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)

Metabolic rates and intercellular transfer of metabolites were studied in human glia and glioma culture cells via topographic scan of NAD(P)H fluorescence by multichannel microfluorometry in conjunction with microinjection of glucose-6-P + allosteric activators. Metabolic rates evaluated from NAD(P) in equilibrium NAD(P)H transients and the required substrate levels were 3--4 times lower in glioma cells as compared to glia cells. Both glia and glioma cells showed variability in the occurrence of intercellular metabolite transfer, detectable via observation of a transient in a neighbour of the cell injected with substrate. On this basis "multicellular integrated states" can be defined in clusters of glioma and glia cells interconnected by cell-to-cell contact and a mesh-like network of intercellular processes. Such multicellular steady states and the associated metabolic rates or their impairment can be used in turn to classify different culture lines in reference to cell physiology and pathology.
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PMID:Metabolic rates and intercellular transfer of molecules in cultures of human glia and glioma cells. 3 40

1. When C6 glioma cells were incubated with mycophenolic acid, a potent and specific inhibitor of IMP:NAD oxidoreductase (EC 1.2.1.14) there was a marked depletion of the cellular content of GTP. The viability of the cells was unaffected. 2. The adenosine 3':5'-monophosphate (cyclic AMP) response of C6 glioma cells to the beta-adrenergic stimulant, (+/-)isoprenaline, was considerably reduced after treatment with mycophenolic acid. The diminished response to (+/-)isoprenaline was prevented by the inclusion of guanine in the culture medium along with mycophenolic acid. 3. The adenylate cyclase response to (+/-)isoprenaline of whole homogenates from C6 cells treated with mycophenolic acid was also depressed; the response was restored to normal by the addition of GTP. 4. The adenylate cyclase response to (+/-)isoprenaline of a membrane fraction prepared from homogenates of C6 cells was almost totally dependent on the presence of added GTP. Membrane fractions from control and mycophenolic-acid-treated C6 cells gave similar adenylate cyclase responses to (+/-)isoprenaline in the presence of GTP. 5. It is concluded that mycophenolic acid may depress the beta-adrenergic sensitivity of C6 cells by depleting the cellular content of GTP.
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PMID:Reduction in beta-adrenergic response of cultured glioma cells following depletion of intracellular GTP. 19 9

NG108-15 neuroblastoma x glioma somatic hybrid cells were permeabilized in the presence of [32P]NAD+ and then cultured for 18 h. Resolution of the cell proteins on polyacrylamide gels revealed [32P]ADP-ribosylation of five major protein species with molecular mass values of 52 kDa, 44 kDa, 35 kDa, 30 kDa and 25 kDa. A similar pattern of labelling was also seen when NG108-15 cell membranes were incubated with [32P]NAD+ and hydrolysis of the product revealed mono(ADP-ribosyl)ation. Immunoprecipitation of these products with anti-Gs alpha antiserum revealed a single band identical to cholera toxin substrate. Culture of [32P]NAD(+)-loaded cells for 18 h in the presence of 50 mM-nicotinamide inhibited the eukaryotic mono(ADP-ribosyl)transferase activity. Inhibition of the eukaryotic enzyme was also accompanied by an increase in the abundance of Gs alpha, whether measured by Western blotting with anti-Gs alpha antibody (two separate antisera) or by cholera toxin-dependent [32P]ADP-ribosylation. There was no accompanying change in the abundance of G beta. The increase in Gs alpha abundance in nicotinamide-treated NG108-15 cells was accompanied by a 2-fold increase in basal adenylate cyclase activity (measured in the presence of GTP), and by a smaller but significant increase in iloprost-dependent activation of adenylate cyclase. Receptor number or affinity was not affected by nicotinamide, since this treatment did not alter the binding parameters of [3H]iloprost to NG108-15 cell membranes. Short-term exposure of cells to nicotinamide for 1 h revealed no significant difference in either basal or agonist-stimulated adenylate cyclase activity. These results reveal that mono(ADP-ribosyl)ation of Gs alpha by eukaryotic ADP-ribosyltransferase modifies the abundance and activity of Gs alpha in NG108-15 cells, and hence may play a role in the hormonal regulation of cell function.
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PMID:Gs alpha is a substrate for mono(ADP-ribosyl)transferase of NG108-15 cells. ADP-ribosylation regulates Gs alpha activity and abundance. 128 Jan 14

