Mutation of potential N-linked glycosylation sites in the Alzheimer's disease amyloid precursor protein (APP)

In order to study the mechanism of intracellular sorting and processing of the Alzheimer's disease amyloid precursor protein (APP), we deleted two potential N-linked glycosylation sites of APP by site-directed mutagenesis. Substitution of alanines for the critical asparagine residues Asn467 and Asn496 was performed. Wild-type and mutant APPs were expressed in COS-1 cells by cDNA transfection and the expressed of the protein products and secretion of N-terminal large fragment was observed. The initial secretion of the mutant APP appeared to be slow compared with wild-type. In addition, we found that a distinct APP fragment, the cytosolic form, is transiently increased in the cytosol fraction of COS-1 cells. These results suggest that aberrant processing occurs following the expression of a mutant APP with Ala substituted for Asn, and that glycosylation may modulate the intracellular sorting of APP. (C) 1996 Elsevier Science Ireland Ltd.