Unique Roles of β-Arrestin in GPCR Trafficking Revealed by Photoinducible Dimerizers

Intracellular trafficking of G protein-coupled receptors (GPCRs) controls their localization and degradation, which affects a cell's ability to adapt to extracellular stimuli. Although the perturbation of trafficking induces important diseases, these trafficking mechanisms are poorly understood. Herein, we demonstrate an optogenetic method using an optical dimerizer, cryptochrome (CRY) and its partner protein (CIB), to analyze the trafficking mechanisms of GPCRs and their regulatory proteins. Temporally controlling the interaction between beta-arrestin and beta 2-adrenergic receptor (ADRB2) reveals that the duration of the beta-arrestin-ADRB2 interaction determines the trafficking pathway of ADRB2. Remarkably, the phosphorylation of ADRB2 by G protein-coupled receptor kinases is unnecessary to trigger clathrin-mediated endocytosis, and beta-arrestin interacting with unphosphorylated ADRB2 fails to activate mitogen-activated protein kinase (MAPK) signaling, in contrast to the ADRB2 agonist isoproterenol. Temporal control of beta-arrestin-GPCR interactions will enable the investigation of the unique roles of beta-arrestin and the mechanism by which it regulates beta-arrestin-specific trafficking pathways of different GPCRs.