自噬功能障碍由 ATG4B 的 S-亚硝化介导，导致高血糖反应中的神经毒性。
Autophagy impairment mediated by S-nitrosation of ATG4B leads to neurotoxicity in response to hyperglycemia.
机构信息
a National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules , Institute of Biophysics, Chinese Academy of Sciences , Beijing , China.
b University of Chinese Academy of Sciences , Beijing , China.
出版信息
Autophagy. 2017 Jul 3;13(7):1145-1160. doi: 10.1080/15548627.2017.1320467.
The majority of diabetic patients develop neuropathy and there is an increasing prevalence of neurodegeneration in the central nervous system (CNS). However, the mechanism behind this is poorly understood. Here we first observed that macroautophagy/autophagy was suppressed in the hippocampus of diabetic GK rats with hyperglycemia, whereas it was unchanged in ob/ob mice without hyperglycemia. Autophagy could be directly inhibited by high glucose in mouse primary hippocampal neurons. Moreover, autophagy was protective in high-glucose-induced neurotoxicity. Further studies revealed that autophagic flux was suppressed by high glucose due to impaired autophagosome synthesis illustrated by mRFP-GFP-LC3 puncta analysis. We showed that decreased autophagy was dependent on NO produced under high glucose conditions. Therefore, (LC-MS/MS)-based quantitative proteomic analysis of protein S-nitrosation was performed and a core autophagy protein, ATG4B was found to be S-nitrosated in the hippocampus of GK rats. ATG4B was also verified to be S-nitrosated in neuronal cells cultured with high glucose. The activities of ATG4B in the processing of unmodified, precursor Atg8-family proteins and in the deconjugation of PE from lipidated Atg8-family proteins, which are essential for efficient autophagosome biogenesis were both compromised by S-nitrosation at Cys189 and Cys292 sites. In addition, ATG4B processing of the GABARAPL1 precursor was affected the least by S-nitrosation compared with other substrates. Finally, ATG4B S-nitrosation was verified to be responsible for decreased autophagy and neurotoxicity in response to high glucose. In conclusion, autophagy impairment mediated by S-nitrosation of ATG4B leads to neurotoxicity in response to hyperglycemia. Our research reveals a novel mechanism linking hyperglycemia with CNS neurotoxicity and shows that S-nitrosation is a novel post-transcriptional modification of the core autophagy machinery.
大多数糖尿病患者会出现神经病变，中枢神经系统（CNS）的神经退行性变也越来越普遍。然而，其背后的机制尚不清楚。在这里，我们首先观察到高血糖的 GK 糖尿病大鼠海马中的巨自噬/自噬受到抑制，而没有高血糖的 ob/ob 小鼠则没有变化。高葡萄糖可直接抑制小鼠原代海马神经元中的自噬。此外，自噬在高葡萄糖诱导的神经毒性中具有保护作用。进一步的研究表明，由于高葡萄糖条件下自噬体合成受损，通过 mRFP-GFP-LC3 斑点分析显示自噬流受到抑制。我们表明，由于高葡萄糖条件下产生的 NO 减少，自噬减少是依赖的。因此，对蛋白质 S-亚硝基化的（LC-MS/MS）-基于定量蛋白质组学分析进行了研究，并且发现核心自噬蛋白 ATG4B 在 GK 大鼠海马中被 S-亚硝基化。还在高葡萄糖培养的神经元细胞中验证了 ATG4B 被 S-亚硝基化。在未修饰、前体 Atg8 家族蛋白的加工和从脂化的 Atg8 家族蛋白上除去 PE 的去共轭作用中，ATG4B 的活性对于有效的自噬体生物发生都是必不可少的，这两种作用都受到 Cys189 和 Cys292 位点的 S-亚硝基化的损害。此外，与其他底物相比，S-亚硝基化对 GABARAPL1 前体的 ATG4B 加工影响最小。最后，验证了 ATG4B 的 S-亚硝基化是对高葡萄糖反应中自噬减少和神经毒性负责的。总之，ATG4B 的 S-亚硝基化介导的自噬损伤导致高血糖反应中的神经毒性。我们的研究揭示了一种将高血糖与中枢神经系统神经毒性联系起来的新机制，并表明 S-亚硝基化是核心自噬机制的一种新的转录后修饰。
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