Biophysics of Receptor/G-protein Interactions

描述（由申请人提供）：与异源三聚体GTP结合蛋白偶联的细胞表面受体普遍负责细胞外信使（如激素、神经递质和各种感觉刺激）的跨膜传递。由于这种直接参与最关键的细胞功能的调节，G蛋白偶联受体（GPCR）是治疗干预的最重要靶点之一。据估计，大约50%的药物在使用中作用于GPCR。因此，在分子水平上了解受体和G蛋白的功能是公共卫生研究的最高优先事项之一。几个相互竞争的模型旨在描述GPCR激活G蛋白的普遍机制，但到目前为止还没有提出令人信服的和结论性的实验证据。假设：G蛋白23亚基复合物是G蛋白激活换档模型中心的关键分子开关。我们将使用原型GPCR视紫红质（R）和负责视网膜视杆细胞中光转导的G蛋白转导素（Gt）作为模型系统来检验这一假设。三个相互关联的具体目标将测试假设的各个方面，如受体-G蛋白复合物的分子组织问题，受体-G蛋白界面的高分辨率图像，受体的信号传递机制，以及单个G蛋白亚基，特别是G23亚基复合物在这一动态过程中的作用。本项目旨在了解细胞间通讯和细胞对各种感官刺激的反应的普遍原则。描述这些基本分子机制的几个相互竞争的理论将被测试，以深入了解细胞表面受体蛋白和特定蛋白质-蛋白质相互作用的内部运作。由于目前市场上几乎一半的治疗药物都是针对这些信号通路的，因此这些研究所获得的知识对于新药设计和对抗心脏病、哮喘和视力障碍等多种疾病至关重要。

DESCRIPTION (provided by applicant): Cell surface receptors coupled to the heterotrimeric GTP-binding proteins are universally responsible for the transmembrane transmission of extracellular messengers such as hormones, neurotransmitters and a variety of sensory stimuli. Because of this direct involvement in the regulation of the most crucial cellular functions, G-protein coupled receptors (GPCRs) are among the most important targets of therapeutic intervention. It's estimated that about 50% of drugs in use act on GPCRs. Thus, understanding of the receptor and the G- protein functions at the molecular level is among the highest priorities of public health research. Several competing models aim at describing the universal mechanism of G- protein activation by GPCRs, but none has presented compelling and conclusive experimental evidence so far. HYPOTHESIS: G-protein 23-subunit complex is a key molecular switch at the center of the gear-shift model of G-protein activation. We will test this hypothesis using the prototypical GPCR rhodopsin (R) and the G-protein transducin (Gt) responsible for phototransduction in retinal rod cells as a model system. Three interconnected Specific Aims will test various aspects of the hypothesis, such as questions of the molecular organization of the receptor- G-protein complex, the high-resolution picture of the receptor-G-protein interface, the mechanism of signal transfer from the receptor, and the roles of individual G- protein subunits, especially the G23 subunit complex, in this dynamic process. This project aims at understanding the universal principles underlying cell- to-cell communications and cellular responses to a variety of sensory stimuli. Several competing theories describing these basic molecular mechanisms will be tested to gain insights into the inner workings of cell surface receptor proteins and specific protein-protein interactions. Because almost half of all therapeutics on the market today target these signaling pathways, knowledge obtained as a result of these studies will be essential in new drug design and fighting a wide range of diseases such as heart problems, asthma and vision disorders.