Mitochondrial calcium spiking: A transduction mechanism based on calcium‐induced permeability transition involved in cell calcium signalling

Abstract We report reversible Ca 2+ -induced Ca 2+ release from mitochondria, which takes the form of Ca 2+ spikes. Mitochondrial Ca 2+ spiking is an all-or-none process with a threshold dependence on both the frequency and the amplitude of the Ca 2+ pulses used as stimuli. This spiking relies on the transient operation of the mitochondrial permeability transition pore, and is initiated — in a threshold-dependent manner — with inositol-triphosphate-mediated Ca 2+ responses in permeabilized cells. Evidence that mitochondrial Ca 2+ -induced Ca 2+ release contributes to inositol-triphosphate-mediated Ca 2+ responses in intact cells is also reported.