LOCATION OF AN EPITOPE SHARED BY ALZHEIMERS AMYLOID PEPTIDE AND BRAINCREATINE-KINASE USING A NEWLY DEVELOPED MONOCLONAL-ANTIBODY

Amyloid plaques, composed mainly by a peptide termed A4-amyloid, deriv ed by proteolytic processing from the amyloid precursor protein (APP), are a hallmark in the brain of Alzheimer's disease patients. We have prepared a collection of monoclonal antibodies as tools to study APP e xpression and proteolysis in different systems. One of these, 5AH10, r aised against residues 9-22 of A4-peptide, was selected for its abilit y to recognize only A4 subpeptides having the intact APP-secretase tar get sequence, as well as whole recombinant APP. By using synthetic sub peptides, we have located 5AH10 epitope between amino acids 15 and 22 of A4. In addition, 5AH10 showed a strong immunoreactivity to a 47 kDa protein present in rat brain extracts, that was identified as the B ( brain specific) subunit of creatine kinase by immunochemical data and direct N-terminal sequencing. The cross-reaction observed is most prob ably due to a high degree of sequence identity between amino acids 15 to 22 of A4 peptide and amino acids 9 to 16 of rat B creatine kinase. 5AH10 did not recognize the muscle specific isoform (M subunit) of rat creatine kinase, nor the B subunit of human and rabbit creatine kinas e, suggesting that glutamine at first position of the epitope is essen tial for antigen recognition by 5AH10.