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)

The primary structures of two muscarinic acetylcholine receptor (mAChR) species, designated as mAChR I and mAChR II, have been elucidated by cloning and sequence analysis of DNAs complementary to the porcine cerebral and cardiac messenger RNAs, respectively. mAChR I and mAChR II expressed in Xenopus oocytes differ from each other both in acetylcholine-induced response and in antagonist binding properties. These results, together with the differential tissue location of the two mAChR mRNAs, have indicated that pharmacologically distinguishable subtypes of the mAChR represent distinct gene products. The primary structures of two additional mammalian mAChR species, designated as mAChR III and mAChR IV, have subsequently been deduced from the nucleotide sequences of the cloned cDNAs or genomic DNAs. We report here that mAChR I and mAChR III expressed in NG108-15 neuroblastoma-glioma hybrid cells, but not mAChR II and mAChR IV, efficiently mediate phosphoinositide hydrolysis, activation of a Ca2+-dependent K+ current and inhibition of the M-current, a voltage-dependent K+ current sensitive to muscarinic agonists.
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PMID:Selective coupling with K+ currents of muscarinic acetylcholine receptor subtypes in NG108-15 cells. 284 72

The effect of chronic membrane depolarization on the regulation of muscarinic acetylcholine receptor (mAChR) number was studied in neuroblastoma cells (clone N1E-115). Receptor number was determined by a filter binding assay using 3H-quinuclidinyl benzilate (QNB) in membrane and crude cellular homogenates. Incubation with 50 microM veratridine (VTN), an activator of voltage-sensitive Na+ channels, induced a 50-200% increase in mAChR number at 24 hr, which was inhibited 80% by TTX. Scatchard analysis showed that affinity of the mAChR for 3H-QNB was not affected by VTN. Upon withdrawal of VTN, mAChR number returned to control levels within 20 hr. Chronic membrane depolarization caused by incubation in medium containing 60 mM K+ induced a TTX-insensitive 50% increase in mAChR number at 24 hr. AChE activity was unaffected by chronic membrane depolarization. The VTN-induced increase in mAChR number was not blocked by coincubation with cycloheximide or tunicamycin, both inhibitors of de novo mAChR synthesis. The rate of mAChR degradation was reduced in the presence of 50 microM VTN, with the apparent half-life increased from approximately 18 hr (control) to approximately 40 hr (VTN). Although treatment with either 1 mM 8Br-cAMP or 1 mM 8Br-GMP failed to increase mAChR number, treatment with either the inorganic Ca2+ channel blocker Co2+ (1 mM) or the organic Ca2+ channel antagonist D600 (10-100 microM) produced 40-80% increases in mAChR number. The combination of VTN and either D600 or Co2+ failed to induce a greater increase in mAChR number than incubation with VTN alone.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regulation of muscarinic acetylcholine receptor number in cultured neuronal cells by chronic membrane depolarization. 303 81

The tumor-promoting phorbol ester 4 beta-phorbol 12 beta-myristate 13 alpha-acetate (PMA), which activates protein kinase C, acted synergistically with A23187 to decrease muscarinic acetylcholine receptor (mAChR) number in neuroblastoma cells (clone N1E-115) as determined by a filter binding assay using [3H]quinuclidinyl benzilate in membrane homogenates. After a 6-h incubation, 10(-7) M PMA and 3 X 10(-7) M A23187 reduced mAChR number 30-40%, compared to the 40-50% reduction observed after treatment with 10(-3) M carbachol, a muscarinic agonist. Incubation with 3 X 10(-7) M A23187 and 10(-7) M 4 alpha-phorbol 12,13-didecanoate, an inactive phorbol ester, did not alter mAChR number. The addition of PMA and A23187 to cultures incubated with 10(-3) M carbachol caused only a modest 6% further reduction in mAChR number as compared to incubation with carbachol alone. The kinetics of the decrease in mAChR number produced by PMA/A23187 were similar to those seen after carbachol treatment. Recovery of mAChR number after treatment with either carbachol or PMA/A23187 was blocked by treatment with the protein synthesis inhibitor cycloheximide. Intact cell binding studies employing [3H]N-methylscopolamine showed that treatment with either PMA/A23187 or carbachol caused a rapid (within 15 min) loss of receptors from the cell surface prior to the decrease in total mAChR number. PMA (10(-7) M), but not 4 alpha-phorbol 12,13-didecanoate, promoted the translocation of protein kinase C activity from the cytosol to the membrane. Incubation with carbachol increased membrane-associated protein kinase C activity within 5 min with an EC50 of 3 X 10(-6) M. This increase persisted for at least 60 min in the continued presence of carbachol and was blocked by simultaneous incubation with atropine. These results suggest that activation of protein kinase C may be involved in the regulation of mAChR number in response to agonist.
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PMID:Activation of protein kinase C induces rapid internalization and subsequent degradation of muscarinic acetylcholine receptors in neuroblastoma cells. 308 82

