title: Inactivation of small Rho GTPases by the multifunctional RTX toxin from Vibrio cholerae.
abstract: Many bacterial toxins target small Rho GTPases in order to manipulate the actin cytoskeleton. The depolymerization of the actin cytoskeleton by the Vibrio cholerae RTX toxin was previously identified to be due to the unique mechanism of covalent actin cross-linking. However, identification and subsequent deletion of the actin cross-linking domain within the RTX toxin revealed that this toxin has an additional cell rounding activity. In this study, we identified that the multifunctional RTX toxin also disrupts the actin cytoskeleton by causing the inactivation of small Rho GTPases, Rho, Rac and Cdc42. Inactivation of Rho by RTX was reversible in the presence of cycloheximide and by treatment of cells with CNF1 to constitutively activate Rho. These data suggest that RTX targets Rho GTPase regulation rather than affecting Rho GTPase directly. A novel 548-amino-acid region of RTX was identified to be responsible for the toxin-induced inactivation of the Rho GTPases. This domain did not carry GAP or phosphatase activities. Overall, these data show that the RTX toxin reversibly inactivates Rho GTPases by a mechanism distinct from other Rho-modifying bacterial toxins.
authors.affiliation: Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
authors.forename: Kerri-Lynn
authors.initials: KL
authors.lastname: Sheahan
authors.forename: Karla J Fullner
authors.initials: KJ
authors.lastname: Satchell
mesh_terms: D000199:Actins / Q000378:metabolism; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D003513:Cycloheximide / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D029968:Escherichia coli Proteins / Q000494:pharmacology; D020690:GTPase-Activating Proteins / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008856:Microscopy, Fluorescence; D008858:Microscopy, Phase-Contrast; D020559:Monomeric GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000235:genetics / Q000502:physiology; D014734:Vibrio cholerae / Q000378:metabolism*; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D000199:Actins; D001427:Bacterial Toxins; D029968:Escherichia coli Proteins; D020690:GTPase-Activating Proteins; C060296:cytotoxic necrotizing factor type 1; D049452:Green Fluorescent Proteins; D003513:Cycloheximide; D010744:Phosphoric Monoester Hydrolases; D020559:Monomeric GTP-Binding Proteins; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins