Novel AKT1-GLI3-VMP1 Pathway Mediates KRAS Oncogene-induced Autophagy in Cancer Cells
Novel AKT1-GLI3-VMP1 Pathway Mediates KRAS Oncogene-induced Autophagy in Cancer Cells
复制标题
DOI：
10.1074/jbc.m112.370809
复制
发表时间：
2012-07-20
影响因子：
4.8
通讯作者：
Fernandez-Zapico, Martin E.
中科院分区：
文献类型：
--
作者：
Lo Re, Andrea E.;Fernandez-Barrena, Maite G.;Fernandez-Zapico, Martin E.
自噬是一种进化上保守的细胞质细胞成分降解过程。研究表明，自噬在肿瘤促进和下游致癌途径的进展中起作用；然而，这一现象背后的分子机制尚未阐明。在这里，我们提供了一种新的信号通路的体外和体内证据，即致癌基因KRAS诱导VMP1的表达，VMP1是自噬体形成所需的分子，即使在营养充足的条件下也能诱导自噬。RNAi实验证明KRAS需要VMP1来诱导自噬。机制分析发现GLI3是由Hedgehog通路调控的转录因子，是KRAS信号传导的效应因子。GLI3以不依赖刺猬的方式调节自噬以及VMP1的表达和启动子活性。染色质免疫沉淀实验表明，GLI3与VMP1启动子结合，并与组蛋白乙酰转移酶p300复合物调节启动子活性。p300的敲低会损伤KRAS-和gli3诱导该启动子的激活。最后，我们确定了PI3K-AKT1通路是介导GLI3-p300复合物上游VMP1表达和启动子活性的信号通路。总之，这些数据提供了一种新的自噬调控机制的证据，该机制将这一细胞过程整合到调节癌基因诱导的自噬的分子网络中。
Autophagy is an evolutionarily conserved degradation process of cytoplasmic cellular constituents. It has been suggested that autophagy plays a role in tumor promotion and progression downstream oncogenic pathways; however, the molecular mechanisms underlying this phenomenon have not been elucidated. Here, we provide both in vitro and in vivo evidence of a novel signaling pathway whereby the oncogene KRAS induces the expression of VMP1, a molecule needed for the formation of the authophagosome and capable of inducing autophagy, even under nutrient-replete conditions. RNAi experiments demonstrated that KRAS requires VMP1 to induce autophagy. Analysis of the mechanisms identified GLI3, a transcription factor regulated by the Hedgehog pathway, as an effector of KRAS signaling. GLI3 regulates autophagy as well as the expression and promoter activity of VMP1 in a Hedgehog-independent manner. Chromatin immunoprecipitation assays demonstrated that GLI3 binds to the VMP1 promoter and complexes with the histone acetyltransferase p300 to regulate promoter activity. Knockdown of p300 impaired KRAS- and GLI3-induced activation of this promoter. Finally, we identified the PI3K-AKT1 pathway as the signaling pathway mediating the expression and promoter activity of VMP1 upstream of the GLI3-p300 complex. Together, these data provide evidence of a new regulatory mechanism involved in autophagy that integrates this cellular process into the molecular network of events regulating oncogene-induced autophagy.