Allosteric Interactions Between the Type 1 (CB1) and Type 2 (CB2) Cannabinoid Receptors Modify β-Arrestin2 Recruitment
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Type 1 (CB1) and Type 2 (CB2) Cannabinoid receptors form heteromers with unique pharmacology compared to CB1 or CB2 alone. We wanted to determine if the Tango β- arrestin2 luc reporter assay could measure heteromer-dependant allosteric modulation of β-arrestin2 recruitment to CB1 and CB2 following non-selective agonism with CP 55,940 and antagonism using AM251 or AM630. We determined that the Tango assay could detect allostery between CB1 and CB2, but the sensitivity of this assay depended on the transfection reagent being used. CP 55,940 agonism in cells expressing CB1 and CB2 resulted in ~25% less β-arrestin2 recruitment to both CB1 and CB2, and these differences were dependant on receptor stoichiometry. Antagonism of CB1 or CB2 increased CP 55,940-induced β-arrestin2 recruitment to the heteromer partner. Thus, the CB1/CB2 heteromer negatively modulates β-arrestin2 recruitment following non-selective agonism, and positively modulates β-arrestin2 recruitment following antagonism with AM251 or AM630.