title: IF1, the endogenous regulator of the F(1)F(o)-ATPsynthase, defines mitochondrial volume fraction in HeLa cells by regulating autophagy.
abstract: The protein IF1 limits mitochondrial ATP consumption when mitochondrial respiration is impaired by inhibiting the 'reverse' activity of the F(1)F(o)-ATPsynthase. We have found that IF1 also increases F(1)F(o)-ATPsynthase activity in respiring mitochondria, promoting its dimerization and increasing the density of mitochondrial cristae. We also noted that IF1 overexpression was associated with an increase in mitochondrial volume fraction that was conversely reduced when IF1 was knocked down using small interfering RNA (siRNA). The volume change did not correlate with the level of transcription factors involved in mitochondrial biogenesis. However, autophagy was dramatically increased in the IF1siRNA treated cells (-IF1), assessed by quantifying LC3-GFP translocation to autophagosomes, whilst levels of autophagy were low in IF1 overexpressing cells (+IF1). The increase in LC3-GFP labelled autophagosomes in -IF1 cells was prevented by the superoxide dismutase mimetic, manganese (III) tetrakis (4-benzoic acid) porphyrin (MnTBAP). An increase in the basal rate of generation of reactive oxygen species (ROS) in -IF1 cells was demonstrated using the fluorescent probe dihydroethidium (DHE). Thus, IF1 appears to limit mitochondrial ROS generation, limiting autophagy which is increased by IF1 knockdown. Variations in IF1 expression level may therefore play a significant role in defining both resting rates of ROS generation and cellular mitochondrial content.
authors.affiliation: Department of Cell and Developmental Biology, University College London, UK. mcampanella@rvc.ac.uk
authors.forename: Michelangelo
authors.initials: M
authors.lastname: Campanella
authors.forename: Andreas
authors.initials: A
authors.lastname: Seraphim
authors.forename: Rosella
authors.initials: R
authors.lastname: Abeti
authors.forename: Edward
authors.initials: E
authors.lastname: Casswell
authors.forename: Pedro
authors.initials: P
authors.lastname: Echave
authors.forename: Michael R
authors.initials: MR
authors.lastname: Duchen
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001343:Autophagy / Q000502:physiology*; D016923:Cell Death; D006367:HeLa Cells / Q000378:metabolism*; D006706:Homeostasis; D006801:Humans; D008564:Membrane Potentials / Q000502:physiology; D008928:Mitochondria / Q000201:enzymology / Q000502:physiology / Q000648:ultrastructure; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D000097795:ATPase Inhibitory Protein
chemical_list: D000255:Adenosine Triphosphate; D011506:Proteins; D006180:Proton-Translocating ATPases; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D014157:Transcription Factors; D000097795:ATPase Inhibitory Protein