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)

mu-Opioid receptors mediate inhibition of the N-type calcium channel current in the human neuroblastoma cell line SH-SY5Y. We have previously shown that chronic exposure to morphine induces homologous tolerance to this effect. Here we show that chronic incubation with morphine (1 microM for three to seven days) does not, however, induce physical dependence at the level of the calcium channel current. Initial experiments were performed using the whole cell voltage-clamp technique. Chronically treated cells were bathed in superfusate which also contained morphine (1 microM). On washout of morphine the current amplitude increased by 12% and this was reversed by re-addition of morphine. Naloxone (1 microM) elicited a similar increase. However, this increase is most likely due to a reversal of the residual inhibitory effect of morphine on the calcium channel current rather than being a novel withdrawal response. Chronic exposure to morphine did not change the voltage-sensitivity of the calcium channel current or induce the appearance of a current sensitive to the L-type calcium channel agonists Bay K 8644 (3 microM) and S(+)-PN 202-791 (1 microM). In a further series of experiments the nystatin-perforated patch technique was employed in order to prevent washout of any L-type current in these cells. Under these conditions a Bay K 8644-sensitive, L-type current was unmasked following treatment with omega Conus Toxin GVIA. The peak current was depressed by omega Conus Toxin GVIA (1 microM) by approximately 90% both in control cells and cells chronically exposed to morphine. Now Bay K 8644 (3 microM) almost doubled the remaining current but the effect was equal in both groups of cells. It is concluded that chronic exposure to morphine does not induce physical dependence and a withdrawal syndrome in the human SH-SY5Y neuroblastoma cell line by changing either N-type or L-type calcium channel activity.
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PMID:Chronic exposure to morphine does not induce dependence at the level of the calcium channel current in human SH-SY5Y cells. 127 57

We have tested 36 patients with the Lambert-Eaton myasthenic syndrome for serum antibodies to voltage-gated calcium channels by using an immunoprecipitation assay with [125I] omega-conotoxin-labeled voltage-gated calcium channels extracted from a human neuroblastoma cell line, SKN-SH. Forty-four percent of these patients had significant levels of antibody (30-1,466 pM) compared with healthy control individuals (less than 15 pM). The incidence of positive sera in patients without associated small cell lung carcinoma (61%) was greater than in those patients with small cell lung carcinoma (28%). Results correlated strongly with results obtained using voltage-gated calcium channels extracted from the small cell lung carcinoma line, MAR5. Anti-voltage-gated calcium channel antibody titers did not correlate with disease severity across individuals, but longitudinal studies in 2 patients receiving immunosuppressive therapy showed a clear inverse relation between antibody titer and an electromyographic index of disease severity. The incidence of positive sera among patients with other neurological disorders was not significant, but 8 of 12 patients with rheumatoid arthritis or systemic lupus erythematosus had raised titers (30-82 pM). We conclude that the antibodies detected in this assay are heterogeneous and that some of them are likely to be implicated in this disorder of neuromuscular transmission. The assay should prove useful as an additional diagnostic aid in patients with Lambert-Eaton myasthenic syndrome.
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PMID:Calcium channel autoantibodies in the Lambert-Eaton myasthenic syndrome. 164 44

More than one type of voltage-gated calcium channel has been identified in muscle cells and neurons. Many specific organic and inorganic blockers of the conventional, slowly inactivating high threshold (L) calcium channel have been reported. No specific blockers of the low threshold (T) channel have been as yet identified. Amiloride, a potassium sparing diuretic, has now been shown to selectively block the low threshold calcium channel in mouse neuroblastoma and chick dorsal root ganglion neurons. The selective blockade of the T-type calcium channel will allow identification of this channel in different tissues and characterization of its specific physiological role.
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PMID:Amiloride selectively blocks the low threshold (T) calcium channel. 245 Dec 91

