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

The relationship of the inner mitochondrial membrane(IMM) cristaestructure and intracristal space (ICS) to oxidative phosphorylation(oxphos) is not well understood. Mitofilin (subunit Mic60) of the mitochondrial contact site and cristaeorganizing system (MICOS) IMM complex is attached to the outer membrane (OMM) via the sortingand assembly machinery/topogenesis of mitochondrial outer membrane β-barrel proteins (SAM/TOB) complex and controls the shape of the cristae. ATP synthasedimers determine sharp cristaeedges, whereas trimeric OPA1 tightens ICS outlets. Metabolism is altered during hypoxia, and we therefore studied cristaemorphology in HepG2 cells adapted to 5% oxygen for 72 h. Three dimensional (3D), super-resolution biplanefluorescence photoactivation localization microscopywith Eos-conjugated, ICS-located lactamase-β indicated hypoxic ICS expansion with an unchanged OMM (visualized by Eos- mitochondrial fissionprotein-1). 3D direct stochastic optical reconstruction microscopy immunocytoch...