The cancer-associated glycosyltransferase GnT-V (MGAT5) recognizes the N-glycan core via residues outside its catalytic pocket

N-acetylglucosaminyltransferase-V (GnT-V or MGAT5) is a glycosyltransferase involved in cancer metastasis that creates the β1,6-branch on N-glycans of target proteins such as cell adhesion molecules and cell surface receptors. The 3D structure of GnT-V and its catalytic site, which are critical for the interaction with the N-glycan terminal, have already been revealed. However, it remains unclear how GnT-V recognizes the core part of N-glycan or the polypeptide part of the acceptor. Using molecular dynamics simulations and biochemical experiments, we found that several residues outside the catalytic pocket are likely involved in the recognition of the core part of N-glycan. Furthermore, our simulation suggested that UDP binding affects the orientation of the acceptor due to the conformational change at the Manα1,6-Man linkage. These findings provide new insights into how GnT-V recognizes its glycoprotein substrates.

RUNX2 promotes gastric cancer progression through the transcriptional activation of MGAT5 and MMP13

Introduction

RUNX2 is overexpressed in gastric cancer but the mechanism(s) through which it promotes tumor progression remain undefined. Here, we investigated the role of RUNX2 on gastric cancer pathogenesis at the molecular level.

Methods

The qRT-PCR and western bolt were utilized to examine the mRNA and protein levels. CCK-8, Transwell and wound healing assays were used to measure cell proliferation, invasion and migration. CHIP-PCR gel electrophoresis was used to verify RUNX2 as a transcription factor for MMP13 and MGAT5. The in vivo assay was utilized to assess tumor growth. In vivo assay was used to evaluate tumor growth, aberrant expression of RUNX2 and lung metastasis of gastric cancer.

Results

RUNX2 is overexpressed in MKN-45 and AGS cells. Genetic RUNX2 silencing reduced the proliferation, invasion and migration of MKN-45 and AGS cells. Analysis of the gastric cancer samples from the database revealed a significant positive correlation between MGAT5, MMP13, and RUNX2 expression. JASPAR analysis revealed that there was a potential binding site of RUNX2 in the promoter regions of MGAT5 and MMP13, and the experimental results confirmed that RUNX2 could regulate the expression of MGAT5 and MMP13 respectively. In vivo assays confirmed the aberrant expression of RUNX2 in mouse models of gastric cancer and reduced growth and lung metastasis in RUNX2 silenced xenograft tumors assessed.

Conclusion

Collectively, these data reveal that RUNX2 enhances MGAT5 and MMP13 expression in gastric cancer cells and represents a biomarker and potential therapeutic target for gastric cancer therapy.

Regulation of neural stem cell differentiation and brain development by MGAT5-mediated N-glycosylation

Undifferentiated neural stem and progenitor cells (NSPCs) encounter extracellular signals that bind plasma membrane proteins and influence differentiation. Membrane proteins are regulated by N-linked glycosylation, making it possible that glycosylation plays a critical role in cell differentiation. We assessed enzymes that control N-glycosylation in NSPCs and found that loss of the enzyme responsible for generating β1,6-branched N-glycans, N-acetylglucosaminyltransferase V (MGAT5), led to specific changes in NSPC differentiation in vitro and in vivo. Mgat5 homozygous null NSPCs in culture formed more neurons and fewer astrocytes compared with wild-type controls. In the brain cerebral cortex, loss of MGAT5 caused accelerated neuronal differentiation. Rapid neuronal differentiation led to depletion of cells in the NSPC niche, resulting in a shift in cortical neuron layers in Mgat5 null mice. Glycosylation enzyme MGAT5 plays a critical and previously unrecognized role in cell differentiation and early brain development.

Aberrant N-glycosylation in cancer: MGAT5 and β1,6-GlcNAc branched N-glycans as critical regulators of tumor development and progression

BACKGROUND

Changes in protein glycosylation are widely observed in tumor cells. N-glycan branching through adding β1,6-linked N-acetylglucosamine (β1,6-GlcNAc) to an α1,6-linked mannose, which is catalyzed by the N-acetylglucosaminyltransferase V (MGAT5 or GnT-V), is one of the most frequently observed tumor-associated glycan structure formed. Increased levels of this branching structure play a pro-tumoral role in various ways, for example, through the stabilization of growth factor receptors, the destabilization of intercellular adhesion, or the acquisition of a migratory phenotype.

