Proteasome inhibition boosts autophagic degradation of ubiquitinated-AGR2 and enhances the antitumor efficiency of bevacizumab
Proteasome inhibition boosts autophagic degradation of ubiquitinated-AGR2 and enhances the antitumor efficiency of bevacizumab
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DOI：
10.1038/s41388-019-0675-z
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发表时间：
2019-01
期刊：
影响因子：
8
通讯作者：
Dawei Wang;Qingqing Xu;Q. Yuan;Mengqi Jia;Huan-min Niu;Xiaofei Liu;Jinsan Zhang;C. Young;Huiqing Yuan
中科院分区：
文献类型：
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作者：
Dawei Wang;Qingqing Xu;Q. Yuan;Mengqi Jia;Huan-min Niu;Xiaofei Liu;Jinsan Zhang;C. Young;Huiqing Yuan
前梯度2 （AGR2）是一种属于蛋白二硫异构酶（PDI）家族的蛋白，在多种癌症中过表达，并促进血管生成以驱动癌症进展。癌症中控制AGR2丰度的机制在很大程度上仍然未知。在这里，我们观察到在肺癌细胞中，蛋白酶体抑制剂MG132/硼替佐米在mRNA和蛋白水平上显著抑制AGR2的表达。mg132介导的AGR2转录抑制与ROS生成和内质网应激诱导无关，但部分原因是E2F1的下调。进一步的研究表明，MG132通过激活自噬促进AGR2的多泛素化降解，这可以通过Atg5和Atg7基因缺失细胞中AGR2水平的显著恢复或自噬抑制剂来证明。雷帕霉素激活的自噬显著降低了细胞和给药硼替佐米的小鼠组织样品中的AGR2蛋白。我们还提供了证据，证明k48连接的多泛素链通过E3连接酶UBR5结合到AGR2的K89上。此外，自噬受体NBR1被证明在MG132或硼替佐米对多泛素化AGR2的清除中起重要作用。重要的是，通过蛋白酶体抑制AGR2的下调显著增强了贝伐单抗的抗肿瘤活性，突出了AGR2作为化疗亚组患者选择的预测标志物的重要性。
Anterior gradient 2 (AGR2), a protein belonging to the protein disulfide isomerase (PDI) family, is overexpressed in multiple cancers and promotes angiogenesis to drive cancer progression. The mechanisms controlling AGR2 abundance in cancer remain largely unknown. Here, we observed that AGR2 expression is significantly suppressed by proteasome inhibitor MG132/bortezomib at mRNA and protein levels in lung cancer cells. MG132-mediated repression of AGR2 transcription was independent of ROS generation and ER stress induction, but partially resulted from the downregulated E2F1. Further investigation revealed that MG132 facilitated polyubiquitinated AGR2 degradation through activation of autophagy, as evidenced by predominant restoration of AGR2 level in cells genetic depletion of Atg5 and Atg7, or by autophagy inhibitors. Activation of autophagy by rapamycin noticeably reduced the AGR2 protein in cells and in the mouse tissue samples administrated with bortezomib. We also provided evidence identifying the K48-linked polyubiquitin chains conjugating onto K89 of AGR2 by an E3 ligase UBR5. In addition, an autophagy receptor NBR1 was demonstrated to be important in polyubiquitinated AGR2 clearance in response to MG132 or bortezomib. Importantly, downregulation of AGR2 by proteasome inhibition significantly enhanced antitumor activity of bevacizumab, highlighting the importance of AGR2 as a predictive marker for selection of subgroup patients in chemotherapy.