We study how mammalian cells activate the programmed cell death pathway and die by apoptosis. We have focused our work on identifying unique mechanisms by which this pathway is regulated in postmitotic cells such as neurons, cardiomyocytes, and myotubes, as well as cancer, senescent, and stem cells. Excessive cell death is seen in many pathological conditions such as after stroke, neurodegeneration or cardiovascular diseases. In contrast, reduced cell death is a hallmark of cancers. Therefore, discovering the mechanism by which mammalian cells regulate cell death has significant therapeutic implications.