Digital imaging fluorescence microscopy was used to investigate the effect of the B subunit of cholera toxin on calcium homeostasis in neuroblastoma N18 cells. The B subunit, which binds specifically to ganglioside GM1 in the outer leaflet of the cell membrane, was found to induce a sustained increase of intracellular calcium concentration ([Ca2+]i). The increase in [Ca2+]i was not observed in the absence of extracellular calcium, or in the presence of the calcium chelator EGTA, and was blocked by nickel. The B subunit was also found to induce an influx of manganese ions, as indicated by a quench of the intracellular fura-2 fluorescence. These data suggest that the B subunit induces an increase in calcium influx in N18 cells. Potassium-induced depolarization also stimulated manganese influx; however, after the onset of depolarization-induced influx, the B subunit had no further effect. This occlusion suggests involvement of voltage-dependent calcium channels. Treatment with BayK8644, a dihydropyridine agonist selective for L-type calcium channels, induced manganese influx that was not altered by the B subunit and apparently blocked the effect of the B subunit itself. Furthermore, the dihydropyridine L-type channel antagonists niguldipine or nicardipine completely inhibited B subunit-induced manganese influx. Thus, the B subunit-induced manganese influx is likely due to activation of an L-type voltage-dependent calcium channel. Spontaneous influx of manganese ions was also inhibited by nicardipine or niguldipine and by exogenous gangliosides. Ganglioside GM1 was more potent than GM3, but globoside had no significant effect. The modulation of L-type calcium channels by endogenous ganglioside GM1 has important implications for its role in neural development, differentiation, and regeneration and also for its potential function in the electrical excitability of neurons.
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PMID:Endogenous ganglioside GM1 modulates L-type calcium channel activity in N18 neuroblastoma cells. 751 36

1. The transcriptional regulation of the rat brain L-type calcium channel alpha 1D subunit (RB alpha 1D) gene was investigated using NG108-15 neuroblastoma-glioma cells. 2. Differentiation of NG108-15 cells in the presence of prostaglandin E1 or retinoic acid resulted in the appearance of mRNA encoding the RB alpha 1D subunit detected using Northern blot analysis. 3. A rat genomic DNA library was screened, and a 15.2-kb clone was isolated and partially sequenced which included part of the 5' upstream sequence through the initial part of intron 2 of the RB alpha 1D gene. 4. Deletion analysis, using a CAT reporter gene and transfected NG108-15 cells, revealed that the 1.2-kb 5'-upstream sequence from the RB alpha 1D gene contains cis-acting positive and negative regulatory elements. A deletion of the 3' end of exon 1 also suggested the presence of regulatory elements in the first exon. 5. DNase footprinting of exon 1 of the RB alpha 1D gene revealed two regions protected from digestion by specific protein binding, and the second region included an (ATG)7 trinucleotide repeat sequence. Electrophoretic mobility shift assays confirmed nuclear protein(s) binding to the (ATG)7 sequence. 6. The (ATG)7 sequence functions as a enhancer when linked to a thymidine kinase promoter and a CAT reporter gene. 7. These results provide the initial description of the transcriptional regulation of the RB alpha 1D gene and identify a novel enhancer that consists of an (ATG)7 trinucleotide repeat sequence.
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PMID:Transcriptional regulation of the neuronal L-type calcium channel alpha 1D subunit gene. 755 31

Monoclonal antibodies that recognize skeletal muscle dihydropyridine-sensitive calcium channel subunits were used to identify similar proteins in neuronal and small cell carcinoma cell lines. alpha 1-related proteins were detected by FACS analysis on the surface of human neuroblastoma (IMR 32) and small cell carcinoma (DMS 273 and DMS 114) cell lines. alpha 1-like polypeptides from these cells were isolated and partially characterized. The polypeptides exhibit an M(r) similar to that of the L-type channel alpha 1 subunit and are recognized by two distinct anti-alpha 1 mAbs. The data provide biochemical evidence for structural similarities between the alpha 1 subunit of small cell carcinoma and neuronal cell lines. Similarly, an alpha 2-like protein was characterized from these cells. Because alpha 2 is a subunit shared by many subtypes of calcium channels, these data suggest that subunits other than the pore-forming alpha 1 subunit may play an important role in the etiology of Lambert-Eaton syndrome. We demonstrate directly that small cell carcinoma and a cell line derived from peripheral neurons share L-type calcium channel-related proteins and a protein common to many voltage-gated calcium channel subtypes. These data support a model that proposes that cross-reactivity of anti-tumor cell antibodies with presynaptic elements, possibly calcium channels, plays a role in the development of Lambert-Eaton syndrome.
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PMID:Alpha 1 and alpha 2 Ca2+ channel subunit expression in human neuronal and small cell carcinoma cells. 807 Jun 39

