The role of calcium in the regulation of apoptosis.

The recognition that apoptosis is regulated by an evolutionarily conserved set of polypeptides from the nematode Caenorhabditis elegans to humans suggests that a conserved set of biochemical mechanism(s) may also be involved in the response. Early evidence suggested that the endogenous endonuclease implicated in apoptosis in most model systems is Ca(2+)-dependent, and subsequent work from a number of independent laboratories suggests that alterations in cytosolic Ca2+ homeostasis are one of the conserved biochemical pathways regulating the response. Molecular targets for Ca2+ are now being identified and include signal transduction intermediates, endonuclease(s) and proteases, and the enzymes involved in the maintenance of phospholipid asymmetry in the plasma membrane. Furthermore, interesting preliminary work suggests that BCL-2 suppresses apoptosis via a mechanism that is linked to intracellular Ca2+ compartmentalization, and it appears that Ca2+ alterations in some examples of apoptosis occur as the result of changes within the mitochondria. This review will summarize what is known about the role of Ca2+ in the regulation of apoptosis and discuss how Ca2+ might interact with some of the other biochemical signals implicated in cell death.