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)

Hexokinase plays a key role in regulating cell energy metabolism. Hexokinase is mainly particulate, bound to the mitochondrial outer membrane in brain and tumour cells. We hypothesized that the intracellular pH (pH1) controls the intracellular distribution of hexokinase. Using the SNB-19 glioma cell line, pH1 variations were imposed by incubating cells in a high-K+ medium at different pH values containing specific ionophores (nigericin and valinomycin), without affecting cell viability. Subcellular fractions of cell homogenates were analysed for hexokinase activity. Imposed pH1 changes were verified microspectrofluorimetrically by using the pH1-sensitive probe SNARF-1-AM (seminaphtho-rhodafluor-1-acetoxymethyl ester). Imposition of an acidic pH1 for 30 min strongly decreased the particulate/total hexokinase ratio, from 63% in the control sample to 31%. Conversely, when a basic pH1, was imposed, the particulate/total hexokinase ratio increased to 80%. The glycolytic parameters, namely lactate/pyruvate ratio, glucose 6-phosphate and ATP levels, were measured concomitantly. Lactate/pyruvate ratio and ATP level were both markedly decreased by acidic pH1 and increased by basic pH1. Conversely, the glucose 6-phosphate level was increased by acidic pH1 and decreased by basic pH1. To demonstrate that the change of hexokinase distribution was not due to altered metabolite levels of glycolysis, a pH1 was imposed for a 5 min incubation time. Modification of the hexokinase distribution was similar to that noted after a 30 min incubation, whereas metabolite levels of glycolysis were not affected. These results provide evidence that the intracellular distribution of hexokinase is highly sensitive to variations of the pH1, and regulates hexokinase activity.
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PMID:Intracellular pH governs the subcellular distribution of hexokinase in a glioma cell line. 861 Nov 81

In vivo phosphorylation of the five histone H1 variants H1a-H1e including H1(0) in NIH 3T3 mouse fibroblasts was examined during the cell cycle by using a combination of HPLC techniques and conventional AU gel electrophoresis. Phosphorylation starts during the late G1 phase and increases throughout the S phase. In the late S phase, the H1 variants exist as a combination of molecules containing 0 or 1 (H1a, H1c), 0-2 (H1d), or 0-3 (H1b, H1e) phosphate groups with a share of unphosphorylated protein ranging between 35% and 75%, according to the particular subtype. Pulse-chase experiments show that phosphorylation during the S phase is a dynamic phosphorylation process with a limited phosphorylation maximum. In most H1 subtypes, phosphorylation occurs very rapidly at the G2/M transition with only small amounts of intermediate phosphorylated molecules. Phosphorylation of mouse H1c, however, occurs stepwise during this transition. Phosphorylated mouse histone subtypes from cells in mitosis contain four phosphate groups in the case of H1a, H1c, and H1e and five in the case of H1b and H1d. Comparison of the mouse phosphorylation pattern to that in rat C-6 glioma cells showed differences for H1e and H1d. By comparing the different phosphorylation patterns of the individual H1 variants during the cell cycle, we were able to classify the H1 histones into subtypes with low (H1a, H1c, H1(0)) and high (H1b, H1d, H1e) phosphorylation levels.
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PMID:In vivo phosphorylation of histone H1 variants during the cell cycle. 863 56

Observation that the G protein-coupled P2U receptor (P2Y2 receptor) is activated by UTP as well as ATP provided the first indication that a class of uridine nucleotide-responsive receptors might exist. This hypothesis was confirmed by our identification of a uridine nucleotide-specific receptor on C6-2B rat glioma cells and by the recent cloning of two uridine nucleotide-responsive receptors, the P2Y6 receptor [J. Biol. Chem. 270:26152-26158 (1995)] and the P2Y4 receptor [J. Biol. Chem. 270:30849-30852 (1995) and J. Biol. Chem. 270:30845-30848 (1995)]. The relative nucleotide selectivities of these uridine nucleotide-activated receptors have not been established. Therefore, we cloned and expressed the P2Y6 and P2Y4 receptors in 1321N1 human astrocytoma cells and compared their relative selectivities for UDP, UTP, and other uridine and adenine nucleotides with that of the P2Y2 receptor expressed in the same cells. These comparisons were made by measuring inositol phosphate accumulation under conditions in which the initial purity and stability of agonists were rigidly ensured and quantitatively assessed. The data indicate that the P2Y2 receptor is activated with similar potencies by ATP and UTP but not by ADP or UDP; the P2Y6 receptor is activated most potently by UDP but weakly by UTP, ATP, and ADP; and the P2Y4 receptor is activated most potently by UTP, less potently by ATP, and not at all by nucleotide diphosphates. Furthermore, the P2Y6 receptor, which displays a uridine nucleotide selectivity essentially identical to that of the uridine nucleotide-specific receptor in C6-2B cells, was shown to be natively expressed in C6-2B cells and to account for the uridine nucleotide responses originally identified in these cells. These results define the uridine nucleotide selectivity of three phospholipase C-linked receptors: a receptor that is selectively activated by UDP (P2Y6 receptor), selectively activated by UTP (P2Y4 receptor), and activated by UTP and ATP but not by diphosphate nucleotides (P2Y2 receptor).
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PMID:Uridine nucleotide selectivity of three phospholipase C-activating P2 receptors: identification of a UDP-selective, a UTP-selective, and an ATP- and UTP-specific receptor. 870 Jan 27

