Affinage

CLDN5

Claudin-5 · UniProt O00501

Length
218 aa
Mass
23.1 kDa
Annotated
2026-06-09
31 papers in source corpus 13 papers cited in narrative 14 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

CLDN5 is an endothelial cell-enriched, four-transmembrane claudin that serves as a structural component of tight junction strands and establishes paracellular barriers, most prominently the blood-brain and inner blood-retinal barriers (PMID:10508865). Its barrier-forming activity was defined by reconstitution of extracellular face-associated tight junction strands when CLDN5 cDNA is introduced into fibroblasts lacking endogenous junctions (PMID:10508865). CLDN5 abundance at endothelial junctions is set by convergent transcriptional inputs — it is activated by the ETS factor ERG (PMID:22235125) and by DLL4-NOTCH signaling through an NICD-RBPJ axis (PMID:38632887), and repressed by inflammatory NF-κB/p65 signaling downstream of TNF-α (PMID:22138107) and by an IL-1β–nmMLCK–β-catenin/FoxO1 pathway (PMID:24522189). Post-transcriptionally, junctional CLDN5 is removed by CAV1-mediated redistribution into the cytosol followed by autophagic degradation under hypoxia (PMID:33280500) and by ADAM17-mediated proteolysis that is normally restrained by the inhibitory G protein GNAZ (PMID:37095509). A de novo G60R mutation in the first extracellular loop converts CLDN5 from a pure barrier protein into an anion-selective paracellular channel, the first gain-of-function mutation described in the claudin family (PMID:35714222). Beyond endothelial junctions, CLDN5 has distinct non-junctional roles: in podocytes it stabilizes β1-integrin by blocking HUWE1-mediated ubiquitination at K774 (PMID:41539562) and governs a ZO1-ZONAB-WIF1 axis that restrains WNT signaling (PMID:35332151), and in adipocytes it controls YBX3 localization and IL10-dependent paracrine thermogenic signaling (PMID:40610440).

Mechanistic history

Synthesis pass · year-by-year structured walk · 12 steps
  1. 1999 High

    Established CLDN5 as an endothelial-specific structural building block of tight junction strands rather than a passive marker, by showing it is sufficient to nucleate junction strands in cells that have none.

    Evidence Immunofluorescence and immunoreplica EM localization plus cDNA reconstitution in L fibroblasts

    PMID:10508865

    Open questions at the time
    • Did not define the heterotypic claudin partners or ZO adaptors required in vivo
    • No mechanism for how strand architecture sets ion or size selectivity
  2. 2011 Medium

    Identified inflammatory transcriptional repression as a route to barrier loss, showing NF-κB/p65 is sufficient to silence the Cldn5 promoter downstream of TNF-α.

    Evidence Promoter-reporter assays, p65 overexpression, TNF-α treatment of brain endothelial cells with qPCR/western readouts

    PMID:22138107

    Open questions at the time
    • Exact p65 binding element within the conserved promoter region not mapped
    • Single lab, did not test in vivo barrier consequences
  3. 2012 Medium

    Placed the ETS factor ERG upstream as a positive transcriptional driver of CLDN5 required for endothelial barrier maintenance.

    Evidence ERG siRNA knockdown with permeability assays, stress-fiber/gap quantification, and reporter assays

    PMID:22235125

    Open questions at the time
    • Direct ERG occupancy of the CLDN5 promoter not resolved beyond reporter assays
    • Relationship to NF-κB repression not integrated
  4. 2014 High

    Resolved the signaling chain linking IL-1β to CLDN5 repression, identifying nmMLCK as the obligatory transducer driving nuclear β-catenin/FoxO1 to silence Cldn5.

    Evidence Primary BMVECs from nmMlck-null mice, IL-1β treatment, nuclear translocation assays, transcription and permeability readouts

    PMID:24522189

    Open questions at the time
    • Whether β-catenin/FoxO1 bind the Cldn5 promoter directly not shown
    • How a cytoskeletal kinase controls transcription factor nuclear entry not mechanistically detailed
  5. 2020 High

    Defined a post-transcriptional turnover route for junctional CLDN5, showing CAV1 redistributes membranous CLDN5 to the cytosol and autophagy clears the aggregates, with autophagy blockade worsening barrier breakdown.

