Ceramide in apoptosis--does it really matter?

During recent years, ceramide has received a lot of attention as a possible mediator of the cellular responses to a variety of apoptotic stimuli. In a manner analogous to generation of its sibling diacylglycerol, ceramide is generated by a phospholipase-C-type reaction from its lipid precursor sphingomyelin. Two observations led to the proposal that ceramide plays a role in apoptosis: (1) treatment of cells with tumor necrosis factor or other inducers of apoptosis leads to activation of sphingomyelinases and to an increase in cellular ceramide levels; (2) ectopic generation or administration of ceramide can mimic apoptotic cell death. Recently, several observations have challenged the notion that ceramide is an important cell-death mediator and have prompted a re-evaluation of previously published results.