The unpredictable caspase-2: what can it do?

Caspase-2, the most conserved member of the caspase family, has long been recognized as an important protein in the regulation of apoptosis. However, due to a lack of phenotype in caspase-2 knock-out mice, its precise role has been questioned. Recently, several publications have described new mechanisms regulating caspase-2 activation, including its role within an activating complex named the PIDDosome, linking caspase-2 function to p53. Consistent with this, evidence is accumulating for potential roles of caspase-2 in non-apoptotic processes, including cell cycle regulation and DNA repair. In addition, a tumor-suppressor function has been suggested for caspase-2. Here we discuss how different PIDDosome complexes could be involved in mechanisms regulating the switch between the various functions of caspase-2.