Recent studies suggest that spontaneous and action potential-evoked neurotransmitter release processes are independently regulated. However, the mechanisms that uncouple the two forms of neurotransmission remain unclear. In cultured mouse and rat neurons, we show that the two C2 domain-containing protein copine-6 is localized to presynaptic terminals and binds to synaptobrevin2 as well as other SNAREproteins inaCa2+-dependent manner. Ca2+-dependent interaction of copine-6with synap to brevin 2 selectively suppresses spontaneous neuro transmission in a reaction that requires the tandem tryptophan residues at the C-terminal region of synaptobrevin2. Accordingly, copine-6 loss of function augmented presynaptic Ca2+ elevation-mediated neurotransmitter release. Intracellular Ca2+ chelation, on the other hand, occluded copine-6-mediated suppression of release. We also evaluated the molecular specificity of the copine-6-dependent regulation of spontaneous release and found that overexpression of copine-6 did not suppress spontaneous release in synaptobrevin2-deficient neurons. Together, these results suggest that copine-6 acts as a specific Ca2+-dependent suppressor of spontaneous neurotransmission.
- Calcium regulation of release
- Spontaneous neurotransmission
- Synaptic vesicle fusion
ASJC Scopus subject areas