Functional F1-ATPase essential in maintaining growth and membrane potential of human mitochondrial DNA-depleted ρ°cells

Abstract

F1-ATPase assembly has been studied in human ρ°cells devoid of mitochondrial DNA (mtDNA). Since, in these cells, oxidative phosphorylation cannot provide ATP, their growth relies on glycolysis. Despite the absence of the mtDNA-coded F0 subunits 6 and 8, ρ°cells possessed normal levels of F1- ATPase α and β subunits. This F1-ATPase was functional and azide- or aurovertin-sensitive but oligomycin-insensitive. In addition, aurovertin decreased cell growth in ρ°cells and also reduced their mitochondrial membrane potential, as measured by rhodamine 123 fluorescence. Therefore, a functional F1-ATPase was important to maintain the mitochondrial membrane potential and the growth of these ρ°cells. Bongkrekic acid, a specific adenine nucleotide translocator (ANT) inhibitor, also reduced ρ°cell growth and mitochondrial membrane potential. In conclusion, p cells need both a functional F1-ATPase and a functional ANT to maintain their mitochondrial membrane potential, which is necessary for their growth. ATP hydrolysis catalyzed by F1 must provide ADP3- at a sufficient rate to maintain a rapid exchange with the glycolyric ATP4- by ANT, this electrogenic exchange inducing a mitochondrial membrane potential efficient enough to sustain cell growth. However, since the effects of bongkrekic acid and of aurovertin were additive, other electrogenic pumps should cooperate with this pathway.