TNF up-regulates ST3GAL4 and sialyl-Lewisx expression in lung epithelial cells through an intronic ATF2-responsive element

ST3GalIV drives SLeX biosynthesis in gastrointestinal cancer cells and associates with cancer cell motility

Expression of sialyl Lewis X (SLeX) is a well-documented event during malignant transformation of cancer cells, and largely associates with their invasive and metastatic properties. Glycoproteins and glycolipids are the main carriers of SLeX, whose biosynthesis is known to be performed by different glycosyltransferases, namely by the family of β-galactoside-α2,3-sialyltransferases (ST3Gals). In this study, we sought to elucidate the role of ST3GalIV in the biosynthesis of SLeX and in malignant properties of gastrointestinal (GI) cancer cells. By immunofluorescent screening, we selected SLeX-positive GI cancer cell lines and silenced ST3GalIV expression via CRISPR/Cas9. Flow cytometry, immunofluorescence and western blot analysis showed that ST3GalIV KO efficiently impaired SLeX expression in most cancer cell lines, with the exception of the colon cancer cell line LS174T. The impact of ST3GalIV KO in the biosynthesis of SLeX isomer SLeA and non sialylated Lewis X and A were also evaluated and overall, ST3GalIV KO led to a decreased expression of SLeA and an increased expression in both LeX and LeA. In addition, the abrogation of SLeX on GI cancer cells led to a reduction in cell motility. Furthermore, ST3GalVI KO was performed in LS174T ST3GalIV KO cells, resulting in the complete abolishment of SLeX expression and consequent reduced motility capacity of those cells. Overall, these findings portray ST3GalIV as the main, but not the only, enzyme driving the biosynthesis of SLeX in GI cancer cells, with a functional impact on cancer cell motility.

Targeting protein glycosylation to regulate inflammation in the respiratory tract: novel diagnostic and therapeutic candidates for chronic respiratory diseases

Protein glycosylation is a widespread posttranslational modification that can impact the function of proteins. Dysregulated protein glycosylation has been linked to several diseases, including chronic respiratory diseases (CRDs). CRDs pose a significant public health threat globally, affecting the airways and other lung structures. Emerging researches suggest that glycosylation plays a significant role in regulating inflammation associated with CRDs. This review offers an overview of the abnormal glycoenzyme activity and corresponding glycosylation changes involved in various CRDs, including chronic obstructive pulmonary disease, asthma, cystic fibrosis, idiopathic pulmonary fibrosis, pulmonary arterial hypertension, non-cystic fibrosis bronchiectasis, and lung cancer. Additionally, this review summarizes recent advances in glycomics and glycoproteomics-based protein glycosylation analysis of CRDs. The potential of glycoenzymes and glycoproteins for clinical use in the diagnosis and treatment of CRDs is also discussed.

Curcumin-mediated transcriptional regulation of human N-acetylgalactosamine-α2,6-sialyltransferase which synthesizes sialyl-Tn antigen in HCT116 human colon cancer cells

Human N-acetylgalactosamine-α2,6-sialyltransferase (hST6GalNAc I) is the major enzyme involved in the biosynthesis of sialyl-Tn antigen (sTn), which is known to be expressed in more than 80% of human carcinomas and correlated with poor prognosis in cancer patients. Athough high expression of hST6GalNAc I is associated with augmented proliferation, migration and invasion in various cancer cells, transcriptional mechanism regulating hST6GalNAc I gene expression remains largely unknown. In this study, we found that hST6GalNAc I gene expression was markedly augmented by curcumin in HCT116 human colon carcinoma cells. To understand the molecular mechanism for the upregulation of hST6GalNAc I gene expression by curcumin in HCT116 cells, we first determined the transcriptional start site of hST6GalNAc I gene by 5′-RACE and cloned the proximal hST6GalNAc I 5′-flanking region spanning about 2 kb by PCR. Functional analysis of the hST6GalNAc I 5′ flanking region of hST6GalNAc I by sequential 5′-deletion, transient transfection of reporter gene constructs and luciferase reporter assays showed that -378/-136 region is essential for maximal activation of transcription in response to curcumin in HCT 116 cells. This region includes putative binding sites for transcription factors c-Ets-1, NF-1, GATA-1, ER-α, YY1, and GR-α. ChIP analysis and site-directed mutagenesis demonstrated that estrogen receptor α (ER-α) binding site (nucleotides -248/-238) in this region is crucial for hST6GalNAc I gene transcription in response to curcumin stimulation in HCT116 cells. The transcription activity of hST6GalNAc I gene induced by curcumin in HCT116 cells was strongly inhibited by PKC inhibitor (Gö6983) and ERK inhibitor (U0126). These results suggest that curcumin-induced hST6GalNAc I gene expression in HCT116 cells is modulated through PKC/ERKs signal pathway.

