficking; single lab, moderate evidence","pmids":["28445614"],"is_preprint":false},{"year":2024,"finding":"DLL4 (delta like 4) regulates endothelial CLDN5 expression through the NOTCH-NICD-RBPJ-CLDN5 signaling pathway. DLL4 deficiency in mice leads to persistent brain microvasculature abnormalities and increased vascular permeability both in vivo and in vitro, and neonatal hyperoxia reduces both DLL4 and CLDN5 expression in developing mouse brain endothelial cells.","method":"Dll4+/LacZ heterozygous mice, in vitro human brain microvascular endothelial cells, Notch pathway inhibition, vascular permeability assays, in vivo hyperoxia model","journal":"The Journal of physiology","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis (DLL4 deficiency → Notch signaling → CLDN5) with in vivo and in vitro validation; single lab","pmids":["38632887"],"is_preprint":false},{"year":2025,"finding":"In adipocytes, CLDN5 regulates subcellular localization of Y-box protein 3 (YBX3), which directly controls IL10 expression by binding to the IL10 promoter and 3'-UTR. CLDN5 ablation in adipocytes impairs thermogenesis and energy expenditure; this effect is mediated paracrinally through IL10 signaling (via IL10R) on neighboring thermogenic adipocytes.","method":"Adipocyte-specific Cldn5 knockout mice, gene expression profiling, ChIP/reporter assays for YBX3 binding to IL10 promoter, paracrine co-culture experiments, metabolic phenotyping","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — cell-type-specific KO mice with defined molecular pathway (CLDN5→YBX3 localization→IL10→IL10R) and multiple orthogonal in vivo and in vitro methods","pmids":["40610440"],"is_preprint":false},{"year":2026,"finding":"CLDN5 forms a stable complex with β1-integrin in podocytes via its intracellular loop and C-terminal domains, binding the intracellular domain of β1-integrin. This interaction prevents HUWE1-mediated ubiquitination of β1-integrin at lysine K774 and subsequent proteasomal degradation, while also ensuring proper membrane localization of β1-integrin. CLDN5 deletion impairs podocyte adhesion, spreading, and resistance to mechanical stress.","method":"Super-resolution imaging, Co-immunoprecipitation, domain-mapping mutagenesis, ubiquitination assays, Cldn5-KO mice with hypertensive and adriamycin injury models","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — complex identification with domain-level mutagenesis, ubiquitination site mapping, and in vivo KO phenotype; multiple orthogonal methods in single study","pmids":["41539562"],"is_preprint":false},{"year":2025,"finding":"Homocysteine (HCY) suppresses Cldn5 transcription by promoting H3K27me3 enrichment at the Cldn5 promoter. High-intensity interval training (HIIT) reverses this by reducing HCY levels and restoring expression of ETS1, a transcriptional activator of Cldn5, thereby re-establishing BBB integrity and alleviating cognitive impairment.","method":"CUMS and HHCY mouse models, ChIP for H3K27me3 at Cldn5 promoter, RT-qPCR, behavioral testing, metabolic enzyme expression analysis","journal":"Neurobiology of stress","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP demonstrates epigenetic mechanism at Cldn5 promoter with in vivo model; single lab, moderate evidence","pmids":["41035457"],"is_preprint":false},{"year":2025,"finding":"Molecular dynamics simulations of multi-pore claudin-5 complexes (16 protomers, 3 adjacent pores) show that the multi-Pore I structural model recapitulates the anion-selective permeability phenotype of the G60R CLDN5 variant. Free energy calculations reveal that ion passage is hindered by higher barriers in multi-pore than in single-pore architectures.","method":"All-atom molecular dynamics simulation, free energy calculations of water and ion permeation across wild-type and G60R claudin-5 multi-pore models","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 4 — computational/simulation study only, no experimental validation in this paper","pmids":[],"is_preprint":true}],"current_model":"CLDN5 encodes claudin-5, an endothelial cell-enriched tight junction strand protein that forms paracellular barriers at the blood-brain and blood-retinal barriers; its expression is transcriptionally controlled by ERG, NFκB/p65, β-catenin/FoxO1 via nmMlck, ETS1, and Notch-RBPJ signaling, and epigenetically by H3K27me3; membrane stability is regulated by CAV1-mediated internalization (with autophagic clearance of cytosolic aggregates) and by ADAM17-mediated proteolytic degradation (tonically suppressed by GNAZ); in podocytes and adipocytes, CLDN5 acts outside classical tight junctions—stabilizing β1-integrin by blocking HUWE1-mediated ubiquitination at K774, and controlling YBX3 localization to regulate IL10/thermogenesis—while a gain-of-function G60R mutation in the first extracellular loop converts the BBB barrier to an anion-selective channel."