Epithelial Sodium Channel Trafficking

描述(由申请人提供)： 上皮性Na+通道(ENaC)形成了肾脏、肺和其他上皮细胞吸收Na+的途径。ENAC受到严格调控，以维持Na+稳态和控制血压。这一规定中的缺陷破坏了微妙的平衡，并导致了疾病。重要的是，许多已确定的遗传性高血压是由于ENaC调节的缺陷造成的。ENaC调节的缺陷也可能与囊性纤维化的发病有关。因此，我们的长期目标是了解调节ENaC的机制，以此作为开发更有针对性的治疗这些疾病的先决条件。最新发现的趋同使人们将注意力集中在泛素化作为管制ENaC贩运的关键机制上。通过减少ENaC表面的表达，泛素化减少了上皮细胞对Na+的吸收，这是面对Na+/容量过剩时的一种重要的适应性反应。在这项提案中，我们将研究泛素化控制ENaC贩运的分子机制。这项工作利用了我们以前的发现，即E3泛素连接酶Nedd4-2催化ENaC泛素化，并在运输途径的两个不同步骤(内吞和溶酶体降解)减少ENaC在细胞表面的表达。重要的是，这一通路的缺陷是导致利德尔综合征的原因。此外，Nedd4-2是醛固酮和加压素调节ENaC的关键汇聚点。尽管泛素化在调节上皮细胞Na+吸收中起着至关重要的作用，但我们的认识还存在着重要的空白。这项建议的总体目标是了解泛素化调节ENaC的分子机制，从而调节上皮细胞的Na+转运。我们将研究E3泛素连接酶调节ENaC转运的机制，研究ENaC在内体中的分选机制，并研究赖氨酸乙酰化在ENaC转运中的作用。通过测试新的假设和使用创新的方法，这项工作将对泛素化调节ENaC表面表达的机制产生新的见解，从而调节上皮细胞的Na+运输和Na+稳态。这可能对我们理解和治疗包括高血压和囊性纤维化在内的疾病有重要的意义。

DESCRIPTION (provided by applicant): The epithelial Na+ channel (ENaC) forms a pathway for Na+ absorption in the kidney, lung, and other epithelia. ENaC is tightly regulated in order to maintain Na+ homeostasis and to control blood pressure. Defects in this regulation upset the delicate balance and cause disease. Importantly, many of the identified inherited forms of hypertension result from defects in ENaC regulation. A defect in ENaC regulation may also contribute to the pathogenesis of cystic fibrosis. Thus, our long term goal is to understand the mechanisms that regulate ENaC as a prerequisite for the development of more targeted treatments for these diseases. A convergence of recent discoveries has focused attention on ubiquitination as a critical mechanism that regulates ENaC trafficking. By reducing ENaC surface expression, ubiquitination decreases epithelial Na+ absorption, which is an important adaptive response in the face of Na+/volume excess. In this proposal, we will investigate the molecular mechanisms by which ubiquitination controls ENaC trafficking. This work capitalizes on our previous discoveries that the E3 ubiquitin ligase Nedd4-2 catalyzes ENaC ubiquitination and reduces ENaC expression at the cell surface at two distinct steps in the trafficking pathway (endocytosis and lysosomal degradation). Importantly, defects in this pathway are responsible for Liddle's syndrome. Moreover, Nedd4-2 is a critical convergence point by which aldosterone and vasopressin regulate ENaC. Although it is clear that ubiquitination plays a critically important role in the regulation of epithelial Na+ absorption, there are important gaps in our knowledge. The overall goal of this proposal is to understand the molecular mechanisms by which ubiquitination regulates ENaC, and hence, epithelial Na+ transport. We will investigate mechanisms by which E3 ubiquitin ligases regulate ENaC trafficking, investigate mechanisms that regulate ENaC sorting in endosomes, and investigate the role of lysine acetylation in ENaC trafficking. By testing novel hypotheses and using innovative approaches, this work will generate new insights into mechanisms by which ubiquitination regulates ENaC surface expression, and hence, epithelial Na+ transport and Na+ homeostasis. This may have important implications for our understanding and treatment of diseases including hypertension and cystic fibrosis.