Selective neurotoxicity of COOH-terminal fragments of the beta-amyloid precursor protein.

The primary component of amyloid deposits found in the brains of patients with Alzheimer's disease is the beta-amyloid protein, a derivative of a much larger precursor protein (beta PP). We have previously reported that overexpression of carboxyl (COOH)-terminal fragments of beta PP from an integrated DNA construct leads to degeneration of neuronally differentiating mouse embryonic stem cells and that the neuronal degeneration is related to approximately 14- and 15-kDa COOH-terminal fragments of the precursor protein. We here demonstrate that these putative cytotoxic fragments contain intact beta-amyloid protein. When such transformed cell lines are treated with dimethyl sulfoxide to induce differentiation into muscle cells, however, the resulting muscle cells remain viable (as do control non-transformed cells), despite the production of comparable amounts of the 14- and 15-kDa fragments. These results are consistent with the hypothesis that particular COOH-terminal fragments of beta PP are amyloidogenic and neurotoxic.