3D Structure and Function of the Cys-loop Family of Ligand-gated Ion Channels

描述(申请人提供)：Cys-loop受体是五聚体配体门控离子通道(LGIC)，在中枢和外周神经系统中介导快速的神经传递，由于其氨基末端和细胞外配体结合域中保守的二硫键而得名。这个完整的膜蛋白超家族包括乙酰胆碱、5-羟色胺、γ-氨基丁酸、甘氨酸和几种无脊椎动物受体的离子电泳型受体。这些亚家族中的每一个都包括受体亚型，它们具有独特的配体结合和通道门控特性，这是由它们特定的亚基组成决定的。虽然不同受体亚型对配体的偏好和门控动力学有很大的差异，但变构激活机制被认为在所有Cys-loop受体中是保守的，这种机制将小分子激动剂的结合传递到大约80埃远的通道开口。因此，对单个受体亚型的研究将在亚型选择疗法的设计方面提供信息，同时对整个Cys-loop家族的受体功能机制具有更广泛的影响。目前，该受体家族没有原子分辨结构信息；大多数结构信息是基于4埃电子显微镜结构和自然产生的可溶胞外域的晶体结构。这项建议的总体目标是在高分辨率下确定Cys-loop受体家族成员的3D结构。这一目标将通过检查异源表达系统中已知家族的代表性成员来确定最适合结晶的候选成员来实现；然后将结晶Cys-loop受体并确定其结构。结构研究将得到功能分析的补充，功能分析测试关于受体状态转换机制的新的基于结构的假说。这些结果将对该家族的一般意义和具体的亚型产生广泛的影响。拟议的研究将为阿尔茨海默氏症和帕金森氏症以及精神分裂症等神经退行性疾病的主要治疗目标提供洞察力。研究结果还将提高我们为这些疾病设计选择性疗法的能力，从而限制有害的副作用。

DESCRIPTION (provided by applicant): Cys-loop receptors are pentameric ligand-gated ion channels (LGICs) that mediate fast neurotransmission in the central and peripheral nervous systems, and are so named due to a conserved disulfide linkage in their amino terminal, extracellular ligand binding domains. This superfamily of integral membrane proteins includes the ionophoretic receptors for acetylcholine, serotonin, gamma-aminobutyric acid, glycine, and several invertebrate receptors. Each of these subfamilies comprises receptor subtypes with unique ligand binding and channel gating properties as determined by their specific subunit composition. While there is great variation in the preferences for ligands and gating kinetics between receptor subtypes, the allosteric activation mechanism that communicates binding of small molecule agonists into channel opening some 80-angstroms distant is believed to be conserved among all Cys-loop receptors. Hence, studies on an individual receptor subtype will be informative in terms of design of subtype-selective therapeutics, while simultaneously having broader implications for mechanisms of receptor function for the entire Cys-loop family. Currently, no atomic-resolution structural information exists for this family of receptors; most structural information is based on a 4-angstrom electron microscopy structure and crystallographic structures of a naturally-occurring soluble extracellular domain. The overall goal of this proposal is to determine the 3D structure of a Cys-loop receptor family member at high resolution. This goal will be accomplished by examining representative members from the known families in heterologous expression systems to determine the best candidates for crystallization; a Cys-loop receptor will then be crystallized and its structure determined. The structural studies will be complemented by functional assays that test new structure-based hypothesis regarding mechanisms of state transitions in the receptor. The results will have broad implications for the family in general and the subtype specifically. The proposed studies will provide insight into the major therapeutic targets for neurodegenerative disorders such as Alzheimer's and Parkinson's diseases, and schizophrenia. The results will also improve our ability to design selective therapeutics for these illnesses, thereby limiting deleterious side effects.