1. The coding sequence of the P2Y1-purinoceptor was cloned from a human genomic library. 2. The open reading frame encodes a protein of 373 amino acids that is 83% identical to the previously cloned chick and turkey P2Y1-purinoceptor and is > or = 95% homologous to the recently cloned rat, mouse, and bovine P2Y1-purinoceptors. 3. The human P2Y1-purinoceptor was stably expressed in 1321N1 human astrocytoma cells using a retroviral vector. Although the P2Y1-purinoceptor agonist, 2MeSATP, had no effect on inositol phosphate accumulation in cells infected with the P2Y1-purinoceptor virus. No effect of 2MeSATP on cyclic AMP accumulation was observed in P2Y1-receptor-expressing 1321N1 cells. 4. The pharmacological selectively of 18 purinoceptor agonists was established for the expressed human P2Y1-purinoceptor. 2MeSATp was more potent than ATP but less potent than 2MeSADP. ADP also was more potent than ATP. A similar maximal effect was observed with most agonists tested. However, alpha, beta-MeATP had no effect and 3'-NH2-3'-deoxyATP and A2P4 were partial agonists. The order of potency of agonists for activation of the turkey P2Y1-purinoceptor, also stably expressed in 1321N1 cells, was identical to that observed for the human P2Y1-purinoceptor. 5. C6 glioma cells express a P2Y-purinoceptor that inhibits adenylyl cyclase but does not activate phospholipase C. Expression of the human P2Y1-purinoceptor in C6 cells conferred 2MeSATP-stimulated inositol lipid hydrolysis to these cells. The phospholipase C-activating human P2Y1-purinoceptor could be delineated from the endogenous P2Y-purinoceptor of C6 glioma cells by use of the P2-purinoceptor antagonist, PPADS, which blocks the P2Y1-purinoceptor but does not block the endogenous P2Y-purinoceptor of C6 cells. P2-purinoceptor agonists also exhibited differential selectivities for activation of these two P2Y-purinoceptors.
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PMID:Second messenger cascade specificity and pharmacological selectivity of the human P2Y1-purinoceptor. 873 91

In the present study we demonstrate that the glycolysis of the tumour 9L glioma, in vivo, may be manipulated with ketamine/xylazine combinations of anaesthetics. Xylazine alone or in combination with ketamine causes hyperglycaemia which is enhanced by glucose injections. Intracellular tumour pH is acidified when glucose is administered with ketamine/xylazine. However, the combination of inorganic phosphate and insulin with ketamine/xylazine and glucose caused an alkaline shift in the tumour pH as measured by 31P NMR. The anaesthetic combination of ketamine/acepromazine did not produce alterations in blood glucose or in tumour pH status as detected by 31P NMR spectroscopy. These results demonstrate dramatic effects of ketamine/xylazine on the acidification or alkalinisation of the cells of 9L glioma. These altered metabolic states are of potential therapeutic importance. The choice of xylazine alone would be useful for chemotherapy and hyperthermia modalities, both known to be dependent upon glucose metabolism and resultant acidification.
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PMID:The importance of choice of anaesthetics in studying radiation effects in the 9L rat glioma. 876 85

The role played by endothelin-1 and intercellular communication mediated by gap junctions in the regulation of glucose disposal by astrocytes has been studied in primary culture. Endothelin-1 increased glucose uptake by astrocytes as did one of its putative messenger arachidonic acid and the non-physiological gap junction uncoupler alpha-glycyrrhetinic acid (AGA). None of these agents increased glucose uptake by C6 glioma cells, a cell line in which gap junction proteins are poorly expressed. In confluent astrocytes, the inhibition of gap junction permeability caused by AGA doubled the activity of the pentose phosphate shunt with minimal changes in the activity of the pyruvate dehydrogenase-catalyzed reaction and that of the tricarboxylic acid cycle. By contrast, these effects were not observed in dissociated astrocytes in which intercellular communication is lacking. The scraped loading dye transfer technique was modified to follow the passage of glucose and its metabolites through astrocyte gap junctions. The diffusion of glucose, the phosphorylated derivative glucose-6-phosphate, the phosphorylisable but not metabolisable derivative ortho-methyl-glucose, and the anaerobic glycolytic product L-lactate was much higher in astrocytes than in C6 glioma cells and was inhibited by the inhibition of gap junction permeability caused by endothelin-1, arachidonic acid, octanol, or AGA. It is concluded that gap junction permeability may regulate brain metabolism by controlling the uptake, utilization, and intercellular distribution of glucose and its metabolites in astrocytes.
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PMID:Endothelin-1 regulates glucose utilization in cultured astrocytes by controlling intercellular communication through gap junctions. 883 89

