Novel Regulation of CREB Activation by Reactive Oxygen Species in B Lymphocytes

Abstract

cAMP Responsive Element Binding protein (CREB) is a transcription factor that promotes expression of genes involved in cell growth and survival. Signaling via reactive oxygen species (ROS) has been reported to attenuate CREB activity by phosphorylation of CREB at the inhibitory site serine‐121. However, ROS signaling has also been reported to enhance CREB activity via phosphorylation at the positive regulatory site serine‐133. We investigated the effects of ROS on CREB activity in murine B lymphocyte cells and observed that hydrogen peroxide induced CREB phosphorylation at ser‐133. Menadione, a superoxide inducer, also promoted CREB phosphorylation at ser‐133. In contrast to our prediction, we observed that peroxide did not induce ser‐121 phosphorylation but rather suppressed ser‐121 phosphorylation. Menadione treatment, however, did not exhibit this marked suppression of ser‐121 phosphorylation. ATM, a kinase activated by DNA damage and ROS, has been previously reported to mediate CREB phosphorylation at ser‐121 in other cell types, and we observed a similar role for ATM in B cells. Intriguingly, we also observed that U0126, an inhibitor of the MEK‐ERK pathway, also suppressed ser‐121 phosphorylation of CREB. Our data therefore illustrate novel mechanisms of CREB regulation in B lymphocytes and suggest that different species of ROS can mediate distinct effects on CREB activation.