title: Expression and cytoprotective activity of the small GTPase RhoB induced by the Escherichia coli cytotoxic necrotizing factor 1.
abstract: RhoB is the only member of the Rho subfamily of small GTPases, which is classified as an immediate early gene product. RhoB is up-regulated in response to growth factors as well as cytotoxic and genotoxic agents. Clostridial glucosylating toxins have been reported to evoke pronounced RhoB expression, based on the inactivation of Rho/Ras proteins. In this study, we report on a long lasting expression of RhoB in cultured cells upon activation of Rho proteins by the cytotoxic necrotizing factor 1 (CNF1) from Escherichia coli. The observations of this study highlight a new pathway involving Rac1, which positively regulates the activity of the rhoB promoter and RhoB expression. Conversely, the isomeric cytotoxic necrotizing factor from Yersinia pseudotuberculosis (CNFy) drives GTP-loading of basal RhoB but fails to cause activation of the rhoB promoter and thus its expression. CNF1 inhibits cytokinesis and induces the formation of bi-nucleated (tetraploid) cells. Upon long term treatment with CNF1, RhoB(-/-) mouse embryonic fibroblasts (MEFs) exhibit DNA fragmentation, phosphatidylserine exposure, and loss of membrane integrity, while RhoB(+/-) MEFs persist as bi-nucleated (tetraploid) cells without any signs of cell death. In conclusion, the cytoprotective RhoB response is not only evoked by bacterial protein toxins inactivating Rho/Ras proteins but also by the Rac1-activating toxin CNF1.
authors.affiliation: Institute of Toxicology, Hannover Medical School, D-30625 Hannover, Germany.
authors.forename: Stefanie C
authors.initials: SC
authors.lastname: Huelsenbeck
authors.forename: Dennis
authors.initials: D
authors.lastname: Roggenkamp
authors.forename: Martin
authors.initials: M
authors.lastname: May
authors.forename: Johannes
authors.initials: J
authors.lastname: Huelsenbeck
authors.forename: Cord
authors.initials: C
authors.lastname: Brakebusch
authors.forename: Klemens
authors.initials: K
authors.lastname: Rottner
authors.forename: Markus
authors.initials: M
authors.lastname: Ladwein
authors.forename: Ingo
authors.initials: I
authors.lastname: Just
authors.forename: Gerhard
authors.initials: G
authors.lastname: Fritz
authors.forename: Gudula
authors.initials: G
authors.lastname: Schmidt
authors.forename: Harald
authors.initials: H
authors.lastname: Genth
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000494:pharmacology*; D016923:Cell Death / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D019610:Cytoprotection / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D019073:HT29 Cells; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D011123:Polyploidy; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects; D015011:Yersinia pseudotuberculosis / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D020743:rhoB GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D001427:Bacterial Toxins; D029968:Escherichia coli Proteins; D012333:RNA, Messenger; C060296:cytotoxic necrotizing factor type 1; D020830:rac1 GTP-Binding Protein; D020743:rhoB GTP-Binding Protein
keywords: Apoptosis; CNF1; Clostridium difficile Toxin B; Cytokinesis; Deamidation; Glucosylation; Lethal Toxin from C. sordellii; Multi-nucleation; Ras; Rho; TcdA; TcdB; TcsL; Toxin A from C. difficile strain; Toxin B from C. difficile strain; cytotoxic necrotizing factor from E. coli; cytotoxic necrotizing factor from Y. pseudotuberculosis