},"narrative":{"teleology":[{"year":1999,"claim":"Establishing that claudin-5 is an endothelial-specific tight junction component sufficient to form TJ strands resolved the molecular identity of endothelial paracellular barriers.","evidence":"Reconstitution of TJ strands in transfected mouse L fibroblasts with immunoreplica EM verification","pmids":["10508865"],"confidence":"High","gaps":["Homotypic vs. heterotypic interactions with other claudins not resolved","Ion selectivity of claudin-5 strands not characterized"]},{"year":2011,"claim":"Demonstrating that NF-κB/p65 directly represses the CLDN5 promoter under TNF-α stimulation established a transcriptional mechanism for inflammation-induced BBB breakdown.","evidence":"Promoter-reporter assays and p65 overexpression in primary mouse brain endothelial cells","pmids":["22138107"],"confidence":"Medium","gaps":["Specific NF-κB binding site on CLDN5 promoter not mapped at nucleotide resolution","In vivo relevance in neuroinflammation models not shown"]},{"year":2012,"claim":"Identifying ERG as a direct transcriptional activator of CLDN5 linked an endothelial-enriched ETS factor to barrier maintenance, explaining how constitutive CLDN5 expression is sustained.","evidence":"ERG siRNA knockdown, ChIP, and permeability assays in endothelial cells","pmids":["22235125"],"confidence":"Medium","gaps":["Relative contribution of ERG versus other ETS factors (e.g., ETS1) not delineated","Whether ERG regulation is specific to particular vascular beds unknown"]},{"year":2014,"claim":"Showing that IL-1β-driven CLDN5 repression requires nmMlck-dependent nuclear translocation of β-catenin/FoxO1 revealed a cytoskeletal signaling relay converging on CLDN5 transcription.","evidence":"Primary BMECs from nmMlck-knockout mice with nuclear fractionation and barrier function assays","pmids":["24522189"],"confidence":"High","gaps":["Whether β-catenin and FoxO1 bind CLDN5 promoter directly or act through intermediary factors not fully resolved","Relevance to non-brain endothelial beds not tested"]},{"year":2017,"claim":"Demonstrating that a long claudin-5 isoform (303 aa) is retained intracellularly while the canonical 218 aa isoform traffics to junctions revealed isoform-specific membrane targeting as a layer of CLDN5 regulation.","evidence":"Forced expression of long vs. short isoforms in transfected cells with immunofluorescence; genotyped human lung tissue immunoblots","pmids":["28445614"],"confidence":"Medium","gaps":["Physiological relevance of the long isoform in vivo unclear","Mechanism of intracellular retention not defined"]},{"year":2020,"claim":"Identifying CAV1-mediated internalization of CLDN5 under hypoxia, followed by autophagic clearance of cytosolic aggregates, established a post-translational degradation route that modulates BBB integrity.","evidence":"Zebrafish in vivo model, BMECs in vitro, genetic and pharmacological autophagy inhibition, STED super-resolution microscopy, TEER","pmids":["33280500"],"confidence":"High","gaps":["Signals triggering CAV1-CLDN5 interaction under hypoxia not identified","Whether this pathway operates in non-CNS endothelia unknown"]},{"year":2022,"claim":"Characterizing the G60R mutation as converting claudin-5 from a barrier to an anion-selective channel established the first CLDN5 channelopathy (alternating hemiplegia), resolving the pore properties of claudin-5's first extracellular loop.","evidence":"Stable cell lines expressing WT or G60R claudin-5 with ion permeability assays and protein modeling","pmids":["35714222"],"confidence":"High","gaps":["Structural basis of anion selectivity at atomic resolution not determined experimentally","Whether other ECL1 mutations cause similar channel conversion unknown"]},{"year":2022,"claim":"Showing that CLDN5 deletion in podocytes activates WNT signaling via ZONAB-dependent transcriptional repression of WIF1 revealed a non-canonical, non-TJ role for CLDN5 in kidney epithelial signaling.","evidence":"Podocyte-specific Cldn5 KO mice, diabetic nephropathy and UUO models, ChIP/reporter for ZONAB-WIF1 promoter","pmids":["35332151"],"confidence":"High","gaps":["How CLDN5 controls ZO1 levels in podocytes mechanistically not defined","Whether this WNT-regulatory function extends to other non-endothelial cell types unclear"]},{"year":2023,"claim":"Identifying ADAM17 as the protease that degrades CLDN5 upon release from GNAZ inhibition explained how blue light and similar stimuli rapidly breach the inner blood-retinal barrier.","evidence":"Genetic ADAM17 and GNAZ knockdown, pharmacological ADAM17 inhibition, in vivo mouse blue-light model with TEER and electroretinogram","pmids":["37095509"],"confidence":"High","gaps":["Specific cleavage site on CLDN5 by ADAM17 not mapped","Whether ADAM17-mediated CLDN5 degradation occurs at the BBB or other vascular beds not tested"]},{"year":2024,"claim":"Placing DLL4/Notch-RBPJ signaling upstream of CLDN5 transcription linked developmental vascular patterning cues to BBB formation.","evidence":"Dll4+/LacZ heterozygous mice, human