β-Arrestin 1 and 2 stabilize the angiotensin II type i receptor in distinct high-affinity conformations

Background and Purpose The angiotensin II type 1 (AT ₁) receptor belongs to family A of 7 transmembrane (7TM) receptors. The receptor has important roles in the cardiovascular system and is commonly used as a drug target in cardiovascular diseases. Interaction of 7TM receptors with G proteins or β-arrestins often induces higher binding affinity for agonists. Here, we examined interactions between AT _1A receptors and β-arrestins to look for differences between the AT _1A receptor interaction with β-arrestin1 and β-arrestin2. Experimental Approach Ligand-induced interaction between AT _1A receptors and β-arrestins was measured by Bioluminescence Resonance Energy Transfer 2. AT _1A-β-arrestin1 and AT _1A-β-arrestin2 fusion proteins were cloned and tested for differences using immunocytochemistry, inositol phosphate hydrolysis and competition radioligand binding. Key Results Bioluminescence Resonance Energy Transfer 2 analysis showed that β-arrestin1 and 2 were recruited to AT _1A receptors with similar ligand potencies and efficacies. The AT _1A-β-arrestin fusion proteins showed attenuated G protein signalling and increased agonist binding affinity, while antagonist affinity was unchanged. Importantly, larger agonist affinity shifts were observed for AT _1A-β-arrestin2 than for AT _1A-β-arrestin1. CONCLUSION AND IMPLICATIONS β-Arrestin1 and 2 are recruited to AT _1A receptors with similar ligand pharmacology and stabilize AT _1A receptors in distinct high-affinity conformations. However, β-arrestin2 induces a receptor conformation with a higher agonist-binding affinity than β-arrestin1. Thus, this study demonstrates that β-arrestins interact with AT _1A receptors in different ways and suggest that AT ₁ receptor biased agonists with the ability to recruit either of the β-arrestins selectively, would be possible to design.