Multi-faceted roles of β-arrestins in G protein-coupled receptors endocytosis

Abstract

Internalization plays a crucial role in regulating the density of cell surface receptors and has been demonstrated to regulate intracellular signaling. Dysregulation of this process has been implicated in various diseases. The vast majority of GPCRs were considered to adopt one way for internalization. We challenged this conventional view by showing that multiple pathways converge to regulate the internalization of a specific receptor, based on an unparalleled characterization of 60 GPCR internalization profiles, both in the absence and presence of individual βarrestins (βarrs). Furthermore, we revealed the internalization mechanism of the glucagon-like peptide-1 receptor (GLP-1R), a class B GPCR pivotal in promoting insulin secretion from pancreatic beta cells to maintain glucose homeostasis. GLP-1R can undergo agonist-induced internalization without βarrs, but can recruit and form stable complexes with βarrs. We found that GLP-1R recruits clathrin adaptor protein-2 for agonist-induced internalization in both βarr-dependent and -independent manners. These results provide a valuable resource for GPCR signaling and reveal the plasticity of different GPCRs to employ or not βarrs in the clathrin-mediated internalization.