TY - JOUR
T1 - A monomeric G protein-coupled receptor isolated in a high-density lipoprotein particle efficiently activates its G protein
AU - Whorton, Matthew R.
AU - Bokoch, Michael P.
AU - Rasmussen, Søren G.F.
AU - Huang, Bo
AU - Zare, Richard N.
AU - Kobilka, Brian
AU - Sunahara, Roger K.
PY - 2007/5/1
Y1 - 2007/5/1
N2 - 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.
AB - 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.
KW - Oligomerization
KW - Single-molecule spectroscopy
KW - β2-adrenergic receptor
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U2 - 10.1073/pnas.0611448104
DO - 10.1073/pnas.0611448104
M3 - Article
C2 - 17452637
AN - SCOPUS:34250666273
SN - 0027-8424
VL - 104
SP - 7682
EP - 7687
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 18
ER -