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)

The role of the NT-3 has been implicated in the survival of progenitor oligodendrocytes in culture. The object of this study was to investigate the expression of the TrkC receptor and its responsiveness in glial cells. We report the expression of two TrkC receptor isoforms in rat primary oligodendrocyte cultures, a glial progenitor cell line, CG-4, and in C6 glioma cells. The reverse transcription-polymerase chain reaction-aided amplification of glial trkC with specific primers from the kinase domain, followed by its cloning and sequencing, shows the presence of two trkC transcripts. The sequence of one of the transcripts is homologous to a previously identified trkC isoform which encodes a functional receptor. The other transcript contains a 42-bp insert in the kinase domain. A Western blot of CG-4 and C6 probed with antibody to a TrkC revealed the presence of gp145-kDa protein band. The investigations revealed a rapid autophosphorylation of gp145TrkC in CG-4 and C6 cells in the presence of its specific ligand, NT-3. Furthermore, K252a, a neurotrophin-specific inhibitor, abolishes the NT-3-mediated receptor autophosphorylation. We also examined other NT-3-dependent phosphorylation of cellular substrates in oligodendroglial cells. Interestingly, we observed phosphorylation of phospholipase C gamma-1 in CG-4 and C6 cells, and phosphorylation of phosphatidylinositol 3-kinase in C6 cells in the presence of NT-3. Both the NT-mediated phosphorylation of phospholipase C gamma-1 and phosphorylation of phosphatidylinositol 3-kinase are blocked in the presence of K252a. The detection of the NT-3-mediated early signal transduction events demonstrates that TrkC receptor exhibits NT-3-mediated intracellular response in oligodendroglial cells.
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PMID:Neurotrophin activates signal transduction in oligodendroglial cells: expression of functional TrkC receptor isoforms. 877 70

Neuronal and glial sodium-dependent transporters are crucial for the control of extracellular glutamate levels in the CNS. The regulation of these transporters is relatively unexplored, but the activity of other transporters is regulated by protein kinase C (PKC)- and phosphatidylinositol 3-kinase (PI3K)-mediated trafficking to and from the cell surface. In the present study the C6 glioma cell line was used as a model system that endogenously expresses the excitatory amino acid carrier 1 (EAAC1) subtype of neuronal glutamate transporter. As previously observed, phorbol 12-myristate 13-acetate (PMA) caused an 80% increase in transporter activity within minutes that cannot be attributed to the synthesis of new transporters. This increase in activity correlated with an increase in cell surface expression of EAAC1 as measured by using a membrane-impermeant biotinylation reagent. Both effects of PMA were blocked by the PKC inhibitor bisindolylmaleimide II (Bis II). The putative PI3K inhibitor, wortmannin, decreased L-[3H]-glutamate uptake activity by >50% within minutes. Wortmannin decreased the Vmax of L-[3H]-glutamate and D-[3H]-aspartate transport, but it did not affect Na+-dependent [3H]-glycine transport. Wortmannin also decreased cell surface expression of EAAC1. Although wortmannin did not block the effects of PMA on activity, it prevented the PMA-induced increase in cell surface expression. This trafficking of EAAC1 also was examined with immunofluorescent confocal microscopy, which supported the biotinylation studies and also revealed a clustering of EAAC1 at cell surface after treatment with PMA. These studies suggest that the trafficking of the neuronal glutamate transporter EAAC1 is regulated by two independent signaling pathways and also may suggest a novel endogenous protective mechanism to limit glutamate-induced excitotoxicity.
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PMID:Multiple signaling pathways regulate cell surface expression and activity of the excitatory amino acid carrier 1 subtype of Glu transporter in C6 glioma. 950 8

