Department of Life Science, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea.
PLoS One. 2010 Dec 20;5(12):e15645. doi: 10.1371/journal.pone.0015645.
The nuclear inclusion a (NIa) protease of turnip mosaic virus (TuMV) is responsible for the processing of the viral polyprotein into functional proteins. NIa was previously shown to possess a relatively strict substrate specificity with a preference for Val-Xaa-His-Gln↓, with the scissile bond located after Gln. The presence of the same consensus sequence, Val(12)-His-His-Gln(15), near the presumptive α-secretase cleavage site of the amyloid-β (Aβ) peptide led us to hypothesize that NIa could possess activity against Aβ.
METHODOLOGY/PRINCIPAL FINDINGS: Western blotting results showed that oligomeric as well as monomeric forms of Aβ can be degraded by NIa in vitro. The specific cleavage of Aβ was further confirmed by mass spectrometry analysis. NIa was shown to exist predominantly in the cytoplasm as observed by immunofluorescence microscopy. The overexpression of NIa in B103 neuroblastoma cells resulted in a significant reduction in cell death caused by both intracellularly generated and exogenously added Aβ. Moreover, lentiviral-mediated expression of NIa in APP(sw)/PS1 transgenic mice significantly reduced the levels of Aβ and plaques in the brain.
CONCLUSIONS/SIGNIFICANCE: These results indicate that the degradation of Aβ in the cytoplasm could be a novel strategy to control the levels of Aβ, plaque formation, and the associated cell death.
芜菁花叶病毒（TuMV）的核包含体 a（NIa）蛋白酶负责将病毒多蛋白加工成功能性蛋白。先前的研究表明，NIa 具有相对严格的底物特异性，偏爱 Val-Xaa-His-Gln↓，其中裂解键位于 Gln 之后。在淀粉样β（Aβ）肽的推定 α-分泌酶切割位点附近存在相同的共有序列 Val(12)-His-His-Gln(15)，这使我们假设 NIa 可能对 Aβ 具有活性。
方法/主要发现：Western blot 结果表明，寡聚体和单体形式的 Aβ均可在体外被 NIa 降解。通过质谱分析进一步证实了 Aβ 的特异性切割。免疫荧光显微镜观察到 NIa 主要存在于细胞质中。在 B103 神经母细胞瘤细胞中过表达 NIa 可显著减少由细胞内产生和外源性添加的 Aβ 引起的细胞死亡。此外，慢病毒介导的 APP(sw)/PS1 转基因小鼠中 NIa 的表达显著降低了大脑中的 Aβ 水平和斑块。
结论/意义：这些结果表明，细胞质中 Aβ 的降解可能是控制 Aβ 水平、斑块形成和相关细胞死亡的一种新策略。
