Biased Agonists of the Type 1 Angiotensin II Receptor Promote Distinct Subcellular β-Arrestin Conformations

Area of Science:

• Pharmacology
• Cellular Biology
• Biochemistry

Background:

• G protein-coupled receptors (GPCRs) are key drug targets involved in cellular signaling.
• Biased agonism describes how ligands can selectively activate specific signaling pathways of a GPCR.
• Location bias indicates that the same ligand-receptor complex can produce different signaling profiles in distinct subcellular compartments.

Purpose of the Study:

• To investigate how biased agonists affect β-arrestin recruitment and conformation at different subcellular locations for the angiotensin II type 1 receptor.
• To determine the impact of ligand bias on ERK activation across various cellular compartments.

Main Methods:

• Utilized split luciferase and Bioluminescence Resonance Energy Transfer (BRET) assays to monitor β-arrestin recruitment and conformational states.
• Examined receptor-β-arrestin complexes at the plasma membrane, early endosomes, and the receptor itself.
• Quantified ERK activation in the nucleus, cytosol, early endosomes, and plasma membrane.

Main Results:

• Angiotensin II and its G protein-biased analogs promoted a core complex conformation of receptor-β-arrestin.
• β-arrestin-biased analogs favored a tail complex configuration of receptor-associated β-arrestins.
• G protein-biased ligands induced greater ERK activation in subcellular locations compared to β-arrestin-biased ligands, with equal ERK activity at the plasma membrane.

Conclusions:

• Ligand bias dictates distinct β-arrestin conformations at the receptor level but not the plasma membrane.
• Location bias significantly influences ERK activation patterns, with G protein-biased ligands showing enhanced signaling in intracellular compartments.
• Findings elucidate the complex interplay between ligand bias and subcellular location in determining GPCR signaling outcomes.