Identification of TRIM25 as a Negative Regulator of Caspase-2 Expression Reveals a Novel Target for Sensitizing Colon Carcinoma Cells to Intrinsic Apoptosis
Identification of TRIM25 as a Negative Regulator of Caspase-2 Expression Reveals a Novel Target for Sensitizing Colon Carcinoma Cells to Intrinsic Apoptosis
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DOI：
10.3390/cells8121622
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发表时间：
2019-12-01
期刊：
影响因子：
6
通讯作者：
Eberhardt, Wolfgang
中科院分区：
文献类型：
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作者：
Nasrullah, Usman;Haeussler, Kristina;Eberhardt, Wolfgang
结直肠癌（CRC）是最常见的癌症之一，其特点是由于原发肿瘤的强转移潜力和高治疗耐药率而具有高死亡率。因此，逃避细胞凋亡是肿瘤细胞对化疗和放疗敏感性降低的主要潜在原因。利用RNA亲和层析技术，我们在结肠癌细胞中鉴定出含有tripartite motif-containing protein 25 （TRIM25）是一个真正的caspase-2 mrna结合蛋白。功能丧失和功能获得的方法显示，TRIM25可以降低caspase-2的蛋白水平，但不会显著影响caspase-2 mRNA水平。此外，环己亚胺实验表明TRIM25不影响caspase-2蛋白的稳定性。此外，TRIM25的沉默诱导caspase-2转录本从RNP颗粒向翻译活性多体重新分布，表明TRIM25负向干扰caspase-2的翻译。在功能上，TRIM25缺失后caspase-2的升高显著增加了结肠直肠癌细胞对药物诱导的内在凋亡的敏感性，这与caspase-3切割和细胞色素c释放增加有关。重要的是，短暂的TRIM25敲低导致的细胞凋亡增敏效应通过caspase-2的沉默得以恢复，这证明了caspase-2的关键作用。TRIM25对caspase-2的抑制暗示了一种对结直肠癌化疗耐药至关重要的生存机制。
Colorectal cancer (CRC) is one of the most common cancers that is characterized by a high mortality due to the strong metastatic potential of the primary tumor and the high rate of therapy resistance. Hereby, evasion of apoptosis is the primary underlying cause of reduced sensitivity of tumor cells to chemo- and radiotherapy. Using RNA affinity chromatography, we identified the tripartite motif-containing protein 25 (TRIM25) as a bona fide caspase-2 mRNA-binding protein in colon carcinoma cells. Loss-of-function and gain-of-function approaches revealed that TRIM25 attenuates the protein levels of caspase-2 without significantly affecting caspase-2 mRNA levels. In addition, experiments with cycloheximide revealed that TRIM25 does not affect the protein stability of caspase-2. Furthermore, silencing of TRIM25 induced a significant redistribution of caspase-2 transcripts from RNP particles to translational active polysomes, indicating that TRIM25 negatively interferes with caspase-2 translation. Functionally, the elevation in caspase-2 upon TRIM25 depletion significantly increased the sensitivity of colorectal cells to drug-induced intrinsic apoptosis as implicated by increased caspase-3 cleavage and cytochrome c release. Importantly, the apoptosis-sensitizing effects by transient TRIM25 knockdown were rescued by concomitant silencing of caspase-2, demonstrating a critical role of caspase-2. Inhibition of caspase-2 by TRIM25 implies a survival mechanism that critically contributes to chemotherapeutic drug resistance in CRC.