ErbB-4 is a recently described member of the epidermal growth factor receptor (EGFR) family which together with erbB-3 acts as a receptor for a group of ligands known as the neuregulins (NRGs) or heregulins (HRGs). Unlike the EGFR and erbB-2 relatively little is known about the expression of erbB-4 in human tumours. Using RT-PCR and Southern blotting analysis we have investigated the expression of erbB-4 mRNA in a range of human tumour cell lines and in normal and malignant breast tissue. Using primers which amplified a 658 base pair (bp) region corresponding to part of the cytoplasmic domain of c-erbB-4 we found the receptor was expressed in some but not all breast and ovarian tumour cell lines and also in a glioma cell line. The highest level of erbB-4 expression was found in the ovarian carcinoma OVCAR-3 and the breast carcinoma T-47D. In all cell lines where the 'full-length' erbB-4 was detected, a second previously undescribed c-erbB-4 sequence was also found as a 610 bp PCR product. The alternative PCR product was identical in sequence to c-erbB-4 except for a deletion of 48 bp which encodes a consensus phosphatidylinositol 3-kinase (PI3K) binding site. This suggested that the two forms of erbB-4 might interact with different intracellular signalling pathways and therefore influence a wider variety of cellular responses to heregulin than previously thought. Expression of both erbB-4 variants was found in 7/7 normal breast tissues but only in 9/12 breast tumours analysed. In line with the terminology of Elenius et al. (1997b) we have designated the two isoforms of the C-terminal transcripts as CT-a (full-length) and CT-b which lacks the P13K binding motif. These results identify suitable cell lines for the further investigation of erbB-4 expression and function and suggest that the role of erbB-4 in breast cancer warrants further investigation with larger numbers of normal and malignant breast tissues.
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PMID:Two erbB-4 transcripts are expressed in normal breast and in most breast cancers. 978 9

Increased numbers of platelet-derived growth factor beta receptors betaPPDGFRs) on neovascular endothelial cells is a common occurrence in several pathological conditions including wound healing, inflammation, and glioma tumorigenesis. Here we sought to test the biological significance of this by determining whether expression of wild-type betaPDGFR by normal aortic endothelial cells affected the expression of the vascular endothelial growth factor (VEGF), a critical angiogenesis regulator and mitogen for such cells. The results showed that PDGF could increase transcription and secretion of VEGF by betaPDGFR-expressing endothelial cells. Moreover, we further demonstrated a requirement for the activation of phosphatidylinositol 3-kinase (PI3K) in this response by using chemical inhibitors of PI3K, mutant PDGFR, and dominant-negative PI3K. These studies suggest a novel mechanism by which PDGF induces VEGF expression in endothelial cells, define VEGF as a downstream target for PI3K, and invoke a role for PI3K in angiogenesis.
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PMID:Induction of vascular endothelial growth factor expression in endothelial cells by platelet-derived growth factor through the activation of phosphatidylinositol 3-kinase. 1019 15

Na(+)-dependent glutamate transporters are the primary mechanism for removal of excitatory amino acids (EAAs) from the extracellular space of the central nervous system and influence both physiologic and pathologic effects of these compounds. Recent evidence suggests that the activity and cell surface expression of a neuronal subtype of glutamate transporter, EAAC1, are rapidly increased by direct activation of protein kinase C and are decreased by wortmannin, an inhibitor of phosphatidylinositol 3-kinase (PI3-K). We hypothesized that this regulation could be analogous to insulin-induced stimulation of the GLUT4 subtype of glucose transporter, which is dependent upon activation of PI3-K. Using C6 glioma, a cell line that endogenously and selectively expresses EAAC1, we report that platelet-derived growth factor (PDGF) increased Na(+)-dependent L-[(3)H]-glutamate transport activity within 30 min. This effect of PDGF was not due to a change in total cellular EAAC1 immunoreactivity but was instead correlated with an increase cell surface expression of EAAC1, as measured using a membrane impermeant biotinylation reagent combined with Western blotting. A decrease in nonbiotinylated intracellular EAAC1 was also observed. These studies suggest that PDGF causes a redistribution of EAAC1 from an intracellular compartment to the cell surface. These effects of PDGF were accompanied by a 35-fold increase in PI3-K activity and were blocked by the PI3-K inhibitors, wortmannin and LY 294002, but not by an inhibitor of protein kinase C. Other growth factors, including insulin, nerve growth factor, and epidermal growth factor had no effect on glutamate transport nor did they increase PI3-K activity. These studies suggest that, as is observed for insulin-mediated translocation of GLUT4, EAAC1 cell surface expression can be rapidly increased by PDGF through activation of PI3-K. It is possible that this PDGF-mediated increase in EAAC1 activity may contribute to the previously demonstrated neuroprotective effects of PDGF.
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PMID:Platelet-derived growth factor rapidly increases activity and cell surface expression of the EAAC1 subtype of glutamate transporter through activation of phosphatidylinositol 3-kinase. 1067 71

