Pairing of forskolin and KCl increases differentiation of immortalized hippocampal neurons in a CREB Serine 133 phosphorylation-dependent and extracellular-regulated protein kinase-independent manner

Although cAMP response element binding protein (CREB)- and extracellular-re gulated protein kinase (ERK)-mediated pathways have been linked to each oth er in neuronal differentiation, involvement of these in hippocampal neurona l cell line has not been defined. Using an immortalized hippocampal cell li ne, HiB5, we have tried a pairing of forskolin with KCl depolarization, whi ch acts as an ERK and CREB kinase activator in hippocampal neurons, to inve stigate if an activation of ERK and phosphorylation of CREB at the critical regulatory site, serine 133 might be coupled in differentiation. Different iation toward a neuronal phenotype was synergistically and markedly increas ed by the pairing of forskolin and KCl depolarization. The synergistic effe ct was accompanied by an increase in phosphorylation of CREB Ser-133, but n ot phosphorylation of ERK, and was not inhibited by MEK inhibitor, PD98059. These findings indicate that phosphorylation of the transcriptional factor CREB may function to facilitate differentiation of HiB5 cells. (C) 2001 El sevier Science Ireland Ltd. All rights reserved.