Sphingosine-1-phosphate (S1P) is an agonist for S1P1-5 receptors and a ligand for GPR3, GPR6, and GPR12. As an intracellular second messenger, it mobilizes Ca2+ and acts as an extracellular ligand for G-protein coupled receptors. This important lipid mediator is generated from sphingosine or other membrane phospholipids.

Sphingosine-1-phosphate (S1P) (1 μM) induces significant Ca2+ release in HEK293 cells under serum starvation conditions (1% FCS).[1]
In functional Ca2+ assays, Suramin alone had no effect on intracellular Ca2+ release via gpr3, gpr6, or gpr12. In contrast, S1P (1 μM) induces Ca2+ release from gpr3, gpr6, and gpr12 in transfected HEK293 cells in the presence of varying concentrations of suramin.[2]
In a functional Ca2+ assay, S1P (3-3000 nM) exhibits nanomolar EC50 values in the presence of Suramin (300 μM) for gpr3 (EC50=29 nM), gpr6 (EC50=15 nM) and gpr12 (EC50=24 nM ), rat gpr3 (EC50=68 nM), respectively act on HEK293 cells.[2]
S1P increases the expression of S1P1 and Gqi5, and when used at a concentration of 200 nM, it allows Gi proteins to stimulate phospholipase C, as well as TAg-Jurkat cells expressing S1P2 and S1P3 receptors (EC 50s=8 and 11 nM).[3]