Sphingolipids are a kind of amphiprotic lipids containing sphingol backbones, which attach to a long chain of fatty acids at one end and polar alcohol at the other. Sphingolipids, including sphingomyelins, cerebrosides, and gangliosides, are commonly found in plant and animal membranes and are particularly abundant in tissues of the central nervous system. Cerebrosides and gangliosides can also be called glycosphingolipids due to their glycosyls.
In mammals, the sphingolipid signaling pathway refers to the process by which ceramide (Cer) and sphingosine-1-phosphate (S1P), the hydrolytic products of sphingolipid, functions in a variety of cellular signaling pathways.
Sphingolipids and their metabolites are important active molecules involved in many important signal transduction processes such as cell proliferation, differentiation, senescence, and apoptosis.
In mammals, membrane sphingomyelin is hydrolyzed into ceramide and S1P by sphingomyelinase (SMase). Ceramide subsequently generates sphingosine (Sph) by ceramidase. Sphingosine produces S1P through phosphorylation by sphingosine kinases 1 (SphK1) and sphingosine kinases 2 (SphK2). Although both ceramide and S1P regulate cellular responses to stress, they function oppositely. S1P acts as a survival factor and a ligand for a family of G protein-coupled receptors, whereas ceramide activates intrinsic and extrinsic apoptotic pathways through receptor-independent mechanisms.