Functional analysis of key residues involved in CB1 and CB2 activation.

Human endocannabinoid signaling is primarily mediated by the G-protein coupled receptors CB1 and CB2. These receptors have been linked to a variety of physiological processes and are being pursued as prospective drug candidates because of their potential to treat pain and inflammation. Due to their high sequence homology, as well as similarity in activation and signaling mechanism, investigating the physiological role of these receptors with selective ligands has been problematic. Ligands that selectively bind to CB2 may provide therapeutic benefits without the psychoactive effects associated with the CB1 receptor. Recent structural determination of the two receptors has allowed us to identify potential key residues involved in ligand binding. In the studies presented here, single point-mutations at the CB2 and CB1 receptor were developed and the receptor-mediated signaling of these mutants were evaluated. Using cannabinoid agonists AM841 and AM12033, we compared each mutation and observed that certain changes did not affect the activity of the receptor while others prevented or severely attenuated signaling. These results may provide a pathway for developing novel CB2 specific compounds with improved therapeutic potential.