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H，K-ATP酶活性的调节。我们建立了钡敏感途径（即，离子通道）是肾集合管（CD）中H，K-ATP酶活性所必需的。我们还发现，当与K限制条件相比时，在K充分条件下H，K-ATP酶的活化机制之间存在根本差异。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。KCNQ 1基因的破坏或该K通道的药物阻断抑制胃酸分泌，胃酸分泌通过胃H，K-ATP酶发生。我们的初步数据表明KCNQ 1在小鼠肾脏CD中的表达及其受膳食钾含量和盐皮质激素的调节。因此，我们假设这些钾通道是必不可少的H，K-ATP酶活性在CD的操作，并通过饮食钾和盐皮质激素调节。因此，我们提出以下具体目标：1.确定KCNQ 1的细胞分布以及该K通道对盐皮质激素和饮食K含量正常、HK α 1和HK α 2缺失以及HK β缺失小鼠的变化的反应。2.确定盐皮质激素和膳食钾摄入量对正常、HK α 1和HK α 2缺失以及HK β缺失小鼠肾脏中KCNQ 1和KCNE 1 -5的稳态mRNA和蛋白表达的影响。3.确定KCNQ 1基因的破坏或KCNQ 1通道活性的高选择性抑制剂是否改变CD中的质子分泌以及KCNQ 1调节H，K-ATP酶的机制。4.确定CD和胃壁细胞中表达的KCNQ 1通道的pH依赖性。随着这些研究的完成，我们将知道在CD中表达的KCNQ 1和KCNE 1 -5亚型的分子身份，如果K摄入调节这些亚型，以及这些分子在CD中的管腔酸化中发挥的作用。即使是适度的钾缺乏也会导致肾损伤和高血压。这些研究将显著阐明我们对肾脏钾稳态的理解，并可能阐明钾耗竭如何加重肾脏和心血管疾病。

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.