Control of neurotransmitter release by two distinctmembrane-binding faces of the Munc13-1 C1C2B region
- Charité-Universitätsmedizin Berlin, Germany
- University of Texas Southwestern Medical Center, United States
- Charité Universitätsmedizin Berlin, Germany
- The University of Texas Southwestern Medical Center, United States
Abstract
Munc13-1 plays a central role in neurotransmitter release through its conserved C-terminal region, which includes a diacyglycerol (DAG)-binding C1 domain, a Ca2+/PIP2-binding C2B domain, a MUN domain and a C2C domain. Munc13-1 was proposed to bridge synaptic vesicles to the plasma membrane through distinct interactions of the C1C2B region with the plasma membrane: i) one involving a polybasic face that is expected to yield a perpendicular orientation of Munc13-1 and hinder release; and ii) another involving the DAG-Ca2+-PIP2-binding face that is predicted to result in a slanted orientation and facilitate release. Here we have tested this model and investigated the role of the C1C2B region in neurotransmitter release. We find that K603E or R769E point mutations in the polybasic face severely impair Ca2+-independent liposome bridging and fusion in in vitro reconstitution assays, and synaptic vesicle priming in primary murine hippocampal cultures. A K720E mutation in the polybasic face and a K706E mutation in the C2B domain Ca2+-binding loops have milder effects in reconstitution assays and do not affect vesicle priming, but enhance or impair Ca2+-evoked release, respectively. The phenotypes caused by combining these mutations are dominated by the K603E and R769E mutations. Our results show that the C1-C2B region of Munc13-1 plays a central role in vesicle priming and support the notion that two distinct faces of this region control neurotransmitter release and short-term presynaptic plasticity.
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Author details
Christian Rosenmund
Funding
National Institute of Neurological Disorders and Stroke (R35 NS097333)
- Josep Rizo
Welch Foundation (I-1304)
- Josep Rizo
German Research Council (958)
- Christian Rosenmund
Reinhart Koselleck project
- Christian Rosenmund
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: Animal Welfare Committee of Charité - Universitätsmedizin Berlin and the Berlin state government agency for Health and Social Services approved all protocols for animal maintenance and experiments (license no. G106/20).
Copyright
© 2021, Camacho 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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Control of neurotransmitter release by two distinctmembrane-binding faces of the Munc13-1 C1C2B region
eLife 10:e72030.
https://doi.org/10.7554/eLife.72030
