SNAP-MEDIATED PROTEIN-PROTEIN INTERACTIONS ESSENTIAL FOR NEUROTRANSMITTER RELEASE

The constitutive fusion of transport vesicles with intracellular membr anes requires soluble proteins called SNAPs(1). Certain presynaptic pr oteins(2-4) implicated in synaptic vesicle exocytosis(5) also bind SNA Ps, suggesting that SNAPs participate in the calcium-regulated membran e fusion events mediating neurotransmitter release(6,7). Here we show that injection of recombinant SNAPs into the giant synapse of squid en hances transmitter release. Conversely, injection of peptides designed to mimic the sites at which SNAP interacts with its binding partners inhibits transmitter release downstream of synaptic vesicle docking. A SNAP-dependent protein complex must therefore mediate transmitter rel ease, showing that transmitter release shares a common molecular mecha nism with constitutive membrane fusion.