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性刺激物，对心血管和肾脏稳态产生不利影响。它在心力衰竭、慢性肾病和某些形式的高血压中升高。虽然体内醛固酮的产生长期以来一直被认为是由Ang I和钾调节的，但K通道调节对Ang II生理作用的贡献，虽然是假设的，但仍未得到证实。最近一代的TASK-1、TASK-3和TASK-1/TASK-3敲除小鼠提供了令人兴奋的可能性，以确定TASK通道调节对体内醛固酮产生的生理控制的功能重要性。我们的假设是TASK亚单位有助于背景钾电流和Ang II对膜电位的控制，以及醛固酮分泌肾小球肾上腺带（ZG）细胞的酸化，我们在体外进行了测试。此外，这些通道在调节体内醛固酮生成和盐/水平衡中起重要作用的假设是在基础条件下以及激素和代谢挑战（即AngII输注、Na负荷和剥夺）过程中确定的。我们追求以下具体目标：目标1：使用qRT-PCR、原位杂交和免疫组织化学，生成并验证新的常规和条件TASK通道亚基敲除小鼠系；目的2：确定对照小鼠和TASK通道敲除小鼠ZG细胞的膜特性，表征背景K通道电流及其由AngII、细胞外K和浴液pH调节，并评估这些通道在设置膜电压和支持ZG细胞兴奋性方面的作用；目的3：评估TASK通道表达对控制体内醛固酮产生的重要性，在对照组和TASK通道敲除小鼠中确定：稳定状态的醛固酮分泌对饮食控制盐平衡引起的RAAS抑制的反应，以及体内外源性AngII或酸负荷的醛固酮分泌反应。该建议的优势在于结合使用分子和细胞生物学，电生理学和全动物实验。至少，我们的努力将阐明TASK通道在醛固酮产生中的作用。最理想的是，我们的工作将为心力衰竭、慢性肾病和顽固性高血压患者的治疗确定一个新的靶点。

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.