Sialidase NEU3 Research Articles

Abstract Tu131: Counteracting Cardiac Ischemia and Reperfusion Injury: the role of Sialidase Neu3

Coronary reperfusion procedures are crucial for restoring blood flow to the heart tissue after an acute myocardial infarction. However, they also lead to ischemia and reperfusion injury (IRI), which exacerbate the damage and promote heart failure. Despite the urgent need for cardioprotective strategies against IRI, none have been clinically implemented, emphasizing the need for a comprehensive understanding of the pathophysiology of IRI. Our research team found that sialidase Neu3, an enzyme responsible for the removal of sialic acid from glycosphingolipids, is modulated during IRI in vivo. Constitutive overexpression of Neu3 in rat cardiomyoblasts was shown to attenuate IRI through activation of the reperfusion injury salvage kinase (RISK) and HIF-1α signaling pathways. To further investigate the role of Neu3 in promoting cardioprotection, in this study we developed an inducible Neu3 overexpression model in human cardiac cells and mice. Inducible upregulation of Neu3 significantly improved cell resistance and reduced oxidative stress in AC16 cells exposed to IRI in vitro. These effects were attributed to Neu3-mediated maintenance of mitochondrial membrane potential, which was impaired in control cells. When looking at the upregulated genes exclusively in cells overexpressing the sialidase Neu3, RNAseq analysis revealed the predominant activation of MAP kinases typical of the RISK pathway. We also generated, for the first time, αMHC-Cre/LSL-Neu3 mice overexpressing Neu3 in an inducible and cardiomyocyte-specific manner. These mice showed no significant differences in cardiac morphology and functionality compared to wild-type animals. However, the Neu3-overexpressing mice exhibited a significant reduction in infarct size and improved cardiac functionality after surgical induction of IRI. These results suggest that Neu3 is a promising target for improving cardioprotection and attenuating the incidence and severity of myocardial infarction.

Artificial and Natural Sweeteners Biased T1R2/T1R3 Taste Receptors Transactivate Glycosylated Receptors on Cancer Cells to Induce Epithelial-Mesenchymal Transition of Metastatic Phenotype.

Understanding the role of biased taste T1R2/T1R3 G protein-coupled receptors (GPCR) agonists on glycosylated receptor signaling may provide insights into the opposing effects mediated by artificial and natural sweeteners, particularly in cancer and metastasis. Sweetener-taste GPCRs can be activated by several active states involving either biased agonism, functional selectivity, or ligand-directed signaling. However, there are increasing arrays of sweetener ligands with different degrees of allosteric biased modulation that can vary dramatically in binding- and signaling-specific manners. Here, emerging evidence proposes the involvement of taste GPCRs in a biased GPCR signaling crosstalk involving matrix metalloproteinase-9 (MMP-9) and neuraminidase-1 (Neu-1) activating glycosylated receptors by modifying sialic acids. The findings revealed that most natural and artificial sweeteners significantly activate Neu-1 sialidase in a dose-dependent fashion in RAW-Blue and PANC-1 cells. To confirm this biased GPCR signaling crosstalk, BIM-23127 (neuromedin B receptor inhibitor, MMP-9i (specific MMP-9 inhibitor), and oseltamivir phosphate (specific Neu-1 inhibitor) significantly block sweetener agonist-induced Neu-1 sialidase activity. To assess the effect of artificial and natural sweeteners on the key survival pathways critical for pancreatic cancer progression, we analyzed the expression of epithelial-mesenchymal markers, CD24, ADLH-1, E-cadherin, and N-cadherin in PANC-1 cells, and assess the cellular migration invasiveness in a scratch wound closure assay, and the tunneling nanotubes (TNTs) in staging the migratory intercellular communication. The artificial and natural sweeteners induced metastatic phenotype of PANC-1 pancreatic cancer cells to promote migratory intercellular communication and invasion. The sweeteners also induced the downstream NFκB activation using the secretory alkaline phosphatase (SEAP) assay. These findings elucidate a novel taste T1R2/T1R3 GPCR functional selectivity of a signaling platform in which sweeteners activate downstream signaling, contributing to tumorigenesis and metastasis via a proposed NFκB-induced epigenetic reprogramming modeling.

