Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0017636 (glioblastoma)
 18,345 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Protein kinase C (PKC), an enzyme involved in signal transduction, responds to diacyl glycerol and also to phorbol ester, a ligand analogous to diacyl glycerol. We have studied the expression of the major isoforms (alpha, beta I, beta II, and gamma) in eight human glioblastoma cell lines. In all eight lines, PKC-alpha mRNA and protein were expressed. In none of the eight did a probe for PKC-beta I and -beta II mRNA give positive results nor were Western blots for PKC-beta II positive. The half-life for PKC alpha mRNA was approximately 16 h and levels of the mRNA were increased slightly following addition of phorbol myristate acetate (PMA) or transforming growth factor-beta (TGF beta). PKC-gamma was present in most of the glioblastomas. In cell line A172, 82% of the PKC-alpha was present in the cytosol with the remainder evenly divided between plasma membrane and nucleus. Thirty minutes after addition of PMA, 33% of the total original protein was in the plasma membrane and 48% in the nuclear fraction. By 21 h, no PKC-alpha was recovered from any fraction. PKC-gamma was also down-regulated in the presence of PMA, but there was no evidence for translocation to the plasma membrane or nuclear fraction. In a more detailed study, translocation of PKC-alpha in the presence of PMA was complete by 10 min, and a major decrease in the PKC translocated to the plasma-membrane fraction occurred some time between 2 and 4 h after PMA addition, while a major decrease in the translocated nuclear fraction occurred some time after 6 h. cAMP alone had no effect on the PKC alpha protein level or distribution, nor did it alter the translocation and down-regulation due to PMA exposure. In these studies the level of PKC-alpha mRNA in tumors was similar to that in normal glial cells.
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PMID:Protein kinase C isoforms in human glioblastoma cells. 133 68

Synthesis and metabolism of the epidermal growth factor (EGF) receptor are extensively regulated to modulate cellular responses to ligand. To study regulation of EGF receptor gene expression, the 5' region of the gene was isolated from a human placental genomic library. A 5' proximal 1.1-kilobase fragment (-1100 to -19 relative to the ATG translation start site) and subfragments of this were subcloned in both forward and reverse orientations into the luciferase expression vector pSVOAL delta 5' and transfected into human cell lines. Luciferase activity was stimulated by treatment of transfected HeLa cells with EGF, 12-O-tetradecanoylphorbol 13-acetate (TPA), (Bu)2 cAMP, retinoic acid, and dexamethasone. Deletion analysis indicated full retention of activity after removal of the -1100 to -485 region (-485 to -19 fragment), but a 5-fold reduction in activity on removal of the -485 to -153 region (-153 to -19 fragment). Despite a reduction in basal activity, the proximal 134-basepair fragment retained responses to all inducers. Additivity was observed in response to maximal concentrations of TPA plus retinoic acid and of TPA plus (Bu)2 cAMP; the response to a combination of four inducers exceeded that to the RSV-LTR strong promoter. Differences in stimulated responses were observed in various recipients, with hepatoma HepG2 cells lacking responses to (Bu)2 cAMP and glioblastoma T98G cells lacking responses to EGF and TPA. These results indicate that a 134-basepair DNA fragment closely adjacent to the translation start site contains elements responsible for directing basal and stimulated expression of the EGF receptor gene.
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PMID:Regulation of epidermal growth factor receptor gene expression. 254 Apr 31

