Supplementary Material for: Beta-Arrestin2 as a Competitor for GRK2 Interaction with the GLP-1 Receptor upon Receptor Activation

The signaling of seven transmembrane receptors/G-protein- coupled receptors (GPCRs) is regulated by a number of receptor interacting proteins, including βarrestins (βarrs) and GPCR kinases (GRKs). In the present report, we have analyzed the interaction pattern between the glucagon-like peptide-1 (GLP-1) receptor (GLP-1R), βarr2, and GRK2 using bioluminescence resonance energy transfer assays. We found that βarr2 interacts with the GLP-1R in a biphasic manner with a phosphorylation-independent and a phosphorylation-dependent component. In competition experiments, we observed βarr2 competing with GRK2 for interaction with GLP-1R. We propose a model were βarr2 competes with GRK2 for interaction with the activated and GRK phosphorylated GLP-1R, suggesting a new role of βarr2 in regulating the orchestration of GRK2 functionality.