AAV-mediated gene therapy for sialidosis

Sialidosis (Mucolipidosis I) is a glycoprotein storage disease, clinically characterized by a spectrum of systemic and neurological phenotypes. The primary cause of the disease is deficiency of the lysosomal sialidase NEU1, resulting in accumulation of sialylated glycoproteins/ oligosaccharides in tissues and body fluids. Neu1–/– mice recapitulate the severe, early-onset forms of the disease, affecting visceral organs, muscles, and the nervous system, with wide-spread lysosomal vacuolization evident in most cell types. Sialidosis is considered an orphan disorder with no therapy currently available. Here, we assessed the therapeutic potential of AAV-mediated gene therapy for the treatment of sialidosis. Neu1–/– mice were co-injected with two scAAV2/8 vectors, expressing human NEU1 and its chaperone PPCA. Treated mice were phenotypically indistinguishable from their WT controls. NEU1 activity was restored to different extent in most tissues, including the brain, heart and muscle, and visceral organs. This resulted in diminished/absent lysosomal vacuolization in multiple cell types and reversal of sialyl-oligosacchariduria. Lastly, normalization of lysosomal exocytosis in the CSF and serum of treated mice, coupled to diminished neuroinflammation, were measures of therapeutic efficacy. These findings point to AAV-mediated gene therapy as a suitable treatment for sialidosis and possibly other diseases, associated with low NEU1 expression.

Functional Selectivity of Cannabinoid Type 1 G Protein-Coupled Receptor Agonists in Transactivating Glycosylated Receptors on Cancer Cells to Induce Epithelial-Mesenchymal Transition Metastatic Phenotype.

Understanding the role of biased G protein-coupled receptor (GPCR) agonism in receptor signaling may provide novel insights into the opposing effects mediated by cannabinoids, particularly in cancer and cancer metastasis. GPCRs can have more than one active state, a phenomenon called either 'biased agonism', 'functional selectivity', or 'ligand-directed signaling'. However, there are increasing arrays of cannabinoid allosteric ligands with different degrees of modulation, called 'biased modulation', that can vary dramatically in a probe- and pathway-specific manner, not from simple differences in orthosteric ligand efficacy or stimulus-response coupling. Here, emerging evidence proposes the involvement of CB1 GPCRs in a novel biased GPCR signaling paradigm involving the crosstalk between neuraminidase-1 (Neu-1) and matrix metalloproteinase-9 (MMP-9) in the activation of glycosylated receptors through the modification of the receptor glycosylation state. The study findings highlighted the role of CB1 agonists AM-404, Aravnil, and Olvanil in significantly inducing Neu-1 sialidase activity in a dose-dependent fashion in RAW-Blue, PANC-1, and SW-620 cells. This approach was further substantiated by findings that the neuromedin B receptor inhibitor, BIM-23127, MMP-9 inhibitor, MMP9i, and Neu-1 inhibitor, oseltamivir phosphate, could specifically block CB1 agonist-induced Neu-1 sialidase activity. Additionally, we found that CB1 receptors exist in a multimeric receptor complex with Neu-1 in naïve, unstimulated RAW-Blue, PANC-1, and SW-620 cells. This complex implies a molecular link that regulates the interaction and signaling mechanism among these molecules present on the cell surface. Moreover, the study results demonstrate that CB1 agonists induce NFκB-dependent secretory alkaline phosphatase (SEAP) activity in influencing the expression of epithelial-mesenchymal markers, E-cadherin, and vimentin in SW-620 cells, albeit the impact on E-cadherin expression is less pronounced compared to vimentin. In essence, this innovative research begins to elucidate an entirely new molecular mechanism involving a GPCR signaling paradigm in which cannabinoids, as epigenetic stimuli, may traverse to influence gene expression and contribute to cancer and cancer metastasis.

