Abstract
The betaA4 peptide, a major component of senile plaques in Alzheimer's disease (AD) brain, has been found in cerebrospinal fluid (CSF) and blood of both AD patients and normal subjects. Although betaA4 1-40 is the major form produced by cell metabolism and found in CSF, recent observations suggest that the long-tailed betaA4 1-42 plays a more crucial role in AD pathogenesis. Here, we established new monoclonal antibodies against the C-terminal end of betaA4 1-40 and 1-42, and used them for the specific Western blot detection. After optimizing the assay conditions, these antibodies detected low picogram amount of betaA4, and both betaA4 1-40 and 1-42 levels in CSF could be determined by direct loading of the samples. Blood levels of betaA4 1-40 and 1-42 were also determined by specific immunoprecipitation followed by Western blot detection. We found that CSF betaA4 1-42 level is lower in AD patients compared with non-demented controls, although there was a significant overlap between the groups. The level of betaA4 1-40 in CSF, and of betaA4 1-40 as well as betaA4 1-42 in plasma, were not different between AD patients and controls. Besides the 4-kDa full-length betaA4 band, we could also detect several N-terminal variants of betaA4 in CSF and plasma of both AD patients and controls. Two N-terminally truncated betaA4 species migrating at the position of 3.3 and 3.7 kDa were found in CSF, while 3.7- and 5-kDa forms were found in plasma. The relative abundance of these various species were considerably different in the CSF and plasma, suggesting that the cellular source and/or clearance of betaA4 is different in these two compartments.
Highlights
A major neuropathological feature of Alzheimer’s disease (AD)1 is the presence of senile plaques in the brain
Establishment and Characterization of Monoclonal Antibodies against A4 —In order to obtain monoclonal antibodies (mAbs) which are specific for the different C termini of short-tailed and long-tailed A4, we immunized two mice with synthetic A4 33– 40 peptide and four mice with synthetic A4 35– 42 peptide, both conjugated to carrier protein
Amyloid deposition in the form of senile plaques is a central feature of AD pathology, the source of A4 in the deposits is not known
Summary
A major neuropathological feature of Alzheimer’s disease (AD)1 is the presence of senile plaques in the brain. Besides the 4-kDa full-length A4 band, we could detect several N-terminal variants of A4 in CSF and plasma of both AD patients and controls.
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