Mechanism Of Glycosylation Research Articles

Altered expression of glycan patterns and glycan-related genes in the medial prefrontal cortex of the valproic acid rat model of autism.

Autism spectrum disorders (ASD) represent a group of neurodevelopmental defects characterized by social deficits and repetitive behaviors. Alteration in Glycosylation patterns could influence the nervous system development and contribute to the molecular mechanism of ASD. Interaction of environmental factors with susceptible genes may affect expressions of glycosylation-related genes and thus result in abnormal glycosylation patterns. Here, we used an environmental factor-induced model of autism by a single intraperitoneal injection of 400 mg/kg valproic acid (VPA) to female rats at day 12.5 post-conception. Following confirmation of reduced sociability and increased self-grooming behaviors in VPA-treated offspring, we analyzed the alterations in the expression profile of glycan patterns and glycan-related genes by lectin microarrays and RNA-seq, respectively. Lectin microarrays detected 14 significantly regulated lectins in VPA rats, with an up-regulation of high-mannose with antennary and down-regulation of Siaα2-3 Gal/GalNAc. Based on the KEGG and CAZy resources, we assembled a comprehensive list of 961 glycan-related genes to focus our analysis on specific genes. Of those, transcription results revealed that there were 107 differentially expressed glycan-related genes (DEGGs) after VPA treatment. Functional analysis of DEGGs encoding anabolic enzymes revealed that the process trimming to form core structure and glycan extension from core structure primarily changed, which is consistent with the changes in glycan patterns. In addition, the DEGGs encoding glycoconjugates were mainly related to extracellular matrix and axon guidance. This study provides insights into the underlying molecular mechanism of aberrant glycosylation after prenatal VPA exposure, which may serve as potential biomarkers for the autism diagnosis.

Characterization of glycosylation regulator-mediated glycosylation modification patterns and tumor microenvironment infiltration in hepatocellular carcinoma.

Background: Previous studies have shown that glycosylation of proteins ofen plays an important role in HCC. However, the potential mechanism of glycosylation in HCC has not been described systematically. Methods: We comprehensively evaluated the glycosylation patterns in HCC samples based on 43 glycosylation regulators, and annotated the modification patterns with the enrichment of immune cells and stromal cells. Considering the heterogeneity of HCC patients, the glycosylation score was constructed using single-sample gene set enrichment analysis (ssGSEA). We also explored the drugs that different HCC patients were sensitive to based on glycosylation mode and score. Results: We identified three glycosylation-regulated gene subtypes. By annotating the subtypes, it was found that the glycosylation regulated gene subtypes was highly matched with three immunophenotypes of HCC (immune-inflamed, immune-excluded, and immune-desert), regardless of the characteristics of immune cell infiltration or prognosis. Based on the characteristic genes of glycosylation-regulated gene subtypes, we constructed a glycosylation-related model, and found that glycosylation-related model was highly consistent with the glycosylation regulated gene subtypes. The glycosylation score that evaluates the glycosylation characteristics of a single HCC sample has high prognostic value, and the prognosis of patients with high glycosylation score is significantly worse. Interestingly, we found that the glycosylation score was closely related to tumor node metastasis (TNM) staging. By applying glycosylation-regulated gene subtypes and glycosylation score to explore the sensitivity of different patients to anticancer drugs, it was found that the sensitivity of Thapsigargin, Shikonin, Embelin and Epothilone. B was closely related to the glycosylation mode. Conclusion: This study reveals that the diversity of glycosylation patterns plays an important role in HCC. Therefore, evaluating the glycosylation patterns of patients with HCC will be helpful in identifying the characteristics of immune cell infiltration and selecting accurate treatment methods.

