Homotypic vacuolar fusion mediated by t- and v-SNAREs
Homotypic vacuolar fusion mediated by t- and v-SNAREs
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DOI：
10.1038/387199a0
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发表时间：
1997-05-08
期刊：
影响因子：
64.8
通讯作者：
Haas, A
中科院分区：
文献类型：
--
作者：
Nichols, BJ;Ungermann, C;Haas, A
膜融合在真核分泌途径和细胞周期中细胞器的遗传中都是必需的。在分泌途径中，小的运输囊泡和细胞器之间发生异型融合。它需要N-乙基马来酰亚胺敏感性融合蛋白（NSF/Sec 18 p）、可溶性NSF附着蛋白（SNAP/Sec 17 p）和SNAP受体（SNARE）。SNARE是整合的膜蛋白（囊泡上的v-SNARE，靶细胞器上的t-SNARE），并被认为为融合过程提供特异性（1-5）。已经表明Sec 17 p和Sec 18 p与v-SNARE/t-SNARE复合物结合并介导膜融合事件（1-3）。酵母空泡的同型融合也需要Sec 17 p和Sec 18 p（参考文献6），但在体外，它们仅用于“启动”空泡，而不是用于随后的对接或融合（7，8）。目前尚不清楚这些反应是否涉及与之前在异型融合系统中鉴定的SNARE相似的SNARE，因此，是否可以比较Sec 18 p/NSF和Sec 17 p/alpha SNAP在这些系统中的作用。在这里，我们鉴定了典型的v-和t-SNARE酵母液泡膜上，尽管两者通常都存在，仅含有v-SNARE的液泡可以与仅含有t-SNARE的液泡融合。两个SNARE都不含的分子不能与两个都含的分子融合，这表明对接是由两个细胞器膜上的同源SNARE介导的。即使t-和v-SNARE在不同的膜上，Sec 17 p和Sec 18 p也在引发阶段起作用。在SNARE复合体的组装点上不需要它们的作用，也不需要它们的作用用于融合事件本身。
Membrane fusion is necessary both in the eukaryotic secretory pathway and for the inheritance of organelles during the cell cycle. In the secretory pathway, heterotypic fusion takes place between small transport vesicles and organelles. It requires N-ethylmaleimide-sensitive fusion protein (NSF/Sec18p), soluble NSF attachment proteins (SNAPs/Sec17p) and SNAP receptors (SNAREs). SNAREs are integral membrane proteins (v-SNAREs on vesicles, t-SNAREs on the target organelles) and are thought to provide specificity to the fusion process(1-5). It has been suggested that Sec17p and Sec18p bind to v-SNARE/t-SNARE complexes and mediate the membrane fusion event(1-3). Homotypic fusion of yeast vacuoles also requires Sec17p and Sec18p (ref, 6), but in vitro they are needed only to 'prime' the vacuoles, not for subsequent docking or fusion(7,8). It has been unclear whether these reactions involve SNAREs that are similar to those previously identified in heterotypic fusion systems and, hence, whether the actions of Sec18p/NSF and Sec17p/alpha SNAP in these systems can be compared, Here we identify typical v- and t-SNAREs on the yeast vacuolar membrane, Although both are normally present, vacuoles containing only the v-SNARE can fuse with those containing only the t-SNARE. Vacuoles containing neither SNARE cannot fuse with those containing both, demonstrating that docking is mediated by cognate SNAREs on the two organelle membranes. Even when t- and v-SNAREs are on separate membranes, Sec17p and Sec18p act at the priming stage. Their action is not required at the point of assembly of the SNARE complex, nor for the fusion event itself.