Neuronal differentiation-dependent expression of the disialic acid epitope on CD166 and its involvement in neurite formation in Neuro2A cells

Possible Involvement of DNA Methylation and Protective Effect of Zebularine on Neuronal Cell Death after Glutamate Excitotoxity

Neuronal cell death after cerebral ischemia consists various steps including glutamate excitotoxity. Excessive Ca²⁺ influx through the N-methyl-D-aspartate (NMDA) receptor, which is one of the ionotropic glutamate receptors, plays a central role in neuronal cell death after cerebral ischemia. We previously reported that DNA methylation is transiently increased in neurons during ischemic injury and that this aberrant DNA methylation is accompanied by neuronal cell death. Therefore, we performed the present experiments on glutamate excitotoxicity to gain further insight into DNA methylation involvement in the neuronal cell death. We demonstrated that knockdown of DNA methyltransferase (DNMT)1, DNMT3a, or DNMT3b gene in Neuro2a cells was performed to examine which DNMTs were more important for neuronal cell death after glutamate excitotoxicity. Although we confirmed a decrease in the levels of the target DNMT protein after small interfering RNA (siRNA) transfection, the Neuro2a cells were not protected from injury by transfection with siRNA for each DNMT. We next revealed that the pharmacological inhibitor of DNMTs protected against glutamate excitotoxicity in Neuro2a cells and also in primary cultured cortical neurons. This protective effect was associated with a decrease in the number of 5-methylcytosine (5 mC)-positive cells under glutamate excitotoxicity. In addition, the increased level of cleaved caspase-3 was also reduced by a DNMT inhibitor. Our results suggest the possibility that at least 2 or all DNMTs functionally would cooperate to activate DNA methylation after glutamate excitotoxicity and that inhibition of DNA methylation in neurons after cerebral ischemia might become a strategy to reduce the neuronal injury.

Bioinformatics Analyses Identify the Therapeutic Potential of ST8SIA6 for Colon Cancer

Sialylation of glycoproteins is modified by distinct sialyltransferases such as ST3Gal, ST6Gal, ST6GalNAc, or ST8SIA with α2,3-, α2,6-, or α2,8-linkages. Alteration of these sialyltransferases causing aberrant sialylation is associated with the progression of colon cancer. However, among the ST8- sialyltransferases, the role of ST8SIA6 in colon cancer remains poorly understood. In this study, we explored the involvement of ST8SIA6 in colon cancer using multiple gene databases. The relationship between ST8SIA6 expression and tumor stages/grades was investigated by UALCAN analysis, and Kaplan–Meier Plotter analysis was used to analyze the expression of ST8SIA6 on the survival outcome of colon cancer patients. Moreover, the biological functions of ST8SIA6 in colon cancer were explored using LinkedOmics and cancer cell metabolism gene DB. Finally, TIMER and TISMO analyses were used to delineate ST8SIA6 levels in tumor immunity and immunotherapy responses, respectively. ST8SIA6 downregulation was associated with an advanced stage and poorly differentiated grade; however, ST8SIA6 expression did not affect the survival outcomes in patients with colon cancer. Gene ontology analysis suggested that ST8SIA6 participates in cell surface adhesion, angiogenesis, and membrane vesicle trafficking. In addition, ST8SIA6 levels affected immunocyte infiltration and immunotherapy responses in colon cancer. Collectively, these results suggest that ST8SIA6 may serve as a novel therapeutic target towards personalized medicine for colon cancer.

Modulation of calcium signaling depends on the oligosaccharide of GM1 in Neuro2a mouse neuroblastoma cells

Recently, we demonstrated that the oligosaccharide portion of ganglioside GM1 is responsible, via direct interaction and activation of the TrkA pathway, for the ability of GM1 to promote neuritogenesis and to confer neuroprotection in Neuro2a mouse neuroblastoma cells. Recalling the knowledge that ganglioside GM1 modulates calcium channels activity, thus regulating the cytosolic calcium concentration necessary for neuronal functions, we investigated if the GM1-oligosaccharide would be able to overlap the GM1 properties in the regulation of calcium signaling, excluding a specific role played by the ceramide moiety inserted into the external layer of plasma membrane. We observed, by calcium imaging, that GM1-oligosaccharide administration to undifferentiated Neuro2a cells resulted in an increased calcium influx, which turned out to be mediated by the activation of TrkA receptor. The biochemical analysis demonstrated that PLCγ and PKC activation follows the TrkA stimulation by GM1-oligosaccharide, leading to the opening of calcium channels both on the plasma membrane and on intracellular storages, as confirmed by calcium imaging experiments performed with IP3 receptor inhibitor. Subsequently, we found that neurite elongation in Neuro2a cells was blocked by subtoxic administration of extracellular and intracellular calcium chelators, suggesting that the increase of intracellular calcium is responsible of GM1-oligosaccharide mediated differentiation. These results suggest that GM1-oligosaccharide is responsible for the regulation of calcium signaling and homeostasis at the base of the neuronal functions mediated by plasma membrane GM1.

Depolarization-dependent Induction of Site-specific Changes in Sialylation on N-linked Glycoproteins in Rat Nerve Terminals

Synaptic transmission leading to release of neurotransmitters in the nervous system is a fast and highly dynamic process. Previously, protein interaction and phosphorylation have been thought to be the main regulators of synaptic transmission. Here we show that sialylation of N-linked glycosylation is a novel potential modulator of neurotransmitter release mechanisms by investigating depolarization-dependent changes of formerly sialylated N-linked glycopeptides. We suggest that negatively charged sialic acids can be modulated, similarly to phosphorylation, by the action of sialyltransferases and sialidases thereby changing local structure and function of membrane glycoproteins. We characterized site-specific alteration in sialylation on N-linked glycoproteins in isolated rat nerve terminals after brief depolarization using quantitative sialiomics. We identified 1965 formerly sialylated N-linked glycosites in synaptic proteins and found that the abundances of 430 glycosites changed after 5 s depolarization. We observed changes on essential synaptic proteins such as synaptic vesicle proteins, ion channels and transporters, neurotransmitter receptors and cell adhesion molecules. This study is to our knowledge the first to describe ultra-fast site-specific modulation of the sialiome after brief stimulation of a biological system.

