Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phosphatidylserine (PS) synthesis was studied in glioma C6 cells with [14C]serine and in the presence or absence of the phorbol ester, 12-O-tetradecanoylphorbol 13-acetate (TPA). It was found that incubation of the cells with 10 nM or 100 nM TPA for 1 h inhibited PS formation by 30% and 60%, respectively. Long-term (18 h) treatment of the cells with 100 nM TPA diminished PS formation and further addition of TPA to down-regulated cells did not affect PS synthesis. The data show that the changes in PS synthesis can be associated with alterations in morphology of cell and the actin cytoskeleton organization. The role of protein kinase C in this process is discussed.
Biochem Mol Biol Int 1995 Jul
PMID:Phosphatidylserine synthesis in phorbol ester treated glioma C6 cells. 754 66

1. The transcriptional regulation of the rat brain L-type calcium channel alpha 1D subunit (RB alpha 1D) gene was investigated using NG108-15 neuroblastoma-glioma cells. 2. Differentiation of NG108-15 cells in the presence of prostaglandin E1 or retinoic acid resulted in the appearance of mRNA encoding the RB alpha 1D subunit detected using Northern blot analysis. 3. A rat genomic DNA library was screened, and a 15.2-kb clone was isolated and partially sequenced which included part of the 5' upstream sequence through the initial part of intron 2 of the RB alpha 1D gene. 4. Deletion analysis, using a CAT reporter gene and transfected NG108-15 cells, revealed that the 1.2-kb 5'-upstream sequence from the RB alpha 1D gene contains cis-acting positive and negative regulatory elements. A deletion of the 3' end of exon 1 also suggested the presence of regulatory elements in the first exon. 5. DNase footprinting of exon 1 of the RB alpha 1D gene revealed two regions protected from digestion by specific protein binding, and the second region included an (ATG)7 trinucleotide repeat sequence. Electrophoretic mobility shift assays confirmed nuclear protein(s) binding to the (ATG)7 sequence. 6. The (ATG)7 sequence functions as a enhancer when linked to a thymidine kinase promoter and a CAT reporter gene. 7. These results provide the initial description of the transcriptional regulation of the RB alpha 1D gene and identify a novel enhancer that consists of an (ATG)7 trinucleotide repeat sequence.
Cell Mol Neurobiol 1995 Jun
PMID:Transcriptional regulation of the neuronal L-type calcium channel alpha 1D subunit gene. 755 31

1. The aim of this study was to elucidate if the K+ uptake was higher in cultured human glioma cells than in cells from other malignant tumors and to analyze the importance of membrane potential and K+ channels for the uptake. 2. K+ transport properties were studied with the isotopes 42K and the K-analogue 201Tl. 3. Comparison with cultured cells from other malignant tumors showed that the specific steady-state accumulation of Tl+ was significantly higher in glioma cells (U-251MG and Tp-378MG). 4. In Ringer's solution at 37 degrees C the rates of K+ and Tl+ uptake were both inhibited by about 55% in ouabain and 60% in furosemide, bumetanide, or Na(+)- or Cl(-)-free medium. This indicated that the routes for K+ and Tl+ uptake were similar and due to Na,K-ATPase-dependent transport and to Na-K-Cl cotransport. 5. About 10% of the uptake was neither ouabain nor bumetanide sensitive. Ba2+, which is known to block inward-rectifying K+ channels and to depolarize glial cells, and other K+ channel blockers (Cs+ and bupivacaine), had no effect on Tl+ uptake. 6. Metabolic inhibition with dinitrophenol reduced the uptake rate to 17%. 7. The washout of Tl+ was unaffected by bumetanide and K+ channel blockers, but dinitrophenol caused a transient increase of 75%, an effect which persisted in the presence of K+ channel blockers. 8. It was concluded that the high specific K+ and Tl+ accumulation in cultured human glioma cells was due not to the presence of inwardly rectifying K+ channels or other identified K+ channels, but to Na,K-ATPase dependent transport and Na-K-Cl cotransport.
Cell Mol Neurobiol 1995 Jun
PMID:Mechanism of high K+ and Tl+ uptake in cultured human glioma cells. 755 34

Expression of vascular endothelial growth factor (VEGF), an endothelial cell-specific mitogen and a potent angiogenic factor, is upregulated in response to a hypoxic or hypoglycemic stress. Here we show that the increase in steady-state levels of VEGF mRNA is partly due to transcriptional activation but mostly due to increase in mRNA stability. Both oxygen and glucose deficiencies result in extension of the VEGF mRNA half-life in a protein synthesis-dependent manner. Viewing VEGF as a stress-induced gene, we compared its mode of regulation with that of other stress-induced genes. Results showed that under nonstressed conditions, VEGF shares with the glucose transporter GLUT-1 a relatively short half-life (0.64 and 0.52 h, respectively), which is extended fourfold and more than eightfold, respectively, when cells are deprived of either oxygen or glucose. In contrast, the mRNAs of another hypoxia-inducible and hypoglycemia-inducible gene, grp78, as well as that of HSP70, were not stabilized by these metabolic insults. To show that VEGF and GLUT-1 are coinduced in differentially stressed microenvironments, multicell spheroids representing a clonal population of glioma cells in which each cell layer is differentially stressed were analyzed by in situ hybridization. Cellular microenvironments conducive to induction of VEGF and GLUT-1 were completely coincidental. These findings show that two different consequences of tissue ischemia, namely, hypoxia and glucose deprivation, induce VEGF and GLUT-1 expression by similar mechanisms. These proteins function, in turn, to satisfy the tissue needs through expanding its vasculature and improving its glucose utilization, respectively.
Mol Cell Biol 1995 Oct
PMID:Stabilization of vascular endothelial growth factor mRNA by hypoxia and hypoglycemia and coregulation with other ischemia-induced genes. 756 86

