Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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 present article investigates chronic opioid regulation of the stimulatory adenylate cyclase-coupled prostaglandin E1 (PGE1) receptor system in neuroblastoma x glioma (NG108-15) hybrid cells. Persistent activation of delta-opioid receptors by morphine (10 mumol/L; 3 days) substantially down-regulates the number of PGE1 binding sites by approximately 30%, without affecting their affinity. Radioligand binding studies performed in the presence of GTP gamma S (100 mumol/L) further revealed that the remaining PGE1 binding sites are still capable of interacting functionally with their associated stimulatory G proteins, Gs. On the postreceptor level, neither changes in the abundance nor in the intrinsic activity of the alpha subunit of Gs (Gs alpha) were found during the state of opioid dependence, as has been verified by western blot and S49 cyc- reconstitution experiments, respectively. Evaluation of the functional interaction between PGE1 receptors and Gs by means of receptor-stimulated, cholera toxin-catalyzed ADP-ribosylation of Gs alpha revealed a significant increase in the ability of PGE1 receptors to activate Gs alpha (3.3-fold increase in EC50; p < 0.05) in cells chronically exposed to morphine. This effect was completely blocked by coincubation of the cells together with the opiate antagonist naloxone (100 mumol/L; 3 days), whereas precipitation of morphine withdrawal by naloxone (100 mumol/L) had no further effect on sensitization in PGE1 receptor/Gs coupling. These findings provide evidence that the stimulatory adenylate cyclase-coupled PGE1 receptor system represents a potential target of chronic delta-opioid receptor activation in NG108-15 hybrid cells. They further suggest that sensitization in stimulatory signal transduction plays a critical role in the generation of opioid dependence.
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PMID:Chronic activation of inhibitory delta-opioid receptors cross-regulates the stimulatory adenylate cyclase-coupled prostaglandin E1 receptor system in neuroblastoma x glioma (NG108-15) hybrid cells. 776 24

This study describes the depression of calcium currents caused by activation of human D3 dopamine receptors which have been stably expressed in the neuroblastoma x glioma NG108-15 cell line. Transfected cells, which had been differentiated with prostaglandin E1 and isobutylmethylxanthine, exclusively expressed D3 receptor mRNA, which was demonstrated by reverse transcription polymerase chain reaction techniques. Transfected cells had high affinity binding sites for iodosulpiride, with a Kd of 0.8 nM and receptor density of 240 fmol mg-1 protein. Calcium currents were recorded using nystatin-perforated patch clamp techniques. In contrast to untransfected cells that had been differentiated, high-threshold calcium currents in differentiated hD3-NG108-15 cells were depressed by application of dopamine and quinpirole. These responses were abolished by the dopamine receptor antagonist S-(-)-sulpiride (1 microM), demonstrating that they were caused by the activation of the transfected dopamine receptors. Coupling of human D3 receptors to calcium currents was sensitive to the action of pertussis toxin, suggesting the involvement of G-proteins of the Gi and/or G(o) subtype. These results demonstrate that human D3 receptors represent a functional class of dopamine receptor.
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PMID:Functional expression of human D3 dopamine receptors in differentiated neuroblastoma x glioma NG108-15 cells. 791 12

Long-term treatment with ethanol increases delta-opioid receptor (DOR) expression in the NG108-15 neuroblastoma x glioma hybrid cell line. To determine the underlying mechanism, we studied the effects of ethanol on [3H]diprenorphine binding to intact cells and DOR gene expression in four related clonal neural cell lines. Incubation with 200 mM ethanol for 48 hr increased [3H]diprenorphine binding by 1.4- (N18TG2), 1.8- (NG108-15), 1.9- (N4TG1), and 3.0-fold (N1E-115). Treatment with 25, 50, or 100 mM ethanol for 1 week caused a dose-dependent increase in receptor expression. Receptor up-regulation was associated with an increase in the potency of etorphine for inhibiting prostaglandin E1-stimulated cAMP accumulation. Constitutive DOR expression differed more than 3-fold among the different cell lines and correlated positively with basal cAMP levels. Long-term ethanol treatment increased basal cAMP levels in three of the four cell lines, but did not induce cellular differentiation. Northern blot analysis demonstrated an identical pattern of multiple transcripts in the four cell lines. Ethanol increased the abundance of DOR mRNA by approximately 3-fold in N18TG2 cells and by approximately 5-fold in the remaining cell lines. These findings indicate that clinically relevant concentrations of ethanol regulate DOR expression by increasing the abundance of DOR mRNA. The disparity between the increase in gene expression and ligand binding suggests that ethanol may also modify mRNA translation or receptor processing.
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PMID:Ethanol increases delta-opioid receptor gene expression in neuronal cell lines. 826 48

