Mechanism of Renal Acid- Base Homeostasis

描述（由申请人提供）：钾和酸碱平衡异常通常是危重患者的严重临床挑战。肾脏通过调节涉及K+特异性阳离子通道和ATP驱动的阳离子泵活性的重吸收和分泌过程，在维持全身钾平衡中起决定性作用。两种H ~+，K ~+-ATP酶定位于肾脏，参与K ~+吸收和尿酸化。本实验室先前的研究表明，结肠α-H+，K+-ATP酶（HK α 2）亚基在慢性低钾血症中上调。另一些则通过代谢性酸中毒、代谢性酸中毒、盐消耗和发育中的肾脏来调节。这种调节反应主要局限于外髓集合管和内髓集合管。该领域的一个挑战是协调在体外观察到的功能特性与表达功能的分歧。我们实验室在上一个资助周期提出的三个战略观察包括：1）HK α 2在体内与β 1-Na+，K+-ATP酶亚基的结合保护复合物免于降解并促进易位至质膜，2）HK α 2的羧基末端的区段对于HK α 2功能是必需的，和3）HK α 2/β 1复合物与四跨膜蛋白CD 63缔合。因此，在接下来的五年中，我们将研究：1）HK α 2和其他X+，K+-ATP酶羧基末端特定区域的生物学作用，以及2）与CD 63相关的生理学作用。因此，本奖项的下一阶段将讨论三个具体目标：目标1将描述我们观察到的HK α 2和CD 63羧基末端之间独特关联的生理意义。目的二是确定和表征HK α 2的羧基端在结肠H+，K+-ATP酶的生物活性中的特定作用。目的3将研究HK α 2/β 1/CD 63复合物向质膜的运输和易位。本实验室研究的总体目标是阐明肾脏调节钾和酸碱平衡反应的分子基础。这项研究将推进钾和酸碱平衡的基本机制在健康和常见的临床情况下与紊乱的电解质平衡模型的知识。

DESCRIPTION (provided by applicant): Abnormalities in potassium and acid-base balance are often serious clinical challenges in critically ill patients. The kidney plays a decisive role in maintaining total body potassium balance through regulation of reabsorptive and secretory processes involving activity of K+-specific cation channels and ATP-driven cation pumps. Two H+, K+-ATPases have been localized to kidney and have been shown to participate in K+ absorption and urinary acidification. Previous studies in our laboratory have shown that the colonic alpha-H+, K+-ATPase (HKalpha2) subunit is up regulated by chronic hypokalemia. Others have shown up regulation by metabolic acidosis, metabolic alkalosis, salt depletion, and in the developing kidney. This regulatory response is confined primarily to the outer and inner medullary-collecting duct. A challenge in the field has been to reconcile the divergence in functional properties observed in vitro with expressed function. Three strategic observations during the last funding cycle made by our laboratory include: 1) that the association of HKalpha2 in vivo with the beta1-Na+, K+-ATPase subunit protects the complex from degradation and fosters translocation to the plasma membrane, 2) that a segment of the carboxy terminal of HKalpha2 is essential for HKalpha2 function, and 3) that the HKalpha2/beta1 complex associates with the tetraspanin protein CD63. Therefore, over the next five years we will investigate: 1) the biologic role of specific regions of the carboxy-terminus of HKalpha2 and other X+, K+-ATPases, and 2) the physiological role of the association with CD63. Accordingly, three Specific Aims will be addressed in the next period of this award: Aim 1 will characterize the physiological significance of our observation of unique association between the carboxy-terminus of HKalpha2 and CD63. Aim 2 will identify and characterize the specific role of the carboxy-terminus of HKalpha2 in the biological activity of the colonic H+, K+-ATPase. Aim 3 will investigate trafficking and translocation of the HKalpha2/beta1/CD63 complex to the plasma membrane. The overall objective of research by this laboratory is to clarify the molecular basis of responses by the kidney to regulate potassium and acid-base homeostasis. This research will advance knowledge of fundamental mechanisms of potassium and acid base balance in health and models of common clinical circumstances associated with deranged electrolyte balance.