ENaC Regulation by Nedd4-2 and SGK

Nedd4-2 和 SGK 的 ENaC 法规

• 批准号: 6797888
• 负责人: Peter M Snyder
• 金额: $ 25.73万
• 依托单位: UNIVERSITY OF IOWA
• 依托单位国家: 美国
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-09-01 至 2006-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6797888
• 关键词: Xenopus oocyte; aldosterone; calcium binding protein; corticosteroid receptors; cyclic AMP; electrolyte balance; epithelium; gene mutation; hypertension; protein binding; protein kinase; protein protein interaction; protein structure function; receptor binding; receptor expression; renal tubular transport; saluresis; site directed mutagenesis; sodium channel; tissue /cell culture

DESCRIPTION (provided by applicant): The epithelial Na+ channel, ENaC, forms the pathway for Na+ absorption in the kidney collecting duct and other epithelia (1, 2). Specific ENaC mutations lead to excessive channel expression at the cell surface, resulting in a genetic form of hypertension (Liddle's syndrome). Aldosterone and other steroid hormones regulate Na+ absorption by altering the expression of ENaC at the cell surface. Thus, understanding the mechanisms that control ENaC surface expression wifi provide critical new insights into the molecular mechanisms of Na+ homeostasis, and the pathogenesis of hypertension. Previous work found that Nedd4 and Nedd4-2 reduce ENaC surface expression by targeting the channel for degradation. A defect in this pathway is responsible for Liddle's syndrome. Conversely, serum and glucocorticoid-regulated kinase (SGK), a down-stream mediator of aldosterone, increases ENaC surface expression. Our preliminary studies suggest the novel hypothesis that these two pathways are not independent, but that they converge in a common pathway to regulate Na+ absorption. The goal of this project is to test the hypothesis that SGK modulates ENaC surface expression in part through Nedd4-2 binding and phosphorylation, and to understand the mechanisms involved. In the first specific aim, we will test the hypothesis that SGK phosphorylates Nedd4-2. We will identify the specific residues that are phosphorylated, and will test whether phoshorylation alters Nedd4-2 function. In specific aim two, we will test the hypothesis that SGK binds to Nedd4-2. We will identify the sequences that mediate this interaction, and test the functional role of binding. Specific forms of hypertension are caused by defects in ENaC regulation by Nedd4 family members (Liddle's syndrome) and defects in mineralocorticoid and glucocorticoid signaling signalling (e.g. glucocorticoid-remediable aldosteronism). Thus, our work will provide a new understanding of these forms of hypertension. In addition, by elucidating the pathways and proteins responsible for blood pressure control, this work may provide important new insights into the molecular causes of essential hypertension.

描述（由申请人提供）：上皮 Na+ 通道 ENaC 形成肾集合管和其他上皮细胞中 Na+ 吸收的途径 (1, 2)。特定的 ENaC 突变导致细胞表面通道过度表达，从而导致遗传性高血压（利德尔综合征）。醛固酮和其他类固醇激素通过改变细胞表面 ENaC 的表达来调节 Na+ 的吸收。因此，了解控制 ENaC 表面表达的机制为 Na+ 稳态的分子机制和高血压的发病机制提供了重要的新见解。先前的工作发现 Nedd4 和 Nedd4-2 通过靶向降解通道来减少 ENaC 表面表达。该通路的缺陷导致了利德尔综合征。相反，血清和糖皮质激素调节激酶 (SGK)（醛固酮的下游介质）会增加 ENaC 表面表达。我们的初步研究提出了一个新的假设，即这两条途径不是独立的，而是它们汇聚在一个共同的途径中来调节 Na+ 的吸收。该项目的目标是检验 SGK 部分通过 Nedd4-2 结合和磷酸化调节 ENaC 表面表达的假设，并了解所涉及的机制。在第一个具体目标中，我们将检验 SGK 磷酸化 Nedd4-2 的假设。我们将鉴定被磷酸化的特定残基，并测试磷酸化是否会改变 Nedd4-2 功能。在具体目标二中，我们将检验 SGK 与 Nedd4-2 结合的假设。我们将鉴定介导这种相互作用的序列，并测试结合的功能作用。特定形式的高血压是由 Nedd4 家族成员的 ENaC 调节缺陷（利德尔综合征）以及盐皮质激素和糖皮质激素信号传导缺陷（例如糖皮质激素可治愈的醛固酮增多症）引起的。因此，我们的工作将为这些形式的高血压提供新的认识。此外，通过阐明负责血压控制的途径和蛋白质，这项工作可能为原发性高血压的分子原因提供重要的新见解。