G Protein Activation Mechanisms by Hormone Receptors

描述(申请人提供)：本申请的长期目标是了解激素如何将信号传递给细胞。一般的策略是专注于一个由七个跨膜受体组成的超家族，这些受体结合荷尔蒙并通过G蛋白传递信号。G蛋白偶联受体(GPCRs)作为细胞内信号转导机制的广泛应用使其成为药物作用的频繁靶点；据估计，几乎60%的药物作用于GPCRs。这些药物包括常用的药物，如β-受体阻滞剂(心血管)、β-激动剂(哮喘)、抗组胺药(H1过敏、H2溃疡)和阿片类药物(疼痛)。据估计，3%的人类基因编码GPCRs；近一半的受体的配体仍有待确定，因此提供了许多新的潜在药物靶点。尽管受体在生物学和医学上具有重要意义，但受体激活G蛋白的分子机制却知之甚少。为了解决这些基本问题，这项建议使用了包括遗传筛选、计算模型和生化分析在内的各种技术来研究人类补体因子5(C5a)受体，它是GPCRs视紫红质家族的成员。C5a受体介导中性粒细胞趋化，在酵母中表达时功能良好，使高通量结构/功能研究成为可能的受体区域的激素结合或耦合到G蛋白。视紫红质是一种被光激活的光感受器，已经通过生物物理分析得到了很好的特征，并且是唯一可以获得晶体结构的GPCR。这两个受体具有相似的结构，使得可以生成C5a受体的计算模型，并可以直接测试来自C5a受体遗传研究的特定受体激活模型。这项提案中概述的研究将为深入了解受体如何在细胞中发挥“开/关”开关的功能提供见解，从而为开发新的治疗药物提供合理的药物设计。

DESCRIPTION (provided by applicant): The long-term objectives of this application are to understand how hormones transduce signals to cells. The general strategy is to focus on a superfamily of seven transmembrane-spanning receptors that bind hormones and mediate signals via G proteins. The widespread use of G protein-coupled receptors (GPCRs) as a mechanism of signal transduction into cells make them frequent targets of pharmaceutical drugs; according to one estimate, almost 60% of all drugs act on GPCRs. These include commonly prescribed agents such as beta-blockers (cardiovascular), beta-agonists (asthma), antihistamines (H1- allergies, H2-ulcers), and opiates (pain). An estimated 3% of human genes encode GPCRs; the ligands remain to be identified for nearly half of the receptors, thus offering many new potential drug targets. Despite their biological and medical importance, the molecular mechanisms by which receptors activate G proteins are poorly understood. To address these fundamental questions, this Proposal employs a variety of techniques including genetic screens, computational modeling, and biochemical analyses to study the human complement factor 5 (C5a) receptor, a member of the rhodopsin family of GPCRs. The C5a receptor mediates neutrophil chemotaxis and functions well when expressed in yeast, making possible high-throughput structure/function studies of regions of the receptor that bind hormones or couple to G proteins. Rhodopsin, a photoreceptor activated by light, has been well characterized by biophysical analyses, and is the only GPCR for which a crystal structure is available. The two receptors share similar structures, enabling computational models of the C5a receptor to be generated and for specific models of receptor activation, derived from genetic studies of the C5a receptor, to be tested directly. The studies outlined in this Proposal will provide insights into how receptors function as "on/off" switches in cells, thus aiding rational drug design for the development of new therapeutic agents.