Cellular Mechanisms of Mineralcorticoid Action

描述（由申请方提供）：维持细胞外液容量稳态对于血流动力学稳定至关重要，肾钠处理异常与心血管疾病和高血压相关。钠排泄的最终调节发生在远端肾单位中，通过阿米洛利敏感性上皮Na+通道（ENaC）的传导转运。上皮细胞顶膜中的ENaC表达和活性不仅在肾集合管中，而且在气道上皮和结肠中也是Na+重吸收的限速步骤。醛固酮是反应性上皮细胞中ENaC表达和活性的主要调节因子。研究旨在检查ENaC的醛固酮调节机制。 在先前的资助期间的工作已经确定，醛固酮刺激β ENaC的翻译后甲基化，从而改变通道门控。现在提出的研究，以检查该网站和机制的调节，并可能定义一个门控网站在ENaC。我们已经证明，EnaC似乎是本地化的，至少部分地，专门领域的膜称为脂筏，这种定位是调节醛固酮。ENaC的筏关联是一个新的发现，可能是重要的ENaC运输，顶膜表达和协会与调节蛋白。我们将研究脂筏联合影响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.