CONCLUSION

In this review, we provide an updated and comprehensive summary of the physiological and pathophysiological roles of MGAT5 and β1,6-GlcNAc branched N-glycans, including their regulatory mechanisms. Specific emphasis is given to the role of MGAT5 and β1,6-GlcNAc branched N-glycans in cellular mechanisms that contribute to the development and progression of solid tumors. We also provide insight into possible future clinical implications, such as the use of MGAT5 as a prognostic biomarker.

ISLR interacts with MGAT5 to promote the malignant progression of human gastric cancer AGS cells

Objectives

Gastric cancer is a common malignant tumor with high morbidity and mortality. The present study aimed to investigate the role of the immunoglobulin superfamily containing leucine-rich repeat (ISLR) gene in gastric cancer and examine whether ISLR could interact with N-acetylglucosaminyltransferase V (MGAT5) to affect the malignant progression of gastric cancer.

Materials and Methods

The expression of ISLR and MGAT5 in human normal gastric epithelial cells and human gastric cancer cells, and the transfection efficiency of ISLR interference plasmids and MGAT5 overexpression plasmids were all detected by reverse transcription-quantitative PCR (RT-qPCR) and western blot. The viability, proliferation, migration and invasion, and epithelial-mesenchymal transition (EMT) of gastric cancer cells after indicated transfection were detected by Cell counting kit-8 (CCK-8) assay, 5-ethynyl-2'-deoxyuridine (EdU) staining, wound healing assay, and transwell assay. The interaction between ISLR and MGAT5 was confirmed by co-immunoprecipitation. The expression of proteins related to migration, invasion, and EMT was detected by immunofluorescence and western blot.

Results

As a result, ISLR was highly expressed in gastric cancer and was associated with poor prognosis. Interference with ISLR inhibited the viability, proliferation, migration, invasion, and EMT of gastric cancer cells. ISLR interacted with MGAT5 in gastric cancer cells. MGAT5 overexpression weakened the effects of ISLR knockdown on suppressing the viability, proliferation, migration, invasion, and EMT of gastric cancer cells.

Conclusion

ISLR interacted with MGAT5 to promote the malignant progression of gastric cancer.

Complex N-Linked Glycosylation: A Potential Modifier of Niemann-Pick Disease, Type C1 Pathology

Complex asparagine-linked glycosylation plays key roles in cellular functions, including cellular signaling, protein stability, and immune response. Previously, we characterized the appearance of a complex asparagine-linked glycosylated form of lysosome-associated membrane protein 1 (LAMP1) in the cerebellum of Npc1^-/- mice. This LAMP1 form was found on activated microglia, and its appearance correlated both spatially and temporally with cerebellar Purkinje neuron loss. To test the importance of complex asparagine-linked glycosylation in NPC1 pathology, we generated NPC1 knock-out mice deficient in MGAT5, a key Golgi-resident glycosyl transferase involved in complex asparagine-linked glycosylation. Our results show that Mgat5^-/-:Npc1^-/- mice were smaller than Mgat5^+/+:Npc1^-/- mice, and exhibited earlier NPC1 disease onset and reduced lifespan. Western blot and lectin binding analyses of cerebellar extracts confirmed the reduction in complex asparagine-linked glycosylation, and the absence of the hyper-glycosylated LAMP1 previously observed. Western blot analysis of cerebellar extracts demonstrated reduced calbindin staining in Mgat5^-/-:Npc1^-/- mice compared to Mgat5^+/+:Npc1^-/- mutant mice, and immunofluorescent staining of cerebellar sections indicated decreased levels of Purkinje neurons and increased astrogliosis in Mgat5^-/-:Npc1^-/- mice. Our results suggest that reduced asparagine-linked glycosylation increases NPC1 disease severity in mice, and leads to the hypothesis that mutations in genes involved in asparagine-linked glycosylation may contribute to disease severity progression in individuals with NPC1. To examine this with respect to MGAT5, we analyzed 111 NPC1 patients for two MGAT5 SNPs associated with multiple sclerosis; however, we did not identify an association with NPC1 phenotypic severity.

