Structural basis for selectivity and diversity in angiotensin II receptors

Area of Science:

• Biochemistry
• Structural Biology
• Pharmacology

Background:

• Angiotensin II receptors (AT1R and AT2R) are crucial in the renin-angiotensin-aldosterone system.
• AT1R regulates blood pressure, while AT2R's function remains largely unknown with diverse reported effects.

Purpose of the Study:

• To elucidate the structural mechanisms behind the functional and ligand selectivity differences between AT1R and AT2R.
• To understand the structural basis for AT2R's unique signaling profile.

Main Methods:

• X-ray crystallography of human AT2R bound to selective and dual ligands.
• Structure-activity relationship (SAR) studies.
• Molecular docking and mutagenesis analyses.

Main Results:

• Crystal structures revealed AT2R in an active-like conformation with a non-canonical helix VIII position.
• This unique helix VIII conformation stabilizes the receptor but hinders G protein and β-arrestin recruitment, explaining the lack of signaling.
• SAR, docking, and mutagenesis identified key interactions governing ligand binding and selectivity.

Conclusions:

• The study provides the structural basis for the distinct functions of AT1R and AT2R.
• Findings offer insights into AT2R's signaling mechanism and can inform the development of novel selective ligands for therapeutic applications.