Figure 5.

Synergistic effect of forskolin (FSK) and PMA on CREB phosphorylation. Cultured 4B cells were incubated for 30 min with increasing concentrations of forskolin in the presence and absence of 1 μm PMA. Data points are the mean and se of the values obtained by Western blot using an antibody against phospho Ser133-CREB in six experiments. The larger-scale representation of the low forskolin concentrations is depicted in the inset. Two-way ANOVA revealed marked increases in Ser133-phospho-CREB with PMA alone and a potentiation of the stimulatory effect of low concentrations of forskolin on CREB phosphorylation. *, P < 0.05 vs. forskolin alone; **, P < 0.01 vs. basal or forskolin alone. TFIIB, Transcription factor IIB.