title: Secretion and intracellular generation of truncated Abeta in beta-site amyloid-beta precursor protein-cleaving enzyme expressing human neurons.
abstract: Insoluble pools of the amyloid-beta peptide (Abeta) in brains of Alzheimer's disease patients exhibit considerable N- and C-terminal heterogeneity. Mounting evidence suggests that both C-terminal extensions and N-terminal truncations help precipitate amyloid plaque formation. Although mechanisms underlying the increased generation of C-terminally extended peptides have been extensively studied, relatively little is known about the cellular mechanisms underlying production of N-terminally truncated Abeta. Thus, we used human NT2N neurons to investigate the production of Abeta11-40/42 from amyloid-beta precursor protein (APP) by beta-site APP-cleaving enzyme (BACE). When comparing undifferentiated human embryonal carcinoma NT2- cells and differentiated NT2N neurons, the secretion of sAPP and Abeta correlated with BACE expression. To study the effects of BACE expression on endogenous APP metabolism in human cells, we overexpressed BACE in undifferentiated NT2- cells and NT2N neurons. Whereas NT2N neurons produced both full-length and truncated Abeta as a result of normal processing of endogenous APP, BACE overexpression increased the secretion of Abeta1-40/42 and Abeta11-40/42 in both NT2- cells and NT2N neurons. Furthermore, BACE overexpression resulted in increased intracellular Abeta1-40/42 and Abeta11-40/42. Therefore, we conclude that Abeta11-40/42 is generated prior to deposition in senile plaques and that N-terminally truncated Abeta peptides may contribute to the downstream effects of amyloid accumulation in Alzheimer's disease.
authors.affiliation: Center for Neurodegenerative Disease Research, Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Edward B
authors.initials: EB
authors.lastname: Lee
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Skovronsky
authors.forename: Farhad
authors.initials: F
authors.lastname: Abtahian
authors.forename: Robert W
authors.initials: RW
authors.lastname: Doms
authors.forename: Virginia M-Y
authors.initials: VM
authors.lastname: Lee
mesh_terms: D000544:Alzheimer Disease / Q000209:etiology / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000096:biosynthesis / Q000235:genetics; D016564:Amyloid beta-Protein Precursor / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D016282:Aspartic Acid Endopeptidases / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D009474:Neurons / Q000378:metabolism; D010446:Peptide Fragments / Q000096:biosynthesis / Q000235:genetics; D058225:Plaque, Amyloid / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D010446:Peptide Fragments; C078592:amyloid beta-protein (1-40); D016282:Aspartic Acid Endopeptidases