Dynamics of receptor/G protein coupling in living cells

EMBO J. 2005 Dec 7;24(23):4106-14. doi: 10.1038/sj.emboj.7600870. Epub 2005 Nov 17.


The interaction of activated G protein-coupled receptors with G proteins is a key event in signal transduction. Here, using a fluorescence resonance energy transfer (FRET)-based assay, we measure directly and in living cells the interaction of YFP-labeled alpha(2A)-adrenergic receptors with CFP-labeled G proteins. Upon agonist stimulation, a small, concentration-dependent increase in FRET was observed. No specific basal FRET was detected in the absence of agonist. Kinetics of the onset of receptor/G protein interaction were <100 ms and depended on expression levels of Galpha. Simultaneously recorded G protein-regulated inwardly rectifying K(+) channel currents revealed a maximal current response already at agonist concentrations producing submaximal FRET amplitudes. By analyzing FRET signals in the presence of a Galpha mutant, which dissociates more slowly from activated receptors, it was demonstrated that only a fraction of wild-type G proteins interacts with the activated receptor at any time. Our data suggest that alpha(2A)-adrenergic receptors and G proteins interact by rapid collision coupling and indicate that there is no significant precoupling between these receptors and G proteins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenergic alpha-2 Receptor Agonists
  • Bacterial Proteins / metabolism
  • Cell Line
  • Cell Membrane / metabolism
  • Fluorescence Resonance Energy Transfer
  • Fluorescent Dyes
  • GTP-Binding Proteins / agonists
  • GTP-Binding Proteins / metabolism*
  • Humans
  • Kinetics
  • Luminescent Proteins / metabolism
  • Receptors, Adrenergic, alpha-2 / metabolism*
  • Receptors, G-Protein-Coupled / agonists
  • Receptors, G-Protein-Coupled / metabolism*
  • Staining and Labeling


  • ADRA2A protein, human
  • Adrenergic alpha-2 Receptor Agonists
  • Bacterial Proteins
  • Fluorescent Dyes
  • Luminescent Proteins
  • Receptors, Adrenergic, alpha-2
  • Receptors, G-Protein-Coupled
  • yellow fluorescent protein, Bacteria
  • GTP-Binding Proteins