Fig. 8. Impaired degradation of the GRK2 Y13/86/92F tyrosine phosphorylation mutant. HEK-293 cells were transiently transfected with β₂AR and GRK2 or GRK2 Y13/86/92F in the absence [(A) and ‘minus’ in (B)] or presence [`plus' in (B)] of isoproterenol (ISO), followed by analysis of the remaining ³⁵S-labeled GRK2 proteins as in Figure 1. Data in all panels are the mean ± SE of three independent experiments performed in duplicate.