Alpha-Synuclein affects neurite morphology, autophagy, vesicle transport and axonal degeneration in CNS neurons.
Alpha-Synuclein affects neurite morphology, autophagy, vesicle transport and axonal degeneration in CNS neurons.
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DOI：
10.1038/cddis.2015.169
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发表时间：
2015-07-09
影响因子：
9
通讯作者：
Lingor P
中科院分区：
文献类型：
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作者：
Koch JC;Bitow F;Haack J;d'Hedouville Z;Zhang JN;Tönges L;Michel U;Oliveira LM;Jovin TM;Liman J;Tatenhorst L;Bähr M;Lingor P
许多神经病理学和实验研究表明，黑质多巴胺能神经元的死亡是由于黑质多巴胺能神经末梢和轴突的变性，最终导致帕金森病（Parkinson disease，PD）的临床症状。然而，这种早期轴突变性的机制仍然知之甚少。在此，我们研究了过度表达人野生型α-突触核蛋白（αSyn-WT）（一种与PD相关的蛋白质）及其突变体α Syn-A30 P和-A53 T对大鼠原代中脑神经元（PMN）轴突形态和功能参数的影响。此外，在大鼠视神经中通过活体成像分析αSyn-WT和-A30 P过表达后的轴突变性。我们发现αSyn-WT及其突变体A30 P和A53 T的过表达损害了PMN的轴突生长，并以变体依赖的方式影响了Sholl分析评估的轴突分支。令人惊讶的是，在用αSyn转染的神经元中，每个神经元的初级神经突数量增加。轴突囊泡运输通过与EGFP标记的突触素共转染的PMN的活体成像来检查。与对照相比，所有αSyn变体的过表达显著减少了运动囊泡的数量，并减慢了囊泡的运输。αSyn-WT和α Syn-A53 T可增强PMN的巨噬细胞自噬流量，而α Syn-A30 P则无此作用。相应地，与其他αSyn变体相比，α Syn-A30 P的αSyn和自噬标志物LC 3的共定位减少。与LC 3共定位的线粒体数量作为线粒体自噬的标志物在各组之间没有差异。在大鼠视神经中，通过体内活体成像分析，αSyn-WT和-A30 P均加速挤压损伤后急性轴突变性的动力学。我们的结论是，αSyn过度表达损害神经突起的生长，并增加轴突变性，而轴突囊泡运输和自噬严重改变。
Many neuropathological and experimental studies suggest that the degeneration of dopaminergic terminals and axons precedes the demise of dopaminergic neurons in the substantia nigra, which finally results in the clinical symptoms of Parkinson disease (PD). The mechanisms underlying this early axonal degeneration are, however, still poorly understood. Here, we examined the effects of overexpression of human wildtype alpha-synuclein (αSyn-WT), a protein associated with PD, and its mutant variants αSyn-A30P and -A53T on neurite morphology and functional parameters in rat primary midbrain neurons (PMN). Moreover, axonal degeneration after overexpression of αSyn-WT and -A30P was analyzed by live imaging in the rat optic nerve in vivo. We found that overexpression of αSyn-WT and of its mutants A30P and A53T impaired neurite outgrowth of PMN and affected neurite branching assessed by Sholl analysis in a variant-dependent manner. Surprisingly, the number of primary neurites per neuron was increased in neurons transfected with αSyn. Axonal vesicle transport was examined by live imaging of PMN co-transfected with EGFP-labeled synaptophysin. Overexpression of all αSyn variants significantly decreased the number of motile vesicles and decelerated vesicle transport compared with control. Macroautophagic flux in PMN was enhanced by αSyn-WT and -A53T but not by αSyn-A30P. Correspondingly, colocalization of αSyn and the autophagy marker LC3 was reduced for αSyn-A30P compared with the other αSyn variants. The number of mitochondria colocalizing with LC3 as a marker for mitophagy did not differ among the groups. In the rat optic nerve, both αSyn-WT and -A30P accelerated kinetics of acute axonal degeneration following crush lesion as analyzed by in vivo live imaging. We conclude that αSyn overexpression impairs neurite outgrowth and augments axonal degeneration, whereas axonal vesicle transport and autophagy are severely altered.