title: Krüppel-like factor 4 promotes differentiation by transforming growth factor-beta receptor-mediated Smad and p38 MAPK signaling in vascular smooth muscle cells.
abstract: KLF4 (Krüppel-like factor 4) has been implicated in vascular smooth muscle cell (VSMC) differentiation induced by transforming growth factor beta (TGF-beta). However, the role of KLF4 and mechanism of KLF4 actions in regulating TGF-beta signaling in VSMCs remain unclear. In this study, we showed that TGF-beta1 inhibited cell cycle progression and induced differentiation in cultured rat VSMCs. This activity of TGF-beta1 was accompanied by up-regulation of KLF4, with concomitant increase in TbetaRI (TGF-beta type I receptor) expression. KLF4 was found to transduce TGF-beta1 signals via phosphorylation-mediated activation of Smad2, Smad3, and p38 MAPK. The activation of both pathways, in turn, increased the phosphorylation of KLF4, which enabled the formation of KLF4-Smad2 complex in response to TGF-beta1. Chromatin immunoprecipitation studies and oligonucleotide pull-down assays showed the direct binding of KLF4 to the KLF4-binding sites 2 and 3 of the TbetaRI promoter and the recruitment of Smad2 to the Smad-responsive region. Formation of a stable KLF4-Smad2 complex in the promoter's Smad-responsive region mediated cooperative TbetaRI promoter transcription in response to TGF-beta1. These results suggest that KLF4-dependent regulation of Smad and p38 MAPK signaling via TbetaRI requires prior phosphorylation of KLF4 through Smad and p38 MAPK pathways. This study demonstrates a novel mechanism by which TGF-beta1 regulates VSMC differentiation.
authors.affiliation: Department of Biochemistry and Molecular Biology, Key Laboratory of Neural and Vascular Biology, China Ministry of Education, Hebei Medical University, No 361, Zhongshan East Road, Shijiazhuang 050017, China.
authors.forename: Hui-xuan
authors.initials: HX
authors.lastname: Li
authors.forename: Mei
authors.initials: M
authors.lastname: Han
authors.forename: Michel
authors.initials: M
authors.lastname: Bernier
authors.forename: Bin
authors.initials: B
authors.lastname: Zheng
authors.forename: Shao-guang
authors.initials: SG
authors.lastname: Sun
authors.forename: Ming
authors.initials: M
authors.lastname: Su
authors.forename: Rui
authors.initials: R
authors.lastname: Zhang
authors.forename: Jian-ran
authors.initials: JR
authors.lastname: Fu
authors.forename: Jin-kun
authors.initials: JK
authors.lastname: Wen
mesh_terms: D000818:Animals; D001665:Binding Sites; D002454:Cell Differentiation; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors / Q000378:metabolism*; D008297:Male; D008954:Models, Biological; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D051381:Rats; D017207:Rats, Sprague-Dawley; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism*; D015398:Signal Transduction; D051785:Smad Proteins / Q000378:metabolism*; D014158:Transcription, Genetic; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: C000715469:Klf4 protein, rat; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; D018125:Receptors, Transforming Growth Factor beta; D051785:Smad Proteins; D048051:p38 Mitogen-Activated Protein Kinases