Identification and characterization of three novel beta 1,3-N-acetylglucosaminyltransferases structurally related to the beta 1,3-galactosyltransferase family

Impacts of β-1, 3-N-acetylglucosaminyltransferases (B3GNTs) in human diseases

Glycosylation modification of proteins is a common post-translational modification that exists in various organisms and has rich biological functions. It is usually catalyzed by multiple glycosyltransferases located in the Golgi apparatus. β-1,3-N-acetylglucosaminyltransferases (B3GNTs) are members of the glycosyltransferases and have been found to be involved in the occurrence and development of a variety of diseases including autoimmunity diseases, cancers, neurodevelopment, musculoskeletal system, and metabolic diseases. The functions of B3GNTs represent the glycosylation of proteins is a crucial and frequently life-threatening step in progression of most diseases. In this review, we give an overview about the roles of B3GNTs in tumor, nervous system, musculoskeletal and metabolic diseases, describing the recent results about B3GNTs, in order to provide a research direction and exploration value for the prevention, diagnosis and treatment of these diseases.

Glyco-Engineering Cell Surfaces by Exo-Enzymatic Installation of GlcNAz and LacNAz Motifs

Exo-enzymatic glyco-engineering of cell-surface glycoconjugates enables the selective display of well-defined glyco-motifs bearing bioorthogonal functional groups, which can be used to study glycans and their interactions with glycan-binding proteins. In recent years, strategies to edit cellular glycans by installing monosaccharides and their derivatives using glycosyltransferase enzymes have rapidly expanded. However, analogous methods to introduce chemical reporter-functionalized type 2 LacNAc motifs have not been reported. Herein, we report the chemo-enzymatic synthesis of unnatural UDP-GlcNAc and UDP-GalNAc nucleotide-sugars bearing azide, alkyne, and diazirine functionalities on the C2-acetamido group using the mutant uridylyltransferase AGX1F383A. The unnatural UDP-GlcNAc derivatives were examined as substrates for the human GlcNAc-transferase B3GNT2, where it was found that modified donors were tolerated for transfer, albeit to a lesser extent than the natural UDP-GlcNAc substrate. When the GlcNAc derivatives were examined as acceptor substrates for the human Gal-transferase B4GalT1, all derivatives were well tolerated and the enzyme could successfully form derivatized LacNAcs. B3GNT2 was also used to exo-enzymatically install GlcNAc and unnatural GlcNAc derivatives on cell-surface glycans. GlcNAc- or GlcNAz-engineered cells were further extended by B4GalT1 and UDP-Gal, producing LacNAc- or LacNAz-engineered cells. Our proof-of-concept glyco-engineering labeling strategy is amenable to different cell types and our work expands the exo-enzymatic glycan editing toolbox to selectively introduce unnatural type 2 LacNAc motifs.

Elevated serum CA199 levels in patients suffering type 2 diabetes vs. various types of cancer

AIMS

Carbohydrate antigen 199 (CA199) is a standard tumor marker, and recent studies have found elevated in CA199 levels in patients with diabetes. However, there is no systematic measurement and comparison of serum CA199 levels in patients with diabetes and cancer. Here, a detailed description of the changes in serum CA199 levels in patients with type 2 diabetes and various cancers was explored.

METHODS

A total of 5,641 participants were screened for clinical laboratory test results of serum CA199 levels over the past three years (2020-2023). This study included 2,464 healthy controls, 688 patients with type 2 diabetes, and 2,489 patients with 16 different types of cancer. Each type of cancer had more than 30 independent serum CA199 level test results. The serum CA199 levels were compared between cancer groups, type 2 diabetes patients, and healthy controls. Additionally, the CA199 levels of cancer patients were compared with those of patients with type 2 diabetes.

RESULTS

The serum CA199 levels of esophagus cancer, lung cancer, pancreatic cancer, ovarian cancer, breast cancer, rectum cancer, prostate cancer, bladder cancer, liver cancer, gastric cancer, cervical cancer, colon cancer, lymphoma, thyroid cancer, intracranial tumors, and nasopharyngeal laryngeal cancer were found to be elevated compared to healthy controls (P < 0.01). In addition, the serum CA199 levels of patients with type 2 diabetes were also significantly elevated compared to healthy controls (P < 0.01). Moreover, the degree of elevation in serum CA199 levels in patients with type 2 diabetes was not significantly different from that observed in some types of cancer, such as esophagus cancer (P = 0.163), breast cancer (P = 0.927), prostate cancer (P = 1.000), bladder cancer (P = 0.406), Lymphoma (P = 0.975), thyroid cancer (P = 1.000), intracranial tumors (P = 0.161), nasopharyngeal and laryngeal cancer (P = 1.000).

CONCLUSIONS

Serum CA199 levels also increase in type 2 diabetes, and the magnitude of the increase is similar to that seen in some cancers.

Imidazolone as an Amide Bioisostere in the Development of β-1,3-N-Acetylglucosaminyltransferase 2 (B3GNT2) Inhibitors

B3GNT2 is responsible for elongation of cell surface long-chain polylactosamine, which influences the regulation of the immune response, making it an attractive target for immunomodulation. In the development of amide containing B3GNT2 inhibitors guided by structure-based drug design, imidazolones were found to successfully serve as amide bioisosteres. This novel imidazolone isosteric strategy alleviated torsional strain of the amide bond on binding to B3GNT2 and improved potency, isoform selectivity, as well as certain physicochemical and pharmacokinetic properties. Herein, we present the synthesis, SAR, X-ray cocrystal structures, and in vivo PK properties of imidazol-4-ones in the context of B3GNT2 inhibition.

Glyco-engineered MDCK cells display preferred receptors of H3N2 influenza absent in eggs used for vaccines

Evolution of human H3N2 influenza viruses driven by immune selection has narrowed the receptor specificity of the hemagglutinin (HA) to a restricted subset of human-type (Neu5Acα2-6 Gal) glycan receptors that have extended poly-LacNAc (Galβ1-4GlcNAc) repeats. This altered specificity has presented challenges for hemagglutination assays, growth in laboratory hosts, and vaccine production in eggs. To assess the impact of extended glycan receptors on virus binding, infection, and growth, we have engineered N-glycan extended (NExt) cell lines by overexpressing β3-Ν-acetylglucosaminyltransferase 2 in MDCK, SIAT, and hCK cell lines. Of these, SIAT-NExt cells exhibit markedly increased binding of H3 HAs and susceptibility to infection by recent H3N2 virus strains, but without impacting final virus titers. Glycome analysis of these cell lines and allantoic and amniotic egg membranes provide insights into the importance of extended glycan receptors for growth of recent H3N2 viruses and relevance to their production for cell- and egg-based vaccines.

β3GNT9 as a prognostic biomarker in glioblastoma and its association with glioblastoma immune infiltration, migration and invasion

Background

Studies have shown that the immune infiltration of tumor microenvironment is related to the prognosis of glioblastoma, which is characterized by high heterogeneity, high recurrence rate and low survival rate. To unravel the role of β1,3-N-acetylglucosaminyltransferase-9 (β3GNT9) in the progression of glioblastoma, this study identifies the value of β3GNT9 as a prognostic biomarker in glioblastoma, and investigates the relationship between β3GNT9 expression and glioblastoma immune infiltration, migration and invasion.

Methods

β3GNT9 expression in glioblastoma was analyzed using the GEPIA database. The clinical features of glioblastoma were screened out from the TCGA database. The relationship between β3GNT9 expression and clinical features was analyzed. The relationship between β3GNT9 and the prognosis of glioblastoma was evaluated through univariate and multivariate COX regression analyses, and the survival analysis was conducted using the Kaplan-Meier method. GSEA was employed to predict the signaling pathway of β3GNT9 in glioblastoma. The correlation between β3GNT9 and tumor immune infiltration was analyzed using the related modules of CIBERSORT and TIMER. A172, U87MG and U251 cell lines were selected to verify β3GNT9 expression in vitro. The effects of β3GNT9 on the migration and invasion of glioblastoma were investigated through cell scratch and invasion assays.

Results

β3GNT9 expression in glioblastoma group was significantly higher than that in normal brain tissue group (P<0.05). The overall survival rate in high β3GNT9 expression group was significantly lower than that in low β3GNT9 expression group (P<0.05). Regression analyses suggested that β3GNT9, involved primarily in glucosamine degradation and extracellular matrix receptor interaction, could be an independent prognostic factor for glioblastoma. CIBERSORT and GEPIA database analyses showed that β3GNT9 was correlated with tumor infiltrating immune cells such as T follicular helper cells, activating natural killer cells, monocytes, macrophages, and eosinophils, thus affecting the immune microenvironment of glioblastoma. Cell experiments confirmed that β3GNT9 was highly expressed in A172, U87MG and U251 cell lines (P<0.05), and promoted the migration and invasion of glioblastoma (P<0.05).

Conclusion

The increased expression of β3GNT9 in glioblastoma can affect the immune microenvironment of glioblastoma and promote its migration and invasion. β3GNT9 can be used as a potential independent prognostic biomarker for patients with glioblastoma.

