Park Jinseo, Fu Ziao, Frangaj Aurel, Liu Jonathan, Mosyak Lidia, Shen Tong, Slavkovich Vesna N, Ray Kimberly M, Taura Jaume, Cao Baohua, Geng Yong, Zuo Hao, Kou Yongjun, Grassucci Robert, Chen Shaoxia, Liu Zheng, Lin Xin, Williams Justin P, Rice William J, Eng Edward T, Huang Rick K, Soni Rajesh K, Kloss Brian, Yu Zhiheng, Javitch Jonathan A, Hendrickson Wayne A, Slesinger Paul A, Quick Matthias, Graziano Joseph, Yu Hongtao, Fiehn Oliver, Clarke Oliver B, Frank Joachim, Fan Qing R
Department of Pharmacology, Columbia University, New York, NY, USA.
Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA.
Nature. 2020 Aug;584(7820):304-309. doi: 10.1038/s41586-020-2452-0. Epub 2020 Jun 24.
The human GABA receptor-a member of the class C family of G-protein-coupled receptors (GPCRs)-mediates inhibitory neurotransmission and has been implicated in epilepsy, pain and addiction. A unique GPCR that is known to require heterodimerization for function, the GABA receptor has two subunits, GABA and GABA, that are structurally homologous but perform distinct and complementary functions. GABA recognizes orthosteric ligands, while GABA couples with G proteins. Each subunit is characterized by an extracellular Venus flytrap (VFT) module, a descending peptide linker, a seven-helix transmembrane domain and a cytoplasmic tail. Although the VFT heterodimer structure has been resolved, the structure of the full-length receptor and its transmembrane signalling mechanism remain unknown. Here we present a near full-length structure of the GABA receptor, captured in an inactive state by cryo-electron microscopy. Our structure reveals several ligands that preassociate with the receptor, including two large endogenous phospholipids that are embedded within the transmembrane domains to maintain receptor integrity and modulate receptor function. We also identify a previously unknown heterodimer interface between transmembrane helices 3 and 5 of both subunits, which serves as a signature of the inactive conformation. A unique 'intersubunit latch' within this transmembrane interface maintains the inactive state, and its disruption leads to constitutive receptor activity.
人类γ-氨基丁酸（GABA）受体——G蛋白偶联受体（GPCRs）C类家族的成员——介导抑制性神经传递，并与癫痫、疼痛和成瘾有关。作为一种已知功能上需要异源二聚化的独特GPCR，GABA受体有两个亚基，GABA和GABA，它们在结构上同源，但执行不同且互补的功能。GABA识别正构配体，而GABA与G蛋白偶联。每个亚基的特征是一个细胞外捕蝇草（VFT）模块、一个下行肽连接子、一个七螺旋跨膜结构域和一个细胞质尾巴。尽管VFT异源二聚体结构已得到解析，但全长受体的结构及其跨膜信号传导机制仍然未知。在这里，我们展示了通过冷冻电子显微镜捕获的处于非活性状态的GABA受体的近全长结构。我们的结构揭示了几种与受体预先结合的配体，包括嵌入跨膜结构域内以维持受体完整性并调节受体功能的两种大型内源性磷脂。我们还确定了两个亚基的跨膜螺旋3和5之间以前未知的异源二聚体界面，它作为非活性构象的标志。这个跨膜界面内一个独特的“亚基间锁扣”维持非活性状态，其破坏会导致受体组成型活性。
