Characterizing Cannabinoid CB2 Receptor Ligands Using DiscoveRx PathHunter (TM) beta-Arrestin Assay

The authors have characterized a set of cannabinoid CB2 receptor ligands, including triaryl bis sulfone inverse agonists, in a cell-based receptor/beta-arrestin interaction assay (DiscoveRx PathHunter (TM)). The results were compared with results using a competitive ligand binding assay, and with effects on forskolin-stimulated cAMP levels (PerkinElmer LANCE (TM)). The authors show good correlation between the 3 assay systems tested, with the beta-arrestin protein complementation assay exhibiting a more robust signal than the cAMP assay for cannabinoid CB2 agonists. Further assay validation shows that DiscoveRx PathHunter (TM) HEK293 CB2 beta-arrestin assay can be carried out from cryopreserved cell suspensions, eliminating variations caused by the need for multiple cell pools during live cell screening campaigns. These results, and the authors' results evaluating a test set of random library compounds, validate the use of ligand-induced interaction between the human cannabinoid CB2 receptor and beta-arrestin as an appropriate and valuable screening platform for compounds specific for the cannabinoid CB2 receptor. (Journal of Biomolecular Screening 2009:49-58)