Distinct activation mechanisms regulate subtype selectivity of Cannabinoid receptors

Area of Science:

• Molecular Pharmacology
• Computational Chemistry
• Biophysics

Background:

• Cannabinoid receptors CB1 and CB2 share high sequence and structural similarity, complicating the design of subtype-selective ligands.
• Understanding the molecular basis of ligand selectivity is crucial for developing targeted therapeutics.

Purpose of the Study:

• To investigate the hypothesis that subtype selectivity arises from ligands binding to distinct conformational states of CB1 and CB2 receptors.
• To elucidate the activation mechanisms of CB1 and CB2 receptors and identify key differences influencing ligand binding.

Main Methods:

• Utilized approximately 700 microseconds of unbiased molecular dynamics simulations.
• Employed Markov state models and VAMPnets to analyze receptor activation pathways.
• Performed structural and dynamic comparisons of metastable intermediate states and docking analyses.

Main Results:

• Identified similarities and distinctions in the activation mechanisms of CB1 and CB2 receptors.
• Observed differences in binding pocket volume changes during receptor activation.
• Docking revealed that CB1 exhibits high affinity only in specific intermediate states, while CB2 shows consistent affinity across its states for CB2-selective agonists.

Conclusions:

• The distinct activation mechanisms and conformational states of CB1 and CB2 receptors mechanistically explain the subtype selectivity of designed agonists.
• Deciphering these activation dynamics provides a foundation for rational drug design targeting specific cannabinoid receptor subtypes.