title: Mitochondrial K(ATP) channel openers activate the ERK kinase by an oxidant-dependent mechanism.
abstract: Extracellular signal-regulated kinases (ERKs) are key regulatory proteins that mediate cell survival, proliferation, and differentiation. Reactive oxygen species (ROS) may play a role in activation of the ERK pathway. Because mitochondria are a major source of ROS, we investigated whether mitochondria-derived ROS play a role in ERK activation. Diazoxide, a potent mitochondrial ATP-sensitive K+ (K(ATP)) channel opener, is known to depolarize the mitochondrial membrane potential and cause a reversible oxidation of respiratory chain flavoproteins, thus increasing mitochondrial ROS production. Using THP-1 cells as a model, we postulated that opening mitochondrial K(ATP) channels would increase production of ROS and, thereby, regulate the activity of the ERK kinase. We found that opening mitochondrial K(ATP) channels by diazoxide induced production of ROS as determined by an increased rate of dihydroethidium and dichlorofluorescein fluorescence. This increased production of ROS was associated with increased phosphorylation of ERK kinase in a time-dependent fashion. The MEK inhibitors PD-98059 and U-0126 blocked ERK activation mediated by diazoxide. N-acetylcysteine, but not diphenyleneiodonium, attenuated ERK activation mediated by diazoxide. Adenovirus-mediated overexpression of manganese superoxide dismutase, which is expressed in mitochondria, decreased the rate of dihydroethidium oxidation as well as ERK activation. We conclude that mitochondrial K(ATP) channel openers trigger ERK activation via mitochondria-derived ROS.
authors.affiliation: Department of Medicine, University of Iowa College of Medicine and Veterans Administration Medical Center, Iowa City, Iowa 52242, USA. lobelia-samavati@uiowa.edu
authors.forename: Lobelia
authors.initials: L
authors.lastname: Samavati
authors.forename: Martha M
authors.initials: MM
authors.lastname: Monick
authors.forename: Salih
authors.initials: S
authors.lastname: Sanlioglu
authors.forename: Garry R
authors.initials: GR
authors.lastname: Buettner
authors.forename: Larry W
authors.initials: LW
authors.lastname: Oberley
authors.forename: Gary W
authors.initials: GW
authors.lastname: Hunninghake
mesh_terms: D000255:Adenosine Triphosphate / Q000502:physiology*; D000256:Adenoviridae / Q000235:genetics; D002460:Cell Line; D003981:Diazoxide / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010766:Phosphorylation; D020110:Pinacidil / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000494:pharmacology
chemical_list: D015221:Potassium Channels; D017382:Reactive Oxygen Species; D020110:Pinacidil; D000255:Adenosine Triphosphate; D013482:Superoxide Dismutase; D020928:Mitogen-Activated Protein Kinases; D003981:Diazoxide