A new method for the purification of bioviable NEU1 sialidase for enzyme replacement therapy for sialidosis

A new method for the purification of bioviable NEU1 sialidase for enzyme replacement therapy for sialidosis

Sialidase NEU3 Contributes to the Invasiveness of Bladder Cancer.

Bladder cancer is the 10th most commonly diagnosed cancer worldwide. The current standard treatment for advanced bladder cancer is neoadjuvant cisplatin (NAC)-based chemotherapy followed by cystectomy. However, the response rate to chemotherapy is only 50%, owing to cisplatin resistance, and there is a need for novel therapies. Because the invasiveness of bladder cancer greatly influences patient prognosis, a mechanistic analysis of the invasive function can lead to therapeutic targets. Sialidases, which remove sialic acid residues from the nonreducing ends of sugar chains and catalyze the initial reaction in the degradation of sugar chains, are predicted to be involved in cell invasion and motility. However, the involvement of sialidases in bladder cancer, especially their relationship with the invasive ability, remains unclear. Here, using patient tissues and multiple bladder cancer cell lines, we show that the sialidase NEU3 is highly expressed in bladder cancer. Analysis of NEU3's function using its siRNA-mediated knockdown revealed that NEU3 contributes to bladder cancer invasiveness. Mechanistic analysis showed that NEU3 activates ERK and PI3K signaling. Our results show that NEU3 is involved in the malignancy of bladder cancer, and its suppression may lead to novel treatments for bladder cancer.

Arylsulfatases and neuraminidases modulate engagement of CCR5 by chemokines by removing key electrostatic interactions

The chemokine receptor CCR5 is known to exist in cell surface subpopulations that differ in their capacity to engage ligands. One proposed explanation for this phenomenon is the presence of CCR5 species with different levels of post-translational modifications (PTMs). Tyrosine sulfation and O-glycan sialylation are PTMs that add negative charges to the extracellular domain of CCR5 and make strong contributions to chemokine binding but it is not known whether cellular mechanisms to control their levels exist. In this study we used a combination of sulfation-sensitive and sulfation-insensitive CCR5 ligands to show that the rate of turnover of CCR5 tyrosine sulfation is more rapid than the rate of turnover of the receptor itself. This suggests that the steady state level of CCR5 sulfation is maintained through the combination of tyrosine protein sulfotransferase (TPST), the trans-Golgi network (TGN)-resident ‘source enzyme, and a ‘sink’ activity that removes tyrosine sulfation from CCR5. By measuring the effects on ligand binding of knockdown and overexpression experiments, we provided evidence that non-lysosomal cellular arylsulfatases, particularly ARSG, ARSI and ARSJ, are CCR5 sulfation ‘sink’ enzymes. We also used targeted knockdown and sialylation-sensitive and insensitive chemokines to identify the sialidase NEU3 as a candidate ‘sink’ enzyme for CCR5 O-glycan sialylation. This study provides the first experimental evidence of activity of sulfatase and sialidase ‘sink’ enzymes on CCR5, providing a potential mechanism for cells to control steady-state levels of these PTMs and thereby exert dynamic control over receptor-ligand interactions at the cell surface and during receptor desensitization.

Sialidase NEU3 action on GM1 ganglioside is neuroprotective in GM1 gangliosidosis

