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

描述（由申请人提供）：Cys环受体是五聚体配体门控离子通道（LGIC），其介导中枢和外周神经系统中的快速神经传递，并且由于其氨基末端、细胞外配体结合结构域中的保守二硫键而如此命名。该整合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受体。这些亚家族中的每一个都包含具有独特配体结合和通道门控特性的受体亚型，如由其特定亚基组成所确定的。虽然受体亚型之间对配体的偏好和门控动力学存在很大差异，但认为将小分子激动剂结合到约80埃距离的通道开口中的变构激活机制在所有Cys环受体中是保守的。因此，对单个受体亚型的研究将在亚型选择性治疗的设计方面提供信息，同时对整个Cys环家族的受体功能机制具有更广泛的意义。目前，没有原子分辨率的结构信息存在这个家庭的受体;大多数结构信息是基于4埃电子显微镜结构和晶体结构的天然存在的可溶性细胞外结构域。该提案的总体目标是以高分辨率确定Cys环受体家族成员的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以确定结晶的最佳候选物来实现;然后将Cys环受体结晶并确定其结构。结构研究将通过功能测定来补充，功能测定测试关于受体状态转换机制的新的基于结构的假设。这些结果将对该家族和该亚型产生广泛的影响。拟议中的研究将为神经退行性疾病（如阿尔茨海默病和帕金森病）和精神分裂症的主要治疗靶点提供深入了解。研究结果还将提高我们为这些疾病设计选择性治疗方法的能力，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.