Regulation of the epithelial Na+ channel by Ras and Sgk

描述(申请人提供)：适当控制依赖钠的液体 远端肾单位的重吸收对血压稳态至关重要。 最重要的系统调节剂--醛固酮的细胞机制 对钠的随意重吸收，人们知之甚少。长期目标 在这份(修订后的)新任命的调查员的第一份提案中，他们 澄清。这项研究与许多器官系统的生理学有关。 包括泌尿系统、心血管系统和呼吸系统，以及 高血压和其他与液体有关的疾病的病理生理学 不平衡。阿米洛利敏感的上皮钠通道(ENaC)的活性 对钠的重吸收是有限制的。醛固酮影响基因表达，然后 增加ENaC的活性。然而，编码ENaC的基因并不是 最初是由他们自己诱导的。因此，醛固酮增加血管紧张素转换酶的表达 将信息传递给ENaC的中间信号蛋白。基因 对醛固酮诱导的转录本进行编码传统上很难 辨认身份。利用现代技术，两个醛固酮诱导的转录本，相关 信号转导，最近被发现：血清和 糖皮质激素调节蛋白(SGK)和小G蛋白K-rasa (K-Rasa)。这些转录本的诱导是醛固酮在体内的主要作用 并转化为SGK和K-RASA蛋白水平的增加。 这些蛋白质与钠重吸收和ENaC的关系仍然很差 明白了。当前提案的具体目标将直接决定 醛固酮诱导的SGK和K-RASA信号转导通路的潜在新作用 调节上皮细胞的ENaC活性。我推测是由醛固酮激活的 Krasa和SGK通过信号转导汇聚稳定ENaC 开放状态，增加管腔内ENaC的数量。的影响 将在A6细胞模型中研究ENaC上的SGK和K-RASA信号。 使用一种全面而新颖的实验方法研究远端肾单位上皮细胞。 蛋白质组分水平和活性的生化评价 SGK和K-RASA信号通路对醛固酮的反应将是一个 结束测量。另一种是ENaC的电生理测量 活性、动力学和数量。特定的分子和蛋白质的作用 SGK和K-RASA信号转导的药理调节剂 过程将被用来系统地描绘细胞 醛固酮促进体内钠重吸收的作用机制 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.