TGF-beta1 activates MAP kinase in human mesangial cells: a possible role in collagen expression

Kidney Int. 1999 Nov;56(5):1710-20. doi: 10.1046/j.1523-1755.1999.00733.x.


Background: Although the pathogenic relevance of transforming growth factor-beta (TGF-beta) to glomerular sclerosis has been established, the intracellular mechanisms by which TGF-beta induces extracellular matrix accumulation are not fully understood. We examined whether the mitogen-activated protein (MAP) kinase pathway is involved in TGF-beta1-induced collagen expression by cultured human mesangial cells.

Methods: The activation of MAP kinase pathways by TGF-beta1 was assessed by immunoblot with anti-phospho-ERK or -JNK antibodies and by transfection of plasmids expressing pathway-specific transcription activators fused to the DNA-binding domain of GAL4, as well as a GAL4 response element-luciferase reporter gene. The role of MAP kinase was assessed using biochemical inhibitors and transiently expressed dominant negative mutant constructs. The effects on TGF-beta1-induced alpha1(I) collagen expression were evaluated by Northern blot and by activation of a transiently transfected alpha1(I) promoter-luciferase reporter construct.

Results: ERK and JNK phosphorylation occurred 30 minutes and one hour, respectively, after TGF-beta1 treatment. A biochemical blockade of the ERK pathway inhibited TGF-beta1-induced alpha1(I) collagen expression. A dominant negative mutant of ERK1 but not of JNK decreased alpha1(I) gene promoter activation. Activation of the TGF-beta-responsive p3TP-Lux construct was partially inhibited by cotransfection of an ERK1 dominant negative mutant.

Conclusion: These data indicate that MAP kinase pathways can be activated by TGF-beta1 in mesangial cells and that the ERK MAP kinase plays a role in TGF-beta-stimulated collagen I expression. Because we have shown previously that SMADs mediate TGF-beta1-stimulated collagen I expression, our findings raise the possibility of interactions between the MAP kinase and the SMAD pathways.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cells, Cultured
  • Collagen / biosynthesis*
  • DNA-Binding Proteins / physiology
  • Enzyme Activation / drug effects
  • Glomerular Mesangium / drug effects
  • Glomerular Mesangium / metabolism*
  • Humans
  • JNK Mitogen-Activated Protein Kinases*
  • MAP Kinase Kinase 4
  • Mitogen-Activated Protein Kinase Kinases / physiology
  • Mitogen-Activated Protein Kinases / metabolism*
  • Smad Proteins
  • Trans-Activators / physiology
  • Transforming Growth Factor beta / pharmacology*


  • DNA-Binding Proteins
  • Smad Proteins
  • Trans-Activators
  • Transforming Growth Factor beta
  • Collagen
  • JNK Mitogen-Activated Protein Kinases
  • Mitogen-Activated Protein Kinases
  • MAP Kinase Kinase 4
  • Mitogen-Activated Protein Kinase Kinases