The protein encoded by this gene catalyzes the phosphorylation of sphingosine to form sphingosine-1-phosphate (S1P)，a lipid mediator with both intra- and extracellular functions. Intracellularly，S1P regulates proliferation and survival，and extracellularly，it is a ligand for cell surface G protein-coupled receptors. This protein，and its product S1P，play a key role in TNF-alpha signaling and the NF-kappa-B activation pathway important in inflammatory，antiapoptotic，and immune processes. Phosphorylation of this protein alters its catalytic activity and promotes its translocation to the plasma membrane. Alternative splicing results in multiple transcript variants encoding different isoforms.