Regulation of ENaC Trafficking

描述(申请人提供)：上皮性钠通道(ENaC)形成了肾脏、肺和其他上皮细胞吸收钠的途径。为了维持Na/容量平衡和控制血压，ENaC受到严格的调节，以应对Na/容量耗竭和Na/容量过剩的情况。然而，这一调节的缺陷导致了几乎所有已知的遗传性高血压，并促成了囊性纤维化的发病机制。这项研究的总体假设是，控制ENaC运输的机制对调节上皮钠转运至关重要。我们提出了三个具体目标来检验这一假设。1.我们以前的工作表明，Nedd4-2在ENaC表面表达的调节中起关键作用；这一调节的缺陷导致了利德尔综合征，一种遗传性高血压。在这个目标中，我们将使用新的方法来研究Ned4-2调节ENaC表面表达的机制。2.最近的工作表明，ENaC是通过对通道的蛋白水解性切割来激活的。令人惊讶的是，我们发现利德尔综合征突变选择性地增加了裂解的ENaC通道的表面表达。这为利德尔综合征突变可能改变ENaC门控提供了一种新的机制。在这个目标中，我们将探索潜在的分子机制。3.将ENaC亚单位组装成复合体是有效运输到细胞表面的关键步骤。在初步数据的基础上，我们将研究辅助伴侣E3泛素连接酶CHIP在生物合成途径中调节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先前的数据，并将对调控ENaC表面表达的机制产生新的见解，从而调节上皮钠转运和钠稳态。这对于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. 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.