title: R-Ras glucosylation and transient RhoA activation determine the cytopathic effect produced by toxin B variants from toxin A-negative strains of Clostridium difficile.
abstract: Clostridium difficile induces antibiotic-associated diarrhea through the production of toxin A and toxin B; the former toxin has been assumed to be responsible for the symptoms of the disease. Several toxin A-negative strains from C. difficile have recently been isolated from clinical cases and have been reported to produce toxin B variants eliciting an atypical cytopathic effect. Ultrastructural analysis indicated these toxins induce a rounding cytopathic effect and filopodia-like structures. Toxin B variants glucosylated R-Ras, and transfection with a constitutively active mutant of this GTPase protected cells against their cytopathic effect. Treatment of cells with toxin B variants induced detachment from the extracellular matrix and blockade of the epidermal growth factor-mediated phosphorylation of extracellular-regulated protein kinases, demonstrating a deleterious effect on the R-Ras-controlled avidity of integrins. Treatment with toxin B variants also induced a transient activation of RhoA probably because of inactivation of Rac1. Altogether, these data indicate that the cytopathic effect induced by toxin B variants is because of cell rounding and detachment mediated by R-Ras glucosylation, and the induction of filopodia-like structures is mediated by RhoA activation. Implications for the pathophysiology of C. difficile-induced diarrhea are discussed.
authors.affiliation: Microbiology and Tumorbiology Center, Box 280, Karolinska Institutet, S-17177 Stockholm, Sweden. echaves@cariari.ucr.ac.cr
authors.forename: Esteban
authors.initials: E
authors.lastname: Chaves-Olarte
authors.forename: Enrique
authors.initials: E
authors.lastname: Freer
authors.forename: Andrea
authors.initials: A
authors.lastname: Parra
authors.forename: Caterina
authors.initials: C
authors.lastname: Guzmán-Verri
authors.forename: Edgardo
authors.initials: E
authors.lastname: Moreno
authors.forename: Monica
authors.initials: M
authors.lastname: Thelestam
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001426:Bacterial Proteins; D001427:Bacterial Toxins / Q000378:metabolism*; D016360:Clostridioides difficile / Q000378:metabolism* / Q000472:pathogenicity; D004789:Enzyme Activation; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D006031:Glycosylation; D051379:Mice; D008855:Microscopy, Electron, Scanning; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D014443:Tyrosine / Q000378:metabolism; D014774:Virulence; D018631:ras Proteins / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; C031815:toxB protein, Clostridium difficile; D014443:Tyrosine; D020928:Mitogen-Activated Protein Kinases; D020558:GTP Phosphohydrolases; C513254:Rras protein, mouse; D018631:ras Proteins; D020742:rhoA GTP-Binding Protein