β-1,4-Galactosyltransferase I involved in Schwann cells proliferation and apoptosis induced by tumor necrosis factor-alpha via the activation of MAP kinases signal pathways

Role of Glycans on Key Cell Surface Receptors That Regulate Cell Proliferation and Cell Death

Cells undergo proliferation and apoptosis, migration and differentiation via a number of cell surface receptors, most of which are heavily glycosylated. This review discusses receptor glycosylation and the known roles of glycans on the functions of receptors expressed in diverse cell types. We included growth factor receptors that have an intracellular tyrosine kinase domain, growth factor receptors that have a serine/threonine kinase domain, and cell-death-inducing receptors. N- and O-glycans have a wide range of functions including roles in receptor conformation, ligand binding, oligomerization, and activation of signaling cascades. A better understanding of these functions will enable control of cell survival and cell death in diseases such as cancer and in immune responses.

Expression profiles of long noncoding RNAs and messenger RNAs in the border zone of myocardial infarction in rats

Background

The participation of long noncoding RNAs (lncRNAs) in myocardial infarction has recently been noted. However, their underlying roles in the border zone of myocardial infarction remain unclear. This study uses microarrays to determine the profiles of lncRNAs and mRNAs in the border zone.

Methods

Bioinformatics methods were employed to uncover their underlying roles. Highly dysregulated lncRNAs was further validated via PCR.

Results

Four hundred seven lncRNAs and 752 mRNAs were upregulated, while 132 lncRNAs and 547 mRNAs were downregulated in the border zone of myocardial infarction. A circos graph was constructed to visualize the chromosomal distribution and classification of the dysregulated lncRNAs and mRNAs. The upregulated mRNAs in the border zone were most highly enriched in cytokine activity, binding, cytokine receptor binding and related processes, as ascertained through Go analysis. Pathway analysis of the upregulated mRNAs showed the most significant changes were in the TNF signaling pathway, cytokine–cytokine receptor interaction and chemokine signaling pathway and similar pathways and interactions. An lncRNA–mRNA co-expression network was established to probe into the underlying functions of the 10 most highly dysregulated lncRNAs based on their co-expressed mRNAs. In the co-expression network, we found 16 genes directly involved in myocardial infarction, including Alox5ap, Itgb2 and B4galt1. The lncRNAs AY212271, EF424788 and MRAK088538, among others, might be associated with myocardial infarction. BC166504 is probably a key lncRNA in the border zone of myocardial infarction.

Conclusions

The results may have revealed some aberrantly expressed lncRNAs and mRNAs that contribute to the underlying pathophysiological mechanisms of myocardial infarction.

The Immunological Regulation Roles of Porcine β-1, 4 Galactosyltransferase V (B4GALT5) in PRRSV Infection

B4GALT5, also known as β-1, 4 galactosyltransferase V, is one of the members of β-1, 4 galactosyltransferase gene (B4GALT) family, which was concerned with embryonic development, tumor generation, other malignant diseases. In this study, we firstly cloned porcine B4GALT (pB4GALT5) from porcine alveolar macrophages, and predicted the structural domain and function of seven porcine β-1, 4 galactosyltransferase (I–VII) based on transcriptome analysis of PRRSV infected cells. Additionally, the upregulated porcine B4GALT5 expression was detected from PRRSV infected porcine alveolar macrophage (PAM) cells. The PRRSV proliferation were slightly inhibited in overexpression of pB4GALT5 transfected cells, the interaction of B4GALT5 and GP5 of PRRSV was firstly be detected by Co-IP, and the co-location between B4GALT5 and GP5 were also observed in golgi membranes by confocal microscopy. A significant increasing mRNA transcription, including inflammatory cytokines (IFN-α, IL-6, IL-18, IL-1β, TNF-α) and some cell surface glycosylated protein involved in antigen present (MHC-I/II), cell adhesion and migration (chemokine MCP-1 and receptor CCR2; LFA-1, ICAM-1) were upregulated in B4GALT5 overexpressed PRRSV infected cells. Our results demonstrated that the regulation of pB4GALT5 plays an important roles in PRRSV proliferation and modification function in viral infection cells. And these results will make achievements by supporting the research of latent mechanisms of β-1, 4 galactosyltransferase V in antiviral immunity.

