[Show abstract][Hide abstract] ABSTRACT: E-cadherin is a central molecule in the process of gastric carcinogenesis and its posttranslational modifications by N-glycosylation have been described to induce a deleterious effect on cell adhesion associated with tumor cell invasion. However, the role that site-specific glycosylation of E-cadherin has in its defective function in gastric cancer cells needs to be determined. Using transgenic mice models and human clinical samples, we demonstrated that N-acetylglucosaminyltransferase V (GnT-V)-mediated glycosylation causes an abnormal pattern of E-cadherin expression in the gastric mucosa. In vitro models further indicated that, among the four potential N-glycosylation sites of E-cadherin, Asn-554 is the key site that is selectively modified with β1,6 GlcNAc-branched N-glycans catalyzed by GnT-V. This aberrant glycan modification on this specific asparagine site of E-cadherin was demonstrated to affect its critical functions in gastric cancer cells by affecting E-cadherin cellular localization, cis-dimer formation, molecular assembly and stability of the adherens junctions and cell-cell aggregation, which was further observed in human gastric carcinomas. Interestingly, manipulating this site-specific glycosylation, by preventing Asn-554 from receiving the deleterious branched structures, either by a mutation or by silencing GnT-V, resulted in a protective effect on E-cadherin, precluding its functional dysregulation and contributing to tumor suppression.Oncogene advance online publication, 20 July 2015; doi:10.1038/onc.2015.225.
[Show abstract][Hide abstract] ABSTRACT: Biological significance:
It has been proposed that serum SP-D concentrations are predictive of COPD pathogenesis, but distinguishing between COPD patients and healthy individuals to establish a clear cut-off value is difficult because smoking status highly affects circulating SP-D levels. Herein, we focused on N-glycosylation in SP-D and examined whether or not N-glycosylation patterns in SP-D are associated with the pathogenesis of COPD. We performed an N-glycomic analysis of human serum SP-D and the results show that a core-fucose is present in its N-glycan. We also found that the N-glycosylation in serum SP-D was indeed altered in COPD, that is, fucosylation levels including core-fucosylation are significantly increased in COPD patients compared with non-COPD smokers. The severity of emphysema was positively associated with fucosylation levels in serum SP-D in smokers. Our findings shed new light on the discovery and/or development of a useful biomarker based on glycosylation changes for diagnosing COPD.
Journal of proteomics 07/2015; DOI:10.1016/j.jprot.2015.07.011 · 3.89 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases that degrade many extracellular matrix components and that have been implicated in the pathogenesis of various human diseases including cancer metastasis. Here, we screened MMP-9 inhibitors using photo-cross-linked chemical arrays, which can detect small-molecule ligand-protein interactions on a chip in a high-throughput manner. The array slides were probed sequentially with His-MMP-9, anti-His antibody, and a Cy5-labeled secondary antibody and then scanned with a microarray scanner. We obtained 27 hits among 24,275 compounds from the NPDepo library; 2 of the identified compounds (isoxazole compound 1 and naphthofluorescein) inhibited MMP-9 enzyme activity in vitro. We further explored 17 analogs of 1 and found that compound 18 had the strongest inhibitory activity. Compound 18 also inhibited other MMPs, including MMP-2, MMP-12, and MMP-13 and significantly inhibited cell migration in human fibrosarcoma HT1080 cells. These results suggest that 18 is a broad-spectrum MMP inhibitor.
[Show abstract][Hide abstract] ABSTRACT: While many examples have been reported that glycoclusters interact with target lectins more strongly than single molecules of glycans, through multivalency effects, literature examples to support lectin interactions/modulations on cell surface and in live animals is quite rare. Our N-glycoclusters, which were efficiently prepared by immobilizing 16 molecules of the asparagine-linked glycans (N-glycans) onto a lysine-based dendron template through histidine-mediated Huisgen cycloaddition, were shown to efficiently detect platelet endothelial cell adhesion molecule (PECAM) on human umbilical vein endothelial cells (HUVEC) as a α(2-6)-sialylated oligosaccharides recognizing lectin. Furthermore, the identity of the N-glycans on our N-glycoclusters allowed control over organ-selective accumulation and serum clearance properties when intravenously injected into mice.
