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Biochem Biophys Res Commun. 2018 May 5;499(2):354-360. doi: 10.1016/j.bbrc.2018.03.164. Epub 2018 Mar 26.

O-GlcNAc site-mapping of liver X receptor-α and O-GlcNAc transferase.

Author information

1
Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, 1046 Blindern, 0317 Oslo, Norway.
2
Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 1041 Blindern, 0317 Oslo, Norway.
3
Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 1041 Blindern, 0317 Oslo, Norway; CIME, Center for Integrative Microbial Evolution, University of Oslo, 1041 Blindern, 0317 Oslo, Norway.
4
Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, 1046 Blindern, 0317 Oslo, Norway.
5
Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, 0450 Oslo, Norway.
6
Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, 1046 Blindern, 0317 Oslo, Norway. Electronic address: lmgronningwang@gmail.com.

Abstract

The Liver X Receptor α (LXRα) belongs to the nuclear receptor superfamily and plays an essential role in regulating cholesterol, lipid and glucose metabolism and inflammatory responses. We have previously shown that LXRα is post-translationally modified by O-linked β-N-acetyl-glucosamine (O-GlcNAc) with increased transcriptional activity. Moreover, we showed that LXRα associates with O-GlcNAc transferase (OGT) in vitro and in vivo in mouse liver. In this study, we report that human LXRα is O-GlcNAc modified in its N-terminal domain (NTD) by identifying a specific O-GlcNAc site S49 and a novel O-GlcNAc modified peptide 20LWKPGAQDASSQAQGGSSCILRE42. However, O-GlcNAc site-mutations did not modulate LXRα transactivation of selected target gene promoters in vitro. Peptide array and co-immunoprecipitation assays demonstrate that LXRα interacts with OGT in its NTD and ligand-binding domain (LBD) in a ligand-independent fashion. Moreover, we map two new O-GlcNAc sites in the longest OGT isoform (ncOGT): S437 in the tetratricopeptide repeat (TPR) 13 domain and T1043 in the far C-terminus, and a new O-GlcNAc modified peptide (amino acids 826-832) in the intervening region (Int-D) within the catalytic domain. We also map four new O-GlcNAc sites in the short isoform sOGT: S391, T393, S399 and S437 in the TPRs 11-13 domain. Future studies will reveal the biological role of identified O-GlcNAc sites in LXRα and OGT.

KEYWORDS:

ETD MS; HCD MS; LXRα; O-GlcNAc; OGT

PMID:
29577901
DOI:
10.1016/j.bbrc.2018.03.164
[Indexed for MEDLINE]

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