title: Mild oxidative stress induces redistribution of BACE1 in non-apoptotic conditions and promotes the amyloidogenic processing of Alzheimer's disease amyloid precursor protein.
abstract: BACE1 is responsible for β-secretase cleavage of the amyloid precursor protein (APP), which represents the first step in the production of amyloid β (Aβ) peptides. Previous reports, by us and others, have indicated that the levels of BACE1 protein and activity are increased in the brain cortex of patients with Alzheimer's disease (AD). The association between oxidative stress (OS) and AD has prompted investigations that support the potentiation of BACE1 expression and enzymatic activity by OS. Here, we have established conditions to analyse the effects of mild, non-lethal OS on BACE1 in primary neuronal cultures, independently from apoptotic mechanisms that were shown to impair BACE1 turnover. Six-hour treatment of mouse primary cortical cells with 10-40 µM hydrogen peroxide did not significantly compromise cell viability but it did produce mild oxidative stress (mOS), as shown by the increased levels of reactive radical species and activation of p38 stress kinase. The endogenous levels of BACE1 mRNA and protein were not significantly altered in these conditions, whereas a toxic H2O2 concentration (100 µM) caused an increase in BACE1 protein levels. Notably, mOS conditions resulted in increased levels of the BACE1 C-terminal cleavage product of APP, β-CTF. Subcellular fractionation techniques showed that mOS caused a major rearrangement of BACE1 localization from light to denser fractions, resulting in an increased distribution of BACE1 in fractions containing APP and markers for trans-Golgi network and early endosomes. Collectively, these data demonstrate that mOS does not modify BACE1 expression but alters BACE1 subcellular compartmentalization to favour the amyloidogenic processing of APP, and thus offer new insight in the early molecular events of AD pathogenesis.
authors.affiliation: Department of Pathology, The University of Melbourne, Parkville, Australia.
authors.forename: Jiang-Li
authors.initials: JL
authors.lastname: Tan
authors.forename: Qiao-Xin
authors.initials: QX
authors.lastname: Li
authors.forename: Giuseppe D
authors.initials: GD
authors.lastname: Ciccotosto
authors.forename: Peter John
authors.initials: PJ
authors.lastname: Crouch
authors.forename: Janetta Gladys
authors.initials: JG
authors.lastname: Culvenor
authors.forename: Anthony Robert
authors.initials: AR
authors.lastname: White
authors.forename: Genevieve
authors.initials: G
authors.lastname: Evin
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D000544:Alzheimer Disease / Q000378:metabolism* / Q000473:pathology*; D000682:Amyloid / Q000378:metabolism*; D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism; D002478:Cells, Cultured; D002499:Centrifugation, Density Gradient; D002540:Cerebral Cortex / Q000378:metabolism / Q000473:pathology; D004789:Enzyme Activation / Q000187:drug effects; D005455:Fluorescent Antibody Technique; D006861:Hydrogen Peroxide / Q000494:pharmacology; D015151:Immunoblotting; D051379:Mice; D008810:Mice, Inbred C57BL; D018384:Oxidative Stress / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D000682:Amyloid; D016564:Amyloid beta-Protein Precursor; C407306:GGA adaptor proteins; D006861:Hydrogen Peroxide; D053829:Amyloid Precursor Protein Secretases; D053148:Caspase 3; D016282:Aspartic Acid Endopeptidases; C509282:Bace1 protein, mouse