title: Smad3 and extracellular signal-regulated kinase 1/2 coordinately mediate transforming growth factor-beta-induced expression of connective tissue growth factor in human fibroblasts.
abstract: Connective tissue growth factor (CTGF) is secreted by fibroblasts stimulated with transforming growth factor-beta (TGF-beta). CTGF is a potent enhancer of fibroblast proliferation, chemotaxis, and extracellular matrix deposition, and it is thought to mediate some of the fibrogenic effects of TGF-beta. Here, we have elucidated signaling pathways involved in regulating the TGF-beta-induced production of CTGF in primary fibroblasts. TGF-beta induced the expression of CTGF messenger RNA and protein in human gingival fibroblasts after 2 h of treatment. Adenoviral overexpression of Smad3 enhanced the TGF-beta-elicited expression of CTGF, whereas Smad7 and dominant-negative Smad3 suppressed the effects of TGF-beta on CTGF and Cyr61 expression. Pre-treatment of cells with PD98059, an inhibitor for extracellular signal-regulated kinase (ERK)1/2-activator mitogen-activated protein kinase (MAPK)/ERK kinase (MEK)1, potently inhibited the TGF-beta-induced expression of CTGF. Furthermore, co-expression of Smad3 with constitutively active MEK1 resulted in potent induction of CTGF production without exogenous TGF-beta stimulation. Together, these results demonstrate that Smad3 and ERK1/2 coordinately mediate TGF-beta-induced release of CTGF by fibroblasts. It is conceivable that the crosstalk between Smad3 and ERK1/2 signaling cascades plays an important role in regulating CTGF expression, e.g., in wound repair and tissue fibrosis and could be exploited in therapeutic targeting of fibrotic conditions.
authors.affiliation: Department of Medical Biochemistry and Molecular Biology, University of Turku, Turku, Finland.
authors.forename: Suvi-Katri
authors.initials: SK
authors.lastname: Leivonen
authors.forename: Lari
authors.initials: L
authors.lastname: Häkkinen
authors.forename: David
authors.initials: D
authors.lastname: Liu
authors.forename: Veli-Matti
authors.initials: VM
authors.lastname: Kähäri
mesh_terms: D002478:Cells, Cultured; D055513:Connective Tissue Growth Factor; D004268:DNA-Binding Proteins / Q000502:physiology*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D005881:Gingiva / Q000166:cytology; D006801:Humans; D017874:Immediate-Early Proteins / Q000096:biosynthesis / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis / Q000378:metabolism*; D048369:MAP Kinase Kinase 1 / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3 / Q000502:physiology*; D011994:Recombinant Proteins / Q000494:pharmacology; D051900:Smad3 Protein; D015534:Trans-Activators / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
chemical_list: C526317:CCN2 protein, human; D004268:DNA-Binding Proteins; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D011994:Recombinant Proteins; C497790:SMAD3 protein, human; D051900:Smad3 Protein; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D055513:Connective Tissue Growth Factor; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human