Divergent transducer-specific molecular efficacies generate biased agonism at a G protein-coupled receptor (GPCR).

Journal Article (Journal Article)

The concept of "biased agonism" arises from the recognition that the ability of an agonist to induce a receptor-mediated response (i.e. "efficacy") can differ across the multiple signal transduction pathways (e.g. G protein and β-arrestin (βarr)) emanating from a single GPCR. Despite the therapeutic promise of biased agonism, the molecular mechanism(s) whereby biased agonists selectively engage signaling pathways remain elusive. This is due in large part to the challenges associated with quantifying ligand efficacy in cells. To address this, we developed a cell-free approach to directly quantify the transducer-specific molecular efficacies of balanced and biased ligands for the angiotensin II type 1 receptor (AT1R), a prototypic GPCR. Specifically, we defined efficacy in allosteric terms, equating shifts in ligand affinity (i.e. KLo/KHi) at AT1R-Gq and AT1R-βarr2 fusion proteins with their respective molecular efficacies for activating Gq and βarr2. Consistent with ternary complex model predictions, transducer-specific molecular efficacies were strongly correlated with cellular efficacies for activating Gq and βarr2. Subsequent comparisons across transducers revealed that biased AT1R agonists possess biased molecular efficacies that were in strong agreement with the signaling bias observed in cellular assays. These findings not only represent the first measurements of the thermodynamic driving forces underlying differences in ligand efficacy between transducers but also support a molecular mechanism whereby divergent transducer-specific molecular efficacies generate biased agonism at a GPCR.

Full Text

Duke Authors

Cited Authors

  • Strachan, RT; Sun, J-P; Rominger, DH; Violin, JD; Ahn, S; Rojas Bie Thomsen, A; Zhu, X; Kleist, A; Costa, T; Lefkowitz, RJ

Published Date

  • May 16, 2014

Published In

Volume / Issue

  • 289 / 20

Start / End Page

  • 14211 - 14224

PubMed ID

  • 24668815

Pubmed Central ID

  • PMC4022887

Electronic International Standard Serial Number (EISSN)

  • 1083-351X

Digital Object Identifier (DOI)

  • 10.1074/jbc.M114.548131


  • eng

Conference Location

  • United States