Prevention of the cytopathic effect induced by Clostridium difficile Toxin B by active Rac1

Abstract 

Clostridium difficile Toxin B (TcdB) glucosylates low molecular weight GTP-binding proteins of the Rho subfamily and thereby causes actin re-organization (cell rounding). This “cytopathic effect” has been generally attributed to RhoA inactivation. Here we show that cells expressing non-glucosylatable Rac1-Q61L are protected from the cytopathic effect of TcdB. In contrast, cells expressing RhoA-Q63L or mock-transfected cells are fully susceptible for the cytopathic effect of TcdB. These findings are extended to the Rac1/RhoG mimic IpgB1 and the RhoA mimic IpgB2 from Shigella. Ectopic expression of IpgB1, but not IpgB2, counteracts the cytopathic effect of TcdB. These data strongly suggest that Rac1 rather than RhoA glucosylation is critical for the cytopathic effect of TcdB.

Abbreviations: C3-bot, exoenzyme C3 from Clostridium botulinum, C3-lim, exoenzyme C3 from Clostridium limosum, Mab, monoclonal antibody, TcdA, Toxin A from Clostridium difficile strain VPI10643, TcdB, Toxin B from Clostridium difficile strain VPI10643, TcdBF, Toxin B from the variant Clostridium difficile serotype F strain 1470, TcsH, hemorrhagic toxin from Clostridium sordellii, TcsL, lethal toxin from Clostridium sordellii

Keywords: Clostridium difficile Toxin B, Clostridium botulinum exoenzyme C3, Shigella, IpgB1, Glucosylation, RhoA, Fibroblast