Vaccine-Induced Adverse Effects in Cultured Neuroblastoma 2A (N2A) Cells Duplicate Toxicity of Serum from Patients with Gulf War Illness (GWI) and Are Prevented in the Presence of Specific Anti-Vaccine Antibodies

Gulf War illness (GWI) is a chronic disease of unknown etiology affecting over 200,000 veterans with symptoms including neurocognitive problems. We previously demonstrated GWI serum toxicity on neural cell cultures manifested by compromised neural network function, decreased cell spreading, and enhanced cell apoptosis. These patients lacked six human leukocyte antigen (HLA) class II alleles, resulting in an inability to form antibodies. Therefore, we hypothesized that GWI patients have vaccine-derived, persistent pathogens, which contribute to the development of the disease. Here, we examined whether individual vaccines were toxic in cultured N2A cells. Moreover, we used antibodies against each of the 20 vaccines administered to Gulf War (GW) veterans, to examine the effects of these antibodies on cell spreading and apoptosis in N2A cells. Antibodies against cholera toxin, hepatitis B, hemagglutinin H1N1, H3N2, and B from influenza A and B strains, measles, and Salmonella Typhi polysaccharide Vi had a remarkable protective effect on both cell spreading and apoptosis, whereas none of the other antibodies administered to GW veterans had an effect. The in vitro observed adverse effects of GWI serum may be due in part to vaccine-derived pathogens, antibodies against which had a protective effect in N2A cell cultures.

Dihydrolipoic Acid-Gold Nanoclusters Regulate Microglial Polarization and Have the Potential To Alter Neurogenesis

Microglia-mediated neuroinflammation is one of the most significant features in a variety of central nervous system (CNS) disorders such as traumatic brain injury, stroke, and many neurodegenerative diseases. Microglia become polarized upon stimulation. The two extremes of the polarization are the neuron-destructive proinflammatory M1-like and the neuron-regenerative M2-like phenotypes. Thus, manipulating microglial polarization toward the M2 phenotype is a promising therapeutic approach for CNS repair and regeneration. It has been reported that nanoparticles are potential tools for regulating microglial polarization. Gold nanoclusters (AuNCs) could penetrate the blood-brain barrier and have neuroprotective effects, suggesting the possibility of utilizing AuNCs to regulate microglial polarization and improve neuronal regeneration in CNS. In the current study, AuNCs functionalized with dihydrolipoic acid (DHLA-AuNCs), an antioxidant with demonstrated neuroprotective roles, were prepared, and their effects on polarization of a microglial cell line (BV2) were examined. DHLA-AuNCs effectively suppressed proinflammatory processes in BV2 cells by inducing polarization toward the M2-like phenotype. This was associated with a decrease in reactive oxygen species and reduced NF-kB signaling and an improvement in cell survival coupled with enhanced autophagy and inhibited apoptosis. Conditioned medium from DHLA-AuNC-treated BV2 cells was able to enhance neurogenesis in both the neuronal cell line N2a and in an ex vivo brain slice stroke model. The direct treatment of brain slices with DHLA-AuNCs also ameliorated stroke-related tissue injury and reduced astrocyte activation (astrogliosis). This study suggests that by regulating neuroinflammation to improve neuronal regeneration, DHLA-AuNCs could be a potential therapeutic agent in CNS disorders.

Advanced Technologies in Sialic Acid and Sialoglycoconjugate Analysis

Although the structural diversity of sialic acid (Sia) is rapidly expanding, understanding of its biological significance has lagged behind. Advanced technologies to detect and probe diverse structures of Sia are absolutely necessary not only to understand further biological significance but also to pursue medicinal and industrial applications. Here we describe analytical methods for detection of Sia that have recently been developed or improved, with a special focus on 9-O-acetylated N-acetylneuraminic acid (Neu5,9Ac), N-glycolylneuraminic acid (Neu5Gc), deaminoneuraminic acid (Kdn), O-sulfated Sia (SiaS), and di-, oligo-, and polysialic acid (diSia/oligoSia/polySia) in glycoproteins and glycolipids. Much more attention has been paid to these Sia and sialoglycoconjugates during the last decade, in terms of regulation of the immune system, neural development and function, tumorigenesis, and aging.

Profiling of glycan receptors for minute virus of mice in permissive cell lines towards understanding the mechanism of cell recognition

The recognition of sialic acids by two strains of minute virus of mice (MVM), MVMp (prototype) and MVMi (immunosuppressive), is an essential requirement for successful infection. To understand the potential for recognition of different modifications of sialic acid by MVM, three types of capsids, virus-like particles, wild type empty (no DNA) capsids, and DNA packaged virions, were screened on a sialylated glycan microarray (SGM). Both viruses demonstrated a preference for binding to 9-O-methylated sialic acid derivatives, while MVMp showed additional binding to 9-O-acetylated and 9-O-lactoylated sialic acid derivatives, indicating recognition differences. The glycans recognized contained a type-2 Galβ1-4GlcNAc motif (Neu5Acα2-3Galβ1-4GlcNAc or 3′SIA-LN) and were biantennary complex-type N-glycans with the exception of one. To correlate the recognition of the 3′SIA-LN glycan motif as well as the biantennary structures to their natural expression in cell lines permissive for MVMp, MVMi, or both strains, the N- and O-glycans, and polar glycolipids present in three cell lines used for in vitro studies, A9 fibroblasts, EL4 T lymphocytes, and the SV40 transformed NB324K cells, were analyzed by MALDI-TOF/TOF mass spectrometry. The cells showed an abundance of the sialylated glycan motifs recognized by the viruses in the SGM and previous glycan microarrays supporting their role in cellular recognition by MVM. Significantly, the NB324K showed fucosylation at the non-reducing end of their biantennary glycans, suggesting that recognition of these cells is possibly mediated by the Lewis X motif as in 3′SIA-Le^X identified in a previous glycan microarray screen.

Comparative analysis of some aspects of mitochondrial metabolism in differentiated and undifferentiated neuroblastoma cells

The aim of the present study is to clarify some aspects of the mechanisms of regulation of mitochondrial metabolism in neuroblastoma (NB) cells. Experiments were performed on murine Neuro-2a (N2a) cell line, and the same cells differentiated by all-trans-retinoic acid (dN2a) served as in vitro model of normal neurons. Oxygraphy and Metabolic Control Analysis (MCA) were applied to characterize the function of mitochondrial oxidative phosphorylation (OXPHOS) in NB cells. Flux control coefficients (FCCs) for components of the OXPHOS system were determined using titration studies with specific non-competitive inhibitors in the presence of exogenously added ADP. Respiration rates of undifferentiated Neuro-2a cells (uN2a) and the FCC of Complex-II in these cells were found to be considerably lower than those in dN2a cells. Our results show that NB is not an exclusively glycolytic tumor and could produce a considerable part of ATP via OXPHOS. Two important enzymes - hexokinase-2 and adenylate kinase-2 can play a role in the generation of ATP in NB cells. MCA has shown that in uN2a cells the key sites in the regulation of OXPHOS are complexes I, II and IV, whereas in dN2a cells complexes II and IV. Results obtained for the phosphate and adenine nucleotide carriers showed that in dN2a cells these carriers exerted lower control over the OXPHOS than in undifferentiated cells. The sum of FCCs for both types of NB cells was found to exceed significantly that for normal cells suggesting that in these cells the respiratory chain was somehow reorganized or assembled into large supercomplexes.

