Physical interaction between human ribonucleotide reductase large subunit and thioredoxin increases colorectal cancer malignancy
Physical interaction between human ribonucleotide reductase large subunit and thioredoxin increases colorectal cancer malignancy
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人核糖核苷酸还原酶大亚基和硫氧还蛋白之间的物理相互作用会增加结直肠癌的恶性程度
DOI：
10.1074/jbc.m117.783365
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发表时间：
2017-06-02
影响因子：
4.8
通讯作者：
Shao, Jimin
中科院分区：
文献类型：
--
作者：
Lou, Meng;Liu, Qian;Shao, Jimin
核糖核苷酸还原酶（Ribonucleotide reductase，RR）是DNA合成的限速酶，催化核糖核苷酸还原为脱氧核糖核苷酸。在每次酶促转换期间，催化大亚基中的活性位点二硫化物的还原通过其C-末端尾中的一对穿梭半胱氨酸残基进行。硫氧还蛋白（Trx）和谷氧还蛋白（Grx）是普遍存在的氧化还原蛋白，催化巯基-二硫键交换反应。在此，对临床结直肠癌（CRC）标本的免疫组织化学检查显示，人硫氧还蛋白1（hTrx 1）而不是人谷氧还蛋白1（hGrx 1）在癌组织中与人RR大亚基（RRM 1）沿着上调，并且两种蛋白的表达水平与癌症恶性程度相关。异位表达的hTrx 1显著增加RR活性、DNA合成以及细胞增殖和迁移。重要的是，hTrx 1和RRM 1的抑制在CRC细胞和异种移植小鼠中产生协同抗癌作用。此外，hTrx 1而不是hGrx 1是RRM 1再生的有效还原酶。我们还观察到在CRC细胞中RRM 1和hTrx 1之间的直接蛋白质-蛋白质相互作用。有趣的是，除了已知的两个保守的半胱氨酸，在RRM 1 C末端的第三个半胱氨酸（Cys 779）是必不可少的RRM 1再生和结合到hTrx 1，而在hTrx 1 Cys 32和Cys 35发挥对应的作用。我们的研究结果表明，在CRC中上调RRM 1和hTrx 1直接相互作用，并促进RR活性，导致DNA合成增强和癌症恶性度。我们建议RRM 1-hTrx 1相互作用可能是一个新的潜在的治疗癌症的目标。
Ribonucleotide reductase (RR) is the rate-limiting enzyme in DNA synthesis, catalyzing the reduction of ribonucleotides to deoxyribonucleotides. During each enzymatic turnover, reduction of the active site disulfide in the catalytic large subunit is performed by a pair of shuttle cysteine residues in its C-terminal tail. Thioredoxin (Trx) and glutaredoxin (Grx) are ubiquitous redox proteins, catalyzing thiol-disulfide exchange reactions. Here, immunohistochemical examination of clinical colorectal cancer (CRC) specimens revealed that human thioredoxin1 (hTrx1), but not human glutaredoxin1 (hGrx1), was up-regulated along with human RR large subunit (RRM1) in cancer tissues, and the expression levels of both proteins were correlated with cancer malignancy stage. Ectopically expressed hTrx1 significantly increased RR activity, DNA synthesis, and cell proliferation and migration. Importantly, inhibition of both hTrx1 and RRM1 produced a synergistic anticancer effect in CRC cells and xenograft mice. Furthermore, hTrx1 rather than hGrx1 was the efficient reductase for RRM1 regeneration. We also observed a direct protein-protein interaction between RRM1 and hTrx1 in CRC cells. Interestingly, besides the known two conserved cysteines, a third cysteine (Cys779) in the RRM1 C terminus was essential for RRM1 regeneration and binding to hTrx1, whereas both Cys32 and Cys35 in hTrx1 played a counterpart role. Our findings suggest that the up-regulated RRM1 and hTrx1 in CRC directly interact with each other and promote RR activity, resulting in enhanced DNA synthesis and cancer malignancy. We propose that the RRM1-hTrx1 interaction might be a novel potential therapeutic target for cancer treatment.