Krüppel-like factor 4 promotes differentiation by transforming growth factor-beta receptor-mediated Smad and p38 MAPK signaling in vascular smooth muscle cells.
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.
Li
Hui-xuan
HX
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.
Han
Mei
M
Bernier
Michel
M
Zheng
Bin
B
Sun
Shao-guang
SG
Su
Ming
M
Zhang
Rui
R
Fu
Jian-ran
JR
Wen
Jin-kun
JK
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*
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