MKP-7, a negative regulator of JNK, regulates VCAM-1 expression through IRF-1

• Published in: Cellular signalling 2012-04, Vol.24 (4), p.866-872
• Main Authors: Nizamutdinova, Irina Tsoy, Kim, Young Min, Lee, Jae Heun, Chang, Ki Churl, Kim, Hye Jung
• Format: Article
• Language: English
• Subjects: Chromatin Immunoprecipitation; Dual-Specificity Phosphatases - genetics; Dual-Specificity Phosphatases - metabolism; GATA6; GATA6 Transcription Factor - genetics; GATA6 Transcription Factor - metabolism; Gene Expression Regulation; Genes, Reporter; Human Umbilical Vein Endothelial Cells; Humans; ICAM-1; Interferon Regulatory Factor-1 - genetics; Interferon Regulatory Factor-1 - metabolism; IRF-1; JNK; Luciferases; MAP Kinase Kinase 4 - antagonists & inhibitors; MAP Kinase Kinase 4 - genetics; MAP Kinase Kinase 4 - metabolism; Mitogen-Activated Protein Kinase Phosphatases - genetics; Mitogen-Activated Protein Kinase Phosphatases - metabolism; MKP-7; Plasmids; Protein Kinase Inhibitors - pharmacology; Signal Transduction - genetics; Transfection; Tumor Necrosis Factor-alpha - genetics; Tumor Necrosis Factor-alpha - metabolism; Vascular Cell Adhesion Molecule-1 - genetics; Vascular Cell Adhesion Molecule-1 - metabolism; VCAM-1
• ISSN: 0898-6568; 1873-3913
• DOI: 10.1016/j.cellsig.2011.12.002

Cell adhesion molecules (CAMs) are involved in a variety of pathologies including cancer, inflammation, pathogenic infections and autoimmune disease. In particular, VCAM-1, rather than ICAM-1, plays a major role in the initiation of atherosclerosis and tumor progression. Therefore, we attempted to elucidate differential mechanisms that regulate VCAM-1 and ICAM-1 expressions. Down-regulation of JNK by a specific inhibitor (SP600125) or dominant negative (DN) JNK1 plasmid enhanced TNF-α-induced VCAM-1 but not ICAM-1 expression. Moreover, transfection with a JNK1-overexpressing vector resulted in the inhibition of VCAM-1 expression stimulated by TNF-α in HUVECs, suggesting that JNK negatively regulates TNF-α-induced VCAM-1 expression in endothelial cells (ECs). Next, we investigated whether JNK signaling affects IRF-1 and/or GATA6, which are transcription factors that mediate TNF-α induction of VCAM-1 but not ICAM-1. The DN-JNK1 plasmid-transfected cells enhanced TNF-α up-regulation of IRF-1 whereas JNK1-overexpressing cells displayed down-regulation; however, neither DN-JNK1 transfection nor JNK1 overexpression affected GATA6 protein levels in the nuclear fraction. Chromatin immunoprecipitation (ChIP) assay confirmed that the inhibition of JNK by DN-JNK1 transfection increases the binding of IRF-1 to the VCAM-1 promoter whereas the overexpression of JNK1 inhibits IRF-1 binding to the VCAM-1 promoter. However, neither DN-JNK1 nor JNK1 overexpression altered GATA6 affinity for the VCAM-1 promoter region. We also examined whether MKP-7 affects ICAM-1 or VCAM-1 by regulating JNK. TNF-α-induced phosphor-JNK levels increased after 5min, peaked at 10min, and decreased after 30min. Interestingly, MKP-7 protein levels increased after 30min, when phosphor-JNK induction by TNF-α was decreased. In addition, silencing MKP-7 with specific siRNA resulted in an increase in phosphor-JNK and inhibited the expression of VCAM-1 but not ICAM-1. Moreover, silencing MKP-7 caused the down-regulation of IRF-1 protein levels and binding to the VCAM-1 promoter. Thus, we suggest that MKP-7, a negative regulator of JNK, regulates VCAM-1 expression in activated endothelial cells through IRF-1 but not GATA6. ► VCAM-1, rather than ICAM-1, plays a major role in the initiation of atherosclerosis and tumor progression. ► The existence of IRF-1 and GATA functional transcription factor binding motifs in the VCAM-1 gene promoter region distinguishes VCAM-1 from other CAMs. ► We discovered that s