Positive regulation of the Egr-1/osteopontin positive feedback loop in rat vascular smooth muscle cells by TGF-beta, ERK, JNK, and p38 MAPK signaling

Biochem Biophys Res Commun. 2010 May 28;396(2):451-6. doi: 10.1016/j.bbrc.2010.04.115. Epub 2010 Apr 22.


Previous studies identified a positive feedback loop in rat vascular smooth muscle cells (VSMCs) in which early growth response factor-1 (Egr-1) binds to the osteopontin (OPN) promoter and upregulates OPN expression, and OPN upregulates Egr-1 expression via the extracellular signal-regulated protein kinase (ERK) signaling pathway. The current study examined whether transforming growth factor-beta (TGF-beta) activity contributes to Egr-1 binding to the OPN promoter, and whether other signaling pathways act downstream of OPN to regulate Egr-1 expression. ChIP assays using an anti-Egr-1 antibody showed that amplification of the OPN promoter sequence decreased in TGF-beta DNA enzyme-transfected VSMCs relative to control VSMCs. Treatment of VSMCs with PD98059 (ERK inhibitor), SP600125 (JNK inhibitor), or SB203580 (p38 MAPK inhibitor) significantly inhibited OPN-induced Egr-1 expression, and PD98059 treatment was associated with the most significant decrease in Egr-1 expression. OPN-stimulated VSMC cell migration was inhibited by SP600125 or SB203580, but not by PD98059. Furthermore, MTT assays showed that OPN-mediated cell proliferation was inhibited by PD98059, but not by SP600125 or SB203580. Taken together, the results of the current study show that Egr-1 binding to the OPN promoter is positively regulated by TGF-beta, and that the p38 MAPK, JNK, and ERK pathways are involved in OPN-mediated Egr-1 upregulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cells, Cultured
  • Early Growth Response Protein 1 / metabolism*
  • Extracellular Signal-Regulated MAP Kinases / antagonists & inhibitors
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Feedback, Physiological
  • Gene Expression Regulation*
  • MAP Kinase Kinase 4 / antagonists & inhibitors
  • MAP Kinase Kinase 4 / metabolism
  • Muscle, Smooth, Vascular / drug effects
  • Muscle, Smooth, Vascular / metabolism*
  • Myocytes, Smooth Muscle / drug effects
  • Myocytes, Smooth Muscle / metabolism*
  • Osteopontin / genetics*
  • Promoter Regions, Genetic
  • Protein Kinase Inhibitors / pharmacology
  • Rats
  • Signal Transduction
  • Transforming Growth Factor beta / metabolism*
  • p38 Mitogen-Activated Protein Kinases / antagonists & inhibitors
  • p38 Mitogen-Activated Protein Kinases / metabolism


  • Early Growth Response Protein 1
  • Egr1 protein, rat
  • Protein Kinase Inhibitors
  • Spp1 protein, rat
  • Transforming Growth Factor beta
  • Osteopontin
  • Extracellular Signal-Regulated MAP Kinases
  • p38 Mitogen-Activated Protein Kinases
  • MAP Kinase Kinase 4