Nrg-1 Belongs to the Endothelial Differentiation Gene Family of G Protein-coupled Sphingosine-1-phosphate Receptors

Abstract

also known as EDG-8, binds sphingosine-1-phosphate (S1P) with high affinity and specificity. In this paper we examined the signal transduction pathways regulated by the binding of S1P to EDG-8. In Chinese hamster ovary cells heterologously expressing EDG-8, S1P inhibited forskolin-induced cAMP accumulation and activated c-Jun NH 2 -terminal kinase. Surprisingly, S1P inhibited serum-induced activation of extracellular regulated protein kinase 1 and 2 (ERK1/2). Treatment with pertussis toxin, which ADP-ribosylates and inactivates G i , blocked S1P-mediated inhibition of cAMP accumulation, but had no effect on c-Jun NH 2 -terminal kinase activation or inhibition of ERK1/2. The inhibitory effect of S1P on ERK1/2 activity was abolished by treatment with orthovanadate, suggesting the involvement of a tyrosine phosphatase. A subunit selective [35 S] guanosine 5-3-O-(thio)triphosphate binding assay demonstrates that EDG-8 activated G i/o and G 12 but not G s and G q/11 in response to S1P. In agreement, EDG-8 did not stimulate phosphoinositide turnover or cAMP accumulation. The ability of S1P to induce mitogenesis in cells expressing the EDG-1 subfamily of G protein-coupled receptors is well characterized. In contrast, S1P inhibited proliferation in Chinese hamster ovary cells expressing EDG-8 but not empty vector. The antiproliferative effect, like S1P-mediated ERK1/2 inhibition, was orthovanadate-sensitive and pertussis toxin-insensitive. Our results indicate that EDG-8, a member of the EDG-1 subfamily, couples to unique signaling pathways.The lysophospholipids sphingosine-1-phosphate (S1P) 1 and lysophosphatidic acid (LPA) are endogenous ligands of the EDG family of G protein-coupled receptors (GPCRs) (1-3). Presently, eight EDG receptors have been cloned and are divided into two or three homology clusters or subfamilies (4 -13). EDG-1, -3, -5, and -8 exhibit high sequence homology to one another and have high affinity for S1P (14 -17). EDG-2, -4, and -7 form a second cluster and are high affinity receptors for LPA (1,5,8,18). EDG-6 displays intermediate homology between the two clusters and binds S1P with moderate to high affinity (7, 19). S1P-activated EDG receptors are coupled to multiple effector pathways, including activation/inhibition of adenylyl cyclase, stimulation of phosphoinositide (PI) hydrolysis, mobilization of Ca 2ϩ (20 -26), induction of DNA synthesis (27-29), and stimulation of the MAP kinase family members ERK1/2, SAPK/JNK, and p38 (17, 20 -24). For example, activation of EDG-1, -3, or -5 by S1P leads to a pertussis toxin (PTX)-sensitive stimulation of ERK1/2 (17, 20 -22, 24), suggesting the involvement of G i/o proteins. In contrast, EDG-5 stimulates both stress-activated protein kinases, SAPK/JNK and p38, in a PTX-insensitive manner (23), indicating that EDG receptor coupling to MAP kinase family members involves PTX-sensitive and -insensitive

Roles of sphingosine-1-phosphate (S1P) receptors in malignant behavior of glioma cells. Differential effects of S1P2 on cell migration and invasiveness

“…S1P 5 overexpression decreased basal levels of phosphoERK and further decreased phosphoERK upon S1P stimulation (Fig. 3A), in agreement with previously published results [15]. Down regulation of S1P 1 , S1P 2 , or S1P 3 expression in U-373 MG cells partially decreased S1P stimulation of ERK phosphorylation (Fig.…”

Design and Synthesis of Selective and Potent Orally Active S1P5 Agonists

“…The mRNA for S1P5 is predominantly expressed in the white matter tracts of the brain, including the cerebellum, corpus callosum, and the spinal cord. [14][15][16][17][18][19] S1P5 receptors are preferentially expressed in oligodendrocytes at all stages of development: progenitors and mature lineages. [9,17,20] The distinct distribution pattern of S1P5 suggests it may play an important role in regulating myelination.…”

FTY720, a sphingosine 1-phosphate receptor modulator, inhibits CD1d-restricted NKT cells by suppressing cytokine production but not migration

“…30 S1P 1 signals exclusively through PTX-sensitive G i and G o proteins, whereas S1P 2 , S1P 3 , S1P 4 , and S1P 5 couple to the PTX-sensitive as well as PTX-insensitive G 12 , G 13 , or G q proteins. [31][32][33] Therefore, all effects of S1P 1 are PTX sensitive. Moreover, SEW2871 selectively binds and activates S1P 1 through a combination of hydrophobic and ion-dipole interaction.…”