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.

Distinct kinetics of (H/K/N)Ras glucosylation and Rac1 glucosylation catalysed by Clostridium sordellii lethal toxin

“…The cellular state of Ras proteins must be taken into account if studies on TcsL are performed in cells expressing oncogenic (GTP-bound) Ras including many fibroblast lines. Small GTPases in general are preferably glucosylated in their GDP-bound state but (at least transiently) protected from glucosylation in their GTP-bound state [7,13]. One must expect that Ras transformed fibroblasts exhibit a lower sensitivity to TcsL-induced Ras glucosylation than to Rac1 glucosylation.…”

“…While TcsH specifically glucosylates Rho proteins, TcsL glucosylates Rac as well as the Ras family proteins (H/K/N/R)Ras, Rap(1/ 2), and Ral [9][10][11][12]. Treatment of cultured cells with TcsL results in actin re-organization (''cytopathic effect"), that is likely based on Rac1 glucosylation [13]. TcsL further causes apoptotic cell death (''cytotoxic effect"), likely based on the inhibition of (H/K/N)Ras/ phosphatidylinositide 3 0 -OH kinase (PI3 K)/Akt survival signaling [10,14,15].…”

Clostridium perfringens TpeL Glycosylates the Rac and Ras Subfamily Proteins

“…Furthermore, the isomeric TcdB from the variant C. difficile serotype F strain 1470 (TcdBF) that glucosylates Rac1 but not RhoA, has a cytopathic effect (13). Halabi-Cabezon et al (10) reported that the glucosylation of Rac1 rather than RhoA correlates with the cytopathic effect of TcdB. It has been reported that Rac1 plays a critical role in the organization of the actin cytoskeleton (3).…”

Clostridium difficile Toxin A Attenuates Wnt/β-Catenin Signaling in Intestinal Epithelial Cells

“…In part, this is due to actin reorganization and consequent inhibition of contractile ring formation in cytokinesis triggered by Rho glycosylation, leading to binucleation and cell cycle arrest at the G 2 -M level (11,(13)(14)(15)(16). TcdA and TcdB also block the G 1 -S transition (10,12).…”