GM1 gangliosidosis is a neurodegenerative disorder caused by mutations in the GLB1 gene, which encodes lysosomal β-galactosidase. The enzyme deficiency blocks GM1 ganglioside catabolism, leading to accumulation of GM1 ganglioside and asialo-GM1 ganglioside (GA1 glycolipid) in brain. This disease can present in varying degrees of severity, with the level of residual β-galactosidase activity primarily determining the clinical course. Glb1 null mouse models, which completely lack β-galactosidase expression, exhibit a less severe form of the disease than expected from the comparable deficiency in humans, suggesting a potential species difference in the GM1 ganglioside degradation pathway. We hypothesized this difference may involve the sialidase NEU3, which acts on GM1 ganglioside to produce GA1 glycolipid. To test this hypothesis, we generated Glb1/Neu3 double KO (DKO) mice. These mice had a significantly shorter lifespan, increased neurodegeneration, and more severe ataxia than Glb1 KO mice. Glb1/Neu3 DKO mouse brains exhibited an increased GM1 ganglioside to GA1 glycolipid ratio compared with Glb1 KO mice, indicating that NEU3 mediated GM1 ganglioside to GA1 glycolipid conversion in Glb1 KO mice. The expression of genes associated with neuroinflammation and glial responses were enhanced in Glb1/Neu3 DKO mice compared with Glb1 KO mice. Mouse NEU3 more efficiently converted GM1 ganglioside to GA1 glycolipid than human NEU3 did. Our findings highlight NEU3’s role in ameliorating the consequences of Glb1 deletion in mice, provide insights into NEU3’s differential effects between mice and humans in GM1 gangliosidosis, and offer a potential therapeutic approach for reducing toxic GM1 ganglioside accumulation in GM1 gangliosidosis patients.

Abstract P2131: Sialidase Neu3: A Novel Cardioprotective Target Against Ischemia And Reperfusion Injury

Coronary reperfusion techniques are life-saving approaches to restore blood flow to cardiac tissue after acute myocardial infarction. However, they also lead to what is known as ischemia and reperfusion injury (IRI), which causes additional damage and heart failure. Despite the urgent need for cardioprotective strategies against IRI, none has yet been introduced into clinical practice, suggesting that a more detailed characterization of the molecular mechanisms underlying the pathogenesis of IRI is essential. In this regard, our research group has shown that sialidase Neu3, an enzyme responsible for removing sialic acid from glycosphingolipids, is modulated during IRI in vivo and that its constitutive overexpression in rat cardiomyoblasts is sufficient to counteract the deleterious effects of IRI through activation of reperfusion injury salvage kinase (RISK) and the HIF-1α pathway. Thus, in this study, we developed an inducible model of Neu3 overexpression in human cardiac cells (AC16) and in mice to further elucidate the role of this protein in promoting cardioprotection. Inducible upregulation of Neu3 significantly increased cell resistance and reduced oxidative stress in AC16 exposed to IRI in vitro. These beneficial effects were related to Neu3-mediated maintenance of mitochondrial membrane potential, which was altered in control cells. Moreover, RNAseq data showed that Neu3 activation was associated with upregulation of the cellular responses to stress, whereas, in contrast, the pro-inflammatory signaling pathways of TNF-α and IL-22 were downregulated. We also generated αMHC-Cre/LSL-Neu3 mice for the first time by crossing the tamoxifen-inducible αMHC-Cre mouse with a mouse carrying a floxed-transcriptional STOP sequence upstream of Neu3. These mice were characterized for cardiac morphology and functionality and showed no significant differences compared with wild-type mice. They will undergo surgical induction of IRI to test the beneficial effects of Neu3. Based on our findings, it can be hypothesized that Neu3 plays a significant role in the cardiac response to IRI. Consequently, targeting Neu3 may hold therapeutic promise in increasing cardioprotection and mitigating the incidence and severity of myocardial infarction.

Inhibitors of the Sialidase NEU3 as Potential Therapeutics for Fibrosis.

Fibrosing diseases are a major medical problem, and are associated with more deaths per year than cancer in the US. Sialidases are enzymes that remove the sugar sialic acid from glycoconjugates. In this review, we describe efforts to inhibit fibrosis by inhibiting sialidases, and describe the following rationale for considering sialidases to be a potential target to inhibit fibrosis. First, sialidases are upregulated in fibrotic lesions in humans and in a mouse model of pulmonary fibrosis. Second, the extracellular sialidase NEU3 appears to be both necessary and sufficient for pulmonary fibrosis in mice. Third, there exist at least three mechanistic ways in which NEU3 potentiates fibrosis, with two of them being positive feedback loops where a profibrotic cytokine upregulates NEU3, and the upregulated NEU3 then upregulates the profibrotic cytokine. Fourth, a variety of NEU3 inhibitors block pulmonary fibrosis in a mouse model. Finally, the high sialidase levels in a fibrotic lesion cause an easily observed desialylation of serum proteins, and in a mouse model, sialidase inhibitors that stop fibrosis reverse the serum protein desialylation. This then indicates that serum protein sialylation is a potential surrogate biomarker for the effect of sialidase inhibitors, which would facilitate clinical trials to test the exciting possibility that sialidase inhibitors could be used as therapeutics for fibrosis.