We have shown recently that the multifunctional growth factor, scatter factor/hepatocyte growth factor (SF/HGF), and its receptor c-met enhance the malignancy of human glioblastoma through an autocrine stimulatory loop (R. Abounader et al., J. Natl. Cancer Inst., 91: 1548-1556, 1999). This report examines the effects of SF/HGF:c-met signaling on human glioma cell responses to DNA-damaging agents. Pretreating U373 human glioblastoma cells with recombinant SF/HGF partially abrogated their cytotoxic responses to gamma irradiation, cisplatin, camptothecin, Adriamycin, and Taxol in vitro. This cytoprotective effect of SF/HGF occurred at least in part through an inhibition of apoptosis, as evidenced by diminished terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling index and reduced DNA laddering. Anti-c-met U1/ribozyme gene transfer inhibited the ability of SF/HGF to protect against single-strand DNA breakage, DNA fragmentation, and glioblastoma cell death caused by DNA-damaging agents, demonstrating a requirement for c-met receptor function. Phosphorylation of the cell survival-promoting kinase Akt (protein kinase B) resulted from SF/HGF treatment of U373 cells, and both Akt phosphorylation and cell survival induced by SF/HGF were inhibited by phosphatidylinositol 3-kinase inhibitors but not by inhibitors of mitogen-activated protein kinase kinase or protein kinase C. Cytoprotection by SF/HGF in vitro was also inhibited by transient expression of dominant-negative Akt. Transgenic SF/HGF expression by intracranial 9L gliosarcomas reduced tumor cell sensitivity to gamma irradiation, confirming the cytoprotective effect of SF/HGF in vivo. These findings demonstrate that c-met receptor activation by SF/HGF protects certain glioblastoma cells from DNA-damaging agents by activating phosphoinositol 3-kinase-dependent and Akt-dependent antiapoptotic pathways.
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PMID:Scatter factor/hepatocyte growth factor protects against cytotoxic death in human glioblastoma via phosphatidylinositol 3-kinase- and AKT-dependent pathways. 1094 42

Glial fibrillary acidic protein (GFAP) is an intermediate filament (IF) protein expressed upon maturation of astrocytes and upregulated during reactive astrogliosis. Its expression is modulated by several growth factors and hormones. Although an upregulation of intracellular cAMP is required for the induction of GFAP expression in astrocytes, little information is available on other downstream factors of the signal transduction pathways involved in the regulation of its expression. In this communication, we identified phosphatidylinositol 3-kinase (PI 3-K) as a necessary enzyme for GFAP expression in rat C6 glioma cells. Use of the specific PI 3-K inhibitors wortmannin and LY294002 and transfection of C6 cells with a dominant negative PI 3-K construct, resulting in a decrease of the enzymatic activity of PI 3-K, inhibited the cAMP-dependent expression of GFAP. Furthermore, confocal laser scanning microscopy demonstrated that inhibition of the PI 3-K activity by LY294002 or wortmannin concomitant with induction of differentiation changes the cellular distribution leading to a pericentrosomal localization of GFAP and an altered cell shape lacking process formation. We conclude that the expression and cellular distribution of GFAP is mediated through a PI 3-K-dependent mechanism.
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PMID:Phosphatidylinositol 3-kinase activity is required for the expression of glial fibrillary acidic protein upon cAMP-dependent induction of differentiation in rat C6 glioma. 1120 24

