Komlodi 2018 AussieMit

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Komlodi T, Hunger M, Moore AL, Gnaiger E (2018) Electron transfer at the Q-junction: new perspectives from combined measurement of mitochondrial O2 flux, H2O2 flux, and coenzyme Q redox state. AussieMit 2018 Melbourne AU.

Link: AussieMit

Komlodi T, Hunger M, Moore AL, Gnaiger E (2018)

Event: AussieMit 2018 Melbourne AU

The coenzyme Q-junction upstream of Complex III is a key point of convergent electron flow from mt-dehydrogenases via Complex I (CI), succinate (S) via Complex II, and glycerol-3-phosphate (Gp) via mt-glycerophosphate dehydrogenase. Deficiency in the Q-junction impairs electron transfer and OXPHOS capacities, while the extent of the inhibition is determined by the fuel substrate type and electron transfer pathways, which results in an altered Q redox state. We analyzed the relationship between the Q redox state, H2O2 and O2 fluxes with fuel substrates provided separately and in combination, thus varying the electron pressure on the Q pool.

Mitochondrial respiration and H2O2 production were determined simultaneously by high-resolution respirometry (HRR; Oroboros Instruments, Innsbruck, Austria), whereas the redox state of Q (Qreduced/Qtotal=Qr/Qt) was detected using a three-electrode system inserted into the Oroboros Q2k prototype. Mitochondria isolated from mouse brain were supplied with S (0.2, 10 or 50 mM), Gp (20 mM), or their combinations, either in the absence (LEAK) or presence of saturating [ADP] (OXPHOS).

We found a linear relationship between Qr/Qt and O2 flux in OXPHOS, and between H2O2 flux in LEAK and O2 flux in OXPHOS. All parameters increased with succinate concentration in LEAK and OXPHOS. H2O2 flux was highest with S50&Gp and S10&Gp in LEAK, while respiration was highest with the same substrates in OXPHOS. Q was most reduced in LEAK with S50. Taken together, substrate combinations exerted an additive effect on H2O2 generation and respiration, but not on Qr/Qt. S-supported H2O2 flux, Qr/Qt and respiration depended on S concentration and S&Gp combination: Gp < S0.2 < S10 < S50 and S0.2Gp < S10Gp ~ S50Gp.

Electron pressure generated by S and Gp separately, or S&Gp in combination on the Q-junction controls respiration and regulates H2O2 flux by reversed electron transfer through the Q pool to CI.


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


Labels: MiParea: Respiration 


Organism: Mouse  Tissue;cell: Nervous system  Preparation: Isolated mitochondria 

Regulation: Redox state, Substrate, Q-junction effect  Coupling state: LEAK, OXPHOS  Pathway: S, Gp  HRR: Oxygraph-2k 


Affiliations

Komlòdi T(1), Hunger M(1), Moore AL(2), Gnaiger E(1,3)

  1. Oroboros Instruments, Innsbruck, Austria
  2. Biochemistry Medicine School Life Sciences, Univ Sussex, Brighton, United Kingdom
  3. Daniel Swarovski Research Lab, Mitochondrial Physiology, Dept Visceral, Transplant Thoracic Surgery Medical Univ Innsbruck, Innsbruck, Austria