brain microvascular endothelial cells, Notch pathway inhibition, hyperoxia model","pmids":["38632887"],"confidence":"Medium","gaps":["Whether RBPJ binds CLDN5 promoter directly or through intermediary targets not confirmed by ChIP","Interaction with ERG and other CLDN5 transcriptional regulators not integrated"]},{"year":2025,"claim":"Demonstrating H3K27me3 enrichment at the CLDN5 promoter under hyperhomocysteinemia and restoration by ETS1 introduced epigenetic regulation as a mechanism for chronic CLDN5 silencing.","evidence":"ChIP for H3K27me3 at Cldn5 promoter in CUMS and HHCY mouse models with behavioral testing","pmids":["41035457"],"confidence":"Medium","gaps":["Identity of the methyltransferase responsible for H3K27me3 deposition at CLDN5 not determined","Whether ETS1 acts by displacing PRC2 or independently not resolved"]},{"year":2025,"claim":"Revealing that CLDN5 in adipocytes controls YBX3 subcellular localization to regulate IL-10 expression and paracrine thermogenic signaling uncovered a metabolic function entirely independent of tight junction barrier formation.","evidence":"Adipocyte-specific Cldn5 KO mice, ChIP/reporter for YBX3 at IL10 promoter, paracrine co-culture, metabolic phenotyping","pmids":["40610440"],"confidence":"High","gaps":["Mechanism by which CLDN5 controls YBX3 subcellular distribution not elucidated","Whether CLDN5 forms junctional structures in adipocytes or acts as a monomer unknown"]},{"year":2025,"claim":"Identifying CLDN5 as a stabilizer of β1-integrin by blocking HUWE1-mediated ubiquitination at K774 in podocytes established a direct protein-protein protective mechanism outside classical TJ function.","evidence":"Co-IP, domain-mapping mutagenesis, ubiquitination assays, Cldn5-KO mice with hypertensive and adriamycin injury models, super-resolution imaging","pmids":["41539562"],"confidence":"High","gaps":["Whether CLDN5 inhibits HUWE1 by steric occlusion or allosteric mechanism not distinguished","Relevance of the CLDN5-β1-integrin axis in endothelial cells not tested"]},{"year":null,"claim":"How CLDN5's non-junctional functions in podocytes and adipocytes are coordinated with its canonical tight junction role, and what structural features allow CLDN5 to moonlight as a signaling scaffold, remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution experimental structure of claudin-5 homo- or heterotypic pores","Mechanism by which CLDN5 integrates with non-junctional signaling partners (YBX3, β1-integrin) not structurally defined","Comprehensive in vivo characterization across vascular beds lacking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,5]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[6,11]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,8]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[4,8]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,3,6,9]},{"term_id":"R-HSA-1500931","term_label":"Cell-Cell communication","supporting_discovery_ids":[0,5]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[4,11]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[5]}],"complexes":[],"partners":["CAV1","ADAM17","GNAZ","ITGB1","HUWE1","YBX3","ERG","RBPJ"],"other_free_text":[]},"mechanistic_narrative":"CLDN5 encodes claudin-5, an endothelial tight junction strand protein that is sufficient to reconstitute tight junction strands and forms the principal paracellular barrier at the blood-brain and blood-retinal barriers [PMID:10508865]. Its transcription is positively regulated by ERG, ETS1, and DLL4/Notch-RBPJ signaling and repressed by NF-κB/p65, β-catenin/FoxO1 (via nmMlck), and H3K27me3 enrichment at its promoter [PMID:22138107, PMID:22235125, PMID:24522189, PMID:38632887, PMID:41035457]; at the protein level, membrane-localized CLDN5 is internalized by CAV1 under hypoxia (with autophagic clearance of cytosolic aggregates) and degraded by ADAM17 when its tonic inhibitor GNAZ is released [PMID:33280500, PMID:37095509]. Beyond classical tight junctions, CLDN5 stabilizes β1-integrin in podocytes by blocking HUWE1-mediated ubiquitination at K774 and controls YBX3 localization in adipocytes to regulate IL-10-dependent thermogenesis, while a de novo G60R mutation in its first extracellular loop converts the BBB barrier to an anion-selective channel, establishing CLDN5-associated alternating hemiplegia as a channelopathy [PMID:41539562, PMID:40610440, PMID:35714222]."