Effects of genistein on N-glycolylneuraminic acid content in rats and the interaction with sialyl transferase / 生物工程学报

To investigate the effects of genistein (Gen) on the biosynthesis of N-glycolylneuraminic acid (Neu5Gc) in rats, 80 4-week-old male SD rats were randomly equally into the control and genistein groups. The rats of control and genistein groups were fed 5% ethanol and 300 mg/(kg·d) genistein respectively by gavage. The contents of Neu5Gc in hind leg muscle, kidney and liver tissues of rats were measured by using high performance liquid chromatography coupled with fluorescence detector (HPLC/FLD), and the mechanism of inhibition of Neu5Gc synthesis was investigated by using the molecular docking of Gen and sialyltransferase. On the 15th day, the content of Neu5Gc in hind leg muscle and liver tissues decreased 13.77% and 15.45%, respectively, and there was no significant change in the content of Neu5Gc in kidney tissues. On the 30th day, the content of Neu5Gc in liver tissues decreased 13.35%, however, there was no significant change in the content of Neu5Gc in kidney tissues and Neu5Gc was not detected in hind leg muscle. The content of Neu5Gc in hind leg muscle, kidney and liver tissues decreased respectively 32.65%, 32.78%, 16.80% and 12.72%, 11.42%, 12.30% while rats fed on the 45th and the 60th days. Genistein has formed the hydrogen bond with sialyltransferase activity site residues His319, Ser151, Gly293, Thr328 and formed a hydrophobic interactions with the residues His302, His301, Trp300, Ser271, Phe292, Thr328, Ser325 and Ile274. The results of molecular docking indicated that the weak intermolecular interaction was the main cause of genistein inhibiting sialyltransferase activity. The research results provided an experimental basis for the subsequent reduction of Neu5Gc in red meat before slaughter.

Effects of Taxol on proliferation, apoptosis, and mRNA expression of α2,6-sialic acid and ST6Gal in cervical carcinoma cell line U14 / 中国病理生理杂志

AIM:To study the effect of Taxol on the proliferation, apoptosis, and mRNA expressions of α2,6-sialic acid (SA) and α2,6-sialyltransferase (ST6Gal) in mouse cervical cancer cell line U14.METHODS:After the U14 cells were treated with Taxol, the IC50 value of Taxol to U14 cells was detected by MTT assay.The expression of α2,6-SA and apoptosis-related factors (Bcl-2, Bax, caspase 8 and caspase 3), the apoptosis rate and cell cycle were determined by flow cytometry.The mRNA expression of ST6Gal1 and ST6Gal2 was detected by qPCR.RESULTS:As compared with control group, Taxol induced obvious U14 cell growth inhibition, reduced α2,6-SA expression, up-regulated Bax, down-regulated Bcl-2, decreased the ratio of Bcl-2/Bax, enhanced caspase 8 and caspase 3 activity, increased the apoptotic rate and cell proportions of Sub-G1 and S phases, and induced G2/M phase arrest.Taxol also down-regulated the mRNA expression of ST6Gal1, and slightly up-regulated the mRNA expression of ST6Gal2.CONCLUSION:α2,6-SA and ST6Gal are involved in the multiple effects of Taxol on modulation of the cell cycle and apoptosis in U14 cells.

Detecting the Expression of ST3GalⅤ in Human Hepatic Carcinoma Cell Lines by Sialyltransferase DNA Microarray / 沈阳医学院学报

Objective: To investigate the differential expression of ST3GalⅤ in human hepatic carcinoma cell lines, HepG?2 and SMMC?7721 and normal hepatic cell line, L?02 by sialyltransferase DNA microarray. Methods: Expression of ST3Gal family was measured with DNA microarray. Western blot was used to verify DNA microarrays data. Result:ST3GalⅤ downregulated in HepG?2 and SMMC?7721 cell lines, compared with control cell line. Conclusion: The downregulation of ST3GalⅤ in HepG?2 and SMMC?7721 cell lines may result in the reduction of GD1a and influence the hepatocyte proliferations.