Opiates, such as morphine, have been used extensively in the clinical management of pain due to their potent analgesic effect. Astrocytes, representing a major non-neuronal cell population in the CNS, contain opioid receptors that are actively involved in several brain functions. This study was designed to evaluate the effects by which morphine, a preferential mu-opioid receptor agonist, contributes to cytotoxicity of nitric oxide (NO) species, including NO and peroxynitrite (ONOO-), in primary rat neonatal astrocytes. Primary astrocytes isolated from the cerebral cortex of 1- to 2-day-old Sprague-Dawley rats were treated with morphine, naloxone, and 3-morpholinosydnonimine (SIN-1), a donor of peroxynitrite. Morphine significantly protected primary rat astrocytes from apoptosis mediated by sodium nitroprusside, an NO donor, and SIN-1 in a dose-dependent manner, whereas it did not in other types of cells including C6 glioma, RAW 264.7, and HL-60 cells. Moreover, naloxone antagonized the protective effects of morphine on SIN-1-induced apoptosis. Morphine also inhibited the nuclear condensation and fragmentation of SIN-1-treated cells that was antagonized by naloxone pretreatment. The protective role of morphine in SIN-1-induced apoptosis was dependent on an intracellular antioxidant system such as GSH. Furthermore, the effects of morphine on SIN-1-induced cytotoxicity were prohibited by pretreatment with the G(i) protein inhibitor, pertussis toxin, and the phosphatidylinositol 3-kinase (PI3 kinase) inhibitors, wortmannin and LY294002. Taken together, these results suggest that morphine may protect primary rat astrocytes from apoptosis by NO species via the signaling cascades that involve both G protein and PI3 kinase.
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PMID:Protective effects of morphine in peroxynitrite-induced apoptosis of primary rat neonatal astrocytes: potential involvement of G protein and phosphatidylinositol 3-kinase (PI3 kinase). 1127 62

Glial fibrillary acidic protein (GFAP) is expressed upon cAMP-mediated induction of differentiation of glial progenitor cells into type II astrocytes. The protein is regulated by hormones, growth factors and cytokines but the signal transduction pathways involved in the regulation of GFAP expression are largely unknown. Specific protein kinase inhibitors were used to study their effect on the expression of GFAP in rat C6 glioma cells. Herbimycin A, a selective protein tyrosine kinase inhibitor, reduced GFAP mRNA and protein expression upon cAMP analog or beta-adrenergic receptor-mediated induction of differentiation. The latter inhibitor attenuated the elevation of cAMP by adenylate cyclase and abolished the activity of phosphatidylinositol 3-kinase (PI 3-K). These data indicate that GFAP expression is regulated by protein tyrosine phosphorylations, modulating the cAMP concentration and PI 3-K activity in C6 glioma cells.
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PMID:Protein tyrosine kinase-dependent regulation of adenylate cyclase and phosphatidylinositol 3-kinase activates the expression of glial fibrillary acidic protein upon induction of differentiation in rat c6 glioma. 1140 34

The formation of human malignant gliomas is thought to involve the accumulation of multiple genetic alterations. To define the function of specific alterations in glioma formation, we serially introduced genetic alterations functionally equivalent to those noted in human malignant gliomas into normal human astrocytes (NHAs). We then monitored the ability of each of these alterations to contribute to the growth of otherwise genetically stable NHAs into intracranial malignant gliomas. Using this model, we show that expression of human telomerase catalytic component (hTERT), but not E7-mediated inactivation of pRb or E6/E7-mediated inactivation of p53/pRb, was sufficient to initiate the tumorigenic process by circumventing cellular senescence in astrocytes. hTERT expression, even in combination with inactivation of p53/pRb, did not transform astrocytes. These alterations together, however, cooperated with ras pathway activation (initiated by expression of mutant H-Ras), but not with phosphatidylinositol 3-kinase pathway activation (initiated by expression of myristoylated Akt) or epidermal growth factor receptor activation, to allow for the formation of intracranial tumors strongly resembling p53/pRb pathway-deficient, telomerase-positive, ras-activated human grade III anaplastic astrocytomas. These results identify four pathways as key in the development of human anaplastic astrocytomas.
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PMID:Formation of intracranial tumors by genetically modified human astrocytes defines four pathways critical in the development of human anaplastic astrocytoma. 1143 23


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