Affinage

CLDN5

Claudin-5 · UniProt O00501

Length
218 aa
Mass
23.1 kDa
Annotated
2026-04-28
37 papers in source corpus 13 papers cited in narrative 14 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

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).

Mechanistic history

Synthesis pass · year-by-year structured walk · 13 steps
  1. 1999 High

    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

    PMID:10508865

    Open questions at the time
    • Homotypic vs. heterotypic interactions with other claudins not resolved
    • Ion selectivity of claudin-5 strands not characterized
  2. 2011 Medium

    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

    PMID:22138107

    Open questions at the time
    • Specific NF-κB binding site on CLDN5 promoter not mapped at nucleotide resolution
    • In vivo relevance in neuroinflammation models not shown
  3. 2012 Medium

    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

    PMID:22235125

    Open questions at the time
    • Relative contribution of ERG versus other ETS factors (e.g., ETS1) not delineated
    • Whether ERG regulation is specific to particular vascular beds unknown
  4. 2014 High

    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

    PMID:24522189

    Open questions at the time
    • 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
  5. 2017 Medium

    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

    PMID:28445614

    Open questions at the time
    • Physiological relevance of the long isoform in vivo unclear
    • Mechanism of intracellular retention not defined
  6. 2020 High

    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

    PMID:33280500

    Open questions at the time
    • Signals triggering CAV1-CLDN5 interaction under hypoxia not identified
    • Whether this pathway operates in non-CNS endothelia unknown
  7. 2022 High

    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

    PMID:35714222

    Open questions at the time
    • Structural basis of anion selectivity at atomic resolution not determined experimentally
    • Whether other ECL1 mutations cause similar channel conversion unknown
  8. 2022 High

    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

    PMID:35332151

    Open questions at the time
    • How CLDN5 controls ZO1 levels in podocytes mechanistically not defined
    • Whether this WNT-regulatory function extends to other non-endothelial cell types unclear
  9. 2023 High

    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

    PMID:37095509

    Open questions at the time
    • Specific cleavage site on CLDN5 by ADAM17 not mapped
    • Whether ADAM17-mediated CLDN5 degradation occurs at the BBB or other vascular beds not tested
  10. 2024 Medium

    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

    PMID:38632887

    Open questions at the time
    • Whether RBPJ binds CLDN5 promoter directly or through intermediary targets not confirmed by ChIP
    • Interaction with ERG and other CLDN5 transcriptional regulators not integrated
  11. 2025 Medium

    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

    PMID:41035457

    Open questions at the time
    • Identity of the methyltransferase responsible for H3K27me3 deposition at CLDN5 not determined
    • Whether ETS1 acts by displacing PRC2 or independently not resolved
  12. 2025 High

    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

    PMID:40610440

    Open questions at the time
    • Mechanism by which CLDN5 controls YBX3 subcellular distribution not elucidated
    • Whether CLDN5 forms junctional structures in adipocytes or acts as a monomer unknown
  13. 2025 High

    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

    PMID:41539562

    Open questions at the time
    • Whether CLDN5 inhibits HUWE1 by steric occlusion or allosteric mechanism not distinguished
    • Relevance of the CLDN5-β1-integrin axis in endothelial cells not tested

Open questions

Synthesis pass · forward-looking unresolved questions
  • 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.
  • 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

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 2 GO:0098772 molecular function regulator activity 2
Localization
GO:0005829 cytosol 2 GO:0005886 plasma membrane 2
Pathway
R-HSA-162582 Signal Transduction 4 R-HSA-1500931 Cell-Cell communication 2 R-HSA-392499 Metabolism of proteins 2 R-HSA-382551 Transport of small molecules 1

