Figure 5.

GRK2 turnover is blocked in Mdm2-deficient cells. (A) Mdm2-null MEFs were transfected with wild-type GRK2 in the presence or absence of Mdm2. Degradation of the heterologous GRK2 protein was assessed after 1 h of chase as in previous figures. (B) Stability of endogenous GRK2 is increased in the absence of Mdm2 expression. GRK2 protein levels were examined by immunoblot analysis in both wild-type and Mdm2-deficient MEFs upon treatment with cycloheximide (CHX) for the indicated times. The amount of GRK2 at 0 h was defined as 100%, and data normalized by actin protein levels. In both the panels, data are the mean±s.e.m. of four independent experiments (^*P<0.05, ^**P<0.01). Representative gels are shown.