},"prefetch_data":{"uniprot":{"accession":"O00501","full_name":"Claudin-5","aliases":["Transmembrane protein deleted in VCFS","TMDVCF"],"length_aa":218,"mass_kda":23.1,"function":"Plays a major role in tight junction-specific obliteration of the intercellular space","subcellular_location":"Cell junction, tight junction; Cell membrane","url":"https://www.uniprot.org/uniprotkb/O00501/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CLDN5","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CLDN5","total_profiled":1310},"omim":[{"mim_id":"621447","title":"ZINC FINGER PROTEIN 787; ZNF787","url":"https://www.omim.org/entry/621447"},{"mim_id":"609131","title":"CLAUDIN 7; CLDN7","url":"https://www.omim.org/entry/609131"},{"mim_id":"603718","title":"CLAUDIN 1; CLDN1","url":"https://www.omim.org/entry/603718"},{"mim_id":"602910","title":"CLAUDIN 3; CLDN3","url":"https://www.omim.org/entry/602910"},{"mim_id":"602909","title":"CLAUDIN 4; CLDN4","url":"https://www.omim.org/entry/602909"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"adipose tissue","ntpm":424.4},{"tissue":"breast","ntpm":412.2},{"tissue":"choroid plexus","ntpm":406.9},{"tissue":"lung","ntpm":384.3}],"url":"https://www.proteinatlas.org/search/CLDN5"},"hgnc":{"alias_symbol":["CPETRL1","BEC1"],"prev_symbol":["AWAL","TMVCF"]},"alphafold":{"accession":"O00501","domains":[{"cath_id":"1.20.140.150","chopping":"2-28_75-154_162-191","consensus_level":"high","plddt":90.7592,"start":2,"end":191}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O00501","model_url":"https://alphafold.ebi.ac.uk/files/AF-O00501-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O00501-F1-predicted_aligned_error_v6.png","plddt_mean":83.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CLDN5","jax_strain_url":"https://www.jax.org/strain/search?query=CLDN5"},"sequence":{"accession":"O00501","fasta_url":"https://rest.uniprot.org/uniprotkb/O00501.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O00501/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O00501"}},"corpus_meta":[{"pmid":"10508865","id":"PMC_10508865","title":"Endothelial claudin: claudin-5/TMVCF constitutes tight junction strands in endothelial cells.","date":"1999","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/10508865","citation_count":707,"is_preprint":false},{"pmid":"16111945","id":"PMC_16111945","title":"Inactivation of the autophagy gene bec-1 triggers apoptotic cell death in C. elegans.","date":"2005","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/16111945","citation_count":196,"is_preprint":false},{"pmid":"33280500","id":"PMC_33280500","title":"Autophagy alleviates hypoxia-induced blood-brain barrier injury via regulation of CLDN5 (claudin 5).","date":"2020","source":"Autophagy","url":"https://pubmed.ncbi.nlm.nih.gov/33280500","citation_count":145,"is_preprint":false},{"pmid":"22138107","id":"PMC_22138107","title":"TNF-alpha induced NFκB signaling and p65 (RelA) overexpression repress Cldn5 promoter in mouse brain endothelial 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When claudin-5 cDNA was introduced into mouse L fibroblasts, TJ strands were reconstituted that resembled those in endothelial cells in vivo (extracellular face-associated TJs), demonstrating that claudin-5 is sufficient to form TJ strands.\",\n      \"method\": \"Immunofluorescence microscopy, immunoreplica electron microscopy, and reconstitution of TJ strands in transfected mouse L fibroblasts\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution in heterologous cells plus structural visualization by immunoreplica EM; foundational paper with >700 citations\",\n      \"pmids\": [\"10508865\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"TNF-α reduces CLDN5 promoter activity and mRNA expression in mouse brain endothelial cells via NFκB signaling; overexpression of the NFκB subunit p65 (RelA) alone is sufficient to repress the Cldn5 promoter, and this regulation requires a conserved promoter region.\",\n      \"method\": \"Promoter-reporter assays, p65 overexpression, TNF-α treatment of primary brain endothelial cells isolated from C57BL/6 mice\",\n      \"journal\": \"Cytokine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple functional assays (reporter + protein knockdown) in one lab; single lab but orthogonal methods\",\n      \"pmids\": [\"22138107\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The ETS transcription factor ERG directly regulates CLDN5 gene expression in endothelial cells. ERG knockdown reduces CLDN5 levels and increases endothelial permeability, with increased stress fibers and gap formation, placing ERG upstream of CLDN5 in the barrier-function pathway.\",\n      \"method\": \"ERG siRNA knockdown in endothelial cells, permeability assays, reporter/ChIP assays identifying CLDN5 as downstream ERG target\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic loss-of-function with defined molecular target and permeability phenotype; single lab\",\n      \"pmids\": [\"22235125\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"IL-1β induces downregulation of Cldn5 in brain microvascular endothelial cells (BMECs) via nuclear translocation of β-catenin and FoxO1, and this transcriptional repression is dependent on non-muscle myosin light chain kinase (nmMlck). Primary BMECs from nmMlck-null mice are resistant to IL-1β-induced Cldn5 repression.