title: Mitochondria in peroxisome-deficient hepatocytes exhibit impaired respiration, depleted DNA, and PGC-1α independent proliferation.
abstract: The tight interrelationship between peroxisomes and mitochondria is illustrated by their cooperation in lipid metabolism, antiviral innate immunity and shared use of proteins executing organellar fission. In addition, we previously reported that disruption of peroxisome biogenesis in hepatocytes severely impacts on mitochondrial integrity, primarily damaging the inner membrane. Here we investigated the molecular impairments of the dysfunctional mitochondria in hepatocyte selective Pex5 knockout mice. First, by using blue native electrophoresis and in-gel activity stainings we showed that the respiratory complexes were differentially affected with reduction of complexes I and III and incomplete assembly of complex V, whereas complexes II and IV were normally active. This resulted in impaired oxygen consumption in cultured Pex5(-/-) hepatocytes. Second, mitochondrial DNA was depleted causing an imbalance in the expression of mitochondrial- and nuclear-encoded subunits of the respiratory chain complexes. Third, mitochondrial membranes showed increased permeability and fluidity despite reduced content of the polyunsaturated fatty acid docosahexaenoic acid. Fourth, the affected mitochondria in peroxisome deficient hepatocytes displayed increased oxidative stress. Acute deletion of PEX5 in vivo using adeno-Cre virus phenocopied these effects, indicating that mitochondrial perturbations closely follow the loss of functional peroxisomes in time. Likely to compensate for the functional impairments, the volume of the mitochondrial compartment was increased several folds. This was not driven by PGC-1α but mediated by activation of PPARα, possibly through c-myc overexpression. In conclusion, loss of peroxisomal metabolism in hepatocytes perturbs the mitochondrial inner membrane, depletes mitochondrial DNA and causes mitochondrial biogenesis independent of PGC-1α.
authors.affiliation: KU Leuven - University of Leuven, Department of Pharmaceutical and Pharmacological Sciences, Laboratory of Cell Metabolism, B-3000 Leuven, Belgium.
authors.forename: Annelies
authors.initials: A
authors.lastname: Peeters
authors.affiliation: KU Leuven - University of Leuven, Department of Pharmaceutical and Pharmacological Sciences, Laboratory of Cell Metabolism, B-3000 Leuven, Belgium.
authors.forename: Abhijit Babaji
authors.initials: AB
authors.lastname: Shinde
authors.affiliation: KU Leuven - University of Leuven, Department of Pharmaceutical and Pharmacological Sciences, Laboratory of Cell Metabolism, B-3000 Leuven, Belgium.
authors.forename: Ruud
authors.initials: R
authors.lastname: Dirkx
authors.affiliation: Department of Paediatrics, Division of Paediatric Neurology and Metabolism, University Hospital Ghent, B-9000 Ghent, Belgium.
authors.forename: Joél
authors.initials: J
authors.lastname: Smet
authors.affiliation: KU Leuven - University of Leuven, Department of Oncology, Laboratory of Angiogenesis and Neurovascular Link, B-3000 Leuven, Belgium; VIB, Vesalius Research Center, Laboratory of Angiogenesis and Neurovascular Link, B-3000 Leuven, Belgium.
authors.forename: Katrien
authors.initials: K
authors.lastname: De Bock
authors.affiliation: Dept Basic Medical Sciences, UGhent, B-9000 Ghent, Belgium.
authors.forename: Marc
authors.initials: M
authors.lastname: Espeel
authors.affiliation: KU Leuven - University of Leuven, Department of Cellular and Molecular Medicine, Laboratory of Intensive Care Medicine, B-3000 Leuven, Belgium.
authors.forename: Ilse
authors.initials: I
authors.lastname: Vanhorebeek
authors.affiliation: Department of Paediatrics, Division of Paediatric Neurology and Metabolism, University Hospital Ghent, B-9000 Ghent, Belgium.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Vanlander
authors.affiliation: Department of Paediatrics, Division of Paediatric Neurology and Metabolism, University Hospital Ghent, B-9000 Ghent, Belgium.
authors.forename: Rudy
authors.initials: R
authors.lastname: Van Coster
authors.affiliation: KU Leuven - University of Leuven, Department of Oncology, Laboratory of Angiogenesis and Neurovascular Link, B-3000 Leuven, Belgium; VIB, Vesalius Research Center, Laboratory of Angiogenesis and Neurovascular Link, B-3000 Leuven, Belgium.
authors.forename: Peter
authors.initials: P
authors.lastname: Carmeliet
authors.affiliation: KU Leuven - University of Leuven, Department of Cellular and Molecular Medicine, Laboratory for Lipid Biochemistry and Protein Interactions, B-3000 Leuven, Belgium.
authors.forename: Marc
authors.initials: M
authors.lastname: Fransen
authors.affiliation: KU Leuven - University of Leuven, Department of Cellular and Molecular Medicine, Laboratory for Lipid Biochemistry and Protein Interactions, B-3000 Leuven, Belgium.
authors.forename: Paul P
authors.initials: PP
authors.lastname: Van Veldhoven
authors.affiliation: KU Leuven - University of Leuven, Department of Pharmaceutical and Pharmacological Sciences, Laboratory of Cell Metabolism, B-3000 Leuven, Belgium. Electronic address: myriam.baes@pharm.kuleuven.be.
authors.forename: Myriam
authors.initials: M
authors.lastname: Baes
mesh_terms: D000818:Animals; D002451:Cell Compartmentation; D049109:Cell Proliferation; D019069:Cell Respiration; D004272:DNA, Mitochondrial / Q000378:metabolism*; D004579:Electron Transport; D017353:Gene Deletion; D022781:Hepatocytes / Q000378:metabolism* / Q000648:ultrastructure; D008055:Lipids / Q000737:chemistry; D008560:Membrane Fluidity; D018345:Mice, Knockout; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D010084:Oxidation-Reduction; D010085:Oxidative Phosphorylation; D018384:Oxidative Stress; D047493:PPAR alpha / Q000378:metabolism; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D000074435:Peroxisome-Targeting Signal 1 Receptor; D020675:Peroxisomes / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000172:deficiency / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D004272:DNA, Mitochondrial; D008055:Lipids; D047493:PPAR alpha; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D000074435:Peroxisome-Targeting Signal 1 Receptor; C000614265:Pex5 protein, mouse; C485290:Ppargc1a protein, mouse; D021122:Protein Subunits; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors
keywords: Biogenesis; Mitochondrial DNA; Oxidative phosphorylation; PGC-1α; PPARα; Peroxisomes