Phosphorylation by Aurora B kinase regulates caspase-2 activity and function

Area of Science:

• Cell Biology
• Molecular Biology
• Cancer Research

Background:

• Mitotic catastrophe (MC) eliminates cells with abnormal chromosome numbers during mitosis.
• Caspase-2 activation is crucial for MC, triggering apoptosis or cell cycle arrest.
• The precise regulation of caspase-2 activation and function in MC remains incompletely understood.

Purpose of the Study:

• To elucidate the molecular mechanisms governing caspase-2 activation and function during mitosis.
• To identify regulatory post-translational modifications of caspase-2.
• To investigate the role of mitotic kinases in controlling caspase-2 activity.

Main Methods:

• Phosphoproteomic analysis to identify caspase-2 phosphorylation sites.
• Site-directed mutagenesis to assess the functional impact of phosphorylation.
• Biochemical assays to measure caspase-2 catalytic activity and apoptosis induction.
• Molecular modeling to predict effects on substrate binding.

Main Results:

• Six novel phosphorylation sites on caspase-2 were identified.
• Aurora B kinase (AURKB) was found to phosphorylate caspase-2 at serine 384 (S384).
• Phosphorylation at S384 inhibits caspase-2's catalytic activity and apoptosis-inducing function during mitotic stress, without affecting dimerization.
• Molecular modeling suggests S384 phosphorylation may impede substrate binding.

Conclusions:

• Caspase-2 S384 phosphorylation by AURKB is a key regulatory mechanism controlling caspase-2 activation.
• This phosphorylation event acts as an inhibitory switch, preventing inappropriate caspase-2 activity during mitosis.
• Understanding this regulation provides insights into the oncosuppressive role of mitotic catastrophe.