Translocation of [3H]dopamine and binding of [3H]WIN 35,428 were measured in intact C6 glioma cells expressing the cloned human dopamine transporter (hDAT) under identical conditions of assay buffer (phosphate-Krebs) and temperature (25 degrees C) with uptake at initial velocity and binding at equilibrium. In the intact cells, [3H]dopamine uptake was a one-component process; in contrast, [3H]WIN 35,428 binding included both a high-affinity component, inhibitable by micromolar concentrations of dopamine, and a low-affinity component only partially inhibited by millimolar concentrations of dopamine. Binding (high-affinity) over uptake Ki ratios were on the average 2.3 for the inhibitors WIN 35,428, cocaine, GBR 12909, and BTCP. The potency of dopamine in inhibiting its own translocation was close to that in inhibiting [3H]WIN 35,428 binding consonant with a more rapid reorientation step of the DAT in the C6-hDAT system than in rat striatal synaptosomes. The similarity in turnover values of the DAT estimated in the current experiments with the C6-hDAT system and in our previous study on rat striatal synaptosomes, performed under comparable conditions, suggest that all DAT's inserted into the C6 cell membrane are functionally active.
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PMID:Translocation of dopamine and binding of WIN 35,428 measured under identical conditions in cells expressing the cloned human dopamine transporter. 887 59

Interleukin-1 (IL-1), an inflammatory cytokine overexpressed in the neuritic plaques of Alzheimer's disease, activates astrocytes and enhances production and processing of beta-amyloid precursor protein (beta-APP). Activated astrocytes, overexpressing S100 beta, are a prominent feature of these neuritic plaques, and the neurite growth-promoting properties of S100 beta have been implicated in the formation of dystrophic neurites overexpressing beta-APP in neuritic plaques. These facts collectively suggest that elevated levels of the inflammatory cytokine IL-1 drive S100 beta and beta-APP overexpression and dystrophic neurite formation in Alzheimer's disease. To more directly assess this driver potential for IL-1, we analyzed IL-1 induction of S100 beta expression in vivo and in vitro, and of beta-APP expression in vivo. Synthetic IL-1 beta was injected into the right cerebral hemispheres of 13 rats. Nine additional rats were injected with phosphate-buffered saline, and seven rats served as uninjected controls. The number of astrocytes expressing detectable levels of S100 beta in tissue sections from IL-1-injected brains was 1.5 fold that of either control group (p < 0.01), while tissue S100 beta levels were approximately threefold that of controls (p < 0.05). The tissue levels of two beta-APP isoforms (approximately 130 and 135 kDa) were also significantly elevated in IL-1-injected brains (p < 0.05). C6 glioma cells, treated in vitro for 24 h with either IL-1 beta or IL-1 alpha, showed significant increases in both S100 beta and S100 beta mRNA levels. These results provide evidence that IL-1 upregulates both S100 beta and beta-APP expression, in vivo and vitro, and support the idea that overexpression of IL-1 in Alzheimer's disease drives astrocytic overexpression of S100 beta, favoring the growth of dystrophic neurites necessary for evolution of diffuse amyloid deposits into neuritic beta-amyloid plaques.
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PMID:In vivo and in vitro evidence supporting a role for the inflammatory cytokine interleukin-1 as a driving force in Alzheimer pathogenesis. 889 49

