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.七跨膜受体/G蛋白偶联受体（G protein-coupled receptors, GPCRs）的信号转导受到多种受体互作蛋白的调控，其中包括β抑制蛋白（βarrestins, βarrs）与G蛋白偶联受体激酶（GPCR kinases, GRKs）。在本研究中，我们借助生物发光共振能量转移实验（bioluminescence resonance energy transfer assays）分析了胰高血糖素样肽-1（glucagon-like peptide-1, GLP-1）受体（GLP-1R）、βarr2与GRK2之间的相互作用模式。结果显示，βarr2以双相模式与GLP-1R发生相互作用，包含不依赖磷酸化与依赖磷酸化两个组分。在竞争实验中，我们观测到βarr2可与GRK2竞争结合GLP-1R。我们提出如下模型：βarr2可与GRK2竞争结合活化且经GRK磷酸化的GLP-1R，这提示βarr2在调控GRK2功能的协同运作中具有全新的生物学作用。