Mitochondrial F ₁ F _O ATP synthase determines the local proton motive force at cristae rims

Abstract

The classical view of oxidative phosphorylation is that a proton motive force (PMF) generated by the respiratory chain complexes fuels ATP synthesis via ATP synthase. Yet, under glycolytic conditions, ATP synthase in its reverse mode also can contribute to the PMF. Here, we dissected these two functions of ATP synthase and the role of its inhibitory factor 1 (IF1) under different metabolic conditions. pH profiles of mitochondrial sub-compartments were recorded with high spatial resolution in live mammalian cells by positioning a pH sensor directly at ATP synthase's F 1 and F O subunits, complex IV and in the matrix. Our results clearly show that ATP synthase activity substantially controls the PMF and that IF1 is essential under OXPHOS conditions to prevent reverse ATP synthase activity due to an almost negligible ΔpH. In addition, we show how this changes lateral, transmembrane, and radial pH gradients in glycolytic and respiratory cells.

Inhibition of ATP synthase reverse activity restores energy homeostasis in mitochondrial pathologies

“…In isolated mitochondria, synthetic and reverse hydrolytic activities of ATP synthase were measured in the same preparation and showed that under different states of respiration and membrane potential, heterogeneous function of ATP synthase can co-exist in coupled mitochondria. Accumulating evidence supports the possibility that ATP hydrolysis can occur heterogeneously in the cell and even within individual mitochondrion simultaneously with ATP synthesis (Wolf et al, 2019;Salewskij et al, 2020;Rieger et al, 2021). Moreover, the inhibition of ATP synthase function was shown to impact the spatiotemporal organization of ATP synthase (Weissert et al, 2021), which can regulate the PMF locally (Rieger et al, 2021).…”

The ATPase Inhibitory Factor 1 is a Tissue-Specific Physiological Regulator of the Structure and Function of Mitochondrial ATP Synthase: A Closer Look Into Neuronal Function

“…Moreover, the existence of the two pools of the ATP synthase could contribute to the heterogeneity in ΔΨm ( Wolf et al, 2019 ) and ΔpH ( Rieger et al, 2021 ) that has been recently reported in mitochondrial cristae by high spatial resolution microscopy. The active and inactive fractions of ATP synthase could be in functionally independent cristae, or even in different regions within the same cristae, thereby contributing to the differences in ΔΨm and ΔpH that affect the overall activity of oxidative phosphorylation ( Figure 2C ).…”

Cell-imaging studies of highly substituted oxazole derivatives as organelle targeting fluorophores (OTFPs)

“…So, it is extremely important to maintain mitochondrial membrane potential. Its depletion results in mitochondrial as well as cellular death 16 . The synthesized dyes were localized inside the mitochondria due to electrostatic interaction between negatively charged MMP and positively charged dye 14 .…”