Mechanism of Renal Acid- Base Homeostasis

描述(由申请人提供)：钾和酸碱平衡的异常通常是危重患者面临的严重临床挑战。肾脏通过调节K+专一性阳离子通道和ATP驱动的阳离子泵的活性来调节重吸收和分泌过程，在维持全身钾平衡方面起着决定性的作用。两种H+，K+-ATPase已定位于肾脏，并被证明参与K+吸收和尿酸。我们实验室以前的研究表明，慢性低钾血症会上调结肠α-H+，K+-ATPase(HKalpha2)亚单位的表达。其他的则表现为代谢性酸中毒、代谢性碱中毒、盐分耗竭和发育中的肾脏。这种调节反应主要局限于外、内髓集合管。该领域的一个挑战是调和体外观察到的功能特性与表达功能的差异。我们实验室在上一个资助周期中进行的三个战略观察包括：1)HKalpha2在体内与Beta1-Na+，K+-ATPase亚单位的结合保护了该复合体免受降解并促进了转位到质膜；2)HKalpha2的一段羧基末端对HKalpha2的功能是必不可少的；以及3)HKalpha2/beta1复合体与Tetraspanin蛋白CD63结合。因此，在接下来的五年里，我们将研究：1)HKalpha2和其他X+，K+-ATPase羧基末端特定区域的生物学作用，以及2)与CD63相关的生理作用。因此，本奖项的下一阶段将涉及三个具体目标：目标1将表征我们观察到HKalpha2的羧基末端与CD63之间的独特联系的生理学意义。目的2鉴定和表征HKalpha2的羧基末端在结肠H+，K+-ATPase生物活性中的特殊作用。AIM 3将研究HKalpha2/beta1/CD63复合体向质膜的运输和移位。该实验室研究的总体目标是阐明肾脏调节钾和酸碱平衡的分子基础。这项研究将促进对健康中钾和酸碱平衡的基本机制的了解，以及与电解质平衡失调相关的常见临床情况的模型。

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.