N-Glycosylation of LRP6 by B3GnT2 Promotes Wnt/β-Catenin Signalling

Reception of Wnt signals by cells is predominantly mediated by Frizzled receptors in conjunction with a co-receptor, the latter being LRP6 or LRP5 for the Wnt/β-catenin signalling pathway. It is important that cells maintain precise control of receptor activation events in order to properly regulate Wnt/β-catenin signalling as aberrant signalling can result in disease in humans. Phosphorylation of the intracellular domain (ICD) of LRP6 is well known to regulate Wntβ-catenin signalling; however, less is known for regulatory post-translational modification events within the extracellular domain (ECD). Using a cell culture-based expression screen for functional regulators of LRP6, we identified a glycosyltransferase, B3GnT2-like, from a teleost fish (medaka) cDNA library, that modifies LRP6 and regulates Wnt/β-catenin signalling. We provide both gain-of-function and loss-of-function evidence that the single human homolog, B3GnT2, promotes extension of polylactosamine chains at multiple N-glycans on LRP6, thereby enhancing trafficking of LRP6 to the plasma membrane and promoting Wnt/β-catenin signalling. Our findings further highlight the importance of LRP6 as a regulatory hub in Wnt signalling and provide one of the few examples of how a specific glycosyltransferase appears to selectively target a signalling pathway component to alter cellular signalling events.

Impact of a Saccharomyces cerevisiae fermentation product during an intestinal barrier challenge in lactating Holstein cows on ileal microbiota and markers of tissue structure and immunity

Feeding a Saccharomyces cerevisiae fermentation product (SCFP; NutriTek, Diamond V, Cedar Rapids, IA) during periods of metabolic stress is beneficial to the health of dairy cows partially through its effect on the gut microbiota. Whether SCFP alters the ileal microbiota in lactating cows during intestinal challenges induced by feed restriction (FR) is not known. We used 16S rRNA sequencing to assess if feeding SCFP during FR to induce gut barrier dysfunction alters microbiota profiles in the ileum. The mRNA abundance of key genes associated with tissue structures and immunity was also detected. Multiparous cows (97.1 ± 7.6 days in milk (DIM); n = 7 per treatment) fed a control diet or the control plus 19 g/d NutriTek for 9 wk were subjected to an FR challenge for 5 d, during which they were fed 40% of their ad libitum intake from the 7 d before FR. All cows were slaughtered at the end of FR. DNA extracted from ileal digesta was subjected to PacBio Full-Length 16S rRNA gene sequencing. High-quality amplicon sequence analyses were performed with Targeted Amplicon Diversity Analysis and MicrobiomeAnalyst. Functional analysis was performed and analyzed using PICRUSt and STAMP. Feeding SCFP did not (P > 0.05) alter dry matter intake, milk yield, or milk components during FR. In addition, SCFP supplementation tended (P = 0.07) to increase the relative abundance of Proteobacteria and Bifidobacterium animalis. Compared with controls, feeding SCFP increased the relative abundance of Lactobacillales (P = 0.03). Gluconokinase, oligosaccharide reducing-end xylanase, and 3-hydroxy acid dehydrogenase were among the enzymes overrepresented (P < 0.05) in response to feeding SCFP. Cows fed SCFP had a lower representation of adenosylcobalamin biosynthesis I (early cobalt insertion) and pyrimidine deoxyribonucleotides de novo biosynthesis III (P < 0.05). Subsets of the Firmicutes genus, Bacteroidota phylum, and Treponema genus were correlated with the mRNA abundance of genes associated with ileal integrity (GCNT3, GALNT5, B3GNT3, FN1, ITGA2, LAMB2) and inflammation (AOX1, GPX8, CXCL12, CXCL14, CCL4, SAA3). Our data indicated that the moderate FR induced dysfunction of the ileal microbiome, but feeding SCFP increased the abundance of some beneficial gut probiotic bacteria and other species related to tissue structures and immunity.

Elucidating Human Milk Oligosaccharide biosynthetic genes through network-based multi-omics integration

Human Milk Oligosaccharides (HMOs) are abundant carbohydrates fundamental to infant health and development. Although these oligosaccharides were discovered more than half a century ago, their biosynthesis in the mammary gland remains largely uncharacterized. Here, we use a systems biology framework that integrates glycan and RNA expression data to construct an HMO biosynthetic network and predict glycosyltransferases involved. To accomplish this, we construct models describing the most likely pathways for the synthesis of the oligosaccharides accounting for >95% of the HMO content in human milk. Through our models, we propose candidate genes for elongation, branching, fucosylation, and sialylation of HMOs. Our model aggregation approach recovers 2 of 2 previously known gene-enzyme relations and 2 of 3 empirically confirmed gene-enzyme relations. The top genes we propose for the remaining 5 linkage reactions are consistent with previously published literature. These results provide the molecular basis of HMO biosynthesis necessary to guide progress in HMO research and application with the goal of understanding and improving infant health and development.

Human milk oligosaccharides are fundamental to infant health. Here the authors deploy a multi-omics systems biology approach to elucidate their biosynthetic network, including the associated enzymes and likely structures of ambiguous oligosaccharides.

Broadening the phenotypic spectrum of Beta3GalT6-associated phenotypes

Biallelic mutations in B3GALT6, coding for a galactosyltransferase involved in the synthesis of glycosaminoglycans (GAGs), have been associated with various clinical conditions, causing spondyloepimetaphyseal dysplasia with joint laxity type 1 (SEMDJL1 or SEMDJL Beighton type), Al-Gazali syndrome (ALGAZ), and a severe progeroid form of Ehlers-Danlos syndrome (EDSSPD2). In the 2017 Ehlers-Danlos syndrome (EDS) classification, Beta3GalT6-related disorders were grouped in the spondylodysplastic EDSs together with spondylodysplastic EDSs due to B4GALT7 and SLC39A13 mutations. Herein, we describe a patient with a previously unreported homozygous pathogenic B3GALT6 variant resulting in a complex phenotype more severe than spondyloepimetaphyseal dysplasia with joint laxity type 1, and having dural ectasia and aortic dilation as additionally associated features, further broadening the phenotypic spectrum of the Beta3GalT6-related syndromes. We also document the utility of repeating sequencing in patients with uninformative exomes, particularly when performed by using "first generations" enrichment capture methods.

B3GNT3 acts as a carcinogenic factor in endometrial cancer via facilitating cell growth, invasion and migration through regulating RhoA/RAC1 pathway-associated markers

BACKGROUND

Aberrant expression of beta-1,3-N-acetylglucosaminyltransferase-3 (B3GNT3) has been frequently clarified in various cancers, however, its role in endometrial cancer (EC) has not been assessed in detail.

PURPOSE

This study aimed to investigate the biological role of B3GNT3 in EC and simply explored the detailed mechanism.

METHODS

The EC RNA-Seq dataset from TCGA database was applied to evaluate the expression of B3GNT3 and assess its role on prognostic value. HEC-1-A and KLE cell lines of EC were used to perform loss- and gain-of-function B3GNT3 assays respectively. Quantitative real-time PCR (qRT-PCR) and western blot were used to measure the mRNA and protein levels of indicated molecules respectively. Cell counting kit-8, clone formation tests, and Transwell assay served to determine the changes of proliferative, invasive and migratory abilities of EC cells after altering the expression of B3GNT3.

RESULTS

B3GNT3 was found to be highly expressed in EC tissues compared to normal tissues according to the online public databases, which confirmed by the following qRT-PCR in 3 EC cell lines. Besides, high B3GNT3 expression presented a worse overall survival in EC patients as compared with low B3GNT3 expression group. Furthermore, functional experiments in vitro indicated that B3GNT3 could facilitate the cell growth, invasion and migration. Moreover, we found that downregulation of B3GNT3 significantly reduced the expression level of GTP-RhoA and GTP-RAC1, whereas upregulation of B3GNT3 presented the opposite results.

CONCLUSION

The results of current study demonstrate that B3GNT3 acts as an oncogene that promotes EC cells growth, invasion and migration possibly through regulating the RhoA/RAC1 signaling pathway-related markers, suggesting that B3GNT3 may be a candidate biomarker for EC therapeutic intervention.

Identifying the prognostic significance of B3GNT3 with PD-L1 expression in lung adenocarcinoma

Background

As a novel treatment, programmed cell death protein 1 (PD-1) inhibitor appears to be less effective in tumors of lung adenocarcinoma patients with epidermal growth factor receptor (EGFR) mutation. Beta-1,3-N-acetylglucosaminyltransferase 3 (B3GNT3) has reported to be associated with programmed death ligand 1 (PD-L1)/PD-1 interaction. However, the relationship between B3GNT3 and PD-L1 and its prognostic significance in

EGFR

mutant status are still unknown.

Methods

B3GNT3 was identified through transcriptome sequencing and The Cancer Genome Atlas Lung Adenocarcinoma (TCGA-LUAD) database. Flow cytometry and real-time polymerase chain reaction were performed to investigate the association between B3GNT3, PD-L1, and EGFR. Then, B3GNT3 and PD-L1 expression were evaluated by immunohistochemical analysis in 145 surgically resected primary lung adenocarcinomas. The relationships between survival and B3GNT3, PD-L1, and EGFR status were assessed, and the potential prognostic factors in patients with B3GNT3 expression were identified.

