H,K ATPase Function in Potassium Homeostasis

描述(申请人提供)：这项研究的长期目标是确定离子通道如何协调H，K-ATPase活性的调节。我们证实，肾集合管(CD)的这种H，K-ATPase活性需要对钡敏感的通路(即离子通道)。我们还发现，与钾限制条件相比，钾充足条件下H，K-ATPase的激活机制存在根本差异。这些观察结果表明，离子通道在H，K-ATPase活性的运行中起着基础性作用。KCNQ1基因的破坏或该K通道的药物阻断会抑制胃酸的分泌，这是通过胃H，K-ATPase发生的。我们的初步数据表明KCNQ1在小鼠肾脏CD中的表达以及它受饮食中钾含量和盐皮质激素的调节。因此，我们假设这些K通道对CD中H，K-ATPase活性的运行是必不可少的，并受膳食K和矿质皮质激素的调节。因此，我们提出了以下具体目标：1.确定KCNQ1的细胞分布以及该K通道对正常、HKalpha1缺失和HKalpha2缺失以及HKbeta缺失小鼠的糖皮质激素和饮食中K含量变化的反应。2.研究糖皮质激素和膳食K摄入量对正常、HKalpha1缺失、HKalpha2缺失和HKbeta缺失小鼠肾脏KCNQ1、KCNE1-5基因和蛋白表达的影响。3.确定KCNQ1基因的阻断或KCNQ1通道活性的高选择性抑制剂是否改变CD的质子分泌以及KCNQ1调节H，K-ATPase的机制。4.明确CD和胃壁细胞表达的KCNQ1通道的pH依赖性。随着这些研究的完成，我们将知道CD中表达的KCNQ1和KCNE1-5亚型的分子同一性，如果K摄入调节这些亚型，以及这些分子在CD管腔酸化中所起的作用。即使是轻微的钾缺乏也会导致肾脏损伤和高血压。这些研究将极大地澄清我们对肾脏钾稳态的理解，以及钾缺乏如何可能加剧肾脏和心血管疾病。

DESCRIPTION (provided by applicant): The long-range goal of this research is to determine how ion channels coordinate the regulation of H, K-ATPase activity. We established that barium-sensitive pathways (i.e., ion channels) are required for this H, K-ATPase activity in the renal collecting duct (CD). We also found that fundamental differences exist between the mechanism of activation of H, K-ATPase under K-replete conditions when compared to K- restricted conditions. These observations suggest that ion channels play a fundamental role in the operation of H, K-ATPase activity. Disruption of the KCNQ1 gene or pharmacological blockade of this K channel inhibits gastric acid secretion, which occurs via gastric H, K-ATPase. Our preliminary data demonstrate KCNQ1 expression in the mouse renal CD and its regulation by dietary K content and mineralocorticoids. Thus, we hypothesize that these K channels are essential for the operation of H, K-ATPase activity in the CD and are regulated by dietary K and mineralocorticoids. Accordingly, we propose the following Specific Aims: 1. To define the cellular distribution of KCNQ1 and the response of this K channel to changes in mineralocorticoids and dietary K content normal, HKalpha1 null and HKalpha2 null, and HKbeta null mice. 2. To determine the effect of mineralocorticoids and dietary K intake on steady-state mRNA and protein expression of KCNQ1 and KCNE1-5 in the kidney of normal, HKalpha1 null and HKalpha2 null, and HKbeta null mice. 3. To determine whether disruption of the KCNQ1 gene or highly selective inhibitors of KCNQ1 channel activity alter proton secretion in the CD and the mechanism for H, K-ATPase regulation by KCNQ1. 4. To define the pH dependence of KCNQ1 channels that are expressed in the CD and the gastric parietal cell. With the completion of these studies we will know the molecular identities of the KCNQ1 and KCNE1-5 isoforms that are expressed in the CD, if K intake regulates these isoforms, and the role these molecules play in luminal acidification in the CD. Even modest potassium depletion has been shown to cause renal injury and hypertension. These studies will significantly clarify our understanding of renal K homeostasis and potentially how K depletion exacerbates both renal and cardiovascular disease.