[Show abstract][Hide abstract] ABSTRACT: O-GlcNAcylation is a reversible post-translational modification. O-GlcNAc addition and removal is catalyzed by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), respectively. More recent evidence indicates that regulation of O-GlcNAcylation is important for inflammatory diseases and tumorigenesis. In this study, we revealed that O-GlcNAcylation was increased in the colonic tissues of dextran sodium sulfate (DSS)-induced colitis and azoxymethane (AOM)/DSS-induced colitis-associated cancer (CAC) animal models. Moreover, the O-GlcNAcylation level was elevated in human CAC tissues compared with matched normal counterparts. To investigate the functional role of O-GlcNAcylation in colitis, we used OGA heterozygote mice, which have an increased level of O-GlcNAcylation. OGA+/- mice have higher susceptibility to DSS-induced colitis than OGA+/+ mice. OGA +/- mice exhibited a higher incidence of colon tumors than OGA+/+ mice. In molecular studies, elevated O-GlcNAc levels were shown to enhance the activation of NF-κB signaling through increasing the binding of RelA/p65 to its target promoters. We also found that Thr-322 and Thr352 in the p65-O-GlcNAcylation sites are critical for p65 promoter binding. These results suggest that the elevated O-GlcNAcylation level in colonic tissues contributes to the development of colitis and CAC by disrupting regulation of NF-κB-dependent transcriptional activity.
[Show abstract][Hide abstract] ABSTRACT: Core fucosylation is an important post-translational modification, which is catalyzed by α1,6-fucosyltransferase (Fut8). Increased expression of Fut8 has been shown in diverse carcinomas including hepatocarcinoma. In this study, we investigated the role of Fut8 expression in liver regeneration by using the 70% partial hepatectomy (PH) model, and found that Fut8 is also critical for the regeneration of liver. Interestingly, we show that the Fut8 activities were significantly increased in the beginning of PH (~4d), but returned to the basal level in the late stage of PH. Lacking Fut8 led to delayed liver recovery in mice. This retardation mainly resulted from suppressed hepatocyte proliferation, as supported not only by a decreased phosphorylation level of epidermal growth factor (EGF) receptor and hepatocyte growth factor (HGF) receptor in the liver of Fut8(-/-) mice in vivo, but by the reduced response to exogenous EGF and HGF of the primary hepatocytes isolated from the Fut8(-/-) mice. Furthermore, an administration of L-fucose, which can increase GDP-fucose synthesis through a salvage pathway, significantly rescued the delayed liver regeneration of Fut8(+/-) mice. Overall, our study provides the first direct evidence for the involvement of Fut8 in liver regeneration.
[Show abstract][Hide abstract] ABSTRACT: Unlabelled:
Objecitive: Fucosyltransferase 8 (FUT8), the only enzyme responsible for the core α1,6-fucosylation of asparagine-linked oligosaccharides of glycoproteins, is a vital enzyme in cancer development and progression. We examined FUT8 expression in non-small cell lung cancers (NSCLCs) to analyze its clinical significance. We also examined the expression of guanosine diphosphate-mannose-4,6-dehydratase (GMD), which is imperative for the synthesis of fucosylated oligosaccharides.
Using immunohistochemistry, we evaluated the expression of FUT8 and GMD in relation to patient survival and prognosis in potentially curatively resected NSCLCs.
High expression of FUT8 was found in 67 of 129 NSCLCs (51.9%) and was significantly found in non-squamous cell carcinomas (p = 0.008). High expression of FUT8 was associated with poor survival (p = 0.03) and was also a significant and independent unfavorable prognostic factor in patients with potentially curatively resected NSCLCs (p = 0.047). High expression of GMD was significantly associated with high FUT8 expression (p = 0.04).
High expression of FUT8 is associated with an unfavorable clinical outcome in patients with potentially curatively resected NSCLCs, suggesting that FUT8 can be a prognostic factor. The analysis of FUT8 expression and its core fucosylated products may provide new insights for the therapeutic targets of NSCLCs.