Abstract 12874: A Novel Mechanism in the Pathogenesis of Heart Failure With Preserved Ejection Fraction Through Hexokinase Mitochondrial Dislocation and Substrate Shuttling Into the O-Glcnacylation Machinery

Introduction: Endothelial cell (EC) dysfunction underlies the pathogenesis of heart failure with preserved ejection fraction (HFpEF), however, the mechanism is unclear. ECs are highly dependent on glycolysis; however, it is not known how their metabolic profile is altered in the setting of HFpEF. Hexokinase 1 (HK1) carries the first step in glycolysis and is mostly bound to the mitochondria in ECs. Objective: We sought to elucidate the role of EC glucose metabolism, and specifically HK1, in the development of HFpEF. Results: We first showed that among glycolytic enzymes, HK1 is highly specific to ECs, suggesting the significance of HK1 in EC physiology. Although HK1 mRNA and protein levels are not changed, we noted increased dislocation of HK1 from the mitochondria in ECs from HFpEF mice. To study the role of HK1 dislocation in the development of HFpEF, we generated mice with mitochondrial-binding domain of the endogenous HK1 replaced with Flag tag (ΔE1HK1). ΔE1HK1mice develop impaired cardiac relaxation at 20 weeks of age and HFpEF by 40 weeks, and ECs from these mice displayed impaired angiogenic potential. Since HK1 is involved in glucose metabolism, we then performed metabolomic studies and demonstrated that intermediates in hexosamine biosynthetic pathway (HBP) are significantly decreased in ECs from ΔE1HK1 mice. To assess the mechanism for the decrease in HBP, we assessed protein modification, and noted reduced protein N-glycosylation and increased O-GlcNAcylation in ECs from ΔE1HK1. We also demonstrated that inhibition of the key enzyme in O-GlcNAcylation (OGT) reverses the EC dysfunction noted in ΔE1HK1 mice, indicating that O-GlcNAcylation is responsible for the angiogenic defect in ECs from ΔE1HK1. Finally, to provide a mechanism for altered protein glycosylation with HK1 mitochondrial dislocation, we showed that HK1 associates with N-glycosylation machinery when it is attached to mitochondria, while it binds to OGT when it is dislocated from mitochondria. Conclusion: Our studies demonstrate a role for HK1 mitochondrial binding and protein O-GlcNAcylation in the pathogenesis of HFpEF, and that HK1 cellular localization plays a major role in the fate of HBP intermediates into either N-glycosylation or O-GlcNAcylation machinery in ECs.

Advances in IgA glycosylation and its correlation with diseases.

Immunoglobulin A (IgA) is the most abundant immunoglobulin synthesized in the human body. It has the highest concentration in the mucosa and is second only to IgG in serum. IgA plays an important role in mucosal immunity, and is the predominant antibody used to protect the mucosal surface from pathogens invasion and to maintain the homeostasis of intestinal flora. Moreover, The binding IgA to the FcαRI (Fc alpha Receptor I) in soluble or aggregated form can mediate anti- or pro- inflammatory responses, respectively. IgA is also known as one of the most heavily glycosylated antibodies among human immunoglobulins. The glycosylation of IgA has been shown to have a significant effect on its immune function. Variation in the glycoform of IgA is often the main characteration of autoimmune diseases such as IgA nephropathy (IgAN), IgA vasculitis (IgAV), systemic lupus erythematosus (SLE), and rheumatoid arthritis (RA). However, compared with the confirmed glycosylation function of IgG, the pathogenic mechanism of IgA glycosylation involved in related diseases is still unclear. This paper mainly summarizes the recent reports on IgA’s glycan structure, its function, its relationship with the occurrence and development of diseases, and the potential application of glycoengineered IgA in clinical antibody therapeutics, in order to provide a potential reference for future research in this field.

Glycosylation of egg white protein with maltodextrin in the dry state: Changes in structural and gel properties

The glycosylation of egg white proteins (EWP) with maltodextrin (MD) was investigated by monitoring their gel properties and protein structure. The improved gel properties of glycosylated EWP (GEWP) were confirmed by the increase in gel hardness, gel water holding capacity (WHC), rheological parameters, and finer gel microstructures. The protein structures were characterized by monitoring changes in the content of sulfhydryl (SH) group, circular dichroism (CD) and X-ray diffraction (XRD) spectra, and differential scanning calorimetry (DSC). The GEWP structures were unfolded due to extended glycosylation, as observed by increased content of exposed SH group and β-sheet and decreased crystallinity, thermal denaturation temperature (Td), and enthalpy (ΔH). A correlation was also found between the gel properties and the protein structural changes. Overall, this study is beneficial for determining the mechanism of glycosylation and provides a convenient approach to improving the gel properties of EWP, which can further broaden the application of EWP in the food industry.