Results

We found that EGFR activation induced PD-L1 expression, and EGFR tyrosine kinase inhibitor (TKI) could reduce PD-L1 protein in EGFR-TKI-sensitive HCC827 and PC9 cell lines. Subsequent analysis showed that EGFR inhibitor could also lead to both decreased PD-L1 and B3GNT3 mRNA expression. A total of 145 lung adenocarcinoma patients were included. PD-L1 >1% and B3GNT3-positive expression in patients might contribute to worse prognosis in both overall survival (OS) [hazard ratio (HR), 2.63; 95% confidence interval (CI), 0.98–7.06; P=0.048] and disease-free survival (DFS) (HR, 3.04; 95% CI, 1.13–8.14; P=0.019), especially in the PD-L1 ≥50% group. However, when patients were negative for B3GNT3, PD-L1, and EGFR (or “triple negative”), there were significant decreases in OS (HR, 5.44; 95% CI, 0.99–29.83; P=0.029) and DFS (HR, 7.24; 95% CI, 1.32–39.73; P=0.008). Positive B3GNT3 expression was a significant risk factor associated with lower DFS (HR, 3.30; P=0.043).

Conclusions

Our results indicate that the B3GNT3 expression is tightly correlated with PD-L1 expression and EGFR mutation status. B3GNT3 is associated with poor prognosis in lung adenocarcinoma patients. Collectively, these findings may offer new insight into enhancing immune therapy efficacy for lung adenocarcinoma patients.

Comparison of human poly-N-acetyl-lactosamine synthase structure with GT-A fold glycosyltransferases supports a modular assembly of catalytic subsites

Poly-N-acetyl-lactosamine (poly-LacNAc) structures are composed of repeating [-Galβ(1,4)-GlcNAcβ(1,3)-]n glycan extensions. They are found on both N- and O-glycoproteins and glycolipids and play an important role in development, immune function, and human disease. The majority of mammalian poly-LacNAc is synthesized by the alternating iterative action of β1,3-N-acetylglucosaminyltransferase 2 (B3GNT2) and β1,4-galactosyltransferases. B3GNT2 is in the largest mammalian glycosyltransferase family, GT31, but little is known about the structure, substrate recognition, or catalysis by family members. Here we report the structures of human B3GNT2 in complex with UDP:Mg2+ and in complex with both UDP:Mg2+ and a glycan acceptor, lacto-N-neotetraose. The B3GNT2 structure conserves the GT-A fold and the DxD motif that coordinates a Mg2+ ion for binding the UDP-GlcNAc sugar donor. The acceptor complex shows interactions with only the terminal Galβ(1,4)-GlcNAcβ(1,3)- disaccharide unit, which likely explains the specificity for both N- and O-glycan acceptors. Modeling of the UDP-GlcNAc donor supports a direct displacement inverting catalytic mechanism. Comparative structural analysis indicates that nucleotide sugar donors for GT-A fold glycosyltransferases bind in similar positions and conformations without conserving interacting residues, even for enzymes that use the same donor substrate. In contrast, the B3GNT2 acceptor binding site is consistent with prior models suggesting that the evolution of acceptor specificity involves loops inserted into the stable GT-A fold. These observations support the hypothesis that GT-A fold glycosyltransferases employ coevolving donor, acceptor, and catalytic subsite modules as templates to achieve the complex diversity of glycan linkages in biological systems.

B3GNT3: A prognostic biomarker associated with immune cell infiltration in pancreatic adenocarcinoma

Pancreatic cancer, one of the most malignant gastrointestinal tumors, is prone to liver metastasis. However, due to the lack of appropriate and comprehensive diagnostic methods, it is difficult to accurately predict the survival outcomes. Therefore, there is a need to identify effective biomarkers, such as UDP-GlcNAc: βGal β-1,3-N-acetylglucosaminyltransferase 3 (B3GNT3), that predict the survival outcome of patients with pancreatic cancer. In the present study, based on data from 171 cases of pancreatic cancer obtained from The Cancer Genome Atlas portal, the differential expression of mRNAs was screened by comparing cancerous tissues with adjacent tissues. Univariate Cox regression analysis demonstrated that B3GNT3 had prognostic capability and could be an independent prognostic factor for pancreatic adenocarcinoma (PAAD). Using the Tumor Immune Estimation Resource tool and Tumor-Immune System Interaction Database, a potential relationship between B3GNT3 expression and immune cell infiltration was identified in pancreatic carcinoma. Furthermore, 177 samples of pancreatic carcinoma were collected and the association of CD68 expression with B3GNT3 was assessed by immunohistochemical staining. B3GNT3 expression was associated with clinical outcomes in pancreatic carcinoma and related to infiltrating levels of immune cells, which indicated that B3GNT3 could be used as an immunotherapy target for PAAD.

Structures and mechanism of human glycosyltransferase β1,3-N-acetylglucosaminyltransferase 2 (B3GNT2), an important player in immune homeostasis

β1,3-N-acetylglucosaminyltransferases (B3GNTs) are Golgi-resident glycosyltransferases involved in the biosynthesis of poly-N-acetyl-lactosamine chains. They catalyze the addition of the N-acetylglucosamine to the N-acetyl-lactosamine repeat as a key step of the chain elongation process. Poly-N-acetyl-lactosamine is involved in the immune system in many ways. Particularly, its long chain has been demonstrated to suppress excessive immune responses. Among the characterized B3GNTs, B3GNT2 is the major poly-N-acetyl-lactosamine synthase, and deletion of its coding gene dramatically reduced the cell surface poly-N-acetyl-lactosamine and led to hypersensitive and hyperresponsive immunocytes. Despite the extensive functional studies, no structural information is available to understand the molecular mechanism of B3GNT2, as well as other B3GNTs. Here we present the structural and kinetic studies of the human B3GNT2. Five crystal structures of B3GNT2 have been determined in the unliganded, donor substrate-bound, acceptor substrate-bound, and product(s)-bound states at resolutions ranging from 1.85 to 2.35 Å. Kinetic study shows that the transglycosylation reaction follows a sequential mechanism. Critical residues involved in recognition of both donor and acceptor substrates as well as catalysis are identified. Mutations of these invariant residues impair B3GNT2 activity in cell assays. Structural comparison with other glycosyltransferases such as mouse Fringe reveals a novel N-terminal helical domain of B3GNTs that may stabilize the catalytic domain and distinguish among different acceptor substrates.

A phylogenetic view and functional annotation of the animal β1,3-glycosyltransferases of the GT31 CAZy family

The formation of β1,3-linkages on animal glycoconjugates is catalyzed by a subset of β1,3-glycosyltransferases grouped in the Carbohydrate-Active enZYmes family glycosyltransferase-31 (GT31). This family represents an extremely diverse set of β1,3-N-acetylglucosaminyltransferases [B3GNTs and Fringe β1,3-N-acetylglucosaminyltransferases], β1,3-N-acetylgalactosaminyltransferases (B3GALNTs), β1,3-galactosyltransferases [B3GALTs and core 1 β1,3-galactosyltransferases (C1GALTs)], β1,3-glucosyltransferase (B3GLCT) and β1,3-glucuronyl acid transferases (B3GLCATs or CHs). The mammalian enzymes were particularly well studied and shown to use a large variety of sugar donors and acceptor substrates leading to the formation of β1,3-linkages in various glycosylation pathways. In contrast, there are only a few studies related to other metazoan and lower vertebrates GT31 enzymes and the evolutionary relationships of these divergent sequences remain obscure. In this study, we used bioinformatics approaches to identify more than 920 of putative GT31 sequences in Metazoa, Fungi and Choanoflagellata revealing their deep ancestry. Sequence-based analysis shed light on conserved motifs and structural features that are signatures of all the GT31. We leverage pieces of evidence from gene structure, phylogenetic and sequence-based analyses to identify two major subgroups of GT31 named Fringe-related and B3GALT-related and demonstrate the existence of 10 orthologue groups in the Urmetazoa, the hypothetical last common ancestor of all animals. Finally, synteny and paralogy analysis unveiled the existence of 30 subfamilies in vertebrates, among which 5 are new and were named C1GALT2, C1GALT3, B3GALT8, B3GNT10 and B3GNT11. Altogether, these various approaches enabled us to propose the first comprehensive analysis of the metazoan GT31 disentangling their evolutionary relationships.

Metabolic engineering challenges of extending N-glycan pathways in Chinese hamster ovary cells

In mammalian cells, N-glycans may include multiple N-acetyllactosamine (poly-LacNAc) units that can play roles in various cellular functions and properties of therapeutic recombinant proteins. Previous studies indicated that β-1,3-N-acetylglucosaminyltransferase 2 (B3GNT2) and β-1,4-galactotransferase 1 (B4GALT1) are two of the primary glycosyltransferases involved in generating LacNAc units. In the current study, knocking out sialyltransferase genes slightly enhanced the LacNAc content (≥4 repeats per glycan) on recombinant EPO protein. Next, the role of single and dual-overexpression of B3GNT2 and B4GALT1 was explored in recombinant EPO-expressing Chinese hamster ovary (CHO) cells. While overexpression of B4GALT1 slightly enhanced the levels of large glycans on recombinant EPO, overexpression of B3GNT2 in EPO-expressing CHO cells significantly decreased the recombinant EPO LacNAc content, resulting in N-glycans terminating primarily with GlcNAc structures, a limited number of Gals, and nearly undetectable sialylation, which was also observed in sialyltransferases knock-out-B3GNT2 overexpression cell lines. Considering the nature of the binding domain motifs present on B3GNT2, which evolved from β1,3-galactosyltransferases, its overexpression may have competed and inhibited endogenous β1,4-galactosyltransferases for exposed GlcNAc residues on the N-glycans, resulting in premature termination of many N-glycans at GlcNAc. Furthermore, B3GNT2 overexpression enhanced intracellular UDP-GlcNAc and CMP-Neu5Ac content while slightly lowering UDP-Gal content. The presence of a sink for UDP-GlcNAc in the form of B3GNT2 with no disposition may have also elevated the intracellular levels of this nucleotide as well as its downstream product, CMP-Neu5Ac. Furthermore, we were unable to overexpress B4GALT1 at either the transcriptional or translational levels following initial B3GNT2 expression. Expression of B3GNT2 following initial expression of B4GALT1 was also problematic in that transcriptional and translational analysis indicated the accumulation of truncated B3GNT2 missing a section of the B3GNT2 trans-Golgi lumen domain while transmembrane and cytoplasmic domains were present. Given that glycosylation is a very complex intra-network process, the addition of one or more recombinant glycosyltransferases may have an unexpected influence on the expression and activities of glycosyltransferases, which can disrupt the nucleotide sugar levels and lead to unexpected modifications of the resulting N-glycan patterns.

