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)

Gangliosides, sialic acid-containing glycosphingolipids, enhance tumor formation in experimental animals and are associated with tumor progression and metastasis in humans. The mechanism(s) for this activity is (are) unknown. One possibility is enhanced platelet activation, since the interaction of platelets with tumor cells contributes to tumor cell arrest in the vascular compartment. We have previously shown that neuroblastoma tumor gangliosides (NBTG) enhance platelet adenosine triphosphate (ATP) secretion, aggregation, and adhesion. We determined that these NBTG effects are specific for collagen and are mediated through an alpha2 beta1 integrin-dependent mechanism. This report describes the effects of NBTG on a physiologically relevant model of collagen-alpha2 betal interaction. Platelet adhesion to immobilized native collagen fibers similar to those found in the extracellular matrix of blood vessels was determined. Platelet adhesion is enhanced by NBTG in a concentration-dependent manner. Incubation with concentrations of 1 and 10 microM NBTG increased platelet adhesion by 9% and 52%, respectively, compared to less than 1% in controls not incubated with gangliosides (P = 0.001 and P < 0.0001, respectively). In addition to increasing the number of adherent platelets, NBTG promoted more rapid attachment. In NBTG-incubated platelets, platelet adhesion began after a 5-min lag phase and was maximal at 30 min compared to a 20-min lag phase and maximal adhesion at 60 min for control platelets. At 30 min this difference was significant (P = 0.017); however, by 120 min there was no difference between NBTG and controls (P = 0.259). NBTG also induces platelet adhesion at collagen concentrations (0.1 microg) that failed to support adhesion of control platelets. These effects of NBTG require Mg2+ or Mn2+ ions but are not supported by Zn2+ or Ca2+ ions. Furthermore, preincubation of platelets with a blocking antibody (6F1) to the integrin collagen receptor alpha2 beta1 abrogates all of the effects of NBTG. These results indicate that tumor gangliosides enhance platelet adhesion to extracellular matrix collagen and promote rapid stabilization of the collagen-alpha2 beta1 interaction, the initial steps in platelet activation.
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PMID:Effects of neuroblastoma tumor gangliosides on platelet adhesion to collagen. 900 4

ATP activates a nonselective cation current by stimulating the P2Z receptor in NG108-15 cells--a hybrid cell line of the mouse neuroblastoma N18TG-2 cells and the rat glioma C6Bu-1 cells. Recently, the P2X7 receptor was cloned from the rat brain and was found to have electrophysiological properties similar to those of the P2Z receptor. We examined the expression of P2X7 receptor mRNA in NG108-15 cells as well as in their parent cell lines, N18TG-2 and C6Bu-1 cells, by reverse transcription-polymerase chain reaction (RT-PCR). The cDNA templates from these cell lines were amplified with primers specific to the P2X7 receptor sequence. Positive signals were detected in the RT-PCR products from NG108-15 and N18TG-2 cells but not from C6Bu-1 cells. We next examined the effect of ATP on the membrane current in N18TG-2 cells and C6Bu-1 cells by whole-cell voltage clamp. In N18TG-2 cells, ATP induced a sustained current with a reversal potential of 9.3 +/- 1.2 mV (n = 22) in a concentration-dependent manner with an EC50 of 1.76 +/- 0.18 mM (n = 36). In contrast, ATP (1 mM) did not induce any current in C6Bu-1 cells. The ATP-induced current in N18TG-2 cells resembled that in NG108-15 cells in the following points: (a) The currents did not desensitize significantly. (b) EC50 values of ATP are of millimolar order. (c) Benzoylbenzoyl-ATP was a more potent agonist than ATP. (d) The current was larger in methanesulfonate than in Cl- external solution. (e) The current was larger at lower external Mg2+ concentrations. These results suggest that the hybrid NG108-15 cells possess a P2X7 receptor like the P2Z receptor and that the ability of expressing this channel originates from N18TG-2 cells but not from C6Bu-1 cells.
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PMID:Identification of P2X7 (P2Z) receptor in N18TG-2 cells and NG108-15 cells. 948 14

