Ability of inhibitors of glycosylation and protein synthesis to sensitize cells to abrin, ricin, Shigella toxin, and Pseudomonas toxin.

A number of compounds that interfere with glycoprotein synthesis and transport have been tested for their ability to sensitize cells to cancerostatic protein toxins. Tunicamycin, swainsonine, cycloheximide, and puromycin sensitized Vero cells and HeLa cells to abrin and ricin, as we have found previously with monensin (K. Sandvig and S. Olsnes, J. Biol. Chem., 257: 7504-7513, 1982). Cycloheximide, but not swainsonine, sensitized Vero cells to Pseudomonas exotoxin A and Shigella toxin. The ability of ricin to intoxicate cells was much lower at 19 degrees C than at 37 degrees C and there was almost no sensitizing effect of cycloheximide and monensin at 19 degrees C. Studies by electron microscopy showed that ricin conjugated to horseradish peroxidase appeared in trans Golgi elements in Vero cells. Possibly, transport of ricin into the cytosol requires passage through the Golgi apparatus. The possibility that the sensitizing agents here described may be valuable in enhancing the action of immunotoxins is discussed.