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Disruption of Axonal Transport in Motor Neuron Diseases
Department of Neurology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan
Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Saitama 332-0012, Japan
* Authors to whom correspondence should be addressed.
Received: 2 November 2011; in revised form: 11 January 2012 / Accepted: 16 January 2012 / Published: 23 January 2012
Abstract: Motor neurons typically have very long axons, and fine-tuning axonal transport is crucial for their survival. The obstruction of axonal transport is gaining attention as a cause of neuronal dysfunction in a variety of neurodegenerative motor neuron diseases. Depletions in dynein and dynactin-1, motor molecules regulating axonal trafficking, disrupt axonal transport in flies, and mutations in their genes cause motor neuron degeneration in humans and rodents. Axonal transport defects are among the early molecular events leading to neurodegeneration in mouse models of amyotrophic lateral sclerosis (ALS). Gene expression profiles indicate that dynactin-1 mRNA is downregulated in degenerating spinal motor neurons of autopsied patients with sporadic ALS. Dynactin-1 mRNA is also reduced in the affected neurons of a mouse model of spinal and bulbar muscular atrophy, a motor neuron disease caused by triplet CAG repeat expansion in the gene encoding the androgen receptor. Pathogenic androgen receptor proteins also inhibit kinesin-1 microtubule-binding activity and disrupt anterograde axonal transport by activating c-Jun N-terminal kinase. Disruption of axonal transport also underlies the pathogenesis of spinal muscular atrophy and hereditary spastic paraplegias. These observations suggest that the impairment of axonal transport is a key event in the pathological processes of motor neuron degeneration and an important target of therapy development for motor neuron diseases.
Keywords: axonal transport; dynactin-1; dynein; kinesin; neurofilament; motor neuron; amyotrophic lateral sclerosis; spinal and bulbar muscular atrophy; spinal muscular atrophy; hereditary spastic paraplegia
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Ikenaka, K.; Katsuno, M.; Kawai, K.; Ishigaki, S.; Tanaka, F.; Sobue, G. Disruption of Axonal Transport in Motor Neuron Diseases. Int. J. Mol. Sci. 2012, 13, 1225-1238.
Ikenaka K, Katsuno M, Kawai K, Ishigaki S, Tanaka F, Sobue G. Disruption of Axonal Transport in Motor Neuron Diseases. International Journal of Molecular Sciences. 2012; 13(1):1225-1238.
Ikenaka, Kensuke; Katsuno, Masahisa; Kawai, Kaori; Ishigaki, Shinsuke; Tanaka, Fumiaki; Sobue, Gen. 2012. "Disruption of Axonal Transport in Motor Neuron Diseases." Int. J. Mol. Sci. 13, no. 1: 1225-1238.