Wortmannin enhances activation of CPP32 (Caspase-3) induced by TNF or anti-Fas.

CPP32/apopain (Caspase-3), a protease of the Ced-3/ICE family, is a central mediator in the apoptosis induced by TNF or anti-Fas. In this study we demonstrate that wortmannin, an inhibitor of PI-3K, enhances the activation of CPP32 (Caspase-3) and DNA fragmentation in TNF-treated U937 cells and anti-Fas-treated Jurkat cells. Caspase-3-like activity, Ac-DEVD-MCA cleavage activity, is enhanced by wortmannin in the range of the concentration (1 - 100 nM) specifically inhibiting PI-3K. LY294002, another PI-3K inhibitor, also enhances Caspase-3-like activity, but inhibitors for myosin light chain kinase and calmodulin dependent kinase do not have any effect on the Caspase-3-like activity. Wortmannin (1 - 100 nM) enhances the processing of Caspase-3 (32K) into active form (17K) in TNF- or anti-Fas-treated cells, but not in untreated cells. These observations suggest that inhibition of PI-3K induces the activation of processing enzyme of Caspase-3 or increases the susceptibility of Caspase-3 to the processing enzyme. PI-3K seems to protect the cells from apoptosis by suppressing the activation of Caspase-3.