Type II cGMP-dependent protein kinase inhibits ERK/JNK-mediated activation of transcription factors in gastric cancer cells
Type II cGMP-dependent protein kinase inhibits ERK/JNK-mediated activation of transcription factors in gastric cancer cells
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II 型 cGMP 依赖性蛋白激酶抑制胃癌细胞中 ERK/JNK 介导的转录因子激活
DOI：
10.3892/mmr.2012.1050
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发表时间：
2012-11-01
影响因子：
3.4
通讯作者：
Shao, Genbao
中科院分区：
文献类型：
--
作者：
Sang, Jianrong;Chen, Yongchang;Shao, Genbao
已有研究表明II型cGMP依赖性蛋白激酶（PKG II）通过阻断EGF触发的MAPK/ERK信号转导抑制胃癌细胞增殖，提示PKG II可能是一种潜在的抗癌因子。在本研究中，PKG II在EGF诱导的MAPK/ERK信号转导通路中的转录因子活化中的作用进行了研究。用编码PKG Ⅱ cDNA的腺病毒（pAd-PKG Ⅱ）感染BGC-823人胃癌细胞，以增加PKG Ⅱ的表达，并用8-pCPT-cGMP处理以激活PKG Ⅱ。利用荧光素酶报告基因分析，发现PKG II显著抑制EGF诱导的AP-1和Elk I的转录活性。与PKG II对AP-1活性的抑制作用一致，AP-1的组分c-Jun和c-Fos的表达水平也被抑制。免疫共沉淀分析表明，EGF处理通过诱导p-c-Jun-c-Jun同源二聚体和p-c-Jun-c-Fos异源二聚体的形成而增加AP-1的含量。然而，这种结合被激活的PKG II有效地阻断。虽然用MAPK抑制剂预处理抑制了EGF诱导的AP-1和Elk 1的转录活性，PKG II阻止EGF诱导的ERK和JNK的磷酸化/激活，但不能阻止EGF诱导的p38 MAPK的磷酸化。这些数据表明PKG II通过抑制ERK-/JNK-而不是p38 MAPK介导的AP-1和Elk 1反式激活来抑制EGF触发的胃癌细胞增殖。
A previous study has shown that type II cGMP-dependent protein kinase (PKG II) inhibits the proliferation of gastric cancer cells through blocking EGF-triggered MAPK/ERK signal transduction, indicating that the kinase may be a potential anticancer factor. In the present study, the role of PKG II in the EGF-induced activation of transcription factors in the MAPK/ERK signal transduction pathway was investigated. BGC-823 human gastric cancer cells were infected with adenoviral constructs encoding the cDNA of PKG II (pAd-PKG II) to increase the expression of PKG II and treated with 8-pCPT-cGMP to activate the enzyme. Using luciferase reporter assays, it was revealed that PKG II markedly suppressed the EGF-induced transcriptional activities of AP-1 and Elk I. Consistent with the inhibitory effect of PKG II on AP-1 activity, the expression levels of c-Jun and c-Fos, components of AP-1, were also inhibited. Co-immunoprecipitation analysis demonstrated that EGF treatment increased the AP-1 content through inducing the formation of p-c-Jun-c-Jun homodimers and p-c-Jun-c-Fos heterodimers. However, this combination was efficiently blocked by activated PKG II. While pretreatments with MAPK inhibitors suppressed the EGF-induced transcriptional activities of AP-1 and Elk!, PKG II prevented the EGF-induced phosphorylation/activation of ERK and JNK, but not the phosphorylation of p38MAPK induced by EGF. These data suggest that PKG II inhibits the EGF-triggered proliferation of gastric cancer cells through suppressing ERK-/JNK-, but not p38MAPK, -mediated AP-1 and Elk1 transactivation.