Plasminogen Activator Inhibitor-1 Is a Transcriptional Target of the Canonical Pathway of Wnt/β-Catenin Signaling
Plasminogen Activator Inhibitor-1 Is a Transcriptional Target of the Canonical Pathway of Wnt/β-Catenin Signaling
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DOI：
10.1074/jbc.m109.091256
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发表时间：
2010-08-06
影响因子：
4.8
通讯作者：
Liu, Youhua
中科院分区：
文献类型：
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作者：
He, Weichun;Tan, Ruoyun;Liu, Youhua
纤溶酶原激活物抑制剂-1（派-1）是一种多功能糖蛋白，在慢性肾脏和心血管疾病的发病机制中起着关键作用。虽然转化生长因子（TGF）-β 1是已知的派-1诱导剂，但其如何控制派-1表达仍是个谜。在此，我们研究了肾小管上皮细胞（HKC-8）中TGF-β 1调节派-1的潜在机制。令人惊讶的是，Smad 2或Smad 3在HKC-8细胞中的过表达阻断了TGF-β 1对派-1的诱导，而它们的敲低使细胞对TGF-β 1的刺激敏感，这表明Smad信号传导不负责派-1的诱导。阻断几种TGF-β 1下游途径如p38 MAPK或JNK，但不阻断磷脂酰肌醇3-激酶/Akt和ERK 1/2，仅部分抑制派-1表达。TGF-β 1刺激肾小管上皮细胞中β-连环蛋白的活化，并且β-连环蛋白的异位表达诱导派-1的表达，而抑制β-连环蛋白则消除其诱导。一个功能性T细胞因子/淋巴增强子结合因子结合位点被确定在派-1基因的启动子区，其与T细胞因子β-连环蛋白激活后相互作用。该位点的缺失或定点突变消除了派-1对β-连环蛋白或TGF-β 1刺激的反应。类似地，Wnt 1的异位表达也激活派-1表达和启动子活性。在体内，派-1在梗阻性肾病的肾小管上皮细胞中被诱导。Wnt 1基因激活β-catenin并促进阻塞性损伤后派-1的表达，而Dick-kopf-1基因阻断Wnt/β-catenin信号通路则抑制派-1的诱导。总的来说，这些研究将派-1鉴定为Wnt/β-连环蛋白信号传导的直接下游靶标，并证明派-1诱导可以在介导该信号传导的纤维化作用中发挥作用。
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)-beta 1 is a known inducer of PAI-1, how it controls PAI-1 expression remains enigmatic. Here we investigated the mechanism underlying TGF-beta 1 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-beta 1, whereas knockdown of them sensitized the cells to TGF-beta 1 stimulation, suggesting that Smad signaling is not responsible for PAI-1 induction. Blockade of several TGF-beta 1 downstream pathways such as p38 MAPK or JNK, but not phosphatidylinositol 3-kinase/Akt and ERK1/2, only partially inhibited PAI-1 expression. TGF-beta 1 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-beta 1 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 Dick-kopf-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.