Coupling of Grb2 to Gab1 mediates hepatocyte growth factor-induced high intensity ERK signal required for inhibition of HepG2 hepatoma cell proliferation
Coupling of Grb2 to Gab1 mediates hepatocyte growth factor-induced high intensity ERK signal required for inhibition of HepG2 hepatoma cell proliferation
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DOI：
10.1074/jbc.m704999200
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发表时间：
2008-01-18
影响因子：
4.8
通讯作者：
Kitamura, Naomi
中科院分区：
文献类型：
--
作者：
Kondo, Asuka;Hirayama, Naoki;Kitamura, Naomi
细胞外信号调节激酶（ERK）途径的激活是生长因子调节细胞增殖的关键因素。肝细胞生长因子（HGF）诱导的人肝癌细胞系HepG 2细胞周期阻滞需要ERK通路的强烈激活。在这项研究中，我们研究了激活的分子机制。我们构建了一个嵌合受体组成的细胞外结构域的神经生长因子受体和细胞质结构域的肝细胞生长因子受体（c-Met），并引入了一个点突变（N1358 H）的嵌合受体，这特异性地取消了直接结合Grb 2的c-Met。该突变嵌合受体未能介导ERK的强烈激活、Cdk抑制剂p16（INK 4a）表达的上调以及配体刺激对HepG 2细胞增殖的抑制。此外，突变体受体没有诱导对接蛋白Gab 1的酪氨酸磷酸化。用siRNA敲低Gab 1可抑制HGF诱导的ERK的强烈激活和HepG 2细胞增殖的抑制。这些结果表明，Gab 1与Grb 2的偶联介导了HGF诱导的ERK通路的强烈激活，这是抑制HepG 2细胞增殖所必需的。
Activation of the extracellular signal-regulated kinase (ERK) pathway is a key factor in the regulation of cell proliferation by growth factors. Hepatocyte growth factor (HGF)-induced cell cycle arrest in the human hepatocellular carcinoma cell line HepG2 requires strong activation of the ERK pathway. In this study, we investigated the molecular mechanism of the activation. We constructed a chimeric receptor composed of the extracellular domain of the NGF receptor and the cytoplasmic domain of the HGF receptor (c-Met) and introduced a point mutation (N1358H) into the chimeric receptor, which specifically abrogates the direct binding of Grb2 to c-Met. The mutant chimeric receptor failed to mediate the strong activation of ERK, up-regulation of the expression of a Cdk inhibitor p16(INK4a) and inhibition of HepG2 cell proliferation by ligand stimulation. Moreover, the mutant receptor did not induce tyrosine phosphorylation of the docking protein Gab1. Knockdown of Gab1 using siRNA suppressed the HGF-induced strong activation of ERK and inhibition of HepG2 cell proliferation. These results suggest that coupling of Grb2 to Gab1 mediates the HGF-induced strong activation of the ERK pathway, which is required for the inhibition of HepG2 cell proliferation.