[Show abstract][Hide abstract] ABSTRACT: Cellular glycosylation plays an important role in many biological processes, as well as in disease states such as diabetes and cancer. Nucleotide sugar s are donor substrates of glycosyltransferases and their availability and localization regulate glycosylation status. The nucleotide sugar level is controlled by cellular metabolic states. To investigate the fate of nucleotide sugars in glycosylation, two methods for monitoring nucleotide sugar metabolism, namely, ion-pair reversed-phase HPLC and LC-MS, have been previously described (Nakajima et al., Glycobiology 20(7):865–871, 2010; Mol Cell Proteomics (9):2468–2480, 2013). Using the HPLC method, cellular levels of eight unique nucleotide sugars were simultaneously determined. Using the LC-MS method, which is based on mass isotopomer analysis of nucleotide sugars metabolically labeled with 13C6-glucose, the metabolic pathways governing UDP-GlcNAc synthesis and utilization were characterized. Here, these strategies are reviewed and the biochemical significance of nucleotide sugars in cellular glycosylation is discussed.
Glycoscience: Biology and Medicine, 01/2015: pages 103-110; , ISBN: 978-4-431-54840-9
[Show abstract][Hide abstract] ABSTRACT: This overview summarizes the current status and future perspectives in the field of glycoscience, with the focus on the integration of current knowledge obtained from genome and proteome research and the impact of such findings on human health and disease. The pathophysiological significance of glycan changes has been reported, and most of these findings can be found in the many chapters in this book. The roles of glycans in infectious diseases, differentiation and development, immune responses, cancer progression, neural communication, and many other intercellular recognition processes are the major topics in this book. Biomarker discovery and its validation of various diseases including cancer are a new challenge in this field. Therapeutics such as vaccines using glycan mimics, recombinant glycoproteins, or the modification of glycans are also new perspective for various diseases. In order to address these challenges, the chemo-enzymatic synthesis of glycans and more sensitive methods for glycan analysis by using NMR, mass spectrometry, imaging techniques, and bioinformatics are needed for the advancement of glycoscience. Finally, major future challenges of glycoscience are also listed in this overview.
Glycoscience: Biology and Medicine, 01/2015: pages 11-14; , ISBN: 978-4-431-54840-9
[Show abstract][Hide abstract] ABSTRACT: Nutrient transporters are critical gate-keepers of extracellular metabolite entry into the cell. As integral membrane proteins, most transporters are N-glycosylated, and the N-glycans are remodeled in the Golgi apparatus. The Golgi branching enzymes N-acetylglucosaminyltransferases I, II, IV, V and avian VI (encoded by Mgat1, Mgat2, Mgat4a/b/c Mgat5 and Mgat6), each catalyze the addition of acetylglucosamine (GlcNAc) in N-glycans. Here, we asked whether N-glycan branching promotes nutrient transport and metabolism in immortal human HeLa carcinoma and non-malignant HEK293 embryonic kidney cells. Mgat6 is absent in mammals, but ectopic expression can be expected to add an additional β1,4-linked branch to N-glycans, and may provide evidence for functional redundancy of the N-glycan branches. Tetracycline (tet)-induced overexpression of Mgat1, Mgat5 and Mgat6 resulted in increased enzyme activity and increased N-glycan branching concordant with the known specificities of these enzymes. Tet-induced Mgat1, Mgat5 and Mgat6 combined with stimulation of hexosamine biosynthesis pathway (HBP) to UDP-GlcNAc, increased cellular metabolite levels, lactate and oxidative metabolism in an additive manner. We then tested the hypothesis that N-glycan branching alone might promote nutrient uptake when glucose (Glc) and glutamine are limiting. In low glutamine and Glc medium, tet-induced Mgat5 alone increased amino acids uptake, intracellular levels of glycolytic and TCA intermediates, as well as HEK293 cell growth. More specifically, tet-induced Mgat5 and HBP elevated the import rate of glutamine, although transport of other metabolites may be regulated in parallel. Our results suggest that N-glycan branching cooperates with HBP to regulate metabolite import in a cell autonomous manner, and can enhance cell growth in low-nutrient environments.
[Show abstract][Hide abstract] ABSTRACT: The vascular endothelial glycocalyx contains several anionic sugars, one of which is a sialic acid attached to both N- and O-glycans. Platelet endothelial cell adhesion molecule (PECAM), a member of the Ig superfamily that plays multiple roles in
cell adhesion, mechanical stress sensing, antiapoptosis and angiogenesis, has recently been shown to recognize α2,6-sialic
acid. In endothelial cells that lack α2,6-sialic acid because of sialyltransferase ST6Gal I deficiency, impairment of the
homophilic PECAM interaction and PECAM-dependent cell survival signaling is observed. In this review, we will introduce part
of the biological role of PECAM, and discuss how the lectin activity of PECAM is related to angiogenesis.
