C Hh reporter activity assay in wild type and Grk2-/- 3T3 cells transfected with the equivalent wild type and mutant kinase domain forms of mouse Grk2, Grk2K220R, Grk2K220M and Grk2D335N after 24h Shh-N and SAG treatment. Data represent the mean and ± SD (n=3). Unpaired Students t-test was used for analysis. ****P<0.0001; **P<0.01; *P<0.05; and n.s. (not significant). 