Low affinity of beta(1)-adrenergic receptor for beta-arrestins explains the resistance to agonist-induced internalization

It has been reported that beta -arrestin is essential for the internalizati on of many G protein-coupled receptors. Since beta (1)-adrenergic receptor (beta (1)AR) shows the resistance to agonist-induced internalization, we ex amine the interaction of beta -arrestin with beta (1)AR with three differen t approaches: translocation of p-arrestin to the plasma membrane, direct bi nding of in vitro translated beta -arrestin to intracellular domains of bet a (1)- and beta (2)ARs, inhibition of beta (1)- and beta (2)AR-stimulated a denylyl cyclase activities by beta -arrestin. The enhanced green fluorescen t protein (EGFP)-tagged beta -arrestin 2 (beta -arrestin 2-GFP) translocate s to and stays at the plasma membrane by beta (2)AR stimulation. beta -Arre stin 2-GFP also translocates to the plasma membrane upon beta (1)AR stimula tion. However, it returns to the cytoplasm 10 - 30 min after agonist stimul ation. The amount of beta -arrestin bound to the third intracellular loop a nd the carboxyl tail of beta (1)AR is lower than that of beta (2)AR. The fu sion protein of beta -arrestin 1 with glutathione-S-transferase inhibits th e beta (1)- and beta (2)AR-stimulated adenylyl cyclase activities. However, inhibition of the beta (1)AR-stimulated activity requires a higher amount of the fusion protein than that of the beta (2)AR-stimulated activity. Thes e results suggest that affinity of beta (1)AR for beta -arrestins is lower than that of beta (2)AR, and explains the resistance to agonist-induced int ernalization. This conclusion is further supported by the finding that beta -arrestin can induce internalization of beta (1)AR when beta -arrestin 1 f used to the carboxyl tail of beta (1)AR. (C) 2001 Elsevier Science Inc. All rights reserved.