Vollum Institute, Oregon Health & Science University, Portland, OR, USA.
Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
Nature. 2021 Jun;594(7863):448-453. doi: 10.1038/s41586-021-03540-0. Epub 2021 May 12.
AMPA-selective glutamate receptors mediate the transduction of signals between the neuronal circuits of the hippocampus. The trafficking, localization, kinetics and pharmacology of AMPA receptors are tuned by an ensemble of auxiliary protein subunits, which are integral membrane proteins that associate with the receptor to yield bona fide receptor signalling complexes. Thus far, extensive studies of recombinant AMPA receptor-auxiliary subunit complexes using engineered protein constructs have not been able to faithfully elucidate the molecular architecture of hippocampal AMPA receptor complexes. Here we obtain mouse hippocampal, calcium-impermeable AMPA receptor complexes using immunoaffinity purification and use single-molecule fluorescence and cryo-electron microscopy experiments to elucidate three major AMPA receptor-auxiliary subunit complexes. The GluA1-GluA2, GluA1-GluA2-GluA3 and GluA2-GluA3 receptors are the predominant assemblies, with the auxiliary subunits TARP-γ8 and CNIH2-SynDIG4 non-stochastically positioned at the B'/D' and A'/C' positions, respectively. We further demonstrate how the receptor-TARP-γ8 stoichiometry explains the mechanism of and submaximal inhibition by a clinically relevant, brain-region-specific allosteric inhibitor.
AMPA 型谷氨酸受体介导海马神经元回路之间的信号转导。AMPA 受体的运输、定位、动力学和药理学由一组辅助蛋白亚基调节，这些亚基是整合膜蛋白，与受体结合形成真正的受体信号复合物。到目前为止，使用工程蛋白构建体对重组 AMPA 受体-辅助亚基复合物的广泛研究还不能准确阐明海马 AMPA 受体复合物的分子结构。在这里，我们使用免疫亲和纯化获得了小鼠海马钙不可渗透的 AMPA 受体复合物，并使用单分子荧光和冷冻电子显微镜实验阐明了三种主要的 AMPA 受体-辅助亚基复合物。GluA1-GluA2、GluA1-GluA2-GluA3 和 GluA2-GluA3 受体是主要的组装体，辅助亚基 TARP-γ8 和 CNIH2-SynDIG4 分别非随机地位于 B'/D'和 A'/C'位置。我们进一步证明了受体-TARP-γ8 计量比如何解释一种临床相关的、脑区特异性的变构抑制剂的作用机制和亚最大抑制作用。