Development of a novel method to evaluate sialylation of glycoproteins and analysis of gp96 sialylation in Hela, SW1990 and A549 cell lines

BACKGROUND: Glycoproteins play a critical role in the cellular activities of eukaryotes. Sialic acid is typically the outermost monosaccharide of glycolipids and glycoproteins, and is necessary for normal development. RESULTS: A strategy based on avidin-biotin affinity was established to enrich sialylated glycoproteins from HeLa cervical carcinoma, SW1990 pancreatic adenocarcinoma, and A549 lung adenocarcinoma cells. Using HPLC-MS/MS, western blot, real-time PCR, and enzyme-linked immunosorbent assay, gp96 was identified in all three cell lines. No significant difference in the protein expression of gp96 was detected at the whole cell level, but the amount of bioti-nylated gp96 in SW1990 cells was 30-40 % lower than that in A549 and HeLa cells, and the amount of sialylated gp96 in SW1990 cells was 30 % lower than that in A549 and HeLa cells. Immunoblotting results showed that the expression of sialyltransferase proteins in the total cell lysates from HeLa and A549 cells were higher than that in SW1990 cells. CONCLUSIONS: We established a new method for investigating the expression and sialylation of glycoproteins using metabolic labeling, click chemistry, and avidin-biotin affinity. We successfully used this method to purify sialylated glycoproteins from cancer cell lines. Our results showed that the levels of gp96 sialylation varied across different cancer cell lines, and this may be because of differences in sialyltransferase expression.

Effect of hepatitis C virus infection on the expressions of multiple sialyltransferases and galactosyltransferases in Huh7.5.1 cell / 中国生化药物杂志

Objective To investigate the altered glycotransferases and glycan profile in HCV-infected cells, the expression levels of 35 kinds of sialyltransferases and galactosyltransferases were evaluated in hepatitis C virus (HCV) infected Huh7.5.1 cell cultured model.Methods Western blot was used to measure the expressions of HCV-nonstructural protein NS3 and and quantitative real-time PCR (qRT-PCR) was performed to determine HCV-RNA levels and mRNA levels of 35 kinds of sialyltransferases and galactosyltransferases.Lectin microarray was used to compare the glycan profiles of sialyltransferases-and galactosyltransferases-associated glycan-profile in Huh7.5.1 cells and HCV infected Huh7.5.1 cells.Results Among the 35 kinds of sialyltransferases and galactosyltransferases, the mRNA levels of four sialyltransferases (including ST3Gal Ⅲ, ST6GalNAC Ⅲ, ST8Sia Ⅲ and ST8SiaⅣ) and five galactosyltransferases (including B3GALT1, B3GALT 2, B3GALT3, B3GALT4 and B4GALNT2) were found to be 11-45 fold higher in HCV-infected cells compared with naive Huh7.5.1 cells.The up-regulated level of B3GALT 1 was the most evident (45-fold change), followed by ST8Sia Ⅳ and ST8Sia Ⅲ, with 39-and 37-fold respectively.Consistently, lectin microarray showed that glycans recognized by EBL (binding terminal sialic acid, Neu5Acα6Gal, 1.97-fold change), ECA letin (binding terminal galactose, Galβ1,4GalNAc,4.3-fold change), and ACA(binding terminal galactose, Galβ1-3GalNAc, 3-fold change) were elevated in glycoprotein products of sialyltransferase and galactosyltransferase respectively.Conclusion HCV infection causes the increased expression levels of mutiple sialyltransferases and galactosyltransferases in Huh7.5.1 cell line and hence the upregulation of glycan profiles of the glycoproteins.These results provide potential therapeutic targets and diagnostic markers for HCV infection and insights on the molecular mechanism of HCV infection.

