Actin involvement in exocytosis from PC12 cells: studies on the influence of botulinum C2 toxin on stimulated noradrenaline release.
Botulinum C2 toxin is known to ADP-ribosylate actin. The toxin effect was studied on [3H]noradrenaline secretion of PC12 cells. [3H]Noradrenaline release was stimulated five- to 15-fold by carbachol (100 microM) or K+ (50 mM) and 10-30-fold by the ionophore A23187 (5 microM). Pretreatment of PC12 cells with botulinum C2 toxin for 4-8 h at 20 degrees C, increased carbachol-, K+-, and A23187-induced, but not basal, [3H]noradrenaline release maximally 1.5-to three-fold, whereas approximately 75% of the cellular actin pool was ADP-ribosylated. Treatment of PC12 cells with botulinum C2 toxin for up to 1 h at 37 degrees C also increased stimulated [3H]noradrenaline secretion, whereas toxin treatment for greater than 1 h decreased the enhanced [3H]noradrenaline release stimulated by carbachol and K+ but not by A23187. Concomitantly with toxin-induced stimulation of secretion, 20-50% of the cellular actin was ADP-ribosylated, whereas greater than 60% of actin was modified when exocytosis was attenuated. The data indicate that ADP-ribosylation of actin by botulinum C2 toxin largely modulates stimulation of [3H]noradrenaline release. Moreover, the biphasic toxin effects suggest that distinct mechanisms are involved in the role of actin in secretion.
Matter
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Rudolf-Buchheim-Institut für Pharmakologie, Justus-Liebig-Universität, Giessen, F.R.G.
Dreyer
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F
Aktories
K
K
D000199:Actins / Q000502:physiology*; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000310:Adrenal Gland Neoplasms; D000818:Animals; D001905:Botulinum Toxins / Q000494:pharmacology*; D000001:Calcimycin / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D005089:Exocytosis; D009638:Norepinephrine / Q000378:metabolism*; D010673:Pheochromocytoma; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D014407:Tumor Cells, Cultured
D000199:Actins; D000246:Adenosine Diphosphate Ribose; D000001:Calcimycin; D002217:Carbachol; D001905:Botulinum Toxins; D011188:Potassium; D009638:Norepinephrine