Overexpression of amyloid precursor protein A4 (beta-amyloid) immunoreactivity in genetically transformed cells: implications for a cellular model of Alzheimer amyloidosis.

Among the major obstacles to clarifying molecular mechanisms involved in amyloid metabolism in Alzheimer disease has been the unavailability of laboratory models for this uniquely human disorder. The present studies were aimed at establishing genetically engineered cell lines that overexpress amyloid immunoreactivity and that may be relevant to amyloid accumulation in the Alzheimer disease brain. We used cloned amyloid cDNA that contains a region encoding A4 (beta-polypeptide) amino acids along with recently developed tumor virus vectors derived from simian virus 40 to prepare transformed cells. After transient and permanent transfection, a variety of cell types overexpressed A4 immunoreactivity that was detected by highly specific monoclonal antibodies. We observed that the use of an amyloid subdomain containing the A4 region, but lacking the sequence of a Kunitz-type protease inhibitor found in amyloid precursor protein variants, was sufficient to obtain cells that overproduced an A4 epitope. The transformed cells were readily propagated in culture and may provide an experimental medium to elucidate aspects of the molecular pathogenesis of Alzheimer disease. The cellular models may also serve as tools for deriving potentially useful therapeutic agents.