Tumor cell E-selectin ligands determine partialefficacy of bortezomib on spontaneous lung metastasis formation of solid human tumors in vivo

Extravasation of circulating tumor cells (CTCs) is critical for metastasis and is initiated by adhesive interactions between glycoligands on CTCs and E-selectin on endothelia. Here, we show that the clinically approved proteasome inhibitor bortezomib (BZM; Velcade) counteracts the cytokine-dependent induction of E-selectin in the lung mediated by the primary tumor, thereby impairing endothelial adhesion and thus spontaneous lung metastasis in vivo. However, the efficacy of BZM crucially depends on the tumor cells' E-selectin ligands, which determine distinct adhesion patterns. The canonical ligands sialyl-Lewis A (sLeA) and sLeX mediate particularly high-affinity E-selectin binding so that the incomplete E-selectin-reducing effect of BZM is not sufficient to disrupt adhesion or metastasis. In contrast, tumor cells lacking sLeA/X nevertheless bind E-selectin, but with low affinity, so that adhesion and lung metastasis are significantly diminished. Such low-affinity E-selectin ligands apparently consist of sialylated MGAT5 products on CD44. BZM no longer has anti-metastatic activity after CD44 knockdown in sLeA/X-negative tumor cells or E-selectin knockout in mice. sLeA/X can be determined by immunohistochemistry in cancer samples, which might aid patient stratification. These data suggest that BZM might act as a drug for inhibiting extravasation and thus distant metastasis formation in malignancies expressing low-affinity E-selectin ligands.

IGF2BP1 Promotes the Liver Cancer Stem Cell Phenotype by Regulating MGAT5 mRNA Stability by m6A RNA Methylation

The aim of this study was to elucidate the mechanism of action of the insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1) on the phenotype of the liver cancer stem cells (LCSCs). To gain insight into the mechanism of action of the IGF2BP1 on LCSCs, the IGF2BP1 shRNA sequences were transfected into hepatocellular carcinoma (HCC) cells. The LCSC phenotypes were measured by stemness gene expressions, spheroid formations, percentages of the CD133⁺ cells, colony formations, and tumorigenesis in vivo. Next, we screened for possible molecular mechanisms from the Cancer Genome Atlas (TCGA) database, and a methylated RNA immunoprecipitation-quantitative polymerase chain reaction (MeRIP-qPCR) was used to adjust the binding of IGF2BP1 to the target gene, alpha-1,6-mannosylglycoprotein 6-beta-N-acetylglucosaminyltransferase (MGAT5). The MeRIP-qPCR was used to detect the binding of IGF2BP1 and MGAT5 through N⁶ methyladenosine (m6A) modification. Furthermore, we adjusted the attenuation of the mRNA of the MGAT5 using quantitative real-time PCR (qRT-PCR). The IGF2BP1 was upregulated in the LCSCs. Furthermore, the IGF2BP1 promoted self-renewal and chemoresistance in human LCSCs and tumorigenesis in mice and it enhanced the expression of stemness genes in the LCSCs compared with the HCC cells. Further exploration indicated that the IGF2BP1 binds directly to the MGAT5 and inhibits its mRNA attenuation, suggesting that the IGF2BP1 impacts MGAT5 mRNA stability through m6A modification. Thus, it can be concluded that the IGF2BP1 facilitated the LCSC phenotypes by promoting the MGAT5 mRNA stability through the upregulation of m6A modification of the MGAT5 mRNA.

The polymorphisms of FGFR2 and MGAT5 affect the susceptibility to COPD in the Chinese people

Background

Chronic obstructive pulmonary disease (COPD) is characterized by incomplete reversible airflow limitation and chronic inflammatory response lesions. This study mainly explored whether FGFR2 and MGAT5 polymorphisms affected the risk of COPD in the Chinese people.

Methods

Five variants in FGFR2 and MGAT5 were chosen and genotyped using Agena MassARRAY platform from 315 COPD patients and 314 healthy controls. The correlation of FGFR2 and MGAT5 with COPD susceptibility was evaluated with odds ratio (OR) and 95% confidence interval (CI) via logistic regression.

Results

We found rs2420915 enhanced the risk of COPD, while rs6430491, rs2593704 reduced the susceptibility of COPD (p < 0.05). Rs2420915 could promote the incidence of COPD in the elderly and nonsmokers. Rs1907240 and rs2257129 also increased the susceptibility to COPD in nonsmokers (p < 0.05). MGAT5-rs2593704 played a protective role in COPD development in different subgroups (age ≤ 70, male, smokers, and individuals with BMI ≤ 24 kg/m²). Meanwhile, rs6430491 was linked with a lower risk of COPD in nonsmoking and BMI ≤ 24 kg/m² subgroups.

