Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0017638 (glioma)
 30,880 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In this report we focus on the characterization of appican, the chondroitin sulfate proteoglycan form of amyloid precursor protein (APP), and the role that it and other proteoglycans may play in AD. Appican is expressed by certain transformed cell lines of neural origin, namely C6 cells and N2a neuroblastomas. It is detected in both human and rat brain and in primary cultures is expressed by astrocytes, but not neurons. The core protein of appican has been shown to be an alternatively spliced isoform of APP, lacking exon 15 of the APP gene, originally identified in leukocytes (L-APP). Splicing out of exon 15 results in the joining of exons 14 and 16, and formation of an Asp-Xaa-Ser-Gly consensus sequence for chondroitin sulfate chain attachment to serine 619 of L-APP, which lies 16 amino acids upstream of the A beta peptide sequence. Mutation of this serine residue to an alanine prevented chondroitin sulfate chain addition to the core protein. Levels of appican expression could be regulated by growth conditions independently of APP, suggesting that these molecules may serve distinct physiological roles within the cell. Morphological changes were also observed in both astrocytic and transformed cell cultures, that appeared to reflect changes in levels of appican expression. Preliminary data suggest that appican may be a strong cell adhesion molecule. Transfected C6 glioma cells overexpressing appican remained attached to tissue culture dishes markedly better than either C6 cells over-expressing exon-15 containing APP or WT C6 cells. Appican-enriched extracellular matrix (ECM) was also observed to serve as a much better substrate for attachment of N2a neuroblastomas, pheocromocytoma PC12 cells and primary astrocytes compared to APP enriched ECM.
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PMID:Characterization of appican, the chondroitin sulfate proteoglycan form of the Alzheimer amyloid precursor protein. 911 61

Two nervous tissue-specific chondroitin sulfate proteoglycans, neurocan and phosphacan (the extracellular domain of protein-tyrosine phosphatase-zeta/beta), are high-affinity ligands of tenascin-C. Using portions of tenascin-C expressed as recombinant proteins in human fibrosarcoma cells, we have demonstrated both by direct radioligand binding assays and inhibition studies that phosphacan binding is retained in all deletion variants except those lacking the fibrinogen-like globe and that phosphacan binds to this single domain with nearly the same affinity (Kd approximately 12 nM) as to native or recombinant tenascin-C. However, maximum binding of neurocan requires both the fibrinogen globe and some of the adjacent fibronectin type III repeats. Binding of phosphacan and neurocan to intact tenascin-C, and of phosphacan to the fibrinogen globe, is significantly increased in the presence of calcium. Chondroitinase treatment of the proteoglycans did not affect their binding to either native tenascin-C or to any of the recombinant proteins, demonstrating that these interactions are mediated by the proteoglycan core proteins rather than through the glycosaminoglycan chains. These results are also consistent with rotary shadowing electron micrographs that show phosphacan as a rod terminated at one end by a globular domain that is frequently seen apposed to the fibrinogen globe in mixtures of phosphacan and tenascin-C. C6 glioma cells adhere to and spread on deletion variants of tenascin-C containing only the epidermal growth factor-like domains or the fibronectin type III repeats and the fibrinogen globe. In both cases cell adhesion was inhibited by similar concentrations of phosphacan, demonstrating that the fibrinogen globe is not necessary for this effect, which is apparently mediated by a direct action of phosphacan on the cells rather than by its interaction with the proteoglycan binding site on tenascin-C.
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PMID:The fibrinogen-like globe of tenascin-C mediates its interactions with neurocan and phosphacan/protein-tyrosine phosphatase-zeta/beta. 918 84