Inhibition of brain ST8SiaIII sialyltransferase leads to impairment of procedural memory in mice

Several glycoproteins in mammalian brains contain α2,8-linked disialic acid residues. We previously showed a constant expression of disialic acid (DiSia) in the hippocampus, olfactory bulb and cortex, and a gradual decrease of expression in the cerebellum from neonatal to senile mice. Previous publications indicate that neurite extension of neuroblastoma-derived Neuro2A cells is inhibited in the presence of DiSia antibody. Based on this, we treated Neuro2A cell cultures with RNA interference for ST8SiaIII mRNA, the enzyme responsible for DiSia formation. We observed that neurite extension was inhibited by this treatment. Taking this evidence into consideration and the relationship of the cerebellum with learning and memory, we studied the role of DiSia expression in a learning task. Through delivery of pST8SiaIII into the brains of C57BL/6 neonatal mice, we inhibited the expression of ST8SiaIII. ST8SiaIII mRNA and protein expressions were analyzed by real-time PCR and western blot, respectively. In this work, we showed that pST8SiaIII-treated mice presented a significantly reduced level of ST8SiaIII mRNA in the cerebellum (p<0.01) in comparison to control mice at 8 days after treatment. It is also noted that these levels returned to baseline values in the adulthood. Then, we evaluated behavioural performance in the T-Maze, a learning task that estimates procedural memory. At all ages, pST8SiaIII-treated mice showed a lower performance in the test session, being most evident at older ages (p<0.001). Taken all together, we conclude that gene expression of ST8SiaIII is necessary for some cognitive tasks at early postnatal ages, since reduced levels impaired procedural memory in adult mice.

Plasma membrane proteomics of tumor spheres identify CD166 as a novel marker for cancer stem-like cells in head and neck squamous cell carcinoma

Patients with advanced head and neck squamous cell carcinoma (HNSCC) have a poor prognosis with the currently available therapy, and tumor recurrence is frequently observed. The discovery of specific membrane-associated cancer stem cell (CSC) markers is crucial for the development of novel therapeutic strategies to target these CSCs. To address this issue, we established sphere cultures to enrich CSCs and used them for plasma membrane proteomics to identify specific membrane signatures of the HNSCC spheres. Of a dataset that included a total of 376 identified proteins, 200 were bona fide membrane proteins. Among them, 123 proteins were at least 1.5-fold up- or down-regulated in the spheres relative to the adherent cultures. These proteins included cell adhesion molecules, receptors, and transporter proteins. Some of them play key roles in wnt, integrin, and TGFβ signaling pathways. When we compared our dataset with two published hESC membrane protein signatures, we found 18 proteins common to all three of the databases. CD166 and CD44 were two such proteins. Interestingly, the expression of CD166, rather than that of the well-established HNSCC CSC marker CD44, was significantly related to the malignant behavior of HNSCC. Relative to CD166(low) HNSCC cells, CD166(high) HNSCC cells had a greater sphere-formation ability in vitro and tumor formation ability in vivo. Patients whose tumors expressed high levels of CD166 had a significantly poorer clinical outcome than those whose tumors expressed low levels of CD166 (cohort 1: 96 cases, p = 0.040), whereas the level of CD44 expression had only a marginal influence on the clinical outcome of patients with HNSCC (p = 0.078). The level of CD166 expression in HNSCC tumors was also associated with the tumor recurrence rate (cohort 2: 104 cases, p = 0.016). This study demonstrates that CD166 is a valuable cell surface marker for the enrichment of HNSCC stem cells and that plasma membrane proteomics is a promising biological tool for investigating the membrane proteins of CSCs.

Platelets recognize brain-specific glycolipid structures, respond to neurovascular damage and promote neuroinflammation

Platelets respond to vascular damage and contribute to inflammation, but their role in the neurodegenerative diseases is unknown. We found that the systemic administration of brain lipid rafts induced a massive platelet activation and degranulation resulting in a life-threatening anaphylactic-like response in mice. Platelets were engaged by the sialated glycosphingolipids (gangliosides) integrated in the rigid structures of astroglial and neuronal lipid rafts. The brain-abundant gangliosides GT1b and GQ1b were specifically recognized by the platelets and this recognition involved multiple receptors with P-selectin (CD62P) playing the central role. During the neuroinflammation, platelets accumulated in the central nervous system parenchyma, acquired an activated phenotype and secreted proinflammatory factors, thereby triggering immune response cascades. This study determines a new role of platelets which directly recognize a neuronal damage and communicate with the cells of the immune system in the pathogenesis of neurodegenerative diseases.

Advanced mass spectrometry and chemical analyses reveal the presence of terminal disialyl motif on mouse B-cell glycoproteins

The occurrence of a terminal disialyl motif on mammalian O-glycans is increasingly being identified through recent mass spectrometry (MS)-based glycomic profiling. In most cases, it is carried on simple core 1 structures in which both the galactose and N-acetyl galactosamine can be disialylated. In contrast, a disialyl motif on N-glycans is less readily revealed by MS mapping, since additional MS/MS analysis is required to determine the distribution of the various sialic acids on typically multisialylated complex type N-glycans. In our MS-based glycomic screening, we found that a mouse B lymphoma cell line, BCL1, ranks among those that have the highest amount of disialyl motif on its O-glycans, including those carried on CD45. More intriguingly, detailed chemical and MS/MS analyses unambiguously showed that the Neu5Gcα2-8Neu5Gc disialyl motif is also present on the N-glycans and that it can be carried on the termini of polylactosaminoglycan chains, which can be further sulfated on the proximal GlcNAc, occurring alongside other monosialylated sulfated LacNAc termini. Upon silencing the expression of mouse α2,8-sialyltransferase VI (ST8Sia VI), the overall disialyl content decreases significantly, but more so for that on the N-glycans than the O-glycans. ST8Sia VI was further shown to be the most significantly upregulated ST8Sia during plasma cell differentiation, which coincides with increasing content of the disialyl motif. Increasing terminal disialylation without leading to polysialylation may thus have important biological consequences awaiting further investigation. Likewise, the expression of mono- and disialylated sulfated LacNAc may constitute novel recognition codes modulating B-cell activation and differentiation.

