Figure 1. Insulin induces GRK2 membrane translocation and GRK-mediated phosphorylation of β₂AR.

(A) Mouse heart lysates were subjected to immunoprecipitation with anti-IR antibody. (B) WT MEF cells were lysed for immunoprecipitation with either an anti-IR antibody or an anti-GRK2 antibody upon insulin stimulation (100 nM, 10 min). Immunoprecipitated proteins were detected by Western blot. Data represent at least three independent experiments. (C) H9c2 cardiac myoblasts overexpressed β₂AR were stimulated with insulin (100 nM, 10 min). Membrane fractions were blotted for GRK2, IR, β₂AR, and G_i. The protein levels on the plasma membrane were normalized to those of G_i. * p < 0.05 by student t-test relative to control group ( n = 3). (D–G) H9c2 cardiac myoblasts were infected with adenovirus expressing mouse β₂AR and then stimulated with insulin for 10 min at indicated doses (D and F) or with 100 nM insulin for indicated times (E and G). The levels of phosphorylation of β₂AR at serine 261/262 and 355/356 were detected by western blot, and normalized against total β₂AR (n = 5). * p < 0.05 and ** p < 0.01 by one-way ANOVA in relative to control followed by Tukey’s test.