Krüppel-like factor 4 inhibits proliferation by platelet-derived growth factor receptor beta-mediated, not by retinoic acid receptor alpha-mediated, phosphatidylinositol 3-kinase and ERK signaling in vascular smooth muscle cells.
Proliferation inhibition of vascular smooth muscle cells (VSMCs) is governed by the activity of a transcription factor network. Krüppel-like factor 4 (Klf4), retinoic acid receptor (RAR alpha), and platelet-derived growth factor receptor (PDGFR) are expressed in VSMCs and are components of such a network. However, the relationship among them in the regulation of VSMC proliferation remains unknown. Here, we investigated the mechanisms whereby Klf4 mediates the growth inhibitory effects in VSMCs through RAR alpha and PDGFR beta. We demonstrated that Klf4 directly binds to the 5' regulatory region of RAR alpha, down-regulates RAR alpha expression, and specifically inhibits RAR alpha-mediated phosphatidylinositol 3-kinase (PI3K) and ERK signaling in cultured VSMCs induced by the synthetic retinoid Am80. Of particular interest, Klf4 inhibits RAR alpha and PDGFR beta expression while blocking PI3K and ERK signaling induced by Am80 and PDGF-BB, respectively. The anti-proliferative effects of Klf4 on neointimal formation depend largely on PDGFR-mediated PI3K signaling without involvement of the RAR alpha-activated signaling pathways. These findings provide a novel mechanism for signal suppression and growth inhibitory effects of Klf4 in VSMCs. Moreover, the results of this study suggest that Klf4 is one of the key mediators of retinoid actions in VSMCs.
Zheng
Bin
B
Department of Biochemistry and Molecular Biology, Hebei Medical University, Zhongshan East Road, Shijiazhuang 050017, China.
Han
Mei
M
Bernier
Michel
M
Zhang
Xin-hua
XH
Meng
Fang
F
Miao
Sui-bing
SB
He
Ming
M
Zhao
Xin-ming
XM
Wen
Jin-kun
JK
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D049109:Cell Proliferation; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000502:physiology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D016297:Mutagenesis, Site-Directed; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D051381:Rats; D017207:Rats, Sprague-Dawley; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D018168:Receptors, Retinoic Acid / Q000378:metabolism*; D000072482:Retinoic Acid Receptor alpha; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology
D048049:Extracellular Signal-Regulated MAP Kinases; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; D019869:Phosphatidylinositol 3-Kinases; D020797:Receptor, Platelet-Derived Growth Factor beta; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; C000715467:KLF4 protein, human; C000715469:Klf4 protein, rat; C000607071:RARA protein, human; C000607073:Rara protein, rat