Synaptotagmin-1–, Munc18-1–, and Munc13-1–dependent liposome fusion with a few neuronal SNAREs
Karolina P. Stepien, Josep Rizo
Abstract
Significance Neurotransmitter release is crucial for neuronal communication. Reproducing the steps that lead to neuronal exocytosis with lipid vesicles and purified proteins provides a powerful strategy to elucidate the molecular mechanisms underlying release. Previous studies showed that reconstitution experiments including Munc18-1, Munc13-1, NSF, α-SNAP, and the SNARE proteins synaptobrevin, syntaxin-1, and SNAP-25, all of which are critical for neurotransmitter release, led to highly efficient vesicle fusion. However, synaptotagmin-1, the Ca 2+ sensor that triggers release, did not have detectable effects in these fusion assays. We now show that, when the amounts of synaptobrevin and syntaxin-1 are lowered in otherwise analogous reconstitution experiments, vesicle fusion is strongly dependent on synaptotagmin-1, exhibiting several features that parallel those of neurotransmitter release in neurons.