Cellular Mechanisms of Mineralcorticoid Action

描述(由申请人提供)：维持细胞外液容量的动态平衡对于血流动力学的稳定是必不可少的，肾脏钠处理的异常与心血管疾病和高血压有关。钠排泄的最终调节发生在远端肾单位，通过阿米洛利敏感的上皮钠通道(ENaC)进行传导转运。ENAC在上皮细胞顶膜的表达和活性是Na+重吸收的限速步骤，不仅在肾脏集合管，而且在呼吸道上皮和结肠中也是如此。醛固酮是ENaC在反应性上皮细胞表达和活性的主要调节因子。研究旨在探讨醛固酮对ENaC的调节机制。在前一个授权期的工作已经确定，醛固酮刺激BetaENaC的翻译后甲基化，从而改变通道门控。现在建议进行研究，以检查这一规定的位置和机制，并可能定义ENaC中的门控位置。我们已经证明ENAC似乎至少部分地定位于称为脂筏的膜的特殊区域，并且这种定位受醛固酮的调节。ENaC的RAFT结合是一个新的发现，可能对ENaC的运输、顶膜表达以及与调节蛋白的结合具有重要意义。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.