Tissue-specific mRNA expression profiles of human carbohydrate sulfotransferase and tyrosylprotein sulfotransferase

Sulfotransferase activity contributes to long-term potentiation and long-term memory

A critical role of protein modifications such as phosphorylation and acetylation in synaptic plasticity and memory is well documented. Tyrosine sulfation plays important roles in several biological processes. However, its role in synaptic plasticity and memory is not well understood. Here, we show that sulfation contributes to long-term potentiation (LTP) in the hippocampal slices. In addition, inhibition of sulfation impairs long-term memory in a spatial memory task without affecting acquisition or short-term memory. Furthermore, LTP-inducing stimulus enhances protein tyrosine sulfation. These results suggest an important role for tyrosine sulfation in LTP and memory.

Tyrosine-sulfated dermatopontin shares multiple binding sites and recognition determinants on triple-helical collagens with proteins implicated in cell adhesion and collagen folding, fibrillogenesis, cross-linking, and degradation

Dermatopontin (DPT), a small extracellular matrix protein that stimulates collagen fibrillogenesis, contains sulfotyrosine residues but neither its level of sulfation nor its binding sites on fibrillar collagens are known. Here, we discovered that DPT is present in a relatively high mass concentration (~ 0.02%) in porcine corneal stroma, from which we purified five DPT charge variants (A-E) containing up to six sulfations. The major variant (C), containing four sulfotyrosine residues, was used to locate binding sites for DPT on triple-helical collagens II and III using the Collagen Toolkits. DPT-binding loci included the triple helix crosslinking sites and collagenase cleavage site. We find that strong DPT-binding sites on triple-helical collagen comprise an arginine-rich, positively-charged sequence that also contains hydrophobic residues. This collagen-binding signature of DPT is similar to that of the chaperone HSP47. Thus, we propose that DPT assumes the role of HSP47 as a collagen chaperone during and after the secretion. Peptide II-44, harbouring the conserved collagenase cleavage site, shows the strongest DPT-binding of the Collagen Toolkit II peptides. Substituting any of the three arginine residues (R) with alanine in the sequence GLAGQRGIVGLOGQRGER of II-44 resulted in almost complete loss of DPT binding. Since osteogenesis imperfecta, spondyloepiphyseal dysplasia, and spondyloepimetaphyseal dysplasia congenita are associated with missense mutations that substitute the corresponding arginine residues in collagens alpha-1(I) and alpha-1(II), we suggest that disrupted DPT binding to fibrillar collagens may contribute to these connective tissue disorders. In conclusion, the present work provides a cornerstone for further elucidation of the role of DPT.

Human Milk Oligosaccharides Differently Modulate Goblet Cells Under Homeostatic, Proinflammatory Conditions and ER Stress

SCOPE

Human milk oligosaccharides (hMOs) have beneficial effects on intestinal barrier function, but the mechanisms of action are not well understood. Here, the effects of hMOs on goblet cells, which indicate that some hMOs may enhance mucus barrier function through direct modulation of goblet cell function, are studied.

METHODS AND RESULTS

The modulatory effects of 2'-fucosyllactose (2'-FL), 3-fucosyllactose (3-FL), lacto-N-triaose II (LNT2), and galacto-oligosaccharides (GOS) on the expression of goblet cell secretory related genes MUC2, TFF3, and RETNLB, and the Golgi-sulfotransferase genes CHST5 and GAL3ST2 of LS174T are determined by real-time quantitative RT-PCR. 3-FL, LNT2, and GOS-modulated LS174T gene expression profiles in a dose- and time-dependent manner. In addition, the upregulation of MUC2 is confirmed by immunofluorescence staining. Effects of 2'-FL, 3-FL, LNT2, and GOS on gene transcription of LS174T are also assessed during exposure to TNF-α, IL-13, or tunicamycin. During TNF-α challenge, 3-FL and LNT2 enhance MUC2 and TFF3 gene expression. After IL-13 exposure, 2'-FL, 3-FL, and LNT2 all show upregulating effects on MUC2; 3-FL and LNT2 also enhance TFF3 expression. LNT2 significantly reverses Tm-induced downregulation of TFF3, RETNLB, and CHST5.

CONCLUSION

The findings indicate that hMOs may enhance mucus barrier function through direct modulation of intestinal goblet cells. Effects are structure- and stressor-dependent.

