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)

(+/- ) -cis-3,4-Dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]- benzamide (U-54494A), structurally related to a kappa opioid agonist U-50448H, is a potent anticonvulsant without analgesic or sedative effects of the opioid agonist in intact animal studies (VonVoigtlander et al., 1987). To explore the mechanism of its anticonvulsant action, we investigated the interaction of U-54494A with the voltage-gated sodium channel using the whole cell patch clamp technique in mouse neuroblastoma cells (NIE-115). The drug reversibly and dose-dependently reduced the tetrodotoxin-sensitive inward Na current without affecting its activation or inactivation kinetics or the reversal potential. Nearly half of this resting block by 50 microM U-54494A at a holding potential of -80 mV was reversed upon further hyperpolarization to -120 mV. We also observed a hyperpolarization shift (9.3 mV) of the steady-state slow inactivation curve in the presence of 50 microM drug with no shift in the steady-state activation or the fast inactivation curves. These results indicate that the drug interacts with the resting and the slowly inactivated channels. The drug appears not to interact with the open state, judging from the absence of a time-dependent block in chloramine-T-treated cells. The recovery rate of the inactivated channel was markedly delayed by the drug, and apparently is responsible for its use-dependent block upon repetitive depolarizations. Our results suggest that voltage- and use-dependent block of the Na channel by U-54494A may be an important pharmacological basis for its anticonvulsant action.
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PMID:Block of sodium channel current by anticonvulsant U-54494A in mouse neuroblastoma cells. 130 69

Whole-cell voltage-clamp techniques were used in order to define the effects of delta-9-tetrahydrocannabinol (THC) on the voltage-gated sodium current in neuroblastoma cells. With regard to the inward sodium current, THC decreased the peak amplitude and increased both the time to peak and tau for recovery. The reversal potential was unchanged, suggesting that channel selectivity for sodium was not altered by the drug. With regard to the outward sodium current, THC had no effect on the peak amplitude, time to peak or tau for recovery. This functional alteration of the voltage-gated sodium channel may contribute to the depressant effects of the cannabinoid.
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PMID:Delta-9-tetrahydrocannabinol depresses inward sodium current in mouse neuroblastoma cells. 164 21

Whole-cell voltage-clamp techniques were used to study the comparative effects of delta-9-tetrahydrocannabinol (THC) and its principal metabolite, 11-hydroxy-delta-9-tetrahydrocannabinol (11-OH-THC), on the voltage-gated sodium current in neuroblastoma cells. The parent compound markedly depressed the inward sodium current with minimal reduction of the outward current, demonstrating that the effects of the drug were related to the membrane potential. In addition, THC reduced the reversal potential, indicating that the drug modified the ion selectivity of the channel. 11-OH-THC similarly depressed inward sodium current; however, in marked contrast to the effects of the parent compound, the drug equally depressed the outward voltage-gated sodium current, indicating that its effects were not related to the membrane potential. Furthermore, 11-OH-THC differed from THC in that it did not alter the reversal potential. The results demonstrate that THC and its 11-OH metabolite both reduce inward sodium current, but their effects on the outward current and ion selectivity are distinctly different. The sum of the actions of these two cannabinoids on the voltage-gated sodium channel provides a plausible cellular basis for THC's depression of action potentials in vivo and for some of its central depressant effects.
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PMID:Differential effects of delta-9-tetrahydrocannabinol and its 11-hydroxy metabolite on sodium current in neuroblastoma cells. 166 10

Biochemical events leading to the formation of mature membrane-associated sodium channel proteins are not completely understood. We have recently purified a protein from the cytoplasm of brain cells, which is able to become incorporated into liposomes and induce neurotoxin-dependent sodium permeability. Here we report data on a monoclonal antibody derived against this protein. This antibody crossreacts with cell membrane preparations. The antibody binding to viable neuroblastoma cells is inhibited by veratrine, indicating that membrane molecules antigenically related to the cytoplasmic protein may also be related to the voltage-gated sodium channel.
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PMID:Possible relationship of brain cytoplasmic tetrodotoxin-sensitive protein to voltage-gated sodium channel shown by monoclonal antibody. 215 3

