|Pallag G, Nazarian S, Ravasz D, Bui D, Komlódi T, Doerrier C, Gnaiger E, Seyfried TN, Chinopoulos C (2022) Proline oxidation leading to high electron flow through reduction of ubiquinone supports ATP production by F1FO-ATPase in mitochondria with inhibited Complex I. MitoFit Preprints 2022.1.v3. https://doi.org/10.26124/mitofit:2022-0001.v3|
Abstract: Version 3 (v3) 2022-03-07 doi:10.26124/mitofit:2022-0001.v3
In mitochondria expressing proline dehydrogenase (ProDH), oxidation of proline to pyrroline-5-carboxylate (P5C) leads to transfer of electrons to ubiquinone supporting Complexes CIII and CIV, in turn generating the protonmotive force. Further catabolism of P5C forms glutamate that fuels the citric acid cycle yielding reducing equivalents sustaining oxidative phosphorylation. However, P5C and glutamate catabolism depend on CI activity due to NAD+ requirement. The extent of proline oxidation was established in isolated mitochondria of various mouse tissues by means of simultaneously measuring oxygen consumption, membrane potential, NADH and ubiquinone redox state using the NextGen-O2k (Oroboros Instruments) and correlated to ProDH activity and F1FO-ATPase directionality. In CI-inhibited mouse liver and kidney mitochondria exhibiting high levels of proline oxidation and ProDH activity, catabolism of proline generated a sufficiently high membrane potential maintaining F1FO-ATPase operation in forward mode. This was not observed when either CIII or CIV was inhibited, nor during anoxia. Fueling CIII and CIV with duroquinone partially reproduced the effects of proline. Excess glutamate could not reproduce the effects of proline, arguing that they are due to processes upstream of glutamate conversion from proline. The ProDH inhibitors L-tetrahydro-2-furoic acid and to lesser extent S-5-oxo-2-tetrahydrofurancarboxylic acid abolished all effects conferred by proline. It is concluded that proline catabolism through ProDH generates sufficient CIII and CIV proton pumping, supporting ATP production by F1FO-ATPase even when CI is inhibited.
• Keywords: proline dehydrogenase, OXPHOS, substrate-level phosphorylation, quinone • Bioblast editor: Tindle-Solomon L • O2k-Network Lab: AT Innsbruck Oroboros, HU Budapest Chinopoulos C
- Original files are available Open Access at Zenodo repository: https://doi.org/10.5281/zenodo.6323145 (in preparation)
- This work was supported by grants from NKFIH ([TKP2021-EGA-25], FIKP-61822-64888-EATV, VEKOP 2.3.3-15-2016-00012, 2017-2.3.4-TET-RU-2017-00003, KH129567, and K135027) to C.C. and from the project NextGen-O2k (Oroboros Instruments) which has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement Nº 859770.
Labels: MiParea: Respiration, Instruments;methods
Organism: Mouse Tissue;cell: Heart, Nervous system, Liver, Kidney Preparation: Isolated mitochondria
Regulation: Q-junction effect Coupling state: LEAK, OXPHOS Pathway: N, S, NS, Other combinations, ROX HRR: Oxygraph-2k, NextGen-O2k