Figure 2.

Effect of siRNA-mediated β-arrestin depletion on cAMP accumulation by endogenously expressed β₂-AR. HEK293 cells were transfected with the indicated RNA oligonucleotides as described and subsequently stimulated with 10 μM isoproterenol for 2 min. Accumulation of cAMP was determined by competition with [³H]cAMP for PKA binding sites and then normalized to total forskolin (10 μM)-stimulated cAMP levels for each treatment. Data are expressed as percent of agonist-induced cAMP accumulation in control RNA-treated (CTL) cells and represent the mean ± SE of six independent experiments. NS, nonstimulated. Statistical significance was determined by using a one-way ANOVA to correct for multiple comparisons between β-arrestin siRNA-transfected cells and control cells. The asterisk indicates P < 0.05 vs. both control RNA- and mock (No RNA)-transfected cells.