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

Abstract

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.

• Authors: T Hayashida, A C Poncelet, S C Hubchak, H W Schnaper
• Journal: Kidney international (Kidney Int) Vol. 56 Issue 5 Pg. 1710-20 (Nov 1999) ISSN: 0085-2538 [Print] United States
• PMID: 10571779 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• 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

Topics

• Cells, Cultured
• Collagen (biosynthesis)
• DNA-Binding Proteins (physiology)
• Enzyme Activation (drug effects)
• Glomerular Mesangium (drug effects, 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)