Altered expression of glycobiology-related genes in Parkinson's disease brain.

The precise mechanisms initiating and perpetuating the cellular degeneration in Parkinson's disease (PD) remain unclear. There is decreased expression of the main brain gangliosides, and GM1 ganglioside in particular, in the PD brain along with decreased expression of the genes coding for the glycosyltranferase and the sialyltransferase responsible for the synthesis of these brain gangliosides. However, potentially important pathogenic mechanisms contributing to the neurodegeneration in PD may also include altered levels of expression of genes involved in glycosylation, sialylation and sphingolipid synthesis and metabolism. Although various studies have described pathological lipid and glycolipid changes in PD brain, there have been limited studies of expression of glycobiology-related genes in PD brain. The current study was performed as an initial attempt to gain new information regarding potential changes in glycoprotein and glycolipid-related genes in PD by investigating the gene expression status for select glycosyltransferases, sialyltransferases, sialidases, sphingosine kinases, and lysosomal enzymes in the substantia nigra and putamen from patients with PD and neurologically normal controls. Results showed altered expression of glycosyltransferase genes (B3GALT2 and B4GALT1) potentially involved in microglial activation and neuroinflammation, sphingosine-1-phosphate (S1P) modulators (SPHK1, SPHK2, and SGPL1) involved in sphingolipid synthesis and metabolism, polysialyltransferase genes (ST8SIA2 and ST8SIA4) that encode enzymes responsible for polysialic acid (polySia) biosynthesis, and the sialidase NEU4, expression of which has been linked to the clearance of storage materials from lysosomes. The data presented here underscore the complexity of the glycolipid/sphingolipid dysregulation in the PD brain and continued and expanded study of these processes may not only provide a greater understanding of the complex roles of aberrant glycosylation sialylation, and sphingolipid synthesis/metabolism in the pathophysiology of PD but may identify potential druggable targets for PD therapeutics.

Changes in lung sialidases in male and female mice after bleomycin aspiration

ABSTRACT Aim of the study: Sialidases, also called neuraminidases, are enzymes that cleave terminal sialic acids from glycoconjugates. In humans and mice, lung fibrosis is associated with desialylation of glycoconjugates and upregulation of sialidases. There are four mammalian sialidases, and it is unclear when the four mammalian sialidases are elevated over the course of inflammatory and fibrotic responses, whether tissue resident and inflammatory cells express different sialidases, and if sialidases are differentially expressed in male and females. Materials and Methods: To determine the time course of sialidase expression and the identity of sialidase expressing cells, we used the bleomycin model of pulmonary fibrosis in mice to examine levels of sialidases during inflammation (days 3 − 10) and fibrosis (days 10 − 21). Results: Bleomycin aspiration increased sialidase NEU1 at days 14 and 21 in male mice and day 10 in female mice. NEU2 levels increased at day 7 in male and day 10 in female mice. NEU3 appears to have a biphasic response in male mice with increased levels at day 7 and then at days 14 and 21, whereas in female mice NEU3 levels increased over 21 days. In control mice, the sialidases were mainly expressed by EpCAM positive epithelial cells, but after bleomycin, epithelial cells, CD45 positive immune cells, and alveolar cells expressed NEU1, NEU2, and NEU3. Sialidase expression was higher in male compared to female mice. There was little expression of NEU4 in murine lung tissue. Conclusions: These results suggest that sialidases are dynamically expressed following bleomycin, that sialidases are differentially expressed in male and females, and that of the four sialidases only NEU3 upregulation is associated with fibrosis in both male and female mice.

