Characterization of the glycosylation profiles of Alzheimer's beta-secretase protein Asp-2 expressed in a variety of cell lines

Amyloid 39-42 beta -peptides are the main components of amyloid plaques fou nd in the brain of Alzheimer's disease patients. Amyloid 39-42 beta -peptid e is formed from amyloid precursor protein by the sequential action of beta -and gamma -secretases. Asp-2 is a transmembrane aspartic protease express ed in the brain, shown to have beta -secretase activity. Mature Asp-2 has f our N-glycosylation sites. In this report we have characterized the carbohy drate structures in this glycoprotein expressed in three different cell lin es, namely Chinese hamster ovary, CV-1 origin of SV40, and baculovirus-infe cted SF9 cells. Biantennary and triantennary oligosaccharides of the "compl ex" type were released from glycoprotein expressed in the mammalian cells, whereas mannose-rich glycans were identified from glycoprotein synthesized in the baculovirus-infected cells. Site-directed mutagenesis of the asparag ine residues at amino acid positions 153, 172, 223, and 354 demonstrate tha t the protease activity of Asp-2 is dependent on its glycosylation.