Bacterial Proteins in the Nicotinic/GABA Receptor Family

描述(由申请人提供)： 烟碱型乙酰胆碱受体和GABAA受体是中枢神经系统烟碱类配体门控离子通道受体家族的成员。它们在尼古丁、可卡因、酒精和巴比妥酸盐成瘾中发挥着重要作用。更好地预防或治疗这些成瘾将对人类健康产生重大影响。需要这些受体的高分辨率结构作为了解这些受体如何工作、它们如何影响加法以及如何设计受体特异性药物用于成瘾以及阿尔茨海默氏症和帕金森氏症、癫痫和精神疾病的靶向治疗的基础。乙酰胆碱结合蛋白作为尼古丁受体的结构模型受到限制，因为它不是离子通道。然而，功能性尼古丁受体的结构一直难以捉摸。一个主要的障碍是难以获得足够的蛋白质，无论是用于X射线结晶学还是用于核磁共振的同位素标记。虽然目前还没有鉴定出细菌的尼古丁受体，但这种细菌受体原则上可以解决这个问题。与细菌钾离子通道和氯离子通道对理解这些通道家族的影响类似，细菌尼古丁受体有望显著促进对尼古丁受体结构和功能的理解。我们已经鉴定了几种细菌蛋白，它们的主要氨基酸序列与烟碱型乙酰胆碱、离子型GABA和甘氨酸受体的胞外区和跨膜区相似。这个项目的长期目标是开发一种原子水平的结构解释，解释尼古丁受体是如何导致成瘾的。这项应用的目的是确定细菌蛋白是否属于尼古丁受体家族。中心假设是，初级氨基酸序列与真核细胞尼古丁亚基相似的细菌蛋白是尼古丁受体家族的成员。这些特定的目的验证了这一假说：(1)确定与尼古丁家族亚基有实质性初级序列同源性的细菌蛋白是否组装成寡聚体；(2)确定这些蛋白是否被运输到细胞表面；以及(3)确定这些蛋白的电生理性质。鉴定第一个细菌尼古丁受体将为这一重要受体家族的结构研究提供有希望的候选者。

DESCRIPTION (provided by applicant): Nicotinic acetylcholine receptors and GABAA receptors are members of the nicotinoid family of ligand-gated ion channel receptors of the central nervous system. They play major roles in addiction to nicotine, cocaine, alcohol, and barbiturates. Better prevention or treatment of these addictions will have major impact on human heath. High-resolution structures of these receptors are needed as a foundation on for understanding how these receptors work, how they affect addition, and how receptor-specific drugs can be designed for targeted therapeutics for addiction and also for Alzheimer's and Parkinson's diseases, epilepsy, and mental illnesses. The acetylcholine binding protein is limited as a structural model of nicotinoid receptors, because it is not an ion channel. Structures of functional nicotinoid receptors, however, have been elusive. A major obstacle has been the difficulty of obtaining enough protein, either for X-ray crystallography or with isotopic labeling for NMR. Although no bacterial nicotinoid receptors have yet been identified, such bacterial receptors could, in principle, solve this problem. Similar to the impact that bacterial potassium and chloride ion channels have on understanding those families of channels, bacterial nicotinoid receptors promise to significantly advance the understanding of the structure and function of nicotinoid receptors. We have identified several bacterial proteins whose primary amino acid sequences are similar to the extracellular domain and transmembrane domains of nicotinic acetylcholine, ionotropic GABA, and glycine receptors. The long-range goal of this project is to develop an atomic-level structural interpretation of how nicotinoid receptors contribute to addiction. The objective of this application is to determine whether bacterial proteins belong to the nicotinoid receptor family. The central hypothesis is that bacterial proteins with primary amino acid sequences that are similar to eukaryotic nicotinoid subunits are members of the nicotinoid receptor family. These specific aims test this hypothesis: (1) determine whether bacterial proteins with substantial primary sequence homology to subunits in nicotinoid family assemble into oligomers; (2) determine whether these proteins are transported to the cell surface; and (3) determine electrophysiological properties of these proteins. Identifying the first bacterial nicotinoid receptors will provide promising candidates for structural study of this important family of receptors.