The Stability of the G Protein-coupled Receptor-β-Arrestin Interaction Determines the Mechanism and Functional Consequence of ERK Activation

Abstract By binding to agonist-activated G protein-coupled receptors (GPCRs), β-arrestins mediate homologous receptor desensitization and endocytosis via clathrin-coated pits. Recent data suggest that β-arrestins also contribute to GPCR signaling by acting as scaffolds for components of the ERK mitogen-activated protein kinase cascade. Because of these dual functions, we hypothesized that the stability of the receptor-β-arrestin interaction might affect the mechanism and functional consequences of GPCR-stimulated ERK activation. In transfected COS-7 cells, we found that angiotensin AT1a and vasopressin V2 receptors, which form stable receptor-β-arrestin complexes, activated a β-arrestin-bound pool of ERK2 more efficiently than α1b and β2 adrenergic receptors, which form transient receptor-β-arrestin complexes. We next studied chimeric receptors in which the pattern of β-arrestin binding was reversed by exchanging the C-terminal tails of the β2 and V2 receptors. The ability of the V2β2 and β2V2 chimeras to activate β-arrestin-bound ERK2 corresponded to the pattern of β-arrestin binding, suggesting that the stability of the receptor-β-arrestin complex determined the mechanism of ERK2 activation. Analysis of covalently cross-linked detergent lysates and cellular fractionation revealed that wild type V2 receptors generated a larger pool of cytosolic phospho-ERK1/2 and less nuclear phospho-ERK1/2 than the chimeric V2β2 receptor, consistent with the cytosolic retention of β-arrestin-bound ERK. In stably transfected HEK-293 cells, the V2β2 receptor increased ERK1/2-mediated, Elk-1-driven transcription of a luciferase reporter to a greater extent than the wild type V2 receptor. Furthermore, the V2β2, but not the V2 receptor, was capable of eliciting a mitogenic response. These data suggest that the C-terminal tail of a GPCR, by determining the stability of the receptor-β-arrestin complex, controls the extent of β-arrestin-bound ERK activation, and influences both the subcellular localization of activated ERK and the physiologic consequences of ERK activation.