The early-immediate gene EGR-1 is induced by transforming growth factor-β and mediates stimulation of collagen gene expression

被引:144
作者
Chen, Shu-Jen [1 ]
Ning, Hongyan [1 ]
Ishida, Wataru [1 ]
Sodin-Semrl, Snezna [1 ]
Takagawa, Shinsuke [1 ]
Mori, Yasuji [1 ]
Varga, John [1 ]
机构
[1] Northwestern Univ, Feinberg Sch Med, Div Rheumatol, Chicago, IL 60611 USA
关键词
D O I
10.1074/jbc.M603270200
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Transforming growth factor-beta (TGF-beta) stimulates collagen synthesis and accumulation, and aberrant TGF-beta signaling is implicated in pathological organ fibrosis. Regulation of type I procollagen gene (COL1A2) transcription by TGF-beta involves the canonical Smad signaling pathway as well as additional protein and lipid kinases, coactivators, and DNA-binding transcription factors that constitute alternate non-Smad pathways. By using Affymetrix microarrays to detect cellular genes whose expression is regulated by Smad3, we identified early growth response factor-1 (EGR-1) as a novel Smad3-inducible gene. Previous studies implicated Egr-1 in cell growth, differentiation, and survival. We found that TGF-beta induced rapid and transient accumulation of Egr-1 protein and mRNA in human skin fibroblasts. In transient transfection assays, TGF-beta stimulated the activity of the Egr-1 gene promoter, as well as that of a minimal Egr-1-responsive reporter construct. Furthermore, TGF-beta enhanced endogenous Egr-1 interaction with a consensus Egr-1-binding site element and with GC-rich DNA sequences of the human COL1A2 promoter in vitro and in vivo. Forced expression of Egr-1 by itself caused dose-dependent up-regulation of COL1A2 promoter activity and further enhanced the stimulation induced by TGF-beta. In contrast, the TGF-beta response was abrogated when the Egr-1-binding sites of the COL1A2 promoter were mutated or deleted. Furthermore, Egr-1-deficient embryonic mouse fibroblasts showed attenuated TGF-beta responses despite intact Smad activation, and forced expression of ectopic EGR-1 in these cells could restore COL1A2 stimulation in a dose-dependent manner. Taken together, these findings identify Egr-1 as a novel intracellular TGF-beta target that is necessary for maximal stimulation of collagen gene expression in fibroblasts. The results therefore implicate Egr-1 in the profibrotic responses elicited by TGF-beta and suggest that Egr-1 may play a new and important role in the pathogenesis of fibrosis.
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收藏
页码:21183 / 21197
页数:15
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