Mechanism of Mechanoreceptor Inhibition by Aldosterone

描述（由申请人提供）：我实验室的长期目标是了解机械转导的分子基础。这包括1)鉴定感觉神经元和肌肉细胞中机械敏感离子通道复合物的成分，2)通过物理和激素因素调节机械敏感通道的表达，3)参与心血管病理生理（自主神经功能障碍，高血压）。目前的提案将解决一个高度新颖的研究领域：醛固酮调节机械敏感离子通道的表达和功能。高血压和慢性心力衰竭的特点是循环醛固酮升高。已知醛固酮抑制压力感受器功能，这可能导致与这些疾病相关的心律失常。醛固酮抑制自主神经系统压力反射控制的分子机制尚不清楚。这一假说的基础是醛固酮激活MAPK信号通路，通过抑制ENaC蛋白的转录和降解，降低压力感受器神经元中机械敏感通道的表达，从而导致压力感受器功能障碍。这是一个新颖的假设。本研究的目的是确定1)醛固酮是否抑制DEG/ENaC转录物表达和机械门控钙瞬态，2)MAPK信号级联的激活是否抑制ENaC表达和机械门控钙瞬态，以及3)ENaC蛋白是培养感觉神经元机械感觉功能所必需的。我们将利用实时RT-PCR和免疫荧光检测醛固酮和MAPK通路对培养感觉神经元ENaC表达的影响。我们将使用2种方法来评估培养的感觉神经元的机械感觉功能。ENaC蛋白在机械转导中的重要性将通过干扰RNA和显性阴性亚型的过表达来确定。本研究结果可能有助于确定醛固酮抑制压力受体的分子机制，并为高血压和慢性心力衰竭的自主神经功能障碍机制提供更好的理解。

DESCRIPTION (provided by applicant): The long term objective of my lab is to understand the molecular basis of mechanotransduction. This includes the 1) identification of components of mechanosensitive ion channel complexes in sensory neurons and muscle cells, 2) regulation of mechanosensitive channel expression by physical and hormonal factors and 3) involvement in cardiovascular pathophysiology (autonomic dysfunction, hypertension). The current proposal will address a highly novel area of research: aldosterone regulation of mechanosensitive ion channel expression and function. Hypertension and chronic heart failure are characterized by elevations in circulating aldosterone. Aldosterone is known to inhibit baroreceptor function, which may contribute to cardiac arrhythmias frequently associated with these diseases. The molecular mechanism of aldosterone suppression of baroreflex control of the autonomic nervous system is unclear. The hypothesis underlying this proposal is that aldosterone activation of the MAPK signaling pathway, decreases the expression of mechanosensitive channels in baroreceptor neurons by inhibiting transcription and augmenting degradation of ENaC proteins, thus causing baroreceptor dysfunction. This is a novel hypothesis. The goals of this proposal are to determine if 1) aldosterone inhibits DEG/ENaC transcript expression and mechanically gated calcium transients, 2) activation of the MAPK signaling cascade inhibits ENaC expression and mechanically gated calcium transients, and 3) ENaC proteins are required for mechanosensory function in cultured sensory neurons. We will use real time RT-PCR and immunofluorescence to determine the role of aldosterone and MAPK pathway on ENaC expression in cultured sensory neurons. We will use 2 assays to assess mechanosensory function in cultured sensory neurons. The importance of ENaC proteins in mechanotransduction will be determined using interference RNA and overexpression of dominant-negative isoforms. The results from this proposal may help define the molecular mechanism of baroreceptor inhibition by aldosterone and provide a better understanding of the mechanism of autonomic dysfunction in hypertension and chronic heart failure.