UMLS:C0027819 - FACTA Search

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Query: UMLS:C0027819 (neuroblastoma)
27,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Interferon-gamma (IFN-gamma) is a potent growth-inhibitory cytokine also endowed with differentiating activity on neural cells. Binding of IFN-gamma to its high-affinity receptor induces a rapid and transient activation of phospholipase A2 (PLA2). The mechanism coupling the IFN-gamma receptor (IFN-gamma-R) to PLA2 activation is not clearly defined, and no information is available on this mechanism in neuroblast cells. We have tested the hypothesis that GTP-binding proteins (G-proteins) may couple the IFN-gamma-R to PLA2 in the human neuroblastoma (NB) cell line LAN-5. Incubation of NB cells with IFN-gamma resulted in a rapid increase in [3H]arachidonic acid (AA) release, and this effect was blocked by pretreatment with anti-IFN-gamma antibodies. IFN-gamma-stimulated AA release was still observed in permeabilized cells that were blocked by pretreatment with anti-IFN-gamma-R antibodies. Exposure of permeabilized LAN-5 cells to guanosine 5'-[gamma-thio]triphosphate (GTP[S]), a non-hydrolysable GTP analogue, induced a dose-dependent release of [3H]AA. A non-specific nucleotide effect was excluded, since similar stimulatory effects on AA mobilization were not observed by GTP, ATP, CTP, ADP and GDP. IFN-gamma-stimulated AA release was completely blocked by the guanine nucleotide analogue that inhibits G-protein function, guanosine 5'-[beta-thio]diphosphate (GDP[S]). A role for G-proteins in IFN-gamma-R coupling to PLA2 was further supported by the inhibition of IFN-gamma-induced [3H]AA release by treatment of permeabilized cells with pertussis toxin and with the antiserum against the common alpha-subunits of G-proteins. To determine a possible contribution to AA mobilization by the phospholipase C and diacyglycerol lipase pathway or by protein kinase C activation, the effects of neomycin, a phospholipase C inhibitor, and PMA (phorbol 12-myristate 13-acetate), a direct activator of protein kinase C, were investigated. Neither neomycin nor PMA affected either basal or IFN-gamma-stimulated AA release. Ca2+ concentration, which has been shown to regulate the activity of some PLA2s, does not appear to play an important role in the regulation of the IFN-gamma-stimulated PLA2 activity, since incubating permeabilized cells in different concentrations of Ca2+ induced AA release without affecting the IFN-gamma response. Altogether, these findings suggest the existence of IFN-gamma-R, which couples a Ca(2+)-independent PLA2 activation via pertussis-toxin-sensitive G-proteins.
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PMID:Interferon-gamma-stimulated and GTP-binding-proteins-mediated phospholipase A2 activation in human neuroblasts. 839 12

The NF1 gene, which is altered in patients with type 1 neurofibromatosis, encodes neurofibromin, a protein whose GTPase-activating function can negatively regulate GTP-Ras by accelerating its conversion to inactive GDP-Ras. In schwannoma cell lines from patients with neurofibromatosis, loss of neurofibromin was previously shown to be associated with impaired regulation of GTP-Ras. Our analysis of other neural crest-derived tumor cell lines has shown that some melanoma and neuroblastoma cell lines established from tumors occurring in patients without neurofibromatosis contain reduced or undetectable levels of neurofibromin, with concomitant genetic abnormalities of the NF1 locus. In contrast to the schwannoma cell lines, GTP-Ras was appropriately regulated in the melanoma and neuroblastoma lines that were deficient in neurofibromin, even when c-H-ras was overexpressed in the lines. These results demonstrate that some neural crest tumors not associated with neurofibromatosis have acquired somatically inactivated NF1 genes and suggest a tumor-suppressor function for neurofibromin that is independent of Ras GTPase activation.
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PMID:Inactivation of the NF1 gene in human melanoma and neuroblastoma cell lines without impaired regulation of GTP.Ras. 851 98

