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)

Choleragen (cholera toxin) activates adenylate cyclase in HeLa cells, which contain less than 15,000 toxin receptors per cell, in a time- and concentration-dependent manner. Activation is blocked by the addition of the oligosaccharide chain of the ganglioside GM1, the receptor for the toxin. When the cells are preincubated with choleragen at 4 degrees C and then incubated with oligosaccharide at 37 degrees C, adenylate cyclase is activated less than 10%. When the preincubation phase is above 18 degrees C, adenylate cyclase becomes activated and the amount of activation depends on the time of preincubation. This inhibitory effect of the oligosaccharide is also observed with human lymphocytes and rat glial C6 cells but not with Friend erythroleukemic and mouse neuroblastoma N18 cells. The latter two cell lines have large numbers ot toxin receptors, whereas the former two cell lines have few receptors. When the number of toxin receptors in HeLa and C6 cells is increased by treating the cells with GM1, activation of adenylate cyclase by choleragen is no longer blocked by the oligosaccharide. The oligosaccharide has a corresponding effect on the displacement of bound 125I-choleragen. When bound to cells at 4 degrees C, most of the radiotoxin is displaced from HeLa, C6, and lymphocytes but not from Friend, N18, or HeLa cells pretreated with GM1. In untreated HeLa cells, dissociation of toxin-receptor complexes by the oligosaccharide depends on the time and temperature of complex formation; above 18 degrees C, the toxin rapidly becomes stably bound to the cells. The inhibitory effect of GM1 oligosaccharide us reversible, as, once it is removed, the small amount of toxin that remains bound can activate adenylate cyclase. These results are consistent with a model in which choleragen, which is multivalent, must bind to several GM1 molecules on the cell surface in order to subsequently activate adenylate cyclase. Lateral mobility of toxin-receptor complexes may be required only to achieve multivalent binding in cells with few receptors.
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PMID:Mechanism of action of cholera toxin: effect of receptor density and multivalent binding on activation of adenylate cyclase. 625 58

The lag period for activation of adenylate cyclase by choleragen was shorter in mouse neuroblastoma N18 cells than in rat glial C6 cells. N18 cells have 500-fold more toxin receptors than C6 cells. Treatment of C6 cells with ganglioside GM1 increased the number of toxin receptors and decreased the lag phase. Choleragen concentration also effected the lag phase, which increased as the toxin concentration and the amount of toxin bound decreased. The concentration, however, required for half-maximal activation of adenylate cyclase depended on the exposure time; at 1.5, 24, and 48 hr, the values were 200, 1.1, and 0.35 PM, respectively. Under the latter conditions, each cell was exposed to 84 molecules to toxin. The length of the lag period was temperature-dependent. When exposed to choleragen at 37, 24, and 20 degrees C, C6 cells began to accumulate cyclic AMP after 50, 90, and 180 min, respectively. In GM1-treated cells, the corresponding times were 35, 60, and 120 min. Cells treated with toxin at 15 degrees C for up to 22 hr did not accumulate cAMP, whereas above this temperature they did. Antiserum to choleragen, when added prior to choleragen, completely blocked the activation of adenylate cyclase. When added after the toxin, the antitoxin lost its inhibitory capability in a time and temperature-dependent manner. Cells, however, could be preincubated with toxin at 15 degrees C, and the antitoxin was completely effective when added before the cells were warmed up. Finally, cells exposed to choleragen for less than 10 min at 37 degrees C accumulated cyclic AMP when shifted to 15 degrees C. Under optimum conditions at 37 degrees C, the minimum lag period for adenylate cyclase activation in these cells was 10 min. These findings suggest that the lag period for choleragen action represents a temperature-dependent transmembrane event, during which the toxin (or its active component) gains access to adenylate cyclase.
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PMID:Mechanism of action of cholera toxin: studies on the lag period. 625 59