Glycosylation as a Main Regulator of Growth and Death Factor Receptors Signaling

Glycosylation is a very frequent and functionally important post-translational protein modification that undergoes profound changes in cancer. Growth and death factor receptors and plasma membrane glycoproteins, which upon activation by extracellular ligands trigger a signal transduction cascade, are targets of several molecular anti-cancer drugs. In this review, we provide a thorough picture of the mechanisms bywhich glycosylation affects the activity of growth and death factor receptors in normal and pathological conditions. Glycosylation affects receptor activity through three non-mutually exclusive basic mechanisms: (1) by directly regulating intracellular transport, ligand binding, oligomerization and signaling of receptors; (2) through the binding of receptor carbohydrate structures to galectins, forming a lattice thatregulates receptor turnover on the plasma membrane; and (3) by receptor interaction with gangliosides inside membrane microdomains. Some carbohydrate chains, for example core fucose and β1,6-branching, exert a stimulatory effect on all receptors, while other structures exert opposite effects on different receptors or in different cellular contexts. In light of the crucial role played by glycosylation in the regulation of receptor activity, the development of next-generation drugs targeting glyco-epitopes of growth factor receptors should be considered a therapeutically interesting goal.

Chronic TNFα Exposure Induces Robust Proliferation of Olfactory Ensheathing Cells, but not Schwann Cells

TNFα is persistently elevated in many injury and disease conditions. Previous reports of cytotoxicity of TNFα for oligodendrocytes and their progenitors suggest that the poor endogenous remyelination in patients with traumatic injury or multiple sclerosis may be due in part to persistent inflammation. Understanding the effects of inflammatory cytokines on potential cell therapy candidates is therefore important for evaluating the feasibility of their use. In this study, we assessed the effects of long term exposure to TNFα on viability, proliferation, migration and TNFα receptor expression of cultured rat olfactory ensheathing cells (OECs) and Schwann cells (SCs). Although OECs and SCs transplanted into the CNS produce similar myelinating phenotypes, and might be expected to have similar therapeutic uses, we report that they have very different sensitivities to TNFα. OECs exhibited positive proliferative responses to TNFα over a much broader range of concentrations than SCs. Low TNFα concentrations increased proliferation and migration of both OECs and SCs, but SC number declined in the presence of 100 ng/ml or higher concentrations of TNFα. In contrast, OECs exhibited enhanced proliferation even at high TNFα concentrations (up to 1 µg/ml) and showed no evidence of TNF cytotoxicity even at 4 weeks post-treatment. Furthermore, while both OECs and SCs expressed TNFαR1 and TNFαR2, TNFα receptor levels were downregulated in OECs after exposure to100 ng/ml TNFα for 5-7 days, but were either elevated or unchanged in SCs. These results imply that OECs may be a more suitable cell therapy candidate if transplanted into areas with persistent inflammation.

The β4GalT1 affects the fibroblast-like synoviocytes invasion in rheumatoid arthritis by modifying N-linked glycosylation of CXCR3

OBJECTIVE

The level of β-1,4-galactosyltransferase 1 (β4GalT1) is up-regulated in collagen-induced arthritis (CIA) mice. It is reported that CXC chemokine receptor 3 (CXCR3) can enhance the invasiveness of fibroblast-like synoviocytes (FLS) in rheumatoid arthritis (RA). This study aims to investigate the specific mechanism of β4GalT1 and relationship between β4GalT1 and CXCR3 in RA.

METHODS

The model of CIA mice was established to explore the role of β4GalT1. The N-glycosylation of CXCR3 was detected by mass spectrometry and western-blot. The interaction between β4GalT1 and CXCR3 was tested by immunoprecipitation. The truncted MMP-1 was detected by ELISA. Flow cytometry analysis was applied to measure ligand-receptor interaction between CXCR3 and CXCL10.

