Ligand-specific regulation of the extracellular surface of a G-protein-coupled receptor.
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.
Bokoch
Michael P
MP
Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California 94305, USA.
Zou
Yaozhong
Y
Rasmussen
Søren G F
SG
Liu
Corey W
CW
Nygaard
Rie
R
Rosenbaum
Daniel M
DM
Fung
Juan José
JJ
Choi
Hee-Jung
HJ
Thian
Foon Sun
FS
Kobilka
Tong Sun
TS
Puglisi
Joseph D
JD
Weis
William I
WI
Pardo
Leonardo
L
Prosser
R Scott
RS
Mueller
Luciano
L
Kobilka
Brian K
BK
D058666:Adrenergic beta-2 Receptor Agonists; D058672:Adrenergic beta-2 Receptor Antagonists; D000494:Allosteric Regulation / Q000187:drug effects; D001665:Binding Sites; D018360:Crystallography, X-Ray; D054314:Drug Inverse Agonism; D004983:Ethanolamines / Q000494:pharmacology; D000068759:Formoterol Fumarate; D006801:Humans; D008024:Ligands; D008239:Lysine / Q000031:analogs & derivatives / Q000378:metabolism; D008745:Methylation; D008958:Models, Molecular; D050505:Mutant Proteins; D019906:Nuclear Magnetic Resonance, Biomolecular; D011412:Propanolamines / Q000378:metabolism / Q000494:pharmacology; D017434:Protein Structure, Tertiary / Q000187:drug effects; D018343:Receptors, Adrenergic, beta-2 / Q000737:chemistry* / Q000378:metabolism*; D055672:Static Electricity; D013379:Substrate Specificity
D058666:Adrenergic beta-2 Receptor Agonists; D058672:Adrenergic beta-2 Receptor Antagonists; D004983:Ethanolamines; D008024:Ligands; D050505:Mutant Proteins; D011412:Propanolamines; D018343:Receptors, Adrenergic, beta-2; C018926:epsilon N-dimethyllysine; C014382:carazolol; D008239:Lysine; D000068759:Formoterol Fumarate