Forkink 2014 Biochim Biophys Acta
| Forkink M, Manjeri GR, Liemburg-Apers DC, Nibbeling E, Blanchard M, Wojtala A, Smeitink JA, Wieckowski MR, Willems PH, Koopman WJ (2014) Mitochondrial hyperpolarization during chronic Complex I inhibition is sustained by low activity of Complex II, III, IV and V. Biochim Biophys Acta 1837:1247-56. |
Forkink M, Manjeri GR, Liemburg-Apers DC, Nibbeling E, Blanchard M, Wojtala A, Smeitink JA, Wieckowski MR, Willems PH, Koopman WJ (2014) Biochim Biophys Acta
Abstract: The mitochondrial oxidative phosphorylation (OXPHOS) system consists of four electron transport chain (ETC) complexes (CI-CIV) and the FoF1-ATP synthase (CV), which sustain ATP generation via chemiosmotic coupling. The latter requires an inward-directed proton-motive force (PMF) across the mitochondrial inner membrane (mtIM) consisting of a proton (ฮpH) and electrical charge (ฮฯ) gradient. CI actively participates in sustaining these gradients via trans-mtIM proton pumping. Enigmatically, at the cellular level genetic or inhibitor-induced CI dysfunction has been associated with ฮฯ depolarization or hyperpolarization. The cellular mechanism of the latter is still incompletely understood. Here we demonstrate that chronic (24h) CI inhibition in HEK293 cells induces a proton-based ฮฯ hyperpolarization in HEK293 cells without triggering reverse-mode action of CV or the adenine nucleotide translocase (ANT). Hyperpolarization was associated with low levels of CII-driven O2 consumption and prevented by co-inhibition of CII, CIII or CIV activity. In contrast, chronic CIII inhibition triggered CV reverse-mode action and induced ฮฯ depolarization. CI- and CIII-inhibition similarly reduced free matrix ATP levels and increased the cell's dependence on extracellular glucose to maintain cytosolic free ATP. Our findings support a model in which ฮฯ hyperpolarization in CI-inhibited cells results from low activity of CII, CIII and CIV, combined with reduced forward action of CV and ANT. โข Keywords: ATeam, Live-cell microscopy, Respirometry, TMRM, SypHer
โข O2k-Network Lab: NL Nijmegen Koopman WJ, PL Warsaw Szewczyk A
Labels: MiParea: Respiration
Organism: Human
Tissue;cell: HEK
Preparation: Permeabilized cells
Coupling state: LEAK, OXPHOS
Pathway: N, S, CIV, NS, ROX
HRR: Oxygraph-2k
