National Institute of Cancer Research, National Health Research Institutes, No. 367, Shengli Road, Tainan, 704, Taiwan.
Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, 807, Taiwan.
J Hematol Oncol. 2019 Jul 19;12(1):79. doi: 10.1186/s13045-019-0769-7.
The biological function of protein arginine methyltransferase 3 (PRMT3) is not well known because very few physiological substrates of this methyltransferase have been identified to date.
The clinical significance of PRMT3 in pancreatic cancer was studied by database analysis. The PRMT3 protein level of human pancreatic tumors was detected by immunoblotting and immunohistochemical staining. PRMT3-associated proteins and the methylation sites on the proteins were investigated using mass spectrometry. Seahorse Bioscience analyzed the metabolic reprogramming. Combination index analysis and xenograft animal model were conducted to explore the effects of combination of inhibitors of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and oxidative phosphorylation on tumor growth.
We found that the expression of PRMT3 is upregulated in pancreatic cancer, and its expression is associated with poor survival. We identified GAPDH as a PRMT3-binding protein and demonstrated that GAPDH is methylated at R248 by PRMT3 in vivo. The methylation of GAPDH by PRMT3 enhanced its catalytic activity while the mutation of R248 abolished the effect. In cells, PRMT3 overexpression triggered metabolic reprogramming and enhanced glycolysis and mitochondrial respiration simultaneously in a GAPDH-dependent manner. PRMT3-overexpressing cancer cells were addicted to GAPDH-mediated metabolism and sensitive to the inhibition of GAPDH and mitochondrial respiration. The combination of inhibitors of GAPDH and oxidative phosphorylation induced a synergistic inhibition on cellular growth in vitro and in vivo.
Our results suggest that PRMT3 mediates metabolic reprogramming and cellular proliferation through methylating R248 of GAPDH, and double blockade of GAPDH and mitochondrial respiration could be a novel strategy for the treatment of PRMT3-overexpressing pancreatic cancer.
蛋白质精氨酸甲基转移酶 3（PRMT3）的生物学功能尚不清楚，因为迄今为止仅鉴定出这种甲基转移酶的少数生理底物。
通过数据库分析研究了 PRMT3 在胰腺癌中的临床意义。通过免疫印迹和免疫组织化学染色检测人胰腺肿瘤中的 PRMT3 蛋白水平。使用质谱法研究 PRMT3 相关蛋白和蛋白上的甲基化位点。 Seahorse Bioscience 分析了代谢重编程。进行组合指数分析和异种移植动物模型，以探讨甘油醛-3-磷酸脱氢酶（GAPDH）和氧化磷酸化抑制剂联合对肿瘤生长的影响。
我们发现 PRMT3 在胰腺癌中表达上调，其表达与不良预后相关。我们鉴定出 GAPDH 是 PRMT3 的结合蛋白，并证明 GAPDH 是体内 PRMT3 甲基化的 R248。PRMT3 对 GAPDH 的甲基化增强了其催化活性，而 R248 的突变则消除了该作用。在细胞中，PRMT3 过表达以 GAPDH 依赖的方式触发代谢重编程，同时增强糖酵解和线粒体呼吸。PRMT3 过表达的癌细胞依赖 GAPDH 介导的代谢，并且对 GAPDH 和线粒体呼吸的抑制敏感。GAPDH 和氧化磷酸化抑制剂的联合在体外和体内对细胞生长均具有协同抑制作用。
我们的结果表明，PRMT3 通过将 R248 甲基化修饰 GAPDH 来介导代谢重编程和细胞增殖，并且 GAPDH 和线粒体呼吸的双重阻断可能是治疗 PRMT3 过表达胰腺癌的新策略。
