PDF(Pubmed)
Abstract：
Autophagy is a conserved, multi-step process of capturing proteolytic cargo in autophagosomes for lysosome degradation. The capacity to remove toxic proteins that accumulate in neurodegenerative disorders attests to the disease-modifying potential of the autophagy pathway. However, neurons respond only marginally to conventional methods for inducing autophagy, limiting efforts to develop therapeutic autophagy modulators for neurodegenerative diseases. The determinants underlying poor autophagy induction in neurons and the degree to which neurons and other cell types are differentially sensitive to autophagy stimuli are incompletely defined. Accordingly, we sampled nascent transcript synthesis and stabilities in fibroblasts, induced pluripotent stem cells (iPSCs), and iPSC-derived neurons (iNeurons), thereby uncovering a neuron-specific stability of transcripts encoding myotubularin-related phosphatase 5 (MTMR5). MTMR5 is an autophagy suppressor that acts with its binding partner, MTMR2, to dephosphorylate phosphoinositides critical for autophagy initiation and autophagosome maturation. We found that MTMR5 is necessary and sufficient to suppress autophagy in iNeurons and undifferentiated iPSCs. Using optical pulse labeling to visualize the turnover of endogenously encoded proteins in live cells, we observed that knockdown of MTMR5 or MTMR2, but not the unrelated phosphatase MTMR9, significantly enhances neuronal degradation of TDP-43, an autophagy substrate implicated in several neurodegenerative diseases. Our findings thus establish a regulatory mechanism of autophagy intrinsic to neurons and targetable for clearing disease-related proteins in a cell-type-specific manner. In so doing, our results not only unravel novel aspects of neuronal biology and proteostasis but also elucidate a strategy for modulating neuronal autophagy that could be of high therapeutic potential for multiple neurodegenerative diseases.
摘要：
自噬是一种保守的,在自噬体中捕获蛋白水解货物以进行溶酶体降解的多步骤过程。清除神经退行性疾病中积累的有毒蛋白质的能力证明了自噬途径的疾病修饰潜力。然而,神经元仅对诱导自噬的常规方法反应轻微，限制开发治疗性自噬调节剂治疗神经退行性疾病的努力。神经元中弱自噬诱导的决定因素以及神经元和其他细胞类型对自噬刺激的差异敏感程度是不完全确定的。因此，我们采样了成纤维细胞的新生转录物合成和稳定性，诱导多能干细胞（iPSCs），和iPSC衍生的神经元（iNeuons），从而揭示了编码肌管蛋白相关磷酸酶5（MTMR5）的转录本的神经元特异性稳定性。MTMR5是一种自噬抑制剂，与其结合伴侣起作用，MTMR2，去磷酸化对自噬启动和自噬成熟至关重要的磷酸肌醇。我们发现MTMR5对于抑制iNeuons和未分化iPSCs中的自噬是必要且足够的。使用光脉冲标记来可视化活细胞中内源性编码蛋白质的周转，我们观察到,敲低MTMR5或MTMR2,而非无关磷酸酶MTMR9,显著增强了TDP-43的神经元降解,TDP-43是一种与多种神经退行性疾病有关的自噬底物.因此，我们的发现建立了神经元固有的自噬调节机制，并以细胞类型特异性方式靶向清除疾病相关蛋白。这样做,我们的研究结果不仅揭示了神经元生物学和蛋白稳定的新方面,而且阐明了调节神经元自噬的策略,该策略可能对多种神经退行性疾病具有很高的治疗潜力.
