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 de position 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