Endosomal accumulation of APP in wobbler motor neurons reflects impaired vesicle trafficking: Implications for human motor neuron disease
Endosomal accumulation of APP in wobbler motor neurons reflects impaired vesicle trafficking: Implications for human motor neuron disease
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DOI：
10.1186/1471-2202-12-24
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发表时间：
2011-03-07
期刊：
影响因子：
2.4
通讯作者：
Bartsch, Joerg W.
中科院分区：
文献类型：
--
作者：
Palmisano, Ralf;Golfi, Panagiota;Bartsch, Joerg W.
背景：散发性肌萎缩侧索硬化症(ALS)的病因目前尚不清楚，但有关疾病机制的假说包括氧化应激、轴突运输缺陷、线粒体功能障碍和RNA加工中断。家族性肌萎缩侧索硬化症是家族性肌萎缩侧索硬化症的良好代表，而小鼠突变型肌萎缩侧索硬化症(Wobbler，WR)由于Vps54基因点突变导致运动神经元进行性变性，为散发性肌萎缩侧索硬化症提供了一种动物模型。结果：在纯合子症状性WR小鼠的运动神经元中，大量的内体小泡明显增大(直径达3微米)，内体特异性的小GTP酶蛋白Rab7和淀粉样前体蛋白(APP)的免疫组织化学染色和超微结构分析表明，VPS54蛋白参与了囊泡的高尔基体转运；囊泡转运障碍也可能参与了ALS的发病。杂合子WR和转基因SOD1(G93A)小鼠均未检测到增大的囊泡；在WR运动神经元中观察到大量APP/Rab7阳性囊泡，大多为Lc3阴性，提示它们不是自噬。结论：内体APP/Rab7染色反映了WR小鼠运动神经元的囊泡运输受损。基于这些发现，对14例散发性ALS患者中6例的脊髓运动神经元进行了APP检测，并分析了ALS组织中增大的小泡内APP。家族性肌萎缩侧索硬化症患者中均未发现这些增大的小泡。因此，我们的研究为人类肌萎缩侧索硬化症的摇摆样病因提供了第一个证据，并建议应对参与囊泡运输的编码蛋白的基因进行病原性突变的筛查。
Background: The cause of sporadic amyotrophic lateral sclerosis (ALS) is largely unknown but hypotheses about disease mechanisms include oxidative stress, defective axonal transport, mitochondrial dysfunction and disrupted RNA processing. Whereas familial ALS is well represented by transgenic mutant SOD1 mouse models, the mouse mutant wobbler (WR) develops progressive motor neuron degeneration due to a point mutation in the Vps54 gene, and provides an animal model for sporadic ALS. VPS54 protein as a component of a protein complex is involved in vesicular Golgi trafficking; impaired vesicle trafficking might also be mechanistic in the pathogenesis of human ALS.Results: In motor neurons of homozygous symptomatic WR mice, a massive number of endosomal vesicles significantly enlarged (up to 3 mu m in diameter) were subjected to ultrastructural analysis and immunohistochemistry for the endosome-specific small GTPase protein Rab7 and for amyloid precursor protein (APP). Enlarged vesicles were neither detected in heterozygous WR nor in transgenic SOD1(G93A) mice; in WR motor neurons, numerous APP/Rab7-positive vesicles were observed which were mostly LC3-negative, suggesting they are not autophagosomes.Conclusions: We conclude that endosomal APP/Rab7 staining reflects impaired vesicle trafficking in WR mouse motor neurons. Based on these findings human ALS tissues were analysed for APP in enlarged vesicles and were detected in spinal cord motor neurons in six out of fourteen sporadic ALS cases. These enlarged vesicles were not detected in any of the familial ALS cases. Thus our study provides the first evidence for wobbler-like aetiologies in human ALS and suggests that the genes encoding proteins involved in vesicle trafficking should be screened for pathogenic mutations.