Epithelial Sodium Channel Trafficking

描述（由申请人提供）： 上皮Na+通道（ENaC）形成肾、肺和其他上皮中Na+吸收的途径。ENaC受到严格调节，以维持Na+稳态并控制血压。这种调节的缺陷破坏了微妙的平衡并引起疾病。重要的是，许多已确定的遗传性高血压是由ENaC调节缺陷引起的。ENaC调节的缺陷也可能导致囊性纤维化的发病机制。因此，我们的长期目标是了解调节ENaC的机制，作为开发针对这些疾病的更有针对性的治疗方法的先决条件。最近的发现集中注意力在泛素化作为一个重要的机制，调节ENaC贩运。通过减少ENaC表面表达，泛素化减少上皮Na+吸收，这是面对Na+/体积过量的重要适应性反应。在这个提议中，我们将调查泛素化控制ENaC运输的分子机制。这项工作利用了我们以前的发现，即E3泛素连接酶Nedd 4 -2催化ENaC泛素化，并在运输途径中的两个不同步骤（内吞作用和溶酶体降解）减少ENaC在细胞表面的表达。重要的是，这一途径的缺陷是利德尔综合征的原因。 此外，Nedd 4 -2是醛固酮和加压素调节ENaC的关键会聚点。虽然很明显，泛素化起着至关重要的作用，上皮Na+吸收的调节，有重要的差距，我们的知识。这项建议的总体目标是了解泛素化调节ENaC的分子机制，因此，上皮Na+转运。我们将研究E3泛素连接酶调节ENaC运输的机制，研究调节ENaC内体分选的机制，并研究赖氨酸乙酰化在ENaC运输中的作用。通过测试新的假设和使用创新的方法，这项工作将产生新的见解泛素化调节ENaC表面表达的机制，因此，上皮Na+转运和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具有重要意义。

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.