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Signal transduction pathways and cellular intoxication with Clostridium difficile toxins
M C Shoshan1, C Fiorentini, M Thelestam
1Department of Bacteriology, Karolinska Institute, Stockholm, Sweden.
Journal of Cellular Biochemistry
|May 1, 1993
Summary
Clostridium difficile toxins A and B cause cell damage by reorganizing the cytoskeleton. This process requires phospholipase A2 (PLA2) activity and involves protein kinase C signaling, but not G-proteins or cyclic nucleotides.
Area of Science:
- Microbiology
- Cell Biology
- Toxicology
Background:
- Clostridium difficile toxins A and B induce similar cytopathic effects (CPE) in cultured cells, involving cytoskeletal reorganization.
- The precise molecular mechanisms underlying these toxin-induced CPEs remain largely unknown.
Purpose of the Study:
- To elucidate the molecular pathways involved in Clostridium difficile toxin A and B-induced cytopathic effects.
- To investigate the role of signal transduction pathways in mediating toxin-induced cytoskeletal damage.
Main Methods:
- Cultured cells were preincubated with modulators of signal transduction pathways before exposure to Clostridium difficile toxins A or B.
- Development of cytopathic effects (CPE) was monitored to assess the impact of pathway modulation.
- Specific inhibitors and activators targeting protein kinase C, phospholipase A2, G-proteins, and cyclic nucleotides were employed.
Main Results:
- Phorbol esters and mezerein, activators of protein kinase C, enhanced both toxin A and B-induced CPEs.
- Inhibitors of phospholipase A2 (PLA2), quinacrine and 4-bromophenacylbromide, significantly inhibited the development of CPE for both toxins.
- Modulation of G-proteins, cyclic nucleotides (cGMP, cAMP), phosphatases, prostacyclin, lipoxygenase, and phospholipase C did not affect toxin-induced CPE.
- Both Clostridium difficile toxins A and B were demonstrated to activate phospholipase A2.
Conclusions:
- The cytoskeletal reorganization induced by Clostridium difficile toxins A and B necessitates phospholipase A2 (PLA2) activity.
- A protein kinase C-dependent pathway is implicated in the mechanism of action of these toxins.
- Pertussis toxin-sensitive G-proteins, cyclic nucleotides, eicosanoid metabolites, and phospholipase C are not directly involved in the observed cytoskeletal effects.