    Evidence Zebrafish BBB and in vitro BMEC models, CAV1 manipulation, genetic/chemical autophagy blockade, STED imaging, TEER

    PMID:33280500

    Open questions at the time
    • Trigger coupling hypoxia to CAV1 engagement of CLDN5 not defined
    • Whether degraded CLDN5 is recycled or replaced not addressed
  6. 2020 Medium

    Linked GPCR signaling to CLDN5 levels, showing serotonin/5-HT1A signaling enhances endothelial CLDN5 and implicating aberrant PKA activation in disease-associated barrier breakdown.

    Evidence Post-mortem human brain immunohistochemistry, BMVEC-pericyte co-culture, pharmacological 5-HT1A stimulation

    PMID:33383868

    Open questions at the time
    • Causal chain from 5-HT1A/PKA to CLDN5 transcription or stability not dissected
    • Correlative human tissue data, not interventional
  7. 2022 High

    Demonstrated CLDN5 can be a conduction element, not just a seal, by showing the G60R extracellular-loop mutation creates an anion-selective paracellular channel — the first claudin gain-of-function.

    Evidence Stable WT and G60R CLDN5 cell lines, ion permeability electrophysiology, structural modeling, barrier assays

    PMID:35714222

    Open questions at the time
    • Atomic structure of the conducting pore not solved
    • In vivo neurological consequences of altered ion flux not established
  8. 2022 High

    Uncovered a non-junctional signaling role in podocytes, where CLDN5 sustains ZO1 and restrains ZONAB-driven WIF1 repression to keep WNT signaling off, with paracrine WIF1 limiting tubular fibrosis.

    Evidence Podocyte-specific Cldn5 knockout mice, diabetic nephropathy and obstruction models, ZONAB localization, WIF1 rescue

    PMID:35332151

    Open questions at the time
    • How CLDN5 controls ZO1 levels and ZONAB sequestration mechanistically not defined
    • Whether the same axis operates in endothelial cells not tested
  9. 2023 High

    Established a light-triggered proteolytic mechanism of barrier disruption: blue light releases ADAM17 from its inhibitory partner GNAZ, leading to ADAM17-mediated CLDN5 degradation and inner blood-retinal barrier loss.

    Evidence Endothelial blue-light exposure, GNAZ knockdown, ADAM17 genetic/pharmacological inhibition, in vivo iBRB leakage, electroretinography

    PMID:37095509

    Open questions at the time
    • Whether ADAM17 cleaves CLDN5 directly or acts via an intermediate not resolved
    • Photoreceptive sensor upstream of GNAZ release not identified
  10. 2024 Medium

    Added DLL4-NOTCH-RBPJ as a developmental/maintenance transcriptional input to CLDN5 and BBB integrity, shown by CLDN5 downregulation and microvascular abnormalities in Dll4 haploinsufficient mice.

    Evidence Dll4+/LacZ mice plus human BMEC studies, vascular permeability assays, NOTCH pathway analysis

    PMID:38632887

    Open questions at the time
    • Direct RBPJ occupancy at the CLDN5 locus not demonstrated
    • Integration with ERG and NF-κB inputs not addressed
  11. 2025 High

    Extended CLDN5 function to metabolic control, showing adipocyte CLDN5 governs YBX3 localization and IL10 transcription to drive paracrine thermogenic signaling.

    Evidence Adipocyte-specific Cldn5 knockout mice, YBX3 localization, IL10 promoter/3'-UTR binding, IL10R paracrine experiments, metabolic phenotyping

    PMID:40610440

    Open questions at the time
    • How a junctional protein controls cytoplasmic-nuclear YBX3 partitioning not mechanistically defined
    • Whether CLDN5 binds YBX3 directly not shown
  12. 2026 High

    Defined a direct protein-stabilization role, showing podocyte CLDN5 binds β1-integrin via its intracellular loop and C-terminus and blocks HUWE1-mediated ubiquitination at K774 to prevent proteasomal degradation.

