Targeting the oligomerization of human ABCG2

描述(申请人提供)：多药耐药(MDR)是人类癌症化疗成功的主要问题。已知的癌细胞多药耐药机制之一是介导抗癌药物外流的膜蛋白表达增加。具有这种药物外排功能的主要膜蛋白有三种：P-糖蛋白(Pgp)、多药耐药相关蛋白1(MRP1)和乳腺癌耐药蛋白/米托蒽醌耐药蛋白(BCRP/MXR)。这些蛋白属于三磷酸腺苷结合盒(ABC)膜转运蛋白超家族，分别命名为ABCB1、ABCC1和ABCG2。我们实验室的长期目标是了解和克服ABC转运体介导的癌细胞多药耐药的分子机制。与人ABCB1和ABCC1不同，人ABCG2是半ABC转运蛋白，其核苷酸结合区位于氨基末端，被认为具有同源二聚体的功能。然而，我们最近的研究表明，它是以同源异构体的形式存在的。在这一应用中，我们计划测试这一假设，即人ABCG2作为同源十聚体而不是主要的同源二聚体发挥作用，我们可以针对寡聚过程来逆转ABCG2介导的耐药性。为此，我们计划完成以下五个具体目标：(1)确定人ABCG2是同源二聚体还是同源十聚体；(2)确定人ABCG2的十二聚体是否是功能转运体；(3)确定人ABCG2的寡聚是否发生在内质网(ER)中；(4)确定人ABCG2的羧基跨膜结构域是否与寡聚有关；(5)确定是否有可能通过破坏ABCG2的寡聚过程来逆转其介导的耐药性。印第安纳大学癌症研究所良好的科学环境和慷慨的机构支持将极大地促进该项目的成功。本研究获得的信息和探针将有助于我们理解ABCG2介导的药物转运的分子机制。这项工作还可能使我们发现一类新的治疗剂，可以帮助克服抗药性癌症。

DESCRIPTION (provided by applicant): Multidrug resistance (MDR) is a major problem for successful chemotherapy of human cancers. One of the known mechanisms of MDR in cancer cells is the elevated expression of membrane proteins that mediate the efflux of anticancer drugs. Three major membrane proteins that have this drug-efflux function have been identified: P-glycoprotein (Pgp), multidrug resistance-associated protein 1 (MRP1), and breast cancer resistance protein/mitoxantrone resistance protein (BCRP/MXR). These proteins belong to the ATP- binding cassette (ABC) membrane transporter superfamily and are also named as ABCB1, ABCC1, and ABCG2, respectively. The long-term goal of our laboratory is to understand the molecular mechanisms of and to overcome ABC transporter-mediated MDR in cancer cells. Unlike human ABCB1 and ABCC1, human ABCG2 is a half ABC transporter with its nucleotide binding domain located at the amino terminus and has been thought to function as a homodimer. However, our recent studies suggest that it exists as a homododecamer. In this application, we plan to test the hypothesis that human ABCG2 functions as a homododecamer rather than the prevailing homodimer and we can target the oligomerization process to reverse ABCG2-mediated drug resistance. To this end, we plan to accomplish the following five specific aims: (1) to determine if human ABCG2 is a homodimer or homododecamer; (2) to determine if the dodecameric form of human ABCG2 is a functional transporter; (3) to determine if the oligomerization of human ABCG2 occurs in the endoplasmic reticulum (ER); (4) to determine if the carboxyl transmembrane domain of human ABCG2 is responsible for oligomerization; (5) to determine if it is possible to reverse ABCG2-mediated drug resistance by disrupting its oligomerization process. The excellent scientific environment at Indiana University Cancer Research Institute and the generous institutional support will contribute enormously to the likelihood of success of this project. The information and probes obtained from this study will help us understand the molecular mechanism of human ABCG2-mediated drug transport. This work may also lead us to the discovery of a new class of therapeutic agents that can help overcome drug-resistant cancers.