1. SH-SY5Y human neuroblastoma cells were investigated with whole-cell and perforated patch recording methods. 2. Besides a quickly activating delayed rectifier channel and a HERG-like channel, a slowly activating potassium channel with biophysical properties identical to those of rat eag (r-eag) channels was detected, here referred to as h-eag. 3. h-eag shows a marked Cole-Moore shift, i.e. the activation kinetics become very slow when the depolarization starts from a very negative holding potential. In addition, extracellular Mg2+ and Ni2+ strongly slow down activation. 4. Application of acetylcholine induces a fast block of the current when recorded in the perforated patch mode. This block is presumably mediated by Ca2+, as about 1 microM intracellular Ca2+ completely abolished h-eag outward current. 5. When cells were grown in the presence of 10 microM retinoic acid in order to synchronize the cell line in the G1 phase of the cell cycle, h-eag current was reduced to less than 5 % of the control value, while the delayed rectifier channel was expressed more abundantly. Down-regulation of h-eag by long-term exposure to retinoic acid was paralleled by a right shift in the activation potential of HERG-like channels. 6. Acute application of 10 microM retinoic acid blocked the delayed rectifier channel but enhanced the h-eag current. 7. Thus, our results show that human neuroblastoma cells express in a cell cycle-dependent manner an [Mg2+]o-dependent potassium channel (h-eag) which is blocked by submicromolar concentrations of intracellular Ca2+.
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PMID:Characterization of an eag-like potassium channel in human neuroblastoma cells. 949 Aug 15

Carboxymethylcellulase (CMCase) was extracted and purified from an angiosperm parasite Cuscuta reflexa free from beta-glucosidase and other enzyme activities. The molecular mass and Stokes' radius of the purified enzyme are 144 kDa and 44 A, respectively. The diffusion coefficient and frictional ratio of the enzyme were 5.15 x 10(-7) cm2/sec and 1.27. The SDS-PAGE revealed homotetrameric nature of the enzyme with a subunit molecular mass of 35 +/- 1 kDa. Titration against DTNB and NBS revealed 19 sulfhydryl groups and 8 tryptophan groups, respectively, per mole of the enzyme. A sharp pH optimum at 5.0 was obtained. Cuscuta CMCase activity is unique amongst plant endoglucanases in being stimulated by Mg2+ and Mn2+ ions and by various thiols. Reaction product analysis, mode of enzyme action and substrate specificity test suggest the endo- nature of the purified CMCase. The enzyme showed K(m) value of 26 +/- 1 mg/ml for carboxymethylcellulose (sodium salt).
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PMID:Physico-chemical and functional characterization of a high molecular weight carboxymethylcellulase from Cuscuta reflexa. 949 45

Metal ions such as Ca2+, Mg2+, or Zn2+, are important for many cell functions, for example, signal transduction and the modulation of enzyme activity. The relationship between apoptosis and metal cations, especially Ca2+, has been described in many reports. We have investigated the role of metal cations in the regulation of apoptosis in the mouse neuroblastoma cell line, Neuro-2A. When Neuro-2A cells were treated with ethylene diaminetetraacetic acid (EDTA), apoptosis was detected as growth inhibition, DNA fragmentation with a ladder pattern in agarose gel electrophoresis, and nuclear decomposition. However, in case of the treatment with ethylene glycol bis- (beta-aminoethyl ether) N,N,N',N'-tetraacetic acid (EGTA), which has a higher chelating specificity for Ca2+ than EDTA, DNA fragmentation was not detected. Moreover, the apoptosis induced by EDTA was inhibited by exogenous Zn2+. The membrane permeable Zn2+ chelator N,N,N',N'-tetrakis (2-pyridylmethyl)ethylenediamine (TPEN) also induced apoptosis of the Neuro-2A cells, and addition of equimolar exogenous Zn2+ or Cu2+, but not Mn2+ or Fe2+, prevented TPEN-induced apoptosis. The results suggest that Zn2+ may be a key regulator of apoptosis in Neuro-2A cells.
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PMID:Induction of apoptosis in Neuro-2A cells by Zn2+ chelating. 966 37

