Autophagy is induced by the type III secretion system of Vibrio alginolyticus in several mammalian cell lines
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ORIGINAL PAPER
Autophagy is induced by the type III secretion system of Vibrio alginolyticus in several mammalian cell lines Zhe Zhao • Lvping Zhang • Chunhua Ren • Jingjing Zhao • Chang Chen • Xiao Jiang • Peng Luo • Chao-Qun Hu
Received: 28 June 2010 / Revised: 7 October 2010 / Accepted: 13 October 2010 / Published online: 3 November 2010 Ó Springer-Verlag 2010
Abstract Vibrio alginolyticus is a gram-negative bacterium and has been recognized as an opportunistic pathogen in marine animals as well as humans. Here, we further characterized a cell death mechanism caused by this bacterium in several mammalian cell lines. The T3SS of V. alginolyticus killed HeLa cells by a very similar cell cytolysis mechanism in fish cells, as evidenced by cell rounding and LDH release; however, DNA fragmentation was not observed. Further studies showed that caspase-1 and caspase-3 were not activated during the T3SS-mediated cell death, indicating that the death mechanism is completely independent of pyroptosis and apoptosis in HeLa cells. Conversely, autophagy was detected during the T3SS-mediated cell death by the appearance of MDC-labeled punctate fluorescence and accumulation of autophagic vesicles. Moreover, western blot analysis revealed increase in conversion of LC3-I to LC3-II in infected mammalian cell lines, confirming that autophagy occurs during the process. Together, these data demonstrate that the death process used by V. alginolyticus in mammalian cells is different from that in fish cells, including induction of autophagy, cell rounding Communicated by David Kelly. Z. Zhao, L. Zhang—contributed equally to this work.
Electronic supplementary material The online version of this article (doi:10.1007/s00203-010-0646-9) contains supplementary material, which is available to authorized users. Z. Zhao L. Zhang C. Ren J. Zhao C. Chen X. Jiang P. Luo C.-Q. Hu (&) Key Laboratory of Applied Marine Biology of Guangdong Province (LAMB) and Key Laboratory of Marine Bio-Resources Sustainable Utilization (LMB), South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, People’s Republic of China e-mail: [email protected]
and osmotic lysis. This study provides some evidences hinting that differences in death mechanism in responses to V. alginolyticus infection may be attributed to the species of infected cells from which it was derived. Keywords Vibrio alginolyticus The type III secretion system (T3SS) Cell death Autophagy Apoptosis Abbreviations CLC Carp leucocyte cell DMEM Dulbecco’s minimal essential medium FHM Fathead minnow epithelial cell EPC Epithelioma papulosum cyprinid FBS Fetal bovine serum LC3 Microtubule-associated protein light chain 3 LDH Lactate dehydrogenase PFA Paraformaldehyde PBS Phosphate-buffered saline MDC Monodansylcadaverine MEM Minimum essential medium with Earle’s balanced salts SDS–PAGE Sodium dodecyl sulfate polyacrylamide gel electrophoresis STS Staurosporine T3SS The type III secretion system TUNEL Terminal deoxynucleotidyl transferasemediated dUTP nic
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