TY - JOUR

T1 - Ligand-specific regulation of the extracellular surface of a G-protein-coupled receptor

AU - Bokoch, Michael P

AU - Zou, Yaozhong

AU - Rasmussen, Søren Gøgsig Faarup

AU - Liu, Corey W

AU - Nygaard, Rie

AU - Rosenbaum, Daniel M

AU - Fung, Juan José

AU - Choi, Hee-Jung

AU - Thian, Foon Sun

AU - Kobilka, Tong Sun

AU - Puglisi, Joseph D

AU - Weis, William I

AU - Pardo, Leonardo

AU - Prosser, R Scott

AU - Mueller, Luciano

AU - Kobilka, Brian K

PY - 2010/1/7

Y1 - 2010/1/7

N2 - G-protein-coupled receptors (GPCRs) are seven-transmembrane proteins that mediate most cellular responses to hormones and neurotransmitters. They are the largest group of therapeutic targets for a broad spectrum of diseases. Recent crystal structures of GPCRs have revealed structural conservation extending from the orthosteric ligand-binding site in the transmembrane core to the cytoplasmic G-protein-coupling domains. In contrast, the extracellular surface (ECS) of GPCRs is remarkably diverse and is therefore an ideal target for the discovery of subtype-selective drugs. However, little is known about the functional role of the ECS in receptor activation, or about conformational coupling of this surface to the native ligand-binding pocket. Here we use NMR spectroscopy to investigate ligand-specific conformational changes around a central structural feature in the ECS of the beta(2) adrenergic receptor: a salt bridge linking extracellular loops 2 and 3. Small-molecule drugs that bind within the transmembrane core and exhibit different efficacies towards G-protein activation (agonist, neutral antagonist and inverse agonist) also stabilize distinct conformations of the ECS. We thereby demonstrate conformational coupling between the ECS and the orthosteric binding site, showing that drugs targeting this diverse surface could function as allosteric modulators with high subtype selectivity. Moreover, these studies provide a new insight into the dynamic behaviour of GPCRs not addressable by static, inactive-state crystal structures.

AB - G-protein-coupled receptors (GPCRs) are seven-transmembrane proteins that mediate most cellular responses to hormones and neurotransmitters. They are the largest group of therapeutic targets for a broad spectrum of diseases. Recent crystal structures of GPCRs have revealed structural conservation extending from the orthosteric ligand-binding site in the transmembrane core to the cytoplasmic G-protein-coupling domains. In contrast, the extracellular surface (ECS) of GPCRs is remarkably diverse and is therefore an ideal target for the discovery of subtype-selective drugs. However, little is known about the functional role of the ECS in receptor activation, or about conformational coupling of this surface to the native ligand-binding pocket. Here we use NMR spectroscopy to investigate ligand-specific conformational changes around a central structural feature in the ECS of the beta(2) adrenergic receptor: a salt bridge linking extracellular loops 2 and 3. Small-molecule drugs that bind within the transmembrane core and exhibit different efficacies towards G-protein activation (agonist, neutral antagonist and inverse agonist) also stabilize distinct conformations of the ECS. We thereby demonstrate conformational coupling between the ECS and the orthosteric binding site, showing that drugs targeting this diverse surface could function as allosteric modulators with high subtype selectivity. Moreover, these studies provide a new insight into the dynamic behaviour of GPCRs not addressable by static, inactive-state crystal structures.

KW - Adrenergic beta-2 Receptor Agonists

KW - Adrenergic beta-2 Receptor Antagonists

KW - Allosteric Regulation

KW - Binding Sites

KW - Crystallography, X-Ray

KW - Drug Inverse Agonism

KW - Ethanolamines

KW - Humans

KW - Ligands

KW - Lysine

KW - Methylation

KW - Models, Molecular

KW - Mutant Proteins

KW - Nuclear Magnetic Resonance, Biomolecular

KW - Propanolamines

KW - Protein Structure, Tertiary

KW - Receptors, Adrenergic, beta-2

KW - Static Electricity

KW - Substrate Specificity

U2 - 10.1038/nature08650

DO - 10.1038/nature08650

M3 - Journal article

C2 - 20054398

VL - 463

SP - 108

EP - 112

JO - Nature

JF - Nature

SN - 0028-0836

IS - 7277

ER -