\",\n      \"method\": \"Primary BMECs from nmMlck-knockout mice, nuclear fractionation of β-catenin/FoxO1, barrier dysfunction assays, Cldn5 promoter analysis\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO cells with multiple orthogonal endpoints (nuclear translocation, gene repression, barrier function); moderate evidence from single lab\",\n      \"pmids\": [\"24522189\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Under hypoxia, CAV1 (caveolin-1) mediates redistribution of membranous CLDN5 into the cytosol in brain microvascular endothelial cells. Autophagy is then activated to degrade cytosolic aggregated CLDN5 and CAV1, thereby alleviating BBB breakdown. Genetic or pharmacological blockage of autophagy aggravates cytosolic CLDN5 aggregation and worsens BBB impairment.\",\n      \"method\": \"Zebrafish in vivo model, in vitro BMECs, genetic autophagy inhibition, pharmacological autophagy blockade, STED super-resolution microscopy, TEER measurements\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (in vivo + in vitro, genetic + pharmacological), super-resolution imaging of localization with functional consequence; strong evidence from single study\",\n      \"pmids\": [\"33280500\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"A de novo G60R missense mutation in the first extracellular loop of claudin-5 converts the BBB tight junction from a barrier-forming to an anion-selective channel: stable cell lines expressing G60R claudin-5 still form tight junctions but display higher Cl⁻ permeability, lower Na⁺ permeability, and attenuated barrier against small molecules, establishing CLDN5-associated alternating hemiplegia as a channelopathy.\",\n      \"method\": \"Generation of stably transfected cell lines expressing wild-type or G60R claudin-5, ion permeability assays, protein modelling, sequence alignment\",\n      \"journal\": \"Brain : a journal of neurology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — active-site/domain mutagenesis equivalent (patient variant in reconstituted cell lines) with electrophysiological functional validation; single study but rigorous\",\n      \"pmids\": [\"35714222\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CLDN5 in podocytes acts as a regulator of WNT signaling: CLDN5 deletion reduces ZO1 expression and induces nuclear translocation of ZONAB, which transcriptionally downregulates WNT inhibitory factor-1 (WIF1), thereby activating WNT signaling and exacerbating podocyte injury and proteinuria. Podocyte-derived WIF1 also acts in a paracrine manner on tubular epithelial cells.\",\n      \"method\": \"Podocyte-specific Cldn5 knockout mice, diabetic nephropathy and ureteral obstruction models, nuclear fractionation of ZONAB, ChIP/reporter for WIF1 promoter, systemic WIF1 delivery\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific KO mice with multiple in vivo phenotypic endpoints and defined molecular pathway; strong evidence\",\n      \"pmids\": [\"35332151\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Blue light exposure causes rapid CLDN5 degradation in retinal endothelial cells via activation of ADAM17 metalloprotease. Under basal conditions ADAM17 is sequestered by the inhibitory G protein GNAZ; blue light disrupts this interaction, freeing ADAM17 to degrade CLDN5. Pharmacological or genetic inhibition of ADAM17 prevents CLDN5 degradation and preserves inner blood-retinal barrier integrity.\",\n      \"method\": \"Pharmacological ADAM17 inhibition, genetic ADAM17 knockdown, GNAZ knockdown, in vivo mouse blue-light exposure model, TEER/permeability assays, electroretinogram\",\n      \"journal\": \"Fluids and barriers of the CNS\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic and pharmacological loss-of-function with defined enzymatic mechanism (ADAM17 as writer/eraser of CLDN5 stability) and in vivo validation; multiple orthogonal methods\",\n      \"pmids\": [\"37095509\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"The long isoform of human claudin-5 (303 aa, produced by the G allele of rs885985) is retained in intracellular compartments and does not localize to the plasma membrane or intercellular junctions, in contrast to the 218 aa isoform which traffics normally to junctions. Only the 218 aa form is detected in human lung tissue.\",\n      \"method\": \"Immunoblot of genotyped human lung tissue, forced expression of long vs. short isoforms in transfected cells, immunofluorescence localization\",\n      \"journal\": \"Annals of the New York Academy of Sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization experiment in transfected cells with functional implication for membrane trafficking; single lab, moderate evidence\",\n      \"pmids\": [\"28445614\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"DLL4 (delta like 4) regulates endothelial CLDN5 expression through the NOTCH-NICD-RBPJ-CLDN5 signaling pathway. DLL4 deficiency in mice leads to persistent brain microvasculature abnormalities and increased vascular permeability both in vivo and in vitro, and neonatal hyperoxia reduces both DLL4 and CLDN5 expression in developing mouse brain endothelial cells.