HMMC-1, a human monoclonal antibody to fucosylated core 1 O-glycan, suppresses growth of uterine endometrial cancer cells

HMMC-1 is a human monoclonal antibody that reacts with a fucosylated and extended core 1 O-glycan, Fucα1-2Galβ1-4GlcNAcβ1-3Galβ1-3GalNAc-Ser/Thr, as an epitope. In the present study, we examined the effects of HMMC-1 on cell proliferation of two human uterine endometrial cancer cell lines, HEC8 and HEC9, to investigate the role of glycoproteins bearing the HMMC-1 epitope in cancer progression. HEC9 cells expressed high levels of the HMMC-1 epitope, but HMMC-1 reactivity was hardly detected in HEC8 cells. In a mouse model of lymph node metastasis using orthotopic implantation, HEC8 and HEC9 showed low (10%) and high (80%) metastatic potency, respectively. Growth of HEC9, but not HEC8, was remarkably inhibited by addition of HMMC-1 to the culture medium. Cell cycle analysis and expression analysis showed that HMMC-1 treatment increased the G(1) phase population of HEC9 cells and induced cyclin-dependent kinase inhibitors p16 and p21. Two glycoproteins, 97 and 137 kDa, with a strong reactivity to HMMC-1 were purified, and the 97-kDa glycoprotein was identified as CD166, an immunoglobulin superfamily cell adhesion molecule assumed to be involved in cancer metastasis. CD166 gene-silencing dramatically reduced HMMC-1 epitope expression and growth in HEC9 cells, indicating that CD166 is the primary glycoprotein presenting the HMMC-1 epitope in HEC9 cells. Collectively, HMMC-1 might arrest the cell cycle in the G(1) phase by binding to O-glycans on the CD166 expressed in HEC9 cells, raising the possibility that HMMC-1 extensively inhibits invasive growth of HMMC-1 epitope-positive uterine endometrial cancer cells by targeting the cancer-associated form of CD166.

Identification of CD166 as a surface marker for enriching prostate stem/progenitor and cancer initiating cells

New therapies for late stage and castration resistant prostate cancer (CRPC) depend on defining unique properties and pathways of cell sub-populations capable of sustaining the net growth of the cancer. One of the best enrichment schemes for isolating the putative stem/progenitor cell from the murine prostate gland is Lin^-;Sca1⁺;CD49f^hi (LSC^hi), which results in a more than 10-fold enrichment for in vitro sphere-forming activity. We have shown previously that the LSC^hi subpopulation is both necessary and sufficient for cancer initiation in the Pten-null prostate cancer model. To further improve this enrichment scheme, we searched for cell surface molecules upregulated upon castration of murine prostate and identified CD166 as a candidate gene. CD166 encodes a cell surface molecule that can further enrich sphere-forming activity of WT LSC^hi and Pten null LSC^hi. Importantly, CD166 could enrich sphere-forming ability of benign primary human prostate cells in vitro and induce the formation of tubule-like structures in vivo. CD166 expression is upregulated in human prostate cancers, especially CRPC samples. Although genetic deletion of murine CD166 in the Pten null prostate cancer model does not interfere with sphere formation or block prostate cancer progression and CRPC development, the presence of CD166 on prostate stem/progenitors and castration resistant sub-populations suggest that it is a cell surface molecule with the potential for targeted delivery of human prostate cancer therapeutics.

Phosphatidylcholine biosynthesis during neuronal differentiation and its role in cell fate determination

Neuronal differentiation is characterized by neuritogenesis and neurite outgrowth, processes that are dependent on membrane biosynthesis. Thus, the production of phosphatidylcholine (PtdCho), the major membrane phospholipid, should be stimulated during neuronal differentiation. We demonstrate that during retinoic acid (RA)-induced differentiation of Neuro-2a cells, PtdCho synthesis was promoted by an ordered and sequential activation of choline kinase alpha (CK(alpha)) and choline cytidylyltransferase alpha (CCT(alpha)). Early after RA stimulation, the increase in PtdCho synthesis is mainly governed by the biochemical activation of CCT(alpha). Later, the transcription of CK(alpha)- and CCT(alpha)-encoding genes was induced. Both PtdCho biosynthesis and neuronal differentiation are dependent on ERK activation. A novel mechanism is proposed by which PtdCho biosynthesis is coordinated during neuronal differentiation. Enforced expression of either CK(alpha) or CCTalpha increased the rate of synthesis and the amount of PtdCho, and these cells initiated differentiation without RA stimulation, as evidenced by cell morphology and the expression of genes associated with neuritogenesis. The differentiation resulting from enforced expression of CCT(alpha) or CK(alpha) was dependent on persistent ERK activation. These results indicate that elevated PtdCho synthesis could mimic the RA signals and thus determine neuronal cell fate. Moreover, they could explain the key role that PtdCho plays during neuronal regeneration.

Formulation of novel lipid-coated magnetic nanoparticles as the probe for in vivo imaging

Background

Application of superparamagnetic iron oxide nanoparticles (SPIOs) as the contrast agent has improved the quality of magnetic resonance (MR) imaging. Low efficiency of loading the commercially available iron oxide nanoparticles into cells and the cytotoxicity of previously formulated complexes limit their usage as the image probe. Here, we formulated new cationic lipid nanoparticles containing SPIOs feasible for in vivo imaging.

Methods

Hydrophobic SPIOs were incorporated into cationic lipid 1,2-dioleoyl-3-(trimethylammonium) propane (DOTAP) and polyethylene-glycol-2000-1,2-distearyl-3-sn-phosphatidylethanolamine (PEG-DSPE) based micelles by self-assembly procedure to form lipid-coated SPIOs (L-SPIOs). Trace amount of Rhodamine-dioleoyl-phosphatidylethanolamine (Rhodamine-DOPE) was added as a fluorescent indicator. Particle size and zeta potential of L-SPIOs were determined by Dynamic Light Scattering (DLS) and Laser Doppler Velocimetry (LDV), respectively. HeLa, PC-3 and Neuro-2a cells were tested for loading efficiency and cytotoxicity of L-SPIOs using fluorescent microscopy, Prussian blue staining and flow cytometry. L-SPIO-loaded CT-26 cells were tested for in vivo MR imaging.

Results

The novel formulation generates L-SPIOs particle with the average size of 46 nm. We showed efficient cellular uptake of these L-SPIOs with cationic surface charge into HeLa, PC-3 and Neuro-2a cells. The L-SPIO-loaded cells exhibited similar growth potential as compared to unloaded cells, and could be sorted by a magnet stand over ten-day duration. Furthermore, when SPIO-loaded CT-26 tumor cells were injected into Balb/c mice, the growth status of these tumor cells could be monitored using optical and MR images.

Conclusion

We have developed a novel cationic lipid-based nanoparticle of SPIOs with high loading efficiency, low cytotoxicity and long-term imaging signals. The results suggested these newly formulated non-toxic lipid-coated magnetic nanoparticles as a versatile image probe for cell tracking.

