Hypoxic HepG2 cell adaptation decreases ATP synthase dimers and ATP production in inflated cristae by mitofilin down-regulation concomitant to MICOS clustering

0459830 - FGÚ 2017 RIV US eng J - Journal Article
Plecitá-Hlavatá, Lydie - Engstová, Hana - Alán, Lukáš - Špaček, Tomáš - Dlasková, Andrea - Smolková, Katarína - Špačková, Jitka - Tauber, Jan - Strádalová, Vendula - Malínský, Jan - Lessard, M. - Bewersdorf, J. - Ježek, Petr
Hypoxic HepG2 cell adaptation decreases ATP synthase dimers and ATP production in inflated cristae by mitofilin down-regulation concomitant to MICOS clustering.
FASEB Journal. Roč. 30, č. 5 (2016), s. 1941-1957. ISSN 0892-6638. E-ISSN 1530-6860
R&D Projects: GA ČR(CZ) GA13-02033S; GA ČR GJ15-02022Y
Institutional support: RVO:67985823 ; RVO:68378041
Keywords : Mitofilin * Mic60 * OPA1 * dSTORM * 3D immunocytochemistry * electron microscopy * mitochondrial cristae morphology
Subject RIV: EA - Cell Biology
Impact factor: 5.498, year: 2016

The relationship of the inner mitochondrial membrane (IMM) cristae structure and intracristal space (ICS) to oxidative phosphorylation (oxphos) is not well understood. Mitofilin (subunit Mic60) of the mitochondrial contact site and cristae organizing system (MICOS) IMM complex is attached to the outer membrane (OMM) via the sorting and assembly machinery/topogenesis of mitochondrial outer membrane beta-barrel proteins (SAM/TOB) complex and controls the shape of the cristae. ATP synthase dimers determine sharp cristae edges, whereas trimeric OPA1 tightens ICS outlets. Metabolism is altered during hypoxia, and we therefore studied cristae morphology in HepG2 cells adapted to 5% oxygen for 72 h. Three dimensional (3D), super-resolution biplane fluorescence photoactivation localization microscopy with Eos-conjugated, ICS-located lactamase-beta indicated hypoxic ICS expansion with an unchanged OMM (visualized by Eos-mitochondrial fission protein-1). 3D direct stochastic optical reconstruction microscopy immunocytochemistry revealed foci of clustered mitofilin (but not MICOS subunit Mic19) in contrast to its even normoxic distribution. Mitofilin mRNA and protein decreased by approx. 20%. ATP synthase dimers vs. monomers and state-3/state-4 respiration ratios were lower during hypoxia. Electron microscopy confirmed ICS expansion (maximum in glycolytic cells), which was absent in reduced or OMM-detached cristae of OPA1- and mitofilin-silenced cells, respectively. Hypoxic adaptation is reported as rounding sharp cristae edges and expanding cristae width (ICS) by partial mitofilin/Mic60 down-regulation. Mitofilin-depleted MICOS detaches from SAM while remaining MICOS with mitofilin redistributes toward higher interdistances. This phenomenon causes partial oxphos dormancy in glycolytic cells via disruption of ATP synthase dimers.
Permanent Link: http://hdl.handle.net/11104/0259995