Structural basis for constitutive activity and agonist‐induced activation of the enteroendocrine fat sensor GPR 119

• Published in: British journal of pharmacology Vol. 171; no. 24; pp. 5774 - 5789
• Main Authors: Engelstoft, M S, Norn, C, Hauge, M, Holliday, N D, Elster, L, Lehmann, J, Jones, R M, Frimurer, T M, Schwartz, T W
• Format: Journal Article
• Language: English
• Published: 01.12.2014
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1111/bph.12877

Background and Purpose GPR 119 is a G αs‐coupled 7 TM receptor activated by endogenous lipids such as oleoylethanolamide ( OEA ) and by the dietary triglyceride metabolite 2‐monoacylglycerol. GPR 119 stimulates enteroendocrine hormone and insulin secretion. But despite massive drug discovery efforts in the field, very little is known about the basic molecular pharmacology of GPR 119. Experimental Approach GPR 119 receptor signalling was studied in transfected cells. Mutational mapping (30 mutations in 23 positions) was performed on residues required for ligand‐independent and agonist‐induced GPR 119 activation ( AR 231453 and OEA ). Novel Rosetta‐based receptor modelling was applied, using a composite template approach with segments from different X ‐ray structures and fully flexible ligand docking. Key Results The increased signalling induced by increasing the cell surface expression of GPR119 in the absence of agonist and the inhibitory effect of two synthetic inverse agonists demonstrated that GRP119 signals with a high degree of constitutive activity through the Gαs pathway. The mutational maps for AR 231453 and OEA were very similar and, surprisingly, also similar to the mutational map for residues affecting the constitutive signalling – albeit with key differences. Surprisingly, almost all residues in extracellular loop‐2b were important for the constitutive activity. The molecular modelling and docking demonstrated that AR 231453 binds in a ‘vertical’ pocket in between mutational hits reaching from the centre of the receptor out to extracellular loop‐2b. Conclusions and Implications The high constitutive activity of GPR 119 should be taken into account in future drug discovery efforts, which can now be guided by the detailed knowledge of the physiochemical properties of the extended ligand‐binding pocket.