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通道被隔离在微绒毛域 顶膜。上皮钠离子通道 (ENaCs) 介导钠离子的进入 来自电生 Na 第一阶段期间的顶端液 运输。 ENaC 定位于顶膜域 对于 Na 穿过这些上皮细胞的矢量运输至关重要。 ENaC 的最新分子表征提供了机会 识别参与建立和维持的相关蛋白质 ENaC 位于顶膜区域，例如外周膜和 膜细胞骨架蛋白。我们的长期目标是了解 ENaC 和相关蛋白之间的分子相互作用 参与微别墅内 ENaC 的建立和维持 肾上皮细胞顶膜的结构域以及这些结构如何 相互作用在正常和病理生理条件下受到调节 条件。在此应用程序中，我们建议重点关注交互 ENaC 和 Apx（非洲爪蟾顶端蛋白）之间的一种新的 ENaC 相关蛋白 最初从非洲爪蟾中克隆的蛋白质。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 以及基于血影蛋白的细胞骨架的元素和功能 在微绒毛域内隔离和/或稳定 ENaC Na重吸收肾上皮的顶膜。有三个 具体目标：1) 检验 Apx 与 ENaC 相互作用的假设 以及 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）检验Apx的假设 螯合和/或稳定 ENaC 在微绒毛域内 细胞表面。 3) 检验表达 Apx 同源物的假设 在哺乳动物肾脏的Na重吸收肾上皮中，这 同源物与哺乳动物 ENaC 相关。预计在 拟议研究的结论我们将确定 Apx 的作用 及其哺乳动物同源物在内部隔离和/或稳定 ENaC Na重吸收肾顶膜微绒毛区 上皮细胞。此外，研究结果将加深我们对 ENaC 相关蛋白在此调节中的作用 重要的离子通道。此外，预计结果 所获得的信息将有助于我们对组织的了解 肾上皮顶膜细胞骨架及相关蛋白 正常生理和病理生理条件下的细胞 例如缺血和多囊肾病。

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.