Glycopattern Alteration of Glycoproteins in Gastrointestinal Cancer Cell Lines and Their Cell-Derived Exosomes.

Gastrointestinal (GI) cancers constitute the largest portion of all human cancers, and the most prevalent GI cancers in China are colorectal cancer (CRC), gastric cancer (GC), and hepatocellular carcinoma (HCC). Exosomes are nanosized vesicles containing proteins, lipids, glycans, and nucleic acid, which play important roles in the tumor microenvironment and progression. Aberrant glycosylation is closely associated with GI cancers; however, little is known about the glycopattern of the exosomes from GI cancer cells. In this study, glycopatterns of HCC, CRC, and GC cell lines and their exosomes were detected using lectin microarrays. For all exosomes, (GlcNAcβ1-4)n and Galβ1-4GlcNAc (DSA) were the most abundant glycans, but αGalNAc and αGal (GSL-II and SBA) were the least. Different cancers had various characteristic glycans in either cells or exosomes. Glycans altered in cell-derived exosomes were not always consistent with the host cells in the same cancer. However, Fucα1-6GlcNAc (core fucose) and Fucα1-3(Galβ1-4)GlcNAc (AAL) were altered consistently in cells and exosomes although they were decreased in HCC and CRC but increased in GC. The study drew the full-scale glycan fingerprint of cells and exosomes related to GI cancer, which may provide useful information for finding specific biomarkers and exploring the underlying mechanism of glycosylation in exosomes.

Towards the Accurate Thermodynamic Characterization of Enzyme Reaction Mechanisms.

We employed QM/MM molecular dynamics (MD) simulations to characterize the rate-limiting step of the glycosylation reaction of pancreatic α-amylase with combined DFT/molecular dynamics methods (PBE/def2-SVP : AMBER). Upon careful choice of four starting active site conformations based on thorough reactivity criteria, Gibbs energy profiles were calculated with umbrella sampling simulations within a statistical convergence of 1-2 kcal ⋅ mol-1 . Nevertheless, Gibbs activation barriers and reaction energies still varied from 11.0 to 16.8 kcal ⋅ mol-1 and -6.3 to +3.8 kcal ⋅ mol-1 depending on the starting conformations, showing that despite significant state-of-the-art QM/MM MD sampling (0.5 ns/profile) the result still depends on the starting structure. The results supported the one step dissociative mechanism of Asp197 glycosylation preceded by an acid-base reaction by the Glu233, which are qualitatively similar to those from multi-PES QM/MM studies, and thus support the use of the latter to determine enzyme reaction mechanisms.

Lamprey immunity protein enables detection for bladder cancer through recognizing N-hydroxyacetylneuraminic acid (Neu5Gc)-modified as a diagnostic marker and exploration of its production mechanism

Previous studies have demonstrated that Neu5Gc is highly expressed in breast, ovarian, prostate, colon and lung cancers, but not in normal human cells. The presence of Neu5Gc is important for prognosis and is associated with aggressiveness, metastasis, and tumor grade. However, increased Neu5Gc in bladder cancer remains unclear. LIP from lamprey binds the carbohydrate receptor of N-glycolylneuraminic acid (Neu5Gc). The combination of Neu5Gc and LIP suggested that it might be used as a diagnostic tool for the detection of Neu5Gc tumor antigen. Here, the classical animal model of bladder cancer was successfully induced by MNU bladder perfusion. The ELISA results showed that the expression level of Neu5Gc in the urine of normal rats was 94.96 ± 21.01ng/mg, and that of bladder cancer rats was 158.28 ± 34.86 ng/mg. In addition, the results of SNA and LIP immunohistochemistry demonstrated the high expression of Neu5Gc in bladder cancer. After the addition of Neu5Gc to BIU-87 and SV-HUC-1 cells, transcriptomic sequencing and real-time quantitative PCR analysis demonstrated that the gene expression of Neu5Gc synthesis pathway was significantly increased. These data suggest that LIP provides a new tool for the detection of biological samples, especially urine from patients with bladder cancer or suspected cancer, and that revealing the mechanism of abnormal glycosylation can provide theoretical basis for clinical studies.

