Cleavage of plasma membrane calcium pumps by caspases: a link between apoptosis and necrosis

Neuronal death, which follows ischemic injury or is triggered by excitotoxins, can occur by both apoptosis and necrosis. Caspases, which are not directly required for necrotic cell death, are central mediators of the apoptotic program. Here we demonstrate that caspases cleave and inactivate the plasma membrane Ca2+, pump (PMCA) in neurons and non-neuronal cells undergoing apoptosis. PMCA cleavage impairs intracellular Ca2+ handling, which results in Ca2+, overload. Expression of non-cleavable PMCA mutants prevents the disturbance in Ca2+ handling, slows down the kinetics of apoptosis, and markedly delays secondary cell lysis (necrosis). These findings suggest that caspase-mediated cleavage and inactivation of PMCAs can lead to necrosis, an event that is reduced by caspase inhibitors in brain ischemia.