Hocevar B A, Brown T L, Howe P H
Department of Cell Biology, The Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195, USA.
EMBO J. 1999 Mar 1;18(5):1345-56. doi: 10.1093/emboj/18.5.1345.
Transforming growth factor-beta (TGF-beta) exerts its effects on cell proliferation, differentiation and migration in part through its modulation of extracellular matrix components, such as fibronectin and plasminogen activator inhibitor-1 (PAI-1). Although the SMAD family of proteins recently has been shown to be a key participant in TGF-beta signaling, other signaling pathways have also been shown to be activated by TGF-beta. We report here that c-Jun N-terminal kinase (JNK), a member of the MAP kinase family, is activated in response to TGF-beta in the human fibrosarcoma HT1080-derived cell line BAHgpt. Stable expression of dominant-negative forms of JNK1 and MKK4, an upstream activator of JNK, results in loss of TGF-beta-stimulated fibronectin mRNA and protein induction, while having little effect on TGF-beta-induced levels of PAI-1. The human fibronectin promoter contains three CRE elements, one of which has been shown to bind a c-Jun-ATF-2 heterodimer. Utilizing a GAL4 fusion trans-reporting system, we demonstrate a decrease in transactivating potential of GAL4-c-Jun and GAL4-ATF-2 in dominant-negative JNK1- and MKK4-expressing cells. Finally, we show that TGF-beta-induced fibronectin synthesis is independent of Smad4. These results demonstrate that TGF-beta-mediated fibronectin induction requires activation of JNK which in turn modulates the activity of c-Jun and ATF-2 in a Smad4independent manner.
转化生长因子-β（TGF-β）部分通过调节细胞外基质成分（如纤连蛋白和纤溶酶原激活物抑制剂-1，PAI-1）来发挥其对细胞增殖、分化和迁移的作用。尽管最近已证明SMAD蛋白家族是TGF-β信号传导的关键参与者，但其他信号通路也已被证明可被TGF-β激活。我们在此报告，丝裂原活化蛋白激酶（MAPK）家族成员c-Jun氨基末端激酶（JNK）在人纤维肉瘤HT1080衍生的细胞系BAHgpt中对TGF-β产生反应而被激活。JNK1和JNK的上游激活剂MKK4的显性负性形式的稳定表达导致TGF-β刺激的纤连蛋白mRNA和蛋白质诱导的丧失，而对TGF-β诱导的PAI-1水平影响很小。人纤连蛋白启动子包含三个CRE元件，其中一个已被证明可结合c-Jun-ATF-2异二聚体。利用GAL4融合反式报告系统，我们证明在表达显性负性JNK1和MKK4的细胞中，GAL4-c-Jun和GAL4-ATF-2的反式激活潜力降低。最后，我们表明TGF-β诱导的纤连蛋白合成独立于Smad4。这些结果表明，TGF-β介导的纤连蛋白诱导需要JNK的激活，而JNK又以Smad4独立的方式调节c-Jun和ATF-2的活性。
