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Published on: January 14, 2018
Munc18-1 binding to the neuronal SNARE complex controls synaptic vesicle priming.
Ferenc Deák1, Yi Xu, Wen-Pin Chang
1Howard Hughes Medical Institute, Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
The Journal of Cell Biology
|March 4, 2009
Summary
Munc18-1 protein is crucial for synaptic vesicle priming, a key step in neurotransmission. This study reveals how Munc18-1 binding to SNARE complexes facilitates priming, independent of Ca(2+)-triggered fusion.
Area of Science:
- Neuroscience
- Molecular Biology
- Cell Biology
Background:
- Munc18-1 and SNAREs are essential for synaptic vesicle fusion.
- Munc18-1 interacts with syntaxin-1 in both closed and open conformations.
- Understanding Munc18-1's role in SNARE complex binding is key to elucidating fusion mechanisms.
Purpose of the Study:
- To investigate the specific role of Munc18-1 binding to open syntaxin-1 in SNARE complexes.
- To determine if Munc18-1 competes with complexins for SNARE complex binding.
- To elucidate the precise step in synaptic vesicle fusion mediated by Munc18-1.
Main Methods:
- Lentiviral expression of Munc18-1 in knockout mice.
- Site-directed mutagenesis of Munc18-1 to disrupt binding to open syntaxin-1.
- Synaptic vesicle fusion and priming assays.
- Co-immunoprecipitation to assess Munc18-1 and complexin-1 binding.
Main Results:
- Lentiviral Munc18-1 expression rescued release defects in knockout mice.
- Mutations disrupting Munc18-1 binding to open syntaxin-1 selectively impaired vesicle priming.
- Ca(2+)-triggered fusion of already primed vesicles was unaffected.
- Munc18-1 and complexin-1 were found to bind simultaneously to SNARE complexes.
Conclusions:
- Munc18-1 binding to SNARE complexes is critical for synaptic vesicle priming.
- The primed state involves a Munc18-1-SNARE-complexin assembly poised for fusion.
- This work clarifies Munc18-1's distinct roles in priming versus Ca(2+)-triggered fusion.
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