Mitochondrial regulation of intracellular Ca2+ signaling: more than just simple Ca2+ buffers. 
Mitochondrial Ca(2+) uptake shapes the profile of intracellular Ca(2+) signals, both spatially and temporally.  In addition, such uptake controls the gating of Ca(2+) release and store-operated Ca(2+) entry channels, partitions cells into subcellular Ca(2+) hotspots, and can result in the release of diffusible signals into the cytosol that subsequently regulate protein function.