Conclusions

We concluded that FGFR2 and MGAT5 genetic polymorphisms are correlated with the risk of COPD in the Chinese people. These data underscored the important role of FGFR2 and MGAT5 gene in the occurrence of COPD and provided new biomarkers for COPD treatment.

Trial registration: NA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01498-3.

miR-124-3p Regulates FGF2-EGFR Pathway to Overcome Pemetrexed Resistance in Lung Adenocarcinoma Cells by Targeting MGAT5

Objective

To investigate whether miR-124-3p regulates the fibroblast growth factor 2 (FGF2)–epidermal growth factor receptor (EGFR) pathway by targeting MGAT5 to affect the pemetrexed resistance in lung adenocarcinoma cells.

Methods

PC9-MTA and H1993-MTA anti-pemetrexed lung adenocarcinoma cell lines were constructed. The cell viability of anti-pemetrexed and parent lung adenocarcinoma cells was analyzed using MTS assay and reverse transcription PCR to determine the expression of miR-124-3p. CCK8 assay, colony formation assay, and flow cytometry were used to determine cells’ proliferation and apoptosis. FGF2–EGFR signaling pathway-related proteins and MGAT5 protein expression were quantified by Western blotting. The target relationship between miR-124-3p and MGAT5 was verified by double luciferase assay. A nude mouse model with a transplanted tumor was established using the anti-pemetrexed lung adenocarcinoma cells. Tumor volume and weight were determined, and the apoptosis of tumor cells was observed.

Results

The half-maximal inhibitory concentration of pemetrexed in anti-pemetrexed lung adenocarcinoma cells was higher than that in parent lung adenocarcinoma cells, and the expression of miR-124-3p in the anti-pemetrexed cells was lower than that of the parent cells. In the miR-124-3p overexpression group, MGAT5 silencing group, and miR-124-3p+MGAT5 overexpression group, compared with the control group, the proliferation ability of cells and tumors was markedly reduced; their apoptosis rates were increased significantly; expression levels of FGF2 and p-EGFR/EGFR were decreased; and the growth rate and tumor volume and mass were reduced; however, the opposite results were obtained in the miR-124-3p silencing group (p<0.05).

Conclusion

miR-124-3p may inhibit the FGF2–EGFR pathway by targeting MGAT5 to decrease pemetrexed resistance in lung adenocarcinoma cells.

Recombinant Lectin from Tepary Bean (Phaseolus acutifolius) with Specific Recognition for Cancer-Associated Glycans: Production, Structural Characterization, and Target Identification

Herein, we report the production of a recombinant Tepary bean lectin (rTBL-1), its three-dimensional (3D) structure, and its differential recognition for cancer-type glycoconjugates. rTBL-1 was expressed in Pichia pastoris, yielding 316 mg per liter of culture, and was purified by nickel affinity chromatography. Characterization of the protein showed that rTBL-1 is a stable 120 kDa homo-tetramer folded as a canonical leguminous lectin with two divalent cations (Ca2+ and Mn2+) attached to each subunit, confirmed in its 3D structure solved by X-ray diffraction at 1.9 Å resolution. Monomers also presented a ~2.5 kDa N-linked glycan located on the opposite face of the binding pocket. It does not participate in carbohydrate recognition but contributes to the stabilization of the interfaces between protomers. Screening for potential rTBL-1 targets by glycan array identified 14 positive binders, all of which correspond to β1-6 branched N-glycans' characteristics of cancer cells. The presence of α1-6 core fucose, also tumor-associated, improved carbohydrate recognition. rTBL-1 affinity for a broad spectrum of mono- and disaccharides was evaluated by isothermal titration calorimetry (ITC); however, no interaction was detected, corroborating that carbohydrate recognition is highly specific and requires larger ligands for binding. This would explain the differential recognition between healthy and cancer cells by Tepary bean lectins.

Exploration of susceptible genes associated with Henoch-Schönlein purpura by whole exome sequencing

BACKGROUND

Henoch-Schönlein purpura (HSP) is a systemic small-vessel vasculitis caused by environmental and inherent factors. Although recent research has advanced our understanding of the role of genetic susceptibility in HSP, there are still significant gaps in our knowledge.

