Plasminogen activator inhibitor-1 is a transcriptional target of the canonical pathway of Wnt/beta-catenin signaling.
Plasminogen activator inhibitor-1 (PAI-1) is a multifunctional glycoprotein that plays a critical role in the pathogenesis of chronic kidney and cardiovascular diseases. Although transforming growth factor (TGF)-beta1 is a known inducer of PAI-1, how it controls PAI-1 expression remains enigmatic. Here we investigated the mechanism underlying TGF-beta1 regulation of PAI-1 in kidney tubular epithelial cells (HKC-8). Surprisingly, overexpression of Smad2 or Smad3 in HKC-8 cells blocked PAI-1 induction by TGF-beta1, whereas knockdown of them sensitized the cells to TGF-beta1 stimulation, suggesting that Smad signaling is not responsible for PAI-1 induction. Blockade of several TGF-beta1 downstream pathways such as p38 MAPK or JNK, but not phosphatidylinositol 3-kinase/Akt and ERK1/2, only partially inhibited PAI-1 expression. TGF-beta1 stimulated beta-catenin activation in tubular epithelial cells, and ectopic expression of beta-catenin induced PAI-1 expression, whereas inhibition of beta-catenin abolished its induction. A functional T cell factor/lymphoid enhancer-binding factor-binding site was identified in the promoter region of the PAI-1 gene, which interacted with T cell factor upon beta-catenin activation. Deletion or site-directed mutation of this site abolished PAI-1 response to beta-catenin or TGF-beta1 stimulation. Similarly, ectopic expression of Wnt1 also activated PAI-1 expression and promoter activity. In vivo, PAI-1 was induced in kidney tubular epithelia in obstructive nephropathy. Delivery of Wnt1 gene activated beta-catenin and promoted PAI-1 expression after obstructive injury, whereas blockade of Wnt/beta-catenin signaling by Dickkopf-1 gene inhibited PAI-1 induction. Collectively, these studies identify PAI-1 as a direct downstream target of Wnt/beta-catenin signaling and demonstrate that PAI-1 induction could play a role in mediating the fibrogenic action of this signaling.
He
Weichun
W
Department of Medicine, The First Affiliated Hospital, Nanjing Medical University, Nanjing 210029, China.
Tan
Ruoyun
R
Dai
Chunsun
C
Li
Yingjian
Y
Wang
Dan
D
Hao
Sha
S
Kahn
Michael
M
Liu
Youhua
Y
D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D006801:Humans; D007684:Kidney Tubules / Q000166:cytology; D020935:MAP Kinase Signaling System; D008297:Male; D051379:Mice; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism*; D015398:Signal Transduction; D014158:Transcription, Genetic; D016212:Transforming Growth Factor beta / Q000378:metabolism; D051153:Wnt Proteins / Q000378:metabolism; D051176:beta Catenin / Q000378:metabolism*
D017395:Plasminogen Activator Inhibitor 1; D016212:Transforming Growth Factor beta; D051153:Wnt Proteins; D051176:beta Catenin