Synaptic vesicles in the brain harbor several soluble N-ethylmaleimide-sensitive-factor attachment protein receptor (SNARE) proteins. With the exception of synaptobrevin2, or VAMP2 (syb2), which is directly involved in vesicle fusion, the role of these SNAREs in neurotransmission is unclear. Here we show that in mice syb2 drives rapid Ca2+-dependent synchronous neurotransmission, whereas the structurally homologous SNARE protein VAMP4 selectively maintains bulk Ca2+-dependent asynchronous release. At inhibitory nerve terminals, up- or downregulation of VAMP4 causes a correlated change in asynchronous release. Biochemically, VAMP4 forms a stable complex with SNAREs syntaxin-1 and SNAP-25 that does not interact with complexins or synaptotagmin-1, proteins essential for synchronous neurotransmission. Optical imaging of individual synapses indicates that trafficking of VAMP4 and syb2 show minimal overlap. Taken together, these findings suggest that VAMP4 and syb2 diverge functionally, traffic independently and support distinct forms of neurotransmission. These results provide molecular insight into how synapses diversify their release properties by taking advantage of distinct synaptic vesicle–associated SNAREs.
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We thank J. Leitz for technical assistance and H. Kramer, L. Monteggia, E. Nelson and E. Nosyreva for advice and discussions. We also thank T.C. Südhof (Stanford University) for the gift of synaptobrevin2 knockout mice and M.C. Wilson (University of New Mexico) for the gift of SNAP-25 knockout mice. This work was supported by grants from the US National Institute of Mental Health to E.T.K. (MH066198). E.T.K. is an established investigator of the American Heart Association.
The authors declare no competing financial interests.
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Raingo, J., Khvotchev, M., Liu, P. et al. VAMP4 directs synaptic vesicles to a pool that selectively maintains asynchronous neurotransmission. Nat Neurosci 15, 738–745 (2012). https://doi.org/10.1038/nn.3067
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