Oxidative Modification of Nuclear Mitogen-activated Protein Kinase Phosphatase 1 Is Involved in Transforming Growth Factor β1-induced Expression of Plasminogen Activator Inhibitor 1 in Fibroblasts

• Published in: The Journal of biological chemistry 2010-05, Vol.285 (21), p.16239-16247
• Main Authors: Liu, Rui-Ming, Choi, Jinah, Wu, Jian-He, Gaston Pravia, Kimberly A., Lewis, Karen M., Brand, Jeffrey D., Mochel, N.S. Reyes, Krzywanski, David M., Lambeth, J. David, Hagood, James S., Forman, Henry Jay, Thannickal, Victor J., Postlethwait, Edward M.
• Format: Article
• Language: English
• Subjects: Fibroblast; Gene Regulation; MAP kinases (MAPKs); MAPK Phosphatase 1; NADPH Oxidase; Oxygen Radicals; Plasminogen Activator Inhibitor 1; Signal Transduction; Transforming Growth Factor β (TGF-β)
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M110.111732

Transforming growth factor β (TGF-β) stimulates reactive oxygen species (ROS) production in various cell types, which mediates many of the effects of TGF-β. The molecular mechanisms whereby TGF-β increases ROS production and ROS modulate the signaling processes of TGF-β, however, remain poorly defined. In this study, we show that TGF-β1 stimulates NADPH oxidase 4 (Nox4) expression and ROS generation in the nucleus of murine embryo fibroblasts (NIH3T3 cells). This is associated with an increase in protein thiol modification and inactivation of MAPK phosphatase 1 (MKP-1), a nuclear phosphatase. Furthermore, knockdown of MKP-1 using small interfering RNA enhances TGF-β1-induced phosphorylation of JNK and p38 as well as the expression of plasminogen activator inhibitor 1 (PAI-1), a TGF-β-responsive gene involved in the pathogenesis of many diseases. Knockdown of Nox4 with Nox4 small interfering RNA, on the other hand, reduces TGF-β1-stimulated ROS production, p38 phosphorylation, and PAI-1 expression. TGF-β also increased the nuclear level of Nox4 protein as well as PAI-1 expression in human lung fibroblasts (CCL-210 cells), suggesting that TGF-β may induce PAI-1 expression by a similar mechanism in human lung fibroblasts. In summary, in this study we have identified nuclear MAPK phosphatase MKP-1 as a novel molecular target of ROS in TGF-β signaling pathways. Our data suggest that increased generation of ROS by Nox4 mediates TGF-β1-induced PAI-1 gene expression at least in part through oxidative modification and inhibition of MKP-1 leading to a sustained activation of JNK and p38 MAPKs.