Gangliosides mediate inhibitory effects of tetanus and botulinum A neurotoxins on exocytosis in chromaffin cells.
Bovine chromaffin cells in monolayer culture were preloaded with 3H-NA (noradrenaline) and subsequently stimulated with carbachol. Botulinum A neurotoxin partially inhibited the evoked release of 3H-NA and the basal efflux of the hormone. The inhibition of evoked release did not exceed 40%, although the cells were exposed to 10 micrograms/ml of toxin for 6 days. The inhibitory effect of botulinum A neurotoxin was neutralized by its antibodies. In contrast to botulinum A neurotoxin, tetanus toxin at even higher concentrations did not influence evoked release. This difference in sensitivity could be explained by the ganglioside pattern of chromaffin cells. Ganglioside GD1a, a putative receptor for botulinum A neurotoxin, could be identified in lipophilic extracts, whereas the tetanus toxin binding gangliosides GT1b and GD1b could not be detected by means of thin-layer chromatography. Treatment of the cells with neuraminidase abolished both, GD1a and the inhibitory effect of botulinum A neurotoxin. Incubation of chromaffin cells with a mixture of gangliosides (21% GM1, 44% GD1a, 15% GD1b, 20% GT1b) not only increased the efficacy of botulinum A neurotoxin but also made the cells sensitive towards tetanus toxin. The concentration-response curve of botulinum A neurotoxin was shifted to the left about five-fold and the maximum inhibition of evoked release was increased up to 60%, even though the cells were exposed to the toxin for 3 days only. In contrast, the maximum inhibition that could be achieved by tetanus toxin was 40%. The results indicate that polysialogangliosides are important for the intracellular accumulation of these clostridial neurotoxins.
Med. Hochschule Hannover, Dept of Pharmacology and Toxicology, F.R.G.
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P
Marxen
U
U
Fuhrmann
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H
Bigalke
D000313:Adrenal Medulla / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D001905:Botulinum Toxins / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology; D002217:Carbachol / Q000494:pharmacology; D002417:Cattle; D002478:Cells, Cultured; D005089:Exocytosis / Q000187:drug effects*; D005732:Gangliosides / Q000378:metabolism / Q000502:physiology*; D009498:Neurotoxins / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism*; D013744:Tetanus Toxin / Q000494:pharmacology*
D005732:Gangliosides; D009498:Neurotoxins; D013744:Tetanus Toxin; D002217:Carbachol; D001905:Botulinum Toxins; D002118:Calcium; D009638:Norepinephrine