Measurement of changes in apoptosis and cell cycle regulatory kinase Cdk2.

Many cell cycle regulatory proteins have been shown to be able to regulate cell death. Activation of Cdk2 has been shown to be necessary for the apoptosis of quiescent cells such as thymocytes, neurons, and endothelial cells. This activation is stimulus-specific because it occurs in glucocorticoid and DNA damage-induced but not in CD95-induced apoptosis in thymocytes. Apoptotic Cdk2 activation is controlled by apoptosis regulatory proteins like p53 and Bcl2 family members and correlates with degradation of its inhibitors p21Cip1 and p27Kip1 by activated caspases. Methods for measuring Cdk2 changes in activity in quiescent cells undergoing apoptosis are detailed in this chapter.