Role of a Disease-associated ST3Gal-4 in Non-small Cell Lung Cancer

Sialylation promotes tumorigenesis by affecting various cancer-related events, including apoptosis inhibition, cell growth, invasion, migration, metastasis, chemo-resistance, and immunomodulation in favor of tumor progression. An altered expression of sialyltransferase enzymes is responsible for synthesizing various tumor-associated sialylated structures. In the present study, our findings have revealed a significant up-regulation of ST3Gal-4 transcript in the two major subtypes of NSCLC cell lines [squamous cell carcinoma cell line (NCI-H520) and adenocarcinoma cell line (A549)]. Thus, the role of the ST3Gal-4 gene was assessed on cancer-associated signal transduction pathways in these cells in view of proliferation, invasion, and migration. ST3Gal-4 was silenced by transfection of both the cell lines with esi-ST3Gal-4-RNA, which RT-PCR and western immunoblotting confirmed. Silencing of ST3Gal-4 resulted in a decreased expression of MAL-I interacting membrane-HSP60, identified earlier as an α2,3-sialylated glycoprotein, thus pointing towards the possible role of ST3Gal-4 in its sialylation. The proliferation, invasion, and migration of both types of NSCLC cells were reduced significantly in the ST3Gal-4 silenced cells. Our findings were substantiated by the down-regulation of β-catenin and E-cadherin, a reduced expression of activated AKT1, ERK1/2, and NF-ƙB in these cells. We propose that ST3Gal-4 may be the disease-associated sialyltransferase involved in α2,3 sialylation of the membrane proteins, including HSP60 of the NSCLC cells. This may lead to the conformational alteration of these proteins, required for the activation of E-cadherin/β-catenin, AKT, and ERK/NF-ƙB mediated signal transduction pathways in these cells, resulting in their proliferation, invasion, and migration.

Analysis of the proximal promoter of the human colon-specific B4GALNT2 (Sda synthase) gene: B4GALNT2 is transcriptionally regulated by ETS1

BACKGROUND

The Sda antigen and corresponding biosynthetic enzyme B4GALNT2 are primarily expressed in normal colonic mucosa and are down-regulated to a variable degree in colon cancer tissues. Although their expression profile is well studied, little is known about the underlying regulatory mechanisms.

METHODS

To clarify the molecular basis of Sda expression in the human gastrointestinal tract, we investigated the transcriptional regulation of the human B4GALNT2 gene. The proximal promoter region was delineated using luciferase assays and essential trans-acting factors were identified through transient overexpression and silencing of several transcription factors.

RESULTS

A short cis-regulatory region restricted to the -72 to +12 area upstream of the B4GALNT2 short-type transcript variant contained the essential promoter activity that drives the expression of the human B4GALNT2 regardless of the cell type. We further showed that B4GALNT2 transcriptional activation mostly requires ETS1 and to a lesser extent SP1.

CONCLUSIONS

Results presented herein are expected to provide clues to better understand B4GALNT2 regulatory mechanisms.

Mycobacterium tuberculosis Infection Up-Regulates Sialyl Lewis X Expression in the Lung Epithelium

Glycans display increasingly recognized roles in pathological contexts, however, their impact in the host-pathogen interplay in many infectious diseases remains largely unknown. This is the case for tuberculosis (TB), one of the ten most fatal diseases worldwide, caused by infection of the bacteria Mycobacterium tuberculosis. We have recently reported that perturbing the core-2 O-glycans biosynthetic pathway increases the host susceptibility to M. tuberculosis infection, by disrupting the neutrophil homeostasis and enhancing lung pathology. In the present study, we show an increased expression of the sialylated glycan structure Sialyl-Lewis X (SLeX) in the lung epithelium upon M. tuberculosis infection. This increase in SLeX glycan epitope is accompanied by an altered lung tissue transcriptomic signature, with up-regulation of genes codifying enzymes that are involved in the SLeX core-2 O-glycans biosynthetic pathway. This study provides novel insights into previously unappreciated molecular mechanisms involving glycosylation, which modulate the host response to M. tuberculosis infection, possibly contributing to shape TB disease outcome.

Sprouty2 Inhibits Migration and Invasion of Fibroblast-Like Synoviocytes in Rheumatoid Arthritis by Down-regulating ATF2 Expression and Phosphorylation

