Bcl-2-regulated calcium signals as common mediators of both apoptosis and autophagy.

The calcium ion, a major intracellular second messenger, is a known mediator of apoptosis and is regulated by the antiapoptotic protein Bcl-2. A paper by Høyer-Hasen et al. (2007) in the current issue of Molecular Cell indicates that calcium also mediates the induction of macroautophagy in a Bcl-2 regulated fashion and identifies a signaling pathway through which calcium exerts its action. These intriguing findings provoke speculation as to how a cell decides to undergo either apoptosis or macroautophagy in response to calcium signals.