Sphingosine-1-phosphate is a ligand for the G protein-coupled receptor EDG-6

EDG-6 is a recently cloned member of the endothelial differentiation gene ( EDG) G protein-coupled receptor family that is expressed in lymphoid and he matopoietic tissue and in the lung. Homology of EDG-6 to the known sphingos ine-1-phosphate (SPP) receptors EDG-1, EDG-8, and EDG-5 and lysophosphatidi c acid (LPA) receptors EDG-2 and EDG-4 suggested that its ligand may be a l ysophospholipid or lysosphingolipid. We examined the binding of [P-32]SPP t o HEK293 cells, transiently transfected with cDNA encoding EDG-6, Binding o f [P-32]SPP was saturable, demonstrating high affinity (K-D = 63 nmol/L). B inding was also specific for SPP, as only unlabeled SPP and sphinganine-1-p hosphate, which lacks the trans double bond at the 4 position, potently dis placed radiolabeled SPP, LPA did not compete for binding of SPP at any conc entration tested, whereas sphingosylphosphorylcholine competed for binding to EDG-6, but only at very high concentrations. In addition, SPP activated extracellular signal-regulated kinase (Erk) in EDG-6 transfected cells in a pertussis toxin-sensitive manner. These results Indicate that EDG-6 is a h igh affinity receptor for SPP, which couples to a G(i/o) protein, resulting in the activation of growth-related signaling pathways. (Blood, 2000;95:26 24-2629) 2000 by The American Society of Hematology.