U-54494A, 3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzamide, has been shown to be a potent and long-acting anticonvulsant without analgesic or sedative effects on intact animals. The persistence of anticonvulsant activity after a decline in its concentration in the brain implies the conversion of the parent drug into active metabolites. In this study, two major metabolites of U-54494A, U-83892E [cis-N-(2-aminocyclohexyl)-3,4-dichlorobenzamide] and U-83894A [cis-N-(2-methylaminocyclohexyl)-3,4-dichlorobenzamide], were identified. The synthetic metabolites displayed anticonvulsant activity against electric shock in experimental animals and blocked voltage-gated sodium channel in N1E-115 neuroblastoma cells in voltage- and use-dependent manner by interacting with the inactivated channels as well as with the channels in the resting state (like the parent compound). These observations may provide one explanation for the long duration of the anticonvulsant activity of the parent compound U-54494A and further underscore the importance of voltage-dependent sodium channels in neuronal excitability, especially during seizures.
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PMID:Two metabolites of anticonvulsant U-54494A: their anticonvulsant activity and interaction with sodium channel. 838 24

The binding characteristics of saxitoxin (STX), a known voltage-gated sodium channel blocker, and its analog saxitoxinol (STXOL), were studied in neuroblastoma, peritoneal macrophage, hepatocytes and PC-12 cell lines. 3H-STXOL bound to the cell-surface sites which appear to be the same as those occupied by 3H-STX and which can, therefore, be identified as STX receptors. The relative agreement of respective Kd obtained by saturation, competition, association and dissociation kinetics for STX and STXOL suggest the absence of any artifact in binding measurements. Unlike STX, STXOL was non-toxic to mice by intratracheal instillation. The major advantage of using 3H-STXOL is that the tritium label is not exchangeable. Data from this study suggest that 3H-STXOL can be used to identify STX receptors at 37 degrees C.
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PMID:Comparative binding and toxicity of saxitoxin and saxitoxinol in mice and in cultured cells. 906 78

Effects of some naturally occurring steroids and synthetic analogues on the cation flux through the cation channel of the 5-HT3 receptor and the voltage-gated and tetrodotoxin-sensitive sodium channel were studied in N1E-115 mouse neuroblastoma cells by measuring the 2-min influx of the organic cation [14C]-guanidinium. The cation fluxes in intact cells were either induced by 2 min exposure of the cells to 5-hydroxytryptamine (5-HT, 100microM) or to veratridine (1 mM). Influx of [14C]-guanidinium through both channels was concentration-dependently inhibited by all compounds studied. The rank order of potency for inhibition of the 5-HT3 receptor-induced cation flux was clomiphene approximately/= cyproterone acetate > estradiol > progesterone approximately/= allotetrahydrodeoxycorticosterone > alfaxalone approximately/= testosterone > aldosterone > dexamethasone. With the exception of dexamethasone and testosterone, which were more potent at the voltage-dependent sodium channel, and progesterone and testosterone, which were about nearly equipotent in inhibiting both cation channels, the steroids were twofold (alfaxalone, allotetrahydrodeoxycorticosterone) to 107-fold (cyproterone acetate) more potent at the 5-HT3 receptor channel than at the voltage-gated sodium channel. The potencies of the steroids (and the synthetic analogues) for inhibition of the 5-HT3 receptor-induced [14C]-guanidinium influx were correlated with their lipophilicity (log P values). A similar correlation between log P values and pIC50 values for the steroid-induced inhibition of the veratridine-evoked cation influx through the voltage-gated sodium channel was only found when cyproterone acetate (a compound with extremely low inhibitory potency at this channel) was not included in the regression analysis. The results indicate that both the 5-HT3 receptor channel and the voltage-gated sodium channel are targets for steroids. The relationship between most of the compounds in inhibiting both cation channels and lipophilicity is compatible with a common mechanistic principle in steroid-induced inhibition of the two channels, i.e. a nonspecific hydrophobic interaction with certain membrane lipids in the neighbourhood of the two channels.
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PMID:Inhibition by steroids of [14C]-guanidinium flux through the voltage-gated sodium channel and the cation channel of the 5-HT3 receptor of N1E-115 neuroblastoma cells. 1054 23

Sodium channel genes are highly regulated. To begin analyzing the human brain sodium channel subtype II gene, SCN2A, at the transcriptional level, we mapped multiple transcriptional start sites within a 397 bp stretch of the 5'-UTR and -flanking region. When inserted into a basic luciferase reporter vector, this 397 bp region can promote luciferase expression in transiently transfected neuroblastoma cells, but not in non-neuronal cells. Thus, this study provides the initial description of a functional promoter in a human voltage-gated sodium channel gene.
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PMID:Identifying the promoter region of the human brain sodium channel subtype II gene (SCN2A). 1100 Apr 91