Preparation of Tyrosylprotein Sulfotransferases for In Vitro One-Pot Enzymatic Synthesis of Sulfated Proteins/Peptides

Protein tyrosine sulfation (PTS), catalyzed by membrane-anchored tyrosylprotein sulfotransferase (TPST), is one of the most common post-translational modifications of secretory and transmembrane proteins. PTS, a key modulator of extracellular protein-protein interactions, accounts for various important biological activities, namely, virus entry, inflammation, coagulation, and sterility. The preparation and characterization of TPST is fundamental for understanding the synthesis of tyrosine-sulfated proteins and for studying PTS in biology. A sulfated protein was prepared using a TPST-coupled protein sulfation system that involves the generation of the active sulfate 3'-phosphoadenosine-5'-phosphosulfate (PAPS) through either PAPS synthetase (PAPSS) or phenol sulfotransferase. The preparation of sulfated proteins was confirmed through radiometric or immunochemical assays. In this study, enzymatically active Drosophila melanogaster TPST (DmTPST) and human TPSTs (hTPST1 and hTPST2) were expressed in Escherichia coli BL21(DE3) host cells and purified to homogeneity in high yield. Our results revealed that recombinant DmTPST was particularly useful considering its catalytic efficiency and ease of preparation in large quantities. This study provides tools for high-efficiency, one-step synthesis of sulfated proteins and peptides that are useful for further deciphering the mechanisms, functions, and future applications of PTS.

Specific Unbinding Forces Between Mutated Human P-Selectin Glycoprotein Ligand-1 and Viral Protein-1 Measured Using Force Spectroscopy

Protein tyrosine sulfation (PTS) is a key modulator of extracellular protein-protein interaction (PPI), which regulates principal biological processes. For example, the capsid protein VP1 of enterovirus 71 (EV71) specifically interacts with sulfated P-selectin glycoprotein ligand-1 (PSGL-1) to facilitate virus invasion. Currently available methods cannot be used to directly observe PTS-induced PPI. In this study, atomic force microscopy was used to measure the interaction between sulfated or mutated PSGL-1 and VP1. We found that the binding strength increased by 6.7-fold following PTS treatment on PSGL-1 with a specific antisulfotyrosine antibody. Similar results were obtained when the antisulfotyrosine antibody was replaced with the VP1 protein of EV71; however, the interaction forces of VP1 were only approximately one-third of those of the antisulfotyrosine antibody. We also found that PTS on the tyrosine-51 residue of glutathione S-transferases fusion-PSGL-1 was mainly responsible for the PTS-induced PPI. Our results contribute to the fundamental understanding of PPI regulated through PTS.

Galacto-oligosaccharides may directly enhance intestinal barrier function through the modulation of goblet cells

SCOPE

Here we have tested the hypothesis that prebiotic galacto-oligosaccharides (GOS) may enhance mucosal barrier function through direct modulation of goblet cell function.

METHODS AND RESULTS

Human adenocarcinoma-derived LS174T cells, which exhibit an intestinal goblet cell-like phenotype, were used to examine the non-prebiotic effects of GOS on goblet cell functions. LS174T cells were treated with GOS, and the expression of goblet cell secretory product genes mucin 2 (MUC2), trefoil factor 3 (TFF3), resistin-like molecule beta (RETNLB) and the Golgi-sulfotransferase genes, carbohydrate (N-acetylglucosamine-6-O) sulfotransferase 5 (CHST5) and galactose-3-O-sulfotransferase 2 (GAL3ST2), was determined by real-time quantitative RT-PCR. In addition, the abundance of CHST5, TFF3 and RETNLB was confirmed by Western blot analysis. Following treatment with GOS for 72 h, the expression of MUC2 was significantly upregulated 2-4-fold, CHST5 and RETNLB, 5-7-fold, and TFF3 2-4-fold. Western blot analysis demonstrated increased abundance of RETNLB, TFF3 and CHST5. Addition of the Th2 cytokine IL-13 along with GOS resulted in synergistic induction of RETNLB and CHST5. IL-8 secretion was not affected by GOS treatment, suggesting that the effects of GOS are not mediated through an inflammatory pathway.

CONCLUSION

Collectively, the data indicate that GOS may enhance mucosal barrier function through direct stimulation of intestinal goblet cells.

Tyrosine sulfation as a protein post-translational modification

Integration of inorganic sulfate into biological molecules plays an important role in biological systems and is directly involved in the instigation of diseases. Protein tyrosine sulfation (PTS) is a common post-translational modification that was first reported in the literature fifty years ago. However, the significance of PTS under physiological conditions and its link to diseases have just begun to be appreciated in recent years. PTS is catalyzed by tyrosylprotein sulfotransferase (TPST) through transfer of an activated sulfate from 3'-phosphoadenosine-5'-phosphosulfate to tyrosine in a variety of proteins and peptides. Currently, only a small fraction of sulfated proteins is known and the understanding of the biological sulfation mechanisms is still in progress. In this review, we give an introductory and selective brief review of PTS and then summarize the basic biochemical information including the activity and the preparation of TPST, methods for the determination of PTS, and kinetics and reaction mechanism of TPST. This information is fundamental for the further exploration of the function of PTS that induces protein-protein interactions and the subsequent biochemical and physiological reactions.

