Abstract

Reactive oxygen species (ROS) exert pleiotropic effects on a wide array of signaling proteins that regulate cellular growth and apoptosis. This study shows that long-term treatment with a low concentration of H₂O₂ leads to the activation of signaling pathways involving extracellular signal-regulated kinase, ribosomal protein S6 kinase, and protein kinase D (PKD) that increase cAMP binding response element protein (CREB) phosphorylation at Ser¹³³ in cardiomyocytes. Although CREB-Ser¹³³ phosphorylation typically mediates cAMP-dependent increases in CREB target gene expression, the H₂O₂-dependent increase in CREB-Ser¹³³ phosphorylation is accompanied by a decrease in CREB protein abundance and no change in Cre-luciferase reporter activity. Mutagenesis studies indicate that H₂O₂ decreases CREB protein abundance via a mechanism that does not require CREB-Ser¹³³ phosphorylation. Rather, the H₂O₂-dependent decrease in CREB protein is prevented by the proteasome inhibitor lactacystin, by inhibitors of mitogen-activated protein kinase kinase or protein kinase C activity, or by adenoviral-mediated delivery of a small interfering RNA that decreases PKD1 expression. A PKD1-dependent mechanism that links oxidative stress to decreased CREB protein abundance is predicted to contribute to the pathogenesis of heart failure by influencing cardiac growth and apoptosis responses.