UMLS:C0027819 - FACTA Search

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Query: UMLS:C0027819 (neuroblastoma)
27,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Neuroblastoma x glioma hybrid NG108-15 cells express a high-affinity IP prostanoid receptor. Saturation binding analysis of this receptor, using [3H]prostaglandin E1 ([3H]PGE1) as ligand, indicated that it was present at some 1.5 pmol/mg of membrane protein and displayed a dissociation constant for this ligand of 30-40 nM. Prolonged exposure of these cells either to PGE1 or to iloprost, which is a stable analogue of prostacyclin, caused a 40-70% decrease in levels of the receptor. The remaining receptors were capable of interacting with the stimulatory G-protein (Gs) of the adenylate cyclase cascade, as saturation analysis of the binding of [3H]PGE1 indicated that they had a similar affinity for the 3H-labelled ligand, and because the specific binding of [3H]PGE1 to these receptors was still sensitive to the presence of poorly hydrolysed analogues of GTP. We have recently demonstrated that prolonged exposure of NG108-15 ells to PGE1 causes a cyclic AMP-independent loss of Gs alpha-subunit (Gs alpha) from these cells [McKenzie & Milligan (1990) J. Biol. Chem. 265, 17084-17093]. Steady-state concentration of the larger 45 kDa form of Gs alpha (which is the predominant form expressed in these cells) was assessed to be 9.6 pmol/mg of membrane protein, and treatment with iloprost decreased levels of this polypeptide to some 3.0 pmol/mg of protein. Time courses of iloprost-mediated down-regulation of the IP prostanoid receptor, loss of Gs alpha protein as assessed by immunoblotting and loss of Gs alpha activity as assessed by the reconstitution of NaF stimulation of adenylate cyclase activity to membranes of S49 cyc- cells by sodium cholate extracts of NG108-15 cells were identical, suggesting that the loss of the IP prostanoid receptor and G-protein occurred in parallel. Each of these effects was half-maximal between 2 and 3 h of exposure to the agonist. Stoichiometry of loss of Gs alpha and IP prostanoid receptor was unchanged by the percentage receptor occupancy, and quantification indicated the loss of some 7-10 mol of Gs alpha/mol of receptor. This is the first report to demonstrate the temporal concurrence of loss of Gs alpha and of a receptor which interacts with this G-protein. Chronic activation of the IP prostanoid receptor on these cells results in the development of a heterologous form of desensitization to agents which function to activate adenylate cyclase [Kelly, Keen, Nobbs & MacDermot (1990) Br. J. Pharmacol. 99, 306-316]. Agonist regulation of Gs alpha levels in these cells may contribute to this process.
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PMID:Concurrent down-regulation of IP prostanoid receptors and the alpha-subunit of the stimulatory guanine-nucleotide-binding protein (Gs) during prolonged exposure of neuroblastoma x glioma cells to prostanoid agonists. Quantification and functional implications. 137 45

Parameters of ligand binding, stimulation of low-Km GTPase, and inhibition of adenylate cyclase were determined in intact human neuroblastoma SH-SY5Y cells and in their isolated membranes, both suspended in identical physiological buffer medium. In cells, the mu-selective opioid agonist [3H]Tyr-D-Ala-Gly(Me)Phe-Gly-ol ([3H]DAMGO) bound to two populations of sites with KD values of 3.9 and 160 nM, with less than 10% of the sites in the high-affinity state. Both sites were also detected at 4 degrees C and were displaced by various opioids, including quaternary naltrexone. The opioid antagonist [3H]naltrexone bound to a single population of sites, and in cells treated with pertussis toxin the biphasic displacement of [3H]naltrexone by DAMGO became monophasic with only low-affinity binding present. The toxin specifically reduced high-affinity agonist binding but had no effect on the binding of [3H]naltrexone. In isolated membranes, both agonist and antagonist bound to a single population of receptor sites with affinities similar to that of the high-affinity binding component in cells. Addition of GTP to membranes reduced the Bmax for [3H]DAMGO by 87% and induced a linear ligand binding component; a low-affinity binding site, however, could not be saturated. Compared with results obtained with membranes suspended in Tris buffer, agonist binding, including both receptor density and affinity, in the physiological medium was attenuated. The results suggest that high-affinity opioid agonist binding represents the ligand-receptor-guanine nucleotide binding protein (G protein) complex present in cells at low density due to modulation by endogenous GTP.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Opioid signal transduction in intact and fragmented SH-SY5Y neural cells. 156 Feb 22

