The ALS disease protein TDP-43 is actively transported in motor neuron axons and regulates axon outgrowth
The ALS disease protein TDP-43 is actively transported in motor neuron axons and regulates axon outgrowth
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DOI：
10.1093/hmg/dds205
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发表时间：
2012-08-15
影响因子：
3.5
通讯作者：
Rossoll, Wilfried
中科院分区：
文献类型：
--
作者：
Fallini, Claudia;Bassell, Gary J.;Rossoll, Wilfried
肌萎缩侧索硬化症（ALS）是一种神经退行性疾病，特别是影响皮质和脊髓运动神经元。含有过度磷酸化和泛素化TDP-43的细胞质内含物是ALS的病理标志，编码TDP-43的基因突变与疾病的发展直接相关。TDP-43是一种普遍存在的DNA/RNA结合蛋白，在前体mRNA剪接中具有核作用。然而，ALS中运动神经元的选择性脆弱性和轴突变性提出了一个问题，即TDP-43是否可能在调节mRNA的细胞质和轴突命运中具有额外的作用，这对神经元功能很重要。为了研究这种可能性，我们的特点TDP-43的本地化和动力学在原代培养的运动神经元。使用细胞成像和生物化学技术相结合，我们证明，TDP-43是本地化的，并积极运输活运动神经元轴突，它与研究轴突mRNA结合蛋白共定位。TDP-43 C-末端片段的表达导致在运动神经元细胞体和神经突中形成过度磷酸化和泛素化的包涵体，并且这些包涵体特异性地隔离mRNA结合蛋白HuD。此外，我们发现，全长或突变TDP-43在运动神经元中的过表达引起轴突生长的严重损害，这取决于TDP-43的C-末端蛋白相互作用结构域。总之，我们的研究结果表明TDP-43在轴突生长的调节中的作用，并表明运动神经元细胞质中mRNA转录后调节的损伤可能是ALS发展的主要因素。
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease specifically affecting cortical and spinal motor neurons. Cytoplasmic inclusions containing hyperphosphorylated and ubiquitinated TDP-43 are a pathological hallmark of ALS, and mutations in the gene encoding TDP-43 have been directly linked to the development of the disease. TDP-43 is a ubiquitous DNA/RNA-binding protein with a nuclear role in pre-mRNA splicing. However, the selective vulnerability and axonal degeneration of motor neurons in ALS pose the question of whether TDP-43 may have an additional role in the regulation of the cytoplasmic and axonal fate of mRNAs, processes important for neuron function. To investigate this possibility, we have characterized TDP-43 localization and dynamics in primary cultured motor neurons. Using a combination of cell imaging and biochemical techniques, we demonstrate that TDP-43 is localized and actively transported in live motor neuron axons, and that it co-localizes with well-studied axonal mRNA-binding proteins. Expression of the TDP-43 C-terminal fragment led to the formation of hyperphosphorylated and ubiquitinated inclusions in motor neuron cell bodies and neurites, and these inclusions specifically sequestered the mRNA-binding protein HuD. Additionally, we showed that overexpression of full-length or mutant TDP-43 in motor neurons caused a severe impairment in axon outgrowth, which was dependent on the C-terminal protein-interacting domain of TDP-43. Taken together, our results suggest a role of TDP-43 in the regulation of axonal growth, and suggest that impairment in the post-transcriptional regulation of mRNAs in the cytoplasm of motor neurons may be a major factor in the development of ALS.