To understand the details of regulation of guanine-nucleotide-binding-protein-linked transmembrane cellular-signalling cascades, it is important to know the absolute levels of each polypeptide component and the stoichiometry of their interactions. Amounts of the IP prostanoid receptor, the stimulatory G protein of the adenylyl cyclase cascade (Gs alpha) and the functional complex of Gs alpha with adenylyl cyclase, which acts as the cyclic AMP generator, were measured in membranes of neuroblastoma x glioma hybrid, NG108-15, cells. As measured by the specific binding of [3H]prostaglandin E1, the IP prostanoid receptor was present in some 100,000 copies/cell. Gs alpha assessed by quantitative immunoblotting with recombinantly expressed protein, was present in considerably higher levels (1,250,000 copies/cell). However, the maximal formation of a complex of Gs alpha and adenylyl cyclase represented only some 17,500 copies/cell. The previously established 8:1 stoichiometry of concurrent downregulation of Gs alpha and the IP prostanoid receptor in these cells [Adie, E. J., Mullaney, I., McKenzie, F. R. & Milligan, G. (1992) Biochem. J. 285, 529-536] indicates that full-agonist occupation of the receptor should be able to activate some 65% of the expressed Gs. Despite the potential 70-fold excess of Gs alpha over the Gs alpha/adenylyl cyclase complex, IP prostanoid-receptor-agonist-mediated reduction of Gs alpha levels by some 35% resulted in a 25% reduction in the maximal formation of the Gs alpha/adenylyl cyclase complex. Such results demonstrate that adenylyl cyclase is quantitatively the least highly expressed component of this signalling cascade and suggests that much of the cellular Gs alpha may not have access to adenylyl cyclase.
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PMID:Quantitative stoichiometry of the proteins of the stimulatory arm of the adenylyl cyclase cascade in neuroblastoma x glioma hybrid, NG108-15 cells. 830 80

Differentiated neuroblastoma cells exhibit both the delayed rectifier potassium current (IK) and the M-current (IM). The present study was designed to determine the roles of protein kinase C (PKC) and of the calmodulin-binding protein 80K/MARCKS, a prominent substrate for PKC and possible regulator of these currents. Neuroblastoma x glioma (NG108-15) hybrid cells transfected with m1 muscarinic receptors were grown with 1% fetal bovine serum (FBS) without the prostaglandin E1 (PGE1) and isobutylmethylxanthine (IBMX) usually added in preparation for electrophysiological studies. Under these conditions, the usual pleomorphism was largely abolished, leaving two populations of small cells with stellate and spherically symmetrical geometries. Whole-cell patch clamping indicated that the two cell types had identical electrophysiological properties, displaying: IK, a small current through a "T-like" Ca2+ channel, and no M-current. Stimulation with carbachol shifted the distribution of cells to a more stellate morphology within 24 hr and later (after 48 hr) reduced the PKC substrate 80K/MARCKS by 22 +/- 7%. In contrast to the stimulation of IK observed with cardiac cells, PKC activation produced only a small inhibition of IK, which was independent of carbachol pretreatment. Thus, PKC and 80K/MARCKS can be dissociated from the regulation of IK in neuroblastoma cells.
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PMID:Whole-cell recording of neuroblastoma x glioma cells during downregulation of a major substrate, 80K/MARCKS, of protein kinase C. 832 Jul 19

