Peptidylarginine deiminases (PADs) are posttranslational modification
enzymes that citrullinate (deiminate)
protein arginine residues in a
calcium-dependent manner, yielding
citrulline residues. Enzymatic citrullination abolishes positive charges of native
protein molecules, inevitably causing significant alterations in their structure and function. Previously, we reported the abnormal accumulation of citrullinated
proteins and an increase of PAD2 content in hippocampi of patients with
Alzheimer disease. In this study, we investigated PAD expression by using dibutyryl cAMP (
dbcAMP) in human
astrocytoma U-251MG cells. Under normal culture conditions, PAD2 and PAD3
mRNA expression is detectable with quantitative PCR in U-251MG cells. The addition of
dbcAMP in a dose-dependent manner significantly increased this
mRNA expression and
protein levels. Moreover, PAD
enzyme activity also increased significantly and dose-dependently. Furthermore, the expression of PAD2 and PAD3
mRNA was inhibited by the cAMP-dependent
PKA inhibitor KT5720, suggesting that such expression of
dbcAMP-induced PAD2 and PAD3
mRNA is mediated by the cAMP-PKA signaling pathway in U-251MG cells. This is the first report to document the PAD2 and PAD3
mRNA expression induced by
dbcAMP and to attribute the induction of these genes to mediation by the cAMP-PKA signaling pathway in U-251MG cells. © 2016 Wiley Periodicals, Inc.