Neurodegenerative Diseases Research Group, Vall d'Hebron Research Institute-Center for Networked Biomedical Research on Neurodegenerative Diseases (CIBERNED), Barcelona 08035, Spain.
J Neurosci. 2010 Sep 15;30(37):12535-44. doi: 10.1523/JNEUROSCI.1920-10.2010.
Mounting evidence suggests a role for autophagy dysregulation in Parkinson's disease (PD). The bulk degradation of cytoplasmic proteins (including α-synuclein) and organelles (such as mitochondria) is mediated by macroautophagy, which involves the sequestration of cytosolic components into autophagosomes (AP) and its delivery to lysosomes. Accumulation of AP occurs in postmortem brain samples from PD patients, which has been widely attributed to an induction of autophagy. However, the cause and pathogenic significance of these changes remain unknown. Here we found in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mouse model of PD that AP accumulation and dopaminergic cell death are preceded by a marked decrease in the amount of lysosomes within dopaminergic neurons. Lysosomal depletion was secondary to the abnormal permeabilization of lysosomal membranes induced by increased mitochondrial-derived reactive oxygen species. Lysosomal permeabilization resulted in a defective clearance and subsequent accumulation of undegraded AP and contributed directly to neurodegeneration by the ectopic release of lysosomal proteases into the cytosol. Lysosomal breakdown and AP accumulation also occurred in PD brain samples, where Lewy bodies were strongly immunoreactive for AP markers. Induction of lysosomal biogenesis by genetic or pharmacological activation of lysosomal transcription factor EB restored lysosomal levels, increased AP clearance and attenuated 1-methyl-4-phenylpyridinium-induced cell death. Similarly, the autophagy-enhancer compound rapamycin attenuated PD-related dopaminergic neurodegeneration, both in vitro and in vivo, by restoring lysosomal levels. Our results indicate that AP accumulation in PD results from defective lysosomal-mediated AP clearance secondary to lysosomal depletion. Restoration of lysosomal levels and function may thus represent a novel neuroprotective strategy in PD.
越来越多的证据表明自噬失调在帕金森病（PD）中起作用。细胞质蛋白（包括α-突触核蛋白）和细胞器（如线粒体）的大量降解是通过巨自噬介导的，巨自噬涉及将细胞质成分隔离到自噬体（AP）中，并将其递送至溶酶体。PD 患者死后大脑样本中出现的 AP 积累，这被广泛归因于自噬的诱导。然而，这些变化的原因和发病意义仍然未知。在这里，我们在 1-甲基-4-苯基-1,2,3,6-四氢吡啶（MPTP）诱导的 PD 小鼠模型中发现，AP 积累和多巴胺能神经元死亡之前，多巴胺能神经元内溶酶体数量明显减少。溶酶体耗竭是由于线粒体衍生的活性氧增加引起的溶酶体膜异常通透性引起的。溶酶体通透性导致未降解的 AP 清除缺陷和随后的积累，并通过溶酶体蛋白酶异常释放到细胞质中直接导致神经退行性变。溶酶体破裂和 AP 积累也发生在 PD 脑样本中，Lewy 体强烈免疫反应性地表达 AP 标志物。通过遗传或药理学激活溶酶体转录因子 EB 诱导溶酶体生物发生，恢复了溶酶体水平，增加了 AP 清除，并减轻了 1-甲基-4-苯基吡啶诱导的细胞死亡。同样，自噬增强化合物雷帕霉素通过恢复溶酶体水平，在体外和体内均减轻了与 PD 相关的多巴胺能神经退行性变。我们的研究结果表明，PD 中 AP 的积累是由于溶酶体耗竭导致的缺陷性溶酶体介导的 AP 清除所致。因此，恢复溶酶体水平和功能可能是 PD 的一种新的神经保护策略。