Quinacrine altered the equilibrium binding of the muscarinic antagonist quinuclidinyl benzilate (QNB) to the muscarinic receptor in membranes from N18TG2 neuroblastoma cells. At 1 microM quinacrine, the apparent Kd for [3H]QNB binding was shifted from 48 to 210 pM without a decrease in the maximum binding. The competition binding profile of quinacrine indicates that it displaced [3H]QNB binding with an IC50 of 460 nM in a manner consistent with competitive inhibition. Quinacrine blocked the muscarinic inhibition of cyclic AMP accumulation by carbachol in cultured N18TG2 neuroblastoma cells without affecting arachidonic acid release or Gi coupling to the adenylate cyclase. The disruption of muscarinic receptor function by quinacrine may provide an explanation for its blockade of the muscarinic response in cells.
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PMID:Muscarinic receptor binding is inhibited by quinacrine. 165 14

The mechanisms of muscarinic receptor-linked increase in cAMP accumulation in SH-SY5Y human neuroblastoma cells has been investigated. The dose-response relations of carbachol-induced cAMP synthesis and carbachol-induced rise in intracellular free Ca2+ were similar. The stimulated cAMP synthesis was inhibited by about 50% when cells were entrapped with the Ca2+ chelator BAPTA or in the presence of the protein kinase C (PKC) inhibitor staurosporine. Production of cAMP could be induced also by the Ca2+ ionophore, ionomycin and by TPA, an activator of PKC. When added together TPA and ionomycin had a synergistic effect. When cAMP synthesis was activated with cholera toxin, PGE1 or PGE1 + pertussis toxin carbachol stimulated cAMP production to the same extent as in control cells. Ca2+ and protein kinase C thus seem to be the mediators of muscarinic-receptor linked cAMP synthesis by a direct action on adenylate cyclase.
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PMID:Muscarinic receptor-linked elevation of cAMP in SH-SY5Y neuroblastoma cells is mediated by Ca2+ and protein kinase C. 165 8

Cholera toxin treatment (up to 1 microgram/ml, 16 h) of neuroblastoma x glioma hybrid NG108-15 cells produced a decrease of some 35% in both delta opioid receptor-mediated stimulation of high-affinity GTPase activity and inhibition of forskolin-amplified adenylate cyclase. Coincident with these decreases was a down-regulation of some 35% in the delta opioid receptor population. A similar pattern of a decrease in signalling capacity was noted for the alpha 2B-adrenergic receptor in these cells after cholera toxin treatment. Half-maximal effects of cholera toxin on all of the parameters assayed were noted at concentrations between 2 and 5 ng/ml. Neither levels of Gi2, as assessed by immunoblotting with specific antisera, nor the intrinsic activity of the alpha subunit of the guanine-nucleotide-binding protein which acts as the inhibitory G-protein of the adenylate cyclase in these cells, as assessed by guanosine 5'-[beta gamma-imido]triphosphate (Gpp[NH]p)-mediated inhibition of adenylate cyclase, was lowered by cholera toxin treatment. Furthermore, levels of another pertussis toxin-sensitive G-protein (Go) expressed by these cells was also not lowered by cholera toxin treatment. However, as previously noted in other cells [Milligan, Unson & Wakelam (1989) Biochem. J. 262, 643-649], marked down-regulation of the alpha subunit of the stimulatory G-protein (Gs) of the adenylate cyclase cascade was observed in response to cholera toxin treatment. Previous studies [Klee, Milligan, Simonds & Tocque (1985) Mol. Aspects Cell Regul. 4, 117-129] have shown that cholera toxin treatment can result in a decrease in the maximal effectiveness of agonists which function to inhibit adenylate cyclase. These data have been used as evidence to suggest a functional interaction between Gs and 'Gi'. The results provided herein demonstrate that such effects of the toxin can be explained adequately by a decrease in the number of receptors that function to produce inhibition of adenylate cyclase.
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PMID:Cholera toxin impairment of opioid-mediated inhibition of adenylate cyclase in neuroblastoma x glioma hybrid cells is due to a toxin-induced decrease in opioid receptor levels. 167 34

