Essential Dynamics of CB1 Receptor-Agonist Complexes: Implications for Signalling Bias
The CB1 cannabinoid receptor is implicated in a broad range of physiological processes and disease states, however CB1-targeting drugs in clinical use remain based on tetrahydrocannabinol (THC). Ligands that exhibit functional selectivity for different intracellular signalling pathways are currently an area of rapid development, and hold significant potential as therapeutic agents. Improved understanding of the exact molecular mechanisms underpinning biased activation of intracellular effector proteins for CB1 is necessary to enable drug development of biased CB1 ligands into candidates for treatment of human disease. Using molecular dynamics, this study shows that CB1 conformations resulting from activation by the orthosteric ligands CP55940, {Delta}9-THC or 5F-MDMB-PICA exhibit differences in the dynamic organisation of key residues and receptor substructures involved in coupling to G proteins and {beta}-arrestins, that leads to selective activation of downstream signalling pathways. The identification of conformationally distinct CB1-agonist complexes that demonstrate different functional profiles provides an important step in unravelling the molecular determinants for biased signalling, and lays a platform for future rational design of novel therapeutic leads.