| Abstrakt: |
Alterations of the axonal transport and microtubule network are potential causes of motor neurodegeneration in mice expressing a mutant form of the superoxide dismutase 1 (SOD1[sup G37R] ) linked to amyotrophic lateral sclerosis (ALS). In the present study, we investigated the biology of microtubule-associated proteins (MAPs), responsible for the formation and stabilization of microtubules, in SOD1[sup G37R] mice. Our results show that the protein levels of MAP2, MAP1A, tau 100 kDa and tau 68 kDa species decrease significantly as early as 5 months before onset of symptoms in the spinal cord of SOD1[sup G37R] mice, whereas decrease in levels of tau 52–55 kDa species is most often noted with the manifestation of the clinical symptoms. Interestingly, there was no change in the protein levels of MAPs in the brain of SOD1[sup G37R] mice, a CNS organ spared by the mutant SOD1 toxicity. Remarkably, as early as 5 months before disease onset, the binding affinities of MAP1A, MAP2 and tau isoforms to the cytoskeleton decreased in spinal cord of SOD1[sup G37R] mice. This change correlated with a hyperphosphorylation of the soluble tau 52–55 kDa species at epitopes recognized by the antibodies AT8 and PHF-1. Finally, a shift in the distribution of MAP2 from the cytosol to the membrane is detected in SOD1[sup G37R] mice at the same stage. Thus, alterations in the integrity of microtubules are early events of the neurodegenerative processes in SOD1[sup G37R] mice. [ABSTRACT FROM AUTHOR] |
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