Komlodi 2022 Q10 Hamburg

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Komlodi T, Cardoso LHD, Doerrier C, Moore AL, Rich PR, Gnaiger E (2022) The mitochondrial Q-junction and coenzyme Q pools: Continuous monitoring of pull and push control of respiration and redox state of the Q-mimetic CoQ2. Q10 Hamburg.

Link: 10th Conference of the International Coenzyme Q10 Association

Komlodi T, Cardoso LHD, Doerrier C, Moore AL, Rich PR, Gnaiger E (2022)

Event: 10th Conference of the International Coenzyme Q10 Association 2022 Hamburg DE

Redox states of the mitochondrial coenzyme Q pool, which reacts with the electron transfer system (ETS), reflect the balance between (1) the push exerted by reducing capacities of the ETS from fuel substrates converging at the Q-junction, and (2) the pull of oxidative capacities of the ETS downstream of Q to O2 combined with the load on the OXPHOS system utilizing or dissipating the protonmotive force. A three-electrode sensor was implemented into the Oroboros NextGen-O2k to monitor continuously the redox state of CoQ2 added as a Q-mimetic simultaneously with O2 consumption (Komlódi et al, Bioenerg Commun 2021.3).

The mitochondrial CoQ pool is partitioned into inactive mtCoQ and ETS-reactive Q. In the latter Q pool, Qfree behaves according to the fluid-state model (random-collision model), whereas supercomplexed Q is bound to supercomplexes according to the solid-state model. CoQ2 equilibrates in the same manner as the Q pool at Complexes CI, CII and CIII. The glassy carbon working electrode is poised at the CoQ2 oxidation or reduction peak potential, as determined by cyclic voltammetry, allowing the redox state of the CoQ2 to be monitored continuously from the current. The voltammogram also provides quality control of the Q-sensor and reveals chemical interferences.

In our study of isolated mouse cardiac and brain mitochondria, CoQ2 was more oxidized when O2 flux was stimulated by coupling control: when energy demand (pull) increased from LEAK to OXPHOS and ET capacity (succinate pathway). In contrast, CoQ2 was more reduced when O2 flux was stimulated by pathway-control of electron input capacities (push), increasing from the NADH (N)- to succinate (S)-linked pathway which converge at the Q-junction, with CI-Q-CIII and CII-Q-CIII segments, respectively. N- and S- respiratory pathway capacities were not completely additive (Gnaiger, Bioenerg Commun 2020.2), as a necessary although not sufficient indication of Q partitioning intermediary between the solid-state and liquid-state models of supercomplex organization. The direct proportionality of CoQ2 reduction and electron transfer capacities through the CI-Q-CIII and CII-Q-CIII segments suggests that CoQ2 is accurately mimicking mitochondrial Q-redox changes.

Electrochemical monitoring of the redox state of the ETS-reactive Q-pool adds a further dimension to coupling- and pathway-control analysis of isolated mitochondria. The NextGen-O2k enables real-time monitoring of redox changes of the ETS-reactive Q-pool without interference by the inactive mtCoQ-pool. This powerful approach expands studies in mitochondrial physiology providing a greater insight into the role and regulation of mitochondrial function in health and disease.


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Affiliations and support

Timea Komlódi1, Luiza H.D. Cardoso1, Carolina Doerrier1, Anthony L Moore2, Peter R Rich3, Erich Gnaiger1*
  1. Oroboros Instruments, Innsbruck, Austria; *presenting author – erich.gnaiger@oroboros.at
  2. Biochemistry and Medicine, School of Life Sciences, Univ Sussex, Falmer, Brighton, UK
  3. Dept Structural and Molecular Biol, Univ College London, London, UK
This work was part of the NextGen-O2k project, with funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement nº 859770.