Phospholipase D1 regulates autophagic flux and clearance of α-synuclein aggregates
Phospholipase D1 regulates autophagic flux and clearance of α-synuclein aggregates
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DOI：
10.1038/cdd.2014.30
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发表时间：
2014-07-01
影响因子：
12.4
通讯作者：
Lee, S-J
中科院分区：
文献类型：
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作者：
Bae, E-J;Lee, H-J;Lee, S-J
许多神经退行性疾病，例如阿尔茨海默病和帕金森病，其特征是聚集蛋白的异常积累。这些疾病中的大脑还显示出自噬囊泡在神经元细胞质中的积累，表明自噬过程受损。由于自噬涉及从头产生膜和囊泡融合，因此脂质分子的广泛变化是必要的。然而，信号脂质修饰酶在自噬中的参与及其在神经退行性疾病中的作用尚不清楚。使用特定的抑制剂，我们发现磷脂酶 D1 (PLD1) 活性的丧失会导致微管相关蛋白轻链 3 (LC3)、p62 和多聚泛素化蛋白的积累，这些迹象表明自噬流出现故障。荧光和电子显微镜分析表明自噬体与溶酶体的融合受损，导致自噬体积累。在自噬通量受损的细胞内，α-突触核蛋白聚集在自噬体中。使用小干扰 RNA 敲低 PLD1 表达也会导致自噬通量受损以及自噬体中 α-突触核蛋白聚集体的积累。 PLD1 的过度表达可以缓解由 α-突触核蛋白积累引起的神经元毒性；然而，活性缺陷突变体 PLD1-KRM 的表达显示救援效果降低。最后，我们证明路易体痴呆 (DLB) 患者脑组织中 PLD 活性和表达水平均降低，而同一组织样本中 α-突触核蛋白和 p62 的含量增加。总的来说，这些结果表明，PLD 活性不足以及膜内磷脂组成的变化可能是路易体疾病中自噬过程受损和蛋白质积累的重要原因。
Many neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease, are characterized by abnormal accumulations of aggregated proteins. Brains in these diseases also show accumulation of autophagic vesicles in the neuronal cytoplasm, suggesting impairment of the autophagic process. As autophagy involves de novo membrane production and vesicle fusion, extensive changes in lipid molecules are necessary. However, the involvement of signaling lipid-modifying enzymes in autophagy and their roles in neurodegenerative diseases are not clear. Using specific inhibitor, we show that loss of phospholipase D1 (PLD1) activity resulted in an accumulation of microtubule-associated protein light chain 3 (LC3), p62, and polyubiquitinated proteins, signs representing malfunction in autophagic flux. Fluorescence and electron microscopic analyses demonstrated impaired fusion of autophagosomes with lysosomes, resulting in accumulation of autophagosomes. Within the cells with impaired autophagic flux, alpha-synuclein aggregates accumulated in autophagosomes. Knockdown of PLD1 expression using small interfering RNA also resulted in impaired autophagic flux and accumulation of alpha-synuclein aggregates in autophagosomes. Neuronal toxicity caused by alpha-synuclein accumulation was rescued by overexpression of PLD1; however, expression of activity-deficient mutant, PLD1-KRM, showed reduced rescue effects. Finally, we demonstrated that both PLD activity and expression levels were reduced in brain tissues of dementia with Lewy bodies (DLB) patients, whereas the amounts of alpha-synuclein and p62 were increased in the same tissue samples. Collectively, these results suggest that insufficient PLD activity, and therefore, the changes in phospholipid compositions within membranes, might be an important contributor to impaired autophagic process and protein accumulation in Lewy body diseases.