Sphingosine-1-phosphate (S1P) displays sustained S1P1 receptor agonism and signaling through S1P lyase-dependent receptor recycling.
The sphingosine-1-phosphate (S1P) type 1 receptor (S1P1R) is a novel therapeutic target in lymphocyte-mediated autoimmune diseases. S1P1 receptor desensitization caused by synthetic S1P1 receptor agonists prevents T-lymphocyte egress from secondary lymphoid organs into the circulation. The selective S1P1 receptor agonist ponesimod, which is in development for the treatment of autoimmune diseases, efficiently reduces peripheral lymphocyte counts and displays efficacy in animal models of autoimmune disease. Using ponesimod and the natural ligand S1P, we investigated the molecular mechanisms leading to different signaling, desensitization and trafficking behavior of S1P1 receptors. In recombinant S1P1 receptor-expressing cells, ponesimod and S1P triggered Gαi protein-mediated signaling and β-arrestin recruitment with comparable potency and efficiency, but only ponesimod efficiently induced intracellular receptor accumulation. In human umbilical vein endothelial cells (HUVEC), ponesimod and S1P triggered translocation of the endogenous S1P1 receptor to the Golgi compartment. However, only ponesimod treatment caused efficient surface receptor depletion, receptor accumulation in the Golgi and degradation. Impedance measurements in HUVEC showed that ponesimod induced only short-lived Gαi protein-mediated signaling followed by resistance to further stimulation, whereas S1P induced sustained Gαi protein-mediated signaling without desensitization. Inhibition of S1P lyase activity in HUVEC rendered S1P an efficient S1P1 receptor internalizing compound and abrogated S1P-mediated sustained signaling. This suggests that S1P lyase - by facilitating S1P1 receptor recycling - is essential for S1P-mediated sustained signaling, and that synthetic agonists are functional antagonists because they are not S1P lyase substrates.
Actelion Pharmaceuticals Ltd, Gewerbestrasse 16, 4123 Allschwil, Switzerland. Electronic address: john.gatfield@actelion.com.
John
J
Gatfield
Actelion Pharmaceuticals Ltd, Gewerbestrasse 16, 4123 Allschwil, Switzerland.
Lucile
L
Monnier
Actelion Pharmaceuticals Ltd, Gewerbestrasse 16, 4123 Allschwil, Switzerland.
Rolf
R
Studer
Actelion Pharmaceuticals Ltd, Gewerbestrasse 16, 4123 Allschwil, Switzerland.
Martin H
MH
Bolli
Actelion Pharmaceuticals Ltd, Gewerbestrasse 16, 4123 Allschwil, Switzerland.
Beat
B
Steiner
Actelion Pharmaceuticals Ltd, Gewerbestrasse 16, 4123 Allschwil, Switzerland.
Oliver
O
Nayler
D019390:Arrestins / Q000378:metabolism; D001327:Autoimmune Diseases / Q000628:therapy; D045744:Cell Line, Tumor; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D006367:HeLa Cells; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D008246:Lysophospholipids / Q000494:pharmacology*; D008565:Membrane Proteins / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D021381:Protein Transport; D049349:Receptors, Lysosphingolipid / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D015398:Signal Transduction; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013601:T-Lymphocytes / Q000276:immunology; D013844:Thiazoles / Q000494:pharmacology*; D000071557:beta-Arrestins
D019390:Arrestins; D008246:Lysophospholipids; D008565:Membrane Proteins; D049349:Receptors, Lysosphingolipid; D013844:Thiazoles; D000071557:beta-Arrestins; C060506:sphingosine 1-phosphate; C550169:ponesimod; C401298:sphingosine-1-phosphate phosphatase; D010744:Phosphoric Monoester Hydrolases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D013110:Sphingosine
G protein coupled receptors; Receptor recycling; S1P lyase; S1P1 desensitization; Signal transduction; Sphingosine-1-phosphate