Mutation of Glu693 to Gln or Val717 to Ile has no effect on the processing of Alzheimer amyloid precursor protein expressed in COS-1 cells by cDNA transfection.

One of the features of Alzheimer's disease (AD) is the formation of senile plaques, of which the main component is a 42 amino acid beta-protein (beta P). Molecular cloning of beta P revealed the presence of a 90-130 kDa precursor, amyloid precursor protein (APP). Since APP is expressed in normal brain without producing beta P, some abnormal processing is the cause of the formation of beta P in AD. Two kinds of mutations of APP, Glu693 to Gln and Val717 to Ile, were reported in AD-related diseases. Site-directed mutagenesis was applied, and the mutated APPs were expressed in COS-1 cells by cDNA transfection. They showed apparently the same processing as wild APP. This means that these mutations might not be a direct cause for the abnormal processing of APP or the formation of beta P in AD.