Facultad de Ciencias Químicas, Departamento de Química Biológica Ranwel Caputto, Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC-CONICET), Universidad Nacional de Córdoba, 5000, Córdoba, Argentina.
Mol Neurobiol. 2019 Mar;56(3):1653-1664. doi: 10.1007/s12035-018-1182-x. Epub 2018 Jun 18.
After retrotranslocation from the endoplasmic reticulum to the cytoplasm, calreticulin is modified by the enzyme arginyltransferase-1 (ATE1). Cellular levels of arginylated calreticulin (R-CRT) are regulated in part by the proteasomal system. Under various stress conditions, R-CRT becomes associated with stress granules (SGs) or reaches the plasma membrane (PM), where it participates in pro-apoptotic signaling. The mechanisms underlying the resistance of tumor cells to apoptosis induced by specific drugs remain unclear. We evaluated the regulatory role of R-CRT in apoptosis of human glioma cell lines treated with the proteasome inhibitor bortezomib (BT). Two cell lines (HOG, MO59K) displaying distinctive susceptibility to apoptosis induction were studied further. BT efficiency was found to be correlated with a subcellular distribution of R-CRT. In MO59K (apoptosis-resistant), R-CRT was confined to SGs formed following BT treatment. In contrast, HOG (apoptosis-susceptible) treated with BT showed lower SG formation and higher levels of cytosolic and PM R-CRT. Increased R-CRT level was associated with enhanced mobilization of intracellular Ca and with sustained apoptosis activation via upregulation of cell death receptor DR5. R-CRT overexpression in the cytoplasm of MO59K rendered the cells susceptible to BT-induced, DR5-mediated cell death. Our findings suggest that R-CRT plays an essential role in the effect of BT treatment on tumor cells and that ATE1 is a strong candidate target for future studies of cancer diagnosis and therapy.
内质网到细胞质的逆向转运后，钙网蛋白被精氨酰转移酶-1（ATE1）修饰。细胞内精氨酰化钙网蛋白（R-CRT）的水平部分受蛋白酶体系统调节。在各种应激条件下，R-CRT 与应激颗粒（SGs）结合或到达质膜（PM），在那里它参与促凋亡信号。肿瘤细胞对特定药物诱导的凋亡的耐药机制尚不清楚。我们评估了 R-CRT 在人神经胶质瘤细胞系用蛋白酶体抑制剂硼替佐米（BT）处理的凋亡中的调节作用。进一步研究了显示出对凋亡诱导有明显不同敏感性的两个细胞系（HOG、MO59K）。BT 效率与 R-CRT 的亚细胞分布相关。在 MO59K（抗凋亡）中，R-CRT 局限于 BT 处理后形成的 SG 中。相比之下，BT 处理的 HOG（凋亡敏感）表现出较低的 SG 形成和更高水平的细胞质和 PM R-CRT。R-CRT 水平增加与细胞内 Ca 的动员增加以及通过上调细胞死亡受体 DR5 持续激活凋亡有关。在 MO59K 细胞质中过表达 R-CRT 使细胞易受 BT 诱导的 DR5 介导的细胞死亡。我们的研究结果表明，R-CRT 在 BT 治疗对肿瘤细胞的作用中起关键作用，ATE1 是癌症诊断和治疗未来研究的一个重要候选靶点。
