Accumulation of human SOD1 and ubiquitinated deposits in the spinal cord of SOD1G93A mice during motor neuron disease progression correlates with a decrease of proteasome

• Published in: Neurobiology of disease Vol. 18; no. 3; pp. 509 - 522
• Main Authors: Cheroni, C., Peviani, M., Cascio, P., DeBiasi, S., Monti, C., Bendotti, C.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.04.2005; Elsevier
• Subjects: Alanine - genetics; Amino Acid Substitution - genetics; Amyotrophic lateral sclerosis; Animals; Female; Glycine - genetics; Humans; Mice; Mice, Inbred C57BL; Mice, Transgenic; Motor Neuron Disease - enzymology; Motor Neuron Disease - genetics; Motor Neuron Disease - metabolism; Motor neurons; Proteasome; Proteasome Endopeptidase Complex - genetics; Proteasome Endopeptidase Complex - metabolism; Protein aggregates; SOD1G93A transgenic mouse model; Solubility; Spinal Cord - chemistry; Spinal Cord - enzymology; Spinal Cord - metabolism; Superoxide Dismutase - biosynthesis; Superoxide Dismutase - genetics; Superoxide Dismutase - metabolism; Superoxide Dismutase-1; Ubiquitin; Ubiquitin - metabolism; Ubiquitin; Motor neurons; Amyotrophic lateral sclerosis; SOD1G93A transgenic mouse model; Protein aggregates; Proteasome
• ISSN: 0969-9961; 1095-953X
• DOI: 10.1016/j.nbd.2004.12.007

Mutations in SOD1 cause selective motor neuron degeneration in familial amyotrophic lateral sclerosis patients and transgenic mice overexpressing the mutant enzyme. Formation and accumulation of ubiquitinated aggregates in motor neurons are thought to be involved in the toxic gain of function of mutant SOD1. The present study shows that the accumulation of soluble and detergent-insoluble mutant SOD1 in spinal cord of symptomatic SOD1G93A transgenic mice is due to impaired degradation of mutant SOD1 rather than to increased transcript levels. This effect was accompanied by a decrease of constitutive proteasome levels and a concomitant increase of immunoproteasome in the spinal cord homogenate which resulted in overall unchanged proteasome activity. A decrease of constitutive proteasome occurred in the motor neurons of SOD1G93A mice at the presymptomatic stage and became remarkable with the progression of the disease. This provides further evidence for an involvement of proteasome impairment in the toxicity of mutant SOD1.