SODIUM CHANNEL APICAL PROTEIN XENOPUS (APX) INTERACTIONS

钠(Na)重吸收肾上皮细胞含有阿米洛利 敏感的钠通道被隔离到微绒毛结构域 顶膜。上皮性钠通道(ENaCs)介导钠离子内流 从生电钠第一阶段的根尖液中分离出来 运输。ENaC定位于顶膜结构域是 对于钠跨上皮细胞的矢量运输是必不可少的。 ENaC的最新分子表征提供了机会 确定参与建立和维持的相关蛋白质 顶膜结构域内的enac，如外周膜和 膜细胞骨架蛋白。我们的长期目标是了解 ENaC与相关蛋白质之间的分子相互作用 在微绒毛内参与建立和维护ENaC 肾上皮细胞顶膜的结构域及其如何 相互作用在正常和病理生理条件下都受到调节 条件。在本应用程序中，我们建议重点关注交互 在ENaC和Apx之间，一种新的与ENaC相关的ENaC 最初从非洲爪哇克隆的蛋白质。最近一个人类的mRNA Apx的同源基因已在肾脏中被鉴定。根据提供的数据 在初步研究中，我们假设Apx与ENaC相互作用 以及基于血影蛋白的细胞骨架的元件和功能 在微绒毛域内隔离和/或稳定ENaC 重吸收钠的肾上皮细胞的顶膜。一共有三个 具体目标：1)检验Apx与ENaC相互作用的假设 和基于血影蛋白的顶膜细胞骨架的组成成分 重吸收肾上皮细胞。2)检验Apx的假设 在微绒毛域内隔离和/或稳定ENaC 细胞表面。3)检验Apx同源表示的假设 在哺乳动物肾脏的重吸收肾上皮中，这 同源基因与哺乳动物的ENaC有关。预计在这次会议上 拟议研究的结论我们将确定Apx的作用 及其哺乳动物同系物在隔离和/或稳定ENaC中的作用 重吸收钠肾顶膜的微绒毛域 上皮细胞。此外，结果将增进我们对 ENaC相关蛋白在此过程中的调控作用 重要的离子通道。此外，预计结果将 将有助于我们更好地了解 肾上皮细胞顶膜细胞骨架及其相关蛋白 正常生理和病理生理条件下的细胞 如缺血和多囊肾病。

Sodium (Na) reabsorbing renal epithelial cells contain amiloride sensitive Na channels which are sequestered to the microvillar domain of the apical membrane. Epithelial Na channels (ENaCs) mediate entry of Na from the apical fluid during the first stage of electrogenic Na transport. Localization of ENaC to the apical membrane domain is essential for the vectoral transport of Na across these epithelia. Recent molecular characterization of ENaC affords the opportunity to identify associated proteins involved in establishing and maintaining ENaC within the apical membrane domain, such as peripheral membrane and membrane cytoskeletal proteins. Our long term goal is to understand the molecular interactions between ENaC and associated proteins which are involved in establishing and maintaining ENaC within the microvillar domain of the apical membrane of renal epithelia and how these interactions are regulated under both normal and pathophysiological conditions. In this application we propose to focus on interactions between ENaC and Apx (Apical protein Xenopus), a novel ENaC associated protein originally cloned from Xenopus. Recently mRNA for a human homolog of Apx has been identified in kidney. Based upon data presented in the Preliminary studies, we hypothesize that Apx interacts with ENaC and elements of the spectrin-based cytoskeleton and functions in sequestering and/or stabilizing ENaC within the microvillar domain of the apical membrane of Na reabsorbing renal epithelia. There are three Specific Aims: 1) To test the hypothesis that Apx interacts with ENaC and elements of the spectrin-based apical membrane cytoskeleton in Na+ reabsorbing renal epithelial cells. 2) To test the hypothesis that Apx sequester and/or stabilizes ENaC within the microvillar domain of the cell surface. 3) To test the hypothesis that an Apx homolog is expressed in Na reabsorbing renal epithelial of the mammalian kidney and that this homolog is associated with mammalian ENaC. It is expected that at the conclusion of the proposed study we will have determined the role of Apx and its mammalian homolog in sequestering and/or stabilizing ENaC within the microvillar domain of the apical membrane of Na reabsorbing renal epithelia. In addition, the results will enhance our understanding of the role ENaC associated proteins play in the regulation of this important ion channel. Furthermore, it is expected that the results obtained will facilitate our understanding of the organization of the apical membrane cytoskeleton and associated proteins in renal epithelial cells under normal physiologic as well as pathophysiologic conditions such as ischemia and polycystic kidney disease.