title: Are mitochondrial reactive oxygen species required for autophagy?
abstract: Reactive oxygen species (ROS) are said to participate in the autophagy signaling. Supporting evidence is obscured by interference of autophagy and apoptosis, whereby the latter heavily relies on ROS signaling. To dissect autophagy from apoptosis we knocked down expression of cytochrome c, the key component of mitochondria-dependent apoptosis, in HeLa cells using shRNA. In cytochrome c deficient HeLa1.2 cells, electron transport was compromised due to the lack of electron shuttle between mitochondrial respiratory complexes III and IV. A rapid and robust LC3-I/II conversion and mitochondria degradation were observed in HeLa1.2 cells treated with staurosporine (STS). Neither generation of superoxide nor accumulation of H(2)O(2) was detected in STS-treated HeLa1.2 cells. A membrane permeable antioxidant, PEG-SOD, plus catalase exerted no effect on STS-induced LC3-I/II conversion and mitochondria degradation. Further, STS caused autophagy in mitochondria DNA-deficient ρ° HeLa1.2 cells in which both electron transport and ROS generation were completely disrupted. Counter to the widespread view, we conclude that mitochondrial ROS are not required for the induction of autophagy.
authors.affiliation: Center for Free Radical and Antioxidant Health, Department of Environmental and Occupational Health, University of Pittsburgh, PA 15219, USA. jjf73@pitt.edu
authors.forename: Jianfei
authors.initials: J
authors.lastname: Jiang
authors.forename: Akihiro
authors.initials: A
authors.lastname: Maeda
authors.forename: Jing
authors.initials: J
authors.lastname: Ji
authors.forename: Catherine J
authors.initials: CJ
authors.lastname: Baty
authors.forename: Simon C
authors.initials: SC
authors.lastname: Watkins
authors.forename: Joel S
authors.initials: JS
authors.lastname: Greenberger
authors.forename: Valerian E
authors.initials: VE
authors.lastname: Kagan
mesh_terms: D001343:Autophagy / Q000187:drug effects; D045304:Cytochromes c / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D019311:Staurosporine / Q000494:pharmacology
chemical_list: D004272:DNA, Mitochondrial; D017382:Reactive Oxygen Species; D045304:Cytochromes c; D019311:Staurosporine