title: Cytochrome bc(1) regulates the mitochondrial permeability transition by two distinct pathways.
abstract: The mitochondrial permeability transition (MPT) pore is a calcium-sensitive channel in the mitochondrial inner membrane that plays a crucial role in cell death. Here we show that cytochrome bc(1) regulates the MPT in isolated rat liver mitochondria and in CEM and HL60 cells by two independent pathways. Glutathione depletion activated the MPT via increased production of reactive oxygen species (ROS) generated by cytochrome bc(1). The ROS producing mechanism in cytochrome bc(1) involves movement of the "Rieske" iron-sulfur protein subunit of the enzyme complex, because inhibition of cytochrome bc(1) by pharmacologically blocking iron-sulfur protein movement completely abolished ROS production, MPT activation, and cell death. The classical inhibitor of the MPT, cyclosporine A, had no protective effect against MPT activation. In contrast, the calcium-activated, cyclosporine A-regulated MPT in rat liver mitochondria was also blocked with inhibitors of cytochrome bc(1). These results indicate that electron flux through cytochrome bc(1) regulates two distinct pathways to the MPT, one unregulated and involving mitochondrial ROS and the other regulated and activated by calcium.
authors.affiliation: Department of Biochemistry, National University of Singapore, Singapore 117597, Singapore. bchjsa@nus.edu.sg
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Armstrong
authors.forename: Hongyuan
authors.initials: H
authors.lastname: Yang
authors.forename: Wei
authors.initials: W
authors.lastname: Duan
authors.forename: Matthew
authors.initials: M
authors.lastname: Whiteman
mesh_terms: D000818:Animals; D000968:Antimycin A / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020134:Catalytic Domain; D016923:Cell Death / Q000502:physiology; D014450:Electron Transport Complex III / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005434:Flow Cytometry; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D007473:Ion Channels / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D011090:Polyenes / Q000494:pharmacology; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D014451:Ubiquinone / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D007473:Ion Channels; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D011090:Polyenes; D017382:Reactive Oxygen Species; D014451:Ubiquinone; D000968:Antimycin A; C041573:stigmatellin; D014450:Electron Transport Complex III; D005978:Glutathione; C003741:ubiquinol; D002118:Calcium