Chronic membrane depolarization results in an increase in muscarinic acetylcholine receptor (mAChR) number in N1E-115 neuroblastoma cells. Because the mAChR interacts with the guanine nucleotide binding regulatory (G) proteins, Gi and Go, the effect of chronic membrane depolarization on the levels of subunits of these G proteins was examined. Quantitation of G protein subunit levels was performed using affinity-purified, monospecific antibodies in a quantitative immunoblot assay. Incubation with 50 microM veratridine (VTN), an activator of voltage-sensitive Na+ channels, induced a 48 +/- 15% increase in the level of the alpha subunit of Go. The effect of VTN was blocked by tetrodotoxin. On removal of VTN, the level of Go alpha decreased to control levels within 24 h. The levels of the alpha subunit of Gi and the common beta subunit were not affected by VTN treatment. These results show that in N1E-115 cells, the level of the alpha subunit of Go is regulated in a manner similar to the level of mAChR in response to chronic membrane depolarization.
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PMID:Chronic membrane depolarization regulates the level of the guanine nucleotide binding protein Go alpha in cultured neuronal cells. 313 83

Four subtypes of muscarinic acetylcholine receptor (mAChR) were stably expressed in neuroblastoma-glioma hybrid cells (NG108-15). By combining fluorescent indicator dye (fura-2) studies with electrophysiological measurements it is shown that stimulation of mAChR I and mAChR III readily leads to release of calcium from intracellular stores and to associated conductance changes, whereas stimulation of mAChR II and mAChR IV exerts no such effect. Dose-response curves describing the amplitude or the delay of the calcium rise induced by acetylcholine suggest that the apparent affinity of mAChR III for its agonist is higher by about one order of magnitude than that of mAChR I. Ionic substitution experiments and current fluctuation analysis indicate that calcium activates a K+-specific conductance of 'small' single-channel amplitude similar to the SK type. Furthermore, an outward current (M current) suppressed by activation of mAChR I and mAChR III has a single-channel amplitude corresponding to a conductance of approximately 3 pS.
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PMID:Intracellular calcium release mediated by two muscarinic receptor subtypes. 319 3

Tunicamycin, a potent inhibitor of protein glycosylation, was used to study the role of protein glycosylation in the regulation of muscarinic acetylcholine receptor (mAChR) number in cultures of N1E-115, a murine neuroblastoma cell line. At a concentration of 0.35 microgram/ml, tunicamycin inhibited macromolecular incorporation of [3H]mannose by 75-80%, whereas incorporation of [3H]leucine was reduced by only 10%. Treatment with tunicamycin caused a 30% decrease in total membrane mAChR number within 48 h as determined by a filter-binding assay using [3H]quinuclidinyl benzilate ([3H]QNB), a highly specific muscarinic antagonist. Tunicamycin also inhibited the recovery of total membrane mAChR by 70% following carbachol-induced down-regulation. The rate of mAChR degradation (control t1/2 12-14 h) was unaffected by incubation with tunicamycin. Intact cell binding studies using [3H]QNB (a membrane-permeable ligand) to measure total cellular (internal plus cell surface) mAChR and [3H]N-methylscopolamine ([3H]NMS, a membrane-impermeable ligand) to measure cell surface mAChR were conducted to determine whether tunicamycin selectively depleted cell surface mAChR. With 12 h of treatment with tunicamycin, cell surface mAChR number declined by 35%, whereas total cellular mAChR fell by only 10%. The ratio of cell surface receptor to total receptor decreased by 45% after 24 h. These results indicate that protein glycosylation is required for the maintenance of cell surface mAChR number. Incubation with tunicamycin causes a selective depletion of cell surface mAChR, implying that protein glycosylation plays a critical role in transport and/or incorporation of mAChR into the plasma membrane.
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PMID:Regulation of neuronal muscarinic acetylcholine receptor number by protein glycosylation. 394 Feb 94

Several calcium antagonists were screened for their effect on muscarinic acetylcholine receptor-mediated cyclic GMP formation in murine neuroblastoma cells (clone N1E-115). Mn2+, Ni2+, and verapamil rapidly antagonized the response noncompetitively, with the following order of potency: verapamil greater than Mn2+ greater than Ni2+. The effects of Mn2+ and Ni2+, but not those of verapamil, were largely reversed by increasing extracellular calcium concentration. Additional effects of these agents included displacement of [3H]quinuclidinyl benzilate binding by verapamil and elevation of cyclic GMP levels by Mn2+ and Ni2+ in the absence of agonists. These results are in support of the hypothesis that receptor-mediated cyclic GMP formation by these cells is dependent upon entry of calcium into the cell and demonstrate the complexity of the effects of calcium antagonists.
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PMID:Effect of some calcium antagonists on muscarinic receptor-mediated cyclic GMP formation. 629 67

