Glutathiolation Triggers Proteins for Degradation by the Ubiquitin- Proteasome Pathway.
Glutathiolation Triggers Proteins for Degradation by the Ubiquitin- Proteasome Pathway.
复制标题
谷胱甘肽化触发蛋白质通过泛素-蛋白酶体途径降解。
DOI：
10.2174/1566524017666171101165021
复制
发表时间：
2017-12
影响因子：
2.5
通讯作者：
Fu Shang
中科院分区：
文献类型：
--
作者：
Xinyu Zhang;Allen Taylor;Yizhi Liu;Fu Shang
背景
谷氨酸是细胞内的一种小分子抗氧化肽，在维持细胞内还原环境中起重要作用。谷胱甘肽还参与特定蛋白质功能的动态调节，通过某些蛋白质响应氧化应激的可逆谷胱甘肽化。
目的
本工作的目的是机械调查的影响，谷胱甘肽对蛋白质的敏感性降解的泛素蛋白酶体途径（UPP）。
方法和结果
数据表明，γ C-晶状体蛋白和碳酸酐酶III几乎不被未修饰的UPP降解，但在谷胱甘肽化后两者都被UPP快速降解。其他巯基修饰试剂（例如碘乙酰胺）对巯基的修饰也会增加γ C-晶状体蛋白的降解，但不如谷胱甘肽化那么有效。生物物理分析表明，谷胱甘肽引起这些蛋白质的可逆构象变化，包括蛋白质表面疏水性的显着增加和热稳定性的下降。修饰后的蛋白质恢复其天然构象和抗降解后，去除谷胱甘肽部分。引起白内障的T5 P突变体γ C-晶状体蛋白与谷胱甘肽化γ C-晶状体蛋白具有许多生物物理特性，包括表面疏水性增加和热稳定性降低。T5 P突变体γ C-晶状体蛋白也迅速降解。比较谷胱甘肽化γ C-晶状体蛋白与其他形式修饰γ C-晶状体蛋白的构象变化和对降解的敏感性表明，谷胱甘肽诱导的疏水斑块暴露，而不是修饰本身，作为UPP降解的信号。与这一假设一致，掩蔽谷胱甘肽化和T5 P突变体γ C-晶状体蛋白的表面疏水性显著降低了它们对UPP降解的敏感性。
结论
这项工作表明，谷胱甘肽是一种新的机制，为UPP识别底物在氧化应激反应。
BACKGROUND
Glutathione is a small antioxidant peptide in cells and it plays an important role in maintaining a reducing intracellular environment. Glutathione is also involved in the dynamic regulation of specific protein functions by reversible glutathiolation of certain proteins in response to oxidative stress.
OBJECTIVE
The purpose of this work is to mechanistically investigate the effects of glutathiolation on the susceptibility of proteins to degradation by the ubiquitinproteasome pathway (UPP).
METHODS AND RESULTS
The data show that γC-crystallin and carbonic anhydrase III were barely degraded by the UPP without modifications, but both were rapidly degraded by the UPP after glutathiolation. Modifications of sulfhydryls by other thiol-modification reagents, such as iodoacetamide, also increased the degradation of γC-crystallin, but not as effectively as glutathiolation. Biophysical analysis showed that glutathiolation caused reversible conformational changes of these proteins, including a significant increase in protein surface hydrophobicity and a decrease in thermal stability. The modified protein regained its native conformation and its resistance to degradation upon removal of the glutathione moiety. A cataract-causing T5P mutant γC-crystallin shares many biophysical characteristics as glutathiolated γC-crystallin, including increased surface hydrophobicity and decreased thermal stability. T5P mutant γC-crystallin was also rapidly degraded. Comparison of the conformational changes and the susceptibility to degradation of glutathiolated γC-crystallin with other forms of modified γC-crystallin suggests that the glutathiolation-induced exposure of hydrophobic patches, rather than the modification per se, serves as the signal for degradation by the UPP. Consistent with this hypothesis, masking the surface hydrophobicity of glutathiolated and T5P mutant γC-crystallins significantly reduced their susceptibility to degradation by the UPP.
CONCLUSION
This work demonstrates that glutathiolation is a novel mechanism for the UPP to recognize substrates in response to oxidative stress.