Matteoli M, Takei K, Cameron R, Hurlbut P, Johnston P A, Südhof T C, Jahn R, De Camilli P
Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510.
J Cell Biol. 1991 Nov;115(3):625-33. doi: 10.1083/jcb.115.3.625.
Rab3A is a small GTP-binding protein highly concentrated on synaptic vesicles. Like other small GTP-binding proteins it is thought to cycle between a soluble and a membrane-associated state. To determine at which stage of the life cycle of synaptic vesicles rab3A is associated with their membranes, the localization of the protein in neurons and neuroendocrine cells at different developmental and functional stages was investigated. In all cases, rab3A was colocalized with synaptic vesicle markers at the cell periphery, but was absent from the Golgi area, suggesting that rab3A associates with vesicles distally to the Golgi complex and dissociates from vesicle membranes before they recycle to this region. Immunofluorescence experiments carried out on frog motor end plates demonstrated that massive exocytosis of synaptic vesicles is accompanied by a translocation of rab3A to the cell surface. The selective localization of rab3A on synaptic vesicles at stages preceding their fusion with the plasmalemma suggests that the protein is part of a regulatory machinery that is assembled onto the vesicles in preparation for exocytosis.
Rab3A是一种高度集中于突触小泡的小GTP结合蛋白。与其他小GTP结合蛋白一样，它被认为在可溶状态和膜相关状态之间循环。为了确定在突触小泡生命周期的哪个阶段rab3A与它们的膜相关联，研究了该蛋白在不同发育和功能阶段的神经元和神经内分泌细胞中的定位。在所有情况下，rab3A在细胞周边与突触小泡标记物共定位，但在高尔基体区域不存在，这表明rab3A在高尔基体复合体远端与小泡相关联，并在小泡循环回到该区域之前从小泡膜上解离。在青蛙运动终板上进行的免疫荧光实验表明，突触小泡的大量胞吐作用伴随着rab3A向细胞表面的转位。Rab3A在突触小泡与质膜融合之前的阶段在突触小泡上的选择性定位表明，该蛋白是一种调节机制的一部分，该机制在小泡上组装以准备胞吐作用。