Although P2 receptors mediate a myriad of physiological effects of extracellular adenine nucleotides, study of this broad class of receptors has been compromised by a lack of P2 receptor-selective antagonist molecules. The adenine nucleotide-promoted inositol lipid hydrolysis response of turkey erythrocyte membranes, which has been used extensively as a model for P2Y receptors, has been applied to identify molecules that competitively block these receptors. Adenosine-3'-phosphate-5' -phosphosulfate (A3P5PS) promoted activation of phospholipase C that was only 10-25% of that observed with the full P2Y receptor agonists ATP, ADP, and 2-methylthio-ATP (2MeSATP). The small stimulatory effects of A3P5PS were saturable. Moreover, these effects were entirely the result of interaction with the P2Y receptor, because A3P5PS had no effect on activation of phospholipase C through the beta-adrenergic receptor and produced a concentration-dependent inhibition of 2MeSATP-promoted activity over the same range of A3P5PS concentrations that alone caused a small activation of phospholipase C. Increasing concentrations of A3P5PS produced a rightward shift of the concentration-effect curve for 2MeSATP, and Schild transformation of these data revealed that A3P5PS is a competitive P2Y receptor antagonist with a pKB of 6.46 +/- 0.17. The presence of a phosphate in the 2'- or 3'-position appears to be crucial for antagonist activity, because adenosine-3' -phosphate-5'- phosphate (A3P5P) and adenosine-2'- phosphate-5'-phosphate also exhibited competitive antagonist/partial agonist activities. Other 3'-substituted analogues, such as 3'-amino-ATP and 3'-benzoylbenzoyl-ATP, were full agonists with no antagonist activity. A3P5PS, A3P5P, and adenosine-2',5'-diphosphate also were competitive antagonists in studies with the cloned human P2Y1 receptor stably expressed in 1321N1 human astrocytoma cells. Moreover, both A3P5PS and A3P5P were devoid of agonist activity at the human P2Y1 receptor. The effects of these 2'- and 3'-phosphate analogues were specific for the phospholipase C-coupled P2Y1 receptor, because no agonistic or antagonistic effects on the adenylyl cyclase-coupled P2Y receptor of C6 glioma cells or on P2Y2, P2Y4, or P2Y6 receptors stably expressed in 1321N1 human astrocytoma cells were observed. These results describe specific competitive antagonism of the P2Y1 receptor by an adenine nucleotide derivative and provide a potential new avenue for P2 receptor drug development.
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PMID:Identification of competitive antagonists of the P2Y1 receptor. 891 64

1. B10 cells, a clonal line of rat brain capillary endothelial cells, exhibit a single P2 purinoceptor, activation of which leads to increases in free intracellular calcium. In the current study the identity of this P2Y receptor was determined by its binding parameters for a range of purinoceptor ligands and by its complementary DNA (cDNA) sequence. The signal transduction mechanism activated by this receptor was also investigated. 2. The radioligand [35S]-dATP alpha S bound with high affinity (Kd = 9.8 nM) to the P2Y purinoceptor expressed on B10 cells, which was found to be extremely abundant (Bmax = 22.5 pmol mg-1 protein). The calculated Ki values of a range of P2 purinoceptor agonists which competitively displaced binding of [35S]-dATP alpha S led to the rank order of affinity: dATP alpha S (Ki 3.4 nM) > 2-chloroATP (2-ClATP) (13 nM), ATP (22 nM) > ATP gamma S (43 nM) > 2-methylthioATP (2-MeSATP) (88 nM) > ADP (368 nM) > > UTP, L-beta,gamma-methyleneATP (both > 10,000 nM). The P2 purinoceptor antagonists, Reactive blue 2 and suramin, were also able to displace binding, with Ki values of 833 and 1358 nM respectively. In contrast pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid 4-sodium (PPADS) was able to displace only 20% of [35S]-dATP alpha S binding at a concentration of 100 microM. 3. 2-ClATP (EC50 = 0.22 microM), 2-MeSATP (0.54 microM), ADP (7.9 microM) and ATP (a partial agonist), but not UTP, inhibited the cyclic AMP formation stimulated by cholera toxin, in a manner that was prevented by pertussis toxin. The purinoceptor antagonist, PPADS, was found to be inactive at a concentration of 100 microM. 4. A P2Y receptor cDNA was derived from mRNA from B10 cells and from C6-2B, a rat glioma cell line known to possess a P2Y receptor that is coupled to the inhibition of adenylate cyclase. Sequence analysis of the entire coding region revealed that both were 100% identical to the rat P2Y1 purinoceptor cDNA. No other P2Y-type receptor mRNA could be detected in B10 cells. Exactly the same sequence was isolated from rat brain cortical astrocytes, where 2-MeSATP has been shown to increase phospholipase C activity. 5. Since the receptor responsible for the transduction shares with the aforementioned binding site significant pharmacological features, including a strong activity of 2-MeSATP (characteristic of P2Y1 receptors alone among all known P2Y purinoceptors) and an unusual insensitivity to PPADS, and since abundant mRNA is present of the P2Y1 receptor but not of any other type resembling the known P2Y receptors, it is concluded that a P2Y1 receptor on rat brain microvascular endothelial cells can account for all of the observations. This single P2Y1 receptor, therefore, appears to couple in different native cell types to either adenylate cyclase inhibition or to phospholipase C activation.
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PMID:The P2Y purinoceptor in rat brain microvascular endothelial cells couple to inhibition of adenylate cyclase. 896 47


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