Allosteric modulation of β-arrestin-biased angiotensin II type 1 receptor signaling by membrane stretch.

Published

Journal Article

It has recently been appreciated that the angiotensin II type 1 receptor (AT1R), a prototypic member of the G protein-coupled receptor superfamily, also functions as a mechanosensor. Specifically, mechanical stretch activates the AT1R to promote downstream signaling mediated exclusively by the multifunctional scaffold protein, β-arrestin, in a manner consistent with previously identified β-arrestin-biased ligands. However, the ligand-independent mechanism by which mechanical stretch promotes β-arrestin-biased signaling remains unknown. Implicit in the concept of biased agonism (i.e. the ability of an agonist to activate a subset of receptor-mediated signaling pathways) is the notion that distinct active conformations of the receptor mediate differential activation of signaling pathways. Here we determined whether mechanical stretch stabilizes distinct β-arrestin-activating conformations of the AT1R by using β-arrestin2-biased agonists as conformational probes in pharmacological and biophysical assays. When tested at cells expressing the AT1R fused to β-arrestin (AT1R-β-arrestin2), we found that osmotic stretch increased the binding affinity and potency of the β-arrestin-biased agonist TRV120023, with no effect on the balanced agonist AngII. In addition, the effect of osmotic stretch on ERK activation was markedly augmented in cells expressing the AT1R-β-arrestin2 fusion compared with the wild type AT1R and completely blocked in cells expressing the AT1R-Gq fusion. Biophysical experiments with an intramolecular BRET β-arrestin2 biosensor revealed that osmotic stretch and TRV120023 activate AT1Rs to stabilize β-arrestin2 active conformations that differ from those stabilized by the AT1R activated by angiotensin II. Together, these data support a novel ligand-independent mechanism whereby mechanical stretch allosterically stabilizes specific β-arrestin-biased active conformations of the AT1R and has important implications for understanding pathophysiological AT1R signaling.

Full Text

Duke Authors

Cited Authors

  • Tang, W; Strachan, RT; Lefkowitz, RJ; Rockman, HA

Published Date

  • October 2014

Published In

Volume / Issue

  • 289 / 41

Start / End Page

  • 28271 - 28283

PubMed ID

  • 25170081

Pubmed Central ID

  • 25170081

Electronic International Standard Serial Number (EISSN)

  • 1083-351X

International Standard Serial Number (ISSN)

  • 0021-9258

Digital Object Identifier (DOI)

  • 10.1074/jbc.M114.585067

Language

  • eng