Verrecchia Franck, Tacheau Charlotte, Wagner Erwin F, Mauviel Alain
INSERM U532, Institut de Recherche sur la Peau Hôpital Saint-Louis, 75475 Paris Cedex 10, France.
J Biol Chem. 2003 Jan 17;278(3):1585-93. doi: 10.1074/jbc.M206927200. Epub 2002 Nov 7.
We have focused our attention on the molecular events underlying the antagonistic activities of pro-inflammatory cytokines against transforming growth factor-beta (TGF-beta)/SMAD signaling. Using jnk1/2-knockout (jnk(-/-)) and I kappa B kinase-gamma/nemo(-/-) fibroblasts, we have determined the specific roles played by the JNK/AP-1 and NF-kappa B/Rel pathways in this phenomenon. We demonstrate that, in a cellular context devoid of JNK activity (i.e. jnk(-/-) fibroblasts), interleukin-1 and tumor necrosis factor-alpha (TNF-alpha) did not inhibit the formation of SMAD-DNA complexes and the resulting SMAD-driven transcription in response to TGF-beta. On the other hand, lack of NF-kappa B activity in nemo(-/-) fibroblasts did not affect the antagonistic effect of pro-inflammatory cytokines against TGF-beta. In the latter cell type, overexpression of antisense c-jun mRNA or of a dominant-negative form of MKK4 blocked the inhibitory activity of TNF-alpha, similar to what was observed in normal human dermal fibroblasts. Among JNK substrates, c-Jun and JunB (but not activating transcription factor-2) antagonized TGF-beta/SMAD signaling in a JNK-dependent manner. Overexpression of JNK1 in jnk(-/-) fibroblasts restored the ability of cytokines and Jun proteins to interfere with SMAD signaling. In junAA mouse embryo fibroblasts, in which c-Jun can no longer be phosphorylated by JNK, JunB substituted for c-Jun in mediating the cytokine effect against SMAD-driven transcription in a JNK-dependent manner. These results suggest a critical role for JNK-mediated c-Jun and JunB phosphorylation in transmitting the inhibitory effect of pro-inflammatory cytokines against TGF-beta-induced SMAD signaling. In addition, we demonstrate that such a JNK-dependent regulatory mechanism underlies the antagonistic activity of TNF-alpha against TGF-beta-induced up-regulation of type I and III collagens in fibroblasts.
我们将注意力集中在促炎细胞因子对转化生长因子-β（TGF-β）/SMAD信号通路拮抗活性的分子机制上。利用jnk1/2基因敲除（jnk(-/-)）和IκB激酶-γ/核因子κB必需调节蛋白（nemo(-/-)）的成纤维细胞，我们确定了JNK/AP-1和NF-κB/Rel通路在此现象中所起的特定作用。我们证明，在缺乏JNK活性的细胞环境中（即jnk(-/-)成纤维细胞），白细胞介素-1和肿瘤坏死因子-α（TNF-α）不会抑制SMAD-DNA复合物的形成以及响应TGF-β产生的SMAD驱动的转录。另一方面，nemo(-/-)成纤维细胞中NF-κB活性的缺失并不影响促炎细胞因子对TGF-β的拮抗作用。在后者这种细胞类型中，反义c-jun mRNA或显性负性形式的MKK4的过表达阻断了TNF-α的抑制活性，这与在正常人皮肤成纤维细胞中观察到的情况相似。在JNK底物中，c-Jun和JunB（而非活化转录因子-2）以JNK依赖的方式拮抗TGF-β/SMAD信号通路。jnk(-/-)成纤维细胞中JNK1的过表达恢复了细胞因子和Jun蛋白干扰SMAD信号的能力。在junAA小鼠胚胎成纤维细胞中，c-Jun不再能被JNK磷酸化，JunB以JNK依赖的方式替代c-Jun介导细胞因子对SMAD驱动转录的作用。这些结果表明JNK介导的c-Jun和JunB磷酸化在传递促炎细胞因子对TGF-β诱导的SMAD信号通路的抑制作用中起关键作用。此外，我们证明这种JNK依赖的调节机制是TNF-α对TGF-β诱导的成纤维细胞中I型和III型胶原上调的拮抗活性的基础。