O-glycosylation pattern of CD24 from mouse brain

The cell adhesion molecule CD24 is a highly glycosylated glycoprotein that plays important roles in the central nervous system, the immune system and in tumor biology. Since CD24 comprises only a short protein core of approximately 30 amino acids and low conservation among species, it has been proposed that the functions of CD24 are mediated by its glycosylation pattern. Our present study provides evidence that interaction of CD24 with the cell adhesion molecule L1 is mediated by O-linked glycans carrying alpha2,3-linked sialic acid. Furthermore, de-N-glycosylated CD24 was shown to promote or inhibit neurite outgrowth of cerebellar neurons or dorsal root ganglion neurons, respectively, to the same extent as untreated CD24. Therefore, this study is focused on the structural elucidation of the chemically released, permethylated CD24 O-glycans by electrospray ionization ion trap mass spectrometry. Our analyses revealed the occurrence of a diverse mixture of mucin-type and O-mannosyl glycans carrying, in part, functionally relevant epitopes, such as 3-linked sialic acid, disialyl motifs, Le(X), sialyl-Le(X) or HNK-1 units. Hence, our data provide the basis for further studies on the contribution of carbohydrate determinants to CD24-mediated biological activities.

Cytoplasmic accumulation of activated leukocyte cell adhesion molecule is a predictor of disease progression and reduced survival in oral cancer patients

Activated leukocyte cell adhesion molecule (ALCAM) has been proposed to function as a cell surface sensor for cell density, controlling the transition between local cell proliferation and tissue invasion in cancer progression. Herein, we determined ALCAM expression in 107 oral squamous cell carcinomas (OSCCs), 78 oral lesions (58 hyperplasias and 20 dysplasias) and 30 histologically normal oral tissues using immunohistochemistry and correlated with clinicopathological parameters. Significant increase in ALCAM immunopositivity was observed from normal oral mucosa, hyperplasia, dysplasia to OSCCs (p(trend) < 0.001). Increased ALCAM expression was observed in cytoplasm of epithelial cells as early as in hyperplasia (p = 0.001, OR = 3.8). Sixty-five of 107 (61%) OSCCs showed significant overexpression of ALCAM protein in cytoplasm/membrane of tumor cells (p = 0.043; OR = 3.3) in comparison with the normal oral tissues. Among OSCCs, cytoplasmic ALCAM was associated with advanced tumor size, tumor stage and tobacco consumption. Importantly, cytoplasmic ALCAM was an independent predictor of poor prognosis of OSCCs in multivariate analysis (p = 0.012, OR = 6.2). In an attempt to understand the molecular basis of cytoplasmic localization of ALCAM, 14-3-3 zeta and 14-3-3 sigma were identified as its novel binding partners in oral cancer cells. In conclusion, increased expression of ALCAM is an early event in oral tumorigenesis; its cytoplasmic accumulation in tumor cells is a predictor of poor prognosis of OSCCs, underscoring its potential as a candidate prognostic marker for oral cancer.

Immunization with a mimotope of GD2 ganglioside induces CD8+ T cells that recognize cell adhesion molecules on tumor cells

The GD2 ganglioside expressed on neuroectodermal tumor cells has been used as a target for passive and active immunotherapy in patients with malignant melanoma and neuroblastoma. We have reported that immunization of mice with a 47-LDA mimotope of GD2, isolated from a phage display peptide library with anti-GD2 mAb 14G2a, induces MHC class I-restricted CD8(+) T cell responses to syngeneic neuroblastoma tumor cells. The cytotoxic activity of the vaccine-induced CTLs was independent of GD2 expression, suggesting recognition of a novel tumor-associated Ag cross-reacting with 47-LDA. Glycan microarray and immunoblotting studies using 14G2a mAb demonstrated that this Ab is highly specific for the entire carbohydrate motif of GD2 but also cross-reacts with a 105 kDa glycoprotein expressed by GD2(+) and GD2(-) neuroblastoma and melanoma cells. Functional studies of tumor cells grown in three-dimensional collagen cultures with 14G2a mAb showed decreases in matrix metalloproteinase-2 activation, a process regulated by the 105 kDa-activated leukocyte cell adhesion molecule (ALCAM/CD166). A recombinant CD166 glycoprotein was shown to be recognized by 14G2a Ab and inhibition of CD166 expression by RNA interference ablated the cell sensitivity to lysis by 47-LDA-induced CD8(+) T cells in vitro and in vivo. The binding of 14G2a to CD166 was not disruptable by a variety of exo- and endo-glycosidases, implying recognition of a non-glycan epitope on CD166. These results suggest that the vaccine-induced CTLs recognize a 47-LDA cross-reactive epitope expressed by CD166, and reveal a novel mechanism of induction of potent tumor-specific cellular responses by mimotopes of tumor-associated carbohydrate Ags.

Molecular cloning and characterization of the expression pattern of the zebrafish alpha2, 8-sialyltransferases (ST8Sia) in the developing nervous system

Sialyltransferases are Golgi type II transmembrane glycoproteins involved in the biosynthesis of sialylated glycolipids and glycoproteins. These sialylated compounds play fundamental roles in the development of a variety of tissues including the nervous system. In this study, we have molecularly cloned from zebrafish sources, the orthologues of the six human alpha2,8-sialyltransferases (ST8Sia), a family of sialyltransferases implicated in the alpha2-8-mono-, oligo-, and poly-sialylation of glycoproteins and gangliosides and we have analysed their expression pattern in the embryonic zebrafish nervous system, using in situ hybridization. Our results show that all six ST8Sia exhibit distinct and overlapping patterns of expression in the developing zebrafish central nervous system with spatial and temporal regulation of the expression of these genes, which suggests a role for the alpha2-8-sialylated compounds in the developing nervous system.

Molecular evolution and expression of zebrafish St8SiaIII, an alpha-2,8-sialyltransferase involved in myotome development

Enzymes of the St8Sia family, a subgroup of the glycosyltransferases, mediate the transfer of sialic acid to glycoproteins or glycolipids. Here, we describe the cloning of the zebrafish St8SiaIII gene and study its developmental activity. A conserved synteny relationship among vertebrate chromosome regions containing St8SiaIII loci underscores an ancient duplication of this gene in the teleost fish lineage and a specific secondary loss of one paralog in the zebrafish. The single zebrafish St8SiaIII enzyme, which is expected to function as an oligosialyltransferase, lacks maternal activity, is weakly expressed during nervous system development, and shows a highly dynamic expression pattern in somites and somite-derived structures. Morpholino knock-down of St8SiaIII leads to anomalous somite morphologies, including defects in segment boundary formation and myotendious-junction integrity. These phenotypes hint for a basic activity of zebrafish St8SiaIII during segmentation and somite formation, providing novel evidence for a non-neuronal function of sialyltransferases during vertebrate development.

