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

Abstract

We report reversible Ca²⁺-induced Ca²⁺ release from mitochondria, which takes the form of Ca²⁺ spikes. Mitochondrial Ca²⁺ spiking is an all-or-none process with a threshold dependence on both the frequency and the amplitude of the Ca²⁺ 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 Ca²⁺ responses in permeabilized cells. Evidence that mitochondrial Ca²⁺-induced Ca²⁺ release contributes to inositol-triphosphate-mediated Ca²⁺ responses in intact cells is also reported.