\",\n      \"method\": \"Dll4+/LacZ heterozygous mice, in vitro human brain microvascular endothelial cells, Notch pathway inhibition, vascular permeability assays, in vivo hyperoxia model\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis (DLL4 deficiency → Notch signaling → CLDN5) with in vivo and in vitro validation; single lab\",\n      \"pmids\": [\"38632887\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In adipocytes, CLDN5 regulates subcellular localization of Y-box protein 3 (YBX3), which directly controls IL10 expression by binding to the IL10 promoter and 3'-UTR. CLDN5 ablation in adipocytes impairs thermogenesis and energy expenditure; this effect is mediated paracrinally through IL10 signaling (via IL10R) on neighboring thermogenic adipocytes.\",\n      \"method\": \"Adipocyte-specific Cldn5 knockout mice, gene expression profiling, ChIP/reporter assays for YBX3 binding to IL10 promoter, paracrine co-culture experiments, metabolic phenotyping\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific KO mice with defined molecular pathway (CLDN5→YBX3 localization→IL10→IL10R) and multiple orthogonal in vivo and in vitro methods\",\n      \"pmids\": [\"40610440\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"CLDN5 forms a stable complex with β1-integrin in podocytes via its intracellular loop and C-terminal domains, binding the intracellular domain of β1-integrin. This interaction prevents HUWE1-mediated ubiquitination of β1-integrin at lysine K774 and subsequent proteasomal degradation, while also ensuring proper membrane localization of β1-integrin. CLDN5 deletion impairs podocyte adhesion, spreading, and resistance to mechanical stress.\",\n      \"method\": \"Super-resolution imaging, Co-immunoprecipitation, domain-mapping mutagenesis, ubiquitination assays, Cldn5-KO mice with hypertensive and adriamycin injury models\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — complex identification with domain-level mutagenesis, ubiquitination site mapping, and in vivo KO phenotype; multiple orthogonal methods in single study\",\n      \"pmids\": [\"41539562\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Homocysteine (HCY) suppresses Cldn5 transcription by promoting H3K27me3 enrichment at the Cldn5 promoter. High-intensity interval training (HIIT) reverses this by reducing HCY levels and restoring expression of ETS1, a transcriptional activator of Cldn5, thereby re-establishing BBB integrity and alleviating cognitive impairment.\",\n      \"method\": \"CUMS and HHCY mouse models, ChIP for H3K27me3 at Cldn5 promoter, RT-qPCR, behavioral testing, metabolic enzyme expression analysis\",\n      \"journal\": \"Neurobiology of stress\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP demonstrates epigenetic mechanism at Cldn5 promoter with in vivo model; single lab, moderate evidence\",\n      \"pmids\": [\"41035457\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Molecular dynamics simulations of multi-pore claudin-5 complexes (16 protomers, 3 adjacent pores) show that the multi-Pore I structural model recapitulates the anion-selective permeability phenotype of the G60R CLDN5 variant. Free energy calculations reveal that ion passage is hindered by higher barriers in multi-pore than in single-pore architectures.\",\n      \"method\": \"All-atom molecular dynamics simulation, free energy calculations of water and ion permeation across wild-type and G60R claudin-5 multi-pore models\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 — computational/simulation study only, no experimental validation in this paper\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"CLDN5 encodes claudin-5, an endothelial cell-enriched tight junction strand protein that forms paracellular barriers at the blood-brain and blood-retinal barriers; its expression is transcriptionally controlled by ERG, NFκB/p65, β-catenin/FoxO1 via nmMlck, ETS1, and Notch-RBPJ signaling, and epigenetically by H3K27me3; membrane stability is regulated by CAV1-mediated internalization (with autophagic clearance of cytosolic aggregates) and by ADAM17-mediated proteolytic degradation (tonically suppressed by GNAZ); in podocytes and adipocytes, CLDN5 acts outside classical tight junctions—stabilizing β1-integrin by blocking HUWE1-mediated ubiquitination at K774, and controlling YBX3 localization to regulate IL10/thermogenesis—while a gain-of-function G60R mutation in the first extracellular loop converts the BBB barrier to an anion-selective channel.