Swelling-induced activation of the outwardly rectifying anion current, ICl, swell, is modulated by intracellular ATP. The mechanisms by which ATP controls channel activation, however, are unknown. Whole cell patch clamp was employed to begin addressing this issue. Endogenous ATP production was inhibited by dialyzing N1E115 neuroblastoma cells for 4-5 min with solutions containing (microM): 40 oligomycin, 5 iodoacetate, and 20 rotenone. The effect of ATP on current activation was observed in the absence of intracellular Mg2+, in cells exposed to extracellular metabolic inhibitors for 25-35 min followed by intracellular dialysis with oligomycin, iodoacetate, and rotenone, after substitution of ATP with the nonhydrolyzable analogue AMP-PNP, and in the presence of AMP-PNP and alkaline phosphatase to dephosphorylate intracellular proteins. These results demonstrate that the ATP dependence of the channel requires ATP binding rather than hydrolysis and/or phosphorylation reactions. When cells were swollen at 15-55%/min in the absence of intracellular ATP, current activation was slow (0.3-0.8 pA/pF per min). ATP concentration increased the rate of current activation up to maximal values of 4-6 pA/pF per min, but had no effect on the sensitivity of the channel to cell swelling. Rate of current activation was a saturable, hyperbolic function of ATP concentration. The EC50 for ATP varied inversely with the rate of cell swelling. Activation of current was rapid (4-6 pA/pF per min) in the absence of ATP when cells were swollen at rates >/=65%/min. Intracellular ATP concentration had no effect on current activation induced by high rates of swelling. Current activation was transient when endogenous ATP was dialyzed out of the cytoplasm of cells swollen at 15%/min. Rundown of the current was reversed by increasing the rate of swelling to 65%/min. These results indicate that the channel and/or associated regulatory proteins are capable of sensing the rate of cell volume increase. We suggest that channel activation occurs via ATP-dependent and -independent mechanisms. Increasing the rate of cell swelling appears to increase the proportion of channels activating via the ATP-independent pathway. These findings have important physiological implications for understanding ICl, swell regulation, the mechanisms by which cells sense volume changes, and volume homeostasis under conditions where cell metabolism is compromised.
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PMID:ATP dependence of the ICl,swell channel varies with rate of cell swelling. Evidence for two modes of channel activation. 1005 19

In mouse neuroblastoma N18TG2 cells prelabeled with [3H]arachidonic acid ([3H]AA) the biosynthesis of 2-arachidonoylglycerol (2-AG) is induced by ionomycin in a fashion sensitive to an inhibitor of diacylglycerol (DAG) lipase, RHC 80267, but not to four different phospholipase C (PLC) blockers. Pulse experiments with [3H]AA showed that ionomycin stimulation leads to the sequential formation of [3H]phosphatidic acid ([3H]PA), [3H]DAG, and [3H]2-AG. [3H]2-AG biosynthesis in N18TG2 cells prelabeled with [3H]AA was counteracted by propranolol and N-ethylmaleimide, two inhibitors of the Mg2+/Ca2(+)-dependent brain PA phosphohydrolase. Pretreatment of cells with exogenous phospholipase D (PLD) led to a strong potentiation of ionomycin-induced [3H]2-AG formation. These data indicate that DAG precursors for 2-AG in intact N18TG2 cells are obtained from the hydrolysis of PA and not through the activation of PLC. The presence of 2% ethanol during ionomycin stimulation failed to elicit the synthesis of [3H]phosphatidylethanol and did not counteract the formation of [3H]PA, thus arguing against the activation of PLD by the Ca2+ ionophore. Selective inhibitors of secretory phospholipase A2 and the acyl-CoA acylase inhibitor thimerosal significantly reduced [3H]2-AG biosynthesis. The implications of these latter findings, and of the PA-dependent pathways of 2-AG formation described here, are discussed.
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PMID:Phosphatidic acid as the biosynthetic precursor of the endocannabinoid 2-arachidonoylglycerol in intact mouse neuroblastoma cells stimulated with ionomycin. 1021 92

