Liu Yanping, Cui Mei, Lu Zhengyu, Yang Qi, Dong Qiang
Department of Neurology, Huashan Hospital, State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200040, P.R. China.
Department of Neurology, Yueyang Hospital of Integrated Traditional Chinese and Western Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai 200437, P.R. China.
Mol Med Rep. 2016 Feb;13(2):1389-94. doi: 10.3892/mmr.2015.4664. Epub 2015 Dec 9.
Previous studies by our group showed that tissue kallikrein (TK) exerts neuroprotective effects during cerebral ischemia. Autophagy is an important adaptive response to cellular stress during nutrient deprivation, and β-catenin in known to repress autophagy. The present study investigated the possible involvement of autophagy and β-catenin signaling in the protective effects of TK under nutrient deprivation-induced stress conditions. TK was shown to promote the survival and inhibit the death of SH-SY5Y cells under serum starvation and enhanced autophagic activity in a concentration-dependent manner, as indicated by augmented light chain (LC)3-II levels and Beclin-1 expression. The autophagy inhibitors 3-methyladenine and NH4Cl abolished the protective effects of TK. Of note, although serum starvation alone and TK treatment increased p62 protein levels and mRNA expression, incubation with the lysosome inhibitor NH4Cl increased the accumulation of LC3-II and p62 protein, indicating normal autophagic flux. It was also observed that β-catenin expression was significantly downregulated by TK treatment. TK stimulated the interaction between LC3 and β-catenin, and NH4Cl abolished the effects of TK on β-catenin levels in serum-starved cells, suggesting the autophagic degradation of β-catenin, which may have led to the enhancement of autophagy. In conclusion, the findings of the present study demonstrated that TK promoted cell survival and β-catenin degradation in serum-starved SH-SY5Y cells via increasing autophagy, which indicated the therapeutic potential of TK under nutrient deprivation-associated stress conditions.
我们团队之前的研究表明，组织激肽释放酶（TK）在脑缺血期间发挥神经保护作用。自噬是细胞在营养缺乏时对细胞应激的一种重要适应性反应，已知β-连环蛋白可抑制自噬。本研究调查了在营养缺乏诱导的应激条件下，自噬和β-连环蛋白信号通路是否可能参与TK的保护作用。结果显示，在血清饥饿条件下，TK能促进SH-SY5Y细胞的存活并抑制其死亡，且以浓度依赖的方式增强自噬活性，这表现为轻链（LC）3-II水平和Beclin-1表达的增加。自噬抑制剂3-甲基腺嘌呤和NH4Cl消除了TK的保护作用。值得注意的是，尽管单独的血清饥饿和TK处理会增加p62蛋白水平和mRNA表达，但与溶酶体抑制剂NH4Cl共同孵育会增加LC3-II和p62蛋白的积累，表明自噬流正常。还观察到，TK处理可显著下调β-连环蛋白的表达。TK刺激了LC3与β-连环蛋白之间的相互作用，而NH4Cl消除了TK对血清饥饿细胞中β-连环蛋白水平的影响，这表明β-连环蛋白的自噬降解可能导致了自噬的增强。总之，本研究结果表明，TK通过增加自噬促进血清饥饿的SH-SY5Y细胞的存活和β-连环蛋白的降解，这表明TK在营养缺乏相关应激条件下具有治疗潜力。
