Single-molecule force spectroscopy study of interactions between angiotensin II type 1 receptor and different biased ligands in living cells
Abstract
Angiotensin II type 1 receptor (AT1R), a typical G protein-coupled receptor, plays a key role in regulating many cardiovascular functions. Different ligands can bind with AT1R to selectively activate either G protein (Gq) or β-arrestin (β-arr) pathway, or both pathways, but the molecular mechanism is not clear yet. In this work, we used, for the first time, atomic force microscopy-based single molecule force spectroscopy (SMFS) to study the interactions of AT1R with three types of ligands, balanced ligand, Gq-biased ligand, and β-arr-biased ligand, in living cells. The results revealed their difference in binding force and binding stability. The complex of the Gq-biased ligand-AT1R overcame two energy barriers with an intermediate state during dissociation, whereas that of β-arr-biased ligand-AT1R complex overcame one energy barrier. This indicated that AT1R had different ligand-binding conformational substates and underwent different structural changes to activate downstream signaling pathways with variable agonist efficacies. Quantitative analysis of AT1R-ligand binding in living cells at the single-molecule level offers a new tool to study the molecular mechanism of AT1R biased activation. Graphical Abstract Single-molecule ...Continue Reading
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