Activating transcription factor 2(ATF2), a transcription factor belonging to the AP-1 family, plays an important role in inflammation. However, its biological functions and underlying molecular mechanisms in rheumatoid arthritis (RA) remain unclear. Western blot and immunohistochemistry were used to identify the expression of ATF2 and Sprouty2(SPRY2) in RA synovial tissues. SW982 cells were stimulated by TNF-α to establish an in vitro RA fibroblast-like synoviocyte (RA-FLS) model. Transwell and monolayer wound-healing were used to detect cell migration and invasion. RNA interference (si-ATF2) and adenovirus vector (Ad-SPRY2) methods were employed to manipulate ATF2 or SPRY2 expression in SW982 cells. The protein expression and phosphorylation levels in SW982 cells were evaluated by western blot. ATF2 expression and phosphorylation were upregulated in the RA synovial tissues. In RA-FLS model, ATF2 expression and phosphorylation were increased in a time-dependent manner. ATF2 knockdown inhibited the migration and invasion of RA-FLS model, reducing the inflammatory factors, which was consistent with the influence on cell behaviors caused by SPRY2 overexpression. Moreover, SPRY2 overexpression inhibited the TNF-α-induced phosphorylation of ERK and ATF2 in SW982 cells. The high expression and phosphorylation of ATF2 promoted migration and invasion of RA-FLSs. SPRY2 might inhibited the inflammatory responses of RA-FLSs via suppressing ERK-ATF2 pathway.

Insight in Adhesion Protein Sialylation and Microgravity Dependent Cell Adhesion-An Omics Network Approach

The adhesion behavior of human tissue cells changes in vitro, when gravity forces affecting these cells are modified. To understand the mechanisms underlying these changes, proteins involved in cell-cell or cell-extracellular matrix adhesion, their expression, accumulation, localization, and posttranslational modification (PTM) regarding changes during exposure to microgravity were investigated. As the sialylation of adhesion proteins is influencing cell adhesion on Earth in vitro and in vivo, we analyzed the sialylation of cell adhesion molecules detected by omics studies on cells, which change their adhesion behavior when exposed to microgravity. Using a knowledge graph created from experimental omics data and semantic searches across several reference databases, we studied the sialylation of adhesion proteins glycosylated at their extracellular domains with regards to its sensitivity to microgravity. This way, experimental omics data networked with the current knowledge about the binding of sialic acids to cell adhesion proteins, its regulation, and interactions in between those proteins provided insights into the mechanisms behind our experimental findings, suggesting that balancing the sialylation against the de-sialylation of the terminal ends of the adhesion proteins' glycans influences their binding activity. This sheds light on the transition from two- to three-dimensional growth observed in microgravity, mirroring cell migration and cancer metastasis in vivo.

Glycosylation changes in inflammatory diseases

Glycosylation is one of the most important modifications of proteins and lipids, and cell surface glycoconjugates are thought to play important roles in a variety of biological functions including cell-cell and cell-substrate interactions, bacterial adhesion, cell immunogenicity and cell signaling. Alterations of glycosylation are observed in a number of inflammatory diseases. Pro-inflammatory cytokines have been shown to modulate cell surface glycosylation by regulating the expression of glycosyltransferases and sulfotransferases involved in the biosynthesis of glycan chains, inducing the expression of specific carbohydrate antigens at the cell surface that can be recognized by different types of lectins or by bacterial adhesins, contributing to the development of diseases. Glycosylation can also regulate biological functions of immune cells by recruiting leukocytes to inflammation sites with pro- or anti-inflammatory effects. Cell surface proteoglycans provide a large panel of binding sites for many mediators of inflammation, and regulate their bio-availability and functions. In this review, we summarize the current knowledge of the glycosylation changes occurring in mucin type O-linked glycans, glycosaminoglycans, as well as in glycosphingolipids, with a particular focus on cystic fibrosis and neurodegenerative diseases, and their consequences on cell interactions and disease progression.

TNF differentially regulates ganglioside biosynthesis and expression in breast cancer cell lines

Gangliosides are glycosphingolipids concentrated in glycolipid-enriched membrane microdomains. Mainly restricted to the nervous system in healthy adult, complex gangliosides such as GD3 and GD2 have been shown to be involved in aggressiveness and metastasis of neuro-ectoderm derived tumors such as melanoma and neuroblastoma. GD3 synthase (GD3S), the key enzyme that controls the biosynthesis of complex gangliosides, was shown to be over-expressed in Estrogen Receptor (ER)-negative breast cancer tumors, and associated with a decreased overall survival of patients. We previously demonstrated that GD3S expression in ER-negative breast cancer cells induced a proliferative phenotype and an increased tumor growth. In addition, our results clearly indicate that Tumor Necrosis Factor (TNF) induced GD3S over-expression in breast cancer cells via NFκB pathway. In this study, we analyzed the effect of TNF on ganglioside biosynthesis and expression in breast cancer cells from different molecular subtypes. We showed that TNF up-regulated the expression of GD3S in MCF-7 and Hs578T cells, whereas no change was observed for MDA-MB-231. We also showed that TNF induced an increased expression of complex gangliosides at the cell surface of a small proportion of MCF-7 cells. These results demonstrate that TNF differentially regulates gangliosides expression in breast cancer cell lines and establish a possible link between inflammation at the tumor site environment, expression of complex gangliosides and tumor development.