School of Biotechnology, Gautam Buddha University, Greater NOIDA, Gautam Budh Nagar 201312, India.
Bioinformatics Core, University of Miami, USA.
Gene. 2018 Aug 30;669:15-27. doi: 10.1016/j.gene.2018.05.081. Epub 2018 May 22.
Target of rapamycin (TOR) regulates cellular homeostasis by coordinating cellular growth pathways in response to different environmental signals. Rapamycin, an allosteric TOR complex 1 (TORC1) inhibitor, has proven to be invaluable for elucidating various aspects of the TOR signalling pathway; however, its applications are limited due to its inability to completely suppress TORC2. In the present study, we examined the effects of a newly discovered potent TOR inhibitor, Torin2, which inhibits both TORC1 and TORC2, on Saccharomyces cerevisiae growth. Genome-scale expression profiling of Torin2 treated yeast cells showed an expression profile similar to that of other TOR inhibitors such as rapamycin and caffeine. Distinct inhibition of cell growth by Torin2 treatment is indicated by the fact that a smaller number of transcripts are altered, compared to the changes after rapamycin and caffeine treatments. Our results revealed that Torin2 leads to increased expression of the calcineurin pathway genes favouring a synergistic therapeutic response of Torin2 in combination with calcineurin inhibitors. Further, Torin2 causes defective bud site selection during asymmetric cell division, indicating a role of TOR signalling in regulation of the budding pattern. Torin2 treated yeast cells exhibit increased expression of metalloreductases which affects iron homeostasis leading to iron toxicity. Notably, the enhanced expression of TOR1 and TOR2 rescue the Torin2 augmented iron toxicity of yeast cell. This study has revealed novel conduits and our results suggest that using Torin2 will enable the dissection of TORC2 mediated functions of the TOR signalling pathway.
雷帕霉素靶蛋白（TOR）通过协调细胞生长途径来响应不同的环境信号，从而调节细胞内稳态。雷帕霉素是一种变构的 TOR 复合物 1（TORC1）抑制剂，已被证明对于阐明 TOR 信号通路的各个方面非常有价值；然而，由于其不能完全抑制 TORC2，其应用受到限制。在本研究中，我们研究了一种新发现的强效 TOR 抑制剂 Torin2 对酿酒酵母生长的影响。Torin2 处理的酵母细胞的全基因组表达谱分析显示，其表达谱与其他 TOR 抑制剂（如雷帕霉素和咖啡因）相似。Torin2 处理导致细胞生长明显受到抑制，与雷帕霉素和咖啡因处理后发生的变化相比，只有较少的转录本发生改变。我们的结果表明，Torin2 导致钙调神经磷酸酶途径基因的表达增加，有利于 Torin2 与钙调神经磷酸酶抑制剂联合治疗的协同反应。此外，Torin2 导致不对称细胞分裂时芽位点选择缺陷，表明 TOR 信号在调节出芽模式中的作用。Torin2 处理的酵母细胞表现出金属还原酶表达增加，这影响铁稳态，导致铁毒性。值得注意的是，TOR1 和 TOR2 的过表达挽救了 Torin2 增强的酵母细胞铁毒性。本研究揭示了新的途径，我们的结果表明，使用 Torin2 将能够解析 TORC2 介导的 TOR 信号通路的功能。
