title: Allosteric modulation of β-arrestin-biased angiotensin II type 1 receptor signaling by membrane stretch.
abstract: 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.
authors.affiliation: From the Departments of Medicine.
authors.forename: Wei
authors.initials: W
authors.lastname: Tang
authors.affiliation: From the Departments of Medicine, Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710.
authors.forename: Ryan T
authors.initials: RT
authors.lastname: Strachan
authors.affiliation: From the Departments of Medicine, Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Lefkowitz
authors.affiliation: From the Departments of Medicine, Cell Biology, and Molecular Genetics and Microbiology, and h.rockman@duke.edu.
authors.forename: Howard A
authors.initials: HA
authors.lastname: Rockman
mesh_terms: D000494:Allosteric Regulation; D000804:Angiotensin II / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019390:Arrestins / Q000235:genetics / Q000378:metabolism*; D001696:Biomechanical Phenomena; D015374:Biosensing Techniques; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006801:Humans; D040542:Mechanotransduction, Cellular; D009842:Oligopeptides / Q000494:pharmacology; D009997:Osmotic Pressure; D044140:Receptor, Angiotensin, Type 1 / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism*; D000071557:beta-Arrestins
chemical_list: D019390:Arrestins; D009842:Oligopeptides; D044140:Receptor, Angiotensin, Type 1; D011993:Recombinant Fusion Proteins; D000071557:beta-Arrestins; C555535:sarcosine-arginyl-valyl-tyrosyl-lysyl-histidyl-prolyl-alanine; D000804:Angiotensin II; D048049:Extracellular Signal-Regulated MAP Kinases
keywords: Allosteric Regulation; Angiotensin II; Cell Signaling; Conformational Change; Mechanotransduction