Glucosylation of Rho proteins by Clostridium difficile toxin B

Abstract

Toxin A and B, the major virulence factors of Clostridium difficile, are the causative agents of antibiotic-associated pseudomembranous colitis. In cultured cell lines their potent cytotoxicity results from their ability to induce disaggregation of the microfilament cytoskeleton. Toxin B acts on the low-molecular-mass GTPase RhoA, which is involved in the regulation of the actin cytoskeleton. We report here that toxin B catalyses the incorporation of up to one mole of glucose per mole of RhoA at the amino acid threonine at position 37. The modification was identified and localized by tandem electrospray mass spectrometry. UDP-glucose selectively serves as cosubstrate for the monoglucosylation reaction catalysed by toxin B. Microinjection of RhoA previously glucosylated by toxin B into monolayer cells caused disaggregation of actin filaments, indicating a dominant-negative activity of glucosylated RhoA.

Involvement of the SKP2–p27KIP1 pathway in suppression of cancer cell proliferation by RECK

“…In fact, collagenolytic activity of SW620 cells was greatly diminished after Ad-RECK infection, as visualized by in situ zymography using DQ type I collagen (Figure 4c). We also found that the effect of type I collagen to downregulate SKP2 could be suppressed by the protein kinase C inhibitor GF109203X (Toullec et al, 1991) (Figure 4e) and the Rho-family GTPase inhibitor toxin B (Just et al, 1995) (Figure 4f), but not by the Src inhibitor PP2 (Hanke et al, 1996) (Figure 4d). Protein kinase C and Rhofamily GTPases are known to be involved in integrin signaling (Caswell et al, 2009).…”

Intracellular trafficking of nonviral vectors

“…and Rho GTPase inhibitors, such as toxin B, 89 can inhibit macropinocytosis, they affect other endocytic pathways as well. Macropinosomes can acidify but do not intersect with lysosomes, 90 thus representing a potential alternative cell entry route of gene transfer for the avoidance of lysosomal degradation.…”

C3 exoenzymes, novel insights into structure and action of Rho-ADP-ribosylating toxins

“…Binding of ADP-ribosylated RhoA to GDI is increased, which leads to a cytosolic accumulation of inactive RhoRhoGDI complex ("trapping effect") Studies from recent years identified Rho GTPases as the preferred targets of several bacterial toxins. In addition to the ADP-ribosylation by C3, Rho GTPases are covalently modified by glucosylation (e.g., by clostridial glucosylating toxins; Aktories and Barbieri 2005;Just et al 1995b;Aktories and Just 2005;Voth and Ballard 2005;Just and Gerhard 2004), deamidation (e.g., by E. coli cytotoxic necrotizing factor; Schmidt et al 1997;Flatau et al 1997), and transglutamination (Bordetella dermonecrotizing factor; Masuda et al 2000) resulting in inactivation or activation of the GTPases respectively (Fig. 2).…”