The predominant consequences of mu-opioid-receptor activation are depression of both neuronal activity and transmitter release. Mu-Opioid agonists have previously been observed to increase a potassium conductance and to inhibit adenylate cyclase. We now report that activation of mu-opioid receptors directly decreases the N-type calcium-channel current in a differentiated, human neuroblastoma cell line (SH-SY5Y). The coupling between the mu-opioid receptor and the calcium channel involves a pertussis toxin-sensitive G protein and is independent of changes in adenylate cyclase activity. The inhibition of the calcium-channel current is voltage dependent because it is largely overcome by strong membrane depolarization. It is not associated with changes in the kinetics of current inactivation. Therefore, the mu-receptor belongs to the superfamily of G-protein-coupled, inhibitory neurotransmitter receptors which modulate the activity of calcium and potassium channels and adenylate cyclase.
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PMID:Mu-opioid-receptor-mediated inhibition of the N-type calcium-channel current. 167 47

D1 dopamine receptors on NS20Y neuroblastoma cells stimulate adenylate cyclase activity, whereas muscarinic receptors on the same cells negatively regulate adenylate cyclase. To determine the mechanisms which underlie these processes, cyclic AMP accumulation was measured in intact cells following either cholera or pertussis toxin treatment. Pretreatment with pertussis toxin (100 ng/ml), which ribosylated greater than 95% of inhibitory quinine nucleotide binding protein (Gi), caused the complete loss of muscarinic induced inhibition. Conversely, pertussis toxin did not affect the ability of dihydrexidine (1 microM, a full efficacy D1 agonist), PGE1 (100 nM), or forskolin (1 microM, a direct activator) to stimulate cAMP accumulation. Both the dihydrexidine-induced stimulation and the carbachol-induced inhibition of cyclic AMP accumulation were unaffected by either removal of extracellular calcium, or increased intracellular calcium caused by the addition of the calcium ionophore A23187. Cholera toxin dose- and time-dependently induced large accumulations of cAMP. At low cholera toxin concentrations, the effects of dihydrexidine (300 nM) were additive with those of cholera toxin. At cholera toxin concentrations greater than 100 ng/ml, dihydrexidine became ineffective in stimulating further cAMP synthesis. Conversely, forskolin (1 microM) still caused marked increases in cAMP accumulation after all cholera toxin treatments. Dihydrexidine-stimulated cAMP accumulation was additive with forskolin-stimulated cAMP accumulation at low forskolin concentrations (10 nM-3 microM), but synergistic at high concentrations (3-100 microM). Additionally, forskolin was much more potent after cholera toxin treatment, suggesting that an activated stimulatory guanine nucleotide binding protein (Gs) may be required for full activation of adenylate cyclase by forskolin in this cell type.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Guanine nucleotide binding proteins and the regulation of cyclic AMP synthesis in NS20Y neuroblastoma cells: role of D1 dopamine and muscarinic receptors. 168 5