We have studied the regulation by glucocorticoids and dibutyryl cAMP of the amounts of urokinase-type plasminogen activator (u-PA), tissue-type plasminogen activator (t-PA) and a Mr approximately 54000 plasminogen activator inhibitor accumulated in serum-free conditioned culture fluid by a human fibrosarcoma, a human glioblastoma and a human melanoma cell line (HT-1080, UCT/gl-1 and Bowes). For the quantitation of u-PA and t-PA, we used sandwich-type ELISA with a combination of polyclonal and monoclonal antibodies. For an estimation of variations in the amount of the inhibitor, we used sodium dodecyl sulphate-polyacrylamide gel electrophoresis followed by Coomassie blue staining of conditioned culture fluid proteins, the inhibitor protein band being identified by its selective removal by passage of the conditioned culture fluids through a column with monoclonal antibodies against the inhibitor. The modulation of the 3 proteins by the hormonal agents varied greatly between the cell lines. The proteins were independently regulated, in the sense that the hormonal agents did not concomitantly change their levels in the direction expected either to increase or decrease total extracellular plasminogen activator activity. In conditioned culture fluids containing both t-PA and inhibitor, the two were present in the medium as a Mr approximately 120 000 complex. In contrast, no u-PA inhibitor complexes were found in conditioned culture fluid from any of the cell lines; this is likely to be due to the occurrence of u-PA in the culture fluid in the one-chain proenzyme form, which, unlike active u-PA, does not react with the inhibitor. These findings illustrate the complexity of the regulation of extracellular plasminogen activator activity, and imply that the presumed functional diversity of u-PA and t-PA may be related to their independent regulation.
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PMID:Hormonal regulation of extracellular plasminogen activators and Mr approximately 54,000 plasminogen activator inhibitor in human neoplastic cell lines, studied with monoclonal antibodies. 301 58

The brain creatine kinase (CKB) gene is expressed in a variety of tissues with highest expression seen in the brain. We have previously shown in primary rat brain cell cultures that CKB mRNA levels are high in oligodendrocytes and astrocytes and low in neurons (Molloy et al.: J Neurochem 59:1925-1932, 1992). In this report we show that treatment of human U87 glioblastoma cells with forskolin and IBMX, to elevate intracellular cAMP, induces expression of CKB mRNA from the transiently transfected rat CKB gene by 14-fold and also increases expression from the endogenous human CKB gene. This induction of CKB mRNA i) is due to increased transcription; ii) occurs rapidly (with maximal induction after 6 hr; iii) requires the activity of protein kinase A (PKA), but iv) does not require de novo protein synthesis and, in fact, is superinduced in the presence of cycloheximide. Given the role of oligodendrocytes in the energy-demanding process of myelination and of astrocytes in ion transport, these results have physiological significance, since they suggest that changes in cellular energy requirements in the brain during events, such as glial cell differentiation and increased neuronal activity, may in part be met by a cAMP-mediated modulation of CKB gene expression. Of particular importance is the possible modulation of CKB gene expression during myelinogenesis, since oligodendrocyte differentiation has been shown previously to be stimulated by increases in cAMP.
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PMID:Transcription of the brain creatine kinase gene in glial cells is modulated by cyclic AMP-dependent protein kinase. 752 18

Transcription factor AP-2 has been implicated as an important regulator of gene expression during vertebrate embryogenesis. We report here the cDNA cloning and analysis of mouse embryonic mRNA splice variants encoding four AP-2 isoforms. Isoform 1 is the homolog of the previously known human (HeLa) AP-2. The three new AP-2 isoforms all share the same DNA binding/dimerization domain as isoform 1 but either lack the proline-rich transcriptional activation domain encoded by exon 2 (isoform 2) or have different amino-termini encoded by two previously unknown alternative first coding exons for AP-2 (isoforms 3 and 4). All four AP-2 mRNA variants are present at significant levels between Days 11.5 and 17.5 of mouse embryogenesis. Variants 1, 3, and 4 show qualitatively but not quantitatively similar restricted expression patterns in 8.5-12.5 dpc embryos examined by in situ hybridization. At mid-embryogenesis, variant 3 is the major AP-2 mRNA species in the nervous system and in total embryo RNA but is less prevalent than variants 1 and 4 in the epidermis. The four mRNAs are all induced, although unequally, during differentiation of P19 cells into neural cell types and by cAMP stimulation of primary astrocytes. Variants 1-3 are coexpressed in different ratios in HeLa cells and in three human glioblastoma cell lines. These findings reveal that transcriptional regulation by AP-2 is likely to be more complex than previously assumed given the potential for multiple AP-2 homo- and heterodimeric DNA binding forms.
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PMID:Alternative mRNAs encode multiple isoforms of transcription factor AP-2 during murine embryogenesis. 775 Jun 31

