A NOVEL AMYLOID COMPONENT

淀粉样蛋白作为老年斑的核心和沿着血管壁积累

Amyloid accumulates as a core of senile plaques and along the vessel wall in the brain tissue of patients afflicted with Alzheimer's disease (AD). The major constituent of amyloid is a 39-43 amino acid peptide called amyloid Beta/A4-protein (A/Beta) derived from a precursor of around 100,000 daltons. Recent immunological studies have demonstrated many acute phase proteins are associated with amyloid, raising the possibility that amyloid might be composed of more than one type of protein. However, biochemically, Abeta had remained the only component identified for many years. However, recently, we have identified a new component in an AD amyloid biochemically and propose to study this protein using molecular biological, biochemical, immunological, and cell biological techniques. The complete digestion of purified AD amyloid, solubilized in 70% formic acid, and digested by cyanogen bromide and Achromobacter lyticus protease I yielded, in addition to ABeta fragments, two peptides of unknown sequence. These sequences were used to raise antisera. Two antisera portion of these sequences was used to generate oligonucleotide that were used by PCR to amplify DNA fragments from a brain cDNA library. A 247- nucleotide DNA segment was amplified. The sequencing of this short DNA demonstrated that this DNA encodes a protein that contains a perfect match with the peptide sequence found n amyloid. A full-length cDNA for the protein containing both two new amyloid sequence was isolated using this PCR amplified probe. We call the protein containing these peptide NACP for further immunohistochemical and immunochemical analysis of this protein. Antisense strategy will be used to identify the biological function of NACP. Finally, potential interaction between NAC or NACP and APP or Abeta will be investigated. Characterization of NAC and NACP should shed further light on the amyloidogenesis in AD and might help in finding the etiology of this devastating disease.