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

描述（由申请人提供）：本研究的目的是确定衰老过程中多巴胺（DA）介导的尿钠排泄调节机制。DA是一种内源性利钠激素，通过抑制顶膜钠-氢交换器-3（NHE 3）和基底外侧膜钠-钾ATP酶（NKA）来调节肾脏近端小管中的盐重吸收。NHE 3和NKA的调节活性对于全身盐、水和矿物质的体内平衡至关重要，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调节是必需的。在缺乏NHERF表达的细胞中，DA不能调节NKA功能。我们证明NHERF-1与NKA、多巴胺1受体（D1受体）和PKC β相关。在DA刺激下，NHERF-1与NKA的结合减少，而与D1受体和PKC β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在丝氨酸-77的磷酸化。在此，我们提出NHERF-1的磷酸化允许其离开复合物，从而允许NKA磷酸化和内吞作用。此外，我们推测，在衰老过程中，NHERF-1 -D1 R相互作用的丧失是盐敏感性高血压的原因。我们将在两个具体目标中讨论这一假设。在目的1中，我们将比较溶剂和多巴胺处理的FBN大鼠中NHERF-1的表达和磷酸化。我们将确定NHERF-1与NKA、D1和D5受体、PKA和PKC β的相关性。在目标2中，我们将用高盐或多巴胺处理NHERF-1敲除动物，并确定NHERF-1在衰老中盐敏感性高血压中的重要性。我们预计，这些研究将提供新的见解，肾近端肾小管NHE 3和NKA的DA的调节，并提供潜在的治疗靶点，治疗与异常钠稳态老化的疾病。

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.