Wang Lude, Hu Bin, Pan Kailing, Chang Jie, Zhao Xiaoya, Chen Lin, Lin Haiping, Wang Jing, Zhou Gezhi, Xu Wenxia, Yuan Jianlie
Central Laboratory, Affiliated Jinhua Hospital, Zhejiang University School of Medicine, Jinhua, China.
Department of Pathology, Affiliated Jinhua Hospital, Zhejiang University School of Medicine, Jinhua, China.
Front Cell Dev Biol. 2021 Mar 30;9:633259. doi: 10.3389/fcell.2021.633259. eCollection 2021.
Methionine is one of the essential amino acids. How tumor cells adapt and adjust their signal transduction networks to avoid apoptosis in a methionine-restricted environment is worthy of further exploration. In this study, we investigated the molecular mechanism of glioma response to methionine restriction, providing a theoretical basis for new treatment strategies for glioma.
We constructed methionine-restriction-tolerant cells in order to study the response of glioma to a methionine-restricted environment. The transcriptome analysis of the tolerant cells showed significant changes in MAT2A. Western blotting, immunohistochemistry, quantitative real-time PCR, colony formation assays, and other experiments were used to verify the role of MAT2A in glioma genesis. In addition, the regulatory mechanism of MAT2A mRNA nuclear export was investigated by transfection, plasma nucleation separation, and co-immunoprecipitation.
Under methionine restriction, glioma cells showed high expression of MAT2A, and an inhibitor of MAT2A reduced the proliferation of tumor cells. The expression of MAT2A was positively correlated with World Health Organization-grade glioma. High expression of MAT2A was related to increased transfer of its mRNA out of the nucleus. The expression of nuclear export regulatory molecule MTR4 could affect the export of MAT2A mRNA. In a methionine-restricted environment, ubiquitination of MTR4 was enhanced, and thus its protein level was reduced. The E3 ubiquitin ligase was verified to be SYVN1.
In summary, methionine restriction leads to increased ubiquitination of MTR4, which promotes the transfer of MAT2A mRNA out of the nucleus and MAT2A protein expression. MAT2A promotes histone methylation, prompting cells to proliferate in a methionine-restricted environment.
蛋氨酸是必需氨基酸之一。肿瘤细胞如何在蛋氨酸受限的环境中适应和调整其信号转导网络以避免凋亡值得进一步探索。在本研究中，我们研究了胶质瘤对蛋氨酸限制的反应的分子机制，为胶质瘤的新治疗策略提供理论依据。
我们构建了耐蛋氨酸限制的细胞，以研究胶质瘤对蛋氨酸受限环境的反应。对耐受细胞的转录组分析显示MAT2A有显著变化。采用蛋白质免疫印迹法、免疫组织化学法、定量实时聚合酶链反应、集落形成试验等实验来验证MAT2A在胶质瘤发生中的作用。此外，通过转染、血浆成核分离和免疫共沉淀研究了MAT2A mRNA核输出的调控机制。
在蛋氨酸限制条件下，胶质瘤细胞显示MAT2A高表达，MAT2A抑制剂可降低肿瘤细胞的增殖。MAT2A的表达与世界卫生组织分级的胶质瘤呈正相关。MAT2A的高表达与其mRNA从细胞核输出增加有关。核输出调节分子MTR4的表达可影响MAT2A mRNA的输出。在蛋氨酸受限的环境中，MTR4的泛素化增强，因此其蛋白水平降低。验证E3泛素连接酶为SYVN1。
综上所述，蛋氨酸限制导致MTR4泛素化增加，促进MAT2A mRNA从细胞核输出和MAT2A蛋白表达。MAT2A促进组蛋白甲基化，促使细胞在蛋氨酸受限的环境中增殖。
