Lu Wenbo, Ma Huan, Sheng Zu-Hang, Mochida Sumiko
Department of Neurobiology, School of Medicine, Shanghai Jiao Tong University, Shanghai 200025, China.
J Biol Chem. 2009 Jan 16;284(3):1930-7. doi: 10.1074/jbc.M803691200. Epub 2008 Nov 14.
Neurotransmission in central neuronal synapses is supported by the recycling of synaptic vesicles via endocytosis at different time scales during and after transmitter release. Here, we examine the kinetics and molecular determinants of different modes of synaptic vesicle recycling at a peripheral neuronal synapse formed between superior cervical ganglion neurons in culture, via acute disruption of endocytosis with Dynasore, an inhibitor of dynamin activation, or a dynamin peptide (P4) that perturbs linkage of dynamin to clathrin coats through amphiphysin. When paired action potentials are generated to produce excitatory postsynaptic potential responses, the second response was reduced after application of Dynasore but not P4. In addition, graded reduction in synaptic transmission during a train of action potentials was accelerated by Dynasore but enhanced by P4. After full depletion of releasable vesicles, P4 delayed the recovery of synaptic transmission while Dynasore limited recovery to 10%. In control neurons, synaptic transmission is stable for more than 1 h under low frequency presynaptic stimulation (0.2 Hz), but was reduced gradually by P4 and rapidly but incompletely blocked by Dynasore at a much lower stimulation frequency. These results suggest two essential modes of dynamin-mediated synaptic vesicle recycling, one activity-dependent and the other activity-independent. Our findings extend the current understanding of synaptic vesicle recycling to sympathetic nerve terminals and provide evidence for a physiological and molecular heterogeneity in endocytosis, a key cellular process for efficient replenishment of the vesicle pool, and thus for synaptic plasticity.
中枢神经元突触中的神经传递是通过在递质释放期间及之后的不同时间尺度上，通过内吞作用对突触小泡进行循环利用来支持的。在这里，我们通过用发动蛋白激活抑制剂Dynasore或一种发动蛋白肽（P4）急性破坏内吞作用，研究了培养的颈上神经节神经元之间形成的外周神经元突触处突触小泡循环利用不同模式的动力学和分子决定因素，该肽通过发动蛋白与网格蛋白包被的衔接蛋白扰乱发动蛋白与网格蛋白包被的连接。当产生成对动作电位以产生兴奋性突触后电位反应时，应用Dynasore后第二个反应降低，但P4处理后没有降低。此外，在一串动作电位期间突触传递的分级降低被Dynasore加速，但被P4增强。在可释放小泡完全耗尽后，P4延迟了突触传递的恢复，而Dynasore将恢复限制在10%。在对照神经元中，在低频突触前刺激（0.2 Hz）下突触传递稳定超过1小时，但在低得多的刺激频率下，P4使其逐渐降低，Dynasore使其迅速但不完全阻断。这些结果提示了发动蛋白介导的突触小泡循环利用的两种基本模式，一种是活动依赖性的，另一种是活动独立性的。我们的发现将目前对突触小泡循环利用的理解扩展到交感神经末梢，并为内吞作用中的生理和分子异质性提供了证据，内吞作用是有效补充小泡池的关键细胞过程，因此也是突触可塑性的关键过程。