Global analysis of human glycosyltransferases reveals novel targets for pancreatic cancer pathogenesis

BACKGROUND

Several reports have shown the role of glycosylation in pancreatic cancer (PC), but a global systematic screening of specific glycosyltransferases (glycoTs) in its progression remains unknown.

METHODS

We demonstrate a rigorous top-down approach using TCGA-based RNA-Seq analysis, multi-step validation using RT-qPCR, immunoblots and immunohistochemistry. We identified six unique glycoTs (B3GNT3, B4GALNT3, FUT3, FUT6, GCNT3 and MGAT3) in PC pathogenesis and studied their function using CRISPR/Cas9-based KD systems.

RESULTS

Serial metastatic in vitro models using T3M4 and HPAF/CD18, generated in house, exhibited decreases in B3GNT3, FUT3 and GCNT3 expression on increasing metastatic potential. Immunohistochemistry identified clinical significance for GCNT3, B4GALNT3 and MGAT3 in PC. Furthermore, the effects of B3GNT3, FUT3, GCNT3 and MGAT3 were shown on proliferation, migration, EMT and stem cell markers in CD18 cell line. Talniflumate, GCNT3 inhibitor, reduced colony formation and migration in T3M4 and CD18 cells. Moreover, we found that loss of GCNT3 suppresses PC progression and metastasis by downregulating cell cycle genes and β-catenin/MUC4 axis. For GCNT3, proteomics revealed downregulation of MUC5AC, MUC1, MUC5B including many other proteins.

CONCLUSIONS

Collectively, we demonstrate a critical role of O- and N-linked glycoTs in PC progression and delineate the mechanism encompassing the role of GCNT3 in PC.

Association between cancer antigen 19-9 and diabetes risk: A prospective and Mendelian randomization study

AIMS/INTRODUCTION

Elevated serum cancer antigen 19-9 (CA19-9) levels have been found in diabetes patients in most observational studies; however, whether there is a causal association between CA19-9 and diabetes mellitus is unclear.

MATERIALS AND METHODS

Our study was carried out based on the Dongfeng-Tongji cohort comprising 27,009 individuals. We first investigated the associations between serum CA19-9 levels and incident diabetes mellitus risk in a prospective cohort study (12,700 individuals). Then, we explored the potential causal relationship between CA19-9 and diabetes mellitus risk in a cross-sectional study (3,349 diabetes mellitus patients and 8,341 controls) using Mendelian randomization analysis. A weighted genetic risk score was calculated by adding the CA19-9 increasing alleles in five single-nucleotide polymorphisms (rs17271883, rs3760776 and rs3760775 in FUT6, rs11880333 in CA11, rs265548 in B3GNT3, and rs1047781 in FUT2), which were identified in a previous genome-wide association study on serum CA19-9 levels.

RESULTS

In the prospective study, a total of 1,004 incident diabetes mellitus patients were diagnosed during a mean 4.54-year follow-up period. Elevated serum CA19-9 level was associated with a higher incident diabetes risk after adjustment for confounders, with a hazard ratio of 1.20 (95% confidence interval 1.11-1.30) per standard deviation (12.17 U/mL) CA19-9 increase. Using the genetic score to estimate the unconfounded effect, we did not find a causal association of CA19-9 with diabetes risk (odds ratio per weighted CA19-9-increasing allele: 0.99, 95% confidence interval 0.94-1.04; P = 0.61).

CONCLUSIONS

The present study did not support a causal association of serum CA19-9 with diabetes risk. CA19-9 might be a potential biomarker of incident diabetes mellitus risk.

B3GNT3, a Direct Target of miR-149-5p, Promotes Lung Cancer Development and Indicates Poor Prognosis of Lung Cancer

Background

B3GNT3 (β1, 3-N-acetylglucosaminyltransferase-3) belongs to the β3GlcNAcT family and is essential to form extended core 1 oligosaccharides. Previous studies revealed that B3GNT3 expression was dysregulated in multiple cancers. Here, we aimed to understand the expression profile and function of B3GNT3 in lung cancer.

Materials and Methods

The expression of B3GNT3 was measured by immunohistochemistry and public database analysis. B3GNT3 was knocked down to evaluate the lung cancer cell proliferation, migration and invasion in in vitro and in vivo tumor formation experiments. miR-149-5p targeting B3GNT3 was identified with TargetScan analysis and confirmed with reporter assay. Overexpression of miR-149-5p was achieved using microRNA mimics and function of microRNA-149-5p/B3GNT3 axis was tested in vitro.

Results

B3GNT3 was upregulated in lung cancer, and B3GNT3 overexpression was associated with poor prognosis of lung cancer patients. High expression of B3GNT3 was associated with advanced TNM stages, larger tumor size, tumor metastasis and recurrence. Functionally, we demonstrated that knockdown of B3GNT3 suppressed lung cancer cell growth and invasion in vitro. Knockdown of B3GNT3 suppressed lung cancer development in a xenograft tumor model. Moreover, miR-149-5p was validated to negatively regulate B3GNT3 expression through directly targeting B3GNT3 3ʹ-UTR. Overexpression of miR-149-5p could antagonize the tumorigenesis effect of B3GNT3 in vitro.

Conclusion

In summary, our study demonstrated that B3GNT3 overexpression was correlated with poor prognosis of lung cancer patient, indicating that B3GNT3 could be a promising prognostic biomarker for lung cancer. miR-149-5p negatively regulated B3GNT3 expression, which might be utilized for therapeutic target in lung cancer.

Glycolysis-Based Genes Associated with the Clinical Outcome of Pancreatic Ductal Adenocarcinoma Identified by The Cancer Genome Atlas Data Analysis

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadly tumors in digestive tract tumors. Although there has been advancement in PDAC treatment, its prognosis still remains unsatisfactory, mainly because of dismal diagnosis. This article aims to develop new prognostic factors related to energy metabolism in PDAC and to use these genes for novel risk stratification. Hundred fifty messenger RNA (mRNA) expression profiles and clinicopathological data of PDAC were downloaded from The Cancer Genome Atlas dataset. The glycolysis pathway was the significant pathway based on the gene set enrichment analysis. We chose the glycolysis pathway-related 176 genes for further analysis. Multivariate Cox regression analysis and forward stepwise Cox regression model established a novel three-gene glycolytic signature (including MET, B3GNT3, and SPAG4) for PDAC patients' prognosis prediction. All 150 patients were classified into two groups by the median risk score. High-risk group had a worse outcome compared to the low-risk group. The risk score was also significantly correlated with age and radiotherapy. A nomogram, including the glycolytic gene signature, has shown some clinical net benefit for overall survival prediction. We also validated the validity and reliability in the Puleo dataset. This novel gene expression signature may be involved in the pathophysiology and used for risk stratification and prognosis prediction in PDAC.

Quantitative Super-Resolution Microscopy of the Mammalian Glycocalyx

The mammalian glycocalyx is a heavily glycosylated extramembrane compartment found on nearly every cell. Despite its relevance in both health and disease, studies of the glycocalyx remain hampered by a paucity of methods to spatially classify its components. We combine metabolic labeling, bioorthogonal chemistry, and super-resolution localization microscopy to image two constituents of cell-surface glycans, N-acetylgalactosamine (GalNAc) and sialic acid, with 10-20 nm precision in 2D and 3D. This approach enables two measurements: glycocalyx height and the distribution of individual sugars distal from the membrane. These measurements show that the glycocalyx exhibits nanoscale organization on both cell lines and primary human tumor cells. Additionally, we observe enhanced glycocalyx height in response to epithelial-to-mesenchymal transition and to oncogenic KRAS activation. In the latter case, we trace increased height to an effector gene, GALNT7. These data highlight the power of advanced imaging methods to provide molecular and functional insights into glycocalyx biology.

Novel role of O-glycosyltransferases GALNT3 and B3GNT3 in the self-renewal of pancreatic cancer stem cells

BACKGROUND

Glycosylation plays a critical role in the aggressiveness of pancreatic cancer (PC). Emerging evidences indicate significant involvement of cancer stem cells (CSCs) in PC aggressiveness. However, the importance of glycosylation in pancreatic cancer stem cells (PCSCs) is yet to be addressed. Hence, we evaluated the potential role of glycosylation in maintenance of stemness of PCSCs.