Effects of gamma-rays and glucose analogs, 2-deoxy-D-glucose (2-DG), 5-thio-D-glucose (5-TG) and 3-O-methyl glucose (3-O-MG) on cellular energy metabolism have been studied in a cell line, derived from a human cerebral glioma, by analysing intermediates of glycolysis and some important nucleotides (ATP, NAD etc.) using the technique of isotachophoresis. Gamma-irradiation induced a transient decrease in the nucleotide levels accompanied by an accumulation of sugar phosphates, the nucleotide levels recovering in a few hours post-irradiation. 2-DG inhibited glycolysis and reduced the nucleotide levels of irradiated as well as unirradiated cells in a concentration-dependent manner both in presence and absence of respiration, whereas 5-TG and 3-O-MG did not show significant effects in the presence of respiration. Reduced energy status observed with 2-DG under respiratory proficient conditions was completely reversed in 2 hr following its removal, whereas such a recovery was not observed in the absence of respiration. These results have important implications in the energy-linked modifications of tumour radiation response using glucose analogs.
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PMID:Effects of gamma-rays and glucose analogs on the energy metabolism of a cell line derived from human cerebral glioma. 178 71

Desensitization of the responsiveness to hormones or drugs is often mediated by down-regulation of receptors. The stimulatory coupling protein (Ns) of adenylate cyclase has been shown to be involved in the down-regulation of stimulatory beta-adrenergic receptors. Whether the inhibitory coupling protein (Ni) is involved in the down-regulation of receptors that inhibit adenylate cyclase is not known. We wished to determine whether down-regulation of inhibitory muscarinic cholinergic and alpha 2-adrenergic receptors occurs in neuroblastoma X glioma hybrid cells after the ability of Ni to inhibit adenylate cyclase is inactivated by pertussis toxin. After treatment of cells with pertussis toxin, the ability of carbachol or epinephrine to inhibit prostaglandin E1-stimulated cAMP accumulation in intact cells was either completely prevented or markedly attenuated, respectively, indicating functional inactivation of Ni. Furthermore, pertussis toxin treatment of membrane fragments from these cells did not result in labeling of the 41,000-dalton alpha-subunit of Ni with ADP ribose from [32P] NAD, indicating maximal ADP ribosylation of Ni by prior treatment of cells with pertussis toxin. Carbachol treatment of cells resulted in down-regulation of muscarinic cholinergic receptors to 45.7 +/- 12.5% and 52.5 +/- 13.5% of control values for toxin-untreated and toxin-treated cells, respectively. Epinephrine treatment of cells caused homologous desensitization of alpha 2-receptor-mediated inhibition of cAMP accumulation and down-regulation of alpha 2-adrenergic receptors to 42.9 +/- 11.4% and 53.2 +/- 5.3% of control values for toxin-untreated and toxin-treated cells, respectively. Down-regulation of muscarinic cholinergic receptors by carbachol and of alpha 2-adrenergic receptors by epinephrine was not due to the effect of retained agonist and was agonist specific, since it could be prevented by the antagonists atropine and yohimbine, respectively. We conclude that agonist-mediated down-regulation of both the muscarinic cholinergic receptor and the alpha 2-adrenergic receptor does not require functional inhibitory coupling.
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PMID:Agonist-induced down-regulation of muscarinic cholinergic and alpha 2-adrenergic receptors after inactivation of Ni by pertussis toxin. 242 98

