Cellular Mechanisms of Mineralcorticoid Action

描述（由申请人提供）：维持细胞外液容量稳态对血流动力学稳定至关重要，肾脏钠处理异常与心血管疾病和高血压有关。钠排泄的最终调控发生在远端肾元，通过阿米洛胺敏感上皮Na+通道（ENaC）的传导运输。ENaC在上皮细胞顶膜的表达和活性是限制Na+在肾集管、气道上皮和结肠重吸收的速率步骤。醛固酮是反应性上皮中ENaC表达和活性的主要调节因子。研究旨在探讨醛固酮调节ENaC的机制。之前的研究已经证实醛固酮刺激β enac的翻译后甲基化，从而改变通道门控。现在有人提议研究这种调控的位点和机制，并可能在ENaC中定义一个门控位点。我们已经证明，EnaC似乎定位，至少部分地，在称为脂筏的膜的专门区域，这种定位是由醛固酮调节的。ENaC的Raft association是一个新发现，可能对ENaC运输、根尖膜表达和与调节蛋白的关联具有重要意义。我们将研究脂质筏关联影响ENaC功能和醛固酮调节的机制。

DESCRIPTION (provided by applicant): Maintenance of extracellular fluid volume homeostasis is essential for hemodynamic stability, and abnormalities of renal sodium handling have been linked to cardiovascular disease and hypertension. Ultimate regulation of sodium excretion occurs in the distal nephron via conductive transport through amiloride sensitive epithelial Na+ channel (ENaC). ENaC expression and activity in the apical membrane of epithelial cells is the rate limiting step in Na+ reabsorption not only in the kidney collecting duct, but in airway epithelia and colon as well. Aldosterone is a major regulator of ENaC expression and activity in responsive epithelia. Studies are designed to examine the mechanism of aldosterone regulation of ENaC. Work in the previous grant period has established that aldosterone stimulates the post-translational methylation of betaENaC which alters channel gating. Studies are now proposed to examine the site and mechanism of this regulation and potentially define a gating site in ENaC. We have demonstrated that EnaC appears to be localized, in part at least, to specialized areas of membrane called lipid rafts and this localization is regulated by aldosterone. Raft association of ENaC is a new finding and could be important for ENaC trafficking, apical membrane expression and association with regulatory proteins. We will examine the mechanism by which lipid raft association affects ENaC function and aldosterone regulation.