Appicans are secreted or cell-associated brain chondroitin sulfate proteoglycans produced by glia cells and containing Alzheimer amyloid precursor protein (APP) as a core protein. Here, we report that rat C6 glioma cells transfected with appican displayed a dramatic change in their phenotypic appearance compared with untransfected cells or cells transfected with APP. Appican-transfected cells lost the round appearance of the untransfected control C6 cells, acquired a flat morphology, and elaborated more processes than control cells. Untransfected, or APP-transfected C6, cells were completely dissociated from their substrate after 40 min of treatment with cell dissociation solution. Under the same conditions, however, <20% of the appican-transfected C6 cells were dissociated from their substrate, suggesting that the appican-transfected glia cells attach more avidly to their substrate than do untransfected or APP transfected control cells. In contrast, appican-transfected fibroblast cells showed no morphological changes and dissociated from their substrate similarly to untransfected fibroblast cells. Extracellular matrix (ECM) prepared from appican-transfected C6 cell cultures contained high levels of appican and was a significantly better substrate for the attachment of C6 cells than ECM from either untransfected or APP-transfected cultures. Furthermore, cell adhesion to ECM was independent of the level of appican expression of the plated cells. ECM from appican-transfected C6 cultures stimulated adhesion of other neural cells including primary astrocytes, Neuro2a neuroblastoma, and PC12 pheochromocytoma, but not fibroblast cells. Conditioned media from appican-transfected C6 cultures failed to promote cell adhesion. Together, these data suggest that secreted appican incorporates into ECM and promotes adhesion of neural cells. Furthermore, our data suggest that the chondroitin sulfate chain engenders APP with novel biological functions.
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PMID:Appican expression induces morphological changes in C6 glioma cells and promotes adhesion of neural cells to the extracellular matrix. 918 36

Catalytic RNA or ribozymes have important potential applications as molecular biological tools in the study of gene expression and as therapeutic inhibitors of disease-causing genes. Very little is known, however, about the cellular uptake mechanisms of exogenously delivered synthetic ribozymes. In this study, we have characterized the uptake properties of a synthetic, 2'-O-methyl-modified ribozyme containing U4/U7 amino groups within the catalytic core of the hammerhead motif. The cellular uptake of the internally [32P]-radiolabeled hammerhead ribozyme in U87-MG glioma cells was temperature, energy, and pH dependent and involved an active process that could be competed with cold ribozyme of the same chemistry and sequence, an all 2'-O-methyl-modified ribozyme of the same sequence, antisense PS-ODNs, and a variety of other polyanions (salmon sperm DNA, spermidine, dextran sulfate, and heparin). Subcellular distribution studies of fluorescently labeled ribozymes confirmed an extranuclear, punctate localization similar to that observed for an endosomal marker, dextran. Our study highlights that hammerhead ribozymes, despite exhibiting a defined secondary structure, enter cells by an endocytic mechanism that appears to be similar to that reported for a variety of antisense ODNs. These observations should facilitate the development of more efficient delivery systems.
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PMID:Cellular uptake properties of a 2'-amino/2'-O-methyl-modified chimeric hammerhead ribozyme targeted to the epidermal growth factor receptor mRNA. 930 83

We have investigated the expression patterns and subcellular localization in nervous tissue of glypican, a major glycosylphosphatidylinositol-anchored heparan sulfate proteoglycan that is predominantly synthesized by neurons, and of biglycan, a small, leucine-rich chondroitin sulfate proteoglycan. By laser scanning confocal microscopy of rat central nervous tissue and C6 glioma cells, we found that a significant portion of the glypican and biglycan immunoreactivity colocalized with nuclear staining by propidium iodide and was also seen in isolated nuclei. In certain regions, staining was selective, insofar as glypican and biglycan immunoreactivity in the nucleus was seen predominantly in a subpopulation of large spinal cord neurons. The amino acid sequences of both proteoglycans contain potential nuclear localization signals, and these were demonstrated to be functional based on their ability to target beta-galactosidase fusion proteins to the nuclei of transfected 293 cells. Nuclear localization of glypican beta-galactosidase or Fc fusion proteins in transfected 293 cells and C6 glioma cells was greatly reduced or abolished after mutation of the basic amino acids or deletion of the sequence containing the nuclear localization signal, and no nuclear staining was seen in the case of heparan sulfate and chondroitin sulfate proteoglycans that do not possess a nuclear localization signal, such as syndecan-3 or decorin (which is closely related in structure to biglycan). Transfection of COS-1 cells with an epitope-tagged glypican cDNA demonstrated transport of the full-length proteoglycan to the nucleus, and there are also dynamic changes in the pattern of glypican immunoreactivity in the nucleus of C6 cells both during cell division and correlated with different phases of the cell cycle. Our data therefore suggest that in certain cells and central nervous system regions, glypican and biglycan may be involved in the regulation of cell division and survival by directly participating in nuclear processes.
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PMID:Glypican and biglycan in the nuclei of neurons and glioma cells: presence of functional nuclear localization signals and dynamic changes in glypican during the cell cycle. 936 4