Little is known about the pharmacology or cell biology of human bombesin (Bn) receptors, because they are usually present at low levels and both subtypes are frequently present in the same tissues. Human gastrin-releasing peptide (GRP) receptors (huGRP-R) and human neuromedin B (NMB) receptors (huNMB-R) were stably transfected into BALB/3T3 fibroblasts. Both receptor types were glycosylated, with 35% of the huGRP-R and 38% of the huNMB-R representing carbohydrate residues. The extent of glycosylation of the transfected huGRP-R was the same as that seen in the human glioblastoma cell line U-118. Radiolabeled agonist ligands were rapidly internalized, whereas noninternalized ligand readily dissociated in a temperature-dependent fashion. The affinities of various agonists for binding to the huGRP-R were Bn (Ki = 1.4 +/- 0.2 nM) = 4 x GRP = 300 x NMB. In contrast, affinities for the huNMB-R were NMB (Ki = 8.1 +/- 5.2 nM) = 4 x Bn = 600 x GRP. [F5-D-Phe6,D-Ala11]Bn(6-13)methyl ester was the most potent huGRP-R antagonist, whereas D-Nal-Cys-Tyr-D-Trp-Lys-Val-Cys-Nal-NH2 was the most potent huNMB-R antagonist. Agonist binding to either receptor type caused activation of phospholipase C and increased cellular [3H]inositol phosphate levels. GRP was potent at increasing [3H]inositol phosphate generation in cells expressing the huGRP-R (EC50 = 13.6 +/- 1.3 nM), whereas NMB was similarly potent when acting upon cells expressing the huNMB-R (EC50 = 9.3 +/- 1.4 nM). However, neither receptor type, when stimulated with agonist, caused an increase in cAMP levels. These data show that stably transfected huGRP-R exhibit similar pharmacology for agonists and antagonists, are appropriately glycosylated, and function similarly with respect to their ability to alter biological activity, compared with natively expressed receptors. Minimal native huNMB-R data are available for comparison, but in general the huNMB-R is similar to the rat NMB receptor in its pharmacology and cell biology.
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PMID:Expression and characterization of cloned human bombesin receptors. 783 18

We previously reported the identification of human CAP, a protein that is related to the Saccharomyces cerevisiae and Schizosaccharomyces pombe adenylyl cyclase-associated CAP proteins. The two yeast CAP proteins have similar functions: the N-terminal domains are required for the normal function of adenylyl cyclase, while loss of the C-terminal domains result in morphological and nutritional defects that are unrelated to the cAMP pathways. We have amplified and cloned cDNAs from a human glioblastoma library that encode a second CAP-related protein, CAP2. The human CAP and CAP2 proteins are 64% identical. Expression of either human CAP or CAP2 in S. cerevisiae cap- strains suppresses phenotypes associated with deletion of the C-terminal domain of CAP, but does not restore hyper-activation of adenylyl cyclase by RAS2val19. Similarly, expression of either human CAP or CAP2 in S. pombe cap- strains suppresses the morphological and temperature-sensitive phenotypes associated with deletion of the C-terminal domain of CAP in this yeast. In addition, expression of human CAP, but not CAP2, suppresses the propensity to sporulate due to deletion of the N-terminal domain of CAP in S. pombe. This latter observation suggests that human CAP restores normal adenylyl cyclase activity in S. pombe cap- cells. Thus, functional properties of both N-terminal and C-terminal domains are conserved between the human and S. pombe CAP proteins.
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PMID:Comparison of human CAP and CAP2, homologs of the yeast adenylyl cyclase-associated proteins. 796 7

