H,K ATPase Function in Potassium Homeostasis

描述（由申请人提供）：本研究的长期目标是确定离子通道如何协调调节H， k - atp酶活性。我们确定了肾集管（CD）中的H， k - atp酶活性需要钡敏感途径（即离子通道）。我们还发现，与K限制条件相比，在K充满条件下H， K- atp酶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 - atp酶活性的运作中起着重要作用。破坏KCNQ1基因或药物阻断该K通道可抑制胃酸分泌，胃酸分泌通过胃H， K- atp酶发生。我们的初步数据证实了KCNQ1在小鼠肾CD中的表达，并受饮食中钾含量和矿化皮质激素的调节。因此，我们假设这些K通道对CD中H， K- atp酶活性的运作至关重要，并受膳食K和矿物皮质激素的调节。为此，我们提出以下具体目标：定义KCNQ1的细胞分布以及该K通道对矿物质皮质激素和膳食K含量变化的响应，正常小鼠，HKalpha1和HKalpha2无效，以及hkβ无效小鼠。2. 探讨矿化皮质激素和膳食K摄入量对正常、HKalpha1缺失、HKalpha2缺失和HKbeta缺失小鼠肾脏中KCNQ1和KCNE1-5 mRNA和蛋白表达的影响。3. 为了确定KCNQ1基因的破坏或KCNQ1通道活性的高选择性抑制剂是否会改变CD中质子的分泌以及KCNQ1调节H， k - atp酶的机制。4. 确定在CD和胃壁细胞中表达的KCNQ1通道的pH依赖性。随着这些研究的完成，我们将了解在乳糜泻中表达的KCNQ1和KCNE1-5异构体的分子特征，钾摄入量是否调节这些异构体，以及这些分子在乳糜泻腔酸化中所起的作用。即使是适度的钾消耗也会导致肾损伤和高血压。这些研究将显著澄清我们对肾脏钾稳态的理解，以及钾耗尽如何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.