Tomosyn Inhibits Synaptotagmin-1-mediated Step of Ca2+-dependent Neurotransmitter Release through Its N-terminal WD40 Repeats*
Tomosyn Inhibits Synaptotagmin-1-mediated Step of Ca2+-dependent Neurotransmitter Release through Its N-terminal WD40 Repeats*
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DOI：
10.1074/jbc.m110.156893
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发表时间：
2010-10
期刊：
影响因子：
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通讯作者：
Yasunori Yamamoto;S. Mochida;N. Miyazaki;K. Kawai;Kohei Fujikura;Takao Kurooka;K. Iwasaki;T. Sakisaka
中科院分区：
文献类型：
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作者：
Yasunori Yamamoto;S. Mochida;N. Miyazaki;K. Kawai;Kohei Fujikura;Takao Kurooka;K. Iwasaki;T. Sakisaka
神经递质的释放是由Ca 2+结合到低亲和力的Ca 2+传感器（主要是synaptotagmin-1）触发的，后者催化SNARE介导的突触囊泡融合。Tomosyn通过C-末端VAMP样结构域螯合靶SNARE来负调节Ca 2+依赖性神经递质释放。除了C末端，N-末端WD 40重复的tomosyn也有强大的抑制活性对Ca 2+依赖性神经递质的释放，虽然这种效果的分子机制仍然难以捉摸。在这里，我们表明，通过其N-末端WD 40重复tomosyn直接结合到突触结合蛋白-1的钙离子依赖性的方式。N-末端WD 40重复序列损害了突触结合蛋白-1促进SNARE复合物介导的膜融合和弯曲脂质双层的活性。N-末端WD 40重复显微注射的上级颈神经节神经元的乙酰胆碱释放减少，通过显微注射突触结合蛋白-1的胞质结构域得到缓解。这些结果表明，在直接结合，N-末端WD 40重复负调节突触结合蛋白-1介导的步骤的Ca 2+依赖性神经递质释放。此外，我们表明，synaptotagmin-1结合增强了目标陷阱螯合活性的tomosyn。这些结果表明，tomosyn和synaptotagmin-1之间的相互作用的基础上抑制控制钙依赖性神经递质的释放。
Neurotransmitter release is triggered by Ca2+ binding to a low affinity Ca2+ sensor, mostly synaptotagmin-1, which catalyzes SNARE-mediated synaptic vesicle fusion. Tomosyn negatively regulates Ca2+-dependent neurotransmitter release by sequestering target SNAREs through the C-terminal VAMP-like domain. In addition to the C terminus, the N-terminal WD40 repeats of tomosyn also have potent inhibitory activity toward Ca2+-dependent neurotransmitter release, although the molecular mechanism underlying this effect remains elusive. Here, we show that through its N-terminal WD40 repeats tomosyn directly binds to synaptotagmin-1 in a Ca2+-dependent manner. The N-terminal WD40 repeats impaired the activities of synaptotagmin-1 to promote SNARE complex-mediated membrane fusion and to bend the lipid bilayers. Decreased acetylcholine release from N-terminal WD40 repeat-microinjected superior cervical ganglion neurons was relieved by microinjection of the cytoplasmic domain of synaptotagmin-1. These results indicate that, upon direct binding, the N-terminal WD40 repeats negatively regulate the synaptotagmin-1-mediated step of Ca2+-dependent neurotransmitter release. Furthermore, we show that synaptotagmin-1 binding enhances the target SNARE-sequestering activity of tomosyn. These results suggest that the interplay between tomosyn and synaptotagmin-1 underlies inhibitory control of Ca2+-dependent neurotransmitter release.