Molecular mechanisms of synaptic vesicle trafficking.

摘要

In this thesis I explore some of the most fundamental, yet mysterious aspects of neuronal function- the mechanisms behind regulating neurotransmission. The means by which a select group of synaptic vesicles is recruited to be released and then recycled successfully were investigated by using real-time imaging in live hippocampal neurons.; By visualizing the dynamics of two Rab proteins thought to be involved in regulating vesicle recycling, we find that these proteins, Rab3a and Rab5, have divergent functions. Specifically we propose that Rab3a preferentially associates with recycling vesicles, and Rab 5 with reserve vesicles. Previous to our experiments, there was only one protein, syntaxin, which was suggested to selectively associate with a particular population of vesicles. Our studies revealed two new candidates.; The reformation of synaptic vesicles through clathrin-mediated endocytosis has been a well investigated and accepted means of vesicle recycling. The large GTPase dynamin is required for the final scission step of vesicle formation through this pathway. Nevertheless, the ongoing controversy over the existence of other modes of endocytosis also brings into question whether dynamin has a universal role in vesicle recapture. By using a newly identified small molecule inhibitor of dynamin function called dynasore, we showed that dynamin is required for all forms of compensatory synaptic vesicle endocytosis.; These experiments help provide unique insight into some of the molecular components involved in presynaptic function, and hopefully help resolve some current controversies in the importance of these mechanisms.