Aurora kinase B-dependent phosphorylation regulates caspase-2 activity and function

Mitotic catastrophe (MC) is an important mechanism to remove cells that become polyploid or aneuploid, as an oncosuppressive mechanism. Previous studies have demonstrated that the activation and catalytic function of caspase-2 is a key step in MC, to trigger apoptosis and/or cell cycle arrest of such defective cells. However, the molecular mechanisms that regulate caspase-2 activation and its function are unclear. Here we show that Aurora kinase B (AURKB), a key mitotic kinase, phosphorylates caspase-2 at a highly conserved residue S384 and inhibits its catalytic activity and function. We identified six new phosphorylation sites in caspase-2 and further demonstrated that phosphorylation at S384 blocks caspase-2 catalytic activity and apoptosis function in response to mitotic insults, without affecting caspase-2 dimerisation. Moreover, molecular modelling suggests that phosphorylation at S384 may affect substrate binding by caspase-2. We propose that caspase-2 S384 phosphorylation by AURKB is a key mechanism that controls caspase-2 activation during mitosis.