Distinct conformational changes in beta-arrestin report biased agonism at seven-transmembrane receptors

Proc Natl Acad Sci U S A. 2008 Jul 22;105(29):9988-93. doi: 10.1073/pnas.0804246105. Epub 2008 Jul 11.

Abstract

Beta-arrestins critically regulate G protein-coupled receptors (GPCRs), also known as seven-transmembrane receptors (7TMRs), both by inhibiting classical G protein signaling and by initiating distinct beta-arrestin-mediated signaling. The recent discovery of beta-arrestin-biased ligands and receptor mutants has allowed characterization of these independent "G protein-mediated" and "beta-arrestin-mediated" signaling mechanisms of 7TMRs. However, the molecular mechanisms underlying the dual functions of beta-arrestins remain unclear. Here, using an intramolecular BRET (bioluminescence resonance energy transfer)-based biosensor of beta-arrestin 2 and a combination of biased ligands and/or biased mutants of three different 7TMRs, we provide evidence that beta-arrestin can adopt multiple "active" conformations. Surprisingly, phosphorylation-deficient mutants of the receptors are also capable of directing similar conformational changes in beta-arrestin as is the wild-type receptor. This indicates that distinct receptor conformations induced and/or stabilized by different ligands can promote distinct and functionally specific conformations in beta-arrestin even in the absence of receptor phosphorylation. Our data thus highlight another interesting aspect of 7TMR signaling--i.e., functionally specific receptor conformations can be translated to downstream effectors such as beta-arrestins, thereby governing their functional specificity.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arrestins / chemistry*
  • Arrestins / genetics
  • Arrestins / metabolism
  • Biophysical Phenomena
  • Biophysics
  • Biosensing Techniques
  • Cells
  • Fluorescence Resonance Energy Transfer
  • Humans
  • Ligands
  • Mutagenesis, Site-Directed
  • Phosphorylation
  • Protein Conformation
  • Receptor, Angiotensin, Type 1 / agonists
  • Receptor, Angiotensin, Type 1 / chemistry
  • Receptor, Angiotensin, Type 1 / genetics
  • Receptors, G-Protein-Coupled / agonists
  • Receptors, G-Protein-Coupled / chemistry*
  • Receptors, G-Protein-Coupled / genetics
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • beta-Arrestin 2
  • beta-Arrestins

Substances

  • ARRB2 protein, human
  • Arrestins
  • Ligands
  • Receptor, Angiotensin, Type 1
  • Receptors, G-Protein-Coupled
  • Recombinant Fusion Proteins
  • beta-Arrestin 2
  • beta-Arrestins
  • seven-transmembrane G-protein-coupled receptor