Induction of protective immune responses against NXS2 neuroblastoma challenge in mice by immunotherapy with GD2 mimotope vaccine and IL-15 and IL-21 gene delivery

The GD2 ganglioside expressed on neuroectodermal tumor cells is weakly immunogenic in tumor-bearing patients and induces predominantly IgM antibody responses in the immunized host. Using a syngeneic mouse challenge model with GD2-expressing NXS2 neuroblastoma, we investigated novel strategies for augmenting the effector function of GD2-specific antibody responses induced by a mimotope vaccine. We demonstrated that immunization of A/J mice with DNA vaccine expressing the 47-LDA mimotope of GD2 in combination with IL-15 and IL-21 genes enhanced the induction of GD2 cross-reactive IgG2 antibody responses that exhibited cytolytic activity against NXS2 cells. The combined immunization regimen delivered 1 day after tumor challenge inhibited subcutaneous (s.c.) growth of NXS2 neuroblastoma in A/J mice. The vaccine efficacy was reduced after depletion of NK cells as well as CD4(+) and CD8(+) T lymphocytes suggesting involvement of innate and adaptive immune responses in mediating the antitumor activity in vivo. CD8(+) T cells isolated from the immunized and cured mice were cytotoxic against syngeneic neuroblastoma cells but not against allogeneic EL4 lymphoma, and exhibited antitumor activity after adoptive transfer in NXS2-challenged mice. We also demonstrated that coimmunization of NXS2-challenged mice with the IL-15 and IL-21 gene combination resulted in enhanced CD8(+) T cell function that was partially independent of CD4(+) T cell help in inhibiting tumor growth. This study is the first demonstration that the mimotope vaccine of a weakly immunogenic carbohydrate antigen in combination with plasmid-derived IL-15 and IL-21 cytokines induces both innate and adaptive arms of the immune system leading to the generation of effective protection against neuroblastoma challenge.

Association of Rpn10 with high molecular weight complex is enhanced during retinoic acid-induced differentiation of neuroblastoma cells

The ubiquitin-binding Rpn10 protein serves as an ubiquitin receptor that delivers client proteins to the 26S proteasome, the protein degradation complex. It has been suggested that the ubiquitin-dependent protein degradation is critical for neuronal differentiation and for preventing neurodegenerative diseases. Our previous study indicated the importance of Rpn10 in control of cellular differentiation (Shimada et al., Mol Biol Cell 17:5356-5371, 2006), though the functional relevance of Rpn10 in neuronal cell differentiation remains a mystery to be uncovered. In the present study, we have examined the level of Rpn10 in a proteasome-containing high molecular weight (HMW) protein fraction prepared from the mouse neuroblastoma cell line Neuro2a. We here report that the protein level of Rpn10 in HMW fraction from un-differentiated Neuro2a cells was significantly lower than that of other cultured cell lines. We have found that retinoic acid-induced neural differentiation of Neuro2a cells significantly stimulates the incorporation of Rpn10 into HMW fractions, although the amounts of 26S proteasome subunits were not changed. Our findings provide the first evidence that the modulation of Rpn10 is linked to the control of retinoic acid-induced differentiation of neuroblastoma cells.

Involvement of membrane protein GDE2 in retinoic acid-induced neurite formation in Neuro2A cells

We show that a glycerophosphodiester phosphodiesterase homolog, GDE2, is widely expressed in brain tissues including primary neurons, and that the expression of GDE2 in neuroblastoma Neuro2A cells is significantly upregulated during neuronal differentiation by retinoic acid (RA) treatment. Stable expression of GDE2 resulted in neurite formation in the absence of RA, and GDE2 accumulated at the regions of perinuclear and growth cones in Neuro2A cells. Furthermore, a loss-of-function of GDE2 in Neuro2A cells by RNAi blocked RA-induced neurite formation. These results demonstrate that GDE2 expression during neuronal differentiation plays an important role for growing neurites.

Involvement of the alpha2,8-polysialyltransferases II/STX and IV/PST in the biosynthesis of polysialic acid chains on the O-linked glycoproteins in rainbow trout ovary

Polysialoglycoprotein (PSGP) in salmonid fish egg is a unique glycoprotein bearing alpha2,8-linked polysialic acid (polySia) on its O-linked glycans. Biosynthesis of the polySia chains is developmentally regulated and only occurs at later stage of oogenesis. Two alpha2,8-polysialyltransferases (alpha2,8-polySTs), PST (ST8Sia IV) and STX (ST8Sia II), responsible for the biosynthesis of polySia on N-glycans of glycoproteins, are known in mammals. However, nothing has been known about which alpha2,8-polySTs are involved in the biosynthesis of polySia on O-linked glycans in any glycoproteins. We thus sought to identify cDNA encoding the alpha2,8-polyST involved in polysialylation of PSGP. A clone for PST orthologue, rtPST, and two clones for the STX orthologue, rtSTX-ov and rtSTX-em, were identified in rainbow trout. The deduced amino acid sequence of rtPST shows a high identity (72-77%) to other vertebrate PSTs, while that of rtSTX-ov shows 92% identity with rtSTX-em and a significant identity (63-76%) to other vertebrate STXs. The rtPST exhibited the in vivo alpha2,8-polyST activity, although its in vitro activity was low. However, the rtSTXs showed no in vivo and very low in vitro activities. Interestingly, co-existence of rtPST and rSTX-ov in the reaction mixture synergistically enhanced the alpha2,8-polyST activity. During oogenesis, rtPST was constantly expressed, while the expression of rtSTX-ov was not increased until polySia chain is abundantly biosynthesized in the later stage. rtSTX-em was not expressed in ovary. These results suggest that the enhanced expression of rtSTX-ov under the co-expression with rtPST may be important for the biosynthesis of polySia on O-linked glycans of PSGP.

Transcriptional regulation of the human Sia-alpha2,3-Gal-beta1,4-GlcNAc-R:alpha2,8-sialyltransferase (hST8Sia III) by retinoic acid in human glioblastoma tumor cell line

In this study, we have shown the transcriptional regulation of the human Sia-alpha2,3-Gal-beta1,4-GlcNAc-R:alpha2,8-sialyltransferase (hST8Sia III) induced by retinoic acid (RA), a potent neuronal cell regulator in glioblastoma cell line (U-87MG). The induction of hST8Sia III by RA is regulated at the transcriptional level in a dose- and time-dependent manner, as evidenced by reverse transcription-polymerase chain reaction (RT-PCR). To elucidate the mechanism underlying the regulation of hST8Sia III gene expression in RA-stimulated U-87MG cells, we characterized the promoter region of the hST8Sia III gene. Functional analysis of the 5'-flanking region of the hST8Sia III gene by the transient expression method showed that the -1194 to -816 region, which contains a retinoic acid nucleic receptor (RAR) at -1000 to -982, functions as the RA-inducible promoter in U-87MG cells. Site-directed mutagenesis indicated that the RA binding site at -996 to -991 is crucial for the RA-induced expression of the hST8Sia III in U-87MG cells. In addition, the transcriptional activity of hST8Sia III induced by RA in U-87MG cells was strongly inhibited by SP600125, c-Jun N-terminal Kinase (JNK) inhibitor, as determined by RT-PCR and luciferase assay of hST8Sia III promoter containing the -1194 to -816 regions. These results suggest that RA markedly modulates transcriptional regulation of hST8Sia III gene expression through JNK signal pathway in U-87MG cells.