RESULTS

β4GalT1 can promote the inflammatory process of arthritis. CXCR3 was N-glycosylated and its glycosylation regulated by β4GalT1. β4GalT1 can enhance the invasiveness of FLS by modifying CXCR3. N-glycosylation of CXCR3 influences the ligand-receptor interaction between CXCR3 and CXCL10.

CONCLUSIONS

β4GalT1 can regulate N-glycans of CXCR3 in RA. N-glycans of CXCR3 affects CXCL10/CXCR3 ligand-binding which enhancing FLS invasion.

Tumor Necrosis Factor Alpha Induces Neural Stem Cell Apoptosis Through Activating p38 MAPK Pathway

Tumor necrosis factor alpha (TNF-α) is an essential cytokine that mediates cell death and has been shown to play a potential role in inducing neural stem cell (NSC) apoptosis. We have previously shown that TNF-α antagonist etanercept can suppress the transplanted NSC apoptosis induced by TNF-α in spinal cord injury (SCI) sites; however, the precise molecular mechanism remains unclear. This study aimed to investigate the signaling pathways responsible for TNF-α-induced apoptosis in NSCs. TNF-α treatment impairs cell viability and increases apoptosis of NSCs in concentration- and time-dependent manners. This is embodied in an increase in Bax and cleaved caspase-3 production, coupled with decreased Bcl-2 levels. Additionally, TNF-α remarkably increased the expression of phosphatidylinositol p38 Mitogen-activated protein kinase (p38 MAPK) in NSCs. p38 MAPK regulates apoptosis, acting as an apoptotic signal due to TNF-α exposure. TNF-α-induced apoptosis was significantly alleviated by the p38 MAPK pathway inhibitor SB203580, as well as targeted inhibition of p38 gene in NSCs, or TNF-α antagonist etanercept. These results suggest that TNF-α induces NSCs apoptosis by activating the p38 MAPK signaling pathway and etanercept acts as an effective TNF-α antagonist to prevent p38 MAPK-dependent apoptosis induced by TNF-α in NSCs. Our research represents a potential gene targeting that can prevent unnecessary grafted cell death after transplantation into the SCI models.

Neurotropin attenuates local inflammatory response and inhibits demyelination induced by chronic constriction injury of the mouse sciatic nerve

Neuropathic pain caused by nerve damage in the central and/or peripheral nervous systems is a refractory disorder and the management of such chronic pain has become a major issue. Neurotropin is a drug widely used in Japan and China to treat chronic pain. Although Neurotropin has been demonstrated to suppress chronic pain through the descending pain inhibitory system, the mechanism of analgesic action in the peripheral nervous system remains to be elucidated. In this study, we investigated the local effects of Neurotropin on peripheral nerve damage in a chronic constriction injury (CCI) model. Neurotropin reduced mRNA expressions of IL-1β, IL-6, and TNF-α in the sciatic nerve 1 day after the injury. Activation of Erk was also inhibited locally in the Neurotropin treatment group. Since Erk activation results in demyelination along with dedifferentiation of Schwann cells, we investigated the expression level of myelin basic protein. Five days after the injury, Neurotropin attenuated the downregulation of myelin basic protein in the sciatic nerve in the CCI model. Local effects of Neurotropin around the injury site may result in discovery of new treatments for not only neuropathic pain but also demyelinating diseases and peripheral nervous system injury.

Multifaceted roles of 5'-regulatory region of the cancer associated gene B4GALT1 and its comparison with the gene family

