Inhibition of spontaneous beta 2-adrenergic activation rescues beta 1-adrenergic contractile response in cardiomyocytes overexpressing beta 2-adrenoceptor.

Published

Journal Article

Cardiac-specific overexpression of the human beta(2)-adrenergic receptor (AR) in transgenic mice (TG4) enhances basal cardiac function due to ligand-independent spontaneous beta(2)-AR activation. However, agonist-mediated stimulation of either beta(1)-AR or beta(2)-AR fails to further enhance contractility in TG4 ventricular myocytes. Although the lack of beta(2)-AR response has been ascribed to an efficient coupling of the receptor to pertussis toxin-sensitive G(i) proteins in addition to G(s), the contractile response to beta(1)-AR stimulation by norepinephrine and an alpha(1)-adrenergic antagonist prazosin is not restored by pertussis toxin treatment despite a G(i) protein elevation of 1.7-fold in TG4 hearts. Since beta-adrenergic receptor kinase, betaARK1, activity remains unaltered, the unresponsiveness of beta(1)-AR is not caused by betaARK1-mediated receptor desensitization. In contrast, pre-incubation of cells with anti-adrenergic reagents such as muscarinic receptor agonist, carbachol (10(-5)m), or a beta(2)-AR inverse agonist, ICI 118,551 (5 x 10(-7)m), to abolish spontaneous beta(2)-AR signaling, both reduce the base-line cAMP and contractility and, surprisingly, restore the beta(1)-AR contractile response. The "rescued" contractile response is completely reversed by a beta(1)-AR antagonist, CGP 20712A. Furthermore, these results from the transgenic animals are corroborated by in vitro acute gene manipulation in cultured wild type adult mouse ventricular myocytes. Adenovirus-directed overexpression of the human beta(2)-AR results in elevated base-line cAMP and contraction associated with a marked attenuation of beta(1)-AR response; carbachol pretreatment fully revives the diminished beta(1)-AR contractile response. Thus, we conclude that constitutive beta(2)-AR activation induces a heterologous desensitization of beta(1)-ARs independent of betaARK1 and G(i) proteins; suppression of the constitutive beta(2)-AR signaling by either a beta(2)-AR inverse agonist or stimulation of the muscarinic receptor rescues the beta(1)-ARs from desensitization, permitting agonist-induced contractile response.

Full Text

Duke Authors

Cited Authors

  • Zhang, SJ; Cheng, H; Zhou, YY; Wang, DJ; Zhu, W; Ziman, B; Spurgoen, H; Lefkowitz, RJ; Lakatta, EG; Koch, WJ; Xiao, RP

Published Date

  • July 14, 2000

Published In

Volume / Issue

  • 275 / 28

Start / End Page

  • 21773 - 21779

PubMed ID

  • 10787424

Pubmed Central ID

  • 10787424

International Standard Serial Number (ISSN)

  • 0021-9258

Digital Object Identifier (DOI)

  • 10.1074/jbc.M909484199

Language

  • eng

Conference Location

  • United States