Munc13 activates the Munc18-1/syntaxin-1 complex and enables Munc18-1 to primeSNAREassembly
Munc13 activates the Munc18-1/syntaxin-1 complex and enables Munc18-1 to primeSNAREassembly
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Munc13 激活 Munc18-1/syntaxin-1 复合物，并使 Munc18-1 结构域 3a 启动 SNARE 组装
DOI：
10.15252/embj.2019103631
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发表时间：
2020-07-09
期刊：
影响因子：
11.4
通讯作者：
Ma, Cong
中科院分区：
文献类型：
--
作者：
Wang, Xianping;Gong, Jihong;Ma, Cong
突触囊泡的启动涉及Munc 13催化的Munc 18 -1/syntaxin-1复合物在SNAP-25和小突触泡蛋白-2的存在下向SNARE复合物的转变; Munc 13通过MUN结构域驱动syntaxin-1的开放，而Munc 18 -1通过结构域3a启动SNARE组装。然而，其潜在机制仍不清楚。在这项研究中，我们已经确定了Munc 18 -1的结构域3a中的一些残基，这些残基对Munc 13和Munc 18 -1在SNARE复合物组装和突触小泡引发中的作用至关重要。我们的研究结果表明，结构域3a侧的两个残基（Q301/K308）介导Munc 18 -1/syntaxin-1复合物与MUN结构域之间的相互作用。这种相互作用使MUN结构域能够驱动突触融合蛋白-1连接区的开放，从而导致结构域3a的延伸并促进突触泡蛋白-2的结合。此外，我们在结构域3a的底部鉴定了两个残基（K332/K333），它们介导Munc 18 -1与syntaxin-1的SNARE基序之间的相互作用。这种相互作用确保了Munc 18 -1在syntaxin-1从封闭到开放的构象变化过程中与syntaxin-1持续缔合，从而加强了Munc 18 -1在模板化SNARE组装中的作用。综上所述，我们的数据表明Munc 13激活Munc 18 -1/syntaxin-1复合物并使Munc 18 -1启动SNARE组装的机制。
Priming of synaptic vesicles involves Munc13-catalyzed transition of the Munc18-1/syntaxin-1 complex to theSNAREcomplex in the presence ofSNAP-25 and synaptobrevin-2; Munc13 drives opening of syntaxin-1 via theMUNdomain while Munc18-1 primesSNAREassembly via domain 3a. However, the underlying mechanism remains unclear. In this study, we have identified a number of residues in domain 3a of Munc18-1 that are crucial for Munc13 and Munc18-1 actions inSNAREcomplex assembly and synaptic vesicle priming. Our results showed that two residues (Q301/K308) at the side of domain 3a mediate the interaction between the Munc18-1/syntaxin-1 complex and theMUNdomain. This interaction enables theMUNdomain to drive the opening of syntaxin-1 linker region, thereby leading to the extension of domain 3a and promoting synaptobrevin-2 binding. In addition, we identified two residues (K332/K333) at the bottom of domain 3a that mediate the interaction between Munc18-1 and theSNAREmotif of syntaxin-1. This interaction ensures Munc18-1 to persistently associate with syntaxin-1 during the conformational change of syntaxin-1 from closed to open, which reinforces the role of Munc18-1 in templatingSNAREassembly. Taken together, our data suggest a mechanism by which Munc13 activates the Munc18-1/syntaxin-1 complex and enables Munc18-1 to primeSNAREassembly.