title: Type III secretion system 1 of Vibrio parahaemolyticus induces oncosis in both epithelial and monocytic cell lines.
abstract: The Vibrio parahaemolyticus type III secretion system 1 (T3SS1) induces cytotoxicity in mammalian epithelial cells. We characterized the cell death phenotype in both epithelial (HeLa) and monocytic (U937) cell lines following infection with V. parahaemolyticus. Using a combination of the wild-type strain and gene knockouts, we confirmed that V. parahaemolyticus strain NY-4 was able to induce cell death in both cell lines via a T3SS1-dependent mechanism. Bacterial contact, but not internalization, was required for T3SS1-induced cytotoxicity. The mechanism of cell death involves formation of a pore structure on the surface of infected HeLa and U937 cells, as demonstrated by cellular swelling, uptake of cell membrane-impermeable dye and protection of cytotoxicity by osmoprotectant (PEG3350). Western blot analysis showed that poly ADP ribose polymerase (PARP) was not cleaved and remained in its full-length active form. This result was evident for seven different V. parahaemolyticus strains. V. parahaemolyticus-induced cytotoxicity was not inhibited by addition of the pan-caspase inhibitor carbobenzoxy-valyl-alanyl-aspartyl-[O-methyl]-fluoromethylketone (Z-VAD-FMK) or the caspase-1 inhibitor N-acetyl-tyrosyl-valyl-alanyl-aspartyl-aldehyde (Ac-YVAD-CHO); thus, caspases were not involved in T3SS1-induced cytotoxicity. DNA fragmentation was not evident following infection and autophagic vacuoles were not observed after monodansylcadaverine staining. We conclude that T3SS1 of V. parahaemolyticus strain NY-4 induces a host cell death primarily via oncosis rather than apoptosis, pyroptosis or autophagy.
authors.affiliation: Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, USA.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Zhou
authors.affiliation: School of Molecular Biosciences, Washington State University, Pullman, WA, USA.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Konkel
authors.affiliation: Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, USA.
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Call
mesh_terms: D001343:Autophagy; D001426:Bacterial Proteins / Q000378:metabolism; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects / Q000235:genetics*; D004847:Epithelial Cells / Q000382:microbiology* / Q000648:ultrastructure; D006367:HeLa Cells; D006801:Humans; D046529:Microscopy, Electron, Transmission; D009000:Monocytes / Q000382:microbiology* / Q000648:ultrastructure; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D020298:U937 Cells; D014735:Vibrio Infections / Q000235:genetics*; D014736:Vibrio parahaemolyticus / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*
chemical_list: D001426:Bacterial Proteins; D061945:Caspase Inhibitors; D011065:Poly(ADP-ribose) Polymerases; D020169:Caspases