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Microtubule‐Dissociating Drugs and A23187 Reveal Differences in the Inhibition of Synaptosomal Transmitter Release by Botulinum Neurotoxins Types A and B
Author(s) -
Ashton Anthony C.,
Dolly J. Oliver
Publication year - 1991
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1991.tb01998.x
Subject(s) - neurotoxin , colchicine , microtubule , nocodazole , chemistry , cytochalasin b , clostridium botulinum , biochemistry , toxin , biology , cytoskeleton , biophysics , pharmacology , microbiology and biotechnology , in vitro , cell , genetics
The inhibitory effects of botulinum neurotoxins types A and B on Ca 2+ ‐dependent evoked release of [ 3 H]noradrenaline from rat cerebrocortical synaptosomes were compared and their molecular basis investigated. A23187, a Ca 2+ ionophore, proved more efficacious in reversing the blockade produced by type A than that by B, whereas the actions of neither were changed by increasing intraterminal cyclic GMP levels using 8‐bromo‐cyclic GMP or nitroprusside. Disruption of the actin‐based cytoskeleton with cytochalasin D did not alter the inhibition seen subsequently with either toxin. However, prior disassembly of microtubules with colchicine, nocodazole, or griseofulvin reduced the potency of type B toxin, but not that of type A toxin; stabilization of the microtubules with taxol counteracted this effect of colchicine. Because colchicine treatment of synaptosomes did not interfere with the measurable binding of type B toxin or its apparent uptake, it appears to act intracellularly. Collectively, these data suggest that botulinum neurotoxins types A and B inactivate transmitter release by interaction at different sites in the process. Based on the consistent results observed with four different drugs known to affect selectively microtubules, their involvement in the action of the type B neurotoxin is proposed.