Cross-talk between ERK MAP kinase and Smad-signaling pathways enhances TGF-β dependent responses in human mesangial cells
Cross-talk between ERK MAP kinase and Smad-signaling pathways enhances TGF-β dependent responses in human mesangial cells
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DOI：
10.1096/fj.03-0037fje
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发表时间：
2003-06-01
期刊：
影响因子：
4.8
通讯作者：
Schnaper, HW
中科院分区：
文献类型：
--
作者：
Hayashida, T;deCaestecker, M;Schnaper, HW
转化生长因子 β (TGF-β) 通过一种鲜为人知的机制刺激肾细胞纤维化。此前，我们提出了 TGF-β1 激活的细胞外信号调节激酶 (ERK) 和 Smad 信号在人肾小球系膜细胞胶原蛋白生成中的协同作用。在异源 DNA 结合转录测定中，生化或显性失活 ERK 阻断可降低 TGF-β1 诱导的 Smad3 活性。通过 MEK/ERK 抑制剂 PD98059 (10 muM) 或 U0126 (25 muM) 预处理，Smad2/3 的总丝氨酸磷酸化减少，但 C 末端 (SSXSP)-X-P 基序的磷酸化不减少。在小鼠乳腺上皮 NMuMG 细胞系中未观察到这种效应，表明 Smad2/3 的 ERK 依赖性激活仅发生在某些细胞类型中。 MEK/ERK 抑制剂可减少 TGF-β 刺激的表达的 S m ad 3A 构建体的磷酸化，该构建体具有突变的 C 端 (SSXSP)-X-P 基序。相比之下，MEK/ERK 抑制并不影响连接区共有磷酸化位点突变的 Smad3 构建体 (Smad3EPSM) 的磷酸化。组成型活性 MEK (caMEK) 诱导 alpha2(I) 胶原蛋白启动子活性，该效应被共转染的 Smad3EPSM 阻断，但 Smad3A 则不然。 caMEK 和 TGF-α1 对胶原蛋白启动子活性的影响是相加的。这些结果表明，ERK 依赖性 R-Smad 连接区磷酸化可增强 I 型胶原合成，并暗示人系膜细胞中 ERK 和 Smad 通路之间存在正向交互作用。
Transforming growth factor beta (TGF-beta) stimulates renal cell fibrogenesis by a poorly understood mechanism. Previously, we suggested a synergy between TGF-beta1 activated extracellular signal regulated kinase (ERK) and Smad signaling in collagen production by human glomerular mesangial cells. In a heterologous DNA binding transcription assay, biochemical or dominant-negative ERK blockade reduced TGF-beta1 induced Smad3 activity. Total serine phosphorylation of Smad2/3, but not phosphorylation of the C-terminal (SSXSP)-X-P motif, was de creased by pretreatment with the MEK/ERK inhibitors, PD98059 (10 muM) or U0126 (25 muM). This effect was not seen in the mouse mammary epithelial NMuMG cell line, indicating that ERK-dependent activation of Smad2/3 occurs only in certain cell types. TGF-beta stimulated phosphorylation of an expressed S m ad 3 A construct, wit h a mutated C-terminal (SSXSP)-X-P motif, was reduced by a MEK/ERK inhibitor. In contrast, MEK/ERK inhibition did not affect phosphorylation of a Smad3 construct mutated at consensus phosphorylation sites in the linker region (Smad3EPSM). Constitutively active MEK (caMEK) induced alpha2(I) collagen promoter activity, an effect blocked by co-transfected Smad3EPSM, but not Smad3A. The effects of caMEK and TGF-alpha1 on collagen promoter activity were additive. These results indicate that ERK-dependent R-Smad linker region phosphorylation enhances collagen I synthesis and imply positive cross talk between the ERK and Smad pathways in human mesangial cells.