Phosphatidylserine induces apoptosis in adherent cells

Phosphatidylserine (PS) is exposed on the outer leaflet of the plasma membr ane in apoptotic cell death. However, the roles of PS in apoptotic signalin g are still unclear. In this study, we found that exogenous PS, but not oth er phospholipids, induced cell death in adherent cells, but not in suspensi on culture. The cell death exhibited typical features of apoptosis such as cell shrinkage, nuclear fragmentation and abnormal chromatin condensation. When PS was added to CHO-K1 cells in monolayer culture, they began to show changes in cell shape and actin cytoskeleton and protein kinase C (PKC) act ivity, followed by cell detachment, caspase activation, cleavage of focal a dhesion kinase (FAK) and finally loss of viability. These results suggested that PS causes apoptosis through actin disorganization, cell detachment an d cleavage of FAK.