- Author
- Shukla AK,Violin JD,Whalen EJ,Gesty-Palmer D,Shenoy SK,Lefkowitz RJ
- Title
- Distinct conformational changes in {beta}-arrestin report biased agonism at seven-transmembrane receptors.
- Publication Date
- 7/11/2008
- Pages
- -
- Journal Name
- Proceedings of the National Academy of Sciences of the United States of America
- 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.
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