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CLDN5 encodes claudin-5, an endothelial tight junction strand protein that is sufficient to reconstitute tight junction strands and forms the principal paracellular barrier at the blood-brain and blood-retinal barriers [PMID:10508865]. Its transcription is positively regulated by ERG, ETS1, and DLL4/Notch-RBPJ signaling and repressed by NF-κB/p65, β-catenin/FoxO1 (via nmMlck), and H3K27me3 enrichment at its promoter [PMID:22138107, PMID:22235125, PMID:24522189, PMID:38632887, PMID:41035457]; at the protein level, membrane-localized CLDN5 is internalized by CAV1 under hypoxia (with autophagic clearance of cytosolic aggregates) and degraded by ADAM17 when its tonic inhibitor GNAZ is released [PMID:33280500, PMID:37095509]. Beyond classical tight junctions, CLDN5 stabilizes β1-integrin in podocytes by blocking HUWE1-mediated ubiquitination at K774 and controls YBX3 localization in adipocytes to regulate IL-10-dependent thermogenesis, while a de novo G60R mutation in its first extracellular loop converts the BBB barrier to an anion-selective channel, establishing CLDN5-associated alternating hemiplegia as a channelopathy [PMID:41539562, PMID:40610440, PMID:35714222].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Establishing that claudin-5 is an endothelial-specific tight junction component sufficient to form TJ strands resolved the molecular identity of endothelial paracellular barriers.\",\n      \"evidence\": \"Reconstitution of TJ strands in transfected mouse L fibroblasts with immunoreplica EM verification\",\n      \"pmids\": [\"10508865\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Homotypic vs. heterotypic interactions with other claudins not resolved\", \"Ion selectivity of claudin-5 strands not characterized\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Demonstrating that NF-κB/p65 directly represses the CLDN5 promoter under TNF-α stimulation established a transcriptional mechanism for inflammation-induced BBB breakdown.\",\n      \"evidence\": \"Promoter-reporter assays and p65 overexpression in primary mouse brain endothelial cells\",\n      \"pmids\": [\"22138107\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific NF-κB binding site on CLDN5 promoter not mapped at nucleotide resolution\", \"In vivo relevance in neuroinflammation models not shown\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identifying ERG as a direct transcriptional activator of CLDN5 linked an endothelial-enriched ETS factor to barrier maintenance, explaining how constitutive CLDN5 expression is sustained.\",\n      \"evidence\": \"ERG siRNA knockdown, ChIP, and permeability assays in endothelial cells\",\n      \"pmids\": [\"22235125\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relative contribution of ERG versus other ETS factors (e.g., ETS1) not delineated\", \"Whether ERG regulation is specific to particular vascular beds unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showing that IL-1β-driven CLDN5 repression requires nmMlck-dependent nuclear translocation of β-catenin/FoxO1 revealed a cytoskeletal signaling relay converging on CLDN5 transcription.\",\n      \"evidence\": \"Primary BMECs from nmMlck-knockout mice with nuclear fractionation and barrier function assays\",\n      \"pmids\": [\"24522189\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether β-catenin and FoxO1 bind CLDN5 promoter directly or act through intermediary factors not fully resolved\", \"Relevance to non-brain endothelial beds not tested\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstrating that a long claudin-5 isoform (303 aa) is retained intracellularly while the canonical 218 aa isoform traffics to junctions revealed isoform-specific membrane targeting as a layer of CLDN5 regulation.\",\n      \"evidence\": \"Forced expression of long vs. short isoforms in transfected cells with immunofluorescence; genotyped human lung tissue immunoblots\",\n      \"pmids\": [\"28445614\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological relevance of the long isoform in vivo unclear\", \"Mechanism of intracellular retention not defined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identifying CAV1-mediated internalization of CLDN5 under hypoxia, followed by autophagic clearance of cytosolic aggregates, established a post-translational degradation route that modulates BBB integrity.\",\n      \"evidence\": \"Zebrafish in vivo model, BMECs in vitro, genetic and pharmacological autophagy inhibition, STED super-resolution microscopy, TEER\",\n      \"pmids\": [\"33280500\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signals triggering CAV1-CLDN5 interaction under hypoxia not identified\", \"Whether this pathway operates in non-CNS endothelia unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Characterizing the G60R mutation as converting claudin-5 from a barrier to an anion-selective channel established the first CLDN5 channelopathy (alternating hemiplegia), resolving the pore properties of claudin-5's first extracellular loop.\",\n      \"evidence\": \"Stable cell lines expressing WT or G60R claudin-5 with ion permeability assays and protein modeling\",\n      \"pmids\": [\"35714222\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of anion selectivity at atomic resolution not determined experimentally\", \"Whether other ECL1 mutations cause similar channel conversion unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Showing that CLDN5 deletion in podocytes activates WNT signaling via ZONAB-dependent transcriptional repression of WIF1 revealed a non-canonical, non-TJ role for CLDN5 in kidney epithelial signaling.