Sphingosine-1-phosphate is an endogenous second messenger that involved in cell proliferation and survival and is a ligand for S1PR1 [1] [2].

Sphingosine-1-phosphate receptor 1 (S1PR1), also known as endothelial differentiation gene 1 (EDG1), is a G-protein-coupled receptor for sphingosine-1-phosphate (S1P) and is involved in regulating endothelial cell cytoskeletal structure, capillary-like network formation, migration and vascular maturation.

Sphingosine-1-phosphate is an endogenous second messenger and a ligand for S1PR1. In endothelial cells, S1P (1-20 μM) induced EDG-l-dependent morphogenesis. In HEK293EDG-1 cells, S1P bound to S1PR1 with Kd value of 8.1 nM in a time-dependent way. In cells transfected with EDG-l, S1P activated ERK-1 and ERK-2 via EDG-1. S1P existed in platelets and released through platelet activation [2]. In human embryonic kidney (HEK) cells, S1P significantly increased [Ca2+]i with EC50 value of 2 nM in a pertussis toxin-sensitive way and inhibited cAMP accumulation induced by forskolin. Also, S1P increased the binding of guanosine 5’-3-O-(thio)triphosphate to cell membranes. In guinea pig atrial myocytes, S1P at the extracellular face activated Gi protein-regulated inwardly rectifying potassium channels [3]. S1P inhibited programmed cell death mediated by ceramide [4].

References:
[1].  Olivera A, Spiegel S. Sphingosine-1-phosphate as second messenger in cell proliferation induced by PDGF and FCS mitogens. Nature, 1993, 365(6446): 557-560.
[2].  Lee MJ, Van Brocklyn JR, Thangada S, et al. Sphingosine-1-phosphate as a ligand for the G protein-coupled receptor EDG-1. Science, 1998, 279(5356): 1552-1555.
[3].  van Koppen C, Meyer zu Heringdorf M, Laser KT, et al. Activation of a high affinity Gi protein-coupled plasma membrane receptor by sphingosine-1-phosphate. J Biol Chem, 1996, 271(4): 2082-2087.
[4].  Cuvillier O, Pirianov G, Kleuser B, et al. Suppression of ceramide-mediated programmed cell death by sphingosine-1-phosphate. Nature, 1996, 381(6585): 800-803.