Catalytic activation of β-arrestin by GPCRs

beta-arrestins are critical regulator and transducer proteins for G-protein-coupled receptors (GPCRs). beta-arrestin is widely believed to be activated by forming a stable and stoichiometric GPCR-beta-arrestin scaffold complex, which requires and is driven by the phosphorylated tail of the GPCR. Here we demonstrate a distinct and additional mechanism of beta-arrestin activation that does not require stable GPCR-beta-arrestin scaffolding or the GPCR tail. Instead, it occurs through transient engagement of the GPCR core, which destabilizes a conserved inter-domain charge network in beta-arrestin. This promotes capture of beta-arrestin at the plasma membrane and its accumulation in clathrin-coated endocytic structures (CCSs) after dissociation from the GPCR, requiring a series of interactions with membrane phosphoinositides and CCS-lattice proteins. beta-arrestin clustering in CCSs in the absence of the upstream activating GPCR is associated with a beta-arrestin-dependent component of the cellular ERK (extracellular signal-regulated kinase) response. These results delineate a discrete mechanism of cellular beta-arrestin function that is activated catalytically by GPCRs.