An antibody to the β-secretase cleavage site on amyloid-β-protein precursor inhibits amyloid-β production

Proteolytic cleavage of amyloid-beta-protein precursor (AOPP) by beta- and gamma-secretases results in production of the amyloid-beta peptide (A beta) that accumulates in the brains of sufferers of Alzheimer's disease (AD). We have developed a monoclonal antibody, 2B12, which binds in the vicinity of the beta-secretase cleavage site on AOPP but does not bind within the A beta region. We hypothesised that this antibody, directed against the substrate rather than the enzyme, could inhibit cleavage of A beta PP by beta-secretase via steric hindrance and thus reduce downstream production of A beta. The antibody would enter cells by binding to A beta PP when it is at the cell surface and then be internalised with the protein. We subsequently demonstrated that, after addition of 2B12 to standard growth media, this antibody was indeed capable of inhibiting A beta 40 production in neuroblastoma and astrocytoma cells expressing native A beta PP, as measured by an ELISA. This inhibition was both concentration- and time-dependent and was specific to 2B12. We were only able to inhibit approximately 50% of A beta 40 production suggesting that Dot all A beta PP is trafficked to the cell surface. We propose that this antibody could be used as a novel, putative therapy for the treatment of AD.