Cardoso 2023 MiP2023
| Cardoso Luiza HD (2023) Electron transfer from beta-oxidation and TCA cycle and impact of OXPHOS coupling on NADH and coenzyme Q redox states. MiPschool Obergurgl 2023. |
Link: MiPschool Obergurgl 2023
Cardoso Luiza HD (2023)
Event: MiPschool Obergurgl 2023
Authors:
Introduction: Multiple mt-matrix dehydrogenases reduce NAD+ to NADH+H+, which is oxidized by CI (N-junction). Convergent electron flow through several mt-Complexes (CI, CII, CETF, etc) reduces electron transfer system (ETS)-reactive ubiquinone (UQ) to ubiquinol (UQH2), which is oxidized by CIII (Q-junction). The aim of our study was to analyze the relationships between the N- and Q-redox states and electron transfer rates.
Methods: Respiration and N- or Q-redox fractions were measured simultaneously with the Oroboros NextGen-O2k. Multiple protocols were used with sequential titrations of substrates, inhibitors, and uncouplers [1, 2]: N-pool with pyruvate&glutamate&malate, mouse liver mitochondria; Q-pool with succinate&rotenone, octanoylcarnitine&malate or palmitoylcarnitine&malate, permeabilized HEK 293T. After substrates, ADP, CCCP and antimycin A were titrated.
Results and discussion: Varying energy supply upstream of the Q-junction by using combinations of substrates and ETS-inhibitors in the noncoupled state, the Q-pool became reduced in direct proportion to respiration. In contrast, varying downstream energy demand in the absence of ADP (LEAK), by ADP activation (OXPHOS), and by uncoupler titrations (ET capacity), the N- and Q-pools were reduced in indirect proportion to respiration. The opposite correlations between redox state and respiratory rate were explained by the contrasting effects of varying electron push from different fuel substrates of the ETS or electron pull modulated by coupling and corresponding energy demand. Special emphasis on the interaction between fatty acid oxidation, CI, and CII – all involving separate electron entries into the Q-junction [3] – is particularly relevant in the context of obesity and bioenergetics studies.
• Keywords: Coenzyme Q, NADH, electron transfer system, OXPHOS, respirometry
• O2k-Network Lab: AT Innsbruck Oroboros
Labels: MiParea: Respiration
Coupling state: OXPHOS
HRR: NextGen-O2k
