Beclin 1 enhances proteasome inhibition-mediated cytotoxicity of thyroid cancer cells in macroautophagy-independent manner.
Beclin 1 enhances proteasome inhibition-mediated cytotoxicity of thyroid cancer cells in macroautophagy-independent manner.
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DOI：
10.1210/jc.2012-2679
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发表时间：
2013-02
期刊：
影响因子：
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通讯作者：
Hai-yan Zhang;Zhen‐Xian Du;Xin Meng;Z. Zong;Hua-Qin Wang
中科院分区：
文献类型：
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作者：
Hai-yan Zhang;Zhen‐Xian Du;Xin Meng;Z. Zong;Hua-Qin Wang
泛素-蛋白酶体系统和巨自噬是细胞内蛋白质降解的两条主要途径。新的证据表明，蛋白酶体抑制剂阻断泛素-蛋白酶体系统可激活巨自噬。目的探讨自噬必需基因Beclin 1在蛋白酶体抑制剂介导的甲状腺癌细胞毒作用中的作用。设计采用酸性营养染料染色和荧光显微镜观察EGF-LC 3的分布，以及Western blot检测LC 3-II的转换。为了确定Beclin 1的作用，用Beclin 1质粒或针对Beclin 1的shRNA转染细胞。MTT法检测细胞活力，流式细胞仪检测细胞凋亡。结果蛋白酶体抑制剂降低Beclin 1表达。此外，用PI 3 K抑制剂3-MA或渥曼青霉素治疗以及Beclin 1表达的敲低不能影响由蛋白酶体抑制剂介导的自噬反应。Beclin 1过表达通过抑制生存素增强蛋白酶体介导的甲状腺癌细胞毒性结论蛋白酶体抑制剂以非Beclin 1依赖的方式引起甲状腺癌细胞的非Beclin 1依赖性巨自噬反应。Beclin 1在甲状腺癌细胞暴露于蛋白酶体抑制剂后具有自噬独立的抗肿瘤作用。
CONTEXT The ubiquitin-proteasome system and macroautophagy are two major pathways for intracellular protein degradation. Emerging lines of evidence have shown that blockade of ubiquitin-proteasome system by proteasome inhibitors activates macroautophagy. OBJECTIVE The purpose of this study was to determine the involvement of autophagy essential gene Beclin 1 in cytotoxicity of thyroid cancer cells mediated by proteasome inhibitors. DESIGN Autophagy was measured by acidic-trophic dye staining and EGF-LC3 distribution using fluorescence microscopy, as well as LC3-II transition using Western blot. To ascertain the effect of Beclin 1, cells were transfected with Beclin 1 plasmid or shRNA against Beclin 1. Cell viability and apoptotic cells were measured using MTT assay and flow cytometry, respectively. RESULTS Proteasome inhibitors decreased Beclin 1 expression. In addition, treatment with PI3K inhibitors 3-MA or wortmannin, as well as knockdown of Beclin 1 expression, was unable to affect autophagic responses mediated by proteasome inhibitors. Overexpression of Beclin 1 enhanced proteasome inhibitor-mediated cytotoxicity of thyroid cancer cells via suppression of survivin. CONCLUSIONS Proteasome inhibitors cause Beclin 1-independent macroautophagic responses of thyroid cancer cells in a Beclin 1-independent manner. Beclin 1 possesses autophagy-independent antitumoral effects upon exposure of thyroid cancer cells to proteasome inhibitors.