    Evidence Super-resolution colocalization, Co-IP, domain-mapping mutagenesis, ubiquitination and proteasome-inhibition assays, Cldn5-KO injury mouse models

    PMID:41539562

    Open questions at the time
    • Whether CLDN5 competes with HUWE1 for the same site or sterically shields K774 not resolved
    • Generalizability of integrin protection beyond podocytes not tested

Open questions

Synthesis pass · forward-looking unresolved questions
  • How a single tight-junction protein toggles between paracellular barrier/channel function and its diverse non-junctional roles (integrin stabilization, WNT restraint, metabolic signaling) through distinct binding partners and domains remains unresolved.
  • No atomic structure of CLDN5 strands or the G60R pore confirmed experimentally
  • Determinants directing CLDN5 to junctional versus non-junctional functions unknown
  • Whether transcriptional, trafficking, and proteolytic regulators act combinatorially in the same cell not integrated

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 1 GO:0005215 transporter activity 1 GO:0098631 cell adhesion mediator activity 1
Localization
GO:0005886 plasma membrane 2 GO:0005829 cytosol 1
Pathway
R-HSA-162582 Signal Transduction 2 R-HSA-168256 Immune System 2 R-HSA-1500931 Cell-Cell communication 1
Complex memberships
tight junction strand

Evidence

Reading pass · 14 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1999 CLDN5/TMVCF localizes exclusively to tight junction strands in endothelial cells of blood vessels (not epithelial cells), and when cDNA is introduced into mouse L fibroblasts, it reconstitutes extracellular face-associated TJ strands, establishing CLDN5 as an endothelial cell-specific structural component of tight junction strands. Immunofluorescence microscopy, immunoreplica electron microscopy, cDNA transfection into L fibroblasts (reconstitution assay) The Journal of cell biology High 10508865
2012 The ETS transcription factor ERG directly regulates CLDN5 gene expression in endothelial cells; ERG knockdown reduces CLDN5 expression, increases endothelial permeability, and promotes stress fiber and gap formation, placing ERG upstream of CLDN5 in the transcriptional control of barrier function. ERG siRNA knockdown in endothelial cells, permeability assays, stress fiber/gap quantification, transcriptional reporter assays The Journal of biological chemistry Medium 22235125
2011 TNF-α reduces CLDN5 promoter activity and mRNA expression in brain endothelial cells via NF-κB signaling; overexpression of the NF-κB subunit p65 (RelA) alone is sufficient to repress the Cldn5 promoter, and a conserved promoter region is required for this downregulation. Promoter-reporter assays, p65 overexpression, TNF-α treatment of primary brain endothelial cells, qPCR, western blot Cytokine Medium 22138107
2014 IL-1β–induced CLDN5 transcriptional repression in brain microvascular endothelial cells requires non-muscle MLCK (nmMlck): nmMlck mediates nuclear translocation of β-catenin and FoxO1, which then repress Cldn5 transcription, and primary BMVECs from nmMlck-null mice are protected from this repression. Primary BMVEC isolation from nmMlck-null mice (genetic loss-of-function), IL-1β treatment, nuclear translocation assays for β-catenin and FoxO1, Cldn5 mRNA/protein quantification, barrier permeability assays 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 then degrades CAV1 and cytosolic aggregated CLDN5. Blocking autophagy genetically or pharmacologically aggravates cytosolic CLDN5 accumulation and worsens blood-brain barrier breakdown. In vivo zebrafish BBB models, in vitro BMEC culture, CAV1 genetic manipulation, autophagy blockade (chemical and genetic), STED super-resolution microscopy, TEER measurements Autophagy High 33280500
2022 A de novo missense mutation G60R in the first extracellular loop of CLDN5 converts its function from a purely barrier-forming tight junction protein to an anion-selective channel: stably transfected cell lines with G60R CLDN5 still form tight junctions but display attenuated small-molecule barrier with higher Cl− and lower Na+ permeability, representing the first gain-of-function mutation in the claudin gene family. Stable transfection of wild-type and G60R CLDN5 cell lines, ion permeability electrophysiology, protein structural modeling, sequence alignment, barrier function assays Brain : a journal of neurology High 35714222
