Identification of stemness-related glycosylation changes in head and neck squamous cell carcinoma.

BACKGROUND: Altered glycosylation is a hallmark of cancer associated with therapy resistance and tumor behavior. In this study, we investigated the glycosylation profile of stemness-related proteins OCT4, CIP2A, MET, and LIMA1 in HNSCC tumors. METHODS: Tumor, adjacent normal tissue, and blood samples of 25 patients were collected together with clinical details. After tissue processing, lectin-based glycovariant screens were performed. RESULTS: Strong correlation between glycosylation profiles of all four stemness-related proteins was observed in tumor tissue, whereas glycosylation in tumor tissue, adjacent normal tissue, and serum was differential. CONCLUSIONS: A mannose- and galactose-rich glycosylation niche associated with stemness-related proteins was identified.

The transcription factor HMGB2 indirectly regulates APRIL expression and Gd-IgA1 production in patients with IgA nephropathy.

BACKGROUND: IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. Proliferation-inducing ligand (APRIL) was identified as an important cause of glycosylation deficiency of IgA1 (Gd-IgA1), which can 'trigger' IgAN. Our previous study indicated that high migration group protein B2 (HMGB2) in peripheral blood mononuclear cells from patients with IgAN was associated with disease severity, but the underlying mechanism remains unclear. MATERIALS AND METHODS: The location of HMGB2 was identified by immunofluorescence. qRT-PCR and Western blotting were used to measure HMGB2, HMGA1, and APRIL expression. Gd-IgA1 levels were detected by enzyme-linked immunosorbent assay (ELISA). In addition, we used DNA pull-down, protein profiling, and transcription factor prediction software to identify proteins bound to the promoter region of the APRIL gene. RNA interference and coimmunoprecipitation (Co-IP) were used to verify the relationships among HMGB2, high mobility group AT-hook protein 1 (HMGA1), and APRIL. RESULTS: HMGB2 expression was greater in IgAN patients than in HCs and was positively associated with APRIL expression in B cells. DNA pull-down and protein profiling revealed that HMGB2 and HMGA1 bound to the promoter region of the APRIL gene. The expression levels of HMGA1, APRIL, and Gd-IgA1 were downregulated after HMGB2 knockdown. Co-IP indicated that HMGB2 binds to HMGA1. The Gd-IgA1 concentration in the supernatant was reduced after HMGA1 knockdown. HMGA1 binding sites were predicted in the promoter region of the APRIL gene. CONCLUSION: HMGB2 expression is greater in IgAN patients than in healthy controls; it promotes APRIL expression by interacting with HMGA1, thereby inducing Gd-IgA1 overexpression and leading to IgAN.

The effects of immortalization on the N-glycome and proteome of CDK4-transformed lung cancer cells.

Biological experiments are often conducted in vitro using immortalized cells due to their accessibility and ease of propagation compared to primary cells and live animals. However, immortalized cells may present different proteomic and glycoproteomic characteristics from the primary cell source due to the introduction of genes that enhance proliferation (e.g. CDK4) or enable telomere lengthening. To demonstrate the changes in phenotype upon CDK4-transformation, we performed LC-MS/MS glycomic and proteomic characterizations of a human lung cancer primary cell line (DTW75) and a CDK4-transformed cell line (GL01) derived from DTW75. We observed that the primary and CDK4-transformed cells expressed significantly different levels of sialylated, fucosylated, and sialofucosylated N-glycans. Specifically, the primary cells expressed higher levels of hybrid- and complex-type sialylated N-glycans, while CDK4-transformed cells expressed higher levels of complex-type fucosylated and sialofucosylated N-glycans. Further, we compared the proteomic differences between the cell lines and found that CDK4-transformed cells expressed higher levels of RNA-binding and adhesion proteins. Further, we observed that the CDK4-transformed cells changed N-glycosylation after 31 days in cell culture, with a decrease in high-mannose and increase in fucosylated, sialylated, and sialofucosylated N-glycans. Identifying these changes between primary and CDK4-transformed cells will provide useful insight when adapting cell lines that more closely resemble in vivo physiological conditions.

N-glycoproteomic analyses of human intestinal enteroids, varying in histo-blood group geno- and phenotypes, reveal a wide repertoire of fucosylated glycoproteins.