Haploinsufficiency of the lysosomal sialidase NEU1 results in a model of pleomorphic rhabdomyosarcoma in mice

Rhabdomyosarcoma, the most common pediatric sarcoma, has no effective treatment for the pleomorphic subtype. Still, what triggers transformation into this aggressive phenotype remains poorly understood. Here we used Ptch1+/−/ETV7TG/+/− mice with enhanced incidence of rhabdomyosarcoma to generate a model of pleomorphic rhabdomyosarcoma driven by haploinsufficiency of the lysosomal sialidase neuraminidase 1. These tumors share mostly features of embryonal and some of alveolar rhabdomyosarcoma. Mechanistically, we show that the transforming pathway is increased lysosomal exocytosis downstream of reduced neuraminidase 1, exemplified by the redistribution of the lysosomal associated membrane protein 1 at the plasma membrane of tumor and stromal cells. Here we exploit this unique feature for single cell analysis and define heterogeneous populations of exocytic, only partially differentiated cells that force tumors to pleomorphism and promote a fibrotic microenvironment. These data together with the identification of an adipogenic signature shared by human rhabdomyosarcoma, and likely fueling the tumor’s metabolism, make this model of pleomorphic rhabdomyosarcoma ideal for diagnostic and therapeutic studies.

Abstract P1040: The Protective Effects Of Sialidase Neu3 Against Cardiac Ischemia And Reperfusion Injury

The salvage of myocardium after acute myocardial infarction (AMI) can only be achieved by timely reperfusion. This is life-saving, however it may also lead to additional damage in the form of ischemia and reperfusion injury (IRI). Protecting cardiac tissue from IRI remains one of the greatest unmet clinical needs in cardiology. Therefore, a better understanding of IRI pathophysiology is necessary. There has been increasing recognition that the activation of specific molecular mechanisms, including the Reperfusion Injury Salvage Kinase (RISK) pathway and HIF-1α contributes to cardioprotection against IRI. Along this line, we previously reported that sialidase Neu3, which removes sialic acid from glycosphingolipids, controls HIF-1α activation via a prolyl hydroxylase-independent pathway. In fact, we found that Neu3 was up-regulated under chronic hypoxia in cyanotic congenital cardiac patients and its overexpression increased muscle cells’ resistance to hypoxic stress by activating the RISK pathway. In light of these premises, the goal of this study was to determine Neu3's involvement in the cardiac response to IRI and establish whether its inducible activation could promote cardioprotection. An IRI model in mice, obtained by temporarily blocking the LAD coronary artery, showed that Neu3 is modulated during this process. Notably, Neu3 showed progressive downregulation during the ischemic phase followed by its reactivation during reperfusion. These results were similar to the Neu3 modulation we observed in human cardiac cells (AC16) exposed to an IRI model in vitro . The overexpression of Neu3 during ischemia had beneficial effects both in terms of cell proliferation and reduction of oxidative stress after reperfusion. We found that Neu3 promotes the activation of glycolytic enzymes during the ischemic phase as well as the maintenance of the mitochondrial membrane potential, suggesting that the Neu3-overexpressing human cardiomyocyte undergoes more aerobic metabolism even in oxygen-deficient environments. In conclusion, these results support a role for Neu3 in cardioprotection against IRI, suggesting that it may be a useful therapeutic target for improving the recovery of patients who have undergone acute myocardial infarction.

The extracellular sialidase NEU3 primes neutrophils.

