Angiotensin receptor conformations stabilized by biased ligands differentially modulate β-arrestin interactions

Area of Science:

• Pharmacology
• Biochemistry
• Structural Biology

Background:

• Biased ligands for the angiotensin II type 1 receptor (AT1R) selectively activate G protein or beta-arrestin signaling pathways by stabilizing distinct receptor conformations.
• Understanding how these ligands interact with beta-arrestin is crucial for developing targeted therapies.

Purpose of the Study:

• To investigate the varying abilities of beta-arrestin-biased AT1R ligands to stabilize different modes of beta-arrestin interaction.
• To elucidate the structural basis for differential beta-arrestin engagement with the AT1R.

Main Methods:

• Biochemical assays
• Double electron-electron resonance (DEER) spectroscopy
• Integrative modeling

Main Results:

• AT1R ligands demonstrated differential stabilization of beta-arrestin interactions with the receptor's seven-transmembrane core versus its phosphorylated C-terminus.
• Ligands less effective at stabilizing the core complex induced an AT1R conformation incompatible with beta-arrestin core binding.
• This suggests that allosteric effects of ligands can directly modulate beta-arrestin activities through distinct binding modes.

Conclusions:

• The study reveals "intra-transducer bias," where ligands can preferentially activate specific beta-arrestin functions.
• This nuanced control over beta-arrestin signaling offers potential for more precise GPCR drug pharmacology.
• Findings highlight the importance of considering ligand-specific interactions with different receptor domains for drug design.