Munc13 supports fusogenicity of non-docked vesicles at synapses with disrupted active zones
- Harvard Mecical School, United States
- Harvard Medical School, United States
- University of Copenhagen, Denmark
- Max Planck Institute for Multidisciplinary Sciences, Germany
Abstract
Active zones consist of protein scaffolds that are tightly attached to the presynaptic plasma membrane. They dock and prime synaptic vesicles, couple them to voltage-gated Ca2+ channels, and direct neurotransmitter release towards postsynaptic receptor domains. Simultaneous RIM+ELKS ablation disrupts these scaffolds, abolishes vesicle docking and removes active zone-targeted Munc13, but some vesicles remain releasable. To assess whether this enduring vesicular fusogenicity is mediated by non-active zone-anchored Munc13 or is Munc13-independent, we ablated Munc13-1 and Munc13-2 in addition to RIM+ELKS in mouse hippocampal neurons. The hextuple knockout synapses lacked docked vesicles, but other ultrastructural features were near-normal despite the strong genetic manipulation. Removing Munc13 in addition to RIM+ELKS impaired action potential-evoked vesicle fusion more strongly than RIM+ELKS knockout by further decreasing the releasable vesicle pool. Hence, Munc13 can support some fusogenicity without RIM and ELKS, and presynaptic recruitment of Munc13, even without active zone-anchoring, suffices to generate some fusion-competent vesicles.
Data availability
All data generated or analyzed in this study, including individual data points, are included in the figures. Source data files for Fig. 1 - figure supplement 3, Fig. 2 - figure supplement 1 and Fig. 2 - figure supplement 2 are provided, and a source data table that contains all means, errors, statistical tests and p-values is also included.
Article and author information
Author details
Funding
National Institute of Mental Health (MH113349)
- Pascal S Kaeser
National Institute of Neurological Disorders and Stroke (NS083898)
- Pascal S Kaeser
Harvard Medical School (NA)
- Pascal S Kaeser
Max Planck Institute for Multidisciplinary Sciences (open access funding)
- Cordelia Imig
- Nils Brose
German Research Foundation (EXC 2067/1-390729940)
- Nils Brose
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: This study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. All animal experiments were approved by the Harvard University Animal Care and Use Committee (protocol number IS00000049).
Copyright
© 2022, Tan 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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Munc13 supports fusogenicity of non-docked vesicles at synapses with disrupted active zones
eLife 11:e79077.
https://doi.org/10.7554/eLife.79077
