Bacterial O-GlcNAcase genes abundance decreases in ulcerative colitis patients and its administration ameliorates colitis in mice

Objective O-linked N-acetylglucosaminylation (O-GlcNAcylation), controlled by O-GlcNAcase (OGA) and O-GlcNAc transferase (OGT), is an important post-translational modification of eukaryotic proteins and plays an essential role in regulating gut inflammation. Gut microbiota encode various enzymes involved in O-GlcNAcylation. However, the characteristics, abundance and function of these enzymes are unknown. Design We first investigated the structure and taxonomic distribution of bacterial OGAs and OGTs. Then, we performed metagenomic analysis to explore the OGA genes abundance in health samples and different diseases. Finally, we employed in vitro and in vivo experiments to determine the effects and mechanisms of bacterial OGAs to hydrolyse O-GlcNAcylated proteins in host cells and suppress inflammatory response in the gut. Results We found OGAs, instead of OGTs, are enriched in Bacteroidetes and Firmicutes, the major bacterial divisions in the human gut. Most bacterial OGAs are secreted enzymes with the same conserved catalytic domain as human OGAs. A pooled analysis on 1999 metagenomic samples encompassed six diseases revealed that bacterial OGA genes were conserved in healthy human gut with high abundance, and reduced exclusively in ulcerative colitis. In vitro studies showed that bacterial OGAs could hydrolyse O-GlcNAcylated proteins in host cells, including O-GlcNAcylated NF kappa B-p65 subunit, which is important for activating NF-kappa B signalling. In vivo studies demonstrated that gut bacteria-derived OGAs could protect mice from chemically induced colonic inflammation through hydrolysing O-GlcNAcylated proteins. Conclusion Our results reveal a previously unrecognised enzymatic activity by which gut microbiota influence intestinal physiology and highlight bacterial OGAs as a promising therapeutic strategy in colonic inflammation.

Automated summary

O-GlcNAcylation, controlled by O-GlcNAcase and O-GlcNAc transferase, is an important post-translational modification of eukaryotic proteins involved in regulating gut inflammation. Gut microbiota encode enzymes involved in O-GlcNAcylation, with bacterial OGAs enriched in Bacteroidetes and Firmicutes. A metagenomic analysis across different diseases showed that bacterial OGA genes were conserved in healthy gut but reduced in ulcerative colitis. Studies demonstrated that bacterial OGAs can hydrolyse O-GlcNAcylated proteins in host cells, including NF kappa B-p65 subunit, and protect mice from colonic inflammation.