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Endothelial claudin: claudin-5/TMVCF constitutes tight junction strands in endothelial cells.

Morita K, Sasaki H, Furuse M, Tsukita S - J. Cell Biol. (1999)

Bottom Line: In contrast, in the kidney, the claudin-5/TMVCF signal was restricted to endothelial cells of arteries, but was undetectable in those of veins and capillaries.Furthermore, when claudin-5/TMVCF cDNA was introduced into mouse L fibroblasts, TJ strands were reconstituted that resembled those in endothelial cells in vivo, i.e., the extracellular face-associated TJs.These findings indicated that claudin-5/TMVCF is an endothelial cell-specific component of TJ strands.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, Faculty of Medicine, Kyoto University, Kyoto 606-8501, Japan.

ABSTRACT
Tight junctions (TJs) in endothelial cells are thought to determine vascular permeability. Recently, claudin-1 to -15 were identified as major components of TJ strands. Among these, claudin-5 (also called transmembrane protein deleted in velo-cardio-facial syndrome [TMVCF]) was expressed ubiquitously, even in organs lacking epithelial tissues, suggesting the possible involvement of this claudin species in endothelial TJs. We then obtained a claudin-6-specific polyclonal antibody and a polyclonal antibody that recognized both claudin-5/TMVCF and claudin-6. In the brain and lung, immunofluorescence microscopy with these polyclonal antibodies showed that claudin-5/TMVCF was exclusively concentrated at cell-cell borders of endothelial cells of all segments of blood vessels, but not at those of epithelial cells. Immunoreplica electron microscopy revealed that claudin-5/TMVCF was a component of TJ strands. In contrast, in the kidney, the claudin-5/TMVCF signal was restricted to endothelial cells of arteries, but was undetectable in those of veins and capillaries. In addition, in all other tissues we examined, claudin-5/TMVCF was specifically detected in endothelial cells of some segments of blood vessels, but not in epithelial cells. Furthermore, when claudin-5/TMVCF cDNA was introduced into mouse L fibroblasts, TJ strands were reconstituted that resembled those in endothelial cells in vivo, i.e., the extracellular face-associated TJs. These findings indicated that claudin-5/TMVCF is an endothelial cell-specific component of TJ strands.

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Localization of claudin-5/TMVCF in the lung. (a–f) Frozen sections of the lung were double stained with anti–claudin-5/6 pAb (a) and anti–VE-cadherin mAb (b), or anti–claudin-5/6 pAb (d) and antioccludin mAb (e). Since anti–claudin-6 pAb yielded no signals (data not shown), the anti–claudin-5/6 pAb staining can be considered to represent the distribution of claudin-5/TMVCF. Merged images (c and f) then revealed that claudin-5/TMVCF was precisely colocalized with VE-cadherin and that the claudin-5/TMVCF signals were complementary to the occludin signals. Considering that VE-cadherin and occludin were expressed exclusively in endothelial and epithelial cells, respectively, in the lungs, these findings indicated that the expression of claudin-5/TMVCF was restricted to endothelial cells. (g) Freeze–fracture replicas of the lung were labeled with anti–claudin-5/6 pAb. Note the specific labeling on the TJ strands of endothelial cells, which delineated the capillary lumen (indicated by asterisks). RC, erythrocytes; Cln, claudin; cad, cadherin. Bars: 20 μm in a–f (f); 100 nm (g).
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Figure 4: Localization of claudin-5/TMVCF in the lung. (a–f) Frozen sections of the lung were double stained with anti–claudin-5/6 pAb (a) and anti–VE-cadherin mAb (b), or anti–claudin-5/6 pAb (d) and antioccludin mAb (e). Since anti–claudin-6 pAb yielded no signals (data not shown), the anti–claudin-5/6 pAb staining can be considered to represent the distribution of claudin-5/TMVCF. Merged images (c and f) then revealed that claudin-5/TMVCF was precisely colocalized with VE-cadherin and that the claudin-5/TMVCF signals were complementary to the occludin signals. Considering that VE-cadherin and occludin were expressed exclusively in endothelial and epithelial cells, respectively, in the lungs, these findings indicated that the expression of claudin-5/TMVCF was restricted to endothelial cells. (g) Freeze–fracture replicas of the lung were labeled with anti–claudin-5/6 pAb. Note the specific labeling on the TJ strands of endothelial cells, which delineated the capillary lumen (indicated by asterisks). RC, erythrocytes; Cln, claudin; cad, cadherin. Bars: 20 μm in a–f (f); 100 nm (g).

Mentions: Next, we examined the distribution of claudin-5/TMVCF in the lungs, which contained both epithelial and endothelial cells and expressed fairly large amounts of claudin-5/TMVCF as detected by Northern blotting (Morita et al. 1999a). When frozen sections of the lung were double stained with anti–claudin-5/6 pAb and anti–VE-cadherin mAb, both signals completely overlapped (Fig. 4, a–c). In contrast, on double staining with anti–claudin-5/6 pAb and antioccludin mAb, the two signals did not overlap at all (Fig. 4, d–f). Furthermore, anti–claudin-6 pAb gave no detectable signals (data not shown). Considering that occludin was expressed in epithelial cells but not in most of the endothelial cells in nonneuronal tissues, these findings indicated that claudin-5/TMVCF was expressed in endothelial cells of all segments of blood vessels but not in epithelial cells delineating the alveolar space in the lung. Furthermore, immunoreplica analysis with anti–claudin-5/6 pAb revealed that claudin-5/TMVCF was localized on the TJ strands of the endothelial cells of the lung (Fig. 4 g).