Human noroviruses, globally the main cause of viral gastroenteritis, show strain specific affinity for histo-blood group antigens (HBGA) and can successfully be propagated ex vivo in human intestinal enteroids (HIEs). HIEs established from jejunal stem cells of individuals with different ABO, Lewis and secretor geno- and phenotypes, show varying susceptibility to such infections. Using bottom-up glycoproteomic approaches we have defined and compared the N-linked glycans of glycoproteins of seven jejunal HIEs. Membrane proteins were extracted, trypsin digested, and glycopeptides enriched by hydrophilic interaction liquid chromatography and analyzed by nanoLC-MS/MS. The Byonic software was used for glycopeptide identification followed by hands-on verifications and interpretations. Glycan structures and attachment sites were identified from MS2 spectra obtained by higher-energy collision dissociation through analysis of diagnostic saccharide oxonium ions (B-ions), stepwise glycosidic fragmentation of the glycans (Y-ions), and peptide sequence ions (b- and y-ions). Altogether 694 unique glycopeptides from 93 glycoproteins were identified. The N-glycans encompassed pauci- and oligomannose, hybrid- and complex-type structures. Notably, polyfucosylated HBGA-containing glycopeptides of the four glycoproteins tetraspanin-8, carcinoembryonic antigen-related cell adhesion molecule 5, sucrose-isomaltase and aminopeptidase N were especially prominent and were characterized in detail and related to donor ABO, Lewis and secretor types of each HIE. Virtually no sialylated N-glycans were identified for these glycoproteins suggesting that terminal sialylation was infrequent compared to fucosylation and HBGA biosynthesis. This approach gives unique site-specific information on the structural complexity of N-linked glycans of glycoproteins of human HIEs and provides a platform for future studies on the role of host glycoproteins in gastrointestinal infectious diseases.

Chemical Synthesis of Fucosylated Chondroitin Sulfate Tetrasaccharide with Fucosyl Branch at the 6-OH of GalNAc Residue.

Fucosylated chondroitin sulfate is a unique glycosaminoglycan isolated from sea cucumbers, with excellent anticoagulant activity. The fucosyl branch in FCS is generally located at the 3-OH of D-glucuronic acid but, recently, a novel structure with α-L-fucose linked to the 6-OH of N-acetyl-galactosamine has been found. Here, using functionalized monosaccharide building blocks, we prepared novel FCS tetrasaccharides with fucosyl branches both at the 6-OH of GalNAc and 3-OH of GlcA. In the synthesis, the protective group strategy of selective O-sulfation, as well as stereoselective glycosylation, was established, which enabled the efficient synthesis of the specific tetrasaccharide compounds. This research enriches knowledge on the structural types of FCS oligosaccharides and facilitates the exploration of the structure-activity relationship in the future.

Neurodevelopmental defects in a mouse model of O-GlcNAc transferase intellectual disability.

The addition of O-linked ß-N-acetylglucosamine (O-GlcNAc) to proteins (referred to as O-GlcNAcylation) is a modification that is crucial for vertebrate development. O-GlcNAcylation is catalyzed by O-GlcNAc transferase (OGT) and reversed by O-GlcNAcase (OGA). Missense variants of OGT have recently been shown to segregate with an X-linked syndromic form of intellectual disability, OGT-linked congenital disorder of glycosylation (OGT-CDG). Although the existence of OGT-CDG suggests that O-GlcNAcylation is crucial for neurodevelopment and/or cognitive function, the underlying pathophysiologic mechanisms remain unknown. Here we report a mouse line that carries a catalytically impaired OGT-CDG variant. These mice show altered O-GlcNAc homeostasis with decreased global O-GlcNAcylation and reduced levels of OGT and OGA in the brain. Phenotypic characterization of the mice revealed lower body weight associated with reduced body fat mass, short stature and microcephaly. This mouse model will serve as an important tool to study genotype-phenotype correlations in OGT-CDG in vivo and for the development of possible treatment avenues for this disorder.

Breast cancer therapy: from the perspective of glucose metabolism and glycosylation.