This study investigates the functional state of the stimulatory GTP-binding protein GS in neuroblastoma x glioma NG108-15 hybrid cells chronically exposed to an opioid. For this purpose, a novel in situ reconstitution protocol was established using membranes selectively depleted of GS function by transient exposure to low pH and then reconstituted with purified exogenous stimulatory GTP-binding proteins. With prostaglandin E1 (PGE1) receptor-stimulated adenylate cyclase activity as an indicator, reconstituted membranes of cells previously rendered tolerant to the delta-opioid [D-Ala2,D-Leu5]enkephalin (DADLE) exhibited approximately 3-fold elevated cAMP generation upon stimulation with PGE1, compared with nontolerant reconstituted cell membranes. This effect developed dose-dependently with respect to the opioid concentration used for pretreatment of the cells and was blocked by concomitant exposure to naloxone. In contrast, receptor-independent activation of GS by the stable GTP analogue guanosine-5'-O-(3-thio)triphosphate did not reveal any difference in adenylate cyclase activity between reconstituted membranes of control and chronically DADLE-pretreated cells. Furthermore, the functional activity of endogenous GS displayed no difference between control and DADLE-tolerant cells, as assessed in S49 cyc- reconstitution assays using sodium cholate extracts derived from NG108-15 membranes. The data presented suggest that the increase in PGE1 receptor-mediated adenylate cyclase activity in opioid-tolerant/dependent NG108-15 hybrid cells most likely relates to enhanced coupling efficiency between the PGE1 binding site (receptor) and GS. Moreover, our results support the concept that supersensitivity to excitatory drugs reflects an adaptive mechanism of cells chronically exposed to an opioid.
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PMID:Coupling of prostaglandin E1 receptors to the stimulatory GTP-binding protein Gs is enhanced in neuroblastoma x glioma (NG108-15) hybrid cells chronically exposed to an opioid. 838 8

In neuroblastoma x glioma NG108-15 hybrid cells, opioid agonists inhibited both basal and prostaglandin E1-stimulated adenylate cyclase activities assayed in the presence of the phosphodiesterase (PDE) inhibitors isobutylmethylxanthine and ZK62711 (rolipram). However, when intracellular [3H]cAMP was measured in the absence of the PDE inhibitors the maximal inhibitory level was increased, using the opioid agonist D-Ala2,D-Leu5-enkephalin. This increase in opioid activity was due to agonist stimulation of cAMP degradation, because when the degradation rate of [3H] cAMP was measured in intact hybrid cells it was observed to increase from the control value of 0.495 +/- 0.003 min-1 to 0.760 +/- 0.003 min-1 in the presence of 1 microM D-Ala2,D-Leu5-enkephalin; this was reversed by naloxone. Dose-dependent studies with various opioid agonists, partial agonists, and antagonists revealed that there was a direct correlation between the abilities of these opioid ligands to inhibit adenylate cyclase activity and to stimulate PDE activity, with enkephalin and its analogs being the most potent agonists. Chronic agonist treatment also resulted in a reduction of the opioid agonist stimulation of cAMP degradation, with an apparent decrease in the PDE activity upon addition of naloxone after chronic treatment. However, treatment of the hybrid cells with pertussis toxin, which attenuated the agonist inhibition of adenylate cyclase activity, did not abolish this opioid response. When selective inhibitors for various types of PDE were used, the type I PDE inhibitor W-7 attenuated the opioid effect, whereas the type II PDE inhibitor trequinsin (HL725), the type III PDE inhibitor indolidan, and the type IV PDE inhibitor rolipram had no effect on opioid-stimulated cAMP degradation. The stimulation of type I PDE activity by delta-opioid receptors was independent of extracellular Ca2+ and was not observed with membrane preparations. Therefore, in NG108-15 cells delta-opioid receptors regulate intracellular cAMP levels by coupling to a pertussis toxin-insensitive guanine nucleotide-binding protein, resulting in an increase in intracellular Ca2+ and in Ca2+/calmodulin-dependent PDE activity.
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PMID:delta-Opioid receptor activates cAMP phosphodiesterase activities in neuroblastoma x glioma NG108-15 hybrid cells. 838 86

