Regulatory Interactions of CFTR and ENaC

描述(由申请人提供)：囊性纤维化跨膜电导调节剂(CFTR)是一种多功能蛋白质，它能将氯化物运输到上皮细胞的顶端质膜上。CFTR还调节其他蛋白质的离子转运，如上皮钠通道，ENaC。CFTR抑制ENaC在呼吸道上皮细胞中的钠转运，囊性纤维化的主要特征之一是ENaC在呼吸道上皮细胞的过度激活。然而，CFTR和ENaC的调控相互作用发生的机制尚不清楚。对突变的CFTR功能进行药物修复的努力主要集中在评估突变的CFTR的氯离子转运特性的恢复上，而在很大程度上忽略了CFTR的其他功能，如它与ENaC的相互调节。因此，通过药物修复突变的cftr功能是否也能恢复cftr和ENaC之间的关键调控相互作用仍是一个悬而未决的问题。因此，了解这些关键调控相互作用的分子基础是实施改善CFTR功能的药理学策略的关键。其他人则认为CFTR通过降低ENaC开放概率(Po)来抑制ENaC活性。相反，我们的初步数据强烈表明，CFTR和ENaC可能也有与细胞内转运相关的调控相互作用。因此，我们将检验这一假设：CFTR和ENaC的调节相互作用导致这些通道在上皮细胞中的细胞内运输和表面表达发生变化。修复突变cftr的药理学试剂可能会调节这些转运相互作用。一些这样的制剂可能通过改变胞质分子伴侣的表达来影响转运。由于CFTR和ENaC的某些胞浆结构域似乎对调节相互作用至关重要，伴侣与这些胞浆结构域的结合可能调节这种相互作用。目前的建议将建立在这些调查和初步数据的基础上，并针对以下具体目标进行研究，以解决这一假说：1)确定CFTR和ENaC相互调节彼此细胞内上皮细胞运输的动力学机制。2)探讨胞浆70kodalton分子伴侣对CFTR和ENaC在上皮细胞中转运作用的影响和调控机制。相关性：肺和呼吸道保护自身免受环境影响的主要机制依赖于呼吸道上皮细胞中适当的离子传输。这种离子转运在囊性纤维化中是异常的，并导致显著的发病率和死亡率。这些数据将有助于更好地了解囊性纤维化肺疾病的发病机制，以及其他一些呼吸道疾病，以及其他分泌上皮疾病的发病机制。

DESCRIPTION (provided by applicant): The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) is a multifunctional protein that transports chloride across the apical plasma membrane of epithelial cells. CFTR also regulates ion transport by other proteins, such as the Epithelial Sodium Channel, ENaC. CFTR inhibits sodium transport by ENaC in airway epithelia, and one of the cardinal features of Cystic Fibrosis (CF) is hyperactivity of ENaC in the airway epithelia. However, the mechanism by which regulatory interactions of CFTR and ENaC occurs is not clear. Efforts at pharmacologic repair of mutant CFTR function have concentrated on assessing restoration of a mutant CFTR's chloride transport properties and have largely ignored other functions of CFTR, such as its interregulation with ENaC. It thus remains an open question whether pharmacologic repair of mutant CFTR function will also restore the critical regulatory interactions of CFTR and ENaC. Understanding the molecular basis of these critical regulatory interactions is therefore key in the implementation of pharmacologic strategies to improve CFTR function. Others have suggested that CFTR inhibits ENaC activity by decreasing ENaC open probability (Po). In contrast, our preliminary data strongly suggests that CFTR and ENaC may also have regulatory interactions related to intracellular trafficking. We will therefore test the hypothesis that: Regulatory interactions of CFTR and ENaC result in altered intracellular trafficking and surface expression of these channels in epithelial cells. Pharmacologic agents that repair mutant CFTR may modulate these trafficking interactions. Some such agents may influence trafficking by altering the expression of cytosolic molecular chaperones. As certain cytosolic domains of CFTR and ENaC appear critical for regulatory interactions, binding of chaperones to these cytosolic domains may regulate such interactions. The present proposal will build on these investigations and preliminary data and address this hypothesis with studies directed at the following Specific Aims: 1) To determine the kinetic mechanism by which CFTR and ENaC regulate each other's intracellular trafficking in epithelial cells. 2) To determine the mechanism by which cytosolic 70 kilodalton molecular chaperones influence and regulate these trafficking interactions of CFTR and ENaC in epithelial cells. Relevance: The major mechanism 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 and leads to significant morbidity and mortality. These data will promote better understanding of the pathogenesis of not only Cystic Fibrosis lung disease, but also a number of other diseases of the airway, as well as diseases of other secretory epithelia.