title: Mapping the binding site of six nonpeptide antagonists to the human V2-renal vasopressin receptor.
abstract: Whereas arginine vasopressin binds to its receptor subtypes V(1)R and V(2)R with equal affinity of approximately 2 nM, nonpeptide antagonists interact differently with vasopressin receptor subtypes. The V(2)R antagonist binding site was mapped by site-directed mutagenesis at six selected amino acid positions, K100D, A110W, M120V, L175Y, R202S, and F307I, predicted to be involved in antagonist binding differences between V(2) R and V(1)R. These mutations did not alter the affinity for arginine vasopressin. However, the affinity for six nonpeptide receptor antagonists SR121463B [1-[4-(N-tert-butylcarbamoyl)-2-methoxybenzenesulfonyl]-5-ethoxy-3-spiro-[4[(2 morpholinoethoxy)cy-clohexane]indoline-2-one, phosphate monohydrate cis-isomer], SR49059 [(2S)1-[(2R3S)-(5-chloro-3-(2 chlorophenyl)-1-(3,4-dimethoxybenzene-sulfonyl)-3-hydroxy-2,3-dihydro-1H-indole-2-carbonyl]-pyrrolidine-2-carboxamide], SSR149415 [(2S,4R)-1-[5-chloro-1-[(2,4-dimethoxyphenyl)sulfonyl]-3-(2-methoxyphenyl)-2-oxo-2,3-dihydro-1H-indol-3-yl]-4-hydroxy-N,N-dimethyl-2pyrrolidine carboxamide, isomer(-)], OPC21268 [1-[1-[4-(3-acetylaminopropoxy)benzoyl]-4-piperidyl]-3,4-dihydro-2(1H)-quinolinone], OPC41061 [(+/-)-4'-[(7-chloro-2,3,4,5-tetrahydro-5-hydroxy-1H-1-benzazepin-1-yl)carbonyl]-o-tolu-m-toluidide], and OPC31260, [(+/-)-5-dimethylamino-1-[4-(2-methylbenzoylamino)benzoyl]-1,2, 3,4,5-tetrahydro-1H-benzazepine monohydrochloride], was altered to varying degrees, resulting in differences up to 6000-fold. Replacement of the small alanine for the bulky tryptophan in position 110 resulted in a reduced affinity for all six antagonists. In contrast, replacement of the large methionine for the smaller valine in position 120 caused a dramatic increase in affinity, up to a K(i) of 7 fM for OPC31260. Molecular modeling revealed that the binding sites for arginine vasopressin and the nonpeptide antagonists are partially overlapping. Whereas arginine vasopressin binds on the extracellular surface of V(2) R, the nonpeptide antagonists penetrate deeper into the transmembrane region of the receptor, in particular OPC21268. The mutagenesis data point to significant differences in the shape of the V(1)R and V(2)R antagonist binding pockets. The most important factor determining the specificity of nonpeptide antagonists seems to be the shape of the binding pocket on the receptor.
authors.affiliation: Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106-4935, USA.
authors.forename: Rosemarie
authors.initials: R
authors.lastname: Macion-Dazard
authors.forename: Nicholas
authors.initials: N
authors.lastname: Callahan
authors.forename: Zhen
authors.initials: Z
authors.lastname: Xu
authors.forename: Nan
authors.initials: N
authors.lastname: Wu
authors.forename: Marc
authors.initials: M
authors.lastname: Thibonnier
authors.forename: Menachem
authors.initials: M
authors.lastname: Shoham
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D065092:Antidiuretic Hormone Receptor Antagonists; D001665:Binding Sites; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D016297:Mutagenesis, Site-Directed; D011863:Radioimmunoassay; D017483:Receptors, Vasopressin / Q000737:chemistry*; D013329:Structure-Activity Relationship
chemical_list: D065092:Antidiuretic Hormone Receptor Antagonists; D008024:Ligands; D017483:Receptors, Vasopressin