CMT2B-associated Rab7 mutants inhibit neurite outgrowth
CMT2B-associated Rab7 mutants inhibit neurite outgrowth
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DOI：
10.1007/s00401-010-0696-8
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发表时间：
2010-10-01
影响因子：
12.7
通讯作者：
Bucci, Cecilia
中科院分区：
文献类型：
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作者：
Cogli, Laura;Progida, Cinzia;Bucci, Cecilia
腓骨肌萎缩症2B型（CMT2B）神经病是一种罕见的常染色体显性轴突疾病，其特征是远端无力、肌肉萎缩和明显的感觉丧失，通常伴有足部溃疡。CMT2B与Rab7蛋白的突变相关，Rab7蛋白是一种控制晚期内吞运输的小GT3。目前，尚不清楚这些突变如何导致神经病变。事实上，CMT2B选择性地影响神经元过程，尽管Rab7的普遍表达。因此，本研究的重点是这些疾病相关的突变是否对神经突生长产生影响。我们观察到在PC12和Neuro2A细胞系中所有CMT2B相关突变体表达后，神经突生长受到显著抑制。因此，我们的数据强烈支持以前的遗传数据，这些数据提出这些Rab7突变确实与CMT2B有因果关系。这些CMT2B相关Rab7突变体对神经突生长的抑制作用通过PC12细胞中生长相关蛋白43（GAP 43）和Neuro2A细胞中核神经元分化标记物NeuN的上调受损进行了生化证实。组成型活性Rab7突变体的表达与CMT2B相关Rab7突变体的表达具有相似的效果。这些CMT2B相关突变体的活性行为与其先前证明的增加的GTP负载一致，从而证实活性Rab7突变体负责CMT2B。我们的研究结果为CMT2B相关Rab7突变体在杂合子患者中覆盖野生型Rab7活性的能力提供了解释。因此，我们的数据表明，降低神经元中Rab7的活性可能是CMT2B的靶向治疗。
Charco-Marie-Tooth type 2B (CMT2B) neuropathy is a rare autosomal-dominant axonal disorder characterized by distal weakness, muscle atrophy, and prominent sensory loss often complicated by foot ulcerations. CMT2B is associated with mutations of the Rab7 protein, a small GTPase controlling late endocytic traffic. Currently, it is still unknown how these mutations cause the neuropathy. Indeed, CMT2B selectively affects neuronal processes, despite the ubiquitous expression of Rab7. Therefore, this study focused on whether these disorder-associated mutations exert an effect on neurite outgrowth. We observed a marked inhibition of neurite outgrowth upon expression of all the CMT2B-associated mutants in the PC12 and Neuro2A cell lines. Thus, our data strongly support previous genetic data which proposed that these Rab7 mutations are indeed causally related to CMT2B. Inhibition of neurite outgrowth by these CMT2B-associated Rab7 mutants was confirmed biochemically by impaired up-regulation of growth-associated protein 43 (GAP43) in PC12 cells and of the nuclear neuronal differentiation marker NeuN in Neuro2A cells. Expression of a constitutively active Rab7 mutant had a similar effect to the expression of the CMT2B-associated Rab7 mutants. The active behavior of these CMT2B-associated mutants is in line with their previously demonstrated increased GTP loading, thus confirming that active Rab7 mutants are responsible for CMT2B. Our findings provide an explanation for the ability of CMT2B-associated Rab7 mutants to override the activity of wild-type Rab7 in heterozygous patients. Thus, our data suggest that lowering the activity of Rab7 in neurons could be a targeted therapy for CMT2B.