We have been studying the molecular mechanism of neuronal differentiation through which the multipotent precursor becomes limited to the final transmitter phenotype. Here we focused on the role of the 5' proximal regulatory cassette (-190; +53 bp) of the rat enkephalin (rENK) gene in the developmental regulation of the enkephalin phenotype. Several well characterized cis-elements, including AP2, CREB, NF1, and NFkB, reside on this region of the rENK gene. These motifs were sufficient to confer activity-dependent expression of the gene during neurodifferentiation when it was tested using transient transfection assays of primary developing spinal cord neurons treated with tetrodotoxin (TTX). This region was then used as a DNA probe in mobility shift assays, with nuclear proteins derived from phenotypically and ontogenetically distinct brain regions. Only a few low abundance protein-DNA complexes were detected and only with nuclear proteins derived from developing but not from adult brain. The spatiotemporal pattern of these complexes did not show correlation with enkephalin expression which was assessed by RT-PCR. We employed synthetic probes corresponding to consensus as well as ENK-specific sequences of the individual motifs to identify the nature of the observed bands. Although both consensus NF1 and enkCRE1(NF1) formed complexes with nuclear proteins derived from the striatum and cortex at various ages, the appearance of the bands was not correlated with ENK expression. Surprisingly, no complexes were detected if other ENK-specific motifs were used as probes. We also tested nuclear extracts derived from forskolin-induced and control C6 glioma cells, again using the whole proximal regulatory cassette as well as individual motifs. These experiments showed the formation of elaborate protein-DNA bands. There was no direct correlation between the appearance of bands and forskolin-induced ENK expression. Unexpectedly, all ENK-specific motifs formed specific and highly abundant protein-DNA complexes when nuclear extracts from the human tumor cell line (HeLa), which does not express ENK, were used. Based on these observations, we concluded that: 1. Interactions between the proximal regulatory cassette and additional probably far distant regions of the rENK gene and their binding proteins may be necessary to confer developmentally regulated, cell-specific expression of the ENK gene; and 2. Inducibility of the gene by common cis-elements can be governed by this region; however, the cell-specificity of the induction remains elusive.
Mol Neurobiol
PMID:Protein-DNA interactions during phenotypic differentiation. 757 7

Using monoclonal antibodies against the RAR-alpha and RAR-beta retinoic receptors, we demonstrated that these receptors were present together in C6 glioma cells as two isoforms of 50 and 55 kDa. For RAR-beta, the 50 kDa isoform predominated (60 to 80% of the total of the two isoforms). After a treatment for 48 h with retinoic acid 10 microM, the 55 kDa form was enhanced, while no effect was observed either on RAR-alpha isoforms from C6 cells and on both RAR-alpha and RAR-beta forms from neuroblastoma SKN SH SY5Y used as a control. Using purified neuronal and glial rat brain nuclei, we showed that the 55 kDa isoform from RAR-beta predominated in glial cells. These results suggest that retinoic acid treatment of C6 cells led to a partial differentiation, the enhancement of the heavy form of RAR-beta being a marker of this phenomenon.
Biochem Mol Biol Int 1995 Aug
PMID:Study of retinoic acid effect upon retinoic acid receptors beta (RAR-beta) in C6 cultured glioma cells. 758 Oct 5

The hydrolysis of the dimethyl ester of [1,4-14C]succinic acid and/or [2,3-14C]succinic acid was measured in homogenates of rat pancreatic islets, liver, jejunum, brain, BC3H1 mouse myocytes, NG108-19 mouse neuroblastoma x rat glioma hybrid cells, and Caco-2 human colon adenocarcinoma cells. The specific activity of the enzyme was much higher in liver, jejunum, and Caco-2 cells than in the other cell types. The affinity of the enzyme for succinic acid dimethyl ester (SAD) was also much higher in liver than in islet homogenates. In the latter case, both particulate and cytosolic activity were observed upon subcellular fractionation. The activity found in islet homogenates was commensurate with the rate of SAD hydrolysis in intact cells. While the intracellular pool of acidic metabolites generated from SAD remained fairly stable over a 15- to 120-min incubation and was mainly located in the cytosolic compartment, the amount of acidic metabolites released in the extracellular milieu progressively increased with the length of incubation. Such metabolites included both monocarboxylic and dicarboxylic acids, the latter consisting mainly of succinic acid and, to a much lesser extent, of fumaric acid and malic acid. However, at variance with SAD, succinic acid failed to be taken up by intact islets. There was no close parallelism between the specific activity of the SAD esterase and the extent of SAD utilization in distinct cell types.
Biochem Mol Med 1995 Aug
PMID:Hydrolysis of succinic acid dimethyl ester in rat pancreatic islets. 758 70