Breast cancer is a leading cause of mortality and the most prevalent form of malignant tumor among women worldwide. Breast cancer cells exhibit an elevated glycolysis and altered glucose metabolism. Moreover, these cells display abnormal glycosylation patterns, influencing invasion, proliferation, metastasis, and drug resistance. Consequently, targeting glycolysis and mitigating abnormal glycosylation represent key therapeutic strategies for breast cancer. This review underscores the importance of protein glycosylation and glucose metabolism alterations in breast cancer. The current research efforts in developing effective interventions targeting glycolysis and glycosylation are further discussed.

Site-Specific Analysis of Core and Antenna Fucosylation on Serum Glycoproteins.

Fucosylation is an important structural feature of glycans and plays an essential role in the regulation of glycoprotein functions. Fucosylation can be classified into core- (CF) and antenna-fucosylation (AF, also known as (sialyl-) Lewis) based on the location on N-glycans, and they perform distinct biological functions. In this study, core- and antenna-fucosylated N-glycans on human serum glycoproteins that hold great clinical application values were systematically characterized at the site-specific level using StrucGP combined with the recently developed fucosylation assignment method. The results showed that fucosylation was widely distributed on serum glycoproteins, with 50% of fucosylated glycopeptides modified by AF N-glycans, 37% by CF N-glycans, and 13% by dual-fucosylated N-glycans. Interestingly, CF and AF N-glycans preferred to modify different groups of serum glycoproteins with different tissue origins and were involved in distinctive biological processes. Specifically, AF N-glycoproteins are mainly from the liver and participated in complement activation, blood coagulation, and endopeptidase activities, while CF N-glycoproteins originate from diverse tissues and are mainly involved in cell adhesion and signaling transduction. These data further enhanced our understanding of fucosylation on circulation glycoproteins.

In Vitro Characterization of an O-Specific Glycosyltransferase Involved in Flagellin Glycosylation.

Glycosyltransferases play a fundamental role in the biosynthesis of glycoproteins and glycotherapeutics. In this study, we investigated protein glycosyltransferase FlgGT1, belonging to the GT2 family. The GT2 family includes cysteine S-glycosyltransferases involved in antimicrobial peptide biosyntheses, sharing conserved catalytic domains while exhibiting diverse C-terminal domains. Our in vitro studies revealed that FlgGT1 recognizes structural motifs rather than specific amino acid sequences when glycosylating the flagellin protein Hag. Notably, FlgGT1 is selective for serine or threonine O-glycosylation over cysteine S-glycosylation. Molecular dynamics simulations provided insights into the structural basis of FlgGT1's ability to accommodate various sugar nucleotides as donor substrates. Mutagenesis experiments on FlgGT1 demonstrated that truncating the relatively large C-terminal domain resulted in a loss of flagellin glycosylation activity. Our classification based on sequence similarity network analysis and AlphaFold2 structural predictions suggests that the acquisition of the C-terminal domain is a key evolutionary adaptation conferring distinct substrate specificities on glycosyltransferases within the GT2 family.

ELISA-based highly sensitive assay system for the detection of endogenous NGLY1 activity.

Cytosolic peptide:N-glycanase (NGLY1, PNGase) is an enzyme that cleaves N-glycans from misfolded glycoproteins. In 2012, a human genetic disorder, NGLY1 deficiency, was first reported to be caused by mutations of the NGLY1 gene. Since then, there has been rapid progresses on NGLY1 biology, and gene therapy has been proposed as a promising therapeutic option for NGLY1 deficiency. While a plasma/urine biomarker has also been developed for this disease, detection of NGLY1 activity could be another viable option for early diagnosis of NGLY1 deficiency. Thus far, several in vitro and in cellulo NGLY1 assays have been reported, but those assay systems have several issues that must be addressed in order to develop an assay system compatible for routine clinical examination. Here, we show a facile, highly sensitive in vitro assay system that could be used to detect NGLY1 activity by utilizing its sequence editing function, i.e. conversion of glycosylated Asn into Asp, followed by a detection of newly generated epitope (HA)-tag by anti-HA antibody. Using this ELISA-based assay, we detected endogenous NGLY1 activity in as little as 2 µg of crude extract, which is the equivalent of 5 × 103 cells. Our system also detects NGLY1 activity from cells with compromised NGLY1 activity, such as iPS cells from patient samples. This assay system could be applied in future clinical examinations to achieve an early diagnosis of NGLY1 deficiency.