Increasing the alpha 2, 6 Sialylation of Glycoproteins May Contribute to Metastatic Spread and Therapeutic Resistance in Colorectal Cancer

Abnormal glycosylation due to dysregulated glycosyltransferases and glycosidases is a key phenomenon of many malignancies, including colorectal cancer (CRC). In particular, increased ST6 Gal I (beta-galactoside alpha 2, 6 sialyltransferase) and subsequently elevated levels of cell-surface alpha 2, 6-linked sialic acids have been associated with metastasis and therapeutic failure in CRC. As many CRC patients experience metastasis to the liver or lung and fail to respond to curative therapies, intensive research efforts have sought to identify the molecular changes underlying CRC metastasis. ST6 Gal I has been shown to facilitate CRC metastasis, and we believe that additional investigations into the involvement of ST6 Gal I in CRC could facilitate the development of new diagnostic and therapeutic targets. This review summarizes how ST6 Gal I has been implicated in the altered expression of sialylated glycoproteins, which have been linked to CRC metastasis, radioresistance, and chemoresistance.

Characterization of P1 promoter activity of the β-galactoside α2,6-sialyltransferase I gene (siat 1) in cervical and hepatic cancer.

The level of β-galactoside α2,6-sialyltransferase I (ST6Gal I) mRNA, encoded by the gene siat1, is increased in malignant tissues. Expression is regulated by different promoters – P1, P2 and P3 – generating three mRNA isoforms H, X and YZ. In cervical cancer tissue the mRNA isoform H, which results from P1 promoter activity, is increased. To study the regulation of P1 promoter, different constructs from P1 promoter were evaluated by luciferase assays in cervical and hepatic cell lines. Deletion of a fragment of 1048 bp (−89 to +24 bp) increased 5- and 3-fold the promoter activity in C33A and HepG2 cell lines, respectively. The minimal region with promoter activity was a 37 bp fragment in C33A cells. The activity of this region does not require the presence of an initiator sequence. In HepG2 cells the minimal promoter activity was detected in the 66 bp fragment. Sp1 (−32) mutation increased the promoter activity only in HepG2 cells. HNF1 mutation decreased promoter activity in HepG2 cell line but not in C33A cells. We identified a large region that plays a negative regulation role. The regulation of promoter activity is cell type specific. Our study provides new insights into the complex transcriptional regulation of siat1 gene.

Mutational analysis for enzyme activity of mouse Gal1,3GalNAc 2,3-sialyltransferase (mST3Gal I).

To determine which amino acid residues are essential for the catalytic activity of mouse Gal1,3GalNAc 2,3-sialyltransferase (mST3Gal I), chemical modification and site-directed mutagenesis were employed against tryptophan and cysteine residues located in the predicted catalytic domain. This enzyme was strongly inhibited by N-bromosuccinimide, a specific blocking reagent for tryptophan residues, and the enzyme activity was completely lost at 3 mM, suggesting the involvement of tryptophan residues in the catalytic activity of mST3Gal I. The N-ethylmaleimide, an irreversible reagent for sulfhydryl group, significantly inhibited the enzyme activity. Seven tryptophan and six cysteine residues conserved in the cloned Gal1,3GalNAc 2,3-sialyltransferases were separately substituted into phenylalanine and serine, respectively. The enzymatic activity assay for tryptophan mutants produced in COS cells showed a complete abolishment of the activity in all of the mutants, except that W70F and W97F retained about 60% and 40% activities of wild type, respectively. In the case of cysteine mutants, no enzyme activity was observed like tryptophan mutants, except for C139S. These results suggest that tryptophan and cysteine residues conserved in ST3Gal I are critical for its activity.

Triptolide downregulates human GD3 synthase (hST8Sia I) gene expression in SK-MEL-2 human melanoma cells

In this study, we have shown that gene expression of human GD3 synthase (hST8Sia I) is suppressed by triptolide (TPL) in human melanoma SK-MEL-2 cells. To elucidate the mechanism underlying the downregulation of hST8Sia I gene expression in TPL-treated SK-MEL-2 cells, we characterized the TPL-inducible promoter region within the hST8Sia I gene using luciferase constructs carrying 5'-deletions of the hST8Sia I promoter. Functional analysis of the 5'-flanking region of the hST8Sia I gene demonstrated that the -1146 to -646 region, which contains putative binding sites for transcription factors c-Ets-1, CREB, AP-1 and NF-kappaB, functions as the TPL-inducible promoter of hST8Sia I in SK-MEL-2 cells. Site-directed mutagenesis and ChIP analysis indicated that the NF-kappaB binding site at -731 to -722 is crucial for TPL-induced suppression of hST8Sia I in SK-MEL-2 cells. This suggests that TPL induces down-regulation of hST8Sia I gene expression through NF-kappaB activation in human melanoma cells.

