The mouse cortical collecting duct cell line presents a tight epithelium with regulated ion and water transport. The epithelial sodium channel (ENaC) is localized in the apical membrane and constitutes the rate-limiting step for sodium entry, thereby enabling transepithelial transport of sodium ions. The membrane-bound serine protease Tmprss2 is co-expressed with the alpha subunit of ENaC. αENaC gene expression followed the Tmprss2 expression, and the absence of Tmprss2 resulted not only in down-regulation of αENaC gene and protein expression but also in abolished transepithelial sodium transport. In addition, RNA-sequencing analyses unveiled drastic down-regulation of the membrane-bound protease CAP3/St14, the epithelial adhesion molecule EpCAM, and the tight junction proteins claudin-7 and claudin-3 as also confirmed by immunohistochemistry. In summary, our data clearly demonstrate a dual role of Tmprss2 in maintaining not only ENaC-mediated transepithelial but also EpCAM/claudin-7-mediated paracellular barrier; the tight epithelium of the mouse renal mCCD cells becomes leaky. Our working model proposes that Tmprss2 acts via CAP3/St14 on EpCAM/claudin-7 tight junction complexes and through regulating transcription of αENaC on ENaC-mediated sodium transport.

中文翻译：

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Tmprss2 维持上皮屏障完整性和跨上皮钠转运。

小鼠皮质集合管细胞系呈现出具有受调节的离子和水运输的紧密上皮。上皮钠通道（ENaC）位于顶膜，构成钠进入的限速步骤，从而实现钠离子的跨上皮转运。膜结合丝氨酸蛋白酶Tmprss2与 ENaC 的 α 亚基共表达。αENaC 基因表达跟随Tmprss2表达，Tmprss2 的缺失不仅导致 αENaC 基因和蛋白质表达下调，而且导致跨上皮钠转运被废除。此外，RNA测序分析揭示了膜结合蛋白酶CAP3/St14、上皮粘附分子EpCAM以及紧密连接蛋白claudin-7和claudin-3的急剧下调，免疫组织化学也证实了这一点。总之，我们的数据清楚地证明了 Tmprss2 在维持 ENaC 介导的跨上皮屏障和 EpCAM/claudin-7 介导的细胞旁屏障方面的双重作用；小鼠肾 mCCD 细胞的紧密上皮变得渗漏。我们的工作模型提出，Tmprss2 通过 CAP3/St14 对 EpCAM/claudin-7 紧密连接复合物起作用，并通过调节 ENaC 介导的钠转运上的 αENaC 转录。