Distinct conformational changes in beta-arrestin report biased agonism at seven-transmembrane receptors.
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.
Shukla
Arun K
AK
Department of Medicine and Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
Violin
Jonathan D
JD
Whalen
Erin J
EJ
Gesty-Palmer
Diane
D
Shenoy
Sudha K
SK
Lefkowitz
Robert J
RJ
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
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