Fig. 6.

GRK subtype specific regulation of β-arrestin 1 signaling. (A–D). Cells expressing either the wild-type (A) or S426A/S430A (C) receptors were cotransfected with control, GRK2, GRK3, GRK4, GRK5, or GRK6 siRNAs as described in Materials and Methods. After exposure to 1 μM WIN for 5 and 15 minutes, cells were lysed and the lysates were separated by SDS-PAGE and blotted with anti-phospho-ERK1/2 and anti-total ERK1/2 antibodies. Representative Western blot images are shown. Graphs provide the quantified levels of ERK1/2 phosphorylation for the wild-type (B) and S416/430A (D) receptors. The statistical significance of the differences compared with control was assessed using one-way analysis of variance and Bonferroni’s post hoc test. ***P < 0.001. (E) Representative Western blot bands demonstrates specific knockdown of GRKs endogenously expressed in HEK293 cells.