Munc18-1 catalyzes neuronal SNARE assembly by templating SNARE association
- Yale University School of Medicine, United States
- Princeton University, United States
Abstract
Sec1/Munc18-family (SM) proteins are required for SNARE-mediated membrane fusion, but their mechanism(s) of action remain controversial. Using single-molecule force spectroscopy, we found that the SM protein Munc18-1 catalyzes step-wise zippering of three synaptic SNAREs (syntaxin, VAMP2, and SNAP-25) into a four-helix bundle. Catalysis requires formation of an intermediate template complex in which Munc18-1 juxtaposes the N-terminal regions of the SNARE motifs of syntaxin and VAMP2, while keeping their C-terminal regions separated. SNAP-25 binds the templated SNAREs to induce full SNARE zippering. Munc18-1 mutations modulate the stability of the template complex in a manner consistent with their effects on membrane fusion, indicating that chaperoned SNARE assembly is essential for exocytosis. Two other SM proteins, Munc18-3 and Vps33, similarly chaperone SNARE assembly via a template complex, suggesting that SM protein mechanism is conserved.
Data availability
All data generated or analyzed during this study are included in the manuscript and supporting files. Source data files have been provided for Figures 2-10.
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Author details
Funding
National Institute of General Medical Sciences (R01GM093341)
- Yongli Zhang
National Institute of General Medical Sciences (R01GM120193)
- Yongli Zhang
National Institute of General Medical Sciences (R01GM071574)
- Frederick M Hughson
National Institute of General Medical Sciences (T32GM007223)
- Junyi Jiao
Deutsche Forschungsgemeinschaft (PO2195/1-1)
- Sarah A Port
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2018, Jiao et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Munc18-1 catalyzes neuronal SNARE assembly by templating SNARE association
eLife 7:e41771.
https://doi.org/10.7554/eLife.41771
