Figure 8. Effect of GRK6 overexpression on the D2R-dependent G protein-mediated signaling and βarrestin 2 recruitment.

8A, In cells transfected with EPAC sensor and D₂R, cAMP level was monitored for 25 minutes. Cells were pretreated with quinpirole at 10 μM and then cAMP production was stimulated by forskolin at 3 μM. In wild type cells quinpirole decreased forskolin effect by about 50% (p<0.05), while in GRK6 overexpressing cells it had no significant effect. 8B, βarrestin 2 recruitment was evaluated by coexpression of D₂-Rluc and βarrestin 2-YFP. Cells were stimulated with quinpirole at 10 μM and then BRET ratio was monitored for 25 minutes. Quinpirole was able to induce an increase in BRET ratio. Coexpression of GRK6 produced a significant increase in delta-BRET (p<0.05). All values are expressed as means ± SEM (n = 4 independent experiments for each experimental condition).