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: EC:4.6.1.1 (adenylate cyclase)
19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Neuroblastoma x glioma in NG108-15 cells possess opiate, alpha-adrenergic, and muscarinic acetylcholine receptors, which mediate an inhibition of adenylate cyclase. Growth of cells for 12--48 hours in the presence of a receptor--activator gradually results in a compensatory increase in adenylate cyclase activity. Withdrawal of the receptor ligand then results in relatively long-lived increases in adenylate cyclase activity and intracellular cAMP levels. Thus cells grown in the presence of morphine, norepinephrine, or acetylcholine seem to become dependent on the compound to maintain normal cAMP levels.
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PMID:Studies on synapse formation and opiate dependence. 21 60

Neuroblastoma cells were synchronized by a combined isoleucine plus glutamine starvation. Adenylate cyclase activity [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] was measured under basal conditions and in the presence of dopamine, adenosine and prostaglandin (PG) E1. A clear dissociation occurred between the respective evolution patterns of basal and agonist-stimulated adenylate cyclase activities. The magnitudes of the enzyme response to PGE1, adenosine, and dopamine also exhibited different evolution patterns during the cell cycle. Evolution of adenylate cyclase responsiveness to PGE1 during the cell cycle exhibited striking similarities with the intracellular 3':5'-cyclic AMP changes observed elsewhere. Use of theophylline and fluphenazine as specific inhibitors of adenosine and dopamine, respectively, made it possible to demonstrate that adenosine, dopamine, and PGE1 stimulated adenylate cyclase through independent receptor sites. Furthermore, whatever the stage of the cell cycle, responses to these three agonists were not additive, indicating that the receptors of adenosine, dopamine, and PGE1 control the same adenylate cyclase moieties. The data suggest that adenylate cyclase cell content and enzyme responsiveness to specific agonists can be independently controlled.
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PMID:Adenylate cyclase from synchronized neuroblastoma cells: responsiveness to prostaglandin E1, adenosine, and dopamine during the cell cycle. 26 97

Neuroblastoma adenylate cyclase is activated by 2-chloroadenosine, prostaglandin E1, and 5'-guanylylimidodiphosphate [GMP-P(NH)P]. However, the process of activation by the first two compounds is different from that induced by the third. Prostaglandin E1 and 2-chloroadenosine activation is rapid, producing elevated activities which are constant throughout a 20-min assay. In contrast, GMP-P(NH)P activation is slow and although the activity is elevated within 1 min, it continues to increase for up to 12 min before attaining a maximal constant value. Activation is more rapid when either prostaglandin E1 or 2-chloroadenosine is present with GMP-P(NH)P. Activation of the enzyme by GMP-P(NH)P appears to be retarded by endogenous nucleotides as suggested by the following observations: (a) if the enzyme is incubated at 30 degrees with 5 mM MgCl2 for 5 to 7 min, GMP-P(NH)P then produces maximal activation without a detect able lag; (b) if, during this incubation, nucleotides, a nucleotide regenerating system, or EDTA (instead of MgCl2) are present, subsequent GMP-P(NH)P activation is slow; and (c) in the assays which contain a nucleotide regenerating systm and MgATP as substrate, the Km for GMP-P(NH)P is 6 +/- 2 muM. However, in the assays using MgAMP-P(NH)P as substrate but no nucleotide regenerating system, the Km is 0.5 +/- 0.2 muM. GPD and GTP do not replace GMP-P(NH)P as an enzyme activator in any of our assays systems, and in fact, are potent inhibitors of GMP-P(NH)P enzyme activation. Prostaglandin E1 and 2-chloradensine do not alter significantly the Km for GMP-P(NH)P but do decrease the ensyme's sensitivity of GDP. Proposed is a hysteretic model of neuroblastoma adenylate cyclase, which shows the enzyme responding slowly to rapid changes in GMP-P(NH)P concentration due to the slow displacement of the tightly bound endogenous guanine nucleotides by GMP-P(NH)P. Additionally, prostaglandin E1 and 2-chloroadenosine increase the rate of GMP-P(NH)P activation by decreasing the enzyme's affinity for these endogenous guanine nucleotides.
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PMID:Neuroblastoma adenylate cyclase. Role of 2-chloroadenosine, prostaglandin E1, and guanine nucleotides in regulation of activity. 93 91

Neuroblastoma is the most common solid tumor of children less than 5 years of age; yet the biology of this tumor is poorly understood. Neuroblastoma tumors are derived from neural crest precursors; they synthesize both adrenergic and peptidergic neurotransmitters. This study determined VIP receptor expression in primary neuroblastoma tumors prior to chemotherapy. The VIP receptor was expressed in 12 of 15 neuroblastoma tumors as determined by direct binding studies (KD = 1.3-12.4 nM) and VIP-mediated stimulation of adenylate cyclase. The VIP stimulation index for adenylate cyclase in the primary tumor was inversely correlated with the VIP content of the tumor, suggesting that VIP regulates its own receptor expression. Similar observations were made in vitro by comparison of two human neuroblastoma cell lines, IMR32 and SKNSH. Both cell lines were demonstrated to express specific, high affinity VIP receptors (KD = 4 nM and 2.5 nM for IMR32 and SKNSH, respectively). IMR32 cells contained very low levels of VIP (0.6 pg VIP/10(6) cells). Exogenous VIP stimulated adenylate cyclase 22-fold over basal activity and VIP inhibited proliferation of IMR32 cells by 49% in 6-day cultures. On the other hand, SKNSH cells synthesized high levels of VIP (6.3 pg/10(6) cells), metabolized VIP rapidly and demonstrated a low level of VIP-mediated stimulation of adenylate cyclase; their proliferation rate was minimally inhibited by exogenous VIP. These observations help validate the hypothesis that VIP serves as an autocrine growth factor in neuroblastoma.
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PMID:Vasoactive intestinal peptide: autocrine growth factor in neuroblastoma. 131 95

