Entropy drives the ligand recognition in G-protein-coupled receptor subtypes

Area of Science:

• Biochemistry
• Pharmacology
• Structural Biology

Background:

• G-protein-coupled receptors (GPCRs) are crucial drug targets.
• Achieving subtype selectivity in highly homologous GPCRs remains a significant challenge in drug discovery.
• The precise mechanisms governing ligand subtype selectivity are often poorly understood, hindering rational drug design.

Purpose of the Study:

• To elucidate the molecular mechanism of ligand recognition and subtype selectivity in cannabinoid receptor (CB) subtypes.
• To leverage this understanding for the rational design of subtype-selective ligands.
• To investigate the potential of entropy-driven selectivity for developing safer therapeutics.

Main Methods:

• Atomic-level molecular dynamics (MD) simulations.
• Cryoelectron microscopy (cryo-EM) structure determination.
• Mutagenesis experiments and ligand binding assays.

Main Results:

• An unusual entropy-driven molecular mechanism for ligand recognition in CB receptor subtypes was identified.
• Distinct conformational dynamics of the orthosteric pocket drive variations in ligand binding entropy and affinity.
• Experimentally validated mechanism enabled the design of ligands with enhanced/ablated subtype selectivity.
• A novel ligand demonstrated efficacy in pain models and lacked addictive properties in animal studies.

Conclusions:

• Entropy plays a critical, unconventional role in CB receptor subtype selectivity.
• The identified mechanism provides a strategy for rational design of entropy-driven, subtype-selective GPCR ligands.
• This approach holds promise for developing safer therapeutics with improved efficacy and reduced side effects.