Agonist dose-dependent phosphorylation by protein kinase A and G protein-coupled receptor kinase regulates β2 adrenoceptor coupling to Gi proteins in cardiomyocytes

Ruijie Liu, Biswarathan Ramani, Dagoberto Soto, Vania De Arcangelis, Yang Kevin Xiang

Research output: Contribution to journalArticle

41 Scopus citations

Abstract

Adrenoceptors receptors (ARs) play a pivotal role in regulating cardiovascular response to catecholamines during β2ARs, prototypical G protein-coupled receptors (GPCRs), expressed in animal hearts, display dual coupling to both Gs and Gi proteins to control the adenylyl cyclase-cAMP dependent protein kinase A (PKA) pathway to regulate contraction responses. Here, we showed that β2AR coupling to Gi proteins was agonist dose-dependent and occurred only at high concentrations in mouse cardiac myocytes. Both β2AR-induced PKA activity, measured by fluorescence resonance energy transfer (FRET) imaging, and the increase in myocyte contraction rate displayed sensitivity to the Gi inhibitor pertussis toxin (PTX). Further studies revealed that β 2ARs underwent PKA phosphorylation at a broad range of agonist concentrations. Disruption of the PKA phosphorylation sites on the β2AR blocked receptor/Gi coupling. However, a sufficient β2AR/Gi coupling was also dependent on the G protein-coupled receptor kinase (GRK)-mediated phosphorylation of the receptors, which only occurred at high concentrations of agonist (≥100 nM). Disruption of the GRK phosphorylation sites on the β2AR blocked receptor internalization and coupling to Gi proteins, probably by preventing the receptor's transportation to access Gi proteins. Furthermore, neither PKA nor GRK site mutated receptors displayed sensitivity to the Gi-specific inhibitor, GiCT. Together, our studies revealed distinct roles of PKA and GRK phosphorylation of β2AR for agonist dose-dependent coupling to Gi proteins in cardiac myocytes, which may protect cells from overstimulation under high concentrations of catecholamines.

Original languageEnglish (US)
Pages (from-to)32279-32287
Number of pages9
JournalJournal of Biological Chemistry
Volume284
Issue number47
DOIs
StatePublished - Nov 20 2009
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology

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