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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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% inositol phosphate (IP) production with or without 1 µM of olmesartan and olmesartan-related compounds in COS1 cells transiently expressing the wild-type (WT) and N111G AT1 receptor.The test compounds were added 1 h before the measurement of IP. 100% IP production indicates basal IP production in WT (1,033±149 cpm) and N111G (2,087±414 cpm) AT1 receptor-transfected cells. Ang II (0.1 µM)-induced maximum IP production in WT and N111G AT1 receptor-transfected cells were 4,037±479 cpm and 4,138±362 cpm, respectively. n=4–7, *p<0.05 vs. no treatment.
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pone-0037974-g002: % inositol phosphate (IP) production with or without 1 µM of olmesartan and olmesartan-related compounds in COS1 cells transiently expressing the wild-type (WT) and N111G AT1 receptor.The test compounds were added 1 h before the measurement of IP. 100% IP production indicates basal IP production in WT (1,033±149 cpm) and N111G (2,087±414 cpm) AT1 receptor-transfected cells. Ang II (0.1 µM)-induced maximum IP production in WT and N111G AT1 receptor-transfected cells were 4,037±479 cpm and 4,138±362 cpm, respectively. n=4–7, *p<0.05 vs. no treatment.

Mentions: Next, we analyzed whether the olmesartan-related compounds induced agonism toward inositol phosphate (IP) production on the AT1-WT and N111G receptors (Fig. 2). R781253 and R781254 retain inverse agonism. After modification of the phenolic group of R781253, R791212 lost inverse agonism and showed neutral antagonism. Interestingly, R794847 lost neutral antagonism, and showed agonism, suggesting that modification of the carboxyl group to the carbamoyl group in addition to insertion of a hydroxyphenyl group in the biphenyltetrazole scaffold induced agonism. Although R795100 and R801832 showed agonism, the strength of these agonism were similar to that of R794847. All of the olmesartan-related compounds showed similar degrees of neutral antagonism and agonism toward the AT1-N111G receptor compared with the pharmacological behaviors of these compounds in the AT1-WT receptor. We selected R794847 as an agonist. Thus, in subsequent analyses, olmesartan was used as an inverse agonist, R239470 was a neutral antagonist, and R794847 was an agonist.


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)

% inositol phosphate (IP) production with or without 1 µM of olmesartan and olmesartan-related compounds in COS1 cells transiently expressing the wild-type (WT) and N111G AT1 receptor.The test compounds were added 1 h before the measurement of IP. 100% IP production indicates basal IP production in WT (1,033±149 cpm) and N111G (2,087±414 cpm) AT1 receptor-transfected cells. Ang II (0.1 µM)-induced maximum IP production in WT and N111G AT1 receptor-transfected cells were 4,037±479 cpm and 4,138±362 cpm, respectively. n=4–7, *p<0.05 vs. no treatment.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3375280&req=5

pone-0037974-g002: % inositol phosphate (IP) production with or without 1 µM of olmesartan and olmesartan-related compounds in COS1 cells transiently expressing the wild-type (WT) and N111G AT1 receptor.The test compounds were added 1 h before the measurement of IP. 100% IP production indicates basal IP production in WT (1,033±149 cpm) and N111G (2,087±414 cpm) AT1 receptor-transfected cells. Ang II (0.1 µM)-induced maximum IP production in WT and N111G AT1 receptor-transfected cells were 4,037±479 cpm and 4,138±362 cpm, respectively. n=4–7, *p<0.05 vs. no treatment.
Mentions: Next, we analyzed whether the olmesartan-related compounds induced agonism toward inositol phosphate (IP) production on the AT1-WT and N111G receptors (Fig. 2). R781253 and R781254 retain inverse agonism. After modification of the phenolic group of R781253, R791212 lost inverse agonism and showed neutral antagonism. Interestingly, R794847 lost neutral antagonism, and showed agonism, suggesting that modification of the carboxyl group to the carbamoyl group in addition to insertion of a hydroxyphenyl group in the biphenyltetrazole scaffold induced agonism. Although R795100 and R801832 showed agonism, the strength of these agonism were similar to that of R794847. All of the olmesartan-related compounds showed similar degrees of neutral antagonism and agonism toward the AT1-N111G receptor compared with the pharmacological behaviors of these compounds in the AT1-WT receptor. We selected R794847 as an agonist. Thus, in subsequent analyses, olmesartan was used as an inverse agonist, R239470 was a neutral antagonist, and R794847 was an agonist.

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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