1. Putrescine has been implicated in modulating cytoplasmic calcium concentration and is correlated with selective neuronal vulnerability in cerebral ischaemia. In order to determine whether putrescine modulates voltage-activated calcium channels, whole-cell and single channel patch clamp experiments were performed with N1E-115 mouse neuroblastoma cells. 2. L-type calcium channel currents showed a 34 +/- 21% increase (n = 6 cells) during external application of 1 mM putrescine. There was no change in the kinetics of the current and no shift in the current-voltage relationship along the voltage axis. 3. T-type calcium channel currents were not affected by 1 mM putrescine. 4. The effect of putrescine on single L-type calcium channels was studied using the cell-attached configuration of the patch clamp technique. Putrescine (5 mM) applied to the bathing solution, but not present in the pipette, caused an increase in open time of the single channel current without changing the conductance of the channel. In 345 depolarizing steps compiled from three cells, the number of channel openings longer than 3 ms increased from six to seventy-six, and the number of channel openings longer than 9 ms increased from zero to twenty-seven. This single channel study supports the hypothesis that putrescine acts on the L-type channel from the inside of the cell. 5. External application of 1 mM spermine and 1 mM spermidine had no effect on T- and L-type calcium channels. Thus, the effect of putrescine is probably not mediated by the higher polyamines. 6. In order to test whether the effect of putrescine is mediated by a second messenger, specific protein kinase C and cyclic AMP-dependent protein kinase inhibitors, staurosporine and KT5720, respectively, were applied prior to putrescine. When cells were preconditioned with 200 nM staurosporine, the increase of the L-type calcium current by 1 mM putrescine was inhibited. By contrast, 200 nM KT5720 did not inhibit the putrescine effect. Therefore, the increase of L-type channel currents by putrescine may be mediated by protein kinase C but not the cyclic AMP-dependent protein kinase. 7. The putrescine-induced enhancement of the L-type calcium channel activity may play an important role in calcium-induced neurotoxicity.
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PMID:The effect of polyamines on voltage-activated calcium channels in mouse neuroblastoma cells. 839 76

The bradykinin regulation of calcium channel currents in NG108-15 neuroblastoma x glioma hybrid cells was examined, in order to determine: (1) which type of bradykinin receptors mediates the inhibition of N-type calcium channels in these cells; and (2) whether bradykinin can modulate other types of calcium channels in these cells. Bradykinin inhibited both N- and L-type calcium channels in NG108-15 cells, with EC50S of 10 +/- 2 nM and 29 +/- 7 nM, respectively. The inhibition of both L- and N-type calcium channels by bradykinin (100 nM) could be completely inhibited by the bradykinin B2 receptor antagonist Hoe 140 (10 nM). Bradykinin appeared to inhibit that portion of the L-type calcium channel current that was also reversibly inhibited by omega-conotoxin GVIA. The bradykinin inhibition of the L-type calcium channel current was partly reduced by pretreatment of the cells with pertussis toxin, whereas the inhibition of the N-type current was pertussis toxin-insensitive. In some cultures it was observed that the bradykinin B1 receptor agonist desArg9bradykinin inhibited the L-type calcium channel current.
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PMID:Bradykinin inhibition of N- and L-type calcium channel currents in NG108-15 cells. 914 48

