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Tricellulin constitutes a novel barrier at tricellular contacts of epithelial cells.

Ikenouchi J, Furuse M, Furuse K, Sasaki H, Tsukita S, Tsukita S - J. Cell Biol. (2005)

Bottom Line: In this study, we identify tricellulin, the first integral membrane protein that is concentrated at the vertically oriented TJ strands of tricellular contacts.When tricellulin expression was suppressed with RNA interference, the epithelial barrier was compromised, and tricellular contacts and bTJs were disorganized.These findings indicate the critical function of tricellulin for formation of the epithelial barrier.

View Article: PubMed Central - PubMed

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

ABSTRACT
For epithelia to function as barriers, the intercellular space must be sealed. Sealing two adjacent cells at bicellular tight junctions (bTJs) is well described with the discovery of the claudins. Yet, there are still barrier weak points at tricellular contacts, where three cells join together. In this study, we identify tricellulin, the first integral membrane protein that is concentrated at the vertically oriented TJ strands of tricellular contacts. When tricellulin expression was suppressed with RNA interference, the epithelial barrier was compromised, and tricellular contacts and bTJs were disorganized. These findings indicate the critical function of tricellulin for formation of the epithelial barrier.

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Schematic drawing of the organization of tTJs. One tricellular contact (left drawing) is enlarged in the right drawing. See the Introduction for details.
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fig1: Schematic drawing of the organization of tTJs. One tricellular contact (left drawing) is enlarged in the right drawing. See the Introduction for details.

Mentions: To be more exact, these TJs should be called bicellular TJs (bTJs) between two adjacent cells. At tricellular contacts, where there are three epithelial cells, TJs have been thought to be structurally specialized and are referred to as tricellular TJs (tTJs). The ultrastructure of tTJs has been examined in detail by freeze-fracture replica electron microscopy (Staehelin et al., 1969; Friend and Gilula, 1972; Staehelin, 1973; Wade and Karnovsky, 1974; Walker et al., 1985). As schematically drawn in Fig. 1, the bTJs are discontinuous at tricellular contacts. As bTJs approach a tricellular contact region, their network extends basolaterally. The central area of these vertically oriented tTJs is composed of three pairs of TJ strands called central sealing elements (Staehelin, 1973), which appear as vertical extensions of the most apical paired strands of the bTJs. At the corner of tricellular contacts, two vertical strands of central sealing elements are associated tightly and laterally within individual plasma membranes, resulting in the formation of a central tube that could be a weak point for the epithelial barrier. From the viewpoint of the epithelial barrier, these two TJ types, bTJs and tTJs, should be considered separately, although the distinction has been largely ignored.


Tricellulin constitutes a novel barrier at tricellular contacts of epithelial cells.

Ikenouchi J, Furuse M, Furuse K, Sasaki H, Tsukita S, Tsukita S - J. Cell Biol. (2005)

Schematic drawing of the organization of tTJs. One tricellular contact (left drawing) is enlarged in the right drawing. See the Introduction for details.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2171318&req=5

fig1: Schematic drawing of the organization of tTJs. One tricellular contact (left drawing) is enlarged in the right drawing. See the Introduction for details.
Mentions: To be more exact, these TJs should be called bicellular TJs (bTJs) between two adjacent cells. At tricellular contacts, where there are three epithelial cells, TJs have been thought to be structurally specialized and are referred to as tricellular TJs (tTJs). The ultrastructure of tTJs has been examined in detail by freeze-fracture replica electron microscopy (Staehelin et al., 1969; Friend and Gilula, 1972; Staehelin, 1973; Wade and Karnovsky, 1974; Walker et al., 1985). As schematically drawn in Fig. 1, the bTJs are discontinuous at tricellular contacts. As bTJs approach a tricellular contact region, their network extends basolaterally. The central area of these vertically oriented tTJs is composed of three pairs of TJ strands called central sealing elements (Staehelin, 1973), which appear as vertical extensions of the most apical paired strands of the bTJs. At the corner of tricellular contacts, two vertical strands of central sealing elements are associated tightly and laterally within individual plasma membranes, resulting in the formation of a central tube that could be a weak point for the epithelial barrier. From the viewpoint of the epithelial barrier, these two TJ types, bTJs and tTJs, should be considered separately, although the distinction has been largely ignored.

Bottom Line: In this study, we identify tricellulin, the first integral membrane protein that is concentrated at the vertically oriented TJ strands of tricellular contacts.When tricellulin expression was suppressed with RNA interference, the epithelial barrier was compromised, and tricellular contacts and bTJs were disorganized.These findings indicate the critical function of tricellulin for formation of the epithelial barrier.

View Article: PubMed Central - PubMed

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

ABSTRACT
For epithelia to function as barriers, the intercellular space must be sealed. Sealing two adjacent cells at bicellular tight junctions (bTJs) is well described with the discovery of the claudins. Yet, there are still barrier weak points at tricellular contacts, where three cells join together. In this study, we identify tricellulin, the first integral membrane protein that is concentrated at the vertically oriented TJ strands of tricellular contacts. When tricellulin expression was suppressed with RNA interference, the epithelial barrier was compromised, and tricellular contacts and bTJs were disorganized. These findings indicate the critical function of tricellulin for formation of the epithelial barrier.

Show MeSH