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)

Using receptor-selective agonists and antagonists, the possible presence of both A2a and A2b adenosine receptor subtypes coupled to activation of adenylyl cyclase was investigated in NG108-15 neuroblastoma x glioma hybrid cells. The relatively non-selective adenosine receptor agonist 5'-(N-ethyl carboxamido)-adenosine (NECA; 1 nM-300 microM) produced a biphasic increase in adenylyl cyclase activity in cell homogenates, best fitted to two components with high (EC50 0.7 microM) and low (EC50 16.0 microM) potency, respectively. The selective adenosine A2a receptor agonist CGS-21680 (1 nM-300 microM) also produced a biphasic increase in adenylyl cyclase. The NECA-dependent increase in adenylyl cyclase activity was almost completely inhibited by the non-selective adenosine receptor antagonist xanthine amine congener (XAC; 30 microM), but only partially inhibited by the selective A2a adenosine antagonist 8-(3-chlorostyryl)caffeine (CSC; 1 microM). Experiments were also performed to investigate the time course of NECA-induced desensitization of putative A2a and A2b receptor responses. The A2a-response was quantified using 10 microM CGS-21680, whilst the A2b response was quantified using 100 microM NECA in the presence of 1 microM CSC. The t0.5 for desensitization for each subtype was found to be around 20 min. Neither activation (with dibutyryl cAMP; 1 mM) nor inhibition (with H-89; 10 microM) of cyclic AMP-dependent protein kinase altered the ability of NECA pretreatment to desensitize A2a or A2b receptor-activated adenylyl cyclase. However zinc (200 microM), an inhibitor of G-protein coupled receptor kinase 2 (GRK2), significantly reversed the agonist-induced desensitization of A2a and A2b receptor-activated adenylyl cyclase. These experiments suggest the co-existence of A2a and A2b receptors coupled in a stimulatory fashion to adenylyl cyclase in NG108-15 cells. Furthermore desensitization of A2a and A2b responses occurs at the same rate and may involve a G-protein-coupled receptor kinase.
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PMID:Evidence for co-expression and desensitization of A2a and A2b adenosine receptors in NG108-15 cells. 951 70

The potential effect of inhibition of phospholipase C on the response of Gi-coupled receptors was investigated in neuroblastoma x glioma hybrid (NG108-15) cells. The phospholipase C specific inhibitor 1-[6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl]-1H -pyrrole-2,5-dione (U73122), which did not affect basal and forskolin-stimulated adenylyl cyclase activities, time- and dose-dependently blocked delta-opioid receptor-mediated inhibition of adenylyl cyclase activity, the EC50 (0.5 microM) of which was consistent with that for inhibition of bradykinin-dependent phospholipase C activation (EC50 = 1 microM). U73122 treatment also blocked functional responses of m4 muscarinic receptor and alpha2-adrenoceptor in NG108-15 cells and three opioid receptors (mu, delta and opioid receptor-like receptor (ORL1)) in human neuroblastoma SK-N-SH cells. 1-[6-((17Beta-3-Methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl]-2, 5-pyrrolidinedione (U73343), an inactive analog of U73122, did not show any effect, which suggests that the blockade by U73122 of Gi-coupled receptor-mediated signaling is probably mediated through inhibition of phospholipase C, although a possible direct modification of G proteins can not be excluded. Furthermore, treatment with U73122 but not U73343 blocked the GTP-induced inhibition of adenylyl cyclase, indicating blockade at the level of Gi proteins.
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PMID:Suppression of phospholipase C blocks Gi-mediated inhibition of adenylyl cyclase activity. 954 54

