Tang Jing, Sun Fei, Deng Xiao-Juan, Ma Yuan-Lin, Li Kun-Yi, Tang Ying, Chen Guo-Jun
Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, 1 Youyi Road, Chongqing 400016, China.
Department of Physiology, Wayne State University School of Medicine, Detroit, MI, 48201, USA.
Genes Dis. 2019 May 25;7(3):401-407. doi: 10.1016/j.gendis.2019.05.003. eCollection 2020 Sep.
Vps34 (vacuolar protein-sorting 34) plays important role in autophagy and endosomal trafficking. These processes are closely associated protein ubiquitination and degradation. We have hypothesized that Vps34 ubiquitination status would also control its degradation. Here, we report that our results did not support this assumption. In cells transiently transfected with ubiquitin (UB) constructs contained different lysine residues (Ks), Vps34 ubiquitination could occur regardless of the presence of any Ks in UB. However, Vps34 protein levels were not significantly altered in cells transiently transfected with these UB mutants. We further found that Vps34 protein was altered by pharmacological manipulation of E2/E3 activity; yet this effect was not significantly affected by UB overexpression. In vivo experiments revealed that in APP/PS1 mice, an animal model of Alzheimer's disease (AD), although ubiquitination of Vps34 was significantly reduced, Vps34 protein levels remained unchanged. Vps34 indeed was subjected to proteasomal or lysosomal degradation, as prolonged treatment of proteasomal inhibitor MG132 or lysosomal inhibitor chloroquine elevated Vps34 protein levels. We conclude that unlike most of other proteins, Vps34 ubiquitination is not closely associated with its degradation.
Vps34（液泡蛋白分选蛋白34）在自噬和内体运输中发挥重要作用。这些过程与蛋白质泛素化和降解密切相关。我们推测Vps34的泛素化状态也会控制其降解。在此，我们报告我们的结果不支持这一假设。在瞬时转染了含有不同赖氨酸残基（Ks）的泛素（UB）构建体的细胞中，无论UB中是否存在任何Ks，Vps34都可能发生泛素化。然而，在用这些UB突变体瞬时转染的细胞中，Vps34蛋白水平没有显著改变。我们进一步发现，通过对E2/E3活性进行药理学操作可改变Vps34蛋白水平；但这种效应不受UB过表达的显著影响。体内实验表明，在阿尔茨海默病（AD）动物模型APP/PS1小鼠中，尽管Vps34的泛素化显著降低，但其蛋白水平保持不变。Vps34确实会经历蛋白酶体或溶酶体降解，因为蛋白酶体抑制剂MG132或溶酶体抑制剂氯喹的长期处理会提高Vps34蛋白水平。我们得出结论，与大多数其他蛋白质不同，Vps34的泛素化与其降解没有密切关联。
