Figure 9.

S123A mutation of hCB₁R results in a selective decrease in the inhibitory potency of MRI-1891 against CB₁R-agonist-induced βArr2 recruitment (c) but not G protein activation (b), without causing a similar change in the effects of rimonabant (right panels) or affecting the binding affinity of either compound (a). GTPγS binding and βArr2 recruitment in CHO cells stably transfected with wild-type and S123A mutant hCB₁R were conducted using human CB₁ receptor cDNA (hCNR1, NM_016083) in the pCI vector (Promega) for GTPγS and radioligand binding assays, and in the pCMV-hCNR1-PK vector (Eurofins/DiscoverX) for β-arrestin-2 recruitment assays via the PathHunter system as described in the Supporting Information. Points and vertical bars represent mean ± SEM from 8 independent experiments. Numbers indicate K_d values calculated using computerized curve fitting and the Cheng–Prusoff equation.