Neuroblastoma x glioma NG 108-15 hybrid cells contain a homogeneous population of delta-opioid receptors. NG 108-15 membranes were labelled either with the opiate agonist, [3H]etorphine or the opiate antagonist [3H]diprenorphine under various conditions: absence or presence of Na+ and/or 5'-guanylylimidophosphate (GppNHp). Ultracentrifugation in linear sucrose gradients after digitonin solubilization of prelabeled receptor was performed. In the soluble extracts from NG 108-15 hybrid cell membranes, bound [3H]etorphine and bound [3H]diprenorphine sedimented in the same position, even in the presence of NaCl and/or GppNHp. These data were analyzed in terms of relative agonist potency of diprenorphine on this specific model, using equilibrium binding studies and inhibition of adenylate cyclase activity. Diprenorphine, at the concentrations used for sedimentation studies, behaving as an opiate antagonist, it is concluded that the delta-opioid receptor could be strongly precoupled to the G-protein in the NG 108-15 cell.
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PMID:The delta-opioid receptor in neuroblastoma x glioma NG 108-15 hybrid cells is strongly precoupled to a G-protein. 132 7

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

Neuroblastoma X glioma NG108-15 hybrid cells cultured in a chemically defined medium within 3 cell passages, exhibited viability, growth rate and morphology similar to those of cells grown in medium supplemented with 5% fetal calf serum. Hybrid cells cultured in the chemically defined medium within these periods of time also did not exhibit a difference in basal adenylate cyclase activity nor in the enzymatic activities stimulated by adenosine, forskolin, NaF, GppNHp or Mn2+. Furthermore, opiate receptor density in chemically defined medium cultured cells remained identical to that in cells cultured in 5% fetal calf serum. The acute and chronic effects of opiates on adenylate cyclase were similar for cells grown under either set of conditions.
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PMID:Neuroblastoma X glioma NG108-15 hybrid cells cultured in a serum-free chemically defined medium: effects on acute and chronic opiate regulation of adenylate cyclase activity. 300 May 35

Using neuroblastoma cells as a model of developing neurons, we have tested the hypothesis that thyroid hormones alter cAMP metabolism. Neuroblastoma cells were grown in serum-free defined medium for 48 h with or without thyroid hormones. Treatment with 20-200 nM 3,5,3'-triiodo-L-thyronine (T3) increased the accumulation of cAMP by intact cells without altering growth, gross morphology, or DNA or protein content. The increase in cAMP accumulation could be detected 5 h after the addition of T3 and was abolished by the addition of cycloheximide. The maximum stimulation produced by prostaglandin E1 was increased in T3 cells without a significant alteration of the half-maximal concentration. T4 and D-T3 in concentrations up to 20 microM did not increase cAMP accumulation. Adenylate cyclase activity in response to forskolin, guanine nucleotides, and stimulatory hormones was increased in purified membranes from cells grown in T3, suggesting that increased adenylate cyclase is probably the major mechanism of the observed response to thyroid hormone.
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PMID:Thyroid effects on adenosine 3',5'-monophosphate levels and adenylate cyclase in cultured neuroblastoma cells. 303 Jun 93

Neuroblastoma-glioma NG108-15 cells that were cultured for 48 h with the opiate antagonist, naloxone, respond to the guanosine 5'-triphosphate (GTP) analogue guanosine 5'-[beta, gamma-imido]-triphosphate (GMP-PNP) in the binding assay as the control, non-treated, cells. This was observed when the guanyl nucleotide was tested in the presence or absence of sodium chloride and also after subcellular fractionation of the membranes on a sucrose gradient which separated between two receptor-containing fractions. The findings suggest that the increase in delta type enkephalin receptors in naloxone-treated NG108-15 cells does not reflect an alteration in the interaction between the receptor and the adenylate cyclase-GTP-binding protein system.
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PMID:Up-regulation of opiate receptors by opiate antagonists in neuroblastoma-glioma cell culture: the possibility of interaction with guanosine triphosphate-binding proteins. 609 9

Neuroblastoma cells were used to study the surface distribution and organization of opiate (enkephalin) receptors and the possible relevance of changes in these variables to biological functions. Opiate receptors readily form clusters that are visible by image-intensifier fluorescent microscopy and are localized on both the cell body and processes. These clusters do not become internalized even during prolonged incubation periods. The receptors appear to pre-exist largely in a diffuse state, with only a very small number pre-existing as clusters. The clusters are induced within 1 hr and they are stable for prolonged (7-9 hr) periods, even after removal of the receptor-bound ligand. Agonists and antagonists are both equally capable of inducing receptor clustering. However, the clusters induced by agonists are different from those induced by antagonists; the former can be dispersed by treatment with dithiothreitol. This dispersion requires removal of the receptor-bound agonist, indicating that the hormone protects or stabilizes disulfide bonds which are critical for maintenance of the clustered state. Pretreatment of cells with sulfhydryl-blocking reagents (iodoacetate, iodoacetamide, and N-ethylmaleimide) prevents cluster formation but does not alter the ability of agonists to inhibit adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] activity. Neither the number nor the affinity of binding sites is altered by pretreatment with opiates. These studies suggest that at least the acute, immediate biological effects of opiates and enkephalins occur prior to and are independent of the formation of gross receptor clusters. The possible relationship of cluster formation to the actions of opiates remains to be determined.
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PMID:Cluster formation of opiate (enkephalin) receptors in neuroblastoma cells: differences between agonists and antagonists and possible relationships to biological functions. 624 85


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