N-glycan structures and N-glycosylation sites of mouse soluble intercellular adhesion molecule-1 revealed by MALDI-TOF and FTICR mass spectrometry

Intercellular adhesion molecule-1 (ICAM-1) is a heavily N-glycosylated transmembrane protein comprising five extracellular Ig-like domains. The soluble isoform of ICAM-1 (sICAM-1), consisting of its extracellular part, is elevated in the cerebrospinal fluid of patients with severe brain trauma. In mouse astrocytes, recombinant mouse sICAM-1 induces the production of the CXC chemokine macrophage inflammatory protein-2 (MIP-2). MIP-2 induction is glycosylation dependent, as it is strongly enhanced when sICAM-1 carries sialylated, complex-type N-glycans as synthesized by wild-type Chinese hamster ovary (CHO) cells. The present study was aimed at elucidating the N-glycosylation of mouse sICAM-1 expressed in wild-type CHO cells with regard to sialylation, N-glycan profile, and N-glycosylation sites. Ion-exchange chromatography and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) of the released N-glycans showed that sICAM-1 mostly carried di- and trisialylated complex-type N-glycans with or without one fucose. In some sialylated N-glycans, one N-acetylneuraminic acid was replaced by N-glycolylneuraminic acid, and approximately 4% carried a higher number of sialic acid residues than of antennae. The N-glycosylation sites of mouse sICAM-1 were analyzed by MALDI-Fourier transform ion cyclotron resonance (FTICR)-MS and nanoLC-ESI-FTICR-MS of tryptic digests of mouse sICAM-1 expressed in the Lec1 mutant of CHO cells. All nine consensus sequences for N-glycosylation were found to be glycosylated. These results show that the N-glycans that enhance the MIP-2-inducing activity of mouse sICAM-1 are mostly di- and trisialylated complex-type N-glycans including a small fraction carrying more sialic acid residues than antennae and that the nine N-glycosylation sites of mouse sICAM-1 are all glycosylated.

Molecular mechanisms involved in transcriptional activation of the human Sia-α2,3-Gal-β1,4-GlcNAc-R:α2,8-sialyltransferase (hST8Sia III) gene induced by KCl in human glioblastoma cells

In the present study, we have shown that KCl known as an inducer for differentiation of neuronal cells increases the human Sia-alpha2,3-Gal-beta1,4-GlcNAc-R:alpha2,8-sialyltransferase (hST8Sia III) gene transcription via phosphoinositide 3 kinase (PI-3K) in glioblastoma U-87MG cells. The induction of hST8Sia III by KCl is regulated at the transcriptional level in a dose- and time-dependent manner as evidenced by reverse transcription-polymerase chain reaction (RT-PCR). To elucidate the mechanism underlying the regulation of hST8Sia III gene expression in U-87MG cells induced by KCl, we characterized the promoter region of the hST8Sia III gene. Functional analysis of the 5'-flanking region of the hST8Sia III gene by the transient expression method showed that the -1194 to -816 region functions as the KCl-inducible promoter in U-87MG cells. Furthermore, as evidenced by Western blot analysis and RT-PCR, KCl-induced expression of hST8Sia III gene was dependent on the PI-3K signal transduction pathway during the neuronal differentiation of U-87 cells, as an increase in beta-tubulin III known as a neuronal differentiation marker was observed. In KCl-depolarization on U-87 cells, the PI-3K-dependent promoter activation at the -1194 to -816 region up-regulated expression of hST8Sia III gene. These results suggest that the expression of hST8Sia III gene via the PI-3K signaling pathway is enhanced during KCl-induced differentiation of U-87 cells by increasing expression of beta-tubulin III.

Molecular cloning and expression of a human hST8Sia VI (alpha2,8-sialyltransferase) responsible for the synthesis of the diSia motif on O-glycosylproteins

Based on BLAST analysis of the human and mouse genome databases using the human CMP sialic acid; alpha2,8-sialyltransferase cDNA (hST8Sia I; EC 2.4.99.8), a putative sialyltransferase gene, was identified on human chromosome 10. The genomic organization was found to be similar to that of hST8Sia I and hST8Sia V. Transcriptional expression analysis showed that the newly identified gene was constitutively expressed at low levels in various human tissues and cell lines. We have isolated a full-length cDNA clone from the breast cancer cell line MCF-7 that encoded a type II membrane protein of 398 amino acid residues with the conserved motifs of sialyltransferases. We have established a mammary cell line (MDA-MB-231) stably transfected with the full-length hST8Sia VI and the analysis of sialylated carbohydrate structures expressed at the cell surface clearly indicated the disappearance of Neu5Acalpha2-3-sialylated structures. The transient expression of a truncated soluble form of the enzyme in either COS-7 cells or insect Sf-9 cells led to the production of an active enzyme in which substrate specificity was determined. Detailed substrate specificity analysis of the hST8Sia VI recombinant enzyme in vitro, revealed that this enzyme required the trisaccharide Neu5Acalpha2-3Galbeta1-3GalNAc (where Neu5Ac is N-acetylneuraminic acid and GalNAc is N-acetylgalactosamine) to generate diSia (disialic acid) motifs specifically on O-glycans.

Up-Regulation of Heme Biosynthesis during Differentiation of Neuro2a Cells

Heme is an iron-containing tetrapyrrole molecule that functions as a prosthetic group for proteins such as mitochondrial respiratory enzymes. Several studies have suggested that heme has essential functions in the construction and maintenance of the nervous system. In this study, the contents of three biologically important forms of heme (types a, b, and c) and the expression of heme biosynthetic enzymes were examined in differentiating Neuro2a cells. During neuronal differentiation, there were increases in the cellular heme levels and increases in the mRNA levels for the rate-limiting enzymes of heme biosynthesis, such as aminolevulinic acid synthase (ALAS; EC 2.3.1.37) and coproporphyrinogen oxidase (EC 1.3.3.3). With respect to heme contents, heme b increased in the late phase of differentiation, but no apparent increase in heme a or b was observed in the early phase. In contrast, heme c (cytochrome c) markedly increased during the early phase of differentiation. This change preceded the increase in heme b and the up-regulation of the mRNA levels for heme biosynthetic enzymes. This study suggests the up-regulation of heme biosynthesis and differential regulation of the heme a, b, and c levels during neuronal differentiation.

