Pavlos Nathan J, Jahn Reinhard
Department of Neurobiology; Max-Planck Institute for Biophysical Chemistry; Göttingen, Germany.
Small GTPases. 2011 Mar;2(2):77-81. doi: 10.4161/sgtp.2.2.15201.
Exo-endocytotic cycling of synaptic vesicles (SVs) is one of the most intensely studied membrane trafficking pathways. It is governed by sets of conserved proteins including Rab GTPases. Long considered to define the identity and composition of a subcellular organelle, it has become increasingly evident that multiple Rabs co-exist on intracellular compartments, each contributing to its membrane organization and specialised function. Indeed, we have recently demonstrated that at least 11 distinct Rab proteins co-exist on highly purified SVs. These include Rabs involved in exocytosis (Rab3a/b/c and Rab27b) and intermediates of SV recycling such as early endosomes (Rab4, Rab5, Rab10, Rab11b and Rab14). Interestingly, we found that while two of these proteins, namely Rab3a and Rab27b, exhibited differential cycling dynamics on SV membranes; they played complementary roles during Ca(2+)-triggered neurotransmitter release. The implications of these findings in the SV trafficking cycle are discussed.
突触小泡（SVs）的胞吐-内吞循环是研究最为深入的膜运输途径之一。它由包括Rab GTP酶在内的一系列保守蛋白调控。长期以来，人们认为Rab蛋白决定亚细胞器的身份和组成，但越来越明显的是，多种Rab蛋白共存于细胞内区室，每种Rab蛋白都对其膜组织和特定功能有贡献。事实上，我们最近证明，至少11种不同的Rab蛋白共存于高度纯化的突触小泡上。这些包括参与胞吐作用的Rab蛋白（Rab3a/b/c和Rab27b）以及突触小泡回收的中间体，如早期内体（Rab4、Rab5、Rab10、Rab11b和Rab14）。有趣的是，我们发现其中两种蛋白，即Rab3a和Rab27b，在突触小泡膜上表现出不同的循环动力学；它们在Ca(2+)触发的神经递质释放过程中发挥互补作用。本文讨论了这些发现对突触小泡运输循环的影响。
