Calicum, MARCKS, and PIP2 regulation of ENaC

摘要 高血压是一个主要的公共卫生问题，因为它是一个重要的危险因素， 许多其他疾病，包括充血性心力衰竭、中风和终末期肾病， 疾病上皮钠通道（ENaC）的组成性激活导致 严重的高血压，而微妙的刺激ENaC可能有助于基本的 高血压因此，了解ENaC的调节对于 了解高血压的病因。我们的实验室是第一批 ENaC活性需要磷脂酰肌醇二磷酸（PIP 2）结合到 ENaC亚基的氨基末端结构域。我们使用了一个组织培养模型， 肾单位钠转运，我们发现PIP 2依赖性调节ENaC 是由一个衔接蛋白，豆蔻酰丙氨酸丰富的C激酶底物介导的 （MARCKS），其结合PIP 2并增加ENaC附近PIP 2的局部浓度 从而激活ENaC。豆蔻酰化的氨基末端结构域和碱性 MARCKS的效应子结构域都有助于其在顶端血浆中的功能 膜的MARCKS的功能可以通过翻译后调节 修饰、与钙/钙调蛋白的结合以及蛋白水解， MARCKS对调节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 调节肾上皮细胞顶膜的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.