Tetanus toxin attenuates the ability of phorbol myristate acetate to mobilize cytosolic protein kinase C in NG-108 cells

Although the pathology of tetanus toxin poisoning has been linked to an inhibition of neurotransmitter release, the mechanism of this inhibition is unknown. The neuroblastoma x glioma hybrid cell NG-108 is an emerging model in which to study the biochemical effect of tetanus toxin on acetylcholine secretion. In differentiated as well as undifferentiated NG-108 cells, a 4 hr tetanus toxin (10(-8) M) pretreatment had no effect on basal levels of cyclic AMP or cyclic GMP. In addition, toxin pretreatment did not affect agonist induced increases in either cyclic nucleotide. Treatment of NG-108 cells for 4 hr with 10(-10) M tetanus toxin had no effect on the subsequently measured activity of cytosolic protein kinase C. However, a 4 hr pretreatment of undifferentiated or differentiated cells with tetanus toxin (10(-8) or 10(-10) M respectively) significantly attenuated the ability of phorbol myristate acetate to mobilize cytosolic protein kinase C. Direct addition of tetanus toxin (10(-7)-10(-10) M) to isolated protein kinase C did not alter the ability of the enzyme to phosphorylate histone protein. These results suggest that one manifestation of tetanus toxin poisoning may be a disruption in protein kinase C metabolism.

Actions of the Clostridium botulinum binary toxin on the structure and function of Y-1 adrenal cells

The binary toxin produced by Clostridium botulinum, also known as type C2 toxin, was examined for its ability to alter the structure and function of Y-1 cells, a murine adrenocortical tumor line. The toxin produced time- and concentration-dependent changes in morphology, characterized by retraction of cell extensions and by rounding of the cell body. These changes were not accompanied by increases or decreases in tissue levels of c-AMP or c-GMP, although there was an increase in the release of total steroids. When cells were exposed to toxin for 24 hr there was no evidence of cell death or lysis. Total nucleic acid content and the rate of incorporation of 14C-leucine into protein were comparable in control cells and intoxicated cells. The toxin has been shown to possess mono(ADP-ribosyl)ating activity, and actin is the presumed substrate. When Y-1 cells were ruptured and then exposed to the toxin in the presence of 32P-NAD, actin was ADP-ribosylated. When cells were exposed to the toxin before being ruptured, there was a subsequent loss in the amount of actin that was available for ADP-ribosylation (32P-NAD) in the broken cell assay. The data suggest that Y-1 cells can survive challenge with the botulinum binary toxin, and thus they are a suitable tissue in which to use the toxin as a pharmacological tool.