Fig. 4.

Agonist-induced translocation of arrestin3 in HEK 293 cells co-expressing arrestin3 and wild-type or mutant D₃ receptors. Cells transiently transfected with arrestin3 and wild-type D₃ receptor (WT) or D₃-C147K (K147) were treated with 10 μM dopamine (DA) or vehicle (CTL) for 20 min, membranes were prepared, and levels of arrestin3 were determined by quantitative immunoblotting. Results were quantified using standard curves constructed with known amounts of purified arrestin3. A representative arrestin3 immunoblot is shown for the cytosolic fraction (supernatant) and the membrane fraction (pellet) from one of three independent experiments. The results from the supernatant demonstrate approximately equal expression of arrestin3 in all four conditions. The amount of arrestin in the membrane fractions from all three experiments is shown in the bar graph as the mean ± S.E.M. (*, p < 0.05 compared with vehicle-treated cells).