Negative cooperativity across ß1-adrenoceptor homodimers provides insights into the nature of the secondary low-affinity CGP 12177 ß1-adrenoceptor binding conformation.
FASEB J
; 29(7): 2859-71, 2015 Jul.
Article
em En
| MEDLINE
| ID: mdl-25837585
ABSTRACT
At the ß1-adrenoceptor, CGP 12177 potently antagonizes agonist responses at the primary high-affinity catecholamine conformation while also exerting agonist effects of its own through a secondary low-affinity conformation. A recent mutagenesis study identified transmembrane region (TM)4 of the ß1-adrenoceptor as key for this low-affinity conformation. Others suggested that TM4 has a role in ß1-adrenoceptor oligomerization. Here, assessment of the dissociation rate of a fluorescent analog of CGP 12177 [bordifluoropyrromethane-tetramethylrhodamine-(±)CGP 12177 (BODIPY-TMR-CGP)] at the human ß1-adrenoceptor expressed in Chinese hamster ovary cells revealed negative cooperative interactions between 2 distinct ß1-adrenoceptor conformations. The dissociation rate of 3 nM BODIPY-TMR-CGP was 0.09 ± 0.01 min(-1) in the absence of competitor ligands, and this was enhanced 2.2- and 2.1-fold in the presence of 1 µM CGP 12177 and 1 µM propranolol, respectively. These effects on the BODIPY-TMR-CGP dissociation rate were markedly enhanced in ß1-adrenoceptor homodimers constrained by bimolecular fluorescence complementation (9.8- and 9.9-fold for 1 µM CGP 12177 and 1 µM propranolol, respectively) and abolished in ß1-adrenoceptors containing TM4 mutations vital for the second conformation pharmacology. This study suggests that negative cooperativity across a ß1-adrenoceptor homodimer may be responsible for generating the low-affinity pharmacology of the secondary ß1-adrenoceptor conformation.
Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Propanolaminas
/
Receptores Adrenérgicos beta 1
/
Antagonistas Adrenérgicos beta
Limite:
Animals
/
Humans
Idioma:
En
Revista:
FASEB J
Assunto da revista:
BIOLOGIA
/
FISIOLOGIA
Ano de publicação:
2015
Tipo de documento:
Article
País de afiliação:
Reino Unido