Forming coumarin C-glycosides via biocatalysis: Characterization of a C-glycosyltransferase from Angelica decursiva

A glycosyl transferase, isolated from Angelica decursiva a medical herb rich in coumarin, shows C-glycosyl transferase activity by in vitro activity assay using 5,7-dihydroxycoumarin as substrate, producing a C-glycosylated product at position C′8 along with the main product at C′6 position. Catalytic promiscuity assay shows that AdCGT also displays O- or C-glycosylation activity to other coumarins and flavonoids. When phloretin and 2,4,6-trihydroxyacetophenone were fed as substrates, AdCGT catalyzed the formation of di-C-glycosides. Therefore, AdCGT is a multifunctional glycosyltransferase with a broad substrate acceptability. This work highlights the potential of AdCGT as a catalyst for glycosylation of coumarin and reveals a new regio-selective C-glycosyltransferase, providing a basis for exploring the mechanism of coumarin glycosylation.

The role of protein glycosylation in muscle diseases.

As a post-translational modification, glycosylation plays vital role in regulating the folding and function of proteins necessary for many biological processes. Unlike glycation, glycosylation is an enzymatic process; glycosyltransferases transfer sugars to proteins, forming glycosidic bonds with amino acid residues on proteins. Changes that interfere with the enzymatic reaction and result in abnormal glycosylation can spatio-temporally affect the balance of glycosylation, leading to disease states. Muscle diseases have been associated with dysfunctional protein glycosylation, and many studies have focused on the pathophysiology underlying this association. This review aims to summarize the research progress on protein glycosylation in the pathogenesis of muscle diseases and provides new insight into the muscle research field. Literatures were reviewed comparatively and data were organized to find information about protein glycosylation and its role in muscle disease. Protein glycosylation modification is closely related to the occurrence of muscle diseases. α-DG is a key protein in the study of inherited muscle diseases and has a wide range of glycosylation, including O-linked glycosylation and N-linked glycosylation. Besides, O-GlcNAc glycosylation is an important mechanism of protein glycosylation, helping maintaining the structure and function of skeletal muscle and participating in multiple biological processes. Protein glycosylation is also connected to muscle disease and neurodegenerative diseases, especially Alzheimer's disease. Taken together, better understanding of protein glycosylation and its implication in muscle disease would help provide new perspectives in the prevention and treatment measures for human muscle diseases.

Unravelling the consecutive glycosylation and methylation of flavonols in peach in response to UV‐B irradiation

Flavonol glycosides are bioactive compounds important for plant defence and human nutrition. Glycosylation and methylation play an important role in enriching the diversity of flavonols in response to the environment. Peach flowers and fruit are rich in flavonol diglycosides such as isorhamnetin 3-O-rutinoside (I3Rut), kaempferol 3-O-rutinoside and quercetin 3-O-rutinoside, and flavonol monoglycosides such as I 3-O-glucoside and Q 3-O-galactoside. UV-B irradiation of fruit significantly induced accumulation of all these flavonol glycosides. Candidate biosynthetic genes induced by UV-B were identified by genome homology searches and the in vitro catalytic activities of purified recombinant proteins determined. PpUGT78T3 and PpUGT78A2 were identified as flavonol 3-O-glucosyltransferase and 3-O-galactosyltransferase, respectively. PpUGT91AK6 was identified as flavonol 1,6-rhamnosyl trasferase catalysing the formation of flavonol rutinosides and PpFOMT1 was identified as a flavonol O-methyltransferase that methylated Q at the 3'-OH-OH to form isorhamnetin derivatives. Transient expression in Nicotiana benthamiana confirmed the specificity of PpUGT78T3 as a flavonol 3-O-glucosyltransferase, PpUGT78A2 as a 3-O-galactosyltransferase, PpUGT91AK6 as a 1,6-rhamnosyltrasferase and PpFOMT1 as an O-methyltransferase. This study provides new insights into the mechanisms of glycosylation and methylation of flavonols, especially the formation of flavonol diglycosides such as I3Rut, and will also be useful for future potential metabolic engineering of complex flavonols.