It has been found that sphingosine and sphingosylphosphorylcholine (amphiphilic cations) have a stimulatory, and cholesterol 3-sulfate (an amphiphilic anion), an inhibitory, effect on [14C]serine incorporation into phosphatidylserine in glioma C6 and rat liver microsomes. In glioma intact cells sphingosine stimulates phosphatidylserine synthesis in a process independent of protein kinase C, but suppressed by thapsigargin. We suggest that the stimulation of the enzyme occurs by the interaction of amphiphilic cations with the membrane cosubstrate phospholipids, leading to a charge redistribution on their phosphate groups, and hence facilitating the enzyme action. A new hypothesis concerning the mechanism of the serine base exchange reaction is discussed.
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PMID:Serine base exchange enzyme activity is modulated by sphingosine and other amphiphilic compounds: possible role of positive charge in increasing the synthesis of phosphatidylserine. 940 36

Antibody to galactocerebroside (GalC) evokes a Ca2+ response in cultured glioma U-87 MG cells. The rise in intracellular calcium [Ca2+]i occurs largely due to the influx of Ca2+ through a plasma membrane channel, though the release of Ca2+ from intracellular stores also contributes. We characterized the channel activated by anti-GalC. The channel activity was transient and the inactivation appeared to be Ca2+ dependent. The channel was impermeant to monovalent ions Na+ and K+ and also to Mn2+. Ni2+ and Co2+ neither permeate through the channel nor inhibit the Ca2+ influx. In contrast Cd2+ the most potent inorganic blocker of Ca2+ channels permeated through this channel. The Ca2+ influx was inhibited by verapamil with IC50 of 65 +/- 8 microM. The Ca2+ influx as well as the intracellular release were markedly inhibited by neomycin sulfate and phorbol dibutyrate, suggesting that the Ca2+ influx may be mediated by IP3 (1). Depletion of intracellular Ca2+ stores by thapsigargin was followed by Ca2+ influx. This represents the capacitative Ca2+ entry pathway and is distinct from the channel activated by anti -GalC.
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PMID:A novel type of Ca2+ channel in U-87 MG cells activated by anti-galactocerebroside. 944 38

The cytotoxicity of alpha-particle-emitting endoradiotherapeutic compounds is of increasing interest because clinical evaluation of these potential therapeutic agents is commencing. Astatine-211 is a radionuclide with a 7.2-h half-life that emits 5.87 and 7.45 MeV alpha particles. In the present work, we have investigated the in vitro cytotoxicity of 211At-labeled chimeric monoclonal antibodies (mAbs) in monolayers of D-247 MG human glioma cells and SK-MEL-28 human melanoma cells. The mAbs studied were 81C6, reactive with the extracellular matrix antigen tenascin, Mel-14, directed against the cell membrane antigen proteoglycan chondroitin sulfate, and a nonspecific control mAb, TPS3.2. Cell uptake increased as a function of activity concentration after a 1-h exposure to the 211At-labeled mAbs. The retention of activity was also measured to calculate cumulative activity associated with the cells and the medium. The clonogenic survival as a function of activity concentration was linear in all cases with no detectable shoulder. Microdosimetric analyses were performed based on measured cell geometry, cumulative activity and Monte Carlo transport of alpha particles. Using 18 kBq/ml activity concentration and 1 h of incubation, a two to five times higher activity bound to the microcolonies was found for the specific mAbs compared to the nonspecific mAb. These calculations indicated that a survival fraction of 0.37 was achieved with 0.24-0.28 Gy for D-247 MG cells and 0.27-0.29 Gy for SK-MEL-28 cells. The microdosimetric cell sensitivity, z0, for D-247 MG cells was significantly lower than for SK-MEL-28 cells (0.08 compared to 0.15 Gy). For both cell lines, reduction in survival to 0.37 required an average of only 1-2 alpha-particle hits to the cell nucleus.
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PMID:The cytotoxicity and microdosimetry of astatine-211-labeled chimeric monoclonal antibodies in human glioma and melanoma cells in vitro. 945 95