Because Mg2+ and Li+ ions have similar chemical properties, we have hypothesized that Li+/Mg2+ competition for Mg2+ binding sites is the molecular basis for the therapeutic action of lithium in manic-depressive illness. By fluorescence spectroscopy with furaptra-loaded cells, the free intracellular Mg2+ concentration within the intact neuroblastoma cells was found to increase from 0. 39 +/- 0.04 mM to 0.60 +/- 0.04 mM during a 40-min Li+ incubation in which the total intracellular Li+ concentration increased from 0 to 5.5 mM. Our fluorescence microscopy observations of Li+-free and Li+-loaded cells also indicate an increase in free Mg2+ concentration upon Li+ incubation. By 31P NMR, the free intracellular Mg2+ concentrations for Li+-free cells was 0.35 +/- 0. 03 mM and 0.80 +/- 0.04 mM for Li+-loaded cells (final total intracellular Li+ concentration of 16 mM). If a Li+/Mg2+ competition mechanism is present in neuroblastoma cells, an increase in the total intracellular Li+ concentration is expected to result in an increase in the free intracellular Mg2+ concentration, because Li+ displaces Mg2+ from its binding sites within the nerve cell. The fluorescence spectroscopy, fluorescence microscopy, and 31P NMR spectroscopy studies presented here have shown this to be the case.
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PMID:Competition between Li+ and Mg2+ in neuroblastoma SH-SY5Y cells: a fluorescence and 31P NMR study. 1035 21

Pineal and retinal melatonin synthesis is controlled by the enzymatic activity of arylalkylamine N-acetyltransferase (AA-NAT, EC 2.3.1.87), which is regulated by light/dark signals and circadian factors. This enzyme converts serotonin to N-acetylserotonin by the transfer of an acetyl group from acetyl coenzyme A. Endogenous AA-NAT instability during routine purification has made enzyme characterization difficult, but now a stable recombinant protein for AA-NAT has been synthesized to investigate the intrinsic biochemical properties of AA-NAT from a rat pineal cDNA encoding a 205 amino acid, 23 kilodalton protein, by using a glutathione-S-transferase (GST) fusion protein system. Recombinant GST-AA-NAT showed substrate specificity for arylalkylamines and stability at 4 degrees C; however, the enzyme activity was reduced by 40% upon preincubation at 37 degrees C for 2 hr. GST-AA-NAT is preferentially phosphorylated by either cyclic AMP- or cyclic GMP-dependent kinases in vitro, but no detrimental effect was observed on AA-NAT enzymatic activity. Among the metal cations tested in this study, Ca2+, Mg2+, Mn2+, Fe2+, and Co2 showed little or no inhibitory potency, while either 1 mM Zn2+ or 0.1 mM Cu2+ nearly abolished the enzymatic activity. GST-AA-NAT enzyme activity is also inhibited by reagents that are known biochemically to modify thiol groups (N-ethylmaleimide, NEM) and histidine residues (p-chloromercuribenzoate, NBS and diethyl pyrocarbonate, DEPC), suggesting the presence of essential cysteine and histidine moieties. Moreover, preincubation of acetyl CoA completely protects the recombinant AA-NAT from inactivation by NEM and DEPC, indicating that specific cysteine and histidine residues may be at the acetylation site. The conclusion is that the biochemical properties of rat recombinant AA-NAT is similar to the endogenous pineal and retinal AA-NAT with respect to the sensitivity to temperature, metal cations, as well as the thiol modification reagents. These data also suggest that the phosphorylation status of the AA-NAT does not affect enzymatic activity directly, and histidine residues are potentially important residues required for high catalytic activity.
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PMID:Biochemical characterization of recombinant serotonin N-acetyltransferase. 1045 Oct 24

The alpha1 beta1 integrin, an inserted (1) domain containing collagen receptor, is expressed in the cell surface membrane of normal and malignant cells, and may play a role in their migration through tissues or in metastatic spread. Here we report that a functional anti-human alpha1beta1 integrin monoclonal antibody (mAb) (1B3.1) directly and specifically binds plastic bound recombinant human alpha1 I-domain protein containing the collagen binding site. Detection was diminished by acidification of the I-domain protein but was enhanced by increasing concentrations of Mg2+ cation. Furthermore, we detected binding of the mAb to proteins from the ocular fluids of 6 patients, with the highest concentration, corresponding to 22.1 ng/ml of I-domain, found in a sample from the eye of a patient with metastatic lung adenocarcinoma. Interestingly, we found that both SKNSH neuroblastoma cells and virally transformed human T cells adhered specifically to plastic wells coated with either immobilized collagen IV or alpha1 I-domain. MAb I B3.1 inhibited adhesion to collagen IV but not to immobilized I-domain. These results suggest a novel function for cell free alpha1 I-domain as a substrate for cellular adhesion, which may have relevance in tumor spread in vivo.
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PMID:Analysis of cell-free human alpha1 integrin with a monoclonal antibody to the I-domain: detection in ocular fluid and function as an adhesion substrate. 1193 86


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