Some extracellular glycoconjugates have sialic acid as the terminal sugar, and sialidases are enzymes that remove this sugar. Mammals have 4 sialidases and can be elevated in inflammation and fibrosis. In this report, we show that incubation of human neutrophils with the extracellular human sialidase NEU3, but not NEU1, NEU2 or NEU4, induces human male and female neutrophils to change from a round to a more amoeboid morphology, causes the primed human neutrophil markers CD11b, CD18, and CD66a to localize to the cell cortex, and decreases the localization of the unprimed human neutrophil markers CD43 and CD62-L at the cell cortex. NEU3, but not the other 3 sialidases, also causes human male and female neutrophils to increase their F-actin content. Human neutrophils treated with NEU3 show a decrease in cortical levels of Sambucus nigra lectin staining and an increase in cortical levels of peanut agglutinin staining, indicating a NEU3-induced desialylation. The inhibition of NEU3 by the NEU3 inhibitor 2-acetylpyridine attenuated the NEU3 effect on neutrophil morphology, indicating that the effect of NEU3 is dependent on its enzymatic activity. Together, these results indicate that NEU3 can prime human male and female neutrophils, and that NEU3 is a potential regulator of inflammation.

Neu1 deficiency increases the susceptibility of zebrafish to Edwardsiella piscicida infection via lysosomal dysfunction

Neu1 is a lysosomal glycosidase that catalyzes the removal of sialic acids from glycoconjugates. Although Neu1 sialidase is highly conserved among vertebrates, the role of fish Neu1 is not fully understood because of its unique aquatic living situation. Compared to land animals, fish have a higher chance of bacterial infection, and to understand the role of fish Neu1, the susceptibility of Neu1 knockout zebrafish (Neu1-KO) was evaluated using Edwardsiella piscicida, a fish pathogen. Neu1-KO larvae showed high susceptibility to E. piscicida, despite the activation of macrophages, and presented increased lysosomal signals induced by the accumulation of Sia α2-3 linked oligosaccharides. The accumulation coincided with the signal of the macrophage marker, suggesting that the dysfunction of lysosomes in macrophages would result in a high susceptibility of Neu1-KO to E. piscicida. Chloroquine, an inhibitor of lysosomal degradation, induced high mortality of wild type zebrafish with E. piscicida infection accompanied by increased lysosomal accumulation, similar to Neu1-KO zebrafish. This study revealed that Neu1 sialidase plays a crucial role in the lysosomal degradation of macrophages with a bacterial infection.

Correlation Between Sialidase NEU1 mRNA Expression Changes in Autism Spectrum Disorder.

Abnormal alterations in enzymes functioned in sialic acid modifications may be associated with ASD. In order to study the differences in peripheral blood sialidase (neuraminidase 1; NEU1) mRNA expression between autism spectrum disorder (ASD) children and healthy control, and to examine the correlation between NEU1 mRNA expression and the main behavioral phenotypes in children with ASD, we performed RT-qPCR to measure NEU1 mRNA expression in peripheral blood of 42 children with ASD and 42 healthy controls. In addition, we used the Autism Diagnostic Observation Schedule, Second Edition (ADOS-2) to measure and evaluate the behavioral phenotypes of children with ASD. Our results showed that NEU1 mRNA in the ASD group was significantly higher than in the control group (P < 0.0001). In addition, the ADOS-2 diagnostic scores of 42 children with ASD were correlated with their NEU1 mRNA expression results (R = 0.344, P = 0.0257). Moreover, in general, NEU1 mRNA expression was also positively correlated with the Social Affect (SA) of ADOS-2 (R = 0.3598, P = 0.0193) but not with the Restricted and Repetitive Behavior (RRB) (R = 0.15, P = 0.3432). Our results indicated that sialidase NEU1 mRNA was significantly increased in children with ASD, and its expression was correlated with the SA of children with ASD, which suggested that sialidase NEU1 may affect the SA of ASD. Our data highlighted the potential of NEU1 expression change may play an important role in ASD disease and lay the foundation for further studies on the relationship between NEU1 and ASD.

Sialidase NEU3 and its pathological significance.

