Sphingosine 1-phosphate (S1P), a potent lipid mediator, is a ligand for a family of five G
protein-coupled receptors (S1P 1–5) that have been shown to regulate a variety of biological
responses important for cancer progression. The cellular level of S1P is low and tightly
regulated in a spatio-temporal manner through its synthesis catalyzed by two sphingosine
kinases, denoted SphK1 and SphK2. Many stimuli activate and translocate SphK1 to the
plasma membrane by mechanisms that are dependent on its phosphorylation. Much less is …