Figure 6.

IGF receptor activation and Akt activity promote GRK2 stabilization. (A) Turnover of endogenous GRK2 was analyzed in MCF7 cells as detailed in Materials and methods in the presence of 50 ng/ml of IGF-1 or vehicle. Labeled proteins were immunoprecipitated with a specific anti-GRK2 antibody (C5/1.1). The density of the ³⁵S-labeled GRK2 band after the pulse period was taken as 100%. Data are mean±s.e.m. of 3–5 independent experiments. ^*P<0.05; ^**P<0.01. A representative fluorography is shown. (B) HEK-293 cells were transfected with different combinations of GRK2, Mdm2 and a constitutively active Akt mutant (Akt-myr) as indicated. GRK2 degradation rate was determined by pulse–chase analysis. Results (mean±s.e.m.) from three independent experiments are shown. ^*P<0.05.