The CLIC-1 Chloride Channel: Structure and Function

描述(由申请人提供)：氯通道蛋白对许多细胞功能是必不可少的，氯通道功能障碍被认为与许多人类疾病状态的发病机制有关。我们已经鉴定并鉴定了一个氯通道蛋白家族，这些蛋白在结构上与其他已知的氯通道无关。CLIC-1是该家族的成员之一，在多种细胞类型中都有表达，并且在肾近端小管细胞的顶端区域高度表达。亚细胞定位研究表明，它存在于沿着内体途径的膜室中。我们最近已经证明，重组CLIC-1在从细菌中纯化并在磷脂膜上重组时，具有氯离子选择性通道的功能。 与典型的离子通道蛋白不同，CLIC蛋白既以膜插入的形式存在于细胞中，也以可溶的形式存在于细胞质中。在过去的几年里，一些膜蛋白被报道能够呈现出可溶于水的构象。在某些情况下，很明显，这些蛋白质可以在膜插入状态和可溶状态之间进行分配，并且这种分配在调节这些蛋白的活性方面很重要。我们现在发现CLIC-1能够从水相插入磷脂膜，这种插入的CLIC-1可以作为氯离子通道。在这项拨款申请中，我们建议研究这种重要蛋白质的功能膜插入的生化基础和生物学相关性。

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.