We have detected a tyrosine-phosphorylated 200-kDa protein in two human tumor cell lines, A1235 glioma and A172 glioblastoma. The protein is an integral plasma membrane sialoglycoprotein with tyrosine kinase activity. The interesting characteristic of this protein (gp200) is that it is recognized by a number of monoclonal and polyclonal antibodies to the 170-kDa epidermal-growth-factor (EGF) receptor; however, it lacks detectable EGF-binding activity. gp200 differs from three other EGF-receptor-related proteins, erb-B-2, erb-B-3 and erb-B-4 gene products, and hence appears to be yet another member of the EGF-receptor family of proteins. This is further strengthened by the fact that both gp200 and the EGF receptor contain a common epitope which is recognized by an anti-peptide IgG to the beta-type platelet-derived-growth-factor (PDGF) receptor. Our previous studies [Bishayee, S., Majumdar, S., Scher, C.D. & Khan, S. (1988) Mol. Cell. Biol. 8, 3696-3702] have demonstrated that this epitope in the PDGF receptor is highly susceptible to the phosphorylation state of the receptor and that such a conformational change appears to be important in biological message transmission. The expression of gp200, which appears to have tyrosine kinase activity and is immunologically related to the EGF receptor in tumor cells, suggests its possible involvement in cell growth.
 ...
PMID:Characterization of a novel epidermal-growth-factor-receptor-related 200-kDa tyrosine kinase in tumor cells. 760 Nov 58

The DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) has been implicated in resistance of human brain tumors to alkylating agents. We observed that 14 human medulloblastoma- and glioma-derived cell lines differ in sensitivity to the methylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), as shown by their 28-fold range in 10% survival dose (LD10). By using the substrate analogue inhibitor O6-benzylguanine (O6-BG), we showed that the contribution of MGMT to resistance varies widely, as evidenced by 3- to 30-fold reductions in LD10 among the lines, and varies up to 20-fold among subpopulations of individual lines. Importantly, variability in resistance, manifested as a 20-fold range in LD10, persists after measurable MGMT is eliminated, disclosing differential contributions of other resistance mechanisms to survival. Cells exposed to MNNG while suspended in growth medium are more resistant than cells alkylated as subconfluent monolayers, and MGMT accounts for a smaller proportion of their resistance. Notably, the MGMT content of the lines is not statistically correlated with MNNG resistance or with potentiation of killing by O6-BG, even though MGMT is a biochemically demonstrated determinant of resistance. In contrast, the same lines vary less in resistance to the ethylating agent N-ethylnitrosourea (ENU), and MGMT makes only a small contribution to resistance. Our results strongly indicate that resistance to both MNNG and ENU is multifactorial.
Mol Carcinog 1995 Jun
PMID:Contribution of O6-methylguanine-DNA methyltransferase to monofunctional alkylating-agent resistance in human brain tumor-derived cell lines. 760 82

To assess the possible role of the DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) in resistance of brain neoplasms to the clinically important chloroethylating agent 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), we quantitated MGMT activity, BCNU survival, and the effect of ablating MGMT activity on the sensitivity of 14 human medulloblastoma- and glioma-derived cell lines. BCNU resistance, measured as 10% survival dose (LD10), differed eightfold among the lines. Elimination of measurable MGMT activity with the substrate analogue inhibitor O6-benzylguanine (O6-BG) revealed a variable but limited contribution of MGMT to survival. In no case did O6-BG reduce LD10 by more than 3.4-fold. In contrast, O6-BG reduced the LD10 for N-methyl-N'-nitro-N-nitrosoguanidine up to 31-fold in the same cell lines (Bobola MS, Blank A, Berger MS, Silber JR, Mol Carcinog 13:70-80, 1995). Variability in BCNU survival, manifested as a sevenfold range of LD10, persists after measurable MGMT was eliminated, indicating that another mechanism or mechanisms is operating to limit cytotoxicity. Cells alkylated while suspended in growth medium are more resistant to BCNU and display less dependence on MGMT than cells treated while proliferating on a plastic substratum. When alkylated in suspension, most of the lines are either unresponsive to O6-BG or contain a subpopulation that did not respond to O6-BG. Our results demonstrate that BCNU resistance is multifactorial and that MGMT makes a modest contribution to resistance in our lines.
Mol Carcinog 1995 Jun
PMID:Contribution of O6-methylguanine-DNA methyltransferase to resistance to 1,3-(2-chloroethyl)-1-nitrosourea in human brain tumor-derived cell lines. 760 83


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