Nrg-1 belongs to the endothelial differentiation gene family of G protein-coupled sphingosine-1-phosphate receptors.
The previously cloned rat nerve growth factor-regulated G protein-coupled receptor NRG-1 (Glickman, M., Malek, R. L., Kwitek-Black, A. E., Jacob, H. J., and Lee N. H. (1999) Mol. Cell. Neurosci. 14, 141-52), 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 NH2-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 NH2-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 [35S] guanosine 5'-3-O-(thio)triphosphate binding assay demonstrates that EDG-8 activated G(i/o) and G12 but not Gs 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.
Malek
R L
RL
Department of Molecular and Cellular Biology, Institute for Genomic Research, Rockville, Maryland 20850, USA.
Toman
R E
RE
Edsall
L C
LC
Wong
S
S
Chiu
J
J
Letterle
C A
CA
Van Brocklyn
J R
JR
Milstien
S
S
Spiegel
S
S
Lee
N H
NH
D002455:Cell Division / Q000502:physiology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D017874:Immediate-Early Proteins / Q000145:classification* / Q000235:genetics; D008246:Lysophospholipids; D005810:Multigene Family; D020890:Neuregulin-1 / Q000145:classification* / Q000235:genetics; D037342:Pertussis Toxin; D011494:Protein Kinases / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000145:classification* / Q000235:genetics; D043562:Receptors, G-Protein-Coupled; D049312:Receptors, Lysophospholipid; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism*; D014638:Vanadates / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D017874:Immediate-Early Proteins; D008246:Lysophospholipids; D020890:Neuregulin-1; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D049312:Receptors, Lysophospholipid; D011994:Recombinant Proteins; D010566:Virulence Factors, Bordetella; C060506:sphingosine 1-phosphate; D014638:Vanadates; D037342:Pertussis Toxin; D011494:Protein Kinases; D019204:GTP-Binding Proteins; D013110:Sphingosine