β1,4-Galactosylransferases are a family of enzymes encoded by seven B4GALT genes and are involved in the development of anticancer drug resistance and metastasis. Among these genes, the B4GALT1 shows significant variations in the transcript origination sites in different cell types/tissues and encodes an interesting dually partitioning β-1, 4-galactosyltransferase protein. We identified at 5'-end of B4GALT1 a 1.454 kb sequence forming a transcription regulatory region, referred to by us as the TR1-PE1, had all characteristics of a bidirectional promoter directing the transcription of B4GALT1 in a divergent manner along with its long non-coding RNA (lncRNA) antisense counterpart B4GALT1-AS1. The TR1-PE1 showed unique dinucleotide base-stacking energy values specific to transcription factor binding sites (TFBSs), INR and BRE, and harbored CpG Island (CGI) that showed GC skew with potential for R-loop formation at the transcription starting sites (TSSs). The 5'-regulatory axis of B4GALT1 also included five more novel TFBSs for CTCF, GLI1, TCF7L2, GATA3 and SOX5, in addition to unique (TG)18 repeats in conjunction with 22 nucleotide TG-associated sequence (TGAS). The five lncRNA B4GALT1-AS1 transcripts showed significant complementarity with B4GALT1 mRNA. In contrast, the rest of B4GALT genes showed fewer lncRNAs, and all lacked the (TG)18 and TGAS. Our results are strongly supported by the FANTOM5 study which showed tissue-specific variations in transcript origination sites for this gene. We suggest that the unique expression patterns for the B4GALT1 in normal and malignant tissues are controlled by a differential usage of 5'-B4GALT1 regulatory units along with a post-transcriptional regulation by the antisense RNA, which in turn govern the cell-matrix interactions, neoplastic progression, anticancer drug sensitivity, and could be utilized in personalized therapy.

Methylcobalamin promotes the differentiation of Schwann cells and remyelination in lysophosphatidylcholine-induced demyelination of the rat sciatic nerve

Schwann cells (SCs) are constituents of the peripheral nervous system. The differentiation of SCs in injured peripheral nerves is critical for regeneration after injury. Methylcobalamin (MeCbl) is a vitamin B12 analog that is necessary for the maintenance of the peripheral nervous system. In this study, we estimated the effect of MeCbl on SCs. We showed that MeCbl downregulated the activity of Erk1/2 and promoted the expression of the myelin basic protein in SCs. In a dorsal root ganglion neuron–SC coculture system, myelination was promoted by MeCbl. In a focal demyelination rat model, MeCbl promoted remyelination and motor and sensory functional regeneration. MeCbl promoted the in vitro differentiation of SCs and in vivo myelination in a rat demyelination model and may be a novel therapy for several types of nervous disorders.

Inhibition of SIRT2 in merlin/NF2-mutant Schwann cells triggers necrosis

Mutations in the NF2 gene cause Neurofibromatosis Type 2 (NF2), a disorder characterized by the development of schwannomas, meningiomas and ependymomas in the nervous system. Merlin, a tumor suppressor encoded by the NF2 gene, modulates activity of many essential signaling pathways. Yet despite increasing knowledge of merlin function, there are no NF2 drug therapies. In a pilot high-throughput screen of the Library of Pharmacologically Active Compounds, we assayed for compounds capable of reducing viability of mouse Schwann cells (MSC) with Nf2 inactivation as a cellular model for human NF2 schwannomas. AGK2, a SIRT2 (sirtuin 2) inhibitor, was identified as a candidate compound. SIRT2 is one of seven mammalian sirtuins that are NAD⁺ -dependent protein deacetylases. We show that merlin-mutant MSC have higher expression levels of SIRT2 and lower levels of overall lysine acetylation than wild-type control MSC. Pharmacological inhibition of SIRT2 decreases merlin-mutant MSC viability in a dose dependent manner without substantially reducing wild-type MSC viability. Inhibition of SIRT2 activity in merlin-mutant MSC is accompanied by release of lactate dehydrogenase and high mobility group box 1 protein into the medium in the absence of significant apoptosis, autophagy, or cell cycle arrest. These findings suggest that SIRT2 inhibition triggers necrosis of merlin-mutant MSCs and that SIRT2 is a potential NF2 drug target.

