Regulation of biglycan gene expression by transforming growth factor-β requires MKK6-p38 mitogen-activated protein kinase signaling downstream of smad signaling
Regulation of biglycan gene expression by transforming growth factor-β requires MKK6-p38 mitogen-activated protein kinase signaling downstream of smad signaling
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DOI：
10.1074/jbc.m300035200
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发表时间：
2003-03-28
影响因子：
4.8
通讯作者：
Kalthoff, H
中科院分区：
文献类型：
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作者：
Ungefroren, H;Lenschow, W;Kalthoff, H
几种信号传导途径已涉及介导TGF-β 1诱导的细胞外基质产生和纤维化。我们最近已经表明，TGF-β 1诱导双糖链蛋白聚糖（BGN）表达依赖于功能性Smad途径（Chen，W. B.，Lenschow，W.，Tiede，K.，Fischer，J.W.，Kalthoff，H.，和Ungefroren，H.（2002）J.Biol.Chem.277，36118 -36128）。在这里，我们提供的证据表明，TGF-β 1诱导BGN mRNA的能力，除了Smads，需要p38 MAPK信号，因为1）p38的药理学抑制剂剂量依赖性地抑制TGF-β效应，而不显著影响TGF-β I型受体的组成型活性突变体的转录活性或Smad 2磷酸化，浓度高达10 pas，2）在TGF-β 1处理的PANC-1细胞中，BGN mRNA的上调之前是p38及其上游激活剂MKK 6磷酸化的延迟增加，3）通过稳定的逆转录病毒转导用p38或MKK 6的显性负突变体抑制p38途径降低TGF-β 1诱导的BGN mRNA表达，4）野生型p38或MKK 6的过表达增强了TGF-β 1对BGN mRNA的作用，而MKK 3则没有。我们进一步证明，TGF-β 1对p38的激活（延迟）是在Smads的下游，并且需要一个功能性的Smad通路，因为用SB 202190阻断TGF-β诱导的p38活性对Smad 2磷酸化没有影响，但是通过强制表达Smad 7阻断Smad信号传导消除了TGF-β 1对p38激活的诱导，如前所述，BGN mRNA表达;最后，在Smad 4缺失的CFPAC-1细胞中Smad 4的再表达恢复了TGF-β诱导的p38磷酸化，并且如前所述，恢复了BGN mRNA的积累。这些结果清楚地表明，TGF-β 1诱导胰腺细胞中BGN表达需要激活Smad信号下游的MKK 6-p38 MAPK信号，并为炎症反应相关纤维化和结缔组织增生中BGN的上调提供了机制线索。
Several signaling pathways have been implicated in mediating TGF-beta1-induced extracellular matrix production and fibrosis. We have shown recently that induction of biglycan (BGN) expression by TGF-beta1 depended on a functional Smad pathway (Chen, W.-B., Lenschow, W., Tiede, K., Fischer, J. W., Kalthoff, H., and Ungefroren, H. (2002) J. Biol. Chem. 277,36118-36128). Here, we present evidence that the ability of TGF-beta1 to induce BGN mRNA, in addition to Smads, requires p38 MAPK signaling, because 1) pharmacological inhibitors of p38 dose-dependently inhibited the TGF-beta effect without significantly affecting the transcriptional activity of a constitutively active mutant of the TGF-beta type I receptor or Smad2 phosphorylation at concentrations up to 10 pas, 2) the up-regulation of BGN mRNA was preceded by a delayed increase in the phosphorylation of p38 and its upstream activator MKK6 in TGF-beta1-treated PANC-1 cells, 3) inhibition of the p38 pathway by stable retroviral transduction with a dominant negative mutant of either p38 or MKK6 reduced TGF-beta1-induced BGN mRNA expression, and 4) overexpression of wild-type p38 or MKK6, but not MKK3, augmented the TGF-beta1 effect on BGN mRNA. We further demonstrate that the (delayed) p38 activation by TGF-beta1 is downstream of Smads and requires a functional Smad pathway, because blocking TGF-beta-induced p38 activity with SB202190 had no effect on Smad2 phosphorylation, but blocking Smad signaling by forced expression of Smad7 abolished TGF-beta1 induction of p38 activation and, as shown earlier, BGN mRNA expression; finally, re-expression of Smad4 in Smad4-null CFPAC-1 cells restored TGF-beta-induced p38 phosphorylation and, as demonstrated previously, BGN mRNA accumulation. These results clearly show that TGF-beta1 induction of BGN expression in pancreatic cells requires activation of MKK6-p38 MAPK signaling downstream of Smad signaling and provide a mechanistic clue to the up-regulation of BGN seen in inflammatory response-related fibrosis and desmoplasia.