Autophagy induction and autophagosome clearance in neurons: relationship to autophagic pathology in Alzheimer's disease.
Autophagy induction and autophagosome clearance in neurons: relationship to autophagic pathology in Alzheimer's disease.
复制标题
神经元中的自噬诱导和自噬体清除：与阿尔茨海默氏病自噬病理学的关系。
DOI：
10.1523/jneurosci.0800-08.2008
复制
发表时间：
2008-07-02
影响因子：
5.3
通讯作者：
Nixon, Ralph A.
中科院分区：
文献类型：
--
作者：
Boland, Barry;Kumar, Asok;Lee, Sooyeon;Platt, Frances M.;Wegiel, Jerzy;Yu, W. Haung;Nixon, Ralph A.
关键词：
自噬是细胞器和蛋白质更新的主要途径，与阿尔茨海默病（AD）的神经退行性变有关。然而，AD脑中受影响神经元中自噬空泡（AV）大量积累的基础尚不清楚。在这项研究中，我们表明，原代皮层神经元中的组成性巨自噬是高效的，因为新形成的自噬体通过与溶酶体融合而迅速清除，这是它们在健康大脑中稀缺的原因。即使在通过用雷帕霉素或营养剥夺抑制mTOR激酶活性强烈诱导大自噬后，活性组织蛋白酶阳性自噬溶酶体而不是LC 3-II阳性自噬体占主导地位，这意味着在健康神经元中有效的自噬体清除。相比之下，通过用半胱氨酸和乙酰基蛋白酶抑制剂抑制自噬体内组织蛋白酶介导的蛋白水解来选择性地阻止大自噬的后期步骤，导致电子致密的双膜限制性AV的显著积累，所述AV含有组织蛋白酶D和不完全降解的LC 3-II在胞体和神经突中。当用长春碱破坏自噬体在微管上的转运而减慢自噬体与溶酶体的融合时，类似的结构大量积累。最后，我们发现蛋白酶抑制或长春碱长期治疗后积累的自噬空泡与AD脑和AD小鼠模型中营养不良神经突中收集的AV非常相似。我们的结论是，macroautophagy是组成性的活跃和高效的健康神经元，和AD中观察到的自噬病理学最有可能来自受损的清除AV，而不是强大的自噬诱导单独。因此，AD中自噬的治疗调节可能需要靶向自噬途径中的晚期步骤。
Macroautophagy, a major pathway for organelle and protein turnover, has been implicated in the neurodegeneration of Alzheimer's disease (AD). The basis for the profuse accumulation of autophagic vacuoles (AVs) in affected neurons of the AD brain, however, is unknown. In this study, we show that constitutive macroautophagy in primary cortical neurons is highly efficient, as newly formed autophagosomes are rapidly cleared by fusion with lysosomes, accounting for their scarcity in the healthy brain. Even after macroautophagy is strongly induced by suppressing mTOR kinase activity with rapamycin or nutrient deprivation, active cathepsin-positive autolysosomes rather than LC3-II-positive autophagosomes predominate, implying efficient autophagosome clearance in healthy neurons. By contrast, selectively impeding late steps in macroautophagy by inhibiting cathepsin-mediated proteolysis within autophagosomes with cysteine- and aspartyl-protease inhibitors caused a marked accumulation of electron-dense double membrane-limited AVs, containing cathepsin D and incompletely degraded LC3-II in perikarya and neurites. Similar structures accumulated in large numbers when fusion of autophagosomes with lysosomes was slowed by disrupting their transport on microtubules with vinblastine. Finally, we find that the autophagic vacuoles accumulating after protease inhibition or prolonged vinblastine treatment strongly resembled AVs that collect in dystrophic neurites in the AD brain and in an AD mouse model. We conclude that macroautophagy is constitutively active and highly efficient in healthy neurons, and that the autophagic pathology observed in AD most likely arises from impaired clearance of AVs rather than strong autophagy induction alone. Therapeutic modulation of autophagy in AD may, therefore, require targeting late steps in the autophagic pathway.