The Roslin Institute & R(D)SVS, University of Edinburgh, Easter Bush, Midlothian, EH25 9RG, UK.
Centre for Dementia Prevention, University of Edinburgh, Edinburgh, UK.
Sci Rep. 2018 Jul 3;8(1):10004. doi: 10.1038/s41598-018-28296-y.
Autolysosomal dysfunction and unstable microtubules are hallmarks of chronic neurodegenerative diseases associated with misfolded proteins. Investigation of impaired protein quality control and clearance systems could therefore provide an important avenue for intervention. To investigate this we have used a highly controlled model for protein aggregation, an in vitro prion system. Here we report that prion aggregates traffic via autolysosomes in the cytoplasm. Treatment with the natural polyamine spermine clears aggregates by enhancing autolysosomal flux. We demonstrated this by blocking the formation of mature autophagosomes resulting in accumulation of prion aggregates in the cytoplasm. Further we investigated the mechanism of spermine's mode of action and we demonstrate that spermine increases the acetylation of microtubules, which is known to facilitate retrograde transport of autophagosomes from the cellular periphery to lysosomes located near the nucleus. We further report that spermine facilitates selective autophagic degradation of prion aggregates by binding to microtubule protein Tubb6. This is the first report in which spermine and the pathways regulated by it are applied as a novel approach towards clearance of misfolded prion protein and we suggest that this may have important implication for the broader family of protein misfolding diseases.
自噬溶酶体功能障碍和不稳定的微管是与错误折叠蛋白相关的慢性神经退行性疾病的标志。因此，研究受损的蛋白质质量控制和清除系统可能为干预提供一个重要途径。为了研究这一点，我们使用了一种高度可控的蛋白质聚集模型，即体外朊病毒系统。在这里，我们报告说朊病毒聚集体通过细胞质中的自噬溶酶体运输。用天然多胺亚精胺处理可通过增强自噬溶酶体流来清除聚集体。我们通过阻断成熟自噬体的形成来证明这一点，导致朊病毒聚集体在细胞质中积累。此外，我们研究了亚精胺作用机制，证明亚精胺增加了微管的乙酰化，这已知有助于自噬体从细胞外周向位于细胞核附近的溶酶体的逆行运输。我们进一步报告说，亚精胺通过与微管蛋白 Tubb6 结合促进朊病毒聚集体的选择性自噬降解。这是首次报道亚精胺及其调节途径被应用于清除错误折叠的朊病毒蛋白的新方法，我们认为这可能对更广泛的蛋白质错误折叠疾病家族具有重要意义。
