Stimulation of pro-α1(I) collagen by TGF-β1 in mesangial cells: Role of the p38 MAPK pathway

Beek Yoke Chin, Amir Mohsenin, Su Xia Li, Augustine M.K. Choi, Mary E. Choi

Research output: Contribution to journalArticle

127 Scopus citations

Abstract

Transforming growth factor-β1 (TGF-β1 is a potent inducer of extracellular matrix protein synthesis and a key mediator of renal fibrosis. However, the intracellular signaling mechanisms by which TGF-β1 stimulates this process remain incompletely understood. In this report, we examined the role of a major stress -activated intracellular signaling cascade, belonging to the mitogen-activated protein kinase (MAPK) superfamily, in mediating TGF-β1 responses in rat glomerular mesangial cells, using dominant-negative inhibition of TGF-β1 signaling receptors. We first stably transfected rat glomerular mesangial cells with a kinase-deleted mutant TGF-β1 type II receptor (TβR-IIM) designed to inhibit TGF-β1 signaling in a dominant-negative fashion. Next, expression of TβR-IIM mRNA was confirmed by Northern analysis. Cell surface expression and ligand binding of TβR-IIM protein were demonstrated by affinity cross-linking with 125I-labeled-TGF-β1. TGF-β1 rapidly induced p38 MAPK phosphorylation in wild-type and empty vector (pcDNA3)-transfected control mesangial cells. Interestingly, transfection with dominant-negative TβR-IIM failed to block TGF-β1-induced p38 MAPK phosphorylation. Moreover, dominant-negative TβR-IIM failed to block TGF-β1-stimulated pro-α1(I) collagen mRNA expression and cellular protein synthesis, whereas TGF-β1-induced extracellular signal-regulated kinase (ERK) 1/ERK2 activation and antiproliferative responses were blocked by TβR-IIM. In the presence of a specific inhibitor of p38 MAPK, SB-203580, TGF-β1 was unable to stimulate pro-α2I) collagen mRNA expression in the control and TβR-IIM-transfected mesangial cells. Finally, we confirmed that both p38 MAPK activation and pro-α1(I) collagen stimulation were TGF-β1 effects that were abrogated by dominant-negative inhibition of TGF-β type I receptor. Thus we show first demonstration of p38 MAPK activation by TGF-β2 in mesangial cells, and, given the rapid kinetics, this TGF-β1 effect is likely a direct one. Furthermore, our findings suggest that the p38 MAPK pathway functions as a component in the signaling of pro-α1(I) collagen induction by TGF-β2 in mesangial cells.

Original languageEnglish (US)
Pages (from-to)F495-F504
JournalAmerican Journal of Physiology - Renal Physiology
Volume280
Issue number3 49-3
DOIs
StatePublished - 2001

Keywords

  • Matrix
  • Mitogen-activated protein kinase
  • Signal transduction
  • Transforming growth factor-β receptor

ASJC Scopus subject areas

  • Physiology
  • Urology

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