Regulation of the epithelial Na+ channel by Ras and Sgk

描述（由申请人提供）：适当控制Na+依赖性液体 远端肾单位的重吸收对血压稳态是至关重要的。 最重要的系统调节剂醛固酮的细胞机制 钠离子的任意重吸收，知之甚少。远景目标 这是一个新任命的调查员的第一个建议（修订）是他们的 澄清。这项研究与许多器官系统的生理学有关 包括泌尿、心血管和呼吸系统，以及 高血压和其他与体液有关的疾病的病理生理学 不平衡阿米洛利敏感性上皮Na+通道（ENaC）的活性 限制Na+重吸收。醛固酮影响基因表达， 增加ENaC的活性。然而，编码ENaC的基因不是 最初是自己诱导的。因此，醛固酮增加了 将信息传递给ENaC的中间信号蛋白。基因 编码醛固酮诱导的转录物传统上很难 确认身份。利用现代技术， 信号转导，最近已经确定：血清-和 糖皮质激素调节激酶（Sgk）和小G蛋白K-RasA （K-rasA）。这些转录物的诱导是醛固酮在细胞内的主要作用。 上皮细胞，并转化为Sgk和K-RasA蛋白水平的增加。 这些蛋白与Na+重吸收和ENaC的关系尚不清楚 明白当前提案的具体目标将直接决定 醛固酮诱导的Sgk和K-RasA信号在 调节上皮细胞中ENaC活性。我推测醛固酮激活的 KRasA和Sgk通过信号转导会聚使ENaC稳定在 开放状态和增加管腔膜中ENaC的数量。的影响 将在ENaC的A6细胞模型中研究Sgk和K-RasA信号传导。 远端肾单位上皮细胞使用一个全面的和新的实验方法。 蛋白质成分水平和活性的生化评估 Sgk和K-RasA信号通路对醛固酮的反应将是一个 终端测量另一个是ENaC的电生理测量 活性、动力学和数量。特定分子和 Sgk和K-RasA信号转导的药理学调节剂， 过程将被用来以系统的方式描绘细胞 醛固酮增加Na+重吸收的机制 上皮细胞

DESCRIPTION (provided by applicant): Proper control of Na+-dependent fluid reabsorption at the distal nephron is critical to blood pressure homeostasis. The cellular mechanisms of aldosterone, the most important systemic modulator of discretionarily Na+ reabsorption, are poorly understood. The long-term goal of this (revised) first proposal of a newly appointed investigator is their elucidation. This research is relevant to the physiology of many organ systems including the urinary, cardiovascular and respiratory systems, as well as to the pathophysiology of hypertension and other diseases associated with fluid imbalance. Activity of the amiloride-sensitive, epithelial Na+ channel (ENaC) is limiting for Na+ reabsorption. Aldosterone affects gene expression and then increases the activity of ENaC. However, the genes encoding ENaC are not themselves initially induced. Thus, aldosterone increases expression of intermediary signaling proteins that transduce information to ENaC. Genes encoding aldosterone-induced transcripts traditionally have been difficult to identify. With modem technology, two aldosterone-induced transcripts, relevant to signal transduction, recently have been identified: serum- and glucocorticoid-regulated kinase (Sgk), and the small G protein, K-RasA (K-rasA). Induction of these transcripts is a primary action of aldosterone in epithelia, and translates into an increase in Sgk and K-RasA protein levels. The relation of these proteins to Na+ reabsorption and ENaC remain poorly understood. The Specific Aims of the current proposal will directly determine the potential novel roles of aldosterone-induced Sgk and K-RasA signaling in regulating ENaC activity in epithelia. I hypothesize that aldosterone-activated KRasA and Sgk through signal transduction convergence stabilize ENaC in the open state and increase number of ENaC in the luminal membrane. The effect of Sgk and K-RasA signaling on ENaC will be investigated in the A6 cell model of distal nephron epithelia using a comprehensive and novel experimental approach. Biochemical assessment of the levels and activities of the protein constituents of Sgk and K-RasA signaling pathways in response to aldosterone will be one end-measurement. The other will be electrophysiological measurement of ENaC activity, kinetics and number. The effects of specific molecular and pharmacological modulators of Sgk and K-RasA signal transduction on these processes will be used to delineate in a systematic manner the cellular mechanisms of aldosterone action to increase Na+ reabsorption in native epithelia.