METHODS

Effect of glycosylation specific inhibitors on growth and PCSCs of PC cells was assessed by MTT assay and Side Population (SP) analysis. Isolated PCSCs/SP were characterized using molecular and functional assays. Expression of tumor-associated carbohydrate antigens (TACAs) was analyzed in PCSCs by western blotting. Effect of tunicamycin on PCSCs was analyzed by tumorsphere, clonogenicity, migration assay and immunoblotting for CSCs markers. The differential expression of glycogenes in PCSCs compared to non-CSCs were determined by RT-qPCR, immunoblotting and immunofluorescence. Co-expression of GALNT3 and B3GNT3 with CD44v6 was assessed in progression stages of KrasG12D; Pdx-1-Cre (KC) and KrasG12D; p53R172H; Pdx-1-Cre (KPC) tumors by immunofluorescence. Transient and CRISPR/Cas9 silencing of GALNT3 and B3GNT3 was performed to examine their effect on CSCs maintenance.

RESULTS

Inhibition of glycosylation decreased growth and CSCs/SP in PC cells. PCSCs overexpressed CSC markers (CD44v6, ESA, SOX2, SOX9 and ABCG2), exhibited global expressional variation of TACAs and showed higher self-renewal potential. Specifically, N-glycosylation inhibition, significantly decreased tumorsphere formation, migration, and clonogenicity of PCSCs, as well as hypo-glycosylated CD44v6 and ESA. Of note, glycosyltransferases (GFs), GALNT3 and B3GNT3, were significantly overexpressed in PCSCs and co-expressed with CD44v6 at advanced PDAC stages in KC and KPC tumors. Further, GALNT3 and B3GNT3 knockdown led to a decrease in the expression of cell surface markers (CD44v6 and ESA) and self-renewal markers (SOX2 and OCT3/4) in PCSCs. Interestingly, CD44v6 was modified with sialyl Lewis a in PCSCs. Finally, CRISPR/Cas9-mediated GALNT3 KO significantly decreased self-renewal, clonogenicity, and migratory capacity in PCSCs.

CONCLUSIONS

Taken together, for the first time, our study showed the importance of glycosylation in mediating growth, stemness, and maintenance of PCSCs. These results indicate that elevated GALNT3 and B3GNT3 expression in PCSCs regulate stemness through modulating CSC markers.

Identification of Poly-N-Acetyllactosamine-Carrying Glycoproteins from HL-60 Human Promyelocytic Leukemia Cells Using a Site-Specific Glycome Analysis Method, Glyco-RIDGE

To elucidate the relationship between the protein function and the diversity and heterogeneity of glycans conjugated to the protein, glycosylation sites, glycan variation, and glycan proportions at each site of the glycoprotein must be analyzed. Glycopeptide-based structural analysis technology using mass spectrometry has been developed; however, complicated analyses of complex spectra obtained by multistage fragmentation are necessary, and sensitivity and throughput of the analyses are low. Therefore, we developed a liquid chromatography/mass spectrometry (MS)-based glycopeptide analysis method to reveal the site-specific glycome (Glycan heterogeneity-based Relational IDentification of Glycopeptide signals on Elution profile, Glyco-RIDGE). This method used accurate masses and retention times of glycopeptides, without requiring MS2, and could be applied to complex mixtures. To increase the number of identified peptide, fractionation of sample glycopeptides for reduction of sample complexity is required. Therefore, in this study, glycopeptides were fractionated into four fractions by hydrophilic interaction chromatography, and each fraction was analyzed using the Glyco-RIDGE method. As a result, many glycopeptides having long glycans were enriched in the highest hydrophilic fraction. Based on the monosaccharide composition, these glycans were thought to be poly-N-acetyllactosamine (polylactosamine [pLN]), and 31 pLN-carrier proteins were identified in HL-60 cells. Gene ontology enrichment analysis revealed that pLN carriers included many molecules related to signal transduction, receptors, and cell adhesion. Thus, these findings provided important insights into the analysis of the glycoproteome using our novel Glyco-RIDGE method. Graphical Abstract ᅟ.

B3GNT3 overexpression is associated with unfavourable survival in non-small cell lung cancer

OBJECTIVE

The aim of this study was to evaluate the expression of beta-1,3-N-acetylglucosaminyltransferase-3 (B3GNT3) in non-small cell lung cancer (NSCLC) patients and to investigate the relevance of B3GNT3 expression in tumour prognosis.

METHODS

In this study, B3GNT3 expression was examined in five pairs of resectable NSCLC tissue by Western blot and in 42 pairs of resectable NSCLC tissue by quantitative real-time PCR (qRT-PCR). Immunohistochemistry and statistical analysis were performed to assess the relationship between B3GNT3 expression scores and clinicopathological parameters, as well as clinical prognosis in a retrospective cohort of 176 NSCLC patients.

RESULTS

Both B3GNT3 mRNA and protein expression levels were significantly higher in NSCLC tissue than in adjacent normal tissue. In the 176 NSCLC cases, a high B3GNT3 expression level was positively correlated with lymph node metastasis (P<0.001) and advanced TNM stage (P=0.043). Kaplan-Meier analysis indicated that patients with high B3GNT3 expression had significantly lower disease-free survival (DFS) (P<0.001) and overall survival (OS) (P<0.001) than those with low B3GNT3 expression. Moreover, in the multivariate analyses, B3GNT3 expression was an independent prognostic factor for DFS (HR 0.329, 95% CI 0.213 to 0.508, P<0.001) and OS (HR 0.383, 95% CI 0.249 to 0.588, P<0.001).

CONCLUSIONS

Our study demonstrated that high expression of B3GNT3 was associated with unfavourable DFS and OS in NSCLC patients, suggesting that B3GNT3 might be a potential prognostic biomarker for NSCLC.

Eradication of Triple-Negative Breast Cancer Cells by Targeting Glycosylated PD-L1

Protein glycosylation provides proteomic diversity in regulating protein localization, stability, and activity; it remains largely unknown whether the sugar moiety contributes to immunosuppression. In the study of immune receptor glycosylation, we showed that EGF induces programmed death ligand 1 (PD-L1) and receptor programmed cell death protein 1 (PD-1) interaction, requiring β-1,3-N-acetylglucosaminyl transferase (B3GNT3) expression in triple-negative breast cancer. Downregulation of B3GNT3 enhances cytotoxic T cell-mediated anti-tumor immunity. A monoclonal antibody targeting glycosylated PD-L1 (gPD-L1) blocks PD-L1/PD-1 interaction and promotes PD-L1 internalization and degradation. In addition to immune reactivation, drug-conjugated gPD-L1 antibody induces a potent cell-killing effect as well as a bystander-killing effect on adjacent cancer cells lacking PD-L1 expression without any detectable toxicity. Our work suggests targeting protein glycosylation as a potential strategy to enhance immune checkpoint therapy.

Genetic correction improves prediction efficiency of serum tumor biomarkers on digestive cancer risk in the elderly Chinese cohort study

Although serum tumor biomarkers alpha-fetoprotein (AFP), carbohydrate antigen 19-9 (CA19-9) and carcinoembryonic antigen (CEA) have been used in digestive cancer risk prediction, the prediction efficiency remains unsatisfactory. The aim of this study was to evaluate whether genetic correction could improve the efficiency of these biomarkers for prediction of digestive cancer risk. We conducted a prospective analysis in 9,808 healthy individuals based on a cohort study in the elderly Chinese population. The genotypes of reported single nucleotide polymorphisms (SNPs) associated with serum AFP, CA19-9 and CEA were used to estimate the genetic corrected levels of these markers. Unconditional logistic regression analysis was performed to evaluate the risk of digestive cancer. The Harrell's C-statistic was used to evaluate the discriminative ability of the raw levels and genetic corrected levels of biomarkers on digestive cancer risk. Up to October 2013, a total of 172 individuals were newly diagnosed with digestive cancer. With the genetic correction, higher odds ratios (ORs) for digestive cancer risk were found for the genetic corrected levels of tumor biomarkers compared with their raw serum levels (1.57 vs. 1.65 for AFP; 1.19 vs. 1.21 for CA19-9; 1.09 vs. 1.10 for CEA, respectively). The same results were observed in the Harrell's C-statistic analyses. Genetic correction improved the prediction efficiency of tumor biomarkers on the digestive cancer risk in an elderly Chinese population. Our findings provide evidence for further studies of genetic effects on tumor biomarker to improve the predictive efficiency on cancer risk.

A pilot exome-wide association study of age-related cataract in Koreans

Age-related cataract (ARC) is the most common cause of visual impairment and blindness worldwide. A previous study reported that genetic factors could explain approximately 50% of the heritability of cataract. However, a genetic predisposition to ARC and the contributing factors have not yet been elucidated in the Korean population. In this study, we assessed the influence of genetic polymorphisms on the risk of ARC in Koreans, including 156 cataract cases and 138 healthy adults. We conducted an exome-wide association study using Illumina Human Exome-12v1.2 platform to screen 244,770 single nucleotide polymorphisms (SNPs). No SNPs reached exome-wide significance level of association (P < 1×10⁻⁶). B3GNT4 rs7136356 showed the most significant association with ARC (P = 6.54×10⁻⁵). Two loci (MUC16 and P2RY2) among the top 20 ARC-associated SNPs were recognized as probably linked to cataractogenesis. Functions of these genes were potentially related to regulating dehydration or homeostasis of the eyes, and showed a potential association with dry eye disease. This finding suggests that mucin- and dry eye disease-related genes may play a significant role in cataractogenesis. Our study provides insight into the genetic predisposition of ARC in Koreans. Additional studies with larger sample sizes are required to confirm the results of this study.

A systematic framework to derive N-glycan biosynthesis process and the automated construction of glycosylation networks

Background

Abnormalities in glycan biosynthesis have been conclusively related to various diseases, whereas the complexity of the glycosylation process has impeded the quantitative analysis of biochemical experimental data for the identification of glycoforms contributing to disease. To overcome this limitation, the automatic construction of glycosylation reaction networks in silico is a critical step.

