CHARACTERIZATION OF PRESYNAPTIC PROTEINS INVOLVED IN SYNAPTIC VESICLEEXOCYTOSIS IN THE NERVOUS-SYSTEM OF TORPEDO-MARMORATA

Synaptobrevin, SNAP-25 and syntaxin (SNAP receptor proteins) are molec ular components that play a key role in the exocytotic machinery of sy naptic vesicles. Their presence, distribution and interactions are rep orted in central and peripheral nervous systems of the electric fish T orpedo marmorata. These three proteins form a protein complex in all t he nervous system regions tested, including the electric lobe and the electric organ which is innervated by pure cholinergic nerve terminals . Immunoblot analysis revealed a double protein pattern of SNAP-25 in the anterior brain and cerebellum, although a single protein band corr esponding to SNAP-25 was observed in the electromotor system. Moreover , SNAP-25 showed a differential distribution in the electromotor syste m. It was present along nerve fibres and terminals that innervated the electric organ but it was not detected in nerve terminals at the elec tric lobe. Immunoisolation experiments using anti-synaptobrevin antibo dies showed a tissue-specific co-existence of SNAP-25 and syntaxin wit h synaptobrevin in the immunoisolated organelles. In conclusion, the m olecular components of the exocytotic machinery are shown to be conser ved in Torpedo, although some differences mainly on SNAP-25, suggest a potential diversity in the regulation of neurosecretion. (C) 1997 IBR O.