Regulated SNARE Folding/Assembly and Membrane Fusion

Dec 19, 2016
Speaker: Yongli Zhang, Associate Professor, Department of Cell Biology, Yale University School of Medicine


All actions and thinking depend on delicate machinery at synapses that release neurotransmitters with extremely high speed and precision. Core components of the release machinery include SNARE proteins, Munc18-1, and synaptotagmin (Syt). SNAREs couple their stage-wise folding and assembly to synaptic vesicle fusion like a zipper, and Munc18-1 and Syt regulate the SNARE assembly. How these components work together to achieve the high speed and precision required for neurotransmission remain unclear. Using high-resolution optical tweezers, we demonstrate that SNAREs zipper stage-wise with distinct kinetics. We directly observed four stages of assembly in SNARE N-terminal, middle, C-terminal, and linker domains (or NTD, MD, CTD and LD, respectively). Results of layer mutations suggest that NTD and CTD are responsible for vesicle docking and fusion, respectively, whereas MD regulates SNARE assembly and fusion. Munc18-1 intimately regulates SNARE assembly by initiating SNARE assembly and stabilizing the half-zippered SNARE complex. Our observations clarify the distinct functions of SNARE domains and the essential role of Munc18-1 in synaptic exocytosis. We also developed novel assays to study membrane protein folding and stability based on optical tweezers.

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