Targeting Tumor Glycans for Cancer Therapy: Successes, Limitations, and Perspectives.

Simple SummaryAberrant glycosylation is a common feature of many cancers, and it plays crucial roles in tumor development and biology. Cancer progression can be regulated by several physiopathological processes controlled by glycosylation, such as cell–cell adhesion, cell–matrix interaction, epithelial-to-mesenchymal transition, tumor proliferation, invasion, and metastasis. Different mechanisms of aberrant glycosylation lead to the formation of tumor-associated carbohydrate antigens (TACAs), which are suitable for selective cancer targeting, as well as novel antitumor immunotherapy approaches. This review summarizes the strategies developed in cancer immunotherapy targeting TACAs, analyzing molecular and cellular mechanisms and state-of-the-art methods in clinical oncology.Aberrant glycosylation is a hallmark of cancer and can lead to changes that influence tumor behavior. Glycans can serve as a source of novel clinical biomarker developments, providing a set of specific targets for therapeutic intervention. Different mechanisms of aberrant glycosylation lead to the formation of tumor-associated carbohydrate antigens (TACAs) suitable for selective cancer-targeting therapy. The best characterized TACAs are truncated O-glycans (Tn, TF, and sialyl-Tn antigens), gangliosides (GD2, GD3, GM2, GM3, fucosyl-GM1), globo-serie glycans (Globo-H, SSEA-3, SSEA-4), Lewis antigens, and polysialic acid. In this review, we analyze strategies for cancer immunotherapy targeting TACAs, including different antibody developments, the production of vaccines, and the generation of CAR-T cells. Some approaches have been approved for clinical use, such as anti-GD2 antibodies. Moreover, in terms of the antitumor mechanisms against different TACAs, we show results of selected clinical trials, considering the horizons that have opened up as a result of recent developments in technologies used for cancer control.

PUStackNGly: Positive-Unlabeled and Stacking Learning for N-Linked Glycosylation Site Prediction

N-linked glycosylation is one of the most common protein post-translation modifications (PTMs) in humans where the Asparagine (N) amino acid of the protein is attached to the glycan. It is involved in most biological processes and associated with various human diseases as diabetes, cancer, coronavirus, influenza, and Alzheimer’s. Accordingly, identifying N-linked glycosylation sites will be beneficial to understanding the system and mechanism of glycosylation. Due to the experimental challenges of glycosylation site identification, machine learning becomes very important to predict the glycosylation sites. This paper proposes a novel N-linked glycosylation predictor based on bagging positive-unlabeled (PU) learning and stacking ensemble machine learning (PUStackNGly). In the proposed PUStackNGly, comprehensive sequence and structural-based features are extracted using different feature extraction descriptors. Then, ensemble-based feature selection is employed to select the most significant and stable features. The ensemble bagging PU learning selects the reliable negative samples from the unlabeled samples using four supervised learning methods (support vector machines, random forest, logistic regression, and XGBoost). Then, stacking ensemble learning is applied using four base classifiers: logistic regression, artificial neural networks, random forest, and support vector machine. The experiments results show that PUStackNGly has a promising predicting performance compared to supervised learning methods. Furthermore, the proposed PUStackNgly outperforms the existing N-linked glycosylation prediction tools on an independent dataset with 95.11% accuracy, 100% recall 80.7% precision, 89.32% F1 score, 96.93% AUC, and 0.87 MCC.

Structure-function relationship of terpenoid glycosyltransferases from plants.

