Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027819 (neuroblastoma)
 27,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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

A monoclonal antibody, designated M148, produced by the hybridoma technique from spleen cells of mice immunized with human medulloblastoma, was found by indirect immunofluorescence to bind to normal human platelets (both PlA1 positive and PlA1 negative) and megakaryocytes, as well as to some medulloblastoma and neuroblastoma cells and cell lines and certain other solid tumours. No binding was observed to other marrow constituents, nor to any other normal tissue examined. The antibody bound to platelets from a patient with the Bernard-Soulier syndrome but not to thrombasthenic platelets. It immunoprecipitated glycoproteins IIb and IIIa from 125I-labelled normal platelet membranes, and completely inhibited ADP-induced fibrinogen binding and aggregation of platelets. Aggregation was also inhibited in response to adrenaline, collagen, thrombin, sodium arachidonate and the ionophore A23187; clot retraction was partially inhibited. The antibody was without effect on thromboxane formation or 5-hydroxytryptamine (5HT) secretion in response to thrombin, but inhibited 5HT secretion in response to arachidonate. It did not inhibit factor VIII binding or agglutination in response to ristocetin, but completely inhibited factor VIII binding in response to thrombin. These findings suggest that the epitopes are close to the fibrinogen and factor VIII binding sites on glycoproteins IIb/IIIa, and that the lack of these glycoproteins is sufficient explanation for the pattern of dysfunction observed in thrombasthenic platelets, without invoking any other membrane abnormality.
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PMID:A monoclonal antibody binding to human medulloblastoma cells and to the platelet glycoprotein IIB-IIIA complex. 623 27

In their study of prostaglandin E1 (PGE1)-sensitive adenylate cyclase (AC) in rat brain homogenates, Collier and Roy claimed that the activity of this enzyme is inhibited by opiates. They also proposed that opiates exert their analgesic and allied effects by inhibiting AC of neurones that are normally stimulated by E prostaglandins. Studies using neuroblastoma x glioma hybrid cells supported this hypothesis. However, subsequent studies with mammalian brain and rat brain tissue slices yielded conflicting results. PGE1 also inhibits platelet aggregation, probably through activation of platelet AC. Gryglewski et al. showed that morphine inhibits the anti-aggregating effect of PGE1 on ADP- and adrenaline-induced platelet aggregation, and suggested that the inhibition by morphine is mediated through platelet AC activity. We report here our attempts to reproduce the results of Gryglewski et al. and our examination of the effect of morphine on PGE1-sensitive AC activity in platelet lysates and on PGE1-induced accumulation of cyclic AMP in intact platelets. The possible existence of opiate receptors in platelets was also assessed by direct binding studies with 3H-etorphine. In contrast to Gryglewski et al., we could not detect any effect of opiates on the aggregation of human platelets, nor did we find any other evidence supporting the presence of opiate receptors in these cells. Thus we conclude that the presence of opiate receptors in human platelets is unlikely.
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PMID:Do human platelets have opiate receptors? 625 32

The sequence of early events which follow the administration of E coli lipopolysaccharide (LPS) to cultured mouse neuroblastoma (C-1300) cells was investigated. Emphasis was placed on cellular energy metabolism in order to establish whether or not an energy failure occurred and whether it was a primary or a secondary effect. Exposure of cultured neuroblastoma cells to LPS produced rapid changes in the regulatory parameters of energy metabolism, an oxidation of intramitochondrial pyridine nucleotides, and a decline in cellular [ATP]/[ADP] [Pi], which were followed by alterations in mitochondrial morphology. In spite of the changes in individual parameters at early stages of exposure to LPS, the cellular energy producing systems remained tightly controlled and the rate of ATP synthesis was maintained at a constant and undiminished level. This allowed the cells to preserve their ionic gradients as manifested by high intracellular [K+] and unaltered transmembrane electrical and pH gradients. These early changes in mitochondrial metabolism were not accompanied by detectable leakage of mitochondrial matrix enzymes into the cytosol, which indicated that mitochondrial membrane remained intact. After longer exposure to LPS, the rate of ATP synthesis declined, the mitochondrial membrane became permeable to high molecular weight substances (matrix enzymes), and intracellular [K+] began to decrease (K+ leakage). It was concluded that responses of mitochondrial metabolism are one of the early events in endotoxemia.
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PMID:Early cellular responses in vitro to endotoxin administration. 626 76

