MITOCHONDRIAL CALCIUM SPIKING - A TRANSDUCTION MECHANISM-BASED ON CALCIUM-INDUCED PERMEABILITY TRANSITION INVOLVED IN CELL CALCIUM SIGNALING

We report reversible Ca2+-induced Ca2+ release from mitochondria, whic h 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 transitio n pore, and is initiated - in a threshold-dependent manner - with inos itol-triphosphate-mediated Ca2+ responses in permeabilized cells. Evid ence that mitochondrial Ca2+-induced Ca2+ release contributes to inosi tol-triphosphate-mediated Ca2+ responses in intact cells is also repor ted.