text: S1P is present at high concentrations in plasma and secreted locally at elevated concentrations at sites of inflammation.  It is formed by the regulated phosphorylation of sphingosine.  It acts through five dedicated high-affinity G-protein coupled receptors, S1P1 - S1P5.  Targeted deletion of S1P1 results in lethality in mice and deletion of S1P2 results in seizures and deafness.  Additionally, a mere 3- to 5-fold elevation in serum S1P concentrations induces sudden cardiac death by an S1P3-receptor specific mechanism.