2022 In podocytes, CLDN5 deletion reduces ZO1 expression and induces nuclear translocation of ZONAB, which transcriptionally downregulates WIF1 (WNT inhibitory factor-1), leading to activation of the WNT signaling pathway; podocyte-derived WIF1 also acts in paracrine on tubular epithelial cells to suppress fibrosis. Podocyte-specific Cldn5 knockout mice, diabetic nephropathy and ureteral obstruction mouse models, ZONAB nuclear localization assays, WIF1 transcriptional analysis, systemic WIF1 delivery rescue experiments Nature communications High 35332151
2023 Blue light exposure causes rapid ADAM17-mediated degradation of endothelial CLDN5, disrupting tight junctions and the inner blood-retinal barrier. Under basal conditions ADAM17 is sequestered by the inhibitory G protein GNAZ; blue light releases ADAM17 from GNAZ. GNAZ knockdown phenocopies blue light effects (ADAM17 hyperactivation, CLDN5 downregulation, barrier permeability). Pharmacological or genetic inhibition of ADAM17 prevents CLDN5 degradation. In vitro endothelial cell blue-light exposure, GNAZ knockdown, ADAM17 pharmacological and genetic inhibition, western blot for CLDN5 protein levels, in vivo mouse iBRB leakage, electroretinography Fluids and barriers of the CNS High 37095509
2024 DLL4-NOTCH signaling regulates endothelial CLDN5 expression and blood-brain barrier integrity through the NOTCH-NICD-RBPJ-CLDN5 pathway; DLL4 insufficiency (Dll4+/LacZ mice) leads to downregulation of CLDN5, persistent abnormalities in brain microvasculature, and increased vascular permeability both in vivo and in vitro. Dll4+/LacZ and Dll4+/+ mouse models, human brain microvascular endothelial cell in vitro studies, in vivo vascular permeability assays, NOTCH pathway component analysis The Journal of physiology Medium 38632887
2020 Serotonin/5-HT1A signaling enhances endothelial CLDN5 expression in brain microvascular endothelial cells; the 5-HT1A receptor is expressed in BMVECs and mural cells, and PKA is aberrantly activated in both cell types in schizophrenic prefrontal cortex, coinciding with site-selective CLDN5 breakdown. Immunohistochemistry on post-mortem human brain tissue, two-dimensional co-culture of BMVECs and pericytes, pharmacological 5-HT1A receptor stimulation, CLDN5 expression quantification International journal of molecular sciences Medium 33383868
2017 The human CLDN5 gene contains a high-frequency SNP (rs885985) creating two ORFs (303 or 218 amino acid isoforms), but only the 218 aa form is detected by immunoblot in human lung tissue. When forcibly expressed in transfected cells, the long 303 aa form is retained in intracellular compartments and does not localize to the plasma membrane, in contrast to the 218 aa form which localizes to intercellular junctions. Genotyping of human lung tissue, immunoblot, transfection of long- and short-form CLDN5 constructs in cells with subcellular localization imaging Annals of the New York Academy of Sciences Medium 28445614
2025 CLDN5 in adipocytes (non-tight junction context) affects subcellular localization of Y-box protein 3 (YBX3); CLDN5 deficiency causes YBX3 mislocalization, which reduces IL10 expression (YBX3 directly binds the IL10 promoter and 3'-UTR); secreted IL10 then acts in paracrine via IL10R on neighboring thermogenic adipocytes to regulate thermogenesis and energy expenditure. Adipocyte-specific Cldn5 knockout mice, YBX3 localization assays, IL10 promoter binding assays, IL10R paracrine signaling experiments, metabolic phenotyping (thermogenesis, energy expenditure, glucose tolerance) Nature communications High 40610440
2026 CLDN5 in podocytes forms a stable complex with β1-integrin via its intracellular loop and C-terminal domains; CLDN5 prevents HUWE1-mediated ubiquitination at lysine K774 of β1-integrin, thereby protecting β1-integrin from proteasomal degradation and ensuring its proper membrane localization. CLDN5 deletion impairs podocyte adhesion, spreading, and mechanical stress resistance in vitro, and worsens renal injury in vivo. Super-resolution imaging (colocalization at podocyte-GBM interface), Co-IP (stable complex), domain-mapping mutagenesis (intracellular loop and C-terminal domains), ubiquitination assays (HUWE1, K774), proteasome inhibition, Cldn5-KO mice with hypertensive and adriamycin injury models The Journal of biological chemistry High 41539562
2025 Molecular dynamics free energy calculations show that multi-pore Claudin-5 TJ strand models create electrostatic barriers to ion permeation higher than in single-pore architectures, and only the multi-Pore I structural model recapitulates the anion-selective permeability phenotype of the G60R variant, providing structural validation of the paracellular pore mechanism. Multi-microsecond all-atom molecular dynamics simulations, free energy calculations for water and ion permeation across multi-protomer (16-subunit) claudin-5 TJ models bioRxivpreprint Low

