title: Bisecting GlcNAc modification stabilizes BACE1 protein under oxidative stress conditions.
abstract: β-Site amyloid precursor protein-cleaving enzyme-1 (BACE1) is a protease essential for amyloid-β (Aβ) production in Alzheimer's disease (AD). BACE1 protein is known to be up-regulated by oxidative stress-inducing stimuli but the mechanism for this up-regulation still needs to be clarified. We have recently found that BACE1 is modified with bisecting N-acetylglucosamine (GlcNAc) by N-acetylglucosaminyltransferase-III (GnT-III, encoded by the Mgat3 gene) and that GnT-III deficiency reduces Aβ-plaque formation in the brain by accelerating lysosomal degradation of BACE1. Therefore, we hypothesized that bisecting GlcNAc would stabilize BACE1 protein on oxidative stress. In the present study, we first show that Aβ deposition in the mouse brain induces oxidative stress, together with an increase in levels of BACE1 and bisecting GlcNAc. Furthermore, prooxidant treatment induces expression of BACE1 protein in wild-type mouse embryonic fibroblasts (MEFs), whereas it reduces BACE1 protein in GnT-III (Mgat3) knock-out MEFs by accelerating lysosomal degradation of BACE1. We purified BACE1 from Neuro2A cells and performed LC/ESI/MS analysis for BACE1-derived glycopeptides and mapped bisecting GlcNAc-modified sites on BACE1. Point mutations at two N-glycosylation sites (Asn(153) and Asn(223)) abolish the bisecting GlcNAc modification on BACE1. These mutations almost cancelled the enhanced BACE1 degradation seen in Mgat3(-/-) MEFs, indicating that bisecting GlcNAc on BACE1 indeed regulates its degradation. Finally, we show that traumatic brain injury-induced BACE1 up-regulation is significantly suppressed in the Mgat3(-/-) brain. These results highlight the role of bisecting GlcNAc in oxidative stress-induced BACE1 expression and offer a novel glycan-targeted strategy for suppressing Aβ generation.
authors.affiliation: Disease Glycomics Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Centre for Systems Chemical Biology, Global Research Cluster, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Kizuka
authors.affiliation: Graduate School of Advanced Sciences of Matter, Hiroshima University, 1-3-1 Kagamiyama, Higashihiroshima, Hiroshima 739-8530, Japan.
authors.forename: Miyako
authors.initials: M
authors.lastname: Nakano
authors.affiliation: Disease Glycomics Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Centre for Systems Chemical Biology, Global Research Cluster, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan shinobuk@riken.jp dglycotani@riken.jp rvw.tani@sanken.osaka-u.ac.jp.
authors.forename: Shinobu
authors.initials: S
authors.lastname: Kitazume
authors.affiliation: Laboratory for Proteolytic Neuroscience, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Saito
authors.affiliation: Laboratory for Proteolytic Neuroscience, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Takaomi C
authors.initials: TC
authors.lastname: Saido
authors.affiliation: Disease Glycomics Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Centre for Systems Chemical Biology, Global Research Cluster, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan shinobuk@riken.jp dglycotani@riken.jp rvw.tani@sanken.osaka-u.ac.jp.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Taniguchi
mesh_terms: D000117:Acetylglucosamine / Q000096:biosynthesis* / Q000235:genetics; D053829:Amyloid Precursor Protein Secretases / Q000096:biosynthesis*; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000096:biosynthesis*; D001921:Brain / Q000378:metabolism / Q000473:pathology; D001930:Brain Injuries / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018384:Oxidative Stress / Q000502:physiology*
chemical_list: D053829:Amyloid Precursor Protein Secretases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human; D000117:Acetylglucosamine
keywords: Alzheimer’s disease; BACE1; GnT-III; bisecting GlcNAc; glycobiology; oxidative stress