Fig. 4. (A) Effect of kinase pathway inhibitors on CREB-dependent luciferase activity in L929 (black) and mtDNA-depleted (hatched) cells. After transfection, cells were incubated for 16 h before the assay with 50 µM KN-93, 50 µM W-7, 10 µM H-89, 20 µM PD 95089, 1 µM calphostin C or 1 µM wortmannin. (B) L929 (black) and mtDNA-depleted L929 (hatched) cells were transiently co-transfected with a plasmid encoding β-galactosidase, the CREB luciferase reporter construct driven by the α-inhibin promoter and an expression vector encoding wild-type CaMKIV or the dominant-negative form CaMKIV T200A. (C) Effect of overexpression of CaMKI, CaMKII and CaMKIV on the activation of the CREB luciferase reporter construct driven by the α-inhibin promoter. L929 (black) and mtDNA-depleted L929 (hatched) cells were transiently co-transfected as described in (B) with an expression vector encoding wild-type CaMKI, II or IV. Results are normalized for β-galactosidase activity, are expressed in fold increase of luciferase activity of the L929 control cells and represent the mean ± SD for n = 3 (***, significantly different from L929 with P <0.001; ###, significantly different from mtDNA-depleted L929 cells with P <0.001).