Intracellular free Ca2+ concentrations ([Ca2+]i) were measured in subclones of NL308 neuroblastoma x fibroblast hybrid cells expressing each of the individual muscarinic acetylcholine receptor (mAChR) subtypes m1, m2, m3 and m4. Application of 100 microM acetylcholine (ACh) increased [Ca2+]i in all four subclones. The increased [Ca2+]i levels were significantly higher in m1- and m3-transformed cells than those in m2- and m4-transformed cells. In more than 95% of m2- and m4-transformed cells, [Ca2+]i showed sinusoidal oscillations. ACh-induced increases in [Ca2+]i were not observed in cells treated with an intracellular Ca2+ chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). Removal of extracellular Ca2+ with ethylene-glycol-bis-(beta- aminoethyl)-N,N,N',N'-tetraacetate (EGTA) did not affect the initial [Ca2+]i increases, but reduced the late phases of delta [Ca2+]i in ml- and m3-transformed cells by 20-30%. Oscillations in m2- and m4-transformed cells persisted in EGTA solution (though sometimes slowed in frequency), suggesting that they were of intracellular origin. ACh-induced delta [Ca2+]i and inositol 1,4,5-trisphosphate formation was completely suppressed by pre-treatment with 50-100 ng ml-1 Pertussis toxin (PTX) for 12 h in m2- and m4-transformed cells, but not in m1- and m3-transformed cells. In all cells, extracellular application of caffeine and ryanodine, or intracellular application of cyclic adenosine diphosphate ribose (cAD-PR) produced a rise in [Ca2+]i. ACh-induced [Ca2+]i oscillations were not observed in ryanodine-treated m2-transformed cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Inositol 1,4,5-trisphosphate formation and ryanodine-sensitive oscillations of cytosolic free Ca2+ concentrations in neuroblastoma x fibroblast hybrid NL308 cells expressing m2 and m4 muscarinic acetylcholine receptor subtypes. 776 Dec 66

The regulation of m4 muscarinic acetylcholine receptor mRNA expression by receptor activation was studied in N1E-115 neuroblastoma and AtT-20 pituitary cells that endogeneously express the m4 muscarinic receptor. Receptor concentration was measured by binding of the muscarinic receptor radioligand [3H]quinuclidinyl benzilate, and RNA-RNA solution hybridization/RNase protection assay with a m4 receptor-specific [32P]-cRNA probe was used to evaluate the levels of receptor mRNA. Treatment of both cell lines with a receptor-saturating concentration of the agonist carbachol decreased receptor number. However, there was no change in steady-state levels of m4 mAChR mRNA in both cell lines. Determination of mRNA stability in the presence of the transcription blocker actinomycin D revealed that carbachol treatment increased half-life of receptor mRNA in N1E-115 cells, but not in AtT-20 cells, suggesting that receptor activation can regulate m4 receptor mRNA stability dependently on cell type. Analysis of receptor degradation kinetics in the presence of the protein synthesis inhibitor cycloheximide showed that receptor down-regulation in N1E-115 and AtT-20 cells is sufficiently accounted for by increased receptor degradation. These results indicate than m4 muscarinic receptor down-regulation is substantially different from that of the muscarinic receptor subtypes m2 and m3 which is reported to be associated with agonist-induced reduction in receptor mRNA.
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PMID:Agonist-induced down-regulation of the m4 muscarinic acetylcholine receptor occurs without changes in receptor mRNA steady-state levels. 787 Jan 90

The electrophysiological effects of KST-5452 [3-(m-phenoxybenzylidene)-quinuclidine], an M1 muscarinic acetylcholine receptor (muscarinic AChR) binding compound, were studied in NG108-15 neuroblastoma x glioma hybrid cells transfected with m1 muscarinic AChR cDNA. Application of KST-5452 to m1-transformed NGPM1-27 cells elicited a sustained inward current associated with decreased conductance and reduced M-current relaxations at a holding potential of -20 mV. The KST-5452-induced responses were blocked by pirenzepine, suggesting that KST-5452 acts as a potent excitant via M1 muscarinic AChRs in brain neurons.
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PMID:Activation of inward current associated with M-potassium current inhibition in m1-muscarinic receptor-transformed NG108-15 cells by KST-5452, a novel cognition enhancer. 808 14


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