GPCR-mediated β-arrestin activation deconvoluted with single-molecule precision
Wesley B. Asher, Daniel S. Terry, G. Glenn Gregorio, Alem W. Kahsai, Alessandro Borgia, Bing Xie, Arnab Modak, Ying Zhu, Wonjo Jang, Alekhya Govindaraju, Li-Yin Huang, Asuka Inoue, Nevin A. Lambert, Vsevolod V. Gurevich, Lei Shi, Robert J. Lefkowitz, Scott C. Blanchard, Jonathan A. Javitch
Abstract
β-arrestins bind G protein-coupled receptors to terminate G protein signaling and to facilitate other downstream signaling pathways. Using single-molecule fluorescence resonance energy transfer imaging, we show that β-arrestin is strongly autoinhibited in its basal state. Its engagement with a phosphopeptide mimicking phosphorylated receptor tail efficiently releases the β-arrestin tail from its N domain to assume distinct conformations. Unexpectedly, we find that β-arrestin binding to phosphorylated receptor, with a phosphorylation barcode identical to the isolated phosphopeptide, is highly inefficient and that agonist-promoted receptor activation is required for β-arrestin activation, consistent with the release of a sequestered receptor C tail. These findings, together with focused cellular investigations, reveal that agonism and receptor C-tail release are specific determinants of the rate and efficiency of β-arrestin activation by phosphorylated receptor. We infer that receptor phosphorylation patterns, in combination with receptor agonism, synergistically establish the strength and specificity with which diverse, downstream β-arrestin-mediated events are directed.