Covering: up to 2021Terpenoids are physiologically active substances that are of great importance to humans. Their physicochemical properties are modified by glycosylation, in terms of polarity, volatility, solubility and reactivity, and their bioactivities are altered accordingly. Significant scientific progress has been made in the functional study of glycosylated terpenes and numerous plant enzymes involved in regio- and enantioselective glycosylation have been characterized, a reaction that remains chemically challenging. Crucial clues to the mechanism of terpenoid glycosylation were recently provided by the first crystal structures of a diterpene glycosyltransferase UGT76G1. Here, we review biochemically characterized terpenoid glycosyltransferases, compare their functions and primary structures, discuss their acceptor and donor substrate tolerance and product specificity, and elaborate features of the 3D structures of the first terpenoid glycosyltransferases from plants.

PD-L2 glycosylation promotes immune evasion and predicts anti-EGFR efficacy

BackgroundCombination therapy has been explored for advanced head and neck squamous cell carcinoma (HNSCC) owing to the limited efficacy of anti-epidermal growth factor receptor (EGFR) therapy. Increased expression and glycosylation...

Recent advances in glycopeptide enrichment and mass spectrometry data interpretation approaches for glycoproteomics analyses

蛋白质糖基化是生物体内最重要的翻译后修饰之一,在蛋白质稳定性、细胞内和细胞间信号转导、激素活化或失活和免疫调节等生理过程和病理进程中发挥重要作用。而异常的蛋白质糖基化往往和多种疾病的发生发展密切相关,目前应用于临床检测的多种肿瘤生物标志物大多属于糖蛋白或者糖抗原。因此在组学层次系统分析蛋白质糖基化的变化对阐明生物体内糖基化修饰的调控机理和发现新型疾病标志物都非常重要。基于质谱的蛋白质组学技术为全面分析蛋白质及其修饰提供了有效的分析手段。在自下而上的蛋白质组学研究中,由于完整糖基化肽段同时存在性质各异的肽段骨架和糖链结构、糖肽的相对丰度和离子化效率较低以及糖基化修饰有高度异质性等特点,完整糖肽的分析比其他翻译后修饰更加困难。近年来,为了更全面、系统地分析蛋白质糖基化,研究人员发展了一些新技术,包括完整糖肽的富集技术、质谱的碎裂模式和数据采集模式、质谱数据的解析方法和定量策略等等,大力推进了该领域的研究水平,也为研究蛋白质糖基化相关的生物标志物提供了技术支持。该篇综述主要关注近年来基于质谱的糖蛋白质组学研究中的新进展,重点介绍针对完整N-和O-糖基化肽段的富集新技术和谱图解析新方法,并讨论其在肿瘤早期诊断方面的应用潜力。

Molecular cloning and functional characterization of UGTs from Glycyrrhiza uralensis flavonoid pathway

Glycyrrhiza uralensis Fisch., a well-known medicinal plant, contains flavonoids including liquiritigenin and isoliquiritigenin, and their corresponding glycoside liquiritin and isoliquiritin. Although some genes encoding UDP-glycosyltransferases (UGTs) have been functionally characterized in G. uralensis, other UGTs mechanisms of glycosylation remain to be elucidated. Against this background the aim of the present study included cloning and characterization of two full-length cDNA clones of GuUGT isoforms from the UGT multigene family. These included GuUGT2 (NCBI acc. MK341791) and GuUGT3 (NCBI acc. MK341793) with an ORF of 1473 and 1332 bp, respectively. Multiple alignments and phylogenetic analysis revealed GuUGTs protein of Glycine max had a high homology to that of other plants. Meanwhile, quantitative real-time PCR was performed to detect the transcript levels of GuUGTs in different tissues. The results indicated that GuUGTs was more expressed in roots as compared to the leaves, and significantly up-regulated upon NaCl stress. The recombinant protein was heterologous expressed in Escherichia coli and exhibited a high level of UGT activity, catalyzing formation of isoliquiritin and liquiritin from isoliquiritigenin and liquiritigenin. The key residues of GuUGT2 for liquiritigenin glycosylation (Asn223), isoliquiritigenin (Asp272) were predicted by molecular docking and residue scanning based on simulated mutations. These results could serve as an important reference to understand the function of the UGT family. In addition, the identification of GuUGT2 and GuUGT3 provides a foundation for future studies of flavonoid biosynthesis in G. uralensis.

