Leibniz-Institut für Molekulare Pharmakologie, FMP, Robert-Rössle-Str. 10, 13125, Berlin, Germany.
Cell Mol Life Sci. 2010 Jun;67(12):2131-40. doi: 10.1007/s00018-010-0332-8. Epub 2010 Mar 24.
Tight junctions control paracellular permeability. Here, we analyzed the impact of residues in the second extracellular loop (ECL2) of mouse claudin-5 on paracellular permeability. Stable expression of claudin-5(wild type) in MDCK-II cells-but not that of mutants R145A, Y148A, Y158A or E159Q-increased transepithelial electrical resistance and decreased fluorescein permeation. Expression of claudin-5(Y148A), (Y158A) or (E159Q) enhanced permeability of FITC-dextran(10 kDa), which was unchanged in cells expressing claudin-5(wild type) or claudin-5(R145A). In contrast, targeting to tight junctions, strand morphology and tight junction assembly were unchanged. It is concluded that R145 is unessential for trans-interaction of claudin-5, but necessary for tightening against small solutes and ions. The highly conserved residues Y148, Y158 and E159 in ECL2 of claudin-5 contribute to homo- and/or heterophilic trans-interaction between classic claudins and thereby tighten the paracellular space against ions, small and large molecules. These results provide novel insights into the molecular function of tight junctions.
紧密连接控制细胞旁通透性。在这里，我们分析了小鼠紧密连接蛋白-5（claudin-5）第二细胞外环（ECL2）残基对细胞旁通透性的影响。claudin-5（野生型）在 MDCK-II 细胞中的稳定表达-而非突变体 R145A、Y148A、Y158A 或 E159Q-增加了上皮细胞电阻并降低了荧光素通透性。claudin-5（Y148A）、（Y158A）或（E159Q）的表达增强了 FITC-葡聚糖（10 kDa）的通透性，而在表达 claudin-5（野生型）或 claudin-5（R145A）的细胞中，这种通透性没有改变。相比之下，靶向紧密连接、链形态和紧密连接组装没有变化。因此得出结论，R145 对于 claudin-5 的跨相互作用不是必需的，但对于防止小分子和离子的渗漏是必需的。ECL2 中的高度保守残基 Y148、Y158 和 E159 有助于经典紧密连接蛋白之间的同型和/或异型跨相互作用，从而使细胞旁空间对离子、小分子和大分子保持紧密。这些结果为紧密连接的分子功能提供了新的见解。
