title: Mitoenergetic Dysfunction Triggers a Rapid Compensatory Increase in Steady-State Glucose Flux.
abstract: ATP can be produced in the cytosol by glycolytic conversion of glucose (GLC) into pyruvate. The latter can be metabolized into lactate, which is released by the cell, or taken up by mitochondria to fuel ATP production by the tricarboxylic acid cycle and oxidative phosphorylation (OXPHOS) system. Altering the balance between glycolytic and mitochondrial ATP generation is crucial for cell survival during mitoenergetic dysfunction, which is observed in a large variety of human disorders including cancer. To gain insight into the kinetic properties of this adaptive mechanism we determined here how acute (30 min) inhibition of OXPHOS affected cytosolic GLC homeostasis. GLC dynamics were analyzed in single living C2C12 myoblasts expressing the fluorescent biosensor FLII(12)Pglu-700μδ6 (FLII). Following in situ FLII calibration, the kinetic properties of GLC uptake (V1) and GLC consumption (V2) were determined independently and used to construct a minimal mathematical model of cytosolic GLC dynamics. After validating the model, it was applied to quantitatively predict V1 and V2 at steady-state (i.e., when V1 = V2 = Vsteady-state) in the absence and presence of OXPHOS inhibitors. Integrating model predictions with experimental data on lactate production, cell volume, and O2 consumption revealed that glycolysis and mitochondria equally contribute to cellular ATP production in control myoblasts. Inhibition of OXPHOS induced a twofold increase in Vsteady-state and glycolytic ATP production flux. Both in the absence and presence of OXPHOS inhibitors, GLC was consumed at near maximal rates, meaning that GLC consumption is rate-limiting under steady-state conditions. Taken together, we demonstrate here that OXPHOS inhibition increases steady-state GLC uptake and consumption in C2C12 myoblasts. This activation fully compensates for the reduction in mitochondrial ATP production, thereby maintaining the balance between cellular ATP supply and demand.
authors.affiliation: Department of Biochemistry, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands; Centre for Systems Biology and Bioenergetics, Radboud University and Radboud University Medical Center, Nijmegen, The Netherlands; Nijmegen Center for Mitochondrial Disorders, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Dania C
authors.initials: DC
authors.lastname: Liemburg-Apers
authors.affiliation: Department of Pharmacology and Toxicology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands; Centre for Systems Biology and Bioenergetics, Radboud University and Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Tom J J
authors.initials: TJ
authors.lastname: Schirris
authors.affiliation: Department of Pharmacology and Toxicology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands; Centre for Systems Biology and Bioenergetics, Radboud University and Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Frans G M
authors.initials: FG
authors.lastname: Russel
authors.affiliation: Department of Biochemistry, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands; Centre for Systems Biology and Bioenergetics, Radboud University and Radboud University Medical Center, Nijmegen, The Netherlands; Nijmegen Center for Mitochondrial Disorders, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Peter H G M
authors.initials: PH
authors.lastname: Willems
authors.affiliation: Department of Biochemistry, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands; Centre for Systems Biology and Bioenergetics, Radboud University and Radboud University Medical Center, Nijmegen, The Netherlands; Nijmegen Center for Mitochondrial Disorders, Radboud University Medical Center, Nijmegen, The Netherlands. Electronic address: werner.koopman@radboudumc.nl.
authors.forename: Werner J H
authors.initials: WJ
authors.lastname: Koopman
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002952:Citric Acid Cycle / Q000187:drug effects / Q000502:physiology*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology; D007700:Kinetics; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D008954:Models, Biological; D032446:Myoblasts / Q000187:drug effects / Q000378:metabolism; D010085:Oxidative Phosphorylation / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology
chemical_list: D000255:Adenosine Triphosphate; D005947:Glucose