Calicum, MARCKS, and PIP2 regulation of ENaC

描述（由申请人提供）：高血压是一个主要的公共卫生问题，因为它是许多其他疾病的重要危险因素，包括充血性心力衰竭、中风和终末期肾病。上皮钠通道（ENaC）的组成性激活可导致严重高血压，而ENaC的轻微刺激可能导致原发性高血压。因此，了解ENaC的调控对了解高血压病因具有重要意义。我们的实验室是第一个证明ENaC活性需要磷脂酰肌醇二磷酸（PIP2）结合到ENaC亚基的氨基末端结构域的实验室之一。我们使用远端肾元钠转运的组织培养模型，我们发现ENaC的PIP2依赖性调节是由一种接头蛋白介导的，肉豆蔻酰基化富丙氨酸C激酶底物（MARCKS），它结合PIP2并增加ENaC附近PIP2的局部浓度，从而激活ENaC。MARCKS的肉豆蔻酰化氨基末端结构域和基本效应结构域都参与了其在根尖质膜上的功能。MARCKS的功能可以通过翻译后修饰、与钙/钙调蛋白的结合和蛋白质水解来调节，因此MARCKS的调节对ENaC的调节也很重要。该项目的目的是展示marks如何在体内调节ENaC，并确定在肾上皮细胞顶膜调节marks活性的分子机制。

DESCRIPTION (provided by applicant): Hypertension is a major public health concern because it is an important risk factor for many other diseases including congestive heart failure, stroke, and end-stage renal disease. The constitutive activation of epithelial sodium channels (ENaC) leads to severe hypertension, while subtle stimulation of ENaC may contribute to essential hypertension. Therefore, understanding the regulation of ENaC is important to understand the etiology of hypertension. Our laboratory was among the first to show that ENaC activity requires binding of phosphatidylinositol bis-phosphate (PIP2) to the amino terminal domain of ENaC subunits. We used a tissue culture model of distal nephron sodium transport and we showed that the PIP2 dependent regulation of ENaC is mediated by an adaptor protein, myristoylated alanine-rich C kinase substrate (MARCKS), that binds PIP2 and increases the local concentration of PIP2 near ENaC and, thereby, activates ENaC. The myristoylated amino terminal domain and the basic effector domain of MARCKS both contribute to its function at the apical plasma membrane. The function of MARCKS can be regulated by posttranslational modifications, association with calcium/calmodulin, and proteolysis so that regulation of MARCKS is also important for regulating ENaC. The aims of this project are to show how MARCKS regulates ENaC in vivo and identify the molecular mechanisms that regulate MARCKS activity at the apical membrane of renal epithelial cells.