Source papers

Stage 0 corpus · 31 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 709 10508865
2020 Autophagy alleviates hypoxia-induced blood-brain barrier injury via regulation of CLDN5 (claudin 5). Autophagy 152 33280500
2011 TNF-alpha induced NFκB signaling and p65 (RelA) overexpression repress Cldn5 promoter in mouse brain endothelial cells. Cytokine 107 22138107
2023 The CLDN5 gene at the blood-brain barrier in health and disease. Fluids and barriers of the CNS 85 36978081
2012 ETS-related gene (ERG) controls endothelial cell permeability via transcriptional regulation of the claudin 5 (CLDN5) gene. The Journal of biological chemistry 77 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 69 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 60 35318077
2021 Brain DNA Methylation Patterns in CLDN5 Associated With Cognitive Decline. Biological psychiatry 51 33838873
2022 Loss of CLDN5 in podocytes deregulates WIF1 to activate WNT signaling and contributes to kidney disease. Nature communications 39 35332151
2023 Inflammation and Blood-Brain Barrier in Depression: Interaction of CLDN5 and IL6 Gene Variants in Stress-Induced Depression. The international journal of neuropsychopharmacology 28 36472886
2014 Polymorphism of the CLDN5 gene and Schizophrenia in an Iranian Population. Iranian journal of public health 28 26060683
2022 Recurrent de novo mutations in CLDN5 induce an anion-selective blood-brain barrier and alternating hemiplegia. Brain : a journal of neurology 23 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
2023 Variants in CLDN5 cause a syndrome characterized by seizures, microcephaly and brain calcifications. Brain : a journal of neurology 18 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
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 15 37095509
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
2024 CLDN5: From structure and regulation to roles in tumors and other diseases beyond CNS disorders. Pharmacological research 14 38228255
2024 CD34+CLDN5+ tumor associated senescent endothelial cells through IGF2-IGF2R signaling increased cholangiocellular phenotype in hepatocellular carcinoma. Journal of advanced research 14 39674501
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
2024 Extracellular Vesicles From Preeclampsia Disrupt the Blood-Brain Barrier by Reducing CLDN5. Arteriosclerosis, thrombosis, and vascular biology 11 39665142
2020 Serotonin/5-HT1A Signaling in the Neurovascular Unit Regulates Endothelial CLDN5 Expression. International journal of molecular sciences 11 33383868
2017 Two common human CLDN5 alleles encode different open reading frames but produce one protein isoform. Annals of the New York Academy of Sciences 9 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
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
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 <italic>CLDN5</italic> Gene 3' Untranslated Region rs10314 Polymorphism and Protein Levels in Children and Adolescents with Attention-Deficit Hyperactivity Disorder: A Molecular and Clinical Correlation Study. Medical principles and practice : international journal of the Kuwait University, Health Science Centre 0 41774611
2026 A longitudinal study of CLDN5 DNA methylation and PTSD. Journal of behavioral medicine 0 42262642
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

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