Results

In this paper, a framework K2014 is developed to automatically construct N-glycosylation networks in MATLAB with the involvement of the 27 most-known enzyme reaction rules of 22 enzymes, as an extension of previous model KB2005. A toolbox named Glycosylation Network Analysis Toolbox (GNAT) is applied to define network properties systematically, including linkages, stereochemical specificity and reaction conditions of enzymes. Our network shows a strong ability to predict a wider range of glycans produced by the enzymes encountered in the Golgi Apparatus in human cell expression systems.

Conclusions

Our results demonstrate a better understanding of the underlying glycosylation process and the potential of systems glycobiology tools for analyzing conventional biochemical or mass spectrometry-based experimental data quantitatively in a more realistic and practical way.

Biochemical and functional characterization of glycosylation-associated mutational landscapes in colon cancer

The molecular basis of aberrant protein glycosylation, a pathological alteration widespread in colorectal cancers (CRC), and the mechanisms by which it contributes to tumor progression remain largely unknown. We performed targeted re-sequencing of 430 glycosylation-associated genes in a series of patient-derived CRC cell lines (N = 31) and matched primary tumor tissues, identifying 12 new significantly mutated glycosylation-associated genes in colon cancer. In particular, we observed an enrichment of mutations in genes (B3GNT2, B4GALT2, ST6GALNAC2) involved in the biosynthesis of N- and Cores 1–3 O-linked glycans in the colon, accounting for ~16% of the CRCs tested. Analysis of independent large-scale tumor tissue datasets confirmed recurrent mutations within these genes in colon and other gastrointestinal cancers. Systematic biochemical and phenotypic characterization of the candidate wild-type and mutant glycosyltransferases demonstrated these mutations as either markedly altering protein localization, post-translational modification, encoded enzymatic activities and/or the migratory potential of colon carcinoma cells. These findings suggest that functionally deleterious mutations in glycosyltransferase genes in part underlie aberrant glycosylation, and contribute to the pathogenesis of molecular subsets of colon and other gastrointestinal malignancies.

Human Gb3/CD77 synthase reveals specificity toward two or four different acceptors depending on amino acid at position 211, creating P(k), P1 and NOR blood group antigens

Human Gb3/CD77 synthase (α1,4-galactosyltransferase, P(k) synthase), encoded by A4GALT gene, is known for synthesis of Gal(α1-4)Gal moiety in globotriaosylceramide (Gb3Cer, CD77, P(k) blood group antigen), a glycosphingolipid of the globo series. Recently, it was shown that c.631C > G mutation in A4GALT, which causes p.Q211E substitution in the open reading frame of the enzyme, broadens the enzyme specificity, making it able also to synthesize Gal(α1-4)GalNAc moiety, which constitutes the defining terminal disaccharide of the NOR antigen (carried by two glycosphingolipids: NOR1 and NOR2). Terminal Gal(α1-4)Gal disaccharide is also present in another glycosphingolipid blood group antigen, called P1, which together with P(k) and NOR comprises the P1PK blood group system. Despite several attempts, it was never clearly shown that P1 antigen is synthesized by Gb3/CD77 synthase, leaving open an alternative hypothesis that there are two homologous α1,4-galactosyltransferases in humans. In this study, using recombinant Gb3/CD77 synthase produced in insect cells, we show that the consensus enzyme synthesizes both the P(k) and P1 antigens, while its p.Q211E variant additionally synthesizes the NOR antigen. This is the first direct biochemical evidence that Gb3/CD77 synthase is able to synthesize two different glycosphingolipid antigens: P(k) and P1, and when p.Q211E substitution is present, the NOR antigen is also synthesized.

B3GNT3 Expression Is a Novel Marker Correlated with Pelvic Lymph Node Metastasis and Poor Clinical Outcome in Early-Stage Cervical Cancer

BACKGROUND

The β1,3-N-acetylglucosaminyltransferase-3 gene (B3GNT3) encodes a member of the B3GNT family that functions as the backbone structure of dimeric sialyl-Lewis A and is involved in L-selectin ligand biosynthesis, lymphocyte homing and lymphocyte trafficking. B3GNT3 has been implicated as an important element in the development of certain cancers. However, the characteristics of B3GNT3 in the development and progression of cancer remain largely unknown. Thus, our study aimed to investigate the expression pattern and the prognostic value of B3GNT3 in patients with early-stage cervical cancer.

METHODS

The mRNA and protein levels of B3GNT3 expression were examined in eight cervical cancer cell lines and ten paired cervical cancer tumors, using real-time PCR and western blotting, respectively. Immunohistochemistry (IHC) was used to analyze B3GNT3 protein expression in paraffin-embedded tissues from 196 early-stage cervical cancer patients. Statistical analyses were applied to evaluate the association between B3GNT3 expression scores and clinical parameters, as well as patient survival.

RESULTS

B3GNT3 expression was significantly upregulated in cervical cancer cell lines and lesions compared with normal cells and adjacent noncancerous cervical tissues. In the 196 cases of tested early-stage cervical cancer samples, the B3GNT3 protein level was positively correlated with high risk TYPES of human papillomavirus (HPV) infection (P = 0.026), FIGO stage (P < 0.001), tumor size (P = 0.025), tumor recurrence (P = 0.004), vital status (P < 0.001), concurrent chemotherapy and radiotherapy (P = 0.016), lymphovascular space involvement (P = 0.003) and most importantly, lymph node metastasis (P = 0.003). Patients with high B3GNT3 expression had a shorter overall survival (OS) and disease-free survival (DFS) compared with those with low expression of this protein. Multivariate analysis suggested that B3GNT3 expression is an independent prognostic indicator for cervical cancer patients.

CONCLUSIONS

Our study demonstrated that elevated B3GNT3 expression is associated with pelvic lymph node metastasis and poor outcome in early-stage cervical cancer patients. B3GNT3 may be a novel prognostic marker and therapeutic target for the treatment of cervical cancer.

Biosynthetic Machinery Involved in Aberrant Glycosylation: Promising Targets for Developing of Drugs Against Cancer

Cancer cells depend on altered metabolism and nutrient uptake to generate and keep the malignant phenotype. The hexosamine biosynthetic pathway is a branch of glucose metabolism that produces UDP-GlcNAc and its derivatives, UDP-GalNAc and CMP-Neu5Ac and donor substrates used in the production of glycoproteins and glycolipids. Growing evidence demonstrates that alteration of the pool of activated substrates might lead to different glycosylation and cell signaling. It is already well established that aberrant glycosylation can modulate tumor growth and malignant transformation in different cancer types. Therefore, biosynthetic machinery involved in the assembly of aberrant glycans are becoming prominent targets for anti-tumor drugs. This review describes three classes of glycosylation, O-GlcNAcylation, N-linked, and mucin type O-linked glycosylation, involved in tumor progression, their biosynthesis and highlights the available inhibitors as potential anti-tumor drugs.

O-glycan repertoires on a mucin-type reporter protein expressed in CHO cell pools transiently transfected with O-glycan core enzyme cDNAs

Glyco-engineering of host cells is used to increase efficacy, decrease immunogenicity and increase circulatory half-lives of protein biopharmaceuticals. The effect of transiently expressed O-glycan core chain glycosyltransferases on O-glycan biosynthesis pathways in CHO cells is reported. Liquid chromatography-mass spectrometry and Western blotting were used to map the O-glycome of a mucin-type fusion protein transiently co-transfected with β1,3-N-acetylglucosaminyltransferase 3 (extended C1 β3GnT3), core 2 β1,6-N-acetylglucosaminyltransferase I (C2 β3GnT1) or core 3 β1,3-N-acetylglucosaminyltransferase 6 (C3 β3GnT6) in CHO cells. Extended core 1 (GlcNAcβ1,3Galβ1,3GalNAc) and core 3 (GlcNAcβ1,3GalNAc), and increased expression of core 2 [Galβ1,3(GlcNAcβ1,6)GalNAc], O-glycans were generated on P-selectin glycoprotein ligand-1/mouse IgG2b (PSGL1/mIgG2b). Endogenous poly-N-acetyllactosamine (poly-LacNAc) synthase elongated extended core 1 and core 3 generating O-glycans with up to five LacNAc repeats. Low amounts of core 3 O-glycans appeared upon extended C1 β3GnT3 expression. The α2,6-sialylated type 2 chain was detected upon co-transfection with the β-galactoside α2,6-sialyltransferase I. N-acetylglucosamine-6-O-sulfotransferase 2 transferred sulfate to carbon 6 of GlcNAc in poly-LacNAc sequences. CHO cells with its known O-glycan repertoire can be used to express recombinant mucin-type proteins together with selected glycosyltransferases in order to recreate carbohydrate determinants on defined O-glycan chains. They will become important tools for assessing the core chain-dependent binding activity of carbohydrate-binding proteins.