\",\n      \"evidence\": \"Podocyte-specific Cldn5 KO mice, diabetic nephropathy and UUO models, ChIP/reporter for ZONAB-WIF1 promoter\",\n      \"pmids\": [\"35332151\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How CLDN5 controls ZO1 levels in podocytes mechanistically not defined\", \"Whether this WNT-regulatory function extends to other non-endothelial cell types unclear\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identifying ADAM17 as the protease that degrades CLDN5 upon release from GNAZ inhibition explained how blue light and similar stimuli rapidly breach the inner blood-retinal barrier.\",\n      \"evidence\": \"Genetic ADAM17 and GNAZ knockdown, pharmacological ADAM17 inhibition, in vivo mouse blue-light model with TEER and electroretinogram\",\n      \"pmids\": [\"37095509\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific cleavage site on CLDN5 by ADAM17 not mapped\", \"Whether ADAM17-mediated CLDN5 degradation occurs at the BBB or other vascular beds not tested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Placing DLL4/Notch-RBPJ signaling upstream of CLDN5 transcription linked developmental vascular patterning cues to BBB formation.\",\n      \"evidence\": \"Dll4+/LacZ heterozygous mice, human brain microvascular endothelial cells, Notch pathway inhibition, hyperoxia model\",\n      \"pmids\": [\"38632887\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether RBPJ binds CLDN5 promoter directly or through intermediary targets not confirmed by ChIP\", \"Interaction with ERG and other CLDN5 transcriptional regulators not integrated\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Demonstrating H3K27me3 enrichment at the CLDN5 promoter under hyperhomocysteinemia and restoration by ETS1 introduced epigenetic regulation as a mechanism for chronic CLDN5 silencing.\",\n      \"evidence\": \"ChIP for H3K27me3 at Cldn5 promoter in CUMS and HHCY mouse models with behavioral testing\",\n      \"pmids\": [\"41035457\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Identity of the methyltransferase responsible for H3K27me3 deposition at CLDN5 not determined\", \"Whether ETS1 acts by displacing PRC2 or independently not resolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revealing that CLDN5 in adipocytes controls YBX3 subcellular localization to regulate IL-10 expression and paracrine thermogenic signaling uncovered a metabolic function entirely independent of tight junction barrier formation.\",\n      \"evidence\": \"Adipocyte-specific Cldn5 KO mice, ChIP/reporter for YBX3 at IL10 promoter, paracrine co-culture, metabolic phenotyping\",\n      \"pmids\": [\"40610440\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which CLDN5 controls YBX3 subcellular distribution not elucidated\", \"Whether CLDN5 forms junctional structures in adipocytes or acts as a monomer unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identifying CLDN5 as a stabilizer of β1-integrin by blocking HUWE1-mediated ubiquitination at K774 in podocytes established a direct protein-protein protective mechanism outside classical TJ function.\",\n      \"evidence\": \"Co-IP, domain-mapping mutagenesis, ubiquitination assays, Cldn5-KO mice with hypertensive and adriamycin injury models, super-resolution imaging\",\n      \"pmids\": [\"41539562\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CLDN5 inhibits HUWE1 by steric occlusion or allosteric mechanism not distinguished\", \"Relevance of the CLDN5-β1-integrin axis in endothelial cells not tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How CLDN5's non-junctional functions in podocytes and adipocytes are coordinated with its canonical tight junction role, and what structural features allow CLDN5 to moonlight as a signaling scaffold, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No high-resolution experimental structure of claudin-5 homo- or heterotypic pores\", \"Mechanism by which CLDN5 integrates with non-junctional signaling partners (YBX3, β1-integrin) not structurally defined\", \"Comprehensive in vivo characterization across vascular beds lacking\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [6, 11]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 8]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [4, 8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 3, 6, 9]},\n      {\"term_id\": \"R-HSA-1500931\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [4, 11]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"CAV1\",\n      \"ADAM17\",\n      \"GNAZ\",\n      \"ITGB1\",\n      \"HUWE1\",\n      \"YBX3\",\n      \"ERG\",\n      \"RBPJ\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}