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 sordellii (toxin L) induce rounding of cultured cells. The cellular effects induced by these two cytotoxins are clearly distinct, suggesting that both toxins use a similar, but not identical mechanism for cell intoxication. We have employed the technique of two-dimensional PAGE for the separation of 32P-labelled cell lysates of McCoy cultured cells to investigate changes in the phosphorylation status of cellular proteins 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 cytotoxin from C. sordellii. This protein shows immunoreactivity with non-muscle 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 induced by C. sordellii, and these two cytotoxins are different.