Evidence

Reading pass · 14 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1999 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. Immunofluorescence microscopy, immunoreplica electron microscopy, and reconstitution of TJ strands in transfected mouse L fibroblasts The Journal of cell biology High 10508865
2011 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. Promoter-reporter assays, p65 overexpression, TNF-α treatment of primary brain endothelial cells isolated from C57BL/6 mice Cytokine Medium 22138107
2012 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. ERG siRNA knockdown in endothelial cells, permeability assays, reporter/ChIP assays identifying CLDN5 as downstream ERG target The Journal of biological chemistry Medium 22235125
2014 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. Primary BMECs from nmMlck-knockout mice, nuclear fractionation of β-catenin/FoxO1, barrier dysfunction assays, Cldn5 promoter analysis Journal of cell science High 24522189
2020 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. Zebrafish in vivo model, in vitro BMECs, genetic autophagy inhibition, pharmacological autophagy blockade, STED super-resolution microscopy, TEER measurements Autophagy High 33280500
2022 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. Generation of stably transfected cell lines expressing wild-type or G60R claudin-5, ion permeability assays, protein modelling, sequence alignment Brain : a journal of neurology High 35714222
2022 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. Podocyte-specific Cldn5 knockout mice, diabetic nephropathy and ureteral obstruction models, nuclear fractionation of ZONAB, ChIP/reporter for WIF1 promoter, systemic WIF1 delivery Nature communications High 35332151
2023 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. Pharmacological ADAM17 inhibition, genetic ADAM17 knockdown, GNAZ knockdown, in vivo mouse blue-light exposure model, TEER/permeability assays, electroretinogram Fluids and barriers of the CNS High 37095509
2017 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. Immunoblot of genotyped human lung tissue, forced expression of long vs. short isoforms in transfected cells, immunofluorescence localization Annals of the New York Academy of Sciences Medium 28445614
2024 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. Dll4+/LacZ heterozygous mice, in vitro human brain microvascular endothelial cells, Notch pathway inhibition, vascular permeability assays, in vivo hyperoxia model The Journal of physiology Medium 38632887
2025 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. Adipocyte-specific Cldn5 knockout mice, gene expression profiling, ChIP/reporter assays for YBX3 binding to IL10 promoter, paracrine co-culture experiments, metabolic phenotyping Nature communications High 40610440
2026 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. Super-resolution imaging, Co-immunoprecipitation, domain-mapping mutagenesis, ubiquitination assays, Cldn5-KO mice with hypertensive and adriamycin injury models The Journal of biological chemistry High 41539562
2025 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. CUMS and HHCY mouse models, ChIP for H3K27me3 at Cldn5 promoter, RT-qPCR, behavioral testing, metabolic enzyme expression analysis Neurobiology of stress Medium 41035457
2025 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. All-atom molecular dynamics simulation, free energy calculations of water and ion permeation across wild-type and G60R claudin-5 multi-pore models bioRxivpreprint Low