Microarray comparison of the gene expression profiles in the adult vs. embryonic day 14 rat liver

The aim of the present study was to identify the differentially-expressed genes of embryonic day 14 (ED 14) rat liver in comparison to adult rat liver, which may provide specific information for the investigation of the hepatogenesis mechanism. The gene expression profiles of ED 14 and adult rat livers were investigated using microarray analysis (the Illumina RatRef-12 Expression BeadChip). Quantitative polymerase chain reaction (qPCR) analyses were conducted to confirm the gene expression. There were 787 genes upregulated in the embryonic liver. Based on the gene ontology classification system, which was analyzed by the database for annotation, visualization and integrated discovery software, a number of the upregulated genes were categorized into the distinct and differentially-expressed functional groups, including metabolism pathway, cell cycle, transcription, signal transduction, purine metabolism, cell structure, transportation and apoptosis. qPCR analyses confirmed the gene expression. Eleven upregulated genes were found in the ED 14 rat liver, which may provide specific information for the understanding of the molecular mechanisms that control hepatogenesis. These overexpressed genes are potential markers for identifying hepatic progenitor cells.

Neuregulin-1/ErbB signaling is impaired in the rat model of diabetic cardiomyopathy

BACKGROUND

Diabetic cardiomyopathy (DCP) is one of the leading causes of increased morbidity and mortality in the diabetic population. The neuregulin-1(NRG1)/ErbB signal system plays a critical role in maintenance of adult heart function. But little is known about the changes of NRG1/ErbB signal system in DCP. The aim of this study was to investigate the changes of the NRG1/ErbB signal system in DCP.

METHODS

A rat model of DCP was established using a single intraperitoneal injection of streptozotocin (STZ). Cardiac function was assessed using echocardiography. The left ventricle fibrosis was evaluated using Masson's trichrome staining. The mRNA expression profiles of ErbB2 and ErbB4 receptors were evaluated using real-time polymerase chain reaction. The protein expression of NRG1 and the phosphorylation of ErbB2 and ErbB4 receptors were assessed using Western blot analysis.

RESULTS

The results showed dramatic left ventricle fibrosis and impaired left ventricle systolic function at 12 weeks after STZ-induced diabetes. This study also showed that ErbB2 and ErbB4 mRNA expression and NRG1 protein expression in the left ventricular myocardium were significantly decreased. In addition, we observed decreased phosphorylation of the ErbB2 and ErbB4 receptors at 12 weeks after the induction of diabetes.

CONCLUSIONS

These findings suggest that NRG1/ErbB signaling is impaired in DCP, which may play some roles in the pathogenesis of DCP.

Inflammatory cues modulate the expression of secretory product genes, Golgi sulfotransferases and sulfomucin production in LS174T cells

The signals that mediate goblet cell expression of specific mucin chemotypes are poorly defined. Animal and in vitro studies show that acidomucin chemotypes may be altered by inflammation and changes in intestinal microbiota. To examine factors that may elicit this response, human adenocarcinoma-derived LS174T cells, which have a goblet cell-like phenotype and produce both sulfo- and sialomucins, were used to examine the effects of selected microbial and host factors on expression of goblet cell secretory product genes, sulfotransferases and sulfomucin production. Expression of genes encoding mucin 2 (MUC2), resistin-like molecule β (RETNLB), and trefoil factor 3 (TFF3) and Golgi sulfotransferases, carbohydrate (N-acetylglucosamine 6-O) sulfotransferase 5 (CHST5) and galactose-3-O-sulfotransferase 2 (GAL3ST2), was measured by quantitative reverse transcriptase-polymerase chain reaction following treatment with bacterial flagellin, tumor necrosis factor α (TNF-α) or the mucogenic cytokine interleukin-13 (IL-13). Expression of the toll-like receptor 5 (TLR5) gene was also analysed. Sulfomucin expression was examined via high-iron diamide/alcian blue (HID/AB) histochemistry and immunofluorescent staining for the Sulfo Le(a) antigen, which is synthesized in part by GAL3ST2. Flagellin, IL-13 and TNF-α all significantly increased GAL3ST2, MUC2, TFF3 and TLR5 expression, while only IL-13 increased RETNLB and CHST5 expression. Based on HID/AB histochemistry, mucin sulfation was significantly increased in response to both flagellin and IL-13 but not TNF-α. Only treatment with flagellin increased the expression of the Sulfo Le(a) antigen. Collectively, these results indicate that bacterial flagellin, IL-13 and TNF-α differentially modulate the expression of goblet cell secretory product genes, sulfotransferases and sulfomucin production.

