Ravasz 2019 Abstract IOC141

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Ravasz D, Bui D, Kitayev A, Greenwood B, Hill C, Komlodi T, Doerrier C, Ozohanics O, Moore AL, Gnaiger E, Kiebish M, Kolev K, Seyfried TN, Willis WT, Narain N, Adam-Vizi V, Chinopoulos C (2019) Endogenous quinones sustain a moderate NADH oxidation by complex I during anoxia. Mitochondr Physiol Network 24.02.

Link: IOC141

Ravasz D, Bui D, Kitayev A, Greenwood B, Hill C, Komlodi T, Doerrier C, Ozohanics O, Moore AL, Gnaiger E, Kiebish M, Kolev K, Seyfried TN, Willis WT, Narain N, Adam-Vizi V, Chinopoulos C (2019)

Event: IOC141

Anoxia leads to over-reduction of mitochondrial quinone pools hampering complex I from oxidizing NADH, leading to a profound decrease in the matrix NAD+/NADH ratio. As a consequence of this, the function of matrix dehydrogenases is impaired. Yet, under certain anoxic conditions catabolism of metabolites converging through the ketoglutarate dehydrogenase complex (KGDHC) is known to occur yielding succinyl-CoA, in turn supporting substrate-level phosphorylation substantiated by succinate-CoA ligase. Here, by measuring simultaneously oxygen partial pressure and NADH autofluorescence or quinone redox state we show that in isolated mitochondria complex I utilizes endogenous quinones oxidizing NADH during anoxia. Untargeted metabolomic analysis of matrix metabolites of anoxic mitochondria and in the presence of ETC inhibitors inferred that NAD+ arising from complex I is utilized by KGDHC yielding succinyl-CoA for succinate-CoA ligase, thus maintaining substrate-level phosphorylation during anoxia. The amount of endogenous quinones was estimated to be in the millimolar range and was unaffected by dietary intake of vitamin K3 (menadione). The quinone pools could be reduced by complexes I and II and the electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO) system during anoxia, exhibiting a descending order of affinity and reciprocally, increasing order of capacity. Our results highlight the importance of quinone availability in conjunction to complex I-mediated NADH oxidation in maintaining substrate-level phosphorylation during anoxia.


Bioblast editor: Plangger M O2k-Network Lab: UK Brighton Moore AL, AT Innsbruck Oroboros, AT Innsbruck Gnaiger E, HU Budapest Chinopoulos C


Labels: MiParea: Respiration, Instruments;methods 


Organism: Mouse  Tissue;cell: Liver  Preparation: Isolated mitochondria  Enzyme: Complex I, TCA cycle and matrix dehydrogenases 


Pathway: N, S, Other combinations  HRR: NextGen-O2k 


Affiliations

Ravasz D(1), Bui D(1), Kitayev A(2), Greenwood B(2), Hill C(2), Komlodi T(3), Doerrier C(3), Ozohanics O(1), Moore AL(4), Gnaiger E(3,5), Kiebish M(2), Kolev K(1), Seyfried TN(6), Willis WT(7), Narain N(2), Adam-Vizi V(1), Chinopoulos C(1)
  1. Dept Medical Biochemistry, Semmelweis Univ, Budapest, Hungary
  2. BERG LLC, Framingham, MA, USA
  3. Oroboros Instruments, Innsbruck, Austria
  4. Depart Biochemistry Molecular Biology, School Life Sciences, Univ Sussex, Brighton, UK
  5. Daniel Swarovski Research Lab, Mitochondrial Physiology, Dept Visceral, Transplant Thoracic Surgery, Medical Univ Innsbruck, Innsbruck, Austria
  6. Biology Dept, Boston College, Chestnut Hill, Boston, MA, USA
  7. Univ Arizona, College Medicine, Dept Medicine, Tucson, AZ, USA