[Show abstract][Hide abstract] ABSTRACT: N-Acetylglucosaminyltransferase (GnT) III is a glycosyltransferase which produces bisected N-glycans by transferring GlcNAc to the 4-position of core mannose. Bisected N-glycans are involved in physiological and pathological processes through the functional regulation of their carrier proteins. An understanding of the biological functions of bisected glycans will be greatly accelerated by use of specific inhibitors of GnT-III. Thus far, however, such inhibitors have not been developed and even the substrate-binding mode of GnT-III is not fully understood. To gain insight into structural features required of the substrate, we systematically synthesized four N-glycan units, the branching parts of the bisected and non-bisected N-glycans. The series of syntheses were achieved from a common core trimannose, giving bisected tetra- and hexasaccharides as well as non-bisected tri- and pentasaccharides. A competitive GnT-III inhibition assay using the synthetic substrates revealed a vital role for the Manβ(1-4)GlcNAc moiety. In keeping with previous reports, GlcNAc at the α1,3-branch is also involved in the interaction. The structural requirements of GnT-III elucidated in this study will provide a basis for rational inhibitor design.
[Show abstract][Hide abstract] ABSTRACT: In the nervous system, various unique glycans not found in other tissues are expressed on glycoproteins, and their expression/functions have been studied using specific antibodies/lectins. Among brain-specific glycans in mammals, we focus on human natural killer-1 (HNK-1) and related Cat-315 epitopes, which can be detected using specific antibodies. It is known that the HNK-1 epitope is expressed on N- and O-mannosylated glycans and that Cat-315 mAb preferentially recognizes the HNK-1 epitope on brain-specific "branched O-mannose glycan." The β1,6-branched O-mannose structure is synthesized by a brain-specific glycosyltransferase, N-acetylglucosaminyltransferase-IX (GnT-IX, also designated as GnT-Vb). Using GnT-IX gene-deficient mice and specific antibodies/lectins, the function of GnT-IX was found to be quite different from that of its ubiquitous homologue, GnT-V. Using Cat-315 mAb, the receptor protein tyrosine phosphatase-beta (RPTPβ) was identified as an in vivo target glycoprotein for GnT-IX. Analysis of the function of branched O-mannose glycan on RPTPβ indicated that its loss promoted the recovery process after myelin injury (called remyelination) in brain and that this phenomenon is probably caused in vivo by reduced activation of astrocytes in GnT-IX-deficient brain.
Advances in neurobiology 08/2014; 9:117-127. DOI:10.1007/978-1-4939-1154-7_6
[Show abstract][Hide abstract] ABSTRACT: The luminal sides of vascular endothelial cells are heavily covered with a so-called glycocalyx, but the precise role of the
endothelial glycocalyx remains unclear. Our previous study showed that N-glycan α2,6-sialylation regulates the cell surface residency of an anti-apoptotic molecule, platelet endothelial cell adhesion
molecule (PECAM), as well as the sensitivity of endothelial cells toward apoptotic stimuli. As PECAM itself was shown to be
modified with biantennary N-glycans having α2,6-sialic acid, we expected that PECAM would possess lectin-like activity toward α2,6-sialic acid to ensure
its homophilic interaction. To verify this, a series of oligosaccharides were initially added to observe their inhibitory
effects on the homophilic PECAM interaction in vitro. We found that a longer α2,6-sialylated oligosaccharide exhibited strong inhibitory activity. Furthermore, we found that
a cluster-type α2,6-sialyl N-glycan probe specifically bound to PECAM-immobilized beads. Moreover, the addition of the α2,6-sialylated oligosaccharide
to endothelial cells enhanced the internalization of PECAM as well as the sensitivity to apoptotic stimuli. Collectively,
these findings suggest that PECAM is a sialic acid binding lectin and that this binding property supports endothelial cell
survival. Notably, our findings that α2,6-sialylated glycans influenced the susceptibility to endothelial cell apoptosis shed
light on the possibility of using a glycan-based method to modulate angiogenesis.