Cultured rat glioma C6 cells exfoliate membrane vesicles which have been termed 'exosomes' into the culture medium. The exosomes contained both stimulatory and inhibitory GTP-binding components of adenylate cyclase (the stimulatory, Gs, and the inhibitory, Gi, regulatory components) and beta-adrenergic receptors but were devoid of adenylate cyclase activity. It was therefore apparent that the catalytic component of adenylate cyclase was either not exfoliated or was inactivated during the exfoliation process. The presence of Gs or Gi in the exosomes was detected by ADP ribosylation using [alpha-32P]NAD in the presence of cholera or pertussis toxins, respectively. The exosomal concentration of each of the two components was estimated to be about one fifth of that of the cell membrane when expressed on a per mg protein basis. Exosomal Gs was almost as active as the membrane-derived Gs in its ability to reconstitute NaF- and guanine nucleotide-stimulated adenylate cyclase activity in membranes of S49 cyc- cells, which lack a functional Gs. The ability of exosomal Gs to reconstitute isoproterenol-stimulated activity, however, was much lower than that of membrane Gs. The density of beta-adrenergic receptors in the exosomes was much less than that found in the membranes. Although the exosomal receptors bound the antagonist iodocyanopindolol with the same affinity as receptors from the cell membrane, the affinity for the agonist isoproterenol was 13- to 18-fold lower in the exosomes. In addition, this affinity was not modulated by GTP in the exosomes. Thus, exfoliated beta-adrenergic receptors seem to be impaired in their ability to couple to and activate Gs. This was directly tested by coupling the receptors to a foreign adenylate cyclase using membrane fusion. The fusates were then assayed for agonist-stimulated activity. While significant stimulation of the acceptor adenylate cyclase was obtained using C6 membrane receptors, the exosomal receptors were completely inactive. Thus during exfoliation, there appear to be changes in the components of the beta-adrenergic-sensitive adenylate cyclase that results in a nonfunctional system in the exosomes.
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PMID:Exfoliation of the beta-adrenergic receptor and the regulatory components of adenylate cyclase by cultured rat glioma C6 cells. 287 68

Activation of muscarinic cholinergic receptors of 1321N1 human astrocytoma cells attenuates cyclic AMP accumulation. This effect results from an activation of phosphodiesterase with no direct inhibition of adenylate cyclase activity. In spite of this lack of coupling of muscarinic receptors to adenylate cyclase, guanine nucleotides reduce the apparent binding affinity of the agonist carbachol in a washed membrane preparation of 1321N1 cells. The order of potency for this effect is guanosine 5'-O-(3-thiotriphosphate) greater than 5'-guanylyl-imidodiphosphate = GTP = GDP; ATP has no effect. The occurrence of a Mr = 41,000 protein labeled in the presence of [32P]NAD and pertussis toxin as well as the occurrence of guanine nucleotide-mediated inhibition of forskolin-stimulated adenylate cyclase activity indicate that the functional inhibitory guanine nucleotide regulatory component of adenylate cyclase (Ni) is present in 1321N1 cells. Pertussis toxin pretreatment of NG108-15 neuroblastoma X glioma cells, which express muscarinic receptors that link through Ni to inhibit adenylate cyclase, blocked the GTP-sensitive, high affinity binding of carbachol. In contrast, pretreatment of 1321N1 cells with a concentration of pertussis toxin that blocked [32P]ADP ribosylation of the Mr = 41,000 substrate and GTP-mediated inhibition of forskolin-stimulated adenylate cyclase activity had no effect on GTP-sensitive high affinity binding of carbachol. These results suggest that muscarinic cholinergic receptors of 1321N1 cells couple to a guanine nucleotide regulatory protein that is distinct from Ni.
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PMID:Guanine nucleotide-sensitive, high affinity binding of carbachol to muscarinic cholinergic receptors of 1321N1 astrocytoma cells is insensitive to pertussis toxin. 298

It has been proposed elsewhere [Meeker, R.B. & Harden, T. K. (1982) Mol. Pharmacol. 22, 310-319] that muscarinic cholinergic receptor-mediated attenuation of cAMP accumulation occurs through activation of phosphodiesterase in 1321N1 human astrocytoma cells. Pertussis toxin, which ADP-ribosylates the guanine nucleotide regulatory protein involved in receptor-mediated inhibition of adenylate cyclase (Ni), has been utilized to further differentiate between the mechanism of cholinergic regulation of cAMP metabolism in 1321N1 cells and the mechanism involving inhibition of adenylate cyclase in other tissues. Muscarinic receptor-mediated regulation of cAMP accumulation in NG108-15 neuroblastoma-glioma cells occurs through inhibition of adenylate cyclase. Pretreatment of these cells with pertussis toxin completely blocked the capacity of carbachol to attenuate cAMP accumulation. In contrast, concentrations of pertussis toxin two to three orders of magnitude higher than those effective in NG108-15 cells had no effect on muscarinic receptor-mediated attentuation of cAMP accumulation in 1321N1 cells. In addition, no effect of pertussis toxin was observed either on the control rate or the carbachol-stimulated rate of cAMP degradation measured directly in intact 1321N1 cells. A 41,000 Mr protein previously proposed to be the alpha subunit of Ni was labeled during incubation of a plasma membrane fraction from 1321N1 cells with [32P]NAD and pertussis toxin. Pertussis toxin is apparently active in 1321N1 cells, since this protein substrate was not labeled in plasma membrane preparations from cells previously incubated with toxin. Functional activity of Ni was demonstrated by the observation that guanosine 5'-[gamma-thio]triphosphate- and GTP-mediated inhibition of forskolin-stimulated adenylate cyclase activity occurred in cell-free preparations from 1321N1 cells. The inhibitory activity of these guanine nucleotides was lost in membrane preparations from pertussis toxin-treated cells. The data suggest that adenylate cyclase is not involved in cholinergic action in 1321N1 cells and, furthermore, Ni is not involved in muscarinic receptor-mediated activation of phosphodiesterase in these cells. Thus, pertussis toxin can be used to differentiate between two mechanisms of cholinergic regulation of cAMP metabolism.
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PMID:Pertussis toxin differentiates between two mechanisms of attenuation of cyclic AMP accumulation by muscarinic cholinergic receptors. 609 Nov 3

