title: The long-lived nature of clostridium perfringens iota toxin in mammalian cells induces delayed apoptosis.
abstract: Mono-ADP ribosylation of actin by bacterial toxins, such as Clostridium perfringens iota or Clostridium botulinum C2 toxins, results in rapid depolymerization of actin filaments and cell rounding. Here we report that treatment of African green monkey kidney (Vero) cells with iota toxin resulted in delayed caspase-dependent death. Unmodified actin did not reappear in toxin-treated cells, and enzyme-active toxin was detectable in the cytosol for at least 24 h. C2 toxin showed comparable, long-lived effects in cells, while a C2 toxin control lacking ADP-ribosyltransferase activity did not induce cell death. To address whether the remarkable stability of the iota and C2 toxins in cytosol was crucial for inducing cell death, we treated cells with C/SpvB, the catalytic domain of Salmonella enterica SpvB. Although C/SpvB also mono-ADP ribosylates actin as do the iota and C2 toxins, cells treated with a cell-permeating C/SpvB fusion toxin became rounded but recovered and remained viable. Moreover, unmodified actin reappeared in these cells, and ADP-ribosyltransferase activity due to C/SpvB was not detectable in the cytosol after 24 h, a result most likely due to degradation of C/SpvB. Repeated application of C/SpvB prevented recovery of cells and reappearance of unmodified actin. In conclusion, a complete but transient ADP ribosylation of actin was not sufficient to trigger apoptosis, implying that long-term stability of actin-ADP-ribosylating toxins, such as iota and C2, in the cytosol is crucial for inducing delayed, caspase-dependent cell death.
authors.affiliation: Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, D-89081 Ulm, Germany.
authors.forename: Hanna
authors.initials: H
authors.lastname: Hilger
authors.forename: Sascha
authors.initials: S
authors.lastname: Pust
authors.forename: Guido
authors.initials: G
authors.lastname: von Figura
authors.forename: Eva
authors.initials: E
authors.lastname: Kaiser
authors.forename: Bradley G
authors.initials: BG
authors.lastname: Stiles
authors.forename: Michel R
authors.initials: MR
authors.lastname: Popoff
authors.forename: Holger
authors.initials: H
authors.lastname: Barth
mesh_terms: D036002:ADP Ribose Transferases / Q000235:genetics / Q000378:metabolism / Q000633:toxicity*; D000199:Actins / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D001427:Bacterial Toxins / Q000378:metabolism / Q000633:toxicity*; D001905:Botulinum Toxins / Q000378:metabolism / Q000633:toxicity; D048430:Cell Shape / Q000187:drug effects; D002522:Chlorocebus aethiops; D010539:Permeability / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism / Q000633:toxicity; D013997:Time Factors; D014709:Vero Cells; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism / Q000633:toxicity
chemical_list: D000199:Actins; D001427:Bacterial Toxins; D011993:Recombinant Fusion Proteins; D037521:Virulence Factors; C050737:iota toxin, Clostridium perfringens; D036002:ADP Ribose Transferases; C415223:spvB protein, Salmonella enterica virulence plasmid; D001905:Botulinum Toxins; C096324:botulinum toxin type C