Exposure of mouse neuroblastoma cell line N4TGl to opiates or [D-Ala2,D-Leu5] enkephalin produced a naloxone-reversible inhibition of cyclic AMP synthesis and prevented, in a concentration-dependent manner, the formation of both ganglioside GM2 (GalNAc-[NeuNAc]-Gal-Glc-ceramide) from GM3 (NeuNAc-Gal-Glc-ceramide) and ganglioside GM1 (Gal-GalNAc-[NeuNAc]-Gal-Glc-ceramide) from GM2 in cell-free extracts. In contrast, the receptor-mediated elevation of intracellular cyclic AMP levels by agents such as prostaglandin E1 (in the presence of isobutylmethylxanthine) or the addition of the cyclic AMP derivatives (dibutyryl cyclic AMP) markedly stimulated the activities of UDP-GalNAc:GM3,N-acetylgalactosaminyltransferase and UDP-Gal:GM2,galactosyltransferase. An overall increase in the synthesis of gangliosides more complex than GM3 was also observed in the mouse neuroblastoma x hamster brain explant hybrid cell line NCB-20 following elevation of cyclic AMP levels by treatment with serotonin and pargyline. The data presented support the hypothesis that cyclic AMP may have a role in the regulation of sialoglycosphingolipid biosynthesis.
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PMID:Possible role of cyclic AMP in the receptor-mediated regulation of glycosyltransferase activities in neurotumor cell lines. 626 98

Cellular differentiation of the neuroblastoma X glioma hybrid cell line NG108-15 was measured and correlated with quantitative changes in the cells' ganglioside composition. The degree of differentiation was measured using an enzymatic marker, choline acetyltransferase (CAT), which is responsible for neurotransmitter synthesis in this cell line. Differentiation of these cells is commonly induced by agents such as dibutyryl cyclic adenosine 3':5'-monophosphate (Bt2cAMP). However, in our studies, we observed that these cells "self-differentiated," in the absence of chemical inducers, when the cells became dense in culture. The differentiation marker, CAT specific activity, rose from 150 to more than 400 pmol/min/mg of protein as cell density increased, attaining a level higher than that achieved by treatment with Bt2cAMP. Differentiation of sparse cultures could be induced by conditioned medium removed from dense cultures. This effect was not due to depletion of a serum component from the medium by the cells, since it was not mimicked by serum depletion or inhibited by addition of fresh serum to the conditioned medium. These data suggest that cell density-dependent differentiation was caused by release of a factor from the cells which induced differentiation in a concentration-dependent manner. Gangliosides, therefore, were purified from sparse control cultures, dense cultures, and cultures treated with the differentiating agents Bt2cAMP, prostaglandin E1 (plus theophylline), or butyric acid. Quantitative thin layer chromatography revealed that all of the cultures contained the four gangliosides GM3, GM2, GM1, and GD1a. The concentration of one of the gangliosides, GM2, increased markedly (up to 12-fold) during differentiation. The GM2 concentration correlated closely with the level of CAT activity in the different cultures (r = 0.99). These data demonstrate that the ganglioside concentration in these cells is regulated during differentiation, a finding consistent with a possible role for gangliosides in the differentiated phenotype.
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PMID:Ganglioside composition is regulated during differentiation in the neuroblastoma X glioma hybrid cell line NG108-15. 630 Mar 57

