title: Salmonella enterica delivers its genotoxin through outer membrane vesicles secreted from infected cells.
abstract: Cytolethal-distending toxins (CDTs) belong to a family of DNA damage inducing exotoxins that are produced by several Gram-negative bacteria. Salmonella enterica serovar Typhi expresses its CDT (named as Typhoid toxin) only in the Salmonella-containing vacuole (SCV) of infected cells, which requires its export for cell intoxication. The mechanisms of secretion, release in the extracellular space and uptake by bystander cells are poorly understood. We have addressed these issues using a recombinant S. Typhimurium strain, MC71-CDT, where the genes encoding for the PltA, PltB and CdtB subunits of the Typhoid toxin are expressed under control of the endogenous promoters. MC71-CDT grown under conditions that mimic the SCV secreted the holotoxin in outer membrane vesicles (OMVs). Epithelial cells infected with MC71-CDT also secreted OMVs-like vesicles. The release of these extracellular vesicles required an intact SCV and relied on anterograde transport towards the cellular cortex on microtubule and actin tracks. Paracrine internalization of Typhoid toxin-loaded OMVs by bystander cells was dependent on dynamin-1, indicating active endocytosis. The subsequent induction of DNA damage required retrograde transport of the toxin through the Golgi complex. These data provide new insights on the mode of secretion of exotoxins by cells infected with intracellular bacteria.
authors.affiliation: Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Guidi
authors.forename: Laura
authors.initials: L
authors.lastname: Levi
authors.forename: Syed Fazle
authors.initials: SF
authors.lastname: Rouf
authors.forename: Speranta
authors.initials: S
authors.lastname: Puiac
authors.forename: Mikael
authors.initials: M
authors.lastname: Rhen
authors.forename: Teresa
authors.initials: T
authors.lastname: Frisan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism*; D020126:Brefeldin A / Q000494:pharmacology; D018938:Caco-2 Cells; D002460:Cell Line; D004249:DNA Damage; D034284:Dynamin I / Q000037:antagonists & inhibitors / Q000378:metabolism; D034281:Dynamins / Q000037:antagonists & inhibitors; D004705:Endocytosis; D004847:Epithelial Cells / Q000378:metabolism / Q000382:microbiology; D006367:HeLa Cells; D006801:Humans; D006835:Hydrazones / Q000494:pharmacology; D051379:Mice; D011401:Promoter Regions, Genetic; D012485:Salmonella typhi / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D022142:Secretory Vesicles / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D001427:Bacterial Toxins; C000589672:CdtB protein, Salmonella typhimurium; D006835:Hydrazones; C511794:N'-(3,4-dihydroxybenzylidene)-3-hydroxy-2-naphthahydrazide; C000589652:PltA protein, Salmonella typhimurium; C000589671:PltB protein, Salmonella typhimurium; C067044:cytolethal distending toxin; D020126:Brefeldin A; D034284:Dynamin I; D034281:Dynamins