Structural Basis for Ligand Recognition and Functional Selectivity at Angiotensin Receptor.

Area of Science:

• Cardiovascular Pharmacology
• Structural Biology
• Molecular Endocrinology

Background:

• The Angiotensin II type 1 receptor (AT1R) is crucial for blood pressure regulation.
• Angiotensin II receptor blockers (ARBs) are widely used antihypertensives, but their structural binding basis is not fully understood.
• Understanding AT1R ligand interactions is key to developing more effective cardiovascular therapies.

Purpose of the Study:

• To determine the crystal structure of the human AT1R in complex with the ARB olmesartan.
• To elucidate the structural basis for AT1R modulation by diverse ligands.
• To investigate the role of specific receptor residues in ligand binding and signaling.

Main Methods:

• X-ray crystallography of human AT1R with olmesartan.
• Molecular docking simulations.
• Site-directed mutagenesis of AT1R.
• Analysis of ligand binding and receptor activity.

Main Results:

• The crystal structure of human AT1R complexed with olmesartan was determined, revealing key anchoring residues (Tyr-35, Trp-84, Arg-167).
• A common binding mode for different ARBs was corroborated, suggesting shared interaction principles.
• Mutagenesis identified specific AT1R-ARB interactions and highlighted the role of the N111(3.35)A mutation in modulating angiotensin II binding but not β-arrestin-biased signaling.

Conclusions:

• The study provides the first crystal structure of human AT1R with an inverse agonist, olmesartan.
• Structural insights reveal common binding modes for ARBs, aiding in the design of novel antihypertensives.
• Specific receptor residues and their interactions dictate ligand efficacy and signaling bias.