The effects of exogenous GM1 and GD1a on S20Y murine neuroblastoma cells were assessed by monitoring morphology, tumorigenicity, mitotic index, and plating efficiency. S20Y cells were seeded at a density equivalent to 5 X 10(4) cells per 35-mm tissue culture dish; 38-42 hr after seeding (preconfluent stage) the cells were treated for 12 hr with 100 micrograms of ganglioside per ml of medium in which the serum content was reduced from 10% to 0.5%. Analysis of the cell lipids indicated that added ganglioside became tightly associated with the membrane during the 12-hr exposure. GM1 treatment resulted in increased projections on the cell surface and fine structures projecting from the cell processes. GD1a treatment resulted in a reduction in the cellular mitotic index. Plating efficiency was reduced by both GM1 and GD1a. Neither ganglioside affected tumorigenicity of the S20Y cells. Twelve hours after removal of the added ganglioside and exposure of the cells to normal medium, the ganglioside composition of the membranes from treated cells approached that of the controls, and the ganglioside-induced effects had been reversed. These results suggest that addition of specific gangliosides induces different cellular responses and that these changes are dependent upon the continued presence of the ganglioside.
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PMID:Effects of exogenous GM1 and GD1a on S20Y neuroblastoma cells. 648 20

A nonganglioside factor(s) present in Sigma types II and III mixed bovine brain ganglioside preparations synergises with suboptimal amounts of serum to induce proliferation specifically in nondividing B 103 neuroblastoma cultures. The active substance is nondialysable and soluble in water as well as in chloroform-methanol mixtures of 1:1-4:1 (vol/vol). It is completely insoluble in ether and acetone at room temperature. Biological activity survives heating to 70 degrees C in the presence of 0.1 M HCl for 1 h as well as boiling at neutral pH. Loss of activity occurs on heating to 70 degrees C for 1 h with 1 M HCl or 1 M NaOH. The activity is insensitive to digestion with neuraminidase, trypsin, pronase, and phospholipases A2 and C. The factor cochromatographs with gangliosides on Dowex AG 50W and Sephadex G100 and is partially recovered with GM1 on DEAE-Sepharose, but may be isolated in a ganglioside-free fraction by sequential chromatography on Sephadex LH20 and silicic acid columns. The substance(s) has the properties of a water-soluble proteolipid protein, the amino acid composition being reported. It is not immunologically cross-reactive with antibodies to GM1 ganglioside or the major proteolipid protein of myelin.
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PMID:Characterization and partial purification of a ganglioside-associated mitogen. 661 41

Ganglioside GM1 promoted neuritogenesis of neuroblastoma cells, neuro-2a clone, in monolayer culture. GM1 bound to neuro-2a cells in three distinct forms, one removable by treatment with serum-containing solutions, one serum-resistant and labile to trypsin treatment, and one resistant to serum and trypsin treatments. The proportions among the three forms of cell-associated GM1 varied in relation to duration of exposure to ganglioside, ganglioside concentration in the medium, and number of cells in culture. The form removable by serum was predominant at the initial stages of association and at the highest ganglioside concentrations (over 10(-6)M); the trypsin-labile and -stable forms tended to increase with increasing cell number and decreasing ganglioside concentration. The neuritogenic effect of GM1 was higher when neuro-2a cells were incubated for 24 h in the presence of GM1 and fetal calf serum. Under this condition the percentage of neurite-bearing cells increased from 11% of control to 62% at the optimal ganglioside concentration of 10-4M. The effect was still present, although to a lower extent (from 11% to 28% of neurite-bearing cells), when cells were first exposed for only 2 h to GM1, then washed and incubated for 24 h in the presence of fetal calf serum. The trypsin-labile and -stable forms of cell-associated GM1 had a fundamental role in the effect, whereas the form removable by serum was not involved. The preparation of GM1 used was extremely pure (99%) and, in particular, had a peptide contamination, if any, less than 1:20,000-1:50,000.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Promotion of neuritogenesis in mouse neuroblastoma cells by exogenous gangliosides. Relationship between the effect and the cell association of ganglioside GM1. 669 71