Fucosylation inhibitor 6-alkynylfucose enhances the ATRA-induced differentiation effect on acute promyelocytic leukemia cells.

For acute promyelocytic leukemia (APL), differentiation therapy with all-trans retinoic acid (ATRA) is well established. However, the narrow application and tolerance development of ATRA remain to be improved. In this study, we investigated the effects of combinations of glycosylation inhibitors with ATRA to achieve better efficiency than ATRA alone. We found that the combination of fucosylation inhibitor 6-alkynylfucose (6AF) and ATRA had an additional effect on cell differentiation, as revealed by expression changes in two differentiation markers, CD11b and CD11c, and significant morphological changes in NB4 APL and HL-60 acute myeloid leukemia (AML) cells. In AAL lectin blot analyses, ATRA or 6AF alone could decrease fucosylation, while their combination decreased fucosylation more efficiently. To clarify the molecular mechanism for the 6AF effect on ATRA-induced differentiation, we performed microarray analyses using NB4 cells. In a pathway analysis using DAVID software, we found that the C-type lectin receptor (CLR) signaling pathway was enriched with high significance. In real-time PCR analyses using NB4 and HL-60 cells, FcεRIγ, CLEC6A, CLEC7A, CASP1, IL-1ß, and EGR3, as components of the CLR pathway, as well as CD45 and AKT3 were upregulated by 6AF in ATRA-induced differentiation. Taken together, the present findings suggest that the CLR signaling pathway is involved in the 6AF effect on ATRA-induced differentiation.

Glycan-Imprinted Nanoparticle as Artificial Neutralizing Antibody for Efficient HIV-1 Recognition and Inhibition.

The HIV-1 envelope is a heavily glycosylated class 1 trimeric fusion protein responsible for viral entry into CD4+ immune cells. Developing neutralizing antibodies against the specific envelope glycans is an alternative method for antiviral therapies. This work presents the first-ever development and characterization of artificial neutralizing antibodies using molecular imprinting technology to recognize and bind to the envelope protein of HIV-1. The prepared envelope glycan-imprinted nanoparticles (GINPs) can successfully prevent HIV-1 from infecting target cells by shielding the glycans on the envelope protein. In vitro experiments showed that GINPs have strong affinity toward HIV-1 (Kd = 36.7 ± 2.2 nM) and possess high anti-interference and specificity. GINPs demonstrate broad inhibition activity against both tier 1 and tier 2 HIV-1 strains with a pM-level IC50 and exhibit a significant inhibitory effect on long-term viral replication by more than 95%. The strategy provides a promising method for the inhibition and therapy of HIV-1 infection.

A quest for cytosolic sequons and their functions.

Evolution shapes protein sequences for their functions. Here, we studied the moonlighting functions of the N-linked sequon NXS/T, where X is not P, in human nucleocytosolic proteins. By comparing membrane and secreted proteins in which sequons are well known for N-glycosylation, we discovered that cyto-sequons can participate in nucleic acid binding, particularly in zinc finger proteins. Our global studies further discovered that sequon occurrence is largely proportional to protein length. The contribution of sequons to protein functions, including both N-glycosylation and nucleic acid binding, can be regulated through their density as well as the biased usage between NXS and NXT. In proteins where other PTMs or structural features are rich, such as phosphorylation, transmembrane ɑ-helices, and disulfide bridges, sequon occurrence is scarce. The information acquired here should help understand the relationship between protein sequence and function and assist future protein design and engineering.

Targeting branched N-glycans and fucosylation sensitizes ovarian tumors to immune checkpoint blockade.

Aberrant glycosylation is a crucial strategy employed by cancer cells to evade cellular immunity. However, it's unclear whether homologous recombination (HR) status-dependent glycosylation can be therapeutically explored. Here, we show that the inhibition of branched N-glycans sensitizes HR-proficient, but not HR-deficient, epithelial ovarian cancers (EOCs) to immune checkpoint blockade (ICB). In contrast to fucosylation whose inhibition sensitizes EOCs to anti-PD-L1 immunotherapy regardless of HR-status, we observe an enrichment of branched N-glycans on HR-proficient compared to HR-deficient EOCs. Mechanistically, BRCA1/2 transcriptionally promotes the expression of MGAT5, the enzyme responsible for catalyzing branched N-glycans. The branched N-glycans on HR-proficient tumors augment their resistance to anti-PD-L1 by enhancing its binding with PD-1 on CD8+ T cells. In orthotopic, syngeneic EOC models in female mice, inhibiting branched N-glycans using 2-Deoxy-D-glucose sensitizes HR-proficient, but not HR-deficient EOCs, to anti-PD-L1. These findings indicate branched N-glycans as promising therapeutic targets whose inhibition sensitizes HR-proficient EOCs to ICB by overcoming immune evasion.

