CLOSTRIDIUM-SORDELLII CYTOTOXIN INDUCES PHOSPHORYLATION OF AN 80,000-MOL-WT PROTEIN IN MCCOY CULTURED-CELLS

The cytotoxins from Clostridium difficile (toxin B) and Clostridium so rdellii (toxin L) induce rounding of cultured cells. The cellular effe cts induced by these two cytotoxins are clearly distinct, suggesting t hat both toxins use a similar, but not identical mechanism for cell in toxication. We have employed the technique of two-dimensional PAGE for the separation of P-32-Iabelled cell lysates of McCoy cultured cells to investigate changes in the phosphorylation status of cellular prote ins after treatment with toxin B and with toxin L. The two-dimensional electrophoresis patterns suggest the implication of an 80,000 mol. wt cellular protein (named pp80c) in the cytopathic action of the cytoto xin from C. sordellii. This protein shows immunoreactivity with non-mu scle caldesmon. Toxin B, however, does not affect the phosphorylation of pp80c, but alters the phosphorylation of another cellular protein, pp77, indicating another mechanism for cell intoxication. In addition, our experiments suggest that the mechanism of action of okadaic acid, a phosphatase inhibitor which causes cell rounding similar to that in duced by C. sordellii, and these two cytotoxins are different.