Endothelial claudin: claudin-5/TMVCF constitutes tight junction strands in endothelial cells.

Morita K, Sasaki H, Furuse M, Tsukita S - J. Cell Biol. (1999)

Localization of claudin-5/TMVCF in the lung. (a–f) Frozen sections of the lung were double stained with anti–claudin-5/6 pAb (a) and anti–VE-cadherin mAb (b), or anti–claudin-5/6 pAb (d) and antioccludin mAb (e). Since anti–claudin-6 pAb yielded no signals (data not shown), the anti–claudin-5/6 pAb staining can be considered to represent the distribution of claudin-5/TMVCF. Merged images (c and f) then revealed that claudin-5/TMVCF was precisely colocalized with VE-cadherin and that the claudin-5/TMVCF signals were complementary to the occludin signals. Considering that VE-cadherin and occludin were expressed exclusively in endothelial and epithelial cells, respectively, in the lungs, these findings indicated that the expression of claudin-5/TMVCF was restricted to endothelial cells. (g) Freeze–fracture replicas of the lung were labeled with anti–claudin-5/6 pAb. Note the specific labeling on the TJ strands of endothelial cells, which delineated the capillary lumen (indicated by asterisks). RC, erythrocytes; Cln, claudin; cad, cadherin. Bars: 20 μm in a–f (f); 100 nm (g).
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Figure 4: Localization of claudin-5/TMVCF in the lung. (a–f) Frozen sections of the lung were double stained with anti–claudin-5/6 pAb (a) and anti–VE-cadherin mAb (b), or anti–claudin-5/6 pAb (d) and antioccludin mAb (e). Since anti–claudin-6 pAb yielded no signals (data not shown), the anti–claudin-5/6 pAb staining can be considered to represent the distribution of claudin-5/TMVCF. Merged images (c and f) then revealed that claudin-5/TMVCF was precisely colocalized with VE-cadherin and that the claudin-5/TMVCF signals were complementary to the occludin signals. Considering that VE-cadherin and occludin were expressed exclusively in endothelial and epithelial cells, respectively, in the lungs, these findings indicated that the expression of claudin-5/TMVCF was restricted to endothelial cells. (g) Freeze–fracture replicas of the lung were labeled with anti–claudin-5/6 pAb. Note the specific labeling on the TJ strands of endothelial cells, which delineated the capillary lumen (indicated by asterisks). RC, erythrocytes; Cln, claudin; cad, cadherin. Bars: 20 μm in a–f (f); 100 nm (g).
Mentions: Next, we examined the distribution of claudin-5/TMVCF in the lungs, which contained both epithelial and endothelial cells and expressed fairly large amounts of claudin-5/TMVCF as detected by Northern blotting (Morita et al. 1999a). When frozen sections of the lung were double stained with anti–claudin-5/6 pAb and anti–VE-cadherin mAb, both signals completely overlapped (Fig. 4, a–c). In contrast, on double staining with anti–claudin-5/6 pAb and antioccludin mAb, the two signals did not overlap at all (Fig. 4, d–f). Furthermore, anti–claudin-6 pAb gave no detectable signals (data not shown). Considering that occludin was expressed in epithelial cells but not in most of the endothelial cells in nonneuronal tissues, these findings indicated that claudin-5/TMVCF was expressed in endothelial cells of all segments of blood vessels but not in epithelial cells delineating the alveolar space in the lung. Furthermore, immunoreplica analysis with anti–claudin-5/6 pAb revealed that claudin-5/TMVCF was localized on the TJ strands of the endothelial cells of the lung (Fig. 4 g).

Bottom Line: In contrast, in the kidney, the claudin-5/TMVCF signal was restricted to endothelial cells of arteries, but was undetectable in those of veins and capillaries.Furthermore, when claudin-5/TMVCF cDNA was introduced into mouse L fibroblasts, TJ strands were reconstituted that resembled those in endothelial cells in vivo, i.e., the extracellular face-associated TJs.These findings indicated that claudin-5/TMVCF is an endothelial cell-specific component of TJ strands.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, Faculty of Medicine, Kyoto University, Kyoto 606-8501, Japan.

ABSTRACT
Tight junctions (TJs) in endothelial cells are thought to determine vascular permeability. Recently, claudin-1 to -15 were identified as major components of TJ strands. Among these, claudin-5 (also called transmembrane protein deleted in velo-cardio-facial syndrome [TMVCF]) was expressed ubiquitously, even in organs lacking epithelial tissues, suggesting the possible involvement of this claudin species in endothelial TJs. We then obtained a claudin-6-specific polyclonal antibody and a polyclonal antibody that recognized both claudin-5/TMVCF and claudin-6. In the brain and lung, immunofluorescence microscopy with these polyclonal antibodies showed that claudin-5/TMVCF was exclusively concentrated at cell-cell borders of endothelial cells of all segments of blood vessels, but not at those of epithelial cells. Immunoreplica electron microscopy revealed that claudin-5/TMVCF was a component of TJ strands. In contrast, in the kidney, the claudin-5/TMVCF signal was restricted to endothelial cells of arteries, but was undetectable in those of veins and capillaries. In addition, in all other tissues we examined, claudin-5/TMVCF was specifically detected in endothelial cells of some segments of blood vessels, but not in epithelial cells. Furthermore, when claudin-5/TMVCF cDNA was introduced into mouse L fibroblasts, TJ strands were reconstituted that resembled those in endothelial cells in vivo, i.e., the extracellular face-associated TJs. These findings indicated that claudin-5/TMVCF is an endothelial cell-specific component of TJ strands.

Show MeSH
Related in: MedlinePlus