Regulation of ABC proteins functions through protein interactions: role of linker domains of ABCB1/C1 in modulating protein functions

分子在细胞膜上的运输是所有生物生存所必需的。有毒环境中的细胞必须主动将扩散的毒素从细胞内（低浓度）运输到细胞外（高浓度），以对抗毒素的浓度梯度。这种分子的“主动运输”对于细胞的生存是必不可少的，并且对细胞来说是昂贵的，因为它需要以ATP的形式消耗能量。一类活性膜转运蛋白，被称为ABC转运蛋白，含有一个ATP结合盒结构域（或ABC结构域），其功能是利用ATP引起分子跨细胞膜运输。现在人们认识到，abc转运蛋白是最大的膜蛋白家族之一，从细菌到人类的所有生物体中都有发现。人类基因组编码49种ABC蛋白，分为7个亚家族（ABC A - G）。几个实验室的研究表明，这些ABC蛋白可以运输各种底物，包括氯离子、谷胱甘肽、胆固醇、固醇、胆盐和许多药物，仅举几例。因此，影响其正常功能的突变已被证明是超过17种遗传性人类疾病的病因，如囊性纤维化（ABCC7）和杜宾-约翰逊综合征（ABCC2）。一些ABC转运蛋白在癌细胞和感染性生物体中引起对化疗药物的耐药性。因此，鉴于ABC转运蛋白在健康和疾病状况中的作用，它们代表了一类重要的蛋白质“或酶”，必须受到细胞和生物体的严格调节。本提案的目的是鉴定与这些ABC转运蛋白相互作用并调节其功能的蛋白质。我们最近的工作已经确定了一个ABCB1相互作用的蛋白。该蛋白结合到ABCB1的一个高电荷和未知功能的特定区域。因此，这个和其他ABCB1-和abcc1相互作用蛋白的身份和生物学意义是本拨款申请的主题。本研究的结果将提供一种新的方法来调节ABC转运蛋白的功能，从而更好地理解可以调节ABC转运蛋白的细胞途径。

The transport of molecules across the cell membrane is required for the survival of all living organisms. Cells in a toxic environment must actively transport diffused toxins from inside the cell (lower concentration) to the outside (higher concentration) against the toxins' concentration gradients. This "Active Transport" of molecules is essential for survival and is costly to cells, as it requires the expenditure of energy in the form of ATP. One class of active membrane transporters, known as ABC transporters contain an ATP-Binding Cassette domain (or an ABC domain) that functions as an engine that utilizes ATP to cause the transport of molecules across the cell membrane. It is now recognized that the ABC-transporters are one of the largest family of membrane proteins that are found in all living organisms from bacterial to man. The human genome encodes for 49 ABC proteins that are classified into seven subfamilies (ABC A - G). Research from several laboratories has shown these ABC proteins to transport various substrates, including chloride ions, glutathione, cholesterol, sterols, bile salts and many drugs, to name just few. Consequently, mutations affecting their normal functions have been shown to be causative of more than 17 genetic human disorders, such as cystic fibrosis (ABCC7) and Dubin-johnson syndrome (ABCC2). Some ABC transporters cause resistance to chemo-therapeutic drugs in cancer cells and in infectious organisms. Therefore, given the role of ABC transporters in health and disease conditions, they represent an important class of proteins "or enzymes" that must be tightly regulated by cells and organisms. The objectives of this proposal are to identify the proteins that interact with, and regulate the functions of these ABC transporters. Our recent work has identified one ABCB1 interacting protein. This protein binds to a specific domain of ABCB1 that is highly charged and of unknown function. Thus the identity and biologic significance of this and other ABCB1- and ABCC1-interacting proteins is the subject of this grant application. The results of this study should provide a novel approach to regulate or modulate the functions of ABC transporters and consequently a better understanding of the cellular pathways that can regulate ABC transporters.