FIGURE 2.

D₂-A4-mediated arrestin3 recruitment. A, schematic of the BRET biosensor used to measure recruitment of arrestin to receptor. B, D₂-WT-Rluc8- and D₂-A4-Rluc8-mediated mVenus-Arr3 recruitment in response to incubation with quinpirole at the indicated concentrations for 10 min before measuring receptor/arrestin3 BRET. Values are expressed as the mean ± S.E. (error bars) of four independent experiments. C, maximal mVenus-Arr3 recruitment by D₂-A4-Rluc8 in response to quinpirole stimulation, expressed as a percentage of the activation by D₂-WT. Because a curve could not be fit to the data for D₂-A4, the BRET response in the presence of 100 μm quinpirole was used as the maximal response. ***, p < 0.001 compared with D₂-WT, Student's t test. Receptor density and the basal BRET for D₂-WT-Rluc8 were 569 ± 111 fmol/mg protein and 0.03 ± 0.005, and for D₂-A4 Rluc8, they were 722 ± 209 fmol/mg protein and 0.05 ± 0.016, respectively.