Regulation of ENaC Trafficking

描述（由申请人提供）：上皮钠通道（ENaC）在肾、肺和其他上皮细胞中形成钠吸收途径。为了维持Na稳态和控制血压，ENaC受到严格调节，以应对Na/容积耗竭和Na/容积过剩的情况。然而，这种调控的缺陷导致了几乎所有已知的遗传性高血压，并有助于囊性纤维化的发病机制。所提出的研究的总体假设是，控制ENaC运输的机制对于调节上皮Na运输至关重要。我们提出三个具体目标来检验这一假设。1. 我们之前的工作表明，Nedd4-2在ENaC表面表达的调控中起关键作用；这种调节的缺陷会导致利德尔综合征，这是一种遗传性高血压。为此，我们将使用新的方法来研究Nedd4-2调节ENaC表面表达的机制。2. 最近的研究表明ENaC是通过通道的蛋白水解裂解激活的。令人惊讶的是，我们发现Liddle's综合征突变选择性地增加了cleaved ENaC通道的表面表达。这提供了一种新的机制，通过利德尔氏综合征突变可能改变ENaC门控。为此，我们将探讨潜在的分子机制。3. ENaC亚基组装成复合物是有效运输到细胞表面的关键步骤。基于初步数据，我们将研究E3泛素连接酶CHIP在生物合成途径中调控ENaC运输的机制。通过使用强大的新方法和测试新的假设，这项工作将有助于解释以前的数据，并将对调节ENaC表面表达的机制产生新的见解，从而对上皮Na转运和Na稳态产生新的见解。这对我们理解和治疗高血压和囊性纤维化等疾病具有重要意义。

DESCRIPTION (provided by applicant): The epithelial Na channel (ENaC) forms a pathway for Na absorption in the kidney, lung, and other epithelia. In order to maintain Na homeostasis and control blood pressure, ENaC is tightly regulated to respond to conditions of Na/volume depletion and Na/volume excess. However, defects in this regulation are responsible for nearly all of the known inherited forms of hypertension, and contributes to the pathogenesis of cystic fibrosis. The overall hypothesis of the proposed research is that mechanisms that control ENaC trafficking are critical for the regulation of epithelial Na transport. We propose three Specific Aims to test this hypothesis. 1. Our previous work indicates that Nedd4-2 is critical in the regulation of ENaC surface expression; defects in this regulation cause Liddle's syndrome, an inherited form of hypertension. In this aim, we will use novel approaches to investigate the mechanisms by which Nedd4-2 regulates ENaC surface expression. 2. Recent work indicates that ENaC is activated by proteolytic cleavage of the channel. Surprisingly, we found that Liddle's syndrome mutations selectively increase surface expression of cleaved ENaC channels. This provides a novel mechanism by which Liddle's syndrome mutations might alter ENaC gating. In this aim, we will pursue the underlying molecular mechanisms. 3. The assembly of ENaC subunits into a complex is a critical step in efficient trafficking to the cell surface. Based on preliminary data, we will investigate the mechanisms by which CHIP, a co-chaperone E3 ubiquitin ligase, regulates ENaC trafficking in the biosynthetic pathway. By using powerful new approaches and by testing novel hypotheses, this work will help to explain previous data and will generate new insight into mechanisms that regulate ENaC surface expression, and hence, epithelial Na transport and Na homeostasis. This has important implications for our understanding and treatment of diseases including hypertension and cystic fibrosis.