The voltage-gated sodium channel NaV1.8 (SNS, PN3) is thought to be a molecular correlate of the dorsal root ganglion (DRG) tetrodotoxin resistant (TTX-R) Na+ current. TTX-R/NaV1.8 is an attractive therapeutic drug target for inflammatory and neuropathic pain on the basis of its specific distribution in sensory neurones and its modulation by inflammatory mediators. However, detailed analysis of recombinant NaV1.8 has been hampered by difficulties in stably expressing the functional protein in mammalian cells. Here, we show stable expression and functional analysis of rat NaV1.8 (rNaV1.8) in the rat DRG/mouse N18Tg2 neuroblastoma hybridoma cell line ND7-23. Rat NaV1.8 Na+ currents were recorded (789 +/- 89 pA, n=62, over 20-cell passages) that qualitatively resembled DRG TTX-R in terms of gating kinetics and voltage-dependence of activation and inactivation. The local anaesthetic drug tetracaine produced tonic inhibition of rNaV1.8 (mean IC50 value 12.5 microM) and in repeated gating paradigms (2-10 Hz) also showed frequency-dependent block. There was a correlation between the ability of several analogues of the anticonvulsant/analgesic compound lamotrigine to inhibit TTX-R and rNaV1.8 (r=0.72, P<0.001). RT-PCR analysis of wild type ND7-23 cells revealed endogenous expression of the beta1 and beta3 accessory Na+ channel subunits-the possibility that the presence of these subunits assists and stabilises expression of rNaV1.8 is discussed. We conclude that the neuroblastoma ND7-23 cell line is a suitable heterologous expression system for rNaV1.8 Na+ channels in that it allows stable expression of a channel with biophysical properties that closely resemble the native TTX-R currents in DRG neurones. This reagent will prove useful in the search for pharmacological inhibitors of rNaV1.8 as novel analgesics.
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PMID:Heterologous expression and functional analysis of rat Nav1.8 (SNS) voltage-gated sodium channels in the dorsal root ganglion neuroblastoma cell line ND7-23. 1497 98

The voltage-gated sodium channel beta2-subunit (beta2) is a member of the IgCAM superfamily and serves as both an adhesion molecule and an auxiliary subunit of the voltage-gated sodium channel. Here we found that beta2 undergoes ectodomain shedding followed by presenilin (PS)-dependent gamma-secretase-mediated cleavage. 12-O-Tetradecanoylphorbol-13-acetate treatment or expression of an alpha-secretase enzyme, ADAM10, resulted in ectodomain cleavage of beta2 in Chinese hamster ovary cells. Subsequent cleavage of the remaining 15-kDa C-terminal fragment (beta2-CTF) was independently inhibited by three specific gamma-secretase inhibitors, expression of the dominant negative form of PS1, and in PS1/PS2 knock-out cells. gamma-Secretase inhibitor treatment also increased endogenous beta2-CTF levels in neuroblastoma cells and mouse primary neuronal cultures. In a cell-free gamma-secretase assay, we detected gamma-secretase activity-dependent generation of a 12 kDa beta2 intracellular domain (ICD), which was loosely associated with the membrane fraction. To assess the functional role of beta2 processing by gamma-secretase, we tested whether N-[N-(3,5-difluorophenylacetyl-l-alanyl)]-S-phenylglycine t-butylester (DAPT), a specific gamma-secretase inhibitor, would alter beta2-mediated cell adhesion and migration. We found that DAPT inhibited cell-cell aggregation and migration in a wound healing assay carried out with Chinese hamster ovary cells expressing beta2. DAPT also reduced migration of neuroblastoma cells in a modified Boyden chamber assay. Since DAPT treatment resulted in increased beta2-CTF levels, we also tested whether beta2-CTFs or beta2-ICDs would directly affect cell migration by overexpressing recombinant proteins. Interestingly, elevated levels of beta2-CTFs, but not ICDs, also blocked cell migration by 81 to 93%. Together, our findings show for the first time that beta2 is a PS/gamma-secretase substrate and gamma-secretase mediated cleavage of beta2-CTF is required for cell-cell adhesion and migration of beta2-expressing cells.
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PMID:Presenilin/gamma-secretase-mediated cleavage of the voltage-gated sodium channel beta2-subunit regulates cell adhesion and migration. 1583 46


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