beta-Arrestin 1 and 2 stabilize the angiotensin II type I receptor in distinct high-affinity conformations.
OBJECTIVE
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 beta-arrestins often induces higher binding affinity for agonists. Here, we examined interactions between AT(1A) receptors and beta-arrestins to look for differences between the AT(1A) receptor interaction with beta-arrestin1 and beta-arrestin2.


METHODS
Ligand-induced interaction between AT(1A) receptors and beta-arrestins was measured by Bioluminescence Resonance Energy Transfer 2. AT(1A)-beta-arrestin1 and AT(1A)-beta-arrestin2 fusion proteins were cloned and tested for differences using immunocytochemistry, inositol phosphate hydrolysis and competition radioligand binding.


RESULTS
Bioluminescence Resonance Energy Transfer 2 analysis showed that beta-arrestin1 and 2 were recruited to AT(1A) receptors with similar ligand potencies and efficacies. The AT(1A)-beta-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)-beta-arrestin2 than for AT(1A)-beta-arrestin1.


CONCLUSIONS
beta-Arrestin1 and 2 are recruited to AT(1A) receptors with similar ligand pharmacology and stabilize AT(1A) receptors in distinct high-affinity conformations. However, beta-arrestin2 induces a receptor conformation with a higher agonist-binding affinity than beta-arrestin1. Thus, this study demonstrates that beta-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 beta-arrestins selectively, would be possible to design.
Sanni
S J
SJ
Department of Clinical Biochemistry, Glostrup Hospital, Glostrup, Denmark.
Hansen
J T
JT
Bonde
M M
MM
Speerschneider
T
T
Christensen
G L
GL
Munk
S
S
Gammeltoft
S
S
Hansen
J L
JL
D000818:Animals; D019390:Arrestins / Q000145:classification / Q000378:metabolism*; D002460:Cell Line; D019204:GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D011487:Protein Conformation; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism*; D015398:Signal Transduction; D000071559:beta-Arrestin 1; D000071557:beta-Arrestins
C000605253:ARRB1 protein, human; D019390:Arrestins; D044140:Receptor, Angiotensin, Type 1; D000071559:beta-Arrestin 1; D000071557:beta-Arrestins; D019204:GTP-Binding Proteins