Munc18-1-regulated stage-wise SNARE assembly underlying synaptic exocytosis

• Published in: eLife Vol. 4
• Main Authors: Ma, Lu, Rebane, Aleksander A, Yang, Guangcan, Xi, Zhiqun, Kang, Yuhao, Gao, Ying, Zhang, Yongli
• Format: Journal Article
• Language: English
• Published: England eLife Science Publications, Ltd 23.12.2015; eLife Sciences Publications Ltd; eLife Sciences Publications, Ltd
• Subjects: Analysis; Biophysics and Structural Biology; energy landscape; Exocytosis; membrane fusion; Munc18 Proteins - metabolism; munc18-1; Neurons; Optical Tweezers; Protein Multimerization; Proteins; SNARE assembly; SNARE Proteins - metabolism; synaptic exocytosis; energy landscape; SNARE assembly; synaptic exocytosis; optical tweezers; Munc18-1; structural biology; none; biophysics; membrane fusion
• ISSN: 2050-084X; 2050-084X
• DOI: 10.7554/eLife.09580

Synaptic-soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins couple their stage-wise folding/assembly to rapid exocytosis of neurotransmitters in a Munc18-1-dependent manner. The functions of the different assembly stages in exocytosis and the role of Munc18-1 in SNARE assembly are not well understood. Using optical tweezers, we observed four distinct stages of assembly in SNARE N-terminal, middle, C-terminal, and linker domains (or NTD, MD, CTD, and LD, respectively). We found that SNARE layer mutations differentially affect SNARE assembly. Comparison of their effects on SNARE assembly and on exocytosis reveals that NTD and CTD are responsible for vesicle docking and fusion, respectively, whereas MD regulates SNARE assembly and fusion. Munc18-1 initiates SNARE assembly and structures t-SNARE C-terminus independent of syntaxin N-terminal regulatory domain (NRD) and stabilizes the half-zippered SNARE complex dependent upon the NRD. Our observations demonstrate distinct functions of SNARE domains whose assembly is intimately chaperoned by Munc18-1.