Distinct activation mechanisms of β-arrestin 1 revealed by 19F NMR spectroscopy

Abstract

{beta}-Arrestins ({beta}arrs) are functionally versatile proteins that play critical roles in the G-protein-coupled receptor (GPCR) signaling pathways. While the classical theory of GPCR-mediated {beta}arr activation centers around the formation of a stable complex between {beta}arr and the phosphorylated receptor tail, emerging evidences highlight the indispensable contribution from membrane lipids for many receptors. Due to the intrinsic complexity of {beta}arr conformational dynamics, detailed molecular mechanisms of its activation by different binding partners remain elusive. Herein we present a comprehensive study of the structural changes of {beta}arr1 in critical structural regions during activation using 19F NMR method. We demonstrate that phosphopeptides derived from different classes of GPCRs show distinct abilities in inducing {beta}arr1 activation. We further show that the membrane phosphoinositide PIP2 independently modulates {beta}arr1 conformational dynamics without displacing its autoinhibitory carboxyl tail, leading to a distinct partially activated state. Our results delineate two activation mechanisms of {beta}arr1 by different binding partners, uncovering a highly multifaceted conformational energy landscape for this protein family.