ABSTRACT
Sphingolipids play important roles in apoptosis, differentiation, senescence, proliferation, and inflammation. The sphingomyelin (SM) cycle, with the key components of SM, sphingomyelinase (SMase) and ceramide, has received substantial attention to date because of its role in cell signaling. The first step in sphingolipid synthesis is the condensation of palmitoyl-CoA and serine. Eventually dihydroceramide is converted to ceramide, and then SM synthase transfers a choline–phosphate from phosphatidylcholine to ceramide to produce SM. Thus, an increase in SMase activity may represent transcriptional increase in the amount of enzyme, a change in allosteric regulation, or a post-translational modification. However, this alteration in SMase activity is neither necessary nor sufficient to document the role of a particular SMase.
