FIGURE 3.

Effect of GRK2 RH domain mutant (D110A) or GRK2 RH domain fragment on D₂ DAR-mediated inhibition of cAMP accumulation. DA inhibition of cAMP accumulation was measured using intact HEK293T cells transiently expressing WT D₂ DAR along with pcDNA, GRK2, GRK2-D110A (A), or GRK2-(45–185) (B). Cells were incubated with various concentrations of DA for 10 min in the presence of 3 μm forskolin. cAMP accumulation was then assessed as described under “Experimental Procedures.” The data shown represent the mean ± S.E. values from at least three experiments and are expressed as a percentage of forskolin-stimulated cAMP accumulation in the absence of DA. The average estimated IC₅₀ parameters (mean ± S.E.) with GRK2-D110A or GRK2-(45–185) expression are 6.1 ± 2.9 and 13.6 ± 1.5 nm, respectively. The control and GRK2 (WT) data are replicated from Fig. 1 for comparative purposes.