The increase in hormone-stimulated cyclic AMP accumulation observed in a variety of intact cells after chronic pretreatment with drugs that inhibit adenylate cyclase activity has been attributed to an increase in adenylate cyclase activity following withdrawal of the inhibitory drug. In NG 108-15 mouse neuroblastoma X rat glioma hybrid cells (NG cells) chronically treated with the muscarinic cholinergic agonist carbachol, we have found a significant decrease in the apparent degradation rate constant for cyclic AMP, in addition to an increase in the prostaglandin E1 (PGE1)-stimulated cyclic AMP synthesis rate in intact cells. In carbachol-pretreated NG cells that were stimulated with a maximally effective dose of PGE1, and that accumulated steady-state cyclic AMP concentrations fourfold or more higher than in control cells, the apparent rate constant for degradation was about 53% lower than the value for control cells. In carbachol-pretreated cells stimulated with a submaximal dose of PGE1 to yield a steady-state cyclic AMP concentration comparable to control cells, the apparent rate constant was 31% lower than the value for control cells. In S49 mouse lymphoma cells (S49 cells) chronically treated with an analog of the inhibitory agonist somatostatin, the first-order rate constant for cyclic AMP degradation in intact cells following isoproterenol stimulation was 29% lower than the value for control cells. Despite these changes in the kinetics of cyclic AMP degradation in intact NG cells and S49 cells, there was either no change or a minimal change (less than 10%) in phosphodiesterase activities assayed in extracts of cells chronically exposed to inhibitory drugs.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Decreased cyclic AMP degradation in NG 108-15 neuroblastoma X glioma hybrid cells and S49 lymphoma cells chronically treated with drugs that inhibit adenylate cyclase. 168 17

1. Prostacyclin and adenosine A2 receptors activate adenylate cyclase in the neuroblastoma hybrid cell lines NG108-15 and NCB-20. Prolonged exposure of NG108-15 cells to iloprost (a stable analogue of prostacyclin) results in a subsequent reduction in the capacity for adenylate cyclase activation by iloprost, the adenosine analogue 5'-(N-ethyl)-carboxamidoadenosine (NECA) or NaF. In contrast prolonged exposure of NCB-20 cells to iloprost results only in the loss of iloprost responsiveness. 2. Iloprost pretreatment of NG108-15 cells also magnified the morphine-dependent inhibition of iloprost-stimulated adenylate cyclase activity from 36 to 48%. This change was not due to lower iloprost stimulation following desensitization, since the % inhibition of adenylate cyclase activity by morphine in control cells was constant irrespective of enzyme activity. 3. These heterologous effects observed in NG108-15 cells following iloprost pretreatment may involve changes in the GS alpha protein, since there was a reduction of about 30% in the cholera toxin-induced [32P]-ADP-ribosylation of a 45 kDa protein from cell membranes (corresponding to the extent of loss of NECA or NaF responsiveness). A similar reduction was not observed in NCB-20 cells. 4. These results indicate that iloprost pretreatment induces different forms of desensitization in NG108-15 and NCB-20 cell lines. The heterologous desensitization in the former may, like the human platelet, involve a functional loss of GS alpha from the cell membrane. Changes in the activity of GS alpha may also account for the heterologous effects on receptors that mediate inhibition of adenylate cyclase.
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PMID:Segregation of discrete GS alpha-mediated responses that accompany homologous or heterologous desensitization in two related somatic hybrids. 169 75

Dopamine or agonists with D1 receptor potency stimulated cyclic AMP (cAMP) accumulation in whole cell preparations of NS20Y neuroblastoma cells. The accumulation of cAMP after D1 stimulation was rapid and linear for 3 min. Both dopamine and the novel D1 receptor agonist dihydrexidine stimulated cAMP accumulation two- to three-fold over baseline. The pseudo-Km for dopamine was approximately 2 microM, whereas for dihydrexidine it was approximately 30 nM. The effects of both drugs were blocked by either the D1-selective antagonist SCH23390 (Ki, 0.3 nM) or the nonselective antagonist (+)-butaclamol (Ki, 5 nM). Both (-)-butaclamol and the D2-selective antagonist (-)-sulpiride were ineffective (Ki greater than 3 microM). Forskolin (10 microM), prostaglandin E1 (1 microM), and adenosine (10 microM) also stimulated cAMP accumulation, but none were antagonized by SCH23390 (1 microM). Finally, muscarinic receptor stimulation (100 microM carbachol) inhibited both D1- and forskolin-stimulated increases in cAMP accumulation by 80%. The present results indicate that NS20Y neuroblastoma cells have D1 receptors that are coupled to adenylate cyclase, and that these receptors have a pharmacological profile similar to that of the D1 receptor(s) found in rat striatum.
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PMID:D1 dopamine receptors of NS20Y neuroblastoma cells are functionally similar to rat striatal D1 receptors. 171 49

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