FIGURE 8.

ERK5 is involved in up-regulation of tyrosine hydroxylase protein in PC12 cells. A, PC12 cells were co-transfected with tyrosine hydroxylase promoter/luciferase and β-galactosidase and empty vector (Vec), ERK5KD, MEK5D, or MEK5A. Two days after transfection, the cells were pretreated with or without U0126 (30 μm) for 30 min and incubated with NGF (100 ng/ml) or Bt₂cAMP (dbcAMP) (0.5 mm) for 6 h. Tyrosine hydroxylase gene promoter activity was expressed as the fold over the control (no drug). Values represent the means ± S.E. (n = 3). NGF and Bt₂cAMP significantly increased the promoter activity (*, p < 0.05), and U0126 abolished the promoter activity (#, p < 0.05). B, PC12 cells were transfected with empty vector, ERK5KD (KD), or MEK5A (MA). Two days after the transfection, the cells were pretreated with or without U0126 (30 μm) for 30 min and incubated with NGF (100 ng/ml) or Bt₂cAMP (0.5 mm) for 24 h. Then tyrosine hydroxylase and ERK1/2 were examined by Western blotting.