The GFPT2-O-GlcNAcylation-YBX1 axis promotes IL-18 secretion to regulate the tumor immune microenvironment in pancreatic cancer.

The immunosuppressive microenvironment caused by several intrinsic and extrinsic mechanism has brought great challenges to the immunotherapy of pancreatic cancer. We identified GFPT2, the key enzyme in hexosamine biosynthesis pathway (HBP), as an immune-related prognostic gene in pancreatic cancer using transcriptome sequencing and further confirmed that GFPT2 promoted macrophage M2 polarization and malignant phenotype of pancreatic cancer. HBP is a glucose metabolism pathway leading to the generation of uridine diphosphate N-acetylglucosamine (UDP-GlcNAc), which is further utilized for protein O-GlcNAcylation. We confirmed GFPT2-mediated O-GlcNAcylation played an important role in regulating immune microenvironment. Through cellular proteomics, we identified IL-18 as a key downstream of GFPT2 in regulating the immune microenvironment. Through CO-IP and protein mass spectrum, we confirmed that YBX1 was O-GlcNAcylated and nuclear translocated by GFPT2-mediated O-GlcNAcylation. Then, YBX1 functioned as a transcription factor to promote IL-18 transcription. Our study elucidated the relationship between the metabolic pathway of HBP in cancer cells and the immune microenvironment, which might provide some insights into the combination therapy of HBP vulnerability and immunotherapy in pancreatic cancer.

Development and validation of a model and nomogram for breast cancer diagnosis based on quantitative analysis of serum disease-specific haptoglobin N-glycosylation.

BACKGROUND: A better diagnostic marker is in need to distinguish breast cancer from suspicious breast lesions. The abnormal glycosylation of haptoglobin has been documented to assist cancer diagnosis. This study aims to evaluate disease-specific haptoglobin (DSHp)-ß N-glycosylation as a potential biomarker for breast cancer diagnosis. METHODS: DSHp-ß chains of 497 patients with suspicious breast lesions who underwent breast surgery were separated from serum immunoinflammatory-related protein complexes. DSHp-ß N-glycosylation was quantified by mass spectrometric analysis. After missing data imputation and propensity score matching, patients were randomly assigned to the training set (n = 269) and validation set (n = 113). Logistic regression analysis was employed in model and nomogram construction. The diagnostic performance was analyzed with receiver operating characteristic and calibration curves. RESULTS: 95 N-glycopeptides at glycosylation sites N207/N211, N241, and N184 were identified in 235 patients with benign breast diseases and 262 patients with breast cancer. DSHp-ß N-tetrafucosyl and hexafucosyl were significantly increased in breast cancer compared with benign diseases (p < 0.001 and p = 0.001, respectively). The new diagnostic model and nomogram included GN2F2, G6N3F6, GN2FS at N184, G-N&G2S2, G2&G3NFS, G2N3F, GN3 at N207/N211, CEA, CA153, and could reliably distinguish breast cancer from benign diseases. For the training set, validation set, and training and validation sets, the area under the curves (AUCs) were 0.80 (95% CI: 0.75-0.86, specificity: 87%, sensitivity: 62%), 0.77 (95% CI:0.69-0.86, specificity: 75%, sensitivity: 69%), and 0.80 (95% CI:0.76-0.84, specificity: 77%, sensitivity: 68%), respectively. CEA, CA153, and their combination yielded AUCs of 0.62 (95% CI: 0.56-0.67, specificity: 29%, sensitivity: 90%), 0.65 (95% CI: 0.60-0.71, specificity: 74%, sensitivity: 51%), and 0.67 (95% CI: 0.62-0.73, specificity: 60%, sensitivity: 68%), respectively. CONCLUSIONS: The combination of DSHp-ß N-glycopeptides, CEA, and CA153 might be a better serologic marker to differentiate between breast cancer and benign breast diseases. The dysregulated N-glycosylation of serum DSHp-ß could provide insights into breast tumorigenesis.