B4GAT1 is the priming enzyme for the LARGE-dependent functional glycosylation of α-dystroglycan

Recent studies demonstrated that mutations in B3GNT1, an enzyme proposed to be involved in poly-N-acetyllactosamine synthesis, were causal for congenital muscular dystrophy with hypoglycosylation of α-dystroglycan (secondary dystroglycanopathies). Since defects in the O-mannosylation protein glycosylation pathway are primarily responsible for dystroglycanopathies and with no established O-mannose initiated structures containing a β3 linked GlcNAc known, we biochemically interrogated this human enzyme. Here we report this enzyme is not a β-1,3-N-acetylglucosaminyltransferase with catalytic activity towards β-galactose but rather a β-1,4-glucuronyltransferase, designated B4GAT1, towards both α- and β-anomers of xylose. The dual-activity LARGE enzyme is capable of extending products of B4GAT1 and we provide experimental evidence that B4GAT1 is the priming enzyme for LARGE. Our results further define the functional O-mannosylated glycan structure and indicate that B4GAT1 is involved in the initiation of the LARGE-dependent repeating disaccharide that is necessary for extracellular matrix protein binding to O-mannosylated α-dystroglycan that is lacking in secondary dystroglycanopathies.

Knockdown of β3GnT8 reverses 5-fluorouracil resistance in human colorectal cancer cells via inhibition the biosynthesis of polylactosamine-type N-glycans

Aberrant glycosylation is known to be associated with cancer chemoresistance. β-1,3-N-acetyl-glucosaminyltransferase (β3GnT)8, which synthesizes polylactosamine on β1-6 branched N-glycans, is dramatically upregulated in colorectal cancer (CRC). 5-Fluorouracil (5-FU) resistance remains a major obstacle to the chemotherapy of CRC. However, little is known with regard to the correlation between 5‑FU resistance and the expression of β3GnT8 in CRC. In this study, a 5-FU‑resistant cell line (SW620/5-FU) was generated, and 50% inhibition concentration (IC50) of 5-FU was determined by MTT assay. Flow cytometry and lectin blot analysis were performed to detect the alteration of polylactosamine structures. Quantitative RT-‑PCR and western blot analysis were used to identify and evaluate candidate genes involved in the synthesis of polylactosamine in SW620/5-FU cells. We found polylactosamine chains were significantly increased in SW620/5-FU cells. Inhibition of the biosynthesis of polylactosamine by 3'-azidothymidine (AZT) was able to reduce 5-FU tolerance. Further studies showed that β3GnT8 expression was also upregulated in 5-FU‑resistant cancer cells, and knockdown of β3GnT8 by RNA interference reversed 5-FU resistance through, at least partly, by suppressing the formation of polylactosamine. In conclusion, the alteration of β3GnT8 in CRC cells correlates with tumor sensitivity to the chemotherapeutic drug and has significant implication for the development of new treatment strategies.

β3GnT8 plays an important role in CD147 signal transduction as an upstream modulator of MMP production in tumor cells

Aberrant carbohydration by related glycosyl-transferases plays an important role in the progression of cancer. This study focused on the ablity of β-1,3-N-acetyl-glucosaminyltransferase-8 (β3GnT8) to regulate MMP-2 expression through regulation of the CD147 signal transduction pathway in cancer cells. β3GnT8 catalyzes and then extends a polylactosamine chain specifically on β1-6-branched tetraantennary N-glycans. CD147 is a major carrier of β1-6-branched polylactosamine sugars on tumor cells, and the high glycoform of CD147 (HG-CD147) induces matrix metalloproteinase (MMP) production. In the present study, we analyzed β3GnT8 mRNA expression in 6 cancer cell lines (MCF-7, M231, LN229, U87, SGC-7901 and U251). We found that β3GnT8 expression in the LN229, SGC-7901 and U251 cell lines was higher than that in the other cell lines. Therefore, we established β3GnT8-knockdown cell lines derived from the LN229 and SGC-7901 cell lines to examine the level of polylactosamine and CD147 N-glycosylation. In addition, tunicamycin is widely used as an inhibitor of N-linked glycosylation. Hence, various concentrations of tunicamycin were used to treat the cells in order to study its influence on CD147 N-glycosylation and MMP-2 expression. In conclusion, we found that β3GnT8 regulated the level of N-glycans on CD147 and that N-glycosylation of CD147 has an important effect on MMP-2 expression. Our findings suggest that β3GnT8 affects the signal transduction pathway of MMP-2 by altering the N-glycan structure of CD147.

Differential expression patterns of N-acetylglucosaminyl transferases and polylactosamines in uterine lesions

Polylactosamine (polyLacNAc) is a fundamental structure in glycoconjugates and it is expressed in specific cells/tissues associated with the development and carcinogenesis. β1,3-N-acetylglucosaminyl transferases ((β3GnTs) play an important role in polyLacNAc synthesis, however the roles of these glycosyltransferases and their products in cancer progression are still unclear. In this sense, this work aimed to evaluate differential expression pattern of the N-acetylglucosaminyl transferases and polylactosamines in invasive and premalignant lesions of the uterus cervix. The expression of β3GnT2 and β3GnT3 were evaluated in normal (n=10) and uterine cervix lesions (n=120), both malignant [squamous carcinoma (SC)] and premalignant [cervical intraepithelial neoplasia (CIN), grades 1, 2 and 3] using immunohistochemistry. Besides, lectin histochemistry with Phytolacca americana lectin (PWM) and Wheat germ agglutinin (WGA) was also carried out to observe the presence of polyLacNAc chains and N-acetylglucosamine (GlcNAc), respectively. The β3GnT3 was expressed in almost all samples (99%) and β3GnT2 was higher expressed in disease samples mainly in CIN 3, when compared with normal (P=0.002), CIN 1 (P=0.009) and CIN 2 (P=0.03). The expression of polyLacNAc was higher is SC samples, when compared with normal (P=0.03), CIN 1 (P=0.02) and CIN 3 (P=0.004), and was observed only nuclear expression in nearly 50% of the SC samples, showing a statistically significant when compared with normal (P=0.01), CIN 1 (P=0.002), CIN 2 (P=0.007) and CIN 3 (P=0.04). Deferring from transferases and polyLacNAc chains, GlcNAc (WGA ligand) reveals a gradual staining pattern decrease with the increase of the lesion degree, being more expressed in CIN 1 lesions when compared with normal (P<0.0001), CIN 2 (P<0.0001), SC (P<0.0001) and CIN 3 (P=0.0003). Our data reveal that β3GnT2 and polyLacNAc may be involved in the progression of the pre-malignant lesions of the human uterine cervix. In addition, polyLacNAc expression only in the nucleus can be associated a poor prognostic in uterine lesions.

N-linked polylactosamine glycan synthesis is regulated by co-expression of β3GnT2 and GCNT2

Poly-N-acetyllactosamine (PLN) is a unique glycan composed of repeating units of the common disaccharide (Galβ1,4-GlcNAcβ1,3)n . The expression of PLN on glycoprotein core structures minimally requires enzyme activities for β1,4-galactosyltransferase (β4GalT) and β1,3-N-acetylglucosminyltransferase (β3GnT). Because β4GalTs are ubiquitous in most cells, PLN expression is generally ascribed to the tissue-specific transcription of eight known β3GnT genes in mice. In the olfactory epithelium (OE), β3GnT2 regulates expression of extended PLN chains that are essential for axon guidance and neuronal survival. N-glycan branching and core composition, however, can also modulate the extent of PLN modification. Here, we show for the first time that the β1,6-branching glycosyltransferase GCNT2 (formerly known as IGnT) is expressed at high levels specifically in the OE and other sensory ganglia. Postnatally, GCNT2 is maintained in mature olfactory neurons that co-express β3GnT2 and PLN. This highly specific co-expression suggests that GCNT2 and β3GnT2 function cooperatively in PLN synthesis. In support of this, β3GnT2 and GCNT2 co-transfection in HEK293T cells results in high levels of PLN expression on the cell surface and on adenylyl cyclase 3, a major carrier of PLN glycans in the OE. These data clearly suggest that GCNT2 functions in vivo together with β3GnT2 to determine PLN levels in olfactory neurons by regulating β1,6-branches that promote PLN extension.

A genome wide association study of genetic loci that influence tumour biomarkers cancer antigen 19-9, carcinoembryonic antigen and α fetoprotein and their associations with cancer risk

OBJECTIVE

Tumour biomarkers are used as indicators for cancer screening and as predictors for therapeutic responses and prognoses in cancer patients. We aimed to identify genetic loci that influence concentrations of cancer antigen 19-9 (CA19-9), carcinoembryonic antigen (CEA) and α fetoprotein (AFP), and investigated the associations between the significant single nucleotide polymorphisms (SNPs) with risks of oesophageal squamous cell (OSCC), pancreatic and hepatocellular cancers.

DESIGN

We carried out a genome wide association study on plasma CA19-9, CEA and AFP concentrations in 3451 healthy Han Chinese and validated the results in 10 326 individuals. Significant SNPs were further investigated in three case control studies (2031 OSCC cases and 2044 controls; 981 pancreatic cancer cases and 1991 controls; and 348 hepatocellular cancer cases and 359 controls).

RESULTS

The analyses showed association peaks on three genetic loci for CA19-9 (FUT6-FUT3 at 19p13.3, FUT2-CA11 at 19q13.3 and B3GNT3 at 19p13.1; p=1.16×10(-13)-3.30×10(-290)); four for CEA (ABO at 9q34.2, FUT6 at 19p13.3, FUT2 at 19q13.3 and FAM3B at 21q22.3; p=3.33×10(-22)-5.81×10(-209)); and two for AFP (AFP at 4q11-q13 and HISPPD2A at 15q15.3; p=3.27×10(-18) and 1.28×10(-14)). These explained 17.14% of the variations in CA19-9, 8.95% in CEA and 0.57% in AFP concentrations. Significant ABO variants were also associated with risk of OSCC and pancreatic cancers, and AFP variants with risk of hepatocellular cancer (p<0.05).