Self‐Promoted Glycosylation for the Synthesis of β‐N‐Glycosyl Sulfonyl Amides

AbstractN‐Glycosyl N‐sulfonyl amides have been synthesized by a self‐promoted glycosylation, i. e. without any catalysts, promotors or additives. When the reactions were carried out at lower temperatures a mixture of N‐ and O‐glycosides were observed, where the latter rearranged to give the β‐N‐glycosides at elevated temperatures. By this method sulfonylated asparagine derivatives can be selectively β‐glycosylated in high yields by trichloroacetimidate glycosyl donors of different reactivity including protected glucosamine derivatives. The chemoselectivity in the glycosylations as well as the rearrangements from O‐glycosides to β‐N‐glycosides gives information of the glycosylation mechanism. This method gives access to glycosyl sulfonyl amides under mild conditions.

The glycosyltransferase ST3GAL2 is regulated by miR-615-3p in the intestinal tract of Campylobacter jejuni infected mice

BackgroundCampylobacter jejuni (C. jejuni) infections are of increasing importance worldwide. As a typical mucosal pathogen, the interaction of C. jejuni with mucins is a prominent step in the colonisation of mucosal surfaces. Despite recent advances in understanding the interaction between bacterial pathogens and host mucins, the mechanisms of mucin glycosylation during intestinal C. jejuni infection remain largely unclear. This prompted us to identify relevant regulatory networks that are concerted by miRNAs and could play a role in the mucin modification and interaction.ResultsWe firstly used a human intestinal in vitro model, in which we observed altered transcription of MUC2 and TFF3 upon C. jejuni NCTC 11168 infection. Using a combined approach consisting of in silico analysis together with in vitro expression analysis, we identified the conserved miRNAs miR-125a-5p and miR-615-3p associated with MUC2 and TFF3. Further pathway analyses showed that both miRNAs appear to regulate glycosyltransferases, which are related to the KEGG pathway ‘Mucin type O-glycan biosynthesis’. To validate the proposed interactions, we applied an in vivo approach utilising a well-established secondary abiotic IL-10−/− mouse model for infection with C. jejuni 81-176. In colonic tissue samples, we confirmed infection-dependent aberrant transcription of MUC2 and TFF3. Moreover, two predicted glycosyltransferases, the sialyltransferases ST3GAL1 and ST3GAL2, exhibited inversely correlated transcriptional levels compared to the expression of the identified miRNAs miR-125a-5p and miR-615-3p, respectively. In this study, we mainly focused on the interaction between miR-615-3p and ST3GAL2 and were able to demonstrate their molecular interaction using luciferase reporter assays and RNAi. Detection of ST3GAL2 in murine colonic tissue by immunofluorescence demonstrated reduced intensity after C. jejuni 81-176 infection and was thus consistent with the observations made above.ConclusionsWe report here for the first time the regulation of glycosyltransferases by miRNAs during murine infection with C. jejuni 81-176. Our data suggest that mucin type O-glycan biosynthesis is concerted by the interplay of miRNAs and glycosyltransferases, which could determine the shape of intestinal glycosylated proteins during infection.

Metal-free glycosylation with glycosyl fluorides in liquid SO2.

Liquid SO2 is a polar solvent that dissolves both covalent and ionic compounds. Sulfur dioxide possesses also Lewis acid properties, including the ability to covalently bind Lewis basic fluoride ions in a relatively stable fluorosulfite anion (FSO2−). Herein we report the application of liquid SO2 as a promoting solvent for glycosylation with glycosyl fluorides without any external additive. By using various temperature regimes, the method is applied for both armed and disarmed glucose and mannose-derived glycosyl fluorides in moderate to excellent yields. A series of pivaloyl-protected O- and S-mannosides, as well as one example of a C-mannoside, are synthesized to demonstrate the scope of the glycosyl acceptors. The formation of the fluorosulfite species during the glycosylation with glycosyl fluorides in liquid SO2 is proved by 19F NMR spectroscopy. A sulfur dioxide-assisted glycosylation mechanism that proceeds via solvent separated ion pairs is proposed, whereas the observed α,β-selectivity is substrate-controlled and depends on the thermodynamic equilibrium.