The influence of divalent cations on glycosphingolipid metabolism was examined in the NB41A mouse neuroblastoma clonal cell line. HPLC methods were utilized to quantitate the effects on neutral glycolipids and monosialogangliosides. NB41A cells were shown to contain GM3, GM2, GM1, GD3, and GD1a by HPLC and TLC. The neutral glycosphingolipids consisted of glucosylceramide (GlcCer), lactosylceramide (LacCer), GalNAc (beta 1 leads to 4) Gal(beta 1 leads to 4)Glc(beta 1 leads to 1)Cer (GgOse3Cer), and GalNAc(beta 1 leads to 3)Gal(alpha 1 leads to 4) Gal(beta 1 leads to 4)Glc(beta 1 leads to 1)Cer (GbOse4Cer) according to their HPLC behavior. Cells grown in the presence of 1.85 mM-EGTA showed a two-to threefold increase in GM3 whereas other glycosphingolipids were only slightly affected. When cells were grown in the presence of 1.45 mM-EGTA plus 0.4 mM-EDTA a similar increase in GM3 was observed but this change was now accompanied by decreases in GM2, GM1, GgOse3Cer. The EGTA-EDTA effects were reversed when growth was in the presence of Ca2+ sufficient to bind all chelator. Mn2+ replacement reversed the chelator effects differentially; GM2 and GM1 levels were the most sensitive to increases in Mn2+ concentration; GgOse3Cer and GbOse4Cer were also sensitive, whereas GM3 was the least affected. These results suggest calcium serves an important regulatory role on GM3 levels and that manganese concentration may regulate the levels of galactosamine-containing glycolipids in mouse NB41A neuroblastoma cells.
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PMID:Effects of divalent cations on the glycolipids from cultured mouse neuroblastoma cells. 680 99

Cholera toxin (CT) covalently linked to horseradish peroxidase (HRP) is a specific cytochemical marker for its receptor, the monosialoganglioside GM1. The binding and endocytosis of exogenous [3H]GM1 by cultured murine neuroblastoma cells (line 2A [CCl-131] ), which contain predominantly GM3, was examined by quantitative electron microscope autoradiography. The relationship between exogenous receptor, [3H]GM1, and CT HRP was studied in double labeling experiments consisting of autoradiographic demonstration of [3H]GM1 and cytochemical visualization of HRP. Exogenous [3H]GM1 was not degraded after its endocytosis by cells for 2 h at 37 degrees C. Quantitative studies showed similar grain density distributions in cells treated with [3H]GM1 alone and in cells treated with [3H]GM1 followed by CT-HRP. Qualitative studies conducted in double labeling experiments showed autoradiographic grains over the peroxidase-stained plasma membrane, lysosomes, and vesicles at the trans aspect of the Golgi apparatus. The findings indicate that exogenous glycolipid is associated with the plasmid membrane of deficient cells and undergoes endocytosis. The quantitative ultra-structural autoradiographic studies are consistent with the hypothesis that the spontaneous endocytosis of exogenous [3H]GM1 controls the subsequent uptake of CT-HRP.
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PMID:Endocytosis of exogenous GM1 ganglioside and cholera toxin by neuroblastoma cells. 682 31

The fluorescence photobleaching recovery method has been used to determine the lateral mobilities of membrane lipids and proteins during the cell cycle of synchronized C1300 mouse neuroblastoma cells (clone Neuro-2A). As probes for lipid mobility, 3,3'-dioctadecylindocarbocyanine iodide and a fluorescein-labeled analog of ganglioside GM1 were used. Membrane proteins were labeled with rhodamine-labeled rabbit antibodies against mouse E14 cells. For both lipid probes the diffusion coefficients reach a minimum in mitosis, increase 2- to 3-fold during G1, remain constant at maximal values during S, and decrease again shortly before mitosis. Membrane proteins also exhibit minimum diffusion coefficients in mitosis, followed by a similar rise in G1. However, as cells proceed through S and G2, the lateral mobility of the membrane proteins gradually decreases. It is argued that lipid mobility is controlled by the fluidity of the membrane lipid matrix whereas protein mobility is governed also by other constraints.
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PMID:Lateral diffusion of membrane lipids and proteins during the cell cycle of neuroblastoma cells. 692 4


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