Calicum, MARCKS, and PIP2 regulation of ENaC

摘要 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，包括充血性心力衰竭、中风和终末期肾脏 疾病。上皮性钠通道(ENaC)的结构性激活导致 严重高血压，而ENaC的轻微刺激可能有助于 高血压。因此，了解ENaC的监管对于 了解高血压的病因。我们的实验室是最早展示 ENaC的活性需要磷脂酰肌醇二磷酸(PIP2)与 ENaC亚基的氨基末端结构域。我们使用了远端的组织培养模型 肾单位钠转运和PIP2对ENaC的依赖调节 是由一种接头蛋白，肉豆蔻酰化富含丙氨酸的C激酶底物介导的 (Marcks)，这结合了PIP2并增加了ENaC附近PIP2的局部浓度 从而激活ENaC。肉豆蔻酰化氨基末端结构域及其碱基 Marcks的效应域在顶端血浆中都对其功能有贡献 薄膜。Marcks的功能可以通过翻译后调整来实现 修饰，与钙/钙调蛋白结合，以及蛋白降解，从而调节 Marcks对于监管ENaC也很重要。这个项目的目的是展示 Marcks如何在体内调节ENaC并确定其分子机制 调节肾上皮细胞顶膜MARCKS活性。

Abstract 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.