title: Partial agonism, neutral antagonism, and inverse agonism at the human wild-type and constitutively active cholecystokinin-2 receptors.
abstract: Cholecystokinin receptor-2 (CCK2R) is a G protein receptor that regulates a number of physiological functions. Activation of CCK2R and/or expression of a constitutively active CCK2R variant may contribute to human diseases, including digestive cancers. Search for antagonists of the CCK2R has been an important challenge during the last few years, leading to discovery of a set of chemically distinct compounds. However, several early-discovered antagonists turned out to be partial agonists. In this context, we carried out pharmacological characterization of six CCK2R antagonists using COS-7 cells expressing the human CCK2R or a CCK2R mutant having a robust constitutive activity on inositol phosphates production, and we investigated the molecular mechanisms which, at a CCK2R binding site, account for these features. Results indicated that three compounds, 3R(+)-N-(2,3-dihydro-1-methyl-2-oxo-5-phenyl-1H-1,4-benzodiazepin-3-yl)-N'-(3-methylphenyl)urea (L365,260), 4-{[2-[[3-(lH-indol-3-yl)-2-methyl-1-oxo-2-[[[1.7.7-trimethyl-bicyclo[2.2.1]hept-2-yl)-oxy]carbonyl]amino]propyl]amino]-1-phenylethyl]amino-4-oxo-[lS-la.2[S*(S*)]4a]}-butanoate N-methyl-D-glucamine (PD135,158), and (R)-1-naphthalenepropanoic acid, b-[2-[[2-(8-azaspiro-[4.5]dec-8-ylcarbonyl)-4,6-dimethylphenyl]amino]-2-oxoethyl] (CR2945), were partial agonists; one molecule, 1-[(R)-2,3-dihydro-1-(2,3-dihydro-1-(2-methylphenacyl)-2-oxo-5-phenyl-1H-1,4-benzodiazepin-3-yl]-3-(3-methylphenyl)urea (YM022), was a neutral antagonist; and two compounds, N-(+)-[1-(adamant-1-ylmethyl)-2,4-dioxo-5-phenyl2,3,4,5-tetrahydro-1H-1,5-benzodiazepin-3-yl]-N'-phenylurea (GV150,013X) and ([(N-[methoxy-3 phenyl] N-[N-methyl N-phenyl carbamoylmethyl], carbomoyl-methyl)-3 ureido]-3-phenyl)2-propionic acid (RPR101,048), were inverse agonists. Furthermore, target- and pharmacophore-based docking of ligands followed by molecular dynamic simulation experiments resulted in consistent motion of aromatic residues belonging to a network presumably important for activation, thus providing the first structural explanations for the different pharmacological profiles of tested compounds. This study confirms that several referenced so-called antagonists are in fact partial agonists, and because of this undesired activity, we suggest that newly generated molecules should be preferred to efficiently block CCK2R-related physiological effects. Furthermore, data on the structural basis for the different pharmacological features of CCK2R ligands will serve to further clarify CCK2R mechanism of activation.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, Unit 531, Institut Fédératif de Recherche, Toulouse, France. fourmyd@toulouse.inserm.fr
authors.forename: Magali
authors.initials: M
authors.lastname: Foucaud
authors.forename: Irina G
authors.initials: IG
authors.lastname: Tikhonova
authors.forename: Ingrid
authors.initials: I
authors.lastname: Langer
authors.forename: Chantal
authors.initials: C
authors.lastname: Escrieut
authors.forename: Marlène
authors.initials: M
authors.lastname: Dufresne
authors.forename: Cathy
authors.initials: C
authors.lastname: Seva
authors.forename: Bernard
authors.initials: B
authors.lastname: Maigret
authors.forename: Daniel
authors.initials: D
authors.lastname: Fourmy
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D006801:Humans; D007295:Inositol Phosphates / Q000096:biosynthesis; D008024:Ligands; D009154:Mutation; D043887:Receptor, Cholecystokinin B / Q000819:agonists* / Q000037:antagonists & inhibitors* / Q000235:genetics
chemical_list: D007295:Inositol Phosphates; D008024:Ligands; D043887:Receptor, Cholecystokinin B