Figure 7.

B-Raf activation by dopaminergic D₂ receptors. CHO cells transfected in 6-cm dishes were serum starved for 18 h and either left untreated or stimulated with 100 nM dopamine (DA) for 5 or 20 min. B-Raf activity was assayed as described in the legend to Figure 5. Data shown represent means ± SE of two independent experiments performed in duplicate. (A) Cells were transfected with 1.8 μg of dopaminergic D₂ receptor (D₂R), 1.8 μg of wild-type or activated Gα_i2 and Gα_i3 subunits, or 1.4 μg of Gβ₁ and Gγ₂ chains. *, Significantly higher than basal (p < 0.05 by unpaired t test). (B) Cells were transfected with 1.8 μg of D₂R and, where indicated, 1.8 μg of Gα_o-WT. *, Significantly higher than values obtained in the absence of Gα_o-WT (p < 0.01 by unpaired t test). (C) Cells were transfected with 1.4 μg of D₂R and, where indicated, 2.8 μg of N17-Ras. PMA pretreatment and incubation with wortmannin were as described in the legend to Figure 5. Results are expressed as percentages of the increase induced by DA in control cells.