The CLIC-1 Chloride Channel: Structure and Function

描述（由申请人提供）：氯离子通道蛋白对许多细胞功能至关重要，已知氯离子通道功能障碍参与许多人类疾病状态的发病机制。我们已经确定并开始表征一个与其他已知氯离子通道结构无关的氯离子通道蛋白家族。该家族的一个成员CLIC-1在许多细胞类型中表达，并且在肾近端小管细胞的顶端结构域中非常高地表达。亚细胞定位研究表明，它存在于膜隔室沿内体途径沿着。我们最近已经证明，重组CLIC-1功能作为一个氯离子选择性通道时，从细菌中纯化和重建磷脂膜。 与典型的离子通道蛋白不同，CLIC蛋白以膜插入形式和细胞质中的可溶形式存在于细胞中。在过去的几年中，已经报道了许多膜蛋白能够呈现可溶于水溶液的构象。在某些情况下，很明显，这些蛋白质可以在膜插入和可溶状态之间分配，并且这种分配在调节这些蛋白质的活性中是重要的。我们现在已经发现CLIC-1能够从水相插入磷脂膜中，并且这种插入的CLIC-1可以作为氯离子通道起作用。在这项资助申请中，我们建议研究这种重要蛋白质的功能性膜插入的生化基础和生物相关性。

DESCRIPTION (provided by applicant): Chloride channel proteins are essential to a host of cellular functions and chloride channel dysfunction is known to be involved in the pathogenesis of a number of human disease states. We have identified and begun to characterize a family of chloride channel proteins which are structurally unrelated to other known chloride channels. One member of this family, CLIC-1, is expressed in many cell types and is very highly expressed in the apical domain of renal proximal tubule cells. Subcellular localization studies indicate that it is present in membrane compartments along the endosomal pathway. We have recently demonstrated that recombinant CLIC-1 functions as a chloride selective channel when purified from bacteria and reconstituted in phospholipid membranes. Unlike typical ion channel proteins, CLIC proteins are present in cells both in a membrane inserted form and in a soluble form in the cytoplasm. Over the past several years, a number of membrane proteins have been reported to be able to assume conformations which are soluble in aqueous solution. In some instances, it is clear that these proteins can partition between membrane-inserted and soluble states and that this partitioning is important in regulation of the activity of these proteins. We have now found that CLIC-1 is capable of inserting into phospholipid membranes from the aqueous phase and this inserted CLIC-1 can function as a chloride channel. In this grant application, we propose to study the biochemical basis and biological relevance of functional membrane insertion of this important protein.