title: Structural basis for constitutive activity and agonist-induced activation of the enteroendocrine fat sensor GPR119.
abstract: OBJECTIVE
  GPR119 is a Gαs-coupled 7TM receptor activated by endogenous lipids such as oleoylethanolamide (OEA) and by the dietary triglyceride metabolite 2-monoacylglycerol. GPR119 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 GPR119.
  
  
  METHODS
  GPR119 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 GPR119 activation (AR231453 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.
  
  
  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 AR231453 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 AR231453 binds in a 'vertical' pocket in between mutational hits reaching from the centre of the receptor out to extracellular loop-2b.
  
  
  CONCLUSIONS
  The high constitutive activity of GPR119 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.
authors.affiliation: Novo Nordisk Foundation Center for Basic Metabolic Research, Section for Metabolic Receptology and Enteroendocrinology, University of Copenhagen, Copenhagen, Denmark; Laboratory for Molecular Pharmacology, Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: M S
authors.initials: MS
authors.lastname: Engelstoft
authors.forename: C
authors.initials: C
authors.lastname: Norn
authors.forename: M
authors.initials: M
authors.lastname: Hauge
authors.forename: N D
authors.initials: ND
authors.lastname: Holliday
authors.forename: L
authors.initials: L
authors.lastname: Elster
authors.forename: J
authors.initials: J
authors.lastname: Lehmann
authors.forename: R M
authors.initials: RM
authors.lastname: Jones
authors.forename: T M
authors.initials: TM
authors.lastname: Frimurer
authors.forename: T W
authors.initials: TW
authors.lastname: Schwartz
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D063388:Endocannabinoids; D019858:Enteroendocrine Cells / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D062105:Molecular Docking Simulation; D009829:Oleic Acids / Q000494:pharmacology*; D010069:Oxadiazoles / Q000494:pharmacology*; D017434:Protein Structure, Tertiary; D011743:Pyrimidines / Q000494:pharmacology*; D043562:Receptors, G-Protein-Coupled / Q000819:agonists* / Q000378:metabolism; D014162:Transfection
chemical_list: C521085:AR 231453; D063388:Endocannabinoids; C519854:GPR119 protein, human; D007328:Insulin; D009829:Oleic Acids; D010069:Oxadiazoles; D011743:Pyrimidines; D043562:Receptors, G-Protein-Coupled; C488250:oleoylethanolamide