A post-docking role for synaptobrevin in synaptic vesicle fusion.
We have used the squid giant synapse to determine the role of synaptobrevin, integral membrane proteins of small synaptic vesicles, in neurotransmitter release. The sequence of squid synaptobrevin, deduced by cDNA cloning, is 65%-68% identical to mammalian isoforms and includes the conserved cleavage site for tetanus and botulinum B toxins. Injection of either toxin into squid nerve terminals caused a slow, irreversible inhibition of release without affecting the Ca2+ signal which triggers release. Microinjection of a recombinant protein corresponding to the cytoplasmic domain of synaptobrevin produced a more rapid and reversible inhibition of release, whereas two smaller peptide fragments were without effect. Electron microscopy of tetanus-injected terminals revealed an increased number of both docked and undocked synaptic vesicles. These data indicate that synaptobrevin participates in neurotransmitter release at a step between vesicle docking and fusion.
Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710.
J M
JM
Hunt
K
K
Bommert
M P
MP
Charlton
A
A
Kistner
E
E
Habermann
G J
GJ
Augustine
H
H
Betz
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D001905:Botulinum Toxins / Q000378:metabolism / Q000633:toxicity; D002118:Calcium / Q000378:metabolism; D003001:Cloning, Molecular; D017124:Conserved Sequence; D018076:DNA, Complementary; D049832:Decapodiformes; D017952:Ganglia, Invertebrate / Q000502:physiology; D006801:Humans; D007150:Immunohistochemistry; D008561:Membrane Fusion; D008565:Membrane Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000502:physiology*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000502:physiology*; D010446:Peptide Fragments / Q000494:pharmacology; D050683:R-SNARE Proteins; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013572:Synaptic Vesicles / Q000187:drug effects / Q000502:physiology*; D013744:Tetanus Toxin / Q000378:metabolism / Q000633:toxicity
D018076:DNA, Complementary; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D050683:R-SNARE Proteins; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D013744:Tetanus Toxin; D001905:Botulinum Toxins; D002118:Calcium