Non-equivalence of Key Positively Charged Residues of the Free Fatty Acid 2 Receptor in the Recognition and Function of Agonist Versus Antagonist Ligands.
Bottom Line: Specifically, although agonists require interaction with both arginine residues to bind the receptor, antagonists require an interaction with only one of the two.Moreover, different chemical series of antagonist interact preferentially with different arginine residues.A homology model capable of rationalizing these observations was developed and provides a tool that will be invaluable for identifying improved FFA2 agonists and antagonists to further define function and therapeutic opportunities of this receptor.
Affiliation: From the Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom and.Show MeSH
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Mentions: GLPG0974 (Fig. 1) has recently been described as a selective FFA2 receptor antagonist that is able to block C2-mediated chemotaxis of human neutrophils (19). We synthesized this compound and demonstrated that it was able to antagonize, in a concentration-dependent manner, both C3 and Cmp 1-mediated activation of a form of hFFA2 that had been C-terminally tagged with enhanced yellow fluorescent protein (hFFA2-eYFP). This was the case whether employing a BRET-based β-arrestin-2 recruitment assay (Fig. 2A), a Gq/11-dependent [Ca2+]i mobilization (Fig. 2B), or a Gi/o-dependent [35S]GTPγS incorporation (Fig. 2C) assay. In each case, when employing 80% maximally effective concentrations of either C3 or Cmp 1, GLPG0974 displayed high and similar potency inhibition against each of the agonists (Table 1). GLPG0974 was highly selective for hFFA2, showing no inhibitory effect on C3-mediated activation of the closely related SCFA receptor hFFA3 (Fig. 2D). However, as found previously for CATPB, another FFA2 antagonist (10), GLPG0974 displayed marked species selectivity and was unable to block the effects of either C3 or Cmp 1 at mFFA2 (Fig. 2E).
Affiliation: From the Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom and.