Figure 4.

Phosphorylation of CREB at serine-133 is not sufficient for 4xCRE transcription. a, Immunoblots were probed for phospho-CREB (top) and then stripped and reprobed for total CREB (bottom) to control for sample variability. Forskolin (F; 10 μm) stimulated CREB phosphorylation when compared with untreated (U) cells. CREB phosphorylation induced by forskolin was insensitive to addition of ifenprodil (F+I) or Bapta-AM (F+B). The effects of forskolin were abolished by incubation with the PKA inhibitor, H89 (10 μm) (data not shown). b, Quantification of CREB phosphorylation (P-CREB/CREB) from 4 experiments; ns, not significantly different from forskolin alone.