Mitochondria, AIF and caspases — rivaling for cell death execution

In both the nematode Caenorhabditis elegans and mammals, two proteins released from the mitochondrion — apoptosis inducing factor (AIF) and endonuclease G — cooperate in executing programmed cell death. Although both factors can kill cells in a caspase-independent fashion, new studies indicate that their translocation from mitochondria depends, in part, on caspase activation. Together, these data raise new questions about the functional hierarchy between caspases, AIF and mitochondrial membrane permeabilization.