Peptide Sequence Mapping around Bisecting GlcNAc-Bearing <em>N</em>-Glycans in Mouse Brain
<i>N</i>-glycosylation is essential for many biological processes in mammals. A variety of <i>N</i>-glycan structures exist, of which, the formation of bisecting <i>N</i>-acetylglucosamine (GlcNAc) is catalyzed by <i>N</i>-acetylglucosaminyltransferase...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2021-08-01
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| Series: | International Journal of Molecular Sciences |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1422-0067/22/16/8579 |
| Summary: | <i>N</i>-glycosylation is essential for many biological processes in mammals. A variety of <i>N</i>-glycan structures exist, of which, the formation of bisecting <i>N</i>-acetylglucosamine (GlcNAc) is catalyzed by <i>N</i>-acetylglucosaminyltransferase-III (GnT-III, encoded by the <i>Mgat3</i> gene). We previously identified various bisecting GlcNAc-modified proteins involved in Alzheimer’s disease and cancer. However, the mechanisms by which GnT-III acts on the target proteins are unknown. Here, we performed comparative glycoproteomic analyses using brain membranes of wild type (WT) and <i>Mgat3</i>-deficient mice. Target glycoproteins of GnT-III were enriched with E4-phytohemagglutinin (PHA) lectin, which recognizes bisecting GlcNAc, and analyzed by liquid chromatograph-mass spectrometry. We identified 32 <i>N</i>-glycosylation sites (Asn-Xaa-Ser/Thr, Xaa ≠ Pro) that were modified with bisecting GlcNAc. Sequence alignment of identified <i>N</i>-glycosylation sites that displayed bisecting GlcNAc suggested that GnT-III does not recognize a specific primary amino acid sequence. The molecular modeling of GluA1 as one of the good cell surface substrates for GnT-III in the brain, indicated that GnT-III acts on <i>N</i>-glycosylation sites located in a highly flexible and mobile loop of GluA1. These results suggest that the action of GnT-III is partially affected by the tertiary structure of target proteins, which can accommodate bisecting GlcNAc that generates a bulky flipped-back conformation of the modified glycans. |
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| ISSN: | 1661-6596 1422-0067 |