title: In vivo covalent cross-linking of cellular actin by the Vibrio cholerae RTX toxin.
abstract: Enteric pathogens often export toxins that elicit diarrhea as a part of the etiology of disease, including toxins that affect cytoskeletal structure. Recently, we discovered that the intestinal pathogen Vibrio cholerae elicits rounding of epithelial cells that is dependent upon a gene we designated rtxA. Here we investigate the association of rtxA with the cell-rounding effect. We find that V. cholerae exports a large toxin, RTX (repeats-in-toxin) toxin, to culture supernatant fluids and that this toxin is responsible for cell rounding. Furthermore, we find that cell rounding is not due to necrosis, suggesting that RTX toxin is not a typical member of the RTX family of pore-forming toxins. Rather, RTX toxin causes depolymerization of actin stress fibers and covalent cross-linking of cellular actin into dimers, trimers and higher multimers. This RTX toxin-specific cross-linking occurs in cells previously rounded with cytochalasin D, indicating that G-actin is the toxin target. Although several models explain our observations, our simultaneous detection of actin cross-linking and depolymerization points toward a novel mechanism of action for RTX toxin, distinguishing it from all other known toxins.
authors.affiliation: Department of Microbiology and Molecular Genetics, Harvard Medical School, 200 Longwood Avenue, D1-408, Boston, MA 02115, USA.
authors.forename: K J
authors.initials: KJ
authors.lastname: Fullner
authors.forename: J J
authors.initials: JJ
authors.lastname: Mekalanos
mesh_terms: D036002:ADP Ribose Transferases / Q000378:metabolism; D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000595:Amino Acid Sequence; D000906:Antibodies / Q000494:pharmacology; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D015153:Blotting, Western; D001905:Botulinum Toxins; D002463:Cell Membrane Permeability / Q000187:drug effects; D048429:Cell Size / Q000187:drug effects; D002772:Cholera Toxin / Q000737:chemistry / Q000378:metabolism*; D003432:Cross-Linking Reagents / Q000737:chemistry / Q000378:metabolism*; D017077:Culture Media, Conditioned / Q000737:chemistry / Q000378:metabolism; D015638:Cytochalasin D / Q000494:pharmacology; D003603:Cytotoxins / Q000737:chemistry / Q000378:metabolism*; D019281:Dimerization; D006801:Humans; D008954:Models, Biological; D008969:Molecular Sequence Data; D011485:Protein Binding; D016415:Sequence Alignment; D022502:Stress Fibers / Q000187:drug effects; D014407:Tumor Cells, Cultured; D014734:Vibrio cholerae / Q000737:chemistry / Q000378:metabolism* / Q000472:pathogenicity; D020741:rho GTP-Binding Proteins / Q000378:metabolism
chemical_list: D000199:Actins; D000906:Antibodies; D001426:Bacterial Proteins; D003432:Cross-Linking Reagents; D017077:Culture Media, Conditioned; D003603:Cytotoxins; D000246:Adenosine Diphosphate Ribose; D015638:Cytochalasin D; D002772:Cholera Toxin; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D001905:Botulinum Toxins; D020741:rho GTP-Binding Proteins