Stable expression of neuronal receptors in cell lines of neural origin is important for studies of neurotransmitter mediated signal transduction. We have achieved this for the first time in three cell lines which are derived from various tissues of neural origin (hippocampus, HN2; chinese hamster brain explant, NCB-20; rat dorsal root ganglion, F-11). Following electroporation assisted transfer of a construct containing the hippocampal serotonin 5-HT1A receptor (5-HT1AR) DNA, one neural cell line, NG-108-15 (murine neuroblastoma x C6 glioma), failed to express the transfected activity, while three others as well as the non-neural CHO (chinese hamster ovary) cells expressed high levels of the receptor. Upon normalization to coexpressed human beta-hexosaminidase B activity, it was found that the human 5-HT1AR, which is normally concentrated in the hippocampus and at a lesser density in the brain, was expressed at the highest level (15.7 x 10(4) receptors/cell) in the HN2 followed by the NCB-20 (8.3 x 10(4) receptors/cell), F-11 (4.4 x 10(4) receptors/cell) and lastly the non-neuronal CHO (4.2 x 10(4) receptors/cell) cells. Ten-twelve days after passage, a striking increase in expression of the receptor was observed only in the cell lines of neural origin. By contrast, there was no appreciable increase in expression of the transfected 5-HT1AR in the non-neural CHO cells over time. This late increase in expression was eliminated in cells which had been maintained in low glucose (1 g/L) for the first two days after passage, thus establishing a vital role of glucose in expression of the transfected 5-HT1AR in cell lines of neural origin. In all cases the 5-HT1AR was negatively coupled to adenylate cyclase, as evidenced by an agonist mediated decrease in prostaglandin E1 stimulated cyclic AMP levels.
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PMID:Heterologous expression of the serotonin 5-HT1A receptor in neural and non-neural cell lines. 847 11

Prolonged exposure of neuroblastoma x glioma (NG 108-15) hybrid cells to inhibitory acting drugs results in sensitization of adenylate cyclase. We now report that chronic activation (3 days) of either inhibitory delta-opioid receptors, alpha 2B-adrenoceptors, or muscarinic M4 receptors significantly decreases the number of stimulatory, adenylate cyclase-coupled prostaglandin E1 receptors. Pharmacological characterization further revealed that the loss of [3H]prostaglandin E1-binding sites most likely corresponds to a reduction of the number of high-affinity, G protein-coupled prostaglandin E1 receptors. The decline in functionally active prostaglandin E1 receptors developed in a time- and dose-dependent manner and could be prevented by pretreatment of the cells with pertussis toxin. Heterologous prostaglandin E1 receptor regulation was blocked by concomitant exposure of the cells to antagonists for inhibitory receptors and was rapidly reversed (t 1/2 < 30 min) upon termination of chronic inhibitory drug treatment. The decrease in high-affinity prostaglandin E1 receptors developed regardless of whether full or partial agonists were used for pretreatment. In addition, the concentrations of inhibitory drugs required to maximally affect prostaglandin E1 receptor number closely resembled those mediating maximal adenylate cyclase inhibition. The data demonstrate that chronic inhibitory drug treatment of NG 108-15 hybrid cells reduces the number of functionally active, excitatory prostaglandin E1 receptors. Thus, it is proposed that adaptations at the level of stimulatory receptor systems contribute to the regulatory mechanisms associated with drug dependence.
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PMID:Chronic exposure of NG 108-15 cells to inhibitory acting drugs reduces stimulatory prostaglandin E1 receptor number. 879 Oct 8

Volume regulation of C6 glioma cells was studied with an automatic system for monitoring cell thickness, while increasing bath osmolality from 300 to 440 mosmol/kgH2O. At 37 degrees C, tissues incubated in solutions containing active substances (inositol, D-biotin, hydrocortisone, prostaglandin E1, insulin, transferrin, sodium selenite, and 3,5,3'-triiodothyronine) responded to hyperosmotic challenge with a typical regulatory volume increase (RVI). Lowering temperature or removing the active substances inhibited osmoregulation. Bumetanide, amiloride, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, or ouabain significantly reduced RVI. Ion substitutions of Na+, Cl-, NaCl, or HCO3- also importantly affected the process. Extracellular acidification rate (EAR) was studied by microphysiometry. Hyperosmotic shock induced an increase in EAR with a time course that matched volume recovery. This increase in EAR was prevented by amiloride. The data show that under hyperosmotic conditions C6 cells are able to regulate their volume. Ion substitutions and application of blockers demonstrate that Na+/H+ and Cl-/HCO3- exchangers and Na(+)-K(-)-2Cl- cotransporter are involved in RVI. The rise in EAR is due to the enhanced activity of Na+/H+ antiporter, which seems to be volume dependent but not osmotic dependent.
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PMID:Electrolyte transport mechanisms involved in regulatory volume increase in C6 glioma cells. 889 8


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