Ligand-regulated oligomerization of Β 2-adrenoceptors in a model lipid bilayer

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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158 Citations (Scopus)

Abstract

The Β 2-adrenoceptor (Β 2 AR) 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 Β 2 AR site-specifically labelled at three different positions with fluorophores and reconstituted into a model lipid bilayer. Our results suggest that the Β 2 AR 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 Β 2 AR oligomerization and suggest a possible mechanism for the functional effects of inverse agonists.

Original languageEnglish
Pages (from-to)3315-3328
Number of pages14
JournalThe EMBO Journal
Volume28
Issue number21
DOIs
Publication statusPublished - Nov 2009
Externally publishedYes

Keywords

  • Β 2-Adrenoceptor
  • FRET
  • Inverse agonist
  • Oligomers
  • TM6

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