Acute incubation of NMDA with neuroblastoma x glioma hybrid (NG108-15) cells or neuroblastoma SK-N-SH cells produced significant attenuation of nociceptin/orphanin FQ (N/OFQ)-induced activation of G protein and inhibition of adenylyl cyclase. The attenuation of N/OFQ signaling by NMDA was dose-dependent, blockable by NMDA antagonists, and not observed in cells lacking NMDA receptors, indicating that the effect of NMDA is mediated by the NMDA receptor. Furthermore, NMDA antagonist pretreatment greatly attenuated N/OFQ-induced acute homologous desensitization of ORL1. Interestingly, the signaling induced by etorphine, an opioid agonist of wide spectrum, was sensitive to NMDA treatment in NG108-15 but insensitive in SK-N-SH cells, suggesting differential modulation of opioid signaling by NMDA. The attenuation effects of NMDA on mu opioid receptor-mediated signaling were also observed.
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PMID:Attenuation of nociceptin/orphanin FQ-induced signaling by N-methyl-D-aspartate in neuronal cells. 955 29

Calcitonin gene-related peptide (CGRP) mediates its effects by binding to specific receptors which are positively coupled to adenylyl cyclase. CGRP(8-37), a CGRP fragment devoid of the N-terminal region, was shown to be a competitive CGRP receptor antagonist. Only a limited amount of data exists on the usefulness of this ligand in studying CGRP receptors. In the present study, we used [125I]-hCGRP(8-37) to characterize CGRP receptors in porcine lung and human neuroblastoma cell (SK-N-MC) membranes. [125I]-hCGRP(8-37) displayed specific and high affinity binding in both membrane preparations. Displacement studies using [125I]-hCGRP(8-37) and the agonist CGRP revealed the presence of high and low affinity CGRP binding sites in SK-N-MC cell and porcine lung membranes. Addition of guanylimidodiphosphate [Gpp(NH)p] shifted the competition curve to the right and changed the two affinity states of the receptor to a single affinity in SK-N-MC cell membranes. On the other hand, in porcine lung membranes, the whole competition curve was shifted to the right while maintaining the two affinity states. Thus, our data indicate that the new radioligand [125I]-hCGRP(8-37) is a useful tool for characterizing CGRP receptors and their coupling to guanine nucleotide binding proteins.
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PMID:Differential effects of guanine nucleotides on [125I]-hCGRP(8-37) binding to porcine lung and human neuroblastoma cell membranes. 957 46

Activation of phospholipase C (PLC) in response to stimulation of delta-opioid, m4 muscarinic and alpha2 adrenergic receptors was observed in NG108-15 cells. Treatment with PLC specific inhibitors, U73122 and ET-18-OCH3, blocked delta-opioid receptor-mediated activation of G proteins with no effect on opioid binding to the receptors. U73122 treatment also suppressed functional responses of m4 muscarinic and alpha2 adrenergic receptors in NG108-15 cells. Furthermore, the G protein activation mediated by mu- and delta-opioid receptors and opioid receptor-like receptor (ORL1) were abolished by U73122 in SK-N-SH neuroblastoma cells. Inhibition of adenylyl cyclase induced by high concentrations of GTP was blocked by U73122, suggesting that blockade is at the level of G proteins. Our results thus indicated that inhibition of PLC leads to blockade of Gi protein activation mediated by opioid receptors or other Gi-coupled receptors.
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PMID:Inhibition of phospholipase C blocks opioid receptor-mediated activation of Gi proteins. 959 56

