title: Distinct conformational changes in beta-arrestin report biased agonism at seven-transmembrane receptors.
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.
authors.affiliation: Department of Medicine and Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Arun K
authors.initials: AK
authors.lastname: Shukla
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Violin
authors.forename: Erin J
authors.initials: EJ
authors.lastname: Whalen
authors.forename: Diane
authors.initials: D
authors.lastname: Gesty-Palmer
authors.forename: Sudha K
authors.initials: SK
authors.lastname: Shenoy
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Lefkowitz
mesh_terms: D019390:Arrestins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D055592:Biophysical Phenomena; D001703:Biophysics; D015374:Biosensing Techniques; D002477:Cells; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D008024:Ligands; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011487:Protein Conformation; D044140:Receptor, Angiotensin, Type 1 / Q000819:agonists / Q000737:chemistry / Q000235:genetics; D043562:Receptors, G-Protein-Coupled / Q000819:agonists / Q000737:chemistry* / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
chemical_list: C000605254:ARRB2 protein, human; D019390:Arrestins; D008024:Ligands; D044140:Receptor, Angiotensin, Type 1; D043562:Receptors, G-Protein-Coupled; D011993:Recombinant Fusion Proteins; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins; C450520:seven-transmembrane G-protein-coupled receptor