A VAMP-Binding Protein from Aplysia Required for Neurotransmitter Release

Before the fusion of synaptic vesicles with the plasma membrane, a protein complex is thought to form between VAMP—an integral membrane protein of the vesicle—and two proteins associated with the plasma membrane, SNAP-25 and syntaxin. The yeast two-hybrid interaction cloning system has now been used to identify additional proteins from Aplysia that interact directly with VAMP. A 33-kilodalton membrane protein, termed VAP-33 (VAMP-associated protein of 33 kilodaltons), was identified whose corresponding messenger RNA was detected only in the central nervous system and the gill of Aplysia . Presynaptic injection of antibodies specific for VAP-33 inhibited synaptic transmission, which suggests that VAP-33 is required for the exocytosis of neurotransmitter.