Department of Infectious Disease, Jiangmen Central Hospital, Affiliated Jiangmen Hospital of Sun Yat-sen University, Jiangmen, Guangdong, China.
Department of Microbiology, Guangdong Provincial Key Laboratory of Tropical Disease Research, School of Public Health, Southern Medical University, Guangzhou, Guangdong, China.
Gut. 2021 Oct;70(10):1872-1883. doi: 10.1136/gutjnl-2020-322468. Epub 2020 Dec 12.
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.
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.
We found OGAs, instead of OGTs, are enriched in and , 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-κB-p65 subunit, which is important for activating NF-κB signalling. In vivo studies demonstrated that gut bacteria-derived OGAs could protect mice from chemically induced colonic inflammation through hydrolysing O-GlcNAcylated proteins.
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.
O-连接 N-乙酰氨基葡萄糖基化（O-GlcNAcylation）受 O-GlcNAcase（OGA）和 O-GlcNAc 转移酶（OGT）的调控，是真核蛋白的一种重要翻译后修饰，在调节肠道炎症中起着至关重要的作用。肠道微生物群编码多种参与 O-GlcNAcylation 的酶。然而，这些酶的特征、丰度和功能尚不清楚。
我们首先研究了细菌 OGA 和 OGT 的结构和分类分布。然后，我们进行了宏基因组分析，以探索健康样本和不同疾病中 OGA 基因的丰度。最后，我们采用体外和体内实验来确定细菌 OGA 水解宿主细胞中 O-GlcNAc 化蛋白和抑制肠道炎症反应的作用和机制。
我们发现 OGA，而不是 OGT，在人类肠道中的主要细菌分类群 和 中丰富。大多数细菌 OGA 是分泌酶，具有与人类 OGA 相同的保守催化结构域。对涵盖 6 种疾病的 1999 个宏基因组样本的汇总分析表明，细菌 OGA 基因在健康人体肠道中高度保守且丰度高，而在溃疡性结肠炎中则特异性减少。体外研究表明，细菌 OGA 可以水解宿主细胞中的 O-GlcNAc 化蛋白，包括对激活 NF-κB 信号通路很重要的 O-GlcNAc 化 NF-κB-p65 亚基。体内研究表明，肠道细菌来源的 OGA 可以通过水解 O-GlcNAc 化蛋白来保护小鼠免受化学诱导的结肠炎症。
我们的研究结果揭示了肠道微生物群影响肠道生理学的一种先前未被识别的酶促活性，并强调了细菌 OGA 作为治疗结肠炎症的一种有前途的治疗策略。
