This Article Full Text Full Text (PDF) Other Versions of this Article: IAI.01705-06v1 75/2/801    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Huelsenbeck, J. Articles by Genth, H. Search for Related Content PubMed PubMed Citation Articles by Huelsenbeck, J. Articles by Genth, H.

Difference in the Cytotoxic Effects of Toxin B from Clostridium difficile Strain VPI 10463 and Toxin B from Variant Clostridium difficile Strain 1470

Institute of Toxicology, Hannover Medical School, D-30625 Hannover, Germany,¹ Institute of Pharmacology and Toxicology, University of Ulm Medical Center, D-89081 Ulm, Germany²

Received 25 October 2006/ Returned for modification 3 November 2006/ Accepted 20 November 2006

Glucosylation of RhoA, Rac1, and Cdc42 by Clostridium difficile toxin B from strain VPI 10463 (TcdB) results in actin reorganization (cytopathic effect) and apoptosis (cytotoxic effect). Toxin B from variant C. difficile strain 1470 serotype F (TcdBF) differs from TcdB with regard to substrate proteins, as it glucosylates Rac1 and R-Ras but not RhoA and Cdc42. In this study, we addressed the question of whether the cellular effects of the toxins depend on their protein substrate specificity. Rat basophilic leukemia (RBL) cells were synchronized using the thymidine double-block technique. We show that cells were most sensitive to the cytotoxic effect of TcdB in S phase, as analyzed in terms of phosphatidyl serine externalization, fragmentation of nuclei, and activation of caspase-3; in contrast, TcdBF induced only a marginal cytotoxic effect, suggesting that inactivation of RhoA (but not of Rac1) was required for the cytotoxic effect. The glucosylation of Rac1 was correlated to the cytopathic effect of either toxin, suggesting a close connection of the two effects. The cytotoxic effect of TcdB was executed by caspase-3, as it was responsive to inhibition by acetyl-Asp-Met-Gln-Asp-aldehyde (Ac-DMQD-CHO), an inhibitor of caspase-3. The viability of TcdB-treated RBL cells was reduced, whereas the viability of TcdBF-treated cells was unchanged, further confirming that inactivation of RhoA is required for the cytotoxic effect. In conclusion, the protein substrate specificity of the glucosylating toxins determines their biological activity.

Published ahead of print on 4 December 2006.

Editor: D. L. Burns

This article has been cited by other articles:

• Busche, S., Descot, A., Julien, S., Genth, H., Posern, G. (2008). Epithelial cell-cell contacts regulate SRF-mediated transcription via Rac-actin-MAL signalling. J. Cell Sci. 121: 1025-1035 [Abstract] [Full Text]