title: Molecular mechanism underlying inverse agonist of angiotensin II type 1 receptor.
abstract: To delineate the molecular mechanism underlying the inverse agonist activity of olmesartan, a potent angiotensin II type 1 (AT1) receptor antagonist, we performed binding affinity studies and an inositol phosphate production assay. Binding affinity of olmesartan and its related compounds to wild-type and mutant AT1 receptors demonstrated that interactions between olmesartan and Tyr113, Lys199, His256, and Gln257 in the AT1 receptor were important. The inositol phosphate production assay of olmesartan and related compounds using mutant receptors indicated that the inverse agonist activity required two interactions, that between the hydroxyl group of olmesartan and Tyr113 in the receptor and that between the carboxyl group of olmesartan and Lys199 and His256 in the receptor. Gln257 was found to be important for the interaction with olmesartan but not for the inverse agonist activity. Based on these results, we constructed a model for the interaction between olmesartan and the AT1 receptor. Although the activation of G protein-coupled receptors is initiated by anti-clockwise rotation of transmembrane (TM) III and TM VI followed by changes in the conformation of the receptor, in this model, cooperative interactions between the hydroxyl group and Tyr113 in TM III and between the carboxyl group and His256 in TM VI were essential for the potent inverse agonist activity of olmesartan. We speculate that the specific interaction of olmesartan with these two TMs is essential for stabilizing the AT1 receptor in an inactive conformation. A better understanding of the molecular mechanisms of the inverse agonism could be useful for the development of new G protein-coupled receptor antagonists with inverse agonist activity.
authors.affiliation: Department of Cardiology, Fukuoka University School of Medicine, Fukuoka 814-0180, Japan. miuras@cis.fukuoka-u.ac.jp
authors.forename: Shin-ichiro
authors.initials: S
authors.lastname: Miura
authors.forename: Masahiro
authors.initials: M
authors.lastname: Fujino
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hanzawa
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kiya
authors.forename: Satoshi
authors.initials: S
authors.lastname: Imaizumi
authors.forename: Yoshino
authors.initials: Y
authors.lastname: Matsuo
authors.forename: Sayo
authors.initials: S
authors.lastname: Tomita
authors.forename: Yoshinari
authors.initials: Y
authors.lastname: Uehara
authors.forename: Sadashiva S
authors.initials: SS
authors.lastname: Karnik
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Yanagisawa
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Koike
authors.forename: Issei
authors.initials: I
authors.lastname: Komuro
authors.forename: Keijiro
authors.initials: K
authors.lastname: Saku
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D019556:COS Cells; D002417:Cattle; D002522:Chlorocebus aethiops; D007093:Imidazoles / Q000494:pharmacology; D007295:Inositol Phosphates / Q000737:chemistry; D007700:Kinetics; D008956:Models, Chemical; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D051381:Rats; D044140:Receptor, Angiotensin, Type 1 / Q000819:agonists* / Q000737:chemistry*; D013777:Tetrazoles / Q000494:pharmacology
chemical_list: D007093:Imidazoles; D007295:Inositol Phosphates; D044140:Receptor, Angiotensin, Type 1; D013777:Tetrazoles; C437965:olmesartan