OBJECTIVES

In this study, we aimed to explore some susceptibility genes likely associated with HSP.

MATERIAL AND METHODS

Three DNA samples from a family with HSP were used to perform whole exome sequencing with Illumina Hiseq 2500 high-throughput sequencing. The relevant single nucleotide variants (SNVs) were screened according to specific filter conditions and the screened SNVs were then verified with Sanger sequencing. The Sanger sequencing results were further screened according to available literature. Finally, candidate genes were validated in 92 samples from children with HSP, and also in 1 child with HSP from HSP family, using the polymerase chain reaction technique (PCR).

RESULTS

Our analysis revealed that the MIF gene and the MGAT5 gene related to immunity remained after screening. Among the 93 children with HSP, there were 3 patients with MIF mutations and 2 patients with MGAT5 mutations.

CONCLUSIONS

Our findings are helpful for providing new methods and ideas for understanding the pathogenesis of HSP by detecting and analyzing gene mutations at the whole-exome level including multi-generation sequencing. MIF and MGAT5 may be new susceptibility loci for HSP, but their roles in the pathogenesis of HSP are worthy of further study.

Decreased miR-124-3p promoted breast cancer proliferation and metastasis by targeting MGAT5

Non-coding RNAs (ncRNAs) have been shown to regulate gene expression involved in tumor progression of multiple malignancies. Numerous studies have indicated that N-acetylglucosaminyltransferase V (MGAT5), is an important tumorigenesis and metastasis-associated enzyme in breast cancer (BC). But, the underlying molecular mechanisms by which ncRNAs modulate MGAT5 expression in BC remain undetermined. In this study, we demonstrated that miR-124 expression at a low level in BC tissue was associated with poor prognosis of BC patients. Meanwhile, miR-124 reduced BC cell proliferation and metastasis. MGAT5 was confirmed as a direct target of miR-124. MGAT5 restoration attenuated the inhibitory effects of miR-124 on BC proliferation and metastasis in vitro and vivo. Overall, we provide new insight into the mechanisms by which miR-124 inhibits BC progression, suggesting the potential of miR-124 and MGAT5 as biomarkers for early diagnosis of breast cancer to provide innovative ideas and methods for the diagnosis and treatment of BC.

Lectin from Sambucus sieboldiana abrogates the anoikis resistance of colon cancer cells conferred by N-acetylglucosaminyltransferase V during hematogenous metastasis

Anoikis is a form of anchorage-dependent apoptosis, and cancer cells adopt anokis-resistance molecular machinery to conduct metastasis. Here, we report that N-acetylglucosaminyltransferase V gene expression confers anoikis resistance during cancer progression. Overexpression of N-acetylglucosaminyltransferase V protected detached cancer cells from apoptotic death, and suppression or knockout of the gene sensitized cancer cells to the apoptotic death. The gene expression also stimulated anchorage-dependent as well as anchorage-independent colony formation of cancer cells following anoikis stress treatments. Importantly, treatment with the lectin from Sambucus sieboldiana significantly sensitized anoikis-induced cancer cell deaths in vitro as well as in vivo. We propose that the lectin alone or an engineered form could offer a new therapeutic treatment option for cancer patients with advanced tumors.

MicroRNA-424 Predicts a Role for β-1,4 Branched Glycosylation in Cell Cycle Progression

MicroRNA regulation of protein expression plays an important role in mediating many cellular processes, from cell proliferation to cell death. The human microRNA miR-424 is up-regulated in response to anti-proliferative cytokines, such as transforming growth factor β (TGFβ), and directly represses cell cycle progression. Our laboratory recently established that microRNA can be used as a proxy to identify biological roles of glycosylation enzymes (glycogenes). Herein we identify MGAT4A, OGT, and GALNT13 as targets of miR-424. We demonstrate that MGAT4A, an N-acetylglucosaminyltransferase that installs the β-1,4 branch of N-glycans, is directly regulated by miR-424 in multiple mammary epithelial cell lines and observe the loss of MGAT4A in response to TGFβ, an inducer of miR-424. Knockdown of MGAT4A induces cell cycle arrest through decreasing CCND1 levels. MGAT4A does not affect levels of β-1,6 branched N-glycans, arguing that this effect is specific to β-1,4 branching and not due to gross changes in overall N-linked glycosylation. This work provides insight into the regulation of cell cycle progression by specific N-glycan branching patterns.