The role of de novo ceramide synthesis in chemotherapy-induced apoptosis.

The de novo pathway of sphingolipid synthesis has been implicated as an alternative to sphingomyelinase activation in generating an apoptotic response through ceramide. A chemotherapy agent was used to activate this pathway in a human T-cell line in order to investigate the role of de novo ceramide synthesis in apoptosis. In data obtained from intact cell radiolabeling studies, it was observed that the first and rate-limiting enzyme in de novo synthesis, serine palmitoyltransferase, is activated and controls the production of ceramide through this pathway. Furthermore, using agents that selectively inhibit ceramide production by this pathway, partial protection from cell death was observed that was independent of caspase activation. These results reveal that serine palmitoyltransferase, an enzyme that controls sphingolipid synthesis for housekeeping functions, is activated during apoptosis and serves to mediate events in this process.