Two-Pore Domain Potassium Channels and Aldosterone Secretion

描述(由申请人提供)：醛固酮是一种早发性致病刺激，对心血管和肾脏的动态平衡有不利影响。它在心力衰竭、慢性肾脏疾病和某些形式的高血压中升高。虽然已知体内的醛固酮的产生受血管紧张素I和钾的调节，但钾通道调节对血管紧张素Ⅱ的生理作用的作用虽然是假设的，但仍未得到证实。最近一代TASK-1、TASK-3和TASK-1/TASK-3基因敲除小鼠为建立任务通道调节对体内醛固酮产生的生理控制的功能重要性提供了令人兴奋的可能性。我们的假设是，任务亚基参与背景K电流，Ang II和酸化对分泌醛固酮的肾上腺球状带(ZG)细胞膜电位的控制。此外，这些通道在调节体内醛固酮生成和盐/水平衡方面的重要假设是在基础条件下以及在激素和代谢挑战(即血管紧张素输入、钠负荷和剥夺)期间确定的。目的1：利用qRT-PCR、原位杂交和免疫组织化学方法建立和验证新的常规和条件性任务通道亚单位基因敲除小鼠品系：目的2：检测对照和任务通道基因敲除小鼠ZG细胞的膜特性，表征背景K通道电流及其受血管紧张素Ⅱ、细胞外钾和镀液pH的调节，并评价这些通道在设定膜电压和支持ZG细胞兴奋性方面的作用；目的：在对照和任务通道基因敲除小鼠中，评价任务通道表达对体内醛固酮产生的控制的重要性，确定：饮食调节盐平衡引起的对RAAS抑制的稳态醛固酮分泌反应，以及体内外源性血管紧张素Ⅱ或酸负荷的醛固酮分泌反应。这一提议的优势在于结合了分子和细胞生物学、电生理学和整体动物实验。至少，我们的努力将阐明任务通道在醛固酮生产中的作用。最好的情况是，我们的工作将为心力衰竭、慢性肾脏疾病和顽固性高血压患者的治疗确定一个新的目标。 项目简介：特发性原发性醛固酮增多症(IHA)出现在13%的非选择性高血压患者中，而在那些患有顽固性高血压的患者中上升到20%。结合使用细胞和体内方法，我们的研究确定TASK通道是控制醛固酮产生的关键膜蛋白，醛固酮是IHA中升高的类固醇激素。这一靶点的确定可用于为IHA患者以及心力衰竭和慢性肾脏疾病患者提供有用的治疗方法，在这些患者中，升高的醛固酮也会加速疾病的进展。

DESCRIPTION (provided by applicant): Aldosterone is an early-onset pathogenic stimulus that adversely influences cardiovascular and renal homeostasis. It is elevated in heart failure, chronic kidney disease and some forms of hypertension. Although the production of aldosterone in vivo has long been known to be regulated by Ang I and potassium, the contribution of K channel regulation to the physiological actions of Ang II, though hypothesized, has remained unproven. The recent generation of TASK-1, TASK-3, and TASK-1/TASK-3 knockout mice offers the exciting possibility to establish the functional importance of TASK channel regulation to the physiological control of aldosterone production in vivo. Our hypothesis that TASK subunits contribute to background K currents and the control of membrane potential by Ang II and acidification in the aldosterone secreting adrenal zona glomerulosa (ZG) cells is tested in vitro. Moreover, the hypothesis that these channels are important in the regulation of aldosterone production and salt/water balance in vivo is determined under basal conditions and during hormonal and metabolic challenge (i.e., AngII infusion, Na loading and deprivation). We pursue the following specific aims: Aim 1: Generate and validate novel conventional and conditional TASK channel subunit knockout mouse lines using qRT-PCR, in situ hybridization, and immunohistochemistry; Aim 2: Determine membrane properties of ZG cells in control and TASK channel knockout mice, characterizing background K channel currents and their modulation by AngII, extracellular K and bath pH, and evaluating the role of these channels in setting membrane voltage and supporting ZG cell excitability; Aim 3: Evaluate the importance of TASK channel expression to the control of aldosterone production in vivo in control and TASK channel knockout mice determining: the steady-state aldosterone secretory response to RAAS suppression caused by dietary manipulation of salt balance, and the aldosterone secretory response to the delivery of exogenous AngII or acid loading in vivo. The strength of this proposal lies in the combined use of molecular and cell biology, electrophysiology and whole animal experimentation. Minimally, our efforts will clarify the role of TASK channels in the production of aldosterone. Optimally, our work will identify a new target for the therapy of patients with heart failure, chronic kidney disease and resistant hypertension. Project Narrative: Idiopathic primary hyperaldosteronism (IHA) is present in 13% of non-selected hypertensive patients and rises to 20% among those that have resistant hypertension. Using a combination of cellular and in vivo approaches our studies identify TASK K channels as critical membrane proteins that control the production of aldosterone, the steroid hormone that is elevated in IHA. The identification of this target can be used to generate a useful therapy for patients with IHA but also for patients with heart failure and chronic kidney disease where elevated aldosterone also hastens disease progression.