CELLULAR MECHANISMS OF MINERALOCORTICOID ACTION

描述(改编自申请人摘要)：维护 细胞外液容量动态平衡对血流动力学至关重要 稳定性和肾脏钠处理的异常与 心血管疾病和高血压。钠的终极管制 肾脏的排泄发生在远端肾单位，并受 盐皮质激素醛固酮。这项研究的长期目标是 了解醛固酮调节钠的细胞机制 重吸收。醛固酮作用的最初生理事件是 根尖膜通透性增加，因数量和数量增加 传导钠通道开放的概率。这项研究建议 研究这种通道激活背后的生化机制。 已知醛固酮可刺激蛋白质的羧甲基化，但 具体的选址还存在争议。这项研究将对醛固酮进行表征 钠通道特定亚基的依赖羧甲基化和 采用体外缺失和定点突变技术 确定门控的特定位置的转录肽 羧甲基化。这些实验将通过重组与之并行 对脂质双分子层的研究以验证其生理学相关性 甲基化位点。甲基转移酶调控的研究进展 将进行其特定的底物以确定其性质 醛固酮调节的步骤。由于通道子单元显然是最终的 醛固酮调节的效应物或底物，将进行研究 来确定醛固酮调节的时间进程和性质。 顶膜中的亚基组成。最后，研究将是 开始检测盐皮质激素对转录的激活 和糖皮质激素在受体转位、转运方面 激活和生化指标。

DESCRIPTION (Adapted from the Applicant's Abstract): 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 in the kidney occurs in the distal nephron and is modulated by the mineralocorticoid aldosterone. The long-term goal of this research are to understand the cellular mechanisms by which aldosterone regulates sodium reabsorption. The initial physiologic event in aldosterone action is an increase in apical membrane permeability due to an increase in number and open probability of conductive sodium channels. This study proposes to study the biochemical mechanisms underlying this channel activation. Carboxymethylation of proteins is known to be stimulated by aldosterone but the exact site is in dispute. This study will characterize the aldosterone dependent carboxymethylation of specific subunits of the sodium channel and employ the techniques of deletion and site specific mutagenesis of in vitro transcribed peptides to determine the specific site of the gating carboxymethylation. These experiments will be paralleled by reconstitution studies in lipid bilayers to validate the physiologic relevance of the methylation site. Studies of the regulation of the methyltransferase and its specific substrate will be carried out to determine the nature of the aldosterone regulated step. Since channel subunits are apparent final effector or substrate for aldosterone regulation, studies will be carried out to define the time course and nature of aldosterone regulation of subunit composition in the apical membrane. Finally, studies will be initiated to examine the transcriptional activation by mineralocorticoids and glucocorticoids both in terms of receptor translocation, transport activation and biochemical targets.