Cyclosporin A (CsA) exerts its immunosuppressive effect by inhibiting the activity of nuclear factor of activated T cells (NFAT), thus preventing transcriptional induction of several cytokine genes. This effect is mediated through inactivation of the phosphatase calcineurin, which inhibits translocation of an NFAT component to the nucleus. We have previously reported that CsA inhibits the growth of rat C6 glioma cells in a dose-dependent manner and induces apoptotic cell death. Here, we report that NFAT DNA-binding activity is present in the nuclear extracts from C6 glioma cells and that CsA treatment inhibits the formation of a functional NFAT complex. We provide evidence for the presence of a group of NFATc proteins in proliferating glioma cells. Immunoblot analyses show that stimulation of C6 glioma cells with a calcium-inducing agent, ionomycin, alters NFATc migration on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This alteration is inhibited by simultaneous treatment with CsA, suggesting a calcineurin involvement in the regulation of glioma NFATc proteins. Direct immunofluorescence reveals the presence of NFATc proteins in nuclei of proliferating glioma cells and their disappearance in CsA-treated cells. These data point to a new mechanism of transcription regulation in glioma cells and provide an explanation for the observed sensitivity of glioma cells to CsA.
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PMID:Nuclear factor of activated T cells (NFAT) as a new component of the signal transduction pathway in glioma cells. 964 59

N-Acetylglucosamine-6-O-sulfotransferase catalyzes the transfer of sulfate from 3'-phosphoadenosine 5'-phosphosulfate to position 6 of a non-reducing N-acetylglucosamine (GlcNAc) residue. We have cloned human GlcNAc-6-O-sulfotransferase cDNA, based on the sequence homology to cloned cDNA of mouse GlcNAc-6-O-sulfotransferase. The predicted protein sequence of the human enzyme was highly homologous to that of the mouse enzyme; in the 363 amino acid stretch of the catalytic region, the two proteins were nearly identical except for conservative changes in 3 amino acid residues. The expressed enzyme transferred sulfate to GlcNAcbeta1-3Galbeta1-4GlcNAcbeta1-3Galbeta1-4Gl cNAc. Co-transfection of the enzyme cDNA and fucosyltransferase VII cDNA into COS-7 cells resulted in cell surface expression of 6-sulfo sialyl Lewis X. Fluorescence in situ hybridization analysis revealed that the GlcNAc-6-O-sulfotransferase gene is located on human chromosome 7q31. mRNA of the human enzyme was strongly expressed in the bone marrow, peripheral blood leukocytes, spleen, brain, spinal cord, ovary, and placenta, and moderate levels of expression were observed in many organs including lymph nodes and thymus. In situ hybridization with the mouse system showed that the transcript was localized in specific regions of the brain, i.e. pyramidal cells in the CA3 subregion of the hippocampus, cerebellar nucleus and Purkinje cells. Among human tumor cells, strong expression of the mRNA was found in MOLT-4 and Jarkat lymphoblastic leukemia cells, Raji lymphoma cells, K-562 chronic myelogeneous leukemia cells, U251 glioma cells, and G361 melanoma cells. Carbohydrate structures synthesized by the sulfotransferase may be involved in various aspects of the differentiation and behavior of blood cells, their progenitor cells, and neurons in the central nervous system.
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PMID:Human N-acetylglucosamine-6-O-sulfotransferase involved in the biosynthesis of 6-sulfo sialyl Lewis X: molecular cloning, chromosomal mapping, and expression in various organs and tumor cells. 972 82


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