title: Intracellularly generated amyloid-beta peptide counteracts the antiapoptotic function of its precursor protein and primes proapoptotic pathways for activation by other insults in neuroblastoma cells.
abstract: Most mutations in amyloid precursor proteins (APPs) linked to early onset familial Alzheimer's disease (FAD) increase the production of amyloid-beta peptides ending at residue 42 (Abeta42), which are released from APP by beta- and gamma-secretase cleavage. Stably transfected cells expressing wild-type human APP (APP(WT)) were more resistant to apoptosis-inducing treatments than cells expressing FAD-mutant human APP (APP(FAD)). Preventing Abeta42 production with an M596I mutation (beta-), which blocks beta-secretase cleavage of APP, or by treatment with a gamma-secretase inhibitor increased the resistance of APP(FAD)-expressing cells to apoptosis. Exposing hAPP(FAD/beta-) cells to exogenous Abeta42 or conditioned medium from Abeta42-producing APP(FAD) cells did not diminish their resistance to apoptosis. Preventing APP from entering the distal secretory pathway, where most Abeta peptides are generated, by retaining APP in the endoplasmic reticulum (ER)/intermediate compartment (IC) increased the resistance of APP(FAD)-expressing cells to apoptosis and did not alter the resistance of APP(WT)-expressing cells. p53-mediated gene transactivation after apoptosis-inducing treatments was much stronger in APP(FAD) cells than in hAPP(WT) or hAPP(FAD/beta-) cells. In contrast, upon induction of ER stress, cells expressing APP(FAD), hAPP(FAD/beta-), or APP(WT) had comparable levels of glucose-regulated protein-78 mRNA, an unfolded protein response indicator. We conclude that Abeta, especially intracellular Abeta, counteracts the antiapoptotic function of its precursor protein and predisposes cells to p53-mediated, and possibly other, proapoptotic pathways.
authors.affiliation: Gladstone Institute of Neurological Disease, Department of Neurology, University of California, San Francisco, California, USA.
authors.forename: Luke
authors.initials: L
authors.lastname: Esposito
authors.forename: Li
authors.initials: L
authors.lastname: Gan
authors.forename: Gui-Qiu
authors.initials: GQ
authors.lastname: Yu
authors.forename: Christian
authors.initials: C
authors.lastname: Essrich
authors.forename: Lennart
authors.initials: L
authors.lastname: Mucke
mesh_terms: D000544:Alzheimer Disease / Q000235:genetics; D053829:Amyloid Precursor Protein Secretases; D016229:Amyloid beta-Peptides / Q000096:biosynthesis / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000235:genetics / Q000378:metabolism*; D017209:Apoptosis; D016282:Aspartic Acid Endopeptidases; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000528:radiation effects; D010450:Endopeptidases / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D045604:Extracellular Fluid / Q000378:metabolism; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D009154:Mutation; D009447:Neuroblastoma / Q000473:pathology / Q000503:physiopathology*; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D016159:Tumor Suppressor Protein p53; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human