Dopamine-mediated regulation of blood pressure in aging: Role of NHERF-1

描述(申请人提供)：这项研究的目的是确定多巴胺(DA)介导的钠尿调节衰老的机制。DA是一种内源性利钠激素，通过抑制肾顶膜钠氢交换器3(NHE3)和基底膜钠钾ATPase(NKA)来调节肾脏近端小管的盐重吸收。NHE3和NKA的调节活性对体内盐分、水和矿物质的平衡至关重要，因此对血压、心脏功能、神经冲动和骨代谢的控制有重要作用。我们已经证明，钠氢调节因子(NHERF-1)的表达对于DA介导的NKA调节是必不可少的。在缺乏NHERF表达的细胞中，DA不能调节NKA的功能。我们发现NHERF-1与NKA、多巴胺1受体(D_1受体)和PKCζ有关。DA刺激后，NHERF1与NKA的结合减少，而与D1受体和PKCζ的结合增加。DA激活蛋白激酶A(PKA)和蛋白激酶C(PKC)可增加NHERF-1丝氨酸-77的磷酸化水平。在这里，我们认为NHERF-1的磷酸化允许它离开复合体，允许NKA磷酸化和内吞。此外，我们假设，在衰老过程中，NHERF-1-D1R相互作用的丧失是盐敏感型高血压的原因。我们将在两个具体目标中阐述这一假设。在目标1中，我们将比较NHERF-1在赋形剂和多巴胺处理的FBN大鼠中的表达和磷酸化。我们将确定NHERF-1与NKA、D1D5受体、PKA和PKCζ的关联。在目标2中，我们将用高盐或多巴胺处理NHERF-1基因敲除的动物，并确定NHERF-1在盐敏感型高血压衰老过程中的重要性。我们期待这些研究将为DA对肾近端小管NHE3和NKA的调节提供新的见解，并为治疗与衰老相关的钠稳态异常相关的疾病提供潜在的治疗靶点。

DESCRIPTION (provided by applicant): The objective of this study is to identify the mechanisms of dopamine (DA)-mediated regulation of natriuresis in aging. DA is an endogenous natriuretic hormone that regulates salt reabsorption in the kidney proximal tubules by inhibiting apical membrane sodium-hydrogen exchanger-3 (NHE3) and basolateral membrane sodium-potassium ATPase (NKA). Regulated activities of NHE3 and NKA is critical for total body salt, water and mineral homeostasis and therefore contributes significantly to control of blood pressure, cardiac function, nerve impulses, and bone metabolism. We have demonstrated that expression of a sodium-hydrogen regulatory factor (NHERF-1) is essential for DA- mediated regulation of NKA. In cells lacking NHERF expression, DA fails to regulate NKA function. We demonstrated that NHERF-1 associates with NKA, Dopamine 1 receptor (D1 receptors), and PKCζ. Upon stimulation with DA, NHERF-1 association with NKA decreased while association with D1 receptor and PKCζ increased. Activation of protein kinase A (PKA) and C (PKC) by DA increases NHERF-1 phosphorylation at serine-77. Herein, we propose that phosphorylation of NHERF-1 allows it to leave the complex allowing NKA phosphorylation and endocytosis. Further, we hypothesize that in aging the loss of NHERF-1 - D1R interaction is responsible for salt-sensitive hypertension. We will address this hypothesis in two specific aims. In Aim 1, we will compare NHERF-1 expression and phosphorylation in vehicle and dopamine treated FBN rats. We will determine the association of NHERF-1 to NKA, D1 and D5 receptors, PKA, and PKCζ. In Aim 2, we will treat NHERF-1 knock-out animals with high salt or dopamine and determine the importance of NHERF-1 in salt-sensitive hypertension in aging. We anticipate that these studies will provide new insights into the regulation of renal proximal tubular NHE3 and NKA by DA and provide potential therapeutic targets for treatment of disorders associated with abnormal sodium homeostasis in aging.