Activation of the delta-opioid receptor in NG108-15 neuroblastoma X glioma hybrid cells results in a transient increase at the intracellular level of inositol-1,4,5-triphosphate [Ins(1,4,5)P3]. This time course in the transient increase in the Ins(1,4,5)P3 level is distinctly different from that observed in the homologous opioid receptor desensitization as measured by the inhibition of adenylyl cyclase activity. One probable mechanism for this rapid loss in Ins(1,4,5)P3 response is the feedback regulation of the phospholipase C activity. Regulation by protein phosphorylation was suggested by the observations that the opioid-mediated response was potentiated by calphostin C, an inhibitor of protein kinase C (PKC), and was abolished by either phorbol-12-myristate-13-acetate, a PKC activator, or calyculin A, a protein phosphatase1/2A inhibitor. The direct phosphorylation of phospholipase C was demonstrated by immunoprecipitation of PLC-beta3 from metabolically labeled NG108-15 cells challenged with the delta-selective agonist [D-Pen2, D-Pen5]enkephalin (DPDPE). A time- and DPDPE concentration-dependent and naloxone-reversible increase in the PLC-beta3 phosphorylation can be demonstrated. This PLC-beta3 phosphorylation was mainly due to PKC activation because pretreatment of NG108-15 cells with calphostin C could block the DPDPE effect. Activation of the PLC-beta3 by DPDPE was one of the prerequisites for agonist-mediated PLC-beta3 phosphorylation because the aminosteroid phospholipase C inhibitor U73122 could block the DPDPE effect. In addition to DPDPE, lysophosphatidic acid (LPA) stimulated the PLC-beta3 phosphorylation, but bradykinin did not. Furthermore, the LPA- and DPDPE-mediated PLC-beta3 phosphorylation was additive and was much less than that observed with phorbol-12-myristate-13-acetate. The effect of DPDPE was specific to PLC-beta3; the betagamma-insensitive phospholipase C-beta1 was not phosphorylated in the presence of either DPDPE or LPA. These results indicate that although PKC phosphorylation of PLC-beta3 is not obligatory for the opioid receptor desensitization, it seems to play a significant facilatory role in the mechanisms allowing desensitization of opioid-activated phospholipase C response before that of adenylyl cyclase inhibition.
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PMID:Contribution of phospholipase C-beta3 phosphorylation to the rapid attenuation of opioid-activated phosphoinositide response. 961 7

1. Prostanoid receptor-mediated sensitization, or excitation, of sensory nerve fibres contributes to the generation of hyperalgesia. To characterize the prostanoid receptors present on sensory neurones, biochemical assays were performed on primary cultures of adult rat dorsal root ganglia (DRG) and the F-11 (embryonic rat DRG x neuroblastoma hybrid) cell line. 2. In DRG cultures, the IP receptor agonists, cicaprost and carbaprostacyclin (cPGI2) stimulated cyclic AMP accumulation. Prostaglandin E2 (PGE2) also increased cyclic AMP levels, but to a lesser extent, while carbocyclic thromboxane A2 (cTxA2), PGD2 and PGF2alpha had negligible effects. The rank order of agonist potency was cicaprost>PGE2=BMY45778=cPGI2=PGI2. In the F-11 cells, the rank order of agonist potency for the stimulation of cyclic AMP accumulation was: cicaprost>iloprost=cPGI2=PGI2=BMY45778>PGE2=cTXA2++ +. In DRG cultures, cicaprost induced significantly more accumulation of inositol phosphates than PGE2. 3. To examine the effects of prostanoids on C-fibre activity, extracellular recordings of d.c. potentials from the rat isolated vagus nerve were made with the 'grease-gap' technique. PGI2 (0.1 nM-10 microM) produced the largest depolarizations of the nerve. The rank order of agonist potency was: PGI2=cPGI2=PGE1>cTXA2>PGE2=PGD2=TXB2>PGF2alpha. 4. Prior depolarization of nerves with either forskolin (10 microM) or phorbol dibutyrate (1 microM) alone significantly reduced the response to PGI2 (10 microM), while simultaneous application of both forskolin and phorbol dibutyrate attenuated PGI2 responses almost completely. 5. Putative EP1 and/or TP receptor-selective antagonists had no effect on the responses to PGI2, cPGI2 or PGE2 in the three preparations studied. 6. Collectively, these data are consistent with a positive coupling of IP receptors to both adenylyl cyclase and phospholipase C in sensory neurones. These findings suggest that IP receptors play a major role in the sensitization of rat sensory neurones.
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PMID:Characterization of prostanoid receptor-evoked responses in rat sensory neurones. 964 76

Our studies with cultured cells have provided new insight into the particular role of GM1 in regulating excitatory opioid responses. GM1 is significantly elevated in chronic opioid-treated cells via Gs/adenylyl cyclase activation. Such GM1 elevation promotes coupling of opioid receptor with Gs, resulting in attenuation of inhibitory opioid effects and induction of a sustained excitatory response. Application of exogenous GM1, but not other gangliosides, induces excitatory opioid responses not only in neurons and neuroblastoma cells that bear intrinsic opioid receptors but also in nonneuronal cells that are transfected with delta-opioid receptor. The latter system provides evidence that allosteric binding of GM1 changes receptor conformation from a Gi-coupled to a Gs-coupled mode. This is supported by preliminary experiments with a mutated delta-opioid receptor.
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PMID:The role of GM1 ganglioside in regulating excitatory opioid effects. 966 47

