| Title: |
N -Glycan on the Non-Consensus N-X-C Glycosylation Site Impacts Activity, Stability, and Localization of the Sd a Synthase B4GALNT2 |
| Authors: |
Virginie Cogez; Dorothée Vicogne; Céline Schulz; Lucie Portier; Giulia Venturi; Jérôme de Ruyck; Mathieu Decloquement; Marc F. Lensink; Guillaume Brysbaert; Fabio Dall’Olio; Sophie Groux-Degroote; Anne Harduin-Lepers |
| Source: |
International Journal of Molecular Sciences, Vol 24, Iss 4, p 4139 (2023) |
| Publisher Information: |
MDPI AG |
| Publication Year: |
2023 |
| Collection: |
Directory of Open Access Journals: DOAJ Articles |
| Subject Terms: |
B4GALNT2; dimer; glycosyltransferase; N -glycan; unusual N-X-C glycosylation site; Biology (General); QH301-705.5; Chemistry; QD1-999 |
| Description: |
The Sd a carbohydrate epitope and its biosynthetic B4GALNT2 enzyme are expressed in the healthy colon and down-regulated to variable extents in colon cancer. The human B4GALNT2 gene drives the expression of a long and a short protein isoform (LF-B4GALNT2 and SF-B4GALNT2) sharing identical transmembrane and luminal domains. Both isoforms are trans-Golgi proteins and the LF-B4GALNT2 also localizes to post-Golgi vesicles thanks to its extended cytoplasmic tail. Control mechanisms underpinning Sd a and B4GALNT2 expression in the gastrointestinal tract are complex and not fully understood. This study reveals the existence of two unusual N -glycosylation sites in B4GALNT2 luminal domain. The first atypical N-X-C site is evolutionarily conserved and occupied by a complex-type N -glycan. We explored the influence of this N -glycan using site-directed mutagenesis and showed that each mutant had a slightly decreased expression level, impaired stability, and reduced enzyme activity. Furthermore, we observed that the mutant SF-B4GALNT2 was partially mislocalized in the endoplasmic reticulum, whereas the mutant LF-B4GALNT2 was still localized in the Golgi and post-Golgi vesicles. Lastly, we showed that the formation of homodimers was drastically impaired in the two mutated isoforms. An AlphaFold2 model of the LF-B4GALNT2 dimer with an N -glycan on each monomer corroborated these findings and suggested that N -glycosylation of each B4GALNT2 isoform controlled their biological activity. |
| Document Type: |
article in journal/newspaper |
| Language: |
English |
| Relation: |
https://www.mdpi.com/1422-0067/24/4/4139; https://doaj.org/toc/1661-6596; https://doaj.org/toc/1422-0067; https://doaj.org/article/718199075d484811b20971a1a49b3239 |
| DOI: |
10.3390/ijms24044139 |
| Availability: |
https://doi.org/10.3390/ijms24044139; https://doaj.org/article/718199075d484811b20971a1a49b3239 |
| Accession Number: |
edsbas.C0D46CDD |
| Database: |
BASE |