CONCLUSIONS

This study identified several loci associated with CA19-9, CEA and AFP concentrations. The ABO variants were associated with risk of OSCC and pancreatic cancers and AFP variants with risk of hepatocellular cancer.

B3GNT3 expression suppresses cell migration and invasion and predicts favorable outcomes in neuroblastoma

Aberrant expression of the simple mucin-type carbohydrate antigens such as T, Tn, sialyl-T and sialyl-Tn is associated with poor prognosis in several cancers. β1,3-N-acetylglucosaminyltransferase-3 (B3GNT3), a member of the β3GlcNAcT family, is responsible for forming extended core 1 (T antigen) oligosaccharides. The role of B3GNT3, which is expressed in various tissues including human fetal brain, in regulating neuroblastoma (NB) formation and cell behaviors remains unclear. Here, we showed that increased B3GNT3 expression evaluated using immunohistochemistry in NB tumor tissues correlated well with the histological grade of differentiation as well as a favorable Shimada's subset of pathology. Univariate and multivariate analyses revealed that positive B3GNT3 expression in tumor tissues predicted a favorable prognosis in NB patients independent of other prognostic markers. B3GNT3 overexpression suppresses T antigen formation and malignant phenotypes including migration and invasion of SK-N-SH cells, whereas B3GNT3 knockdown enhances these phenotypes of SK-N-SH cells. Moreover, B3GNT3 expression decreased phosphorylation of focal adhesion kinase (FAK), Src, paxillin, Akt and ERK1/2. We conclude that B3GNT3 predicts a favorable cancer behavior of NB and suppresses malignant phenotypes by modulating mucin-type O-glycosylation and signaling in NB cells.

Attenuation of fibroblast growth factor signaling by poly-N-acetyllactosamine type glycans

Fibroblast growth factors (FGFs) and their receptors are expressed in a variety of mammalian tissues, playing a role in development and cell proliferation. While analyzing human sperm motility, we found that sperm treated with endo-β-galactosidase (EBG), which specifically hydrolyzes poly-N-acetyllactosamine type glycans (polyLacs), enhanced motility. Mass spectrometry analysis revealed that sperm-associated polyLacs are heavily fucosylated, consistent with Lewis Y antigen. Immunohistochemistry of epididymis using an anti-Lewis Y antibody before and after EBG treatment suggested that polyLacs carrying the Lewis Y epitope are synthesized in epididymal epithelia and secreted to seminal fluid. EBG-treated sperm elevated cAMP levels and calcium influx, indicating activation of fibroblast growth factor signaling. Seminal fluid polyLacs bound to FGFs in vitro, and impaired FGF-mediated signaling in HEK293T cells.

Identification of 15 new psoriasis susceptibility loci highlights the role of innate immunity

To gain further insight into the genetic architecture of psoriasis, we conducted a meta-analysis of 3 genome-wide association studies (GWAS) and 2 independent data sets genotyped on the Immunochip, including 10,588 cases and 22,806 controls. We identified 15 new susceptibility loci, increasing to 36 the number associated with psoriasis in European individuals. We also identified, using conditional analyses, five independent signals within previously known loci. The newly identified loci shared with other autoimmune diseases include candidate genes with roles in regulating T-cell function (such as RUNX3, TAGAP and STAT3). Notably, they included candidate genes whose products are involved in innate host defense, including interferon-mediated antiviral responses (DDX58), macrophage activation (ZC3H12C) and nuclear factor (NF)-κB signaling (CARD14 and CARM1). These results portend a better understanding of shared and distinctive genetic determinants of immune-mediated inflammatory disorders and emphasize the importance of the skin in innate and acquired host defense.

Regulation and function of axon guidance and adhesion molecules during olfactory map formation

The olfactory system presents a practical model for investigating basic mechanisms involved in patterning connections between peripheral sensory neurons and central targets. Our understanding of olfactory map formation was advanced greatly by the discovery of cAMP signaling as an important determinant of glomerular positioning in the olfactory bulb. Additionally, several cell adhesion molecules have been identified recently that are proposed to regulate homotypic interactions among projecting axons. From these studies a model has emerged to partially explain the wiring of axons from widely dispersed neuron populations in the nasal cavity to relatively stereotyped glomerular positions. These advances have revitalized interest in axon guidance molecules in establishing olfactory topography, but also open new questions regarding how these patterns of guidance cues are established and function, and what other pathways, such as glycosylation, might be involved. This review summarizes the current state of this field and the important molecules that impact on cAMP-dependent mechanism in olfactory axon guidance.

The i blood group antigen as a marker for umbilical cord blood-derived mesenchymal stem cells

Multipotent mesenchymal stem cells (MSCs) offer great promise for future regenerative and anti-inflammatory therapies. However, there is a lack of methods to quickly and efficiently isolate, characterize, and ex vivo expand desired cell populations for therapeutic purposes. Single markers to identify cell populations have not been characterized; instead, all characterizations rely on panels of functional and phenotypical properties. Glycan epitopes can be used for identifying and isolating specific cell types from heterogeneous populations, on the basis of their cell-type specific expression and prominent cell surface localization. We have now studied in detail the cell surface expression of the blood group i epitope (linear poly-N-acetyllactosamine chain) in umbilical cord blood (UCB)-derived MSCs. We used flow cytometry and mass spectrometric glycan analysis and discovered that linear poly-N-acetyllactosamine structures are expressed in UCB-derived MSCs, but not in cells differentiated from them. We further verified the findings by mass spectrometric glycan analysis. Gene expression analysis indicated that the stem-cell specific expression of the i antigen is determined by β3-N-acetylglucosaminyltransferase 5. The i antigen is a ligand for the galectin family of soluble lectins. We found concomitant cell surface expression of galectin-3, which has been reported to mediate the immunosuppressive effects exerted by MSCs. The i antigen may serve as an endogenous ligand for this immunosuppressive agent in the MSC microenvironment. Based on these findings, we suggest that linear poly-N-acetyllactosamine could be used as a novel UCB-MSC marker either alone or within an array of MSC markers.

β3GnT2 maintains adenylyl cyclase-3 signaling and axon guidance molecule expression in the olfactory epithelium

In the olfactory epithelium (OE), odorant receptor stimulation generates cAMP signals that function in both odor detection and the regulation of axon guidance molecule expression. The enzyme that synthesizes cAMP, adenylyl cyclase 3 (AC3), is coexpressed in olfactory sensory neurons (OSNs) with poly-N-acetyllactosamine (PLN) oligosaccharides determined by the glycosyltransferase β3GnT2. The loss of either enzyme results in similar defects in olfactory bulb (OB) innervation and OSN survival, suggesting that glycosylation may be important for AC3 function. We show here that AC3 is extensively modified with N-linked PLN, which is essential for AC3 activity and localization. On Western blots, AC3 from the wild-type OE migrates diffusely as a heavily glycosylated 200 kDa band that interacts with the PLN-binding lectin LEA. AC3 from the β3GnT2(-/-) OE loses these PLN modifications, migrating instead as a 140 kDa glycoprotein. Furthermore, basal and forskolin-stimulated cAMP production is reduced 80-90% in the β3GnT2(-/-) OE. Although AC3 traffics normally to null OSN cilia, it is absent from axon projections that aberrantly target the OB. The cAMP-dependent guidance receptor neuropilin-1 is also lost from β3GnT2(-/-) OSNs and axons, while semaphorin-3A ligand expression is upregulated. In addition, kirrel2, a mosaically expressed adhesion molecule that functions in axon sorting, is absent from β3GnT2(-/-) OB projections. These results demonstrate that PLN glycans are essential in OSNs for proper AC3 localization and function. We propose that the loss of cAMP-dependent guidance cues is also a critical factor in the severe axon guidance defects observed in β3GnT2(-/-) mice.

Subcellular localization and tumor distribution of human beta3-galactosyltransferase by beta3GalT7 antiserum

A novel member of the human beta3-galactosyltransferase family, the beta3GalT7 gene (AY277592, EC2.4.1.-) was first isolated and cloned by our laboratory. To further study its functions, we constructed a prokaryotic expression system of beta3GalT7 and obtained anti-beta3GalT7 polyclonal antiserum by immunizing rabbit with purified beta3GalT7 protein. Using the antiserum, the expression of beta3GalT7 in various tissues and cell lines was analyzed by Western blot and immunochemical assays. Immunochemistry analysis showed the enzyme was expressed significantly higher in some tumor tissues than in normal tissues, indicating its biofunction in tumorogenesis. By immunofluorescence, the enzyme was observed highly accumulated in cytoplasm around nuclear membrane, implying that beta3GalT7 may play an important role in the assembly of galactose in RER and Golgi.

Structural and biochemical aspects of keratan sulphate in the cornea

Keratan sulphate (KS) is the predominant glycosaminoglycan (GAG) in the cornea of the eye, where it exists in proteoglycan (PG) form. KS-PGs have long been thought to play a pivotal role in the establishment and maintenance of the array of regularly-spaced and uniformly- thin collagen fibrils which make up the corneal stroma. This characteristic arrangement of fibrils allows light to pass through the cornea. Indeed, perturbations to the synthesis of KS-PG core proteins in genetically altered mice lead to structural matrix alterations and corneal opacification. Similarly, mutations in enzymes responsible for the sulphation of KS-GAG chains are causative for the inherited human disease, macular corneal dystrophy, which is manifested clinically by progressive corneal cloudiness starting in young adulthood.