Structural basis of efficacy-driven ligand selectivity at GPCRs.

Area of Science:

• Pharmacology
• Molecular Biology
• Computational Chemistry

Background:

• Drug selectivity is crucial for therapeutic efficacy, yet challenging to achieve between closely related receptors.
• Efficacy-driven selectivity, where ligands preferentially activate certain receptors despite similar binding affinities, offers a potential solution but lacks a clear molecular mechanism.
• Understanding this mechanism is vital for designing novel therapeutics targeting G-protein-coupled receptors (GPCRs).

Purpose of the Study:

• To elucidate the structural basis of efficacy-driven selectivity for xanomeline between muscarinic acetylcholine receptors (mAChRs).
• To experimentally validate the proposed mechanism.
• To guide the rational design of new ligands with tailored selectivity profiles.

Main Methods:

• All-atom molecular dynamics simulations to model ligand-receptor interactions.
• Biochemical assays to validate simulation findings and assess receptor activation.
• Structure-based drug design to create novel ligands with modified selectivity.

Main Results:

• Xanomeline exhibits similar binding modes in inactive mAChRs but distinct interactions in active states.
• These differences in active-state binding lead to divergent effects on receptor stability, explaining efficacy-driven selectivity.
• Experimental validation confirmed the simulation-derived mechanism, and newly designed ligands demonstrated altered selectivity profiles.

Conclusions:

• The study reveals the atomic-level mechanism underlying efficacy-driven selectivity in mAChRs.
• This understanding facilitates the rational design of selective ligands for pharmaceutically important GPCRs.
• The findings provide a framework for developing safer and more effective drugs by enhancing target selectivity.