A monomeric G protein-coupled receptor isolated in a high-density lipoprotein particle efficiently activates its G protein

Matthew R. Whorton, Michael P. Bokoch, Søren G.F. Rasmussen, Bo Huang, Richard N. Zare, Brian Kobilka, Roger K. Sunahara

Research output: Contribution to journalArticle

510 Scopus citations

Abstract

G protein-coupled receptors (GPCRs) respond to a diverse array of ligands, mediating cellular responses to hormones and neurotransmitters, as well as the senses of smell and taste. The structures of the GPCR rhodopsin and several G proteins have been determined by x-ray crystallography, yet the organization of the signaling complex between GPCRs and G proteins is poorly understood. The observations that some GPCRs are obligate heterodimers, and that many GPCRs form both homo- and heterodimers, has led to speculation that GPCR dinners may be required for efficient activation of G proteins. However, technical limitations have precluded a definitive analysis of G protein coupling to monomeric GPCRs in a biochemically defined and membrane-bound system. Here we demonstrate that a prototypical GPCR, the β2-adrenergic receptor (β2AR), can be incorporated into a reconstituted high-density lipoprotein (rHDL) phospholipid bilayer particle together with the stimulatory heterotrimeric G protein, Gs. Single-molecule fluorescence imaging and FRET analysis demonstrate that a single β2AR is incorporated per rHDL particle. The monomeric β2AR efficiently activates Gs and displays GTP-sensitive allosteric ligand-binding properties. These data suggest that a monomeric receptor in a lipid bilayer is the minimal functional unit necessary for signaling, and that the cooperativity of agonist binding is due to G protein association with a receptor monomer and not receptor oligomerization.

Original languageEnglish (US)
Pages (from-to)7682-7687
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume104
Issue number18
DOIs
StatePublished - May 1 2007

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Keywords

  • Oligomerization
  • Single-molecule spectroscopy
  • β2-adrenergic receptor

ASJC Scopus subject areas

  • General

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