EMC chaperone-CaV structure reveals an ion channel assembly intermediate
EMC chaperone-CaV structure reveals an ion channel assembly intermediate
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DOI：
10.1038/s41586-023-06175-5
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发表时间：
2023-05-17
期刊：
影响因子：
64.8
通讯作者：
Minor Jr, Daniel L. L.
中科院分区：
文献类型：
--
作者：
Chen, Zhou;Mondal, Abhisek;Minor Jr, Daniel L. L.
电压门控离子通道（VGIC）包括多个结构单元，其组装是功能（1，2）所必需的。缺乏对VGIC亚基如何组装以及是否需要伴侣蛋白的结构理解。高压激活钙通道（Ca（V）s）（3，4）是典型的多亚基VGIC，其功能和运输由成孔Ca（V）1或Ca（V）2 CaV α（1）（参考文献3）与辅助Ca-V β（5）和Ca-V α（2）δ亚基（6，7）之间的相互作用有力地塑造。在这里，我们展示了人脑和心脏Ca（V）1.2与Ca-V β（3）结合到伴侣-内质网膜蛋白复合物（EMC）（8，9）-以及组装的Ca（V）1.2-Ca-V β（3）-Ca-V α（2）δ-1通道的冷冻电子显微镜结构。这些结构提供了EMC-客户端复合物的视图，并定义了EMC位点-跨膜（TM）和细胞质（Cyto）码头;这些位点和客户端通道之间的相互作用导致孔亚基的部分提取，并打开Ca-V α（2）δ相互作用位点。这些结构确定了加巴喷丁类抗疼痛和抗焦虑药物的Ca-V α（2）δ结合位点（6），表明EMC和Ca-V α（2）δ与通道的相互作用是相互排斥的，并表明EMC到Ca-V α（2）δ的传递涉及二价离子依赖性步骤和Ca（V）1.2元素排序。EMC-Ca-V复合物的破坏损害了Ca-V功能，表明EMC作为促进通道组装的通道保持酶发挥作用。总之，这些结构揭示了Ca-V组装中间体和EMC客户端结合位点，这些位点可能对VGIC和其他膜蛋白的生物发生产生广泛的影响。
Voltage-gated ion channels (VGICs) comprise multiple structural units, the assembly of which is required for function(1,2). Structural understanding of how VGIC subunits assemble and whether chaperone proteins are required is lacking. High-voltage-activated calcium channels (Ca(V)s)(3,4) are paradigmatic multisubunit VGICs whose function and trafficking are powerfully shaped by interactions between pore-forming Ca(V)1 or Ca(V)2 CaV alpha(1) (ref. 3), and the auxiliary Ca-V beta(5) and Ca-V alpha(2)delta subunits(6,7). Here we present cryo-electron microscopy structures of human brain and cardiac Ca(V)1.2 bound with Ca-V beta(3) to a chaperone-the endoplasmic reticulum membrane protein complex (EMC)(8,9)-and of the assembled Ca(V)1.2-Ca-V beta(3)-Ca-V alpha(2)delta-1 channel. These structures provide a view of an EMC-client complex and define EMC sites-the transmembrane (TM) and cytoplasmic (Cyto) docks; interaction between these sites and the client channel causes partial extraction of a pore subunit and splays open the Ca-V alpha(2)delta-interaction site. The structures identify the Ca-V alpha(2)delta-binding site for gabapentinoid anti-pain and anti-anxiety drugs(6), show that EMC and Ca-V alpha(2)delta interactions with the channel are mutually exclusive, and indicate that EMC-to-Ca-V alpha(2)delta hand-off involves a divalent ion-dependent step and Ca(V)1.2 element ordering. Disruption of the EMC-Ca-V complex compromises Ca-V function, suggesting that the EMC functions as a channel holdase that facilitates channel assembly. Together, the structures reveal a Ca-V assembly intermediate and EMC client-binding sites that could have wide-ranging implications for the biogenesis of VGICs and other membrane proteins.