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

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 dimers 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 beta2-adrenergic receptor (beta2AR), 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 beta2AR is incorporated per rHDL particle. The monomeric beta2AR 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.

SUBMITTER: Whorton MR

PROVIDER: S-EPMC1863461 | biostudies-literature | 2007 May

REPOSITORIES: biostudies-literature

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

Whorton Matthew R MR Bokoch Michael P MP Rasmussen Søren G F SG Huang Bo B Zare Richard N RN Kobilka Brian B Sunahara Roger K RK

Proceedings of the National Academy of Sciences of the United States of America 20070423 18

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, h ...[more]

PMID: 17452637

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Project description:High-density lipoprotein (HDL) is a mixture of complex particles mediating reverse cholesterol transport (RCT) and several cytoprotective activities. Despite its relevance for human health, many aspects of HDL-mediated lipid trafficking and cellular signaling remain elusive at the mo-lecular level. During HDL’s journey throughout the body, its functions are mediated through in-teractions with cell surface receptors on different cell types. To characterize and better under-stand the functional interplay between HDL particles and tissue, we analyzed the sur-faceome-residing receptor neighborhoods with which HDL potentially interacts. We applied a combination of chemoproteomic technologies including automated cell surface capturing (au-to-CSC) and HATRIC-based ligand–receptor capturing (HATRIC-LRC) on four different cellular model systems mimicking tissues relevant for RCT. The surfaceome analysis of EA.hy926, HEPG2, foam cells, and human aortic endothelial cells (HAECs) revealed the main currently known HDL scavenger receptor B1 (SCRB1), as well as 155 shared cell surface receptors repre-senting potential HDL-receptor interaction candidates . Since vascular endotheli-al growth factor A (VEGF-A) was recently found as a regulatory factor of transendothelial transport of HDL, we next analyzed the VEGF-modulated surfaceome of HAEC using the au-to-CSC technology. VEGF-A treatment led to the remodeling of the surfaceome of HAEC cells, including the previously reported higher surfaceome abundance of SCRB1. In total, 165 addition-al receptors were found on HAEC upon VEGF-A treatment representing SCRB1 co-regulated re-ceptors potentially involved in HDL function. Using the HATRIC-LRC technology on human endothelial cells, we specifically aimed for the identification of other bona fide (co-)receptors of HDL beyond SCRB1. HATRIC-LRC enabled, next to SCRB1, the identification of the receptor ty-rosine-protein kinase Mer (MERTK). Through RNA interference, we revealed its contribution to endothelial HDL binding and uptake. Furthermore, subsequent proximity ligation assays (PLAs) demonstrated the spatial vicinity of MERTK and SCRB1 on the endothelial cell surface. The data shown provide direct evidence for a complex and dynamic HDL receptome and that receptor nanoscale organization may influence binding and uptake of HDL.

Dataset Information

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

Publications

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

Similar Datasets

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