Interaction of a non-peptide agonist with angiotensin II AT1 receptor mutants

• Published in: Canadian journal of physiology and pharmacology 2002-05, Vol.80 (5), p.413-417
• Main Authors: Costa-Neto, Claudio M, Miyakawa, Ayumi A, Pesquero, João B, Oliveira, Laerte, Hjorth, Siv A, Schwartz, Thue W, Paiva, Antonio CM
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence - physiology; Angiotensin II - metabolism; Angiotensin II - pharmacology; Animals; Biphenyl Compounds - metabolism; Biphenyl Compounds - pharmacology; Cercopithecus aethiops; Conferences; COS Cells; Dose-Response Relationship, Drug; Imidazoles - metabolism; Imidazoles - pharmacology; Molecular Sequence Data; Mutagenesis, Site-Directed; Peptides; Rats; Receptor, Angiotensin, Type 1; Receptors, Angiotensin - agonists; Receptors, Angiotensin - chemistry; Receptors, Angiotensin - genetics; Receptors, Angiotensin - metabolism
• ISSN: 0008-4212; 1205-7541
• DOI: 10.1139/y02-058

To identify residues of the rat AT 1A angiotensin II receptor involved with signal transduction and binding of the non-peptide agonist L-162,313 (5,7-dimethyl-2-ethyl-3-[[4-[2(n-butyloxycarbonylsulfonamido)-5-isobutyl-3-thienyl]phenyl]methyl]imidazol[4,5,6]-pyridine) we have performed ligand binding and inositol phosphate turnover assays in COS-7 cells transiently transfected with the wild-type and mutant forms of the receptor. Mutant receptors bore modifications in the extracellular region: T88H, Y92H, G196I, G196W, and D278E. Compound L-162,313 displaced [ 125 I]-Sar 1 ,Leu 8 -AngII from the mutants G196I and G196W with IC 50 values similar to that of the wild-type. The affinity was, however, slightly affected by the D278E mutation and more significantly by the T88H and Y92H mutations. In inositol phosphate turnover assays, the ability of L-162,313 to trigger the activation cascade was compared with that of angiotensin II. These assays showed that the G196W mutant reached a relative maximum activation exceeding that of the wild-type receptor; the efficacy was slightly reduced in the G196I mutant and further reduced in the T88H, Y92H, and D278E mutants. Our data suggest that residues of the extracellular domain of the AT 1 receptor are involved in the binding of the non-peptide ligand, or in a general receptor activation phenomenon that involves conformational modifications for a preferential binding of agonists or antagonists. Key words: angiotensin, receptor, GPCR, non-peptide agonist, transduction.