Enhanced sialyltransferases transcription in cervical intraepithelial neoplasia

Altered sialylation observed during oncogenic transformation, tumor metastases and invasion, has been associated with enhanced sialyltransferases (STs) transcription. Increased mRNA expression of STs (ST6Gal I, ST3Gal III) has been detected in invasive cervical squamous cell carcinoma. A study of the sialic acid concentration in local tissue of cervix and in serum showed a slight elevation in benign inflammatory lesions and a moderate elevation in severe neoplasia, but to date, altered expression of STs in cervical intraepithelial neoplasia has not yet been evaluated. This study investigates the changes in mRNA expression of three STs (ST6Gal I, ST3Gal III, and ST3Gal IV) in cervical intraepithelial lesions (CIN). Alterations of these STs mRNA expression were examined in 35 cervix specimens classified as normal, CIN 1, CIN 2 and CIN 3, by semiquantitative reverse transcription-polymerase chain reaction. mRNA expression of the three STs was enhanced in CIN 1, CIN 2 and CIN 3 with respect to normal tissue, with a significant difference of p < 0.001 (Mann-Whitney U test) for all the enzymes. Our results suggest that altered expression of ST3Gal III, ST3Gal IV and ST6Gal I in CIN could play an important role during malignant transformation and could be related with the enhanced sialic acid expression detected in neoplasic tissues.

La sialilación alterada que se ha detectado durante la transformación maligna, en los tumores con invasión y metástasis ha sido asociada con un incremento en la transcripción de sialiltransferasas (STs). En carcinoma escamoso cervical invasor ha sido detectado un incremento en la expresión del ARNm de STs (ST3Gal III y ST6Gal I). Un estudio realizado en muestras de cérvix mostró un ligero incremento en la expresión de ácido siálico en lesiones inflamatorias benignas y un incremento moderado en neoplasia severa, con respecto al tejido normal, sin embargo, a la fecha la expresión alterada de STs en la neoplasia intraepitelial cervical no ha sido evaluada. Este estudio tuvo como finalidad investigar los cambios en el nivel de transcripción de tres STs (ST3Gal III, ST3Gal IV y ST6Gal I) en la neoplasia intraepitelial cervical (NIC). Para ello se analizaron 35 biopsias de cérvix clasificadas como: normal, NIC 1, NIC 2 y NIC 3, mediante ensayos semicuantitativos de RT-PCR. El nivel de transcripción de las tres STs se incrementó en las muestras con diagnóstico de neoplasia intraepitelial cervical con respecto al tejido normal, con una diferencia significativa de p < 0.001 (Mann-Whitney U test) para todas las enzimas. Nuestros resultados sugieren que la expresión alterada de las STs: ST3Gal III, ST3Gal IV y ST6Gal I, en la neoplasia intraepitelial cervical puede tener un papel importante durante la transformación maligna y estar relacionada con los incrementos en la expresión de ácido siálico detectado en tejido con neoplasia cervical.

Biosynthesis of eukaryotic cell surface glycosphingolipids using solubilized glycosyltransferases.

Two fucsyltransferases (FucT-2 and FucT-3) have been solubilized from Golgi-rich membrane fraction of bovine spleen, using a cationic detergent. FucT-3 was distinguished from FucT-2 by comparing their kinetic parameters and heat stability. FucT-2 and FucT-3 lost activity (85 %) and (5 %), respectively, when heated at 55°C for 10 sec. Two galactosyltransferases (GalT-3 and GalT-4) and two sialyltransferases (SAT-2 and SAT-3) have also been solubilized from embryonic chicken brain membranes using nonionic detergents. Affinity chromatography and microisoelectric focusing were used to separate these enzymes into functionally pure fractions. Anomeric and positional linkages in some of the products (LM1 and LD1c) have also been established. The terminal NeuAc(α2–8) linkage in GD3 and LD1c was established by identification of the partially methylated penultimate [Ac-14C]sialic acid.