In neuroblastoma-glioma (NG108-15) hybrid cells, opiates inhibit adenylate cyclase and stimulate a low Km GTPase. It has been postulated that the stimulation of GTPase plays a role in opiate inhibition of adenylate cyclase (Koski, G., and Klee, W. A. (1981) Proc. Natl. Acad. Sci. U.S.A. 78, 4185-4189). Treatment of NG108-15 cells with pertussis toxin attenuates receptor-mediated inhibition of adenylate cyclase. The toxin acts by catalyzing the ADP-ribosylation of a 41,000-dalton substrate believed to be a part of the receptor-adenylate cyclase complex. We have found that toxin treatment of NG108-15 results in inhibition of the opiate-stimulated GTPase. The concentration of toxin required for inhibition of this GTPase was similar to that needed for both attenuation of opiate inhibition of adenylate cyclase and ADP ribosylation of the 41,000-dalton substrate. Inhibition of the opiate-induced GTPase by pertussis toxin in isolated membranes required NAD, consistent with the hypothesis that this effect of the toxin resulted from ADP ribosylation of a protein component of the system. Since the opiate-stimulated GTPase is believed to play a role in the receptor-mediated decrease in adenylate cyclase activity, inhibition of this GTPase may be an important part of the mechanism by which the toxin interferes with opiate action on adenylate cyclase.
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PMID:Pertussis toxin inhibits enkephalin stimulation of GTPase of NG108-15 cells. 613 91

Pertussis toxin (islet-activating protein) activates adenylate cyclase in susceptible cells by ADP-ribosylating an inhibitory component of the cyclase system. This toxin, assayed in a cell-free system in the presence of high concentrations of thiol, catalyzed the hydrolysis of NAD to ADP-ribose and nicotinamide. This NAD glycohydrolase activity co-chromatographed on Sephacryl G-200 in 6.5 M urea, pH 3.2, 0.1 M glycine with the ADP-ribosyltransferase activity of the toxin, as monitored by the transfer of [32P]ADP-ribose from [32P]NAD to a 41,000-Da protein in NG108-15 neuroblastoma X glioma hybrid cells. In the absence of thiol, the native holotoxin was enzymatically inactive. Following addition of 250 mM dithiothreitol to the assay, maximal enzymatic activity was evident after a delay of approximately 1 h; with 20 mM thiol, the delay was longer. The Km for NAD with the fully activated enzyme was 25 microM; the Km did not appear to vary with the extent of activation. Thiol was necessary in a cell-free system to demonstrate NAD glycohydrolase activity. When extensively washed membranes were used as a source of 41,000-Da substrate, thiol was necessary to observe ADP-ribosylation in some cases (human erythrocytes) and significantly stimulated activity in others (NG108-15 cells). In contrast to the bacterial toxins choleragen and Escherichia coli heat-labile enterotoxin that ADP-ribosylate stimulatory components of the cyclase system, pertussis toxin did not transfer ADP-ribose to low molecular weight guanidino compounds, such as arginine or agmatine.
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PMID:Activation by thiol of the latent NAD glycohydrolase and ADP-ribosyltransferase activities of Bordetella pertussis toxin (islet-activating protein). 631 27


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