title: A cell-permeable fusion toxin as a tool to study the consequences of actin-ADP-ribosylation caused by the salmonella enterica virulence factor SpvB in intact cells.
abstract: The virulence factor SpvB is a crucial component for the intracellular growth and infection process of Salmonella enterica. The SpvB protein mediates the ADP-ribosylation of actin in infected cells and is assumed to be delivered directly from the engulfed bacteria into the host cell cytosol. Here we used the binary Clostridium botulinum C2 toxin as a transport system for the catalytic domain of SpvB (C/SpvB) into the host cell cytosol. A recombinant fusion toxin composed of the enzymatically inactive N-terminal domain of C. botulinum C2 toxin (C2IN) and C/SpvB was cloned, expressed, and characterized in vitro and in intact cells. When added together with C2II, the C2IN-C/SpvB fusion toxin was efficiently delivered into the host cell cytosol and ADP-ribosylated actin in various cell lines. The cellular uptake of the fusion toxin requires translocation from acidic endosomes into the cytosol and is facilitated by Hsp90. The N- and C-terminal domains of SpvB are linked by 7 proline residues. To elucidate the function of this proline region, fusion toxins containing none, 5, 7, and 9 proline residues were constructed and analyzed. The existence of the proline residues was essential for the translocation of the fusion toxins into host cell cytosol and thereby determined their cytopathic efficiency. No differences concerning the mode of action of the C2IN-C/SpvB fusion toxin and the C2 toxin were obvious as both toxins induced depolymerization of actin filaments, resulting in cell rounding. The acute cellular responses following ADP-ribosylation of actin did not immediately induce cell death of J774.A1 macrophage-like cells.
authors.affiliation: Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, D-89081 Ulm, Germany.
authors.forename: Sascha
authors.initials: S
authors.lastname: Pust
authors.forename: Henrike
authors.initials: H
authors.lastname: Hochmann
authors.forename: Eva
authors.initials: E
authors.lastname: Kaiser
authors.forename: Guido
authors.initials: G
authors.lastname: von Figura
authors.forename: Karin
authors.initials: K
authors.lastname: Heine
authors.forename: Klaus
authors.initials: K
authors.lastname: Aktories
authors.forename: Holger
authors.initials: H
authors.lastname: Barth
mesh_terms: D036002:ADP Ribose Transferases / Q000235:genetics / Q000494:pharmacology*; D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D000818:Animals; D001905:Botulinum Toxins / Q000235:genetics / Q000494:pharmacology*; D002463:Cell Membrane Permeability / Q000187:drug effects; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000494:pharmacology; D019779:Salmonella enterica / Q000235:genetics / Q000472:pathogenicity; D014709:Vero Cells; D037521:Virulence Factors / Q000235:genetics / Q000494:pharmacology*
chemical_list: D000199:Actins; D018841:HSP90 Heat-Shock Proteins; D011993:Recombinant Fusion Proteins; D037521:Virulence Factors; D036002:ADP Ribose Transferases; C415223:spvB protein, Salmonella enterica virulence plasmid; D001905:Botulinum Toxins; C096324:botulinum toxin type C