Ligand‐regulated oligomerization of β2‐adrenoceptors in a model lipid bilayer |
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| Authors: | Juan José Fung Xavier Deupi Leonardo Pardo Xiao Jie Yao Gisselle A Velez‐Ruiz Brian T DeVree Roger K Sunahara Brian K Kobilka |
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| Affiliation: | 1. Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA;2. Laboratori de Medicina Computacional, Unitat de Bioestadística, Facultat de Medicina, Universitat Autònoma de Barcelona, Barcelona, Spain;3. Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, USA |
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| Abstract: | The β2‐adrenoceptor (β2AR) was one of the first Family A G protein‐coupled receptors (GPCRs) shown to form oligomers in cellular membranes, yet we still know little about the number and arrangement of protomers in oligomers, the influence of ligands on the organization or stability of oligomers, or the requirement for other proteins to promote oligomerization. We used fluorescence resonance energy transfer (FRET) to characterize the oligomerization of purified β2AR site‐specifically labelled at three different positions with fluorophores and reconstituted into a model lipid bilayer. Our results suggest that the β2AR is predominantly tetrameric following reconstitution into phospholipid vesicles. Agonists and antagonists have little effect on the relative orientation of protomers in oligomeric complexes. In contrast, binding of inverse agonists leads to significant increases in FRET efficiencies for most labelling pairs, suggesting that this class of ligand promotes tighter packing of protomers and/or the formation of more complex oligomers by reducing conformational fluctuations in individual protomers. The results provide new structural insights into β2AR oligomerization and suggest a possible mechanism for the functional effects of inverse agonists. |
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| Keywords: | β 2‐Adrenoceptor FRET inverse agonist oligomers TM6 |
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