Impairment of syntaxin by botulinum neurotoxin C1 or antibodies inhibits acetylcholine release but not Ca2+ channel activity.
The involvement of syntaxin, an omega-conotoxin-sensitive Ca2+ channel-associated protein, in acetylcholine release was studied at synapses formed between rat sympathetic neurons in culture. Transmission at these synapses involved omega-conotoxin-sensitive Ca2+ channels because a dose-dependent inhibition was observed when omega-conotoxin was bath-applied. Confocal microscope examination of immunofluorescent staining showed that syntaxin had a similar distribution to synaptic vesicle-associated membrane proteins, synaptophysin and vesicle-associated membrane protein/synaptobrevin-2, indicating that syntaxin molecules are concentrated in the presynaptic terminals. Botulinum neurotoxin C1 applied extracellularly or intracellularly into presynaptic neurons blocked synaptic transmission. Introduction of a monoclonal antibody, or polyclonal antibodies, to syntaxin into the presynaptic neuron depressed the evoked release of acetylcholine without affecting Ca2+ influx through Ca2+ channels. These results suggest that syntaxin plays an important role in release of neurotransmitter by a nerve impulse and that this mechanism is downstream of Ca2+ influx.
Mochida
S
S
Department of Physiology, Tokyo Medical College, Japan.
Saisu
H
H
Kobayashi
H
H
Abe
T
T
D000109:Acetylcholine / Q000378:metabolism*; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000906:Antibodies / Q000276:immunology*; D015220:Calcium Channels / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007231:Infant, Newborn; D008565:Membrane Proteins / Q000378:metabolism*; D050765:Qa-SNARE Proteins; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D000906:Antibodies; D015220:Calcium Channels; D008565:Membrane Proteins; D050765:Qa-SNARE Proteins; D000109:Acetylcholine