Inhibition by Ca2+ of the hydrolysis and the synthesis of ATP in Ehrlich ascites tumour mitochondria: relation to the Crabtree effect

Abstract

Phosphorylation of ADP and hydrolysis of ATP by isolated mitochondria from Ehrlich ascites tumour cells is greatly reduced when the mitochondria have been preloaded with Ca2+ (50 nmol/mg protein or more). Translocation of ADP is diminished in Ca(2+)-loaded mitochondria. However, ATPase in toluene-permeabilized mitochondria and in inside-out submitochondrial particles is also strongly inhibited by micromolar concentrations of Ca2+, indicating that, independently of adenine nucleotide transport, F1Fo-ATPase is also affected. ATP hydrolysis by submitochondrial particles depleted of the inhibitory subunit of F1Fo-ATPase (the Pullman-Monroy protein inhibitor) is insensitive to Ca2+; however, this sensitivity is restored when the particles are supplemented with the inhibitory subunit isolated from beef heart mitochondria. In view of the previous observations that glucose elicits in Ehrlich ascites tumour cells an increase of cytoplasmic free Ca2+ (Teplova, V.V., Bogucka, K., Czyz, A., Evtodienko, Yu.V., Duszyński, J. and Wojtczak, L. (1993) Biochem. Biophys. Res. Commun. 196, 1148-1154) and that this calcium is then taken up by mitochondria, resulting in a strong inhibition of coupled respiration (Evtodienko, Yu.V., Teplova, V.V., Duszyński, J., Bogucka, K. and Wojtczak, L. (1994) Cell Calcium 15, 439-446), the present results are discussed in terms of the mechanism of the Crabtree effect in tumour cells.

Calcium-dependent physiologic and pathologic stimulus-metabolic response coupling in hepatocytes

“…Hormone-evoked increases in ΔΨ m and ΔpH m occurred even in the presence of oligomycin to block proton flux through the F1-Fo ATP synthetase. These results indicate that the prolonged increase in mitochondrial PMF could not be explained by Ca 2+ -dependent inhibition of proton flux through the Fo subunit, as observed in some tumor cells [44]. …”

Plasma Membrane Ca2+-ATPase Isoforms Composition Regulates Cellular pH Homeostasis in Differentiating PC12 Cells in a Manner Dependent on Cytosolic Ca2+ Elevations

“…Alternatively, elevation in PMF could result from the inhibition of pathways that dissipate H + gradient. It has been reported that mitochondrial Ca 2+ uptake may inhibit ATP synthase [50] consequently increasing PMF and reducing ATP level. However, our observations with FCCP and oligomycin as well higher ATP content detected in _2 line (yet unpublished) rather exclude ATP synthase inhibition as a mechanism of PMF increase.…”

Calcium and Mitochondrial Reactive Oxygen Species Generation: How to Read the Facts

“…This ‘after-hyperpolarization’ parallels a significant increase in the ROS release from mitochondria [143]. The mechanism of the relative hyperpolarization following depolarization by moderate Ca 2+ load is yet to be clarified but could be related to inhibition of the adenylate translocase [148] or F 0 F 1 -ATPase by Ca 2+ [149,150]. Nonetheless, the stimulated ROS generation under this condition is most likely due to a shift of ΔΨ towards higher values, into the range where ROS generation is sensitive to changes in ΔΨ.…”