Phosphorylation of specific amino acid residues is believed to be crucial for the agonist-induced regulation of several G protein-coupled receptors. This is especially true for the three types of opioid receptors (mu, delta, and kappa), which contain consensus sites for phosphorylation by numerous protein kinases. Protein kinase C (PKC) has been shown to catalyze the in vitro phosphorylation of mu- and delta-opioid receptors and to potentiate agonist-induced receptor desensitization. In this series of experiments, we continue our investigation of how opioid-activated PKC contributes to homologous receptor down-regulation and then expand our focus to include the exploration of the mechanism(s) by which mu-opioids produce PKC translocation in SH-SY5Y neuroblastoma cells. [D-Ala2,N-Me-Phe4,Gly-ol]enkephalin (DAMGO)-induced PKC translocation follows a time-dependent and biphasic pattern beginning 2 h after opioid addition, when a pronounced translocation of PKC to the plasma membrane occurs. When opioid exposure is lengthened to >12 h, both cytosolic and particulate PKC levels drop significantly below those of control-treated cells in a process we termed "reverse translocation." The opioid receptor antagonist naloxone, the PKC inhibitor chelerythrine, and the L-type calcium channel antagonist nimodipine attenuated opioid-mediated effects on PKC and mu-receptor down-regulation, suggesting that this is a process partially regulated by Ca2+-dependent PKC isoforms. However, chronic exposure to phorbol ester, which depletes the cells of diacylglycerol (DAG) and Ca2+-sensitive PKC isoforms, before DAMGO exposure, had no effect on opioid receptor down-regulation. In addition to expressing conventional (PKC-alpha) and novel (PKC-epsilon) isoforms, SH-SY5Y cells also contain a DAG- and Ca2+-independent, atypical PKC isozyme (PKC-zeta), which does not decrease in expression after prolonged DAMGO or phorbol ester treatment. This led us to investigate whether PKC-zeta is similarly sensitive to activation by mu-opioids. PKC-zeta translocates from the cytosol to the membrane with kinetics similar to those of PKC-alpha and epsilon in response to DAMGO but does not undergo reverse translocation after longer exposure times. Our evidence suggests that direct PKC activation by mu-opioid agonists is involved in the processes that result in mu-receptor down-regulation in human neuroblastoma cells and that conventional, novel, and atypical PKC isozymes are involved.
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PMID:Role of protein kinase C (PKC) in agonist-induced mu-opioid receptor down-regulation: II. Activation and involvement of the alpha, epsilon, and zeta isoforms of PKC. 993 Jul 31

Parathyroid hormone-related protein (PTHrP) was discovered a dozen years ago as a product of malignant tumors. It is now known that PTHrP is a paracrine factor with multiple biological functions. One such function is to relax smooth muscle by inhibiting calcium influx into the cell. In the central nervous system, PTHrP and its receptor are widely expressed in neurons in the cerebral cortex, hippocampus and cerebellum. The function of PTHrP in the CNS is not known. Previous work has shown that expression of the PTHrP gene is depolarization-dependent in cultured cerebellar granule cells and depends specifically on L-type voltage sensitive calcium channel (L-VSCC) Ca(2+) influx. PTHrP has also been found to be capable of protecting these cells against kainic acid-induced excitotoxicity. Here, we tested the idea that mice with a PTHrP-null CNS might display hypersensitivity to kainic acid excitotoxicity. We found that these mice were six-fold more sensitive than control littermate mice to kainic-acid-induced seizures as well as hippocampal c-Fos expression. PTHrP-null embryonic mixed cerebral cortical cultures were more sensitive to kainic acid than control cultures, and PTHrP addition was found to be protective against kainate toxicity in both PTHrP-null and control cultures. By whole-cell techniques, PTHrP was found to reduce L-VSCC Ca(2+) influx in cultured mouse neuroblastoma cells. We conclude that PTHrP functions as a component of a neuroprotective feedback loop that is structured around the L-type calcium channel. This loop appears to be operative in vivo as well as in vitro.
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PMID:Endogenous parathyroid hormone-related protein functions as a neuroprotective agent. 1187 96


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