On the cellular level, opioid dependence is characterized by a significant elevation of adenylyl cyclase (AC) activity after drug withdrawal, a regulatory phenomenon termed "AC supersensitivity" or "cAMP overshoot." The present study examines the role of the stimulatory G protein (Gs) in the expression of naloxone precipitated opioid withdrawal in chronically morphine (10 microM; 3 days) treated neuroblastoma X glioma (NG108-15) hybrid cells. Determination of high-affinity [3H]forskolin binding to intact cells, which provides a direct parameter for the binding of the activated alpha-subunit of Gs (Gsalpha) to AC, revealed that the enhancement of AC activity after opioid withdrawal is not caused by an increased stimulation of effector activity by Gsalpha. Although not a direct function of Gs, the expression of AC supersensitivity required Gsalpha-mediated stimulation of AC, because 1) the enhancement of AC activity after opioid withdrawal was observed only in the presence of low, but not of high concentrations of forskolin, and 2) chemical inactivation of Gsalpha by low pH pretreatment abolished the induction of AC supersensitivity. Moreover, the regulatory mechanism underlying AC supersensitivity not only required the presence of activated Gsalpha per se, but functional intact stimulatory signal transduction pathways. Indeed, blockade of prostaglandin E1 receptor/Gs interaction in situ with a site-specific anti-Gsalpha antibody, as well as uncoupling of prostaglandin E1 receptor signaling by cholera toxin-catalyzed ADP-ribosylation of Gsalpha, prevented the expression of AC supersensitivity in membranes from opioid-withdrawn cells. These results suggest that the enhancement of AC activity in opioid-dependent cells, triggered by drug withdrawal, is not a direct Gsalpha effect, but involves a secondary regulatory event that requires costimulation of AC by acutely receptor-activated Gsalpha.
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PMID:Adenylyl cyclase supersensitivity in opioid-withdrawn NG108-15 hybrid cells requires Gs but is not mediated by the Gsalpha subunit. 969 42

Increasing evidence supports a role for adaptations in the cAMP pathway in mediating aspects of neural plasticity. These adaptations include altered levels of the catalytic (C) and regulatory (R) subunits of cAMP-dependent protein kinase (PKA) in specific neuronal cell types. In an effort to understand the mechanisms underlying this regulation of PKA, the effects of perturbing the cAMP pathway on PKA expression were examined in the locus ceruleus-like CATH.a cell line and the human neuroblastoma SH-SY5Y cell line. Exposure of CATH.a and SH-SY5Y cells to forskolin, a direct activator of adenylyl cyclase, resulted in a time-dependent decrease in levels of immunoreactivity of C and the two types of R (RI and RII). This decrease in PKA subunit immunoreactivity was not attenuated by pretreatment of the cells with the protein synthesis inhibitor cycloheximide. Moreover, exposure of the cell lines to forskolin had no effect on levels of mRNA for these PKA subunits over a wide time course. In contrast, treatment of cells with a cAMP antagonist (Rp-8-bromo-cAMPS) dramatically increased levels of PKA subunit immunoreactivity, particularly that of RI. No change in RI mRNA levels, however, was observed under these conditions. The PKA catalytic inhibitor H-89 did not attenuate the forskolin-induced down-regulation. The PKA subunit down-regulation was blocked, however, by treatment of the cells with Leu-Leu-Leu or lactacystin, inhibitors of proteasomes that are implicated in the regulated proteolysis of specific cellular proteins. Together, these findings demonstrate that regulation of PKA subunit expression by forskolin or a cAMP antagonist occurs primarily through post-transcriptional mechanisms and suggests the involvement of proteasome-mediated degradation in these phenomena.
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PMID:Regulation of cAMP-dependent protein kinase subunit expression in CATH.a and SH-SY5Y cells. 969 69


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