DeltaF508-CFTR Trafficking Regulated by 4-Phenylbutyrate

描述（由申请方提供）：囊性纤维化跨膜传导调节因子（CFTR）是一种多功能蛋白质，既可转运Cl-穿过上皮细胞的顶端质膜，又可通过其他蛋白质（如上皮钠通道ENaC）调节离子转运。囊性纤维化（CF）的一个主要特征是气道上皮中经由ENaC的Na+转运的过度活跃，尽管这是由CFTR的缺失导致的机制尚不清楚。在突变CFTR功能的药理学修复方面的努力，例如使用4-苯基丁酸钠（4PBA）来纠正最常见的突变CFTR的运输，？F508-CFTR集中于评估突变CFTR的Cl-转运功能的恢复。这些研究往往忽略了4PBA或其他CFTR“校正剂”对ENaC贩运和/或功能的影响。我们提出的研究将解决是否药物修复，或纠正？F508-CFTR运输将促进CF气道中ENaC的适当调节。这是一个关键问题，在实施药理学策略，以改善？F508 CFTR贩运和功能。我们的假设是，4PBA诱导上皮细胞中的分子伴侣表达的调节，从而导致CFTR和ENaC的细胞内运输和功能表达的改变。由于4PBA还改善了CF以外疾病中许多突变蛋白的细胞内运输，因此该假设也可能与开发许多其他蛋白构象疾病的药物疗法密切相关。4PBA导致胞质分子伴侣Hsc 70和Hsp 70以及29 kDa的新型腔内质网蛋白ERp 29的表达改变。我们的数据表明，这些分子伴侣的表达特异性改变调节CFTR，？F508和ENaC运输和功能表达。本建议将建立在这些初步数据和测试这一假设的研究，针对以下具体目标：具体目标1：要确定Hsc 70和Hsp 70调节CFTR，？上皮细胞中的F508和ENaC运输。具体目标二：为了确定ERp 29，一种新的4-苯基丁酸调节的腔内质网蛋白，调节CFTR的运输的机制，？上皮细胞中的F508和ENaC。 公共卫生相关性：肺和气道保护自身免受环境影响的主要机制取决于呼吸道上皮细胞中适当的离子转运。这种离子转运在囊性纤维化中是异常的，导致显著的发病率和死亡率。这些数据将促进对囊性纤维化和其他气道疾病中负责离子转运的通道的调节的更好理解，并为囊性纤维化的新的、基于机制的疗法的开发提供信息。

DESCRIPTION (provided by applicant): The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) is a multifunctional protein that both transports Cl- across the apical plasma membrane of epithelial cells and regulates ion transport by other proteins, such as the Epithelial Sodium Channel, ENaC. A cardinal feature of Cystic Fibrosis (CF) is hyperactivity of Na+ transport via ENaC in the airway epithelia, although the mechanism by which this results from the absence of CFTR is not known. Efforts at pharmacologic repair of mutant CFTR function, such as the use of Sodium 4- Phenylbutyrate (4PBA) to correct trafficking of the most common mutant CFTR, ?F508-CFTR, have concentrated on assessing restoration of a mutant CFTR's Cl- transport function. These studies have often ignored the influence of 4PBA or other CFTR "correctors" on ENaC trafficking and/or function. Our proposed studies will address whether pharmacologic repair, or correction of ?F508-CFTR trafficking will promote appropriate regulation of ENaC in the CF airway. This is a key issue in the implementation of pharmacologic strategies to improve ?F508 CFTR trafficking and function. Our hypothesis is that 4PBA induces modulations of molecular chaperone expression in epithelial cells that result in altered intracellular trafficking and functional expression of CFTR and ENaC. Because 4PBA also improves the intracellular trafficking of a number of mutant proteins in diseases besides CF, this hypothesis may also be germane to developing pharmacologic therapies for a number of other protein conformational diseases. 4PBA causes altered expression of the cytosolic chaperones Hsc70 and Hsp70, as well as a novel luminal endoplasmic reticular protein of 29 kDa, ERp29. Our data suggest that specifically altered expression of these chaperones modulates CFTR, ?F508 and ENaC trafficking and functional expression. The present proposal will build on these preliminary data and test this hypothesis with studies directed at the following Specific Aims: Specific Aim 1: To determine the mechanism by which Hsc70 and Hsp70 modulate CFTR, ?F508 and ENaC trafficking in epithelial cells. Specific Aim 2: To determine the mechanism by which ERp29, a novel 4-phenylbutyrate-regulated luminal endoplasmic reticular protein, regulates the trafficking of CFTR, ?F508 and ENaC in epithelial cells. PUBLIC HEALTH RELEVANCE: The major mechanim by which the lung and airway defends itself from the environment depends on proper ion transport in the respiratory epithelia. Such ion transport is aberrant in Cystic Fibrosis, leading to significant morbidity and mortality. These data will promote better understanding of the regulation of channels responsible for ion transport in Cystic Fibrosis and other diseases of the airway, and inform development of novel, mechanism-based therapies for Cystic Fibrosis.