Sequence analysis of the human tyrosylprotein sulfotransferase-2 gene in subjects with chronic pancreatitis

BACKGROUND/AIMS

Human trypsinogens are post-translationally sulfated on Tyr154 by the Golgi resident enzyme tyrosylprotein sulfotransferase-2 (TPST2). Tyrosine sulfation stimulates the autoactivation of human cationic trypsinogen. Because increased trypsinogen autoactivation has been implicated as a pathogenic mechanism in chronic pancreatitis, we hypothesized that genetic variants of TPST2 might alter the risk for the disease.

METHODS

We sequenced the 4 protein-coding exons and the adjacent intronic sequences of TPST2 in 151 subjects with chronic pancreatitis and in 169 healthy controls. The functional effect of TPST2 variants on trypsinogen sulfation was analyzed in transfected HEK 293T cells.

RESULTS

We detected 10 common polymorphic variants, including 6 synonymous variants and 4 intronic variants, with similar frequencies in patients and controls. None of the 8 common haplotypes reconstructed from the frequent variants showed an association with chronic pancreatitis. In addition, we identified 5 rare TPST2 variants, which included 3 synonymous alterations, the c.458G>A (p.R153H) nonsynonymous variant and the c.-9C>T variant in the 5' untranslated region. The p.R153H variant was found in a family with hereditary pancreatitis; however, it did not segregate with the disease. In functional assays, both the p.R153H and c.-9C>T TPST2 variants catalyzed trypsinogen sulfation as well as wild-type TPST2.

CONCLUSION

Genetic variants of human TPST2 exert no influence on the risk of chronic pancreatitis.

Protein tyrosine-O-sulfation in the retina

Tyrosine-O-sulfation, a post-translational modification, is catalyzed by two independent tyrosylprotein sulfotransferases (TPSTs). As an initial step towards understanding the role of TPSTs in retinal function, this study was undertaken to determine the extent to which tyrosine-O-sulfation of proteins is utilized in the retina. A previously characterized anti-sulfotyrosine antibody was used to determine the presence and localization of tyrosine-O-sulfated proteins (TOSPs) in the retina. Using Western blot, RT-PCR and immunohistochemical analyses, we detected TOSPs in the retinas from diverse species, including frog, fish, mouse and human. Some of the variability in the observed sizes of retinal TOSPs in the mouse, at least, may result from differential patterns of glycosylation; however, there seem to be species-specific sulfated retinal proteins as well. TOSPs were detected in most of the retinal layers as well as in the retinal pigment epithelium from human and mouse. Several retinal TOSPs were detected in the inter-photoreceptor matrix, which is consistent with the secreted nature of some sulfated proteins. Transcripts for both TPST-1 and TPST-2 were expressed in both the human and mouse retinas. These data show that retinal protein tyrosine-O-sulfation is highly conserved which suggest a functional significance of these proteins to retinal function and structure.

A common African polymorphism abolishes tyrosine sulfation of human anionic trypsinogen (PRSS2)

Human pancreatic trypsinogens undergo post-translational sulfation on Tyr(154), catalysed by the Golgi-resident enzyme tyrosylprotein sulfotransferase 2. Sequence alignments suggest that the sulfation of Tyr(154) is facilitated by a unique sequence context which is characteristically found in primate trypsinogens. In the search for genetic variants that might alter this sulfation motif, we identified a single nucleotide polymorphism (c.457G>C) in the PRSS2 (serine protease 2, human anionic trypsinogen) gene, which changed Asp(153) to a histidine residue (p.D153H). The p.D153H variant is common in subjects of African origin, with a minor allele frequency of 9.2%, whereas it is absent in subjects of European descent. We demonstrate that Asp(153) is the main determinant of tyrosine sulfation in anionic trypsinogen, as both the natural p.D153H variation and the p.D153N mutation result in a complete loss of trypsinogen sulfation. In contrast, mutation of Asp(156) and Glu(157) only slightly decrease tyrosine sulfation, whereas mutation of Gly(151) and Pro(155) has no effect. With respect to the biological relevance of the p.D153H variant, we found that tyrosine sulfation had no significant effect on the activation of anionic trypsinogen or the catalytic activity and inhibitor sensitivity of anionic trypsin. Taken together with previous studies, the observations of the present study suggest that the primary role of trypsinogen sulfation in humans is to stimulate autoactivation of PRSS1 (serine protease 1, human cationic trypsinogen), whereas the sulfation of anionic trypsinogen is unimportant for normal digestive physiology. As a result, the p.D153H polymorphism which eliminates this modification could become widespread in a healthy population.