title: Munc18-1-regulated stage-wise SNARE assembly underlying synaptic exocytosis.
abstract: 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.
authors.affiliation: Department of Cell Biology, Yale School of Medicine, New Haven, United States.
authors.forename: Lu
authors.initials: L
authors.lastname: Ma
authors.affiliation: Department of Cell Biology, Yale School of Medicine, New Haven, United States.|Integrated Graduate Program in Physical and Engineering Biology, Yale University, New Haven, United States.|Department of Physics, Yale University, New Haven, United States.
authors.forename: Aleksander A
authors.initials: AA
authors.lastname: Rebane
authors.affiliation: Department of Cell Biology, Yale School of Medicine, New Haven, United States.|Department of Physics, Wenzhou University, Wenzhou, China.
authors.forename: Guangcan
authors.initials: G
authors.lastname: Yang
authors.affiliation: Department of Cell Biology, Yale School of Medicine, New Haven, United States.
authors.forename: Zhiqun
authors.initials: Z
authors.lastname: Xi
authors.affiliation: Department of Cell Biology, Yale School of Medicine, New Haven, United States.
authors.forename: Yuhao
authors.initials: Y
authors.lastname: Kang
authors.affiliation: Department of Cell Biology, Yale School of Medicine, New Haven, United States.
authors.forename: Ying
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Department of Cell Biology, Yale School of Medicine, New Haven, United States.
authors.forename: Yongli
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D005089:Exocytosis; D051938:Munc18 Proteins / Q000378:metabolism*; D052898:Optical Tweezers; D055503:Protein Multimerization; D050600:SNARE Proteins / Q000378:metabolism*
chemical_list: D051938:Munc18 Proteins; D050600:SNARE Proteins
keywords: Munc18-1; SNARE assembly; biophysics; energy landscape; membrane fusion; none; optical tweezers; structural biology; synaptic exocytosis