Sialidases (EC 3.2.1.18, also called neuraminidases) catalyze the removal of α-glycosidically linked sialic acid residues from glycoproteins and glycolipids; this is the initial step in the degradation of these glycoconjugates. Sialidases of mammalian origin have been implicated in not only lysosomal catabolism but also the modulation of functional molecules involved in many biological processes. To date, four types of mammalian sialidases have been cloned and designated as Neu1, Neu2, Neu3 and Neu4. These sialidases differ in their subcellular localization and enzymatic properties, as well as their chromosomal localization, and they are expressed in a tissue-specific manner. Among the sialidases, the plasma membrane-associated sialidase Neu3 appears to play particular roles in controlling transmembrane signaling through the modulation of gangliosides, and its aberrant expression is closely related to various pathogeneses, including that of cancer. Interestingly, the human orthologue NEU3 acts in two ways, catalytic hydrolysis of gangliosides and protein interactions with other signaling molecules. Aberrant NEU3 expression can induce various pathological conditions. This review briefly summarizes recent studies, focusing on the involvement of NEU3 in various pathological phenomena.

Selective histone methyltransferase G9a inhibition reduces metastatic development of Ewing sarcoma through the epigenetic regulation of NEU1

Ewing sarcoma (EWS) is an aggressive bone and soft tissue tumor with high susceptibility to metastasize. The underlying molecular mechanisms leading to EWS metastases remain poorly understood. Epigenetic changes have been implicated in EWS tumor growth and progression. Linking epigenetics and metastases may provide insight into novel molecular targets in EWS and improve its treatment. Here, we evaluated the effects of a selective G9a histone methyltransferase inhibitor (BIX01294) on EWS metastatic process. Our results showed that overexpression of G9a in tumors from EWS patients correlates with poor prognosis. Moreover, we observe a significantly higher expression of G9a in metastatic EWS tumor as compared to either primary or recurrent tumor. Using functional assays, we demonstrate that pharmacological G9a inhibition using BIX01294 disrupts several metastatic steps in vitro, such as migration, invasion, adhesion, colony formation and vasculogenic mimicry. Moreover, BIX01294 reduces tumor growth and metastases in two spontaneous metastases mouse models. We further identified the sialidase NEU1 as a direct target and effector of G9a in the metastatic process in EWS. NEU1 overexpression impairs migration, invasion and clonogenic capacity of EWS cell lines. Overall, G9a inhibition impairs metastases in vitro and in vivo through the overexpression of NEU1. G9a has strong potential as a prognostic marker and may be a promising therapeutic target for EWS patients.

Critical Involvement of CD44 in T Helper Type 2 Cell-Mediated Eosinophilic Airway Inflammation in a Mouse Model of Acute Asthma.

Interactions between CD44 and hyaluronan (HA) are crucial for recruiting leukocytes to inflamed tissues. This review summarizes findings from our studies of the roles of CD44-HA interactions in leukocyte trafficking, with a particular focus on airway T helper type 2 (Th2) cells in mouse models of acute asthma. In a mite allergen-induced model of acute asthma, intraperitoneal injection of anti-CD44 monoclonal antibodies blocked lymphocytes and eosinophils from accumulating in the lung, and suppressed both the antigen-induced increase in Th2 cytokines in the bronchoalveolar lavage fluid (BALF) and airway hyperresponsiveness (AHR). CD44 deficiency was associated with decreased mite allergen-induced Th2 cell-mediated airway inflammation and AHR in sensitized mice. Asthmatic responses to antigen-sensitized splenic CD4+ T cells transferred from CD44-deficient mice were weaker than in wild-type mice. Administration of anti-CD44 monoclonal antibodies preferentially suppressed the airway accumulation of antigen-specific Th2 cells induced by antigen challenge, without affecting Th1 and Th17 cells. Increased HA-binding ability of CD44 and expression of Neu1 sialidase were observed on antigen-specific Th2 cells compared with antigen-specific Th1 and Th17 cells. Finally, in a mouse model of acute asthma, neuraminidase 1-deficient SM/J mice exhibited a lower Th2 cytokine concentration and a lower absolute Th2 cell number in the BALF, as well as an attenuated AHR. Our findings indicate that CD44 critically contributes to the antigen challenge-induced airway accumulation of antigen-specific Th2 cells, without affecting Th1 and Th17 cells, in mice. Furthermore, neuraminidase 1 activity is necessary for the interaction between HA and CD44, and Th2 cell-mediated airway inflammation.