FIGURE 6.

Wild type and mutant β₂ARs differentially couple to G_i proteins to regulate agonist-induced PKA FRET responses. A, the β₁β₂AR-KO cardiac myocytes expressing the PKA FRET biosensor AKAR2.2 together with the β₂AR, PKAmut β₂AR, or GRKmut β₂AR were stimulated with 10 μm Iso as indicated. The PKA FRET ratio was measured. B–D, myocytes were also treated with PTX to access the receptor/G_i coupling in regulating PKA FRET response after Iso stimulation. **, p < 0.01; ***, p < 0.001 when compared with the wild type receptor by two-way ANOVA. YFP, yellow fluorescent protein; CFP, cyan fluorescent protein.