Cryo-EM structure of the human α1β3γ2 GABAA receptor in a lipid bilayer
Cryo-EM structure of the human α1β3γ2 GABAA receptor in a lipid bilayer
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DOI：
10.1038/s41586-018-0833-4
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发表时间：
2019-01-24
期刊：
影响因子：
64.8
通讯作者：
Aricescu, A. Radu
中科院分区：
文献类型：
--
作者：
Laverty, Duncan;Desai, Rooma;Aricescu, A. Radu
A 型γ-氨基丁酸 (GABA(A)) 受体是五聚体配体门控离子通道，是脊椎动物神经系统中快速抑制性神经传递的主要驱动因素1,2。它们的功能障碍与一系列神经系统疾病有关，包括抑郁症、癫痫和精神分裂症3,4。在理论上可能的众多组装中，大脑中最普遍的是 α 1 β 2/3 γ 2 GABAA 受体5。 β 3 亚基在维持抑制性张力方面具有重要作用，并且该亚基的单独表达足以挽救 β 1-β 3 三重敲除神经元中的抑制性突触传递6。到目前为止，为异聚 GABAA 受体生成准确结构模型的努力因工程化受体的使用和去污剂的存在而受到阻碍7-9。值得注意的是，最近的一些冷冻电子显微镜重建报告了“塌陷”构象8,9；然而，这些与典型五聚体配体门控离子通道鱼雷烟碱乙酰胆碱受体10,11的结构、同源同源五聚体受体变体12的大量结构工作以及离子通道结构的逻辑不一致。在这里，我们展示了全长人类 alpha 1 beta 3 gamma 2L 的高分辨率冷冻电子显微镜结构，这是一种主要的突触 GABA(A) 受体亚型，在脂质纳米盘中进行功能重建。该受体与正变构调节剂“巨体”结合，并处于脱敏构象。每个GABA(A)受体五聚体含有两个磷脂酰肌醇-4,5-二磷酸分子，其头基占据a1亚基的细胞内近膜区域中带正电的口袋。超过这个水平，细胞内 M3-M4 环很大程度上无序，可能是因为不存在相互作用的突触后蛋白。该结构阐明了异聚 GABA(A) 受体组织的分子原理，并为未来 GABA 信号传导和药理学的机制研究提供了参考框架。
Type A gamma-aminobutyric acid (GABA(A)) receptors are pentameric ligand-gated ion channels and the main drivers of fast inhibitory neurotransmission in the vertebrate nervous system1,2. Their dysfunction is implicated in a range of neurological disorders, including depression, epilepsy and schizophrenia3,4. Among the numerous assemblies that are theoretically possible, the most prevalent in the brain are the alpha 1 beta 2/3 gamma 2 GABAA receptors5. The beta 3 subunit has an important role in maintaining inhibitory tone, and the expression of this subunit alone is sufficient to rescue inhibitory synaptic transmission in beta 1-beta 3 triple knockout neurons6. So far, efforts to generate accurate structural models for heteromeric GABAA receptors have been hampered by the use of engineered receptors and the presence of detergents7-9. Notably, some recent cryo-electron microscopy reconstructions have reported ` collapsed' conformations8,9; however, these disagree with the structure of the prototypical pentameric ligand-gated ion channel the Torpedo nicotinic acetylcholine receptor10,11, the large body of structural work on homologous homopentameric receptor variants12 and the logic of an ion-channel architecture. Here we present a highresolution cryo-electron microscopy structure of the full-length human alpha 1 beta 3 gamma 2L-a major synaptic GABA(A) receptor isoformthat is functionally reconstituted in lipid nanodiscs. The receptor is bound to a positive allosteric modulator ` megabody' and is in a desensitized conformation. Each GABA(A) receptor pentamer contains two phosphatidylinositol-4,5-bisphosphate molecules, the head groups of which occupy positively charged pockets in the intracellular juxtamembrane regions of a1 subunits. Beyond this level, the intracellular M3-M4 loops are largely disordered, possibly because interacting post-synaptic proteins are not present. This structure illustrates the molecular principles of heteromeric GABA(A) receptor organization and provides a reference framework for future mechanistic investigations of GABAergic signalling and pharmacology.