Mice overexpressing β-1,4-Galactosyltransferase I are resistant to TNF-induced inflammation and DSS-induced colitis

Glycosylation is an essential post-translational modification, which determines the function of proteins and important processes such as inflammation. β-1,4-galactosyltransferase I (βGalT1) is a key enzyme involved in the addition of galactose moieties to glycoproteins. Intestinal mucins are glycoproteins that protect the gut barrier against invading pathogens and determine the composition of the intestinal microbiota. Proper glycosylation of mucus is important in this regard. By using ubiquitously expressing βGalT1 transgenic mice, we found that this enzyme led to strong galactosylation of mucus proteins, isolated from the gut of mice. This galactosylation was associated with a drastic change in composition of gut microbiota, as TG mice had a significantly higher Firmicutes to Bacteroidetes ratio. TG mice were strongly protected against TNF-induced systemic inflammation and lethality. Moreover, βGalT1 transgenic mice were protected in a model of DSS-induced colitis, at the level of clinical score, loss of body weight, colon length and gut permeability. These studies put βGalT1 forward as an essential protective player in exacerbated intestinal inflammation. Optimal galactosylation of N-glycans of mucus proteins, determining the bacterial composition of the gut, is a likely mechanism of this function.

Krüppel-like factor 6 rendered rat Schwann cell more sensitive to apoptosis via upregulating FAS expression

Krüppel-like factor 6 (KLF6) is a tumor suppressor gene and play a role in the regulation of cell proliferation and apoptosis. After the peripheral nerve injury (PNI), the microenvironment created by surrounding Schwann cells (SCs) is a critical determinant of its regenerative potential. In this study, we examined the effects of KLF6 on SCs responses during PNI. Both KLF6 mRNA and protein expression levels were upregulated in the injured sciatic nerve, and immunofluorescence results showed that many KLF6-positive cells simultaneously expressed the SC markers S-100 and p75NTR. The apoptosis inducers TNFα and cisplatin upregulated KLF6 expression in primary cultured SCs and the SC line RSC96. Although KLF6 overexpression exacerbated cisplatin- and TNFα-induced apoptosis, expression levels of the apoptosis regulators Bcl2 and Bax were not significantly affected in either KLF6-overexpressing or KLF6-depleted RSC96 cells. Realtime PCR arrays and qRT-PCR demonstrated that KLF6 overexpression upregulated four pro-apoptotic genes, FAS, TNF, TNFSF12, and PYCARD, and inhibited expression of the anti-apoptotic IL10 gene expression. Further analysis revealed that FAS protein expression was positively correlated with KLF6 expression in SCs. These data suggest that KLF6 upregulation may render SCs more vulnerable to apoptosis after injury via upregulating FAS expression.

Signaling pathways regulating dose-dependent dual effects of TNF-α on primary cultured Schwann cells

After peripheral nerve injury, Schwann cells are rapidly activated to participate in the regenerative process and modulate local immune reactions. Tumor necrosis factor-α (TNF-α), one of the major initiators of the inflammatory cascade, has been known to exert pleiotropic functions during peripheral nerve injury and regeneration. In this study, we aimed to investigate the in vitro effects of TNF-α on peripheral neural cells. First, gene-microarray analysis was applied to the RNA samples extracted from injured peripheral nerves, providing the information of gene interactions post nerve injury. Then, after primary cultured Schwann cells were treated with increasing dosages (0-40 ng/ml) of TNF-α, cell proliferation and migration were examined by EdU incorporation and a transwell-based assay, and cell apoptosis was observed and quantified by electron microscopy and Annexin V-FITC assay, respectively. The results showed that lower dosages of TNF-α increased cell proliferation and migration, whereas higher dosages of TNF-α decreased cell proliferation and migration and enhanced cell apoptosis. The tests using a chemical inhibitor of TNF-α further confirmed the above effects of TNF-α. To understand how TNF-α produced the dose-dependent dual effects on primary cultured Schwann cells, we performed co-immunoprecipitation, Western blot analysis, and immunocytochemistry to decipher the complex network of biochemical pathways involving many signaling molecules, i.e., TNF receptor-associated death domain, Fas-associated death domain, receptor interacting protein, JNK, NF-κB p65, and caspases, thus assuming the mechanisms by which TNF-α activated the death and survival pathways and achieved a balance between the two opposite actions in primary cultured Schwann cells.