Superoxide dismutase in CSF from amyotrophic lateral sclerosis patients with and without CuZn-superoxide dismutase mutations.
Mutations in CuZn-superoxide dismutase (CuZn-SOD) have been linked to familial amyotrophic lateral sclerosis (ALS), and motor neurone death is caused by the gain of a toxic property of the mutant protein. Here we determined amounts, activity and molecular forms of CuZn-SOD in CSF from ALS patients carrying the D90A and other CuZn-SOD mutations and patients without such mutations. There were no differences in amount of protein and enzymic activities of CuZn-SOD between 37 neurological controls, 54 sporadic and 12 familial ALS cases, and 10 cases homozygous for the D90A mutation. Three cases heterozygous for the A89V, S105L and G114A CuZn-SOD mutations showed low amounts of CuZn-SOD. There was no evidence for accumulation of inactive protein in any of the groups. Immunoblots showed no evidence for the presence of any precipitates or other molecular forms of CuZn-SOD with higher molecular weight in the groups. About 25% of the CuZn-SOD subunits in CSF from controls shows an N-terminal truncation. This truncated portion does not differ between controls and ALS groups not carrying CuZn-SOD mutations, but is 70% larger in samples from D90A homozygous ALS patients. The findings suggest an essentially normal amount and activity of D90A mutant CuZn-SOD in CNS tissues of ALS cases. The increased occurrence of N-terminally truncated mutant subunits may indicate a difference in degradation routes compared with the wild-type enzyme, resistance against subsequent proteolytic steps and/or a compromised downstream proteolytic machinery. Molecular fragments accumulated to a greater extent from the D90A mutant enzyme might contribute to the motor neurone degeneration. We also determined the other SOD isoenzymes: in the controls, CuZn-SOD contributed 75%, extracellular SOD 25% and Mn-SOD <5% of the total SOD activity. There was no difference in the amount of extracellular SOD between any of the groups.
Jacobsson
J
J
Department of Pharmacology and Clinical Neurosciences and Department of Medical Biosciences, Clinical Chemistry, Umeå University Hospital, Umeå, Sweden.
Jonsson
P A
PA
Andersen
P M
PM
Forsgren
L
L
Marklund
S L
SL
D000328:Adult; D000367:Age Factors; D000368:Aged; D019943:Amino Acid Substitution; D000690:Amyotrophic Lateral Sclerosis / Q000134:cerebrospinal fluid* / Q000201:enzymology* / Q000235:genetics; D004789:Enzyme Activation / Q000235:genetics; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D015151:Immunoblotting; D007527:Isoenzymes / Q000134:cerebrospinal fluid / Q000235:genetics; D008875:Middle Aged; D008970:Molecular Weight; D009154:Mutation; D011499:Protein Processing, Post-Translational; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*
D007527:Isoenzymes; D013482:Superoxide Dismutase