FIGURE 3.

BACE1 is modified with bisecting GlcNAc in vivo. (A) Bisecting GlcNAc modification by GnT-III. (B) BACE1 or APP was immunoprecipitated from mouse brains and blotted with E4-PHA lectin (Lower) or anti-BACE1 or APP antibodies (Upper). hAPP indicates the APP23 transgenic mouse model for AD. (C) Proteins from mouse brain membrane fractions were treated with or without PNGase F and then immunoblotted for BACE1 or for syntaxin 6 (loading control). (D) LC–MS base peak chromatogram of desialo-alditol N-glycans derived from mouse brain BACE1. To simplify the results, N-glycans were chemically desialylated before LC–MS analysis. BACE1-specific glycans, judged by comparison with N-glycan structures from anti-BACE1 IgG, are highlighted by red squares. Asterisks indicate glycans demonstrated by MS/MS analysis to contain a bisecting GlcNAc structure. Numbers in parentheses indicate the charge state. Reprinted with the permissions from Kizuka et al. (2015).