PDF(Pubmed)
Abstract：
Tomosyns are widely thought to attenuate membrane fusion by competing with synaptobrevin-2/VAMP2 for SNARE-complex assembly. Here, we present evidence against this scenario. In a novel mouse model, tomosyn-1/2 deficiency lowered the fusion barrier and enhanced the probability that synaptic vesicles fuse, resulting in stronger synapses with faster depression and slower recovery. While wild-type tomosyn-1m rescued these phenotypes, substitution of its SNARE motif with that of synaptobrevin-2/VAMP2 did not. Single-molecule force measurements indeed revealed that tomosyn\'s SNARE motif cannot substitute synaptobrevin-2/VAMP2 to form template complexes with Munc18-1 and syntaxin-1, an essential intermediate for SNARE assembly. Instead, tomosyns extensively bind synaptobrevin-2/VAMP2-containing template complexes and prevent SNAP-25 association. Structure-function analyses indicate that the C-terminal polybasic region contributes to tomosyn\'s inhibitory function. These results reveal that tomosyns regulate synaptic transmission by cooperating with synaptobrevin-2/VAMP2 to prevent SNAP-25 binding during SNARE assembly, thereby limiting initial synaptic strength and equalizing it during repetitive stimulation.
摘要：
人们普遍认为，Tomosyns通过与突触蛋白2/VAMP2竞争SNARE复合物组装来减弱膜融合。这里,我们提出了反对这种情况的证据。在一个新的小鼠模型中，tomosyn-1/2缺乏降低了融合屏障并增强了突触小泡融合的可能性，导致更强的突触，更快的抑郁和更慢的恢复。虽然野生型tomosyn-1m拯救了这些表型，用突触蛋白2/VAMP2取代其SNARE基序。单分子力测量确实表明，tomosyn的SNARE基序不能替代突触短蛋白2/VAMP2与Munc18-1和syntaxin-1形成模板复合物，Munc18-1和syntaxin-1是SNARE组装的重要中间体。相反，Tomosyns广泛结合含有突触短蛋白2/VAMP2的模板复合物并防止SNAP-25缔合。结构功能分析表明，C末端的多碱区有助于番茄的抑制功能。这些结果表明，在SNARE组装过程中，Tomosyns通过与突触短蛋白2/VAMP2合作来调节突触传递，以防止SNAP-25结合。从而限制初始突触强度并在重复刺激期间使其均衡。
