Mechanism of activation and modulation in human GABA(B) receptor

项目摘要 抑制性神经递质GABA在大脑中产生缓慢和长期的抑制作用， 代谢型GABAB受体（GABABR）的活化。GABABR信号传导的缺陷已经被 涉及各种神经和情绪障碍，包括痉挛、癫痫、成瘾和 焦虑GABABR是C类G蛋白偶联受体（GPCR）家族的成员，其通常 作为二聚体起作用并具有大的胞外结构域。基本问题依然存在 关于这些C类受体的激活和调节的分子机制。 GABABR是GABAB 1和GABAB 2亚基的异源二聚体，受钾离子调节， 含有通道四聚化结构域（KCTD）的蛋白辅助亚基。在本提案中，我们将 开发全长GABABR、其辅助亚基及其与G- 蛋白基于我们的细胞外和细胞内成分的结构模型， 人GABABR，我们建议确定GABABR辅助亚基的结构多样性 KCTDs，并阐明KCTDs和G蛋白之间的相互作用（目的1），描述分子 GABABR和KCTD之间的关联，并确定其对GABABR信号传导的影响（目的2），以及 解析多种功能状态下全长GABABR的结构，表征变构 GABABR和G蛋白之间的相互作用（目的3）。我们将采用创新的战略， 结合结构和功能分析，包括冷冻电子显微镜（EM）和纳米盘。 总之，这些研究将促进我们对GABA在脑内作用的分子基础的理解。 大脑，导致治疗神经系统疾病的新疗法的发展。

PROJECT SUMMARY The inhibitory neurotransmitter GABA produces slow and prolonged inhibition in the brain through activation of metabotropic GABAB receptors (GABABR). Defects in GABABR signaling have been implicated in various neurological and mood disorders including spasticity, epilepsy, addiction and anxiety. GABABR is a member of the class C G protein-coupled receptor (GPCR) family, which typically functions as a dimer and possesses large extracellular domains. Fundamental questions remain concerning the molecular mechanisms underlying activation and modulation of these class C receptors. The GABABR is a heterodimer of GABAB1 and GABAB2 subunits and is modulated by the potassium channel tetramerization domain-containing (KCTD) protein auxiliary subunits. In this proposal, we will develop structural models for full-length GABABR, its auxiliary subunits and their complexes with G- protein. Building on our structural models for both the extracellular and intracellular components of human GABABR, we propose to determine the structural diversity of GABABR auxiliary subunits KCTDs, and elucidate the interactions between KCTDs and G proteins (Aim 1), describe the molecular association between GABABR and KCTD, and determine its impact on GABABR signaling (Aim 2), and solve the structures of full-length GABABR in multiple functional states, characterizing the allosteric interaction between the GABABR and G proteins (Aim 3). We will use an innovative strategy of combining structural and functional analyses, including cryo-electron microscopy (EM) and nanodiscs. Together, these studies will advance our understanding of the molecular basis of GABA action in the brain, leading to the development of novel therapeutics for treating neurological diseases.