Characterization of the human and mouse sphingosine 1-phosphate receptor, S1P₅ (Edg-8): Structure - Activity relationship of sphingosine 1-phosphate receptors

Five G protein-coupled receptors (S1P₁/Edg-1, S1P₃/Edg-3, S1P₂/Edg-5, S1P₄/Edg-6, and S1P₅/Edg-8) for the intercellular lipid mediator sphingosine 1-phosphate have been cloned and characterized. We found human and mouse sequences closely related to rat S1P₅ (97% identical amino acids) and report now the characterization of the human and mouse S1P₅ gene products as encoding sphingosine 1-phosphate receptors. When HEK293T cells were cotransfected with S1P₅ and G protein DNAs, prepared membranes showed sphingosine 1-phosphate concentration-dependent increases in [γ-³⁵S]GTP binding (EC₅₀ = 12.7 nM). The lipid mediator inhibited forskolin-driven rises in cAMP by greater than 80% after introduction of the mouse or human S1P₅ DNAs into rat hepatoma RH7777 cells (IC₅₀ = 0.22 nM). This response is blocked fully by prior treatment of cultures with pertussis toxin, thus implicating signaling through G_i/oα proteins. Northern blot analysis showed high expression of human S1P₅ mRNA in spleen, corpus collosum, peripheral blood leukocytes, placenta, lung, aorta, and fetal tissues. Mouse S1P₅ mRNA is also expressed in spleen and brain. Finally, we found that one enantiomer of a sphingosine 1-phosphate analogue wherein the 3-hydroxyl and 4,5-olefin are replaced by an amide functionality shows some selectivity as an agonist S1P₁ and S1P₃ vs S1P₂ and S1P₅.