Nafazatrom (Bay g 6575) was explored for its ability to inhibit platelet aggregation. In vitro, it had no effect on ADP, serotonin, epinephrine, or collagen induced platelet aggregation in platelet rich plasma of monkeys. On the other hand, in vivo it was a powerful inhibitor of ADP induced platelet aggregation as measured by the in vivo platelet aggregation recording instrument described previously (Ambrus et al., 1976). This effect was potentiated by dipyridamole. On the other hand, following parenteral administration of Bay g 6575, no ex vivo inhibition was noticed of ADP, serotonin, epinephrine, and collagen induced platelet aggregation. The hypothesis was presented that Bay g 6575 acts by increasing prostacyclin synthesis and/or release or interferes with its decomposition. This may explain in vivo activity; rapid decomposition may explain inability to demonstrate ex vivo activity. This also explains potentiation by the phosphodiesterase inhibitor dipyridamole. Bay g 6575 also was highly effective as a platelet aggregation inhibitor in monkeys after oral administration. In mice, Bay g 6575 increased circulation time of intravenously injected polyploid Ehrlich ascites tumor cells. In Furth-Wistar rats implanted with Furth-Columbia Wilms' tumor, in A/J mice implanted with C1300 neuroblastoma and in Wistar rats implanted with SMT-2A (Kim) breast cancer, Bay g 6575 significantly reduced spontaneous pulmonary metastasis. On the other hand, no effect was seen in the metastatic rate of NIH renal adenocarcinoma in BALB/cCr mice.
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PMID:Study of platelet aggregation in vivo. IX. Effect of nafazatrom on in vivo platelet aggregation and spontaneous tumor metastasis. 628 24

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

Adenylate cyclase in NG108-15 (neuroblastoma X glioma hybrid) cells is responsive to both stimulatory and inhibitory ligands. Bordetella pertussis toxin (PT) catalyzes the ADP-ribosylation of a 41,000-Da peptide believed to be a subunit of the putative guanyl nucleotide-binding protein (Gi) involved in cyclase inhibition and abolishes inhibitory effects of opiate agonists. In studying the effects of PT on opiate receptors, we found that [3H]enkephalinamide binding was reduced by approximately 90% in membranes prepared from cells incubated with PT compared to control membranes. Agonist affinity, assessed by enkephalinamide competition for [3H]diprenorphine-binding sites, was markedly reduced in cells incubated with PT. Furthermore, inhibition by guanylylimidodiphosphate of ligand binding to opiate receptors was reduced following treatment with PT. The number of opiate receptors assessed by [3H]diprenorphine binding was unaltered by PT. These data are consistent with the hypothesis that PT-catalyzed ADP-ribosylation impairs the interaction of Gi with the inhibitory receptor-ligand complex, effectively uncoupling the inhibitory receptor from Gi and the cyclase catalytic unit.
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PMID:ADP-ribosylation of adenylate cyclase by pertussis toxin. Effects on inhibitory agonist binding. 631 76

Administration of Escherichia coli endotoxin to NB41A3 neuroblastoma cells in culture produced decreases in 1) intracellular [ATP]/[ADP], 2) flux through pyruvate dehydrogenase (PDH), and 3) total intracellular calcium. These effects were reversible if endotoxin was washed off within 10-15 min, but not if it remained in contact with the cells for 30 min or more. Minor, reversible morphological and functional alterations occurred during the initial phase, but after 30-min exposure to the toxin, the damage was irreversible. A model is proposed in which early, reversible weak binding of endotoxin to the plasma membrane partially blocks inward calcium flux, lowering the intracellular [Ca2+] and consequently the PDH phosphatase activity which activates the PDH complex. If endotoxin is removed at this stage, these processes are reversed and the cell recovers. If not, the toxin becomes irreversibly incorporated into the cell with consequent damage to the plasma membrane and organelles, which leads to massive ion movements resulting in cellular hydration with ultimate disruption of mitochondria and cell death.
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PMID:Cellular effects of endotoxin in vitro. II. Reversibility of endotoxic damage. 635 30

Intramitochondrial substrate metabolism was examined in cultured neuroblastoma NB41A3 cells exposed to endotoxin in order to elucidate possible causes for the changes in [ATP]/[ADP][Pi] and [NAD+]/[NADH] reported by us previously in these cells [1]. Flux through pyruvate dehydrogenase (PDH), measured with [1-14C]-pyruvate, was inhibited by 54% within 10 min in endotoxin-treated cells (0.99 nmol/min/mg dry wt vs 0.46 nmol/min/mg dry wt). In contrast, flux through 2-oxoglutarate dehydrogenase, measured with [1-14C]-glutamate was unaltered (0.79 nmol/min/mg dry wt). Dichloroacetate, an inhibitor of PDH kinase, restored flux through PDH to control levels. In endotoxin-treated cells, only 44% of the total PDH complex was in the active (nonphosphorylated) form as compared to 72% in control cells. Equilibrium uptake studies with 45Ca2+ and atomic absorption measurements showed that intracellular [Ca2+] in endotoxin-treated cells was about 20% lower than in control cells. It is postulated that binding of endotoxin to the plasma membrane triggers a sequence of events that lead to an initial decline in intracellular calcium concentration and that this latter event may be responsible for the inhibition of PDH phosphatase and consequent conversion of the complex to its inactive phosphorylated form.
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PMID:Cellular effects of endotoxin in vitro. I. Effect of endotoxin on mitochondrial substrate metabolism and intracellular calcium. 635 31


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