Effect of 1,4-Dioxane Solvent on ß-Glucuronidation Using Methyl 1,2,3,4-Tetra-O-acetyl-ß-D-glucuronate as the Glycosyl Donor.

A facile and selective ß-D-glucuronidation of alcohols, such as (-)-menthol, cholestanol, (+)- and (-)-borneols, and 2-adamantanol, using commercially available methyl 1,2,3,4-tetra-O-acetyl-ß-D-glucuronate as the glycosyl donor and trimethylsilyl bis(trifluoromethanesulfonyl)imide (Tf2NTMS) (0.5 equivalent) as the activator in 1,4-dioxane at 60 °C gave products in moderate yields. The addition of MS4A increased the ß : α ratios of D-glucuronides when cholestanol, (+)-borneol, and 2-adamantanol were used as the acceptor substrate.

Regulation of Glycosylation in Bone Metabolism.

Glycosylation plays a crucial role in the maintenance of homeostasis in the body and at the onset of diseases such as inflammation, neurodegeneration, infection, diabetes, and cancer. It is also involved in bone metabolism. N- and O-glycans have been shown to regulate osteoblast and osteoclast differentiation. We recently demonstrated that ganglio-series and globo-series glycosphingolipids were essential for regulating the proliferation and differentiation of osteoblasts and osteoclasts in glycosyltransferase-knockout mice. Herein, we reviewed the importance of the regulation of bone metabolism by glycoconjugates, such as glycolipids and glycoproteins, including our recent results.

Optimizing cryopreservation conditions for use of fucosylated human mesenchymal stromal cells in anti-inflammatory/immunomodulatory therapeutics.

Mesenchymal stem/stromal cells (MSCs) are being increasingly used in cell-based therapies due to their broad anti-inflammatory and immunomodulatory properties. Intravascularly-administered MSCs do not efficiently migrate to sites of inflammation/immunopathology, but this shortfall has been overcome by cell surface enzymatic fucosylation to engender expression of the potent E-selectin ligand HCELL. In applications of cell-based therapies, cryopreservation enables stability in both storage and transport of the produced cells from the manufacturing facility to the point of care. However, it has been reported that cryopreservation and thawing dampens their immunomodulatory/anti-inflammatory activity even after a reactivation/reconditioning step. To address this issue, we employed a variety of methods to cryopreserve and thaw fucosylated human MSCs derived from either bone marrow or adipose tissue sources. We then evaluated their immunosuppressive properties, cell viability, morphology, proliferation kinetics, immunophenotype, senescence, and osteogenic and adipogenic differentiation. Our studies provide new insights into the immunobiology of cryopreserved and thawed MSCs and offer a readily applicable approach to optimize the use of fucosylated human allogeneic MSCs as immunomodulatory/anti-inflammatory therapeutics.

In-Membrane Enrichment and Peptic Digestion to Facilitate Analysis of Monoclonal Antibody Glycosylation.

The number of therapeutic monoclonal antibodies (mAbs) is growing rapidly due to their widespread use for treating various diseases and health conditions. Assessing the glycosylation profile of mAbs during production is essential to ensuring their safety and efficacy. This research aims to rapidly isolate and digest mAbs for liquid chromatography-tandem mass spectrometry (LC-MS/MS) identification of glycans and monitoring of glycosylation patterns, potentially during manufacturing. Immobilization of an Fc region-specific ligand, oFc20, in a porous membrane enables the enrichment of mAbs from cell culture supernatant and efficient elution with an acidic solution. Subsequent digestion of the mAb eluate occurred in a pepsin-modified membrane within 5 min. The procedure does not require alkylation and desalting, greatly shortening the sample preparation time. Subsequent LC-MS/MS analysis identified 11 major mAb N-glycan proteoforms and assessed the relative peak areas of the glycosylated peptides. This approach is suitable for the glycosylation profiling of various human IgG mAbs, including biosimilars and different IgG subclasses. The total time required for this workflow is less than 2 h, whereas the conventional enzymatic release and labeling of glycans can take much longer. Thus, the integrated membranes are suitable for facilitating the analysis of mAb glycosylation patterns.