N-linked oligosaccharide analysis of rat brain Thy-1 by liquid chromatography with graphitized carbon column/ion trap-Fourier transform ion cyclotron resonance mass spectrometry in positive and negative ion modes

We have previously described the site-specific glycosylation analysis of rat brain Thy-1 by LC/multistage tandem mass spectrometry (MS(n)) using proteinase-digested Thy-1. In the present study, detailed structures of oligosaccharides released from Thy-1 were elucidated by mass spectrometric oligosaccharide profiling using LC/MS with a graphitized carbon column (GCC-LC/MS). First, using model oligosaccharides, we improved the oligosaccharide profiling by ion trap mass spectrometry (IT-MS) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Sequential scanning of a full MS(1) scan with FT-ICR-MS followed by data-dependent MS(n) with IT-MS in positive ion mode, and a subsequent full MS(1) scan with FT-ICR-MS followed by data-dependent MS(n) with IT-MS in negative ion mode enabled the monosaccharide composition analysis as well as profiling and sequencing of both neutral and acidic oligosaccharides in a single analysis. The improved oligosaccharide profiling was applied to elucidation of N-linked oligosaccharides from Thy-1 isolated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It was demonstrated that Thy-1 possesses a significant variety of N-linked oligosaccharides, including Lewis a/x, Lewis b/y, and disialylated structure as a partial structure. Our method could be applicable to analysis of a small abundance of glycoproteins, and could become a powerful tool for glycoproteomics.

Inflammation-dependent changes in α2,3-, α2,6-, and α2,8-sialic acid glycotopes on serum glycoproteins in mice

The expression of acute-phase serum proteins increases in response to inflammatory stimuli. Most of these proteins are glycoproteins that often contain sialic acids (Sia). It is unknown, however, how the expression of Sia in these glycoproteins changes during inflammation. This study demonstrates changes in the alpha2,3-, alpha2,6-, and alpha2,8-Sia glycotopes on serum glycoproteins in response to turpentine oil-induced inflammation, based on lectin- and immunoblot analyses by using sialyl linkage-specific lectins, Maackia amurensis for the alpha2,3-Sia glycotope and Sambucus sieboldiana for the alpha2,6-Sia glycotopes, and monoclonal antibody 2-4B (mAb.2-4B) recognizing the di- and oligomers of the alpha2,8-Neu5Gc residue. There was an increase in a limited number of sialoglycoproteins containing the alpha2,3-, alpha2,6-, or alpha2,8-Sia glycotopes. Reverse transcription-polymerase chain reaction (RT-PCR) analysis of the expression profiles of mRNAs for the known sialyltransferases in mouse liver during inflammation indicated the up-regulated expression of beta-galactoside alpha2,3-sialyltransferases (ST3Gal I and ST3Gal III) and beta-N-acetylgalactosaminide alpha2,6-sialyltransferase (ST6GalNAc VI) as well as beta-galactoside alpha2,6-sialyltransferase (ST6Gal I) mRNAs. Notably, ST3Gal I and III and ST6GalNAc VI are involved in the synthesis of the alpha2,3- and alpha2,6-Sia glycotopes on O-glycan chains and possibly on gangliosides, whereas ST6Gal I is specific for N-glycan chains. These results provide evidence for the inflammation-induced expression of sialyl glycotopes in serum glycoproteins. We demonstrated that inflammation significantly increased the expression of an unknown 32-kDa glycoprotein containing the alpha2,8-Sia glycotope. The mechanism for the increase in glycoprotein in inflamed mouse serum remains to be examined, as mRNA expression for all of the alpha2,8-sialyltransferases (ST8Sia I-VI) was unchanged during inflammation.

Expression and characterization of murine hevin (SC1), a member of the SPARC family of matricellular proteins

Hevin, also known as SC1, MAST 9, SPARC-like 1, RAGS1 and ECM2, is a member of the SPARC-related family of matricellular proteins. Mouse hevin is 53% identical to mouse SPARC, and both proteins share a follistatin-like module and an extracellular Ca(2+)-binding (E-C) domain. SPARC functions as a modulator of cell-matrix interactions, a regulator of growth factor activity, a de-adhesive protein, and a cell cycle inhibitor. Although the functions of mouse hevin are unknown, its human orthologue has been shown to be de-adhesive for endothelial cells. We now report the production of recombinant mouse hevin in insect cells through the use of a baculoviral expression system and its purification by anion-exchange, size-exclusion chromatography, and isoelectric focusing. Furthermore, we have produced rat anti-hevin monoclonal antibodies (MAbs) that have been characterized by indirect and capture ELISAs, immunoblotting, immunoprecipitation, and immunohistochemistry (IHC). Recombinant hevin, present as a soluble factor or bound to tissue-culture plastic, inhibited the spreading of bovine aortic endothelial cells in vitro. IHC analysis of hevin in normal human and mouse tissues revealed a limited expression pattern in many tissues, with particularly dominant staining in dermis, ducts, vasculature, muscle, and brain. In lung and pancreatic tumor xenografts, we found distinct reactivity with MAbs that were selective for stromal cells, tumor cells, and/or endothelial cells. Although similar to SPARC in its anti-adhesive activities, hevin nevertheless exhibits a distinctive histological distribution that, in certain invasive tumors, is associated with desmoplasia.

Differential transcriptional regulation by human immunodeficiency virus type 1 and gp120 in human astrocytes

Astrocytes may be infected with the human immunodeficiency virus type 1 (HIV-1) or exposed to the HIV protein gp120, yet their role in the pathogenesis of HIV dementia is largely unknown. To characterize the effects of HIV on astrocytic transcription, microarray analysis and ribonuclease protection assays (RPA) were performed. Infection of astrocytes by HIV or treatment with gp120 had differential and profound effects on gene transcription. Of the 1153 oligonucleotides on the immune-based array, the expression of 108 genes (53 up; 55 down) and 82 genes (32 up; 50 down) were significantly modulated by gp120 and HIV infection respectively. Of the 1153 oligonucleotides on the neuro-based array, 58 genes (25 up; 33 down) and 47 genes (17 up; 30 down) were significantly modulated by gp120 and HIV infection respectively. Chemokine and cytokine induction occurred predominantly by HIV infection, whereas gp120 had no significant effect. These results were confirmed by RPA. The authors conclude that profound alterations of astrocytic function occur in response to HIV infection or interaction with viral proteins, suggesting that astrocytes may play an important role in the pathogenesis of HIV dementia.

Polysialic acid in human milk. CD36 is a new member of mammalian polysialic acid-containing glycoprotein

The neural cell adhesion molecule and the voltage-sensitive sodium channel alpha-subunit are the only two molecules in mammals known to be modified by alpha-2,8-linked polysialic acid (polySia). We found a new polySia-containing glycoprotein in human milk and identified it as CD36, a member of the B class of the scavenger receptor superfamily. The polySia-containing glycan chain(s) were removed by alkaline treatment but not by peptide:N-glycanase F digestion, indicating that milk CD36 contained polySia on O-linked glycan chain(s). Polysialylation of CD36 occurs not only in human milk but also in mouse milk. However, CD36 in human platelets is not polysialylated. PolySia CD36 is secreted in milk at any lactation stage and reaches peak level at 1 month after parturition. Thus, it is suggested that polySia of milk CD36 is significant for neonatal development in terms of protection and nutrition.