Mitochondrial signaling in apoptosis: mitochondrial daggers to the breaking heart.

Mitochondria respond to signals from the cytoplasmic environment, including energy needs, substrate and oxygen availability, ion fluxes, as well as kinase and proteolytic signals. They integrate these complex, often conflicting signals with a coordinated response, whether for growth, hibernation, or apoptosis. In this review we consider the panoply of signals that impact the mitochondria, and focus particularly on the apoptotic pathways in which the mitochondria stand at the crossroads.