Mechanism of Action of Tetanus Toxin

We examined an in vivo system to explore whether protein kinase C PKC activity is diminished when animals become intoxicated with tetanus toxin TT. Homogenates of brain and spinal cord from mice manifesting generalized tetanus after receiving a 50x minimal lethal dose of TT were assayed for PKC activity. PKC activity p-mole per mg protein per min was similar in cytosol and membrane fractions of brain from control C and TT-intoxicated mice. Cytosolic PKC activity in the spinal cord was depressed in TT-intoxicated mice, 87.3 or - 25, cord was similar in C- and TT-intoxicated mice. Cytosolic PKC activity was similar in C- and TT treated macrophages as well as in C- and TT- intoxicated mice from both the brain and the spinal cord. These data could be linked to our previous finding of TT-induced inhibition of lysosomal secretion in human macrophages. However, in subsequent experiments, we were unable to demonstrate any direct interaction of TT with purified PKC. Because of our recent substantial progress in purification and characterization of the human neutorphil lysosomal Calcium pump, we turned our investigation towards the observation that TT directly stimulates this pump. Tetanus toxin significantly increased ATP-dependent Calcium uptake by human neutrophil lysosomes in a saturable and dose-dependent manner.