Source papers

Stage 0 corpus · 37 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
1999 Endothelial claudin: claudin-5/TMVCF constitutes tight junction strands in endothelial cells. The Journal of cell biology 707 10508865
2005 Inactivation of the autophagy gene bec-1 triggers apoptotic cell death in C. elegans. Current biology : CB 196 16111945
2020 Autophagy alleviates hypoxia-induced blood-brain barrier injury via regulation of CLDN5 (claudin 5). Autophagy 145 33280500
2011 The Atg6/Vps30/Beclin 1 ortholog BEC-1 mediates endocytic retrograde transport in addition to autophagy in C. elegans. Autophagy 103 21183797
2011 TNF-alpha induced NFκB signaling and p65 (RelA) overexpression repress Cldn5 promoter in mouse brain endothelial cells. Cytokine 103 22138107
2023 The CLDN5 gene at the blood-brain barrier in health and disease. Fluids and barriers of the CNS 79 36978081
2012 ETS-related gene (ERG) controls endothelial cell permeability via transcriptional regulation of the claudin 5 (CLDN5) gene. The Journal of biological chemistry 75 22235125
2014 Non-muscle Mlck is required for β-catenin- and FoxO1-dependent downregulation of Cldn5 in IL-1β-mediated barrier dysfunction in brain endothelial cells. Journal of cell science 67 24522189
2022 Angelica sinensis polysaccharide improves rheumatoid arthritis by modifying the expression of intestinal Cldn5, Slit3 and Rgs18 through gut microbiota. International journal of biological macromolecules 57 35318077
2021 Brain DNA Methylation Patterns in CLDN5 Associated With Cognitive Decline. Biological psychiatry 47 33838873
2007 Autophagy genes unc-51 and bec-1 are required for normal cell size in Caenorhabditis elegans. Genetics 45 17890369
2022 Loss of CLDN5 in podocytes deregulates WIF1 to activate WNT signaling and contributes to kidney disease. Nature communications 38 35332151
2009 Disruption of the ether-a-go-go K+ channel gene BEC1/KCNH3 enhances cognitive function. The Journal of neuroscience : the official journal of the Society for Neuroscience 33 19923296
2023 Inflammation and Blood-Brain Barrier in Depression: Interaction of CLDN5 and IL6 Gene Variants in Stress-Induced Depression. The international journal of neuropsychopharmacology 26 36472886
2014 Polymorphism of the CLDN5 gene and Schizophrenia in an Iranian Population. Iranian journal of public health 26 26060683
2022 Recurrent de novo mutations in CLDN5 induce an anion-selective blood-brain barrier and alternating hemiplegia. Brain : a journal of neurology 22 35714222
2021 Super-resolved local recruitment of CLDN5 to filtration slits implicates a direct relationship with podocyte foot process effacement. Journal of cellular and molecular medicine 22 34156149
2018 CLDN5 affects lncRNAs acting as ceRNA dynamics contributing to regulating blood‑brain barrier permeability in tumor brain metastasis. Oncology reports 19 29328410
2014 C. elegans CEP-1/p53 and BEC-1 are involved in DNA repair. PloS one 19 24586407
2023 Variants in CLDN5 cause a syndrome characterized by seizures, microcephaly and brain calcifications. Brain : a journal of neurology 16 36477332
2017 Increased cerebral expressions of MMPs, CLDN5, OCLN, ZO1 and AQPs are associated with brain edema following fatal heat stroke. Scientific reports 16 28490769
2005 A study of the combined effect of the CLDN5 locus and the genes for the phospholipid metabolism pathway in schizophrenia. Prostaglandins, leukotrienes, and essential fatty acids 15 16181776
2020 Tight Junction-Related CLDN5 and CLDN6 Genes, and Gap Junction-Related GJB6 and GJB7 Genes Are Somatically Mutated in Gastric and Colorectal Cancers. Pathology oncology research : POR 14 32170581
2023 Blue light exposure collapses the inner blood-retinal barrier by accelerating endothelial CLDN5 degradation through the disturbance of GNAZ and the activation of ADAM17. Fluids and barriers of the CNS 13 37095509
2024 CLDN5: From structure and regulation to roles in tumors and other diseases beyond CNS disorders. Pharmacological research 11 38228255
2020 Serotonin/5-HT1A Signaling in the Neurovascular Unit Regulates Endothelial CLDN5 Expression. International journal of molecular sciences 11 33383868
2024 CD34+CLDN5+ tumor associated senescent endothelial cells through IGF2-IGF2R signaling increased cholangiocellular phenotype in hepatocellular carcinoma. Journal of advanced research 9 39674501
2024 Extracellular Vesicles From Preeclampsia Disrupt the Blood-Brain Barrier by Reducing CLDN5. Arteriosclerosis, thrombosis, and vascular biology 8 39665142
2017 Two common human CLDN5 alleles encode different open reading frames but produce one protein isoform. Annals of the New York Academy of Sciences 8 28445614
2024 Delta like 4 regulates cerebrovascular development and endothelial integrity via DLL4-NOTCH-CLDN5 pathway and is vulnerable to neonatal hyperoxia. The Journal of physiology 6 38632887
2010 Interaction of human immunodeficiency virus gp120 with the voltage-gated potassium channel BEC1. FEBS letters 6 20638388
2024 Loss of Cldn5 -and increase in Irf7-in the hippocampus and cerebral cortex of diabetic mice at the early symptomatic stage. Nutrition & diabetes 5 39147772
2025 Adipocyte CLDN5 promotes thermogenesis and energy expenditure through regulation of IL10 expression. Nature communications 3 40610440
2025 The silicon efflux transporter BEC1 is essential for bloom formation and stress tolerance in cucumber. Journal of integrative plant biology 2 40326667
2026 CLDN5 as a novel modulator of podocyte adhesion to extracellular matrix via β1-integrin binding. The Journal of biological chemistry 0 41539562
2026 Investigation of CLDN5 Gene 3'UTR rs10314 Polymorphism and Protein Levels in Children and Adolescents With ADHD: A Molecular and Clinical Correlation Study. Medical principles and practice : international journal of the Kuwait University, Health Science Centre 0 41774611
2025 High-intensity interval training improves cognitive dysfunction in chronically stressed mice through alleviating homocysteine-induced transcriptional repression of Cldn5. Neurobiology of stress 0 41035457