Functional Selectivity of Natural and Synthetic Prostaglandin EP4 Receptor Ligands

• Published in: The Journal of pharmacology and experimental therapeutics 2009-10, Vol.331 (1), p.297-307
• Main Authors: Leduc, Martin, Breton, Billy, Galés, Céline, Le Gouill, Christian, Bouvier, Michel, Chemtob, Sylvain, Heveker, Nikolaus
• Format: Article
• Language: English
• Subjects: Animals; Arrestins - metabolism; Arrestins - physiology; beta-Arrestin 2; beta-Arrestins; Cell Line; Dinoprostone - metabolism; Dinoprostone - physiology; GTP-Binding Protein alpha Subunits, Gi-Go - metabolism; GTP-Binding Protein alpha Subunits, Gi-Go - physiology; GTP-Binding Protein alpha Subunits, Gs - metabolism; GTP-Binding Protein alpha Subunits, Gs - physiology; Humans; Insecta; Ligands; Protein Binding - drug effects; Protein Binding - physiology; Receptors, Prostaglandin E - metabolism; Receptors, Prostaglandin E - physiology; Receptors, Prostaglandin E, EP4 Subtype; Signal Transduction - drug effects; Signal Transduction - physiology
• ISSN: 0022-3565; 1521-0103
• DOI: 10.1124/jpet.109.156398

Classically, the prostaglandin E 2 (PGE 2 ) receptor EP 4 has been classified as coupling to the Gα s subunit, leading to intracellular cAMP increases. However, EP 4 signaling has been revealed to be more complex and also involves coupling to pertussis toxin-sensitive Gα i proteins and β-arrestin-mediated effects. There are now many examples of selective activation of independent pathways by G protein-coupled receptor (GPCR) ligands, a concept referred to as functional selectivity. Because most EP 4 ligands had thus far only been functionally characterized by their ability to stimulate cAMP production, we systematically determined the potencies and efficacies of a panel of EP 4 ligands for activation of Gα s , Gα i , and β-arrestin relative to the endogenous ligand PGE 2 . For this purpose, we adapted three bioluminescence resonance energy transfer (BRET) assays to evaluate the respective pathways in living cells. Our results suggest considerable functional selectivity among the tested, structurally related agonists. PGE 2 was the most selective in activating Gα s , whereas PGF 2α and PGE 1 alcohol were the most biased for activating Gα i1 and β-arrestin, respectively. We observed reversal in order of potencies between β-arrestin 2 and Gα i1 functional assays comparing PGE 1 alcohol and either PGF 2α , PGD 2 , or 7-[(1 R ,2 R )-2-[( E ,3 R )-3-hydroxy-4-(phenoxy)but-1-enyl]-5-oxocyclopentyl]heptanoic acid (M&B28767). Most ligands were full agonists for the three pathways tested. Our results have implications for the use of PGE 2 analogs in experimental and possibly clinical settings, because their activity spectra on EP 4 differ from that of the native agonist. The BRET-based methodology used for this first systematic assessment of a set of EP 4 agonists should be applicable for the study of other GPCRs.