Botulinum toxin type A inhibits Ca2+-dependent transport of acetylcholine in reconstituted giant liposomes made from presynaptic membranes from cholinergic nerve terminals

Abstract Giant liposomes were made from a mixture of asolectin phospholipid vesicles and presynaptic plasma membranes isolated from Torpedo cholinergic nerve; endings. Acetylcholine filled giant liposomes were able to release neurotransmitter upon stimulation by the Ca 2+ ionophore A23187 and Ca 2+ . Botulinum neurotoxin type A inhibited this Ca 2+ -dependent acetylcholine transport. Additionally, Botulinum toxin type A decreased membrane fluidity of liposomes. These results suggest that Botulinum toxin can interact directly with components of the presynaptic plasma membrane and inhibit acetylcholine translocation. Furthermore, since the reconstituted liposomes do not have synaptic vesicle components, the observed effects may account for the action of Botulinum toxin on the non-quantal release of acetylcholine from motor nerve terminals.