The comparative role of activator protein 1 and Smad factors in the regulation of Timp-1 and MMP-1 gene expression by transforming growth factor-beta 1.
The balance between matrix metalloproteinases (MMPs) and their inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), is pivotal in the remodeling of extracellular matrix. TGF-beta has profound effects on extracellular matrix homeostasis, in part via its ability to alter this balance at the level of gene expression. The intracellular signaling pathways by which TGF-beta mediates its actions include the Smad pathway, specific to the TGF-beta superfamily, but also, for example, mitogen-activated protein kinase pathways; furthermore, cross-talk between the Smads and other signaling pathways modifies the TGF-beta response. The reciprocal effect of TGF-beta on the expression of Timp-1 and MMP-1 supports its role in matrix anabolism, yet the mechanisms by which TGF-beta induces Timp-1 and represses induced MMP-1 have remained opaque. Here, we (i) investigate the mechanism(s) by which TGF-beta1 induces expression of the Timp-1 gene and (ii) compare this with TGF-beta1 repression of phorbol ester-induced MMP-1 expression. We report that the promoter-proximal activator protein 1 (AP1) site is essential for the response of both Timp-1 and MMP-1 to TGF-beta (induction and repression, respectively). c-Fos, JunD, and c-Jun are essential for the induction of Timp-1 gene expression by TGF-beta1, but these AP1 factors transactivate equally well from both Timp-1 and MMP-1 AP1 sites. Smad-containing complexes do not interact with the Timp-1 AP1 site, and overexpression of Smads does not substitute or potentiate the induction of the gene by TGF-beta1; furthermore, Timp-1 is still induced by TGF-beta1 in Smad knockout cell lines, although to varying extents. In contrast, Smads do interact with the MMP-1 AP1 site and mediate repression of induced MMP-1 gene expression by TGF-beta1.
Hall
Marie-Claire
MC
School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom.
Young
David A
DA
Waters
Jasmine G
JG
Rowan
Andrew D
AD
Chantry
Andrew
A
Edwards
Dylan R
DR
Clark
Ian M
IM
D000818:Animals; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000502:physiology*; D005786:Gene Expression Regulation; D020781:Matrix Metalloproteinase 1 / Q000235:genetics*; D051379:Mice; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D051899:Smad2 Protein; D051900:Smad3 Protein; D051901:Smad4 Protein; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000235:genetics*; D015534:Trans-Activators / Q000502:physiology*; D018808:Transcription Factor AP-1 / Q000502:physiology*; D015533:Transcriptional Activation; D016212:Transforming Growth Factor beta / Q000502:physiology*; D053773:Transforming Growth Factor beta1
D004268:DNA-Binding Proteins; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; D051901:Smad4 Protein; C490810:Smad4 protein, mouse; C508961:Tgfb1 protein, mouse; D019715:Tissue Inhibitor of Metalloproteinase-1; D015534:Trans-Activators; D018808:Transcription Factor AP-1; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D020781:Matrix Metalloproteinase 1; D013755:Tetradecanoylphorbol Acetate