Department of Biotechnology, National Institute of Pharmaceutical Education and Research, SAS Nagar, Punjab, India.
Biochem J. 2013 Sep 1;454(2):217-25. doi: 10.1042/BJ20121806.
Maintenance of cellular redox homoeostasis forms an important part of the cellular defence mechanism and continued cell viability. Despite extensive studies, the role of the chaperone Hsp104 (heat-shock protein of 102 kDa) in propagation of misfolded protein aggregates in the cell and generation of oxidative stress remains poorly understood. Expression of RNQ1-RFP in Saccharomyces cerevisiae cells led to the generation of the prion form of the protein and increased oxidative stress. In the present study, we show that disruption of Hsp104 in an isogenic yeast strain led to solubilization of RNQ1-RFP. This reduced the oxidative stress generated in the cell. The higher level of oxidative stress in the Hsp104-containing (parental) strain correlated with lower activity of almost all of the intracellular antioxidant enzymes assayed. Surprisingly, this did not correspond with the gene expression analysis data. To compensate for the decrease in protein translation induced by a high level of reactive oxygen species, transcriptional up-regulation takes place. This explains the discrepancy observed between the transcription level and functional enzymatic product. Our results show that in a ΔHsp104 strain, due to lower oxidative stress, no such mismatch is observed, corresponding with higher cell viability. Thus Hsp104 is indirectly responsible for enhancing the oxidative stress in a prion-rich environment.
细胞氧化还原稳态的维持是细胞防御机制和持续细胞存活的重要组成部分。尽管进行了广泛的研究，但伴侣蛋白 Hsp104（热休克蛋白 102kDa）在细胞内错误折叠蛋白聚集体的传播和氧化应激产生中的作用仍知之甚少。在酿酒酵母细胞中表达 RNQ1-RFP 会导致该蛋白形成朊病毒形式并增加氧化应激。在本研究中，我们表明，在同基因酵母菌株中破坏 Hsp104 会导致 RNQ1-RFP 溶解。这降低了细胞中产生的氧化应激。在含有 Hsp104（亲本）菌株中观察到的更高水平的氧化应激与几乎所有测定的细胞内抗氧化酶的活性降低相关。令人惊讶的是，这与基因表达分析数据不相符。为了补偿高水平活性氧诱导的蛋白质翻译减少，会发生转录上调。这解释了观察到的转录水平和功能性酶产物之间的差异。我们的研究结果表明，在ΔHsp104 菌株中，由于氧化应激较低，因此不会出现这种不匹配，这与更高的细胞活力相对应。因此，Hsp104 间接负责增强富含朊病毒的环境中的氧化应激。