We have used a tumorigenic glioblastoma cell line, SNB-19, as a model system to identify fucose-containing glycoprotein candidates for tumor suppressor function. Glycoproteins were analyzed after treatment with a variety of chemical differentiating agents by two-dimensional SDS-PAGE, followed by electroblotting and visualization using the fucose-specific lectin, Ulex europeaus I. Approximately 25 fucose-containing glycoproteins (FUCGLAPs) were routinely visualized in control extracts using 60-70 micrograms of protein per gel and staining with Vectastain ABC kits. Retinoic acid induced the most marked change in FUCGLAP expression, causing a fivefold increase in one FUCGLAP (M(r) = 125 kDa, pI = 6.6). Neither butyric acid, dibutyryl cAMP, nor combinations of these compounds gave a similar result. Using this model system and analytical approach, it should be possible to identify, isolate, and evaluate glycoprotein oligosaccharides for their tumor modulating capability.
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PMID:The identification of glioblastoma-associated, fucose-containing glycoproteins induced by retinoic acid. 808 41

Increasing evidence suggests that in mammals, astrocytes are a heterogenous family of cells all of which share certain properties, but differ in lineage, biochemical and functional aspects. It seems likely that glioblastomas, arising from glial precursors, may also represent a family of related but distinct cell types. We have examined the antigenic characteristics and differentiative potential of 7 different human glioblastoma cell lines in vitro. All the cell lines were labeled with a monoclonal antibody 7B11 which labels all classes of astrocytes and their precursors in the rat CNS. U138MG and Tm3 cells expressed antigens on their surfaces recognized by the monoclonal antibodies A2B5 and HNK-1. When grown in serum-free medium in the presence of cAMP and theophylline, U138MG cells assumed a process-bearing morphology and some cells expressed the Gal-C antigen specific for oligodendrocytes. Under identical conditions, Tm3 cells converted to process-bearing cells, some of which expressed glial fibrillary acidic protein (GFAP) specific for astrocytes. Other cell lines with similar antigenic characteristics did not respond similarly to cAMP and theophylline. Finally, A2781 cells were GFAP immunoreactive and unlabeled by either A2B5 or HNK-1 antibodies. These observations suggest that individual glioblastoma cell lines may be derived from distinct glial precursor cells in the vertebrate CNS.
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PMID:Antigenic and differentiative heterogeneity among human glioblastomas. 838 1

We have established a highly sensitive functional screen for the isolation of cDNAs encoding cAMP phosphodiesterases (PDEs) by complementation of defects in a Saccharomyces cerevisiae strain lacking both endogenous cAMP PDE genes, PDE1 and PDE2. Three groups of cDNAs corresponding to three distinct human genes encoding cAMP-specific PDEs were isolated from a human glioblastoma cDNA library using this functional screen. Two of these genes are closely related to the Drosophila dunce cAMP-specific PDE. The third gene, which we named HCP1, encoded a novel cAMP-specific PDE. HCP1 has an amino acid sequence related to the sequences of the catalytic domains of all cyclic nucleotide PDEs. HCP1 is a high affinity cAMP-specific PDE (Km = 0.2 microM) that does not share other properties of the cAMP-specific PDE family, i.e. extensive sequence homology to the Drosophila dunce cAMP PDE and sensitivity to rolipram and R020-1724. The PDE activity of HCP1 is not sensitive to cGMP or other inhibitors of the cGMP-inhibitable PDEs, such as milrinone. The biochemical and pharmacological properties of HCP1 suggest that it is a member of a previously undiscovered cyclic nucleotide PDE family. Northern blot analysis indicates that high levels of HCP1 mRNA are present in human skeletal muscle.
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PMID:Isolation and characterization of a previously undetected human cAMP phosphodiesterase by complementation of cAMP phosphodiesterase-deficient Saccharomyces cerevisiae. 838 65


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