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Na通道，其被隔离到微绒毛结构域， 顶膜上皮Na通道（ENaCs）介导Na的进入 在生电钠的第一阶段， 运输ENaC在顶膜结构域的定位是 对于Na穿过这些上皮的载体运输是必需的。 最近ENaC的分子表征提供了机会， 鉴定参与建立和维持 ENaC位于顶膜结构域，如外周膜， 膜细胞骨架蛋白我们的长期目标是了解 ENaC和相关蛋白质之间的分子相互作用， 参与微绒毛内ENaC的建立和维持 肾上皮细胞顶膜的结构域，以及这些结构域是如何 在正常和病理生理条件下， 条件在本申请中，我们建议将重点放在相互作用上 在ENaC和Apx（非洲爪蟾的顶端蛋白）之间，一种新的ENaC相关蛋白， 最初从非洲爪蟾克隆的蛋白质。最近，人类的mRNA 已在肾脏中鉴定出Apx的同源物。根据提供的数据 在初步研究中，我们假设Apx与ENaC相互作用 和血影蛋白为基础的细胞骨架的元素， 将ENaC隔离和/或稳定在微绒毛结构域内， 钠重吸收肾上皮细胞的顶膜。有三 具体目的：1）检验Apx与ENaC相互作用的假设 和Na+中基于血影蛋白的顶膜细胞骨架的元素 重吸收肾上皮细胞。2)为了验证Apx 将ENaC隔离和/或稳定在微绒毛结构域内， 细胞表面3)为了检验Apx同源物表达于 在哺乳动物肾脏的Na重吸收肾上皮细胞中， 同源物与哺乳动物ENaC相关。预计在 在拟议研究的结论中，我们将确定Apx的作用 及其哺乳动物同系物在螯合和/或稳定ENaC中的作用 钠重吸收肾顶膜微绒毛区 上皮细胞此外，研究结果将增进我们对 ENaC相关蛋白在调节这一过程中的作用 重要的离子通道此外，预计结果 这将有助于我们了解组织的情况。 肾上皮细胞顶膜骨架及其相关蛋白 正常生理和病理生理条件下的细胞 例如局部缺血和多囊肾疾病。

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.