SNAP-25 and syntaxin, but not synaptobrevin 2, cooperate in the regulated release of nerve growth factor

Investigating the release mechanism of nerve growth factor (NGF) the possible cooperation of SNAREs (target (t)- and vesicular (v)- soluble NSF attachment protein receptors) which form a fusion core during docking of synaptic vesicles at the plasma membrane was examined. Cleavage of those proteins by clostridium toxins shows that SNAP-25 (synaptic vesicle associated protein) and syntaxin are involved but not synaptobrevin 2. Alpha-latrotoxin, which effects the release of neurotransmitters by acting on the fusion core, also induces Ca2+-independent NGF release. Taken together, the results indicate the formation of a fusion core during regulated NGF release and implicate the existence of NGF vesicles.