ESSENTIAL ROLE FOR AUTOPHAGY PROTEIN ATG7 THE PREVENTION OF AXONAL DEGENERATION

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 自噬是一种受调控的溶酶体降解过程，涉及自噬小体的形成和运输。虽然最近的证据表明，基础水平的自噬可以防止神经退化，但发生这种情况的确切机制尚不清楚。通过使用条件性基因敲除突变小鼠，我们报告了神经元自噬对于维持轴突终末的局部动态平衡和防止轴突变性特别重要。我们发现，浦肯野细胞中一个重要的自噬基因ATG7的特定消融最初会导致细胞自主性、进行性营养不良(表现为轴突肿胀)和轴突终末的退化。与自噬抑制一致的是，在这些营养不良的肿胀中没有观察到自噬小体，这与病理情况下轴突营养不良肿胀中的自噬小体聚集形成对比。突变型浦肯野细胞的轴突营养不良几乎没有树突或棘突萎缩的迹象，这表明轴突终末比树突更容易受到自噬损害。轴突的这一早期病理事件之后是细胞自主性浦肯野细胞死亡和小鼠行为缺陷。此外，突变的浦肯野细胞的超微结构分析显示，在轴突营养不良的肿胀中积累了异常的膜结构。最后，我们在野生型浦肯野细胞轴突中观察到双膜空泡样结构，而在突变型浦肯野细胞轴突中这些结构被取消。因此，我们得出结论，自噬蛋白ATG7在轴突的膜运输和周转中是必需的。我们的研究表明轴突自噬功能受损可能是与神经变性相关的轴索病的一个可能机制。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Autophagy is a regulated lysosomal degradation process that involves autophagosome formation and transport. Although recent evidence indicates that basal levels of autophagy protect against neurodegeneration, the exact mechanism whereby this occurs is not known. By using conditional knockout mutant mice, we report that neuronal autophagy is particularly important for the maintenance of local homeostasis of axon terminals and protection against axonal degeneration. We show that specific ablation of an essential autophagy gene, Atg7, in Purkinje cells initially causes cell-autonomous, progressive dystrophy (manifested by axonal swellings) and degeneration of the axon terminals. Consistent with suppression of autophagy, no autophagosomes are observed in these dystrophic swellings, which is in contrast to accumulation of autophagosomes in the axonal dystrophic swellings under pathological conditions. Axonal dystrophy of mutant Purkinje cells proceeds with little sign of dendritic or spine atrophy, indicating that axon terminals are much more vulnerable to autophagy impairment than dendrites. This early pathological event in the axons is followed by cell-autonomous Purkinje cell death and mouse behavioral deficits. Furthermore, ultrastructural analyses of mutant Purkinje cells reveal an accumulation of aberrant membrane structures in the axonal dystrophic swellings. Finally, we observe double-membrane vacuole-like structures in wild-type Purkinje cell axons, whereas these structures are abolished in mutant Purkinje cell axons. Thus, we conclude that the autophagy protein Atg7 is required for membrane trafficking and turnover in the axons. Our study implicates impairment of axonal autophagy as a possible mechanism for axonopathy associated with neurodegeneration.