EVIDENCE THAT SYNAPTOBREVIN IS INVOLVED IN FUSION BETWEEN SYNAPTIC VESICLES AND SYNAPTIC PLASMA-MEMBRANE VESICLES

We have developed a model system, consisting of rat brain synaptic ves icles and rat brain synaptic plasma membrane vesicles, to study the fu sion process associated with the exocytotic release of neurotransmitte rs. Our results show a significant increase in the extent of fusion wh en the reaction takes place in cytosol compared to that obtained when fusion is carried out in buffer. This effect is mediated by cytosolic proteins, although N-ethylmaleimide-sensitive factor does not play a r ole in fusion. We also registered an almost complete inhibition of fus ion when synaptic vesicles were pre-incubated with botulinum toxin B, indicating that synaptobrevin plays an important role in the coalescen ce of membrane lipids of the interacting membranes. (C) 1997 Academic Press.