Article date: September 2010
By: SJ Sanni, JT Hansen, MM Bonde, T Speerschneider, GL Christensen, S Munk, S Gammeltoft, JL Hansen in Volume 161, Issue 1, pages 150-161
BACKGROUND AND PURPOSE The angiotensin II type 1 (AT1) 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 AT1A receptors and β‐arrestins to look for differences between the AT1A receptor interaction with β‐arrestin1 and β‐arrestin2.
EXPERIMENTAL APPROACH Ligand‐induced interaction between AT1A receptors and β‐arrestins was measured by Bioluminescence Resonance Energy Transfer 2. AT1A‐β‐arrestin1 and AT1A‐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 AT1A receptors with similar ligand potencies and efficacies. The AT1A‐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 AT1A‐β‐arrestin2 than for AT1A‐β‐arrestin1.
CONCLUSION AND IMPLICATIONS β‐Arrestin1 and 2 are recruited to AT1A receptors with similar ligand pharmacology and stabilize AT1A 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 AT1A receptors in different ways and suggest that AT1 receptor biased agonists with the ability to recruit either of the β‐arrestins selectively, would be possible to design.
DOI: 10.1111/j.1476-5381.2010.00875.x
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