The lysosphingolipid sphingosine 1-phosphate (S1P) regulates cell proliferation, apoptosis, motility, and neurite retraction. Its actions may be both intracellular as a second messenger and extracellular as a receptor ligand. S1P and the structurally related lysolipid mediator lysophosphatidic acid (LPA) signal cells through a set of G protein-coupled receptors known as EDG receptors. Some EDG receptors are S1P receptors; others are LPA receptors.
According to these guidelines, a receptor is to be named with the abbreviation of the natural agonist with the highest potency, followed by a subscripted arabic number. Thus they suggested that the designation EDG5 should be changed to S1P2.