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Small molecules with similar structures exhibit agonist, neutral antagonist or inverse agonist activity toward angiotensin II type 1 receptor.

Miura S, Kiya Y, Hanzawa H, Nakao N, Fujino M, Imaizumi S, Matsuo Y, Yanagisawa H, Koike H, Komuro I, Karnik SS, Saku K - PLoS ONE (2012)

Bottom Line: The results of substituted cysteine accessibility mapping studies support the novel concept that ligand-induced changes in the conformation of TM3 play a role in stabilizing GPCR.Although the agonist-, neutral antagonist and inverse agonist-binding sites in the AT(1) receptor are similar, each ligand induced specific conformational changes in TM3.In addition, all of the experimental data were obtained with functional receptors in a native membrane environment (in situ).

View Article: PubMed Central - PubMed

Affiliation: Department of Cardiology, Fukuoka University School of Medicine, Fukuoka, Japan. miuras@cis.fukuoka-u.ac.jp

ABSTRACT
Small differences in the chemical structures of ligands can be responsible for agonism, neutral antagonism or inverse agonism toward a G-protein-coupled receptor (GPCR). Although each ligand may stabilize the receptor conformation in a different way, little is known about the precise conformational differences. We synthesized the angiotensin II type 1 receptor blocker (ARB) olmesartan, R239470 and R794847, which induced inverse agonism, antagonism and agonism, respectively, and then investigated the ligand-specific changes in the receptor conformation with respect to stabilization around transmembrane (TM)3. The results of substituted cysteine accessibility mapping studies support the novel concept that ligand-induced changes in the conformation of TM3 play a role in stabilizing GPCR. Although the agonist-, neutral antagonist and inverse agonist-binding sites in the AT(1) receptor are similar, each ligand induced specific conformational changes in TM3. In addition, all of the experimental data were obtained with functional receptors in a native membrane environment (in situ).

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Changes in cysteine accessibility in COS1 cells expressing C76A/C289A mutant receptors in which the transmenbrane 3 residues from Ala106 to Phe117, except for position 113, were successively replaced by cysteine.1 µM of ARBs, n=4–9, *p<0.05 vs. no treatment. #p<0.05 vs. C76A/C289A.
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pone-0037974-g003: Changes in cysteine accessibility in COS1 cells expressing C76A/C289A mutant receptors in which the transmenbrane 3 residues from Ala106 to Phe117, except for position 113, were successively replaced by cysteine.1 µM of ARBs, n=4–9, *p<0.05 vs. no treatment. #p<0.05 vs. C76A/C289A.

Mentions: We found that olmesartan, R239470 and R794847 acted as an inverse agonist, a neutral antagonist and an agonist, respectively. Therefore, we investigated the agonist-, neutral antagonist- and inverse agonist-specific changes in receptor conformation with regard to stabilization around TM3. Differences in cysteine accessibility by ligand (-), olmesartan, R239470 and R794847 in AT1-WT and mutant receptors are shown in Fig. 3. The % inhibition of 125I-[Sar1, Ile8] AngII binding with the unliganded/unoccupied receptor [ligands (-)] in the A106C, V108C, S109C, N111C, L112C, S115C, V116C and F117C mutants in the C76A/C289A background were significantly higher than those in the C76A/C289A mutant with ligand (-), indicating that Ala106, Val108, Ser109, Asn111, Leu112, Ser115, Val116 and Phe117 face toward the ligand pocket of Ang II. In particular, the % inhibitions of the C76A/V108C/C289A and C76A/L112C/C289A mutants with ligand (-) were very high. Val108 and Leu112 definitely entered the ligand pocket.


Small molecules with similar structures exhibit agonist, neutral antagonist or inverse agonist activity toward angiotensin II type 1 receptor.

Miura S, Kiya Y, Hanzawa H, Nakao N, Fujino M, Imaizumi S, Matsuo Y, Yanagisawa H, Koike H, Komuro I, Karnik SS, Saku K - PLoS ONE (2012)

Changes in cysteine accessibility in COS1 cells expressing C76A/C289A mutant receptors in which the transmenbrane 3 residues from Ala106 to Phe117, except for position 113, were successively replaced by cysteine.1 µM of ARBs, n=4–9, *p<0.05 vs. no treatment. #p<0.05 vs. C76A/C289A.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3375280&req=5

pone-0037974-g003: Changes in cysteine accessibility in COS1 cells expressing C76A/C289A mutant receptors in which the transmenbrane 3 residues from Ala106 to Phe117, except for position 113, were successively replaced by cysteine.1 µM of ARBs, n=4–9, *p<0.05 vs. no treatment. #p<0.05 vs. C76A/C289A.
Mentions: We found that olmesartan, R239470 and R794847 acted as an inverse agonist, a neutral antagonist and an agonist, respectively. Therefore, we investigated the agonist-, neutral antagonist- and inverse agonist-specific changes in receptor conformation with regard to stabilization around TM3. Differences in cysteine accessibility by ligand (-), olmesartan, R239470 and R794847 in AT1-WT and mutant receptors are shown in Fig. 3. The % inhibition of 125I-[Sar1, Ile8] AngII binding with the unliganded/unoccupied receptor [ligands (-)] in the A106C, V108C, S109C, N111C, L112C, S115C, V116C and F117C mutants in the C76A/C289A background were significantly higher than those in the C76A/C289A mutant with ligand (-), indicating that Ala106, Val108, Ser109, Asn111, Leu112, Ser115, Val116 and Phe117 face toward the ligand pocket of Ang II. In particular, the % inhibitions of the C76A/V108C/C289A and C76A/L112C/C289A mutants with ligand (-) were very high. Val108 and Leu112 definitely entered the ligand pocket.

Bottom Line: The results of substituted cysteine accessibility mapping studies support the novel concept that ligand-induced changes in the conformation of TM3 play a role in stabilizing GPCR.Although the agonist-, neutral antagonist and inverse agonist-binding sites in the AT(1) receptor are similar, each ligand induced specific conformational changes in TM3.In addition, all of the experimental data were obtained with functional receptors in a native membrane environment (in situ).

View Article: PubMed Central - PubMed

Affiliation: Department of Cardiology, Fukuoka University School of Medicine, Fukuoka, Japan. miuras@cis.fukuoka-u.ac.jp

ABSTRACT
Small differences in the chemical structures of ligands can be responsible for agonism, neutral antagonism or inverse agonism toward a G-protein-coupled receptor (GPCR). Although each ligand may stabilize the receptor conformation in a different way, little is known about the precise conformational differences. We synthesized the angiotensin II type 1 receptor blocker (ARB) olmesartan, R239470 and R794847, which induced inverse agonism, antagonism and agonism, respectively, and then investigated the ligand-specific changes in the receptor conformation with respect to stabilization around transmembrane (TM)3. The results of substituted cysteine accessibility mapping studies support the novel concept that ligand-induced changes in the conformation of TM3 play a role in stabilizing GPCR. Although the agonist-, neutral antagonist and inverse agonist-binding sites in the AT(1) receptor are similar, each ligand induced specific conformational changes in TM3. In addition, all of the experimental data were obtained with functional receptors in a native membrane environment (in situ).

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