Bisecting GlcNAc modification stabilizes BACE1 protein under oxidative stress conditions

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 (Asn153 and Asn223) abolish the bisecting GlcNAc modification on BACE1. These mutations almost cancelled the enhanced BACE1 degradation seen in Mgat3–/– MEFs, indicating that bisecting Glc...
Source: Biochemical Journal - Category: Biochemistry Authors: Tags: Disease, Biomolecules Research articles Source Type: research