Trafficking and Regulation of the Epithelial Na+ Channel

描述（由申请人提供）：维修。细胞外液容量稳态对血流动力学稳定至关重要，肾脏钠处理异常与心血管疾病和高血压有关。肾脏钠排泄的最终调节发生在远端肾单位，通过阿米洛胺敏感上皮Na+通道（ENaC）进行传导运输。ENaC在上皮细胞顶膜的表达和活性是限制Na+重吸收速率的步骤，不仅在肾收集层，而且在气道上皮和结肠中也是如此。ENaC功能异常已在盐敏感性高血压、肾盐消耗和囊性纤维化的遗传形式中得到证实。本研究的长期目标是了解上皮细胞顶膜中ENaC表达的调控因素，以及激素、生理条件和其他通道（如囊性纤维化膜调节剂CFTR）调控ENaC功能的机制。ENaC功能的主要控制是通过调节Na+再吸收细胞膜上活性通道的数量来实现的。通道由蛋白水解裂解激活。通道的顶端表达控制是通道传递到膜的功能，通过内吞作用进行回收，以及通道循环和降解之间的平衡。对反应性细胞系和原生组织（包括肾和肺）的多次观察表明，通道活性的调节与构成完全活跃通道的3个独立亚基的非协调调节有关。目前的实验将确定网格蛋白介导的通道内吞作用的结合伙伴和调节位点，内吞途径中单个亚基的命运以及通道再循环到顶膜的调节。实验旨在确定通道亚基的非协调调节是否发生在内噬途径中，并与野生型和具有不同处理方式的劈裂通道有关。被蛋白水解激活。该研究旨在确定在高血压等疾病状态下可能受到异常调节的调节机制。

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 in the kidney occurs in the distal nephron via conductive transport through the 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 duce, but in airway epithelia and colon as well. Abnormalities of ENaC function have been demonstrated in hereditary forms of salt-sensitive hypertension, renal salt wasting, and cystic Fibrosis. The long term goal of this research is to understand the factors that regulate ENaC expression in the apical membrane of epithelial cells and the mechanisms by which hormones, physiologic conditions and other channels (such as the cystic fibrosis trahsmembrane regulator CFTR) control ENaC function. Major control of ENaC function is exerted by regulation of the number of active channels in the membrane of Na+ reabsorbing cells. Channels are activated by proteolytic cleavage. Control of apical expression of the channel is a function of delivery of the channel to the membrane, retrieval through endocytosis, and the balance between recycling and degradation of the channel. Multiple observations in responsive cell lines and native tissues including kidney and lung have demonstrated that modulation of channel activity is associated with non-coordinate regulation of the 3 separate subunits which make up the fully active channel. The current experiments will define the binding partners and regulatory sites of clathrin-mediated endocytosis of the channel, the fate of the individual subunits within the endocytic pathways and the regulation of channel recycling to the apical membrane. Experiments are designed to determine if non-coordinate regulation of channel subunits takes place in the endocytic pathway and is related to differential handling of wild type and cleaved channels which have.been activated by proteolysis. The research aims to identify regulatory mechanisms which may be subject to abnormal regulation in disease states such as hypertension.