Robb 2018 J Biol Chem

Robb EL, Hall AR, Prime TA, Eaton S, Szibor M, Viscomi C, James AM, Murphy MP (2018) Control of mitochondrial superoxide production by reverse electron transport at complex I. J Biol Chem 293:9869-79.

» PMID: 29743240 Open Access

Robb EL, Hall AR, Prime TA, Eaton S, Szibor M, Viscomi C, James AM, Murphy MP (2018) J Biol Chem

Abstract: The generation of mitochondrial superoxide (O_2̇^•-)) by reverse electron transport (RET) at complex I causes oxidative damage in pathologies such as ischemia reperfusion injury, but also provides the precursor to H₂O₂ production in physiological mitochondrial redox signaling. Here, we quantified the factors that determine mitochondrial O_2̇^•- production by RET in isolated heart mitochondria. Measuring mitochondrial H₂O₂ production at a range of proton-motive force (Δp) values and for several coenzyme Q (CoQ) and NADH pool redox states obtained with the uncoupler p-trifluoromethoxyphenylhydrazone, we show that O_2̇^•- production by RET responds to changes in O_2̇^•- concentration, the magnitude of Δp, and the redox states of the CoQ and NADH pools. Moreover, we determined how expressing the alternative oxidase from the tunicate Ciona intestinalis to oxidize the CoQ pool affected RET-mediated O_2̇^•- production at complex I, underscoring the importance of the CoQ pool for mitochondrial O_2̇^•- production by RET. An analysis of O_2̇^•- production at complex I as a function of the thermodynamic forces driving RET at complex I revealed that many molecules that affect mitochondrial reactive oxygen species production do so by altering the overall thermodynamic driving forces of RET, rather than by directly acting on complex I. These findings clarify the factors controlling RET-mediated mitochondrial O_2̇^•- production in both pathological and physiological conditions. We conclude that O_2̇^•- production by RET is highly responsive to small changes in Δp and the CoQ redox state, indicating that complex I RET represents a major mode of mitochondrial redox signaling. • Keywords: RET, Coenzyme Q, Complex I, Mitochondria, Mitochondrial membrane potential, Reactive oxygen species (ROS), Redox signaling, Respiration, Reverse electron transport, Superoxide • Bioblast editor: Kandolf G • O2k-Network Lab: FI Helsinki Jacobs HT, IT Padova Viscomi C, DE Jena Szibor M

Labels: MiParea: Respiration, nDNA;cell genetics 

Stress:Oxidative stress;RONS  Organism: Rat  Tissue;cell: Heart  Preparation: Isolated mitochondria 

Coupling state: ET  Pathway: N, S, ROX  HRR: Oxygraph-2k, O2k-Fluorometer 

2018-07, AmR