It has been reported that β-arrestin is essential for the internalization of many G protein-coupled receptors. Since β 1 -adrenergic receptor (β 1 AR) shows the resistance to agonist-induced internalization, we examine the interaction of β-arrestin with β 1 AR with three different approaches: translocation of β-arrestin to the plasma membrane, direct binding of in vitro translated β-arrestin to intracellular domains of β 1 - and β 2 ARs, inhibition of β 1 - and β 2 AR-stimulated adenylyl cyclase activities by β-arrestin. The enhanced green fluorescent protein (EGFP)-tagged β-arrestin 2 (β-arrestin 2-GFP) translocates to and stays at the plasma membrane by β 2 AR stimulation. β-Arrestin 2-GFP also translocates to the plasma membrane upon β 1 AR stimulation. However, it returns to the cytoplasm 10 - 30 min after agonist stimulation. The amount of β-arrestin bound to the third intracellular loop and the carboxyl tail of β 1 AR is lower than that of β 2 AR. The fusion protein of β-arrestin 1 with glutathione-S-transferase inhibits the β 1 - and β 2 AR-stimulated adenylyl cyclase activities. However, inhibition of the β 1 AR-stimulated activity requires a higher amount of the fusion protein than that of the β 2 AR-stimulated activity. These results suggest that affinity of β 1 AR for β-arrestins is lower than that of β 2 AR, and explains the resistance to agonist-induced internalization. This conclusion is further supported by the finding that β-arrestin can induce internalization of β 1 AR when β-arrestin 1 fused to the carboxyl tail of β 1 AR.
All Science Journal Classification (ASJC) codes
- Biochemistry, Genetics and Molecular Biology(all)
- Pharmacology, Toxicology and Pharmaceutics(all)