The wasp venom, mastoparan (MP), is a direct activator of reconstituted pertussis toxin-sensitive G-proteins and of purified nucleoside diphosphate kinase (NDPK) [E.C. 2.6.4.6.]. In HL-60 membranes, MP activates high-affinity GTPase [E.C. 3.6.1.-] and NDPK-catalyzed GTP formation, but not photolabeling of G-protein alpha-subunits with GTP azidoanilide; this suggests that the venom activates G-proteins in this system indirectly via stimulation of NDPK. Moreover, the MP analogue, mastoparan 7 (MP 7), is a much more effective activator of reconstituted G-proteins than MP, whereas with regard to NDPK and GTPase in HL-60 membranes, the two peptides are similarly effective. In our present study, we investigated NDPK- and G-protein activation by MP in membranes of the human neuroblastoma cell line, SH-SY5Y, the human erythroleukemia cell line, HEL, the rat basophilic leukemia cell line, RBL 2H3, and the hamster ductus deferens smooth muscle cell line, DDT1MF-2. All these membranes exhibited high NDPK activities that were increased by MP. Compared to basal GTP formation rates, basal rates of high-affinity GTP hydrolysis in cell membranes were low. MP activated high-affinity GTP hydrolysis in cell membranes but did not enhance incorporation of GTP azidoanilide into G-protein alpha-subunits. As with HL-60 membranes, MP and MP 7 were similarly effective activators of NDPK and GTPase in SH-SY5Y membranes. Pertussis toxin inhibited MP-stimulated GTP hydrolyses in SH-SY5Y- and HEL membranes, whereas NDPK activations by MP were pertussis toxin-insensitive. Our data suggest that indirect G-protein activation via NDPK is not restricted to HL-60 membranes but is a more general mechanism of MP action in cell membranes. Pertussis toxin-catalyzed ADP-ribosylation of alpha-subunits may inhibit the transfer of GTP from NDPK to G-proteins. NDPK may play a much more important role in transmembrane signal transduction than was previously appreciated and, moreover, the GTPase of G-protein alpha-subunits may serve as GDP-synthase for NDPK.
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PMID:Activation of GTP formation and high-affinity GTP hydrolysis by mastoparan in various cell membranes. G-protein activation via nucleoside diphosphate kinase, a possible general mechanism of mastoparan action. 857 86

The regulation of phospholipase D was studied in human neuroblastoma cells using phosphatidylethanol as a marker of the enzyme activity. Carbachol induced phospholipase D activity in SH-SY5Y cells. Muscarinic antagonists inhibited the response with potencies suggesting that muscarinic M1 receptors are responsible for the activation. In permeabilized SH-SY5Y cells, both the carbachol- and GTP gamma S-induced Peth formation was inhibited by GDP beta S, indicating that both responses are mediated via a G-protein. The protein kinase C inhibitors, bisindolylmaleimide and staurosporine significantly inhibited the carbachol-induced Peth formation whereas H7 had no effect. Thus, the cholinergic activation of phospholipase D in SH-SY5Y cells is probably mediated via a direct receptor-G-protein coupling but an involvement of protein kinase C cannot be excluded. Calmidazolium, a calmodulin antagonist, induced an increase in phosphatidylethanol formation in both SH-SY5Y and IMR-32 cells. This effect was inhibited by genistein and tyrphostin, indicating a tyrosine kinase dependent pathway for phospholipase D activation in neuroblastoma cells.
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PMID:Regulation of phospholipase D activity in neuroblastoma cells. 890 67

Purified bovine brain G-protein was used in a solution phase assay to identify membrane-associated proteins that influenced the activation of heterotrimeric G-proteins. Detergent-solubilized membrane extracts from the neuroblastoma-glioma cell hybrid NG108-15, but not the parent C6B4 glioma cell line, increased [35S]GTPgammaS binding to purified G-protein by approximately 460%. The G-protein activator was heat-sensitive, and the magnitude of its action was related to the amount of extract protein. The biophysical and biochemical properties of the G-protein activator were determined using DEAE ion exchange chromatography, gel filtration, and a lectin affinity matrix. In the presence of added GDP (1 microM), the enriched G-protein activator increased the initial rate of [35S]GTPgammaS binding to brain G-protein by up to 4-fold. In the absence of added GDP, the G-protein activator elicited an initial burst in [35S]GTPgammaS binding to brain G-protein within the first 30 s, after which the rate of nucleotide binding to G-protein was similar in the absence or presence of the G-protein activator. The stimulation of nucleotide binding to brain G-protein by the activator was also observed after resolution of Galpha from Gbetagamma. The G-protein activator was distinct from other proteins (neuromodulin, tubulin, and beta-amyloid precursor protein) that influence nucleotide binding to G-protein, indicating the existence of a novel signal accelerator.
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PMID:Characterization of a G-protein activator in the neuroblastoma-glioma cell hybrid NG108-15. 893 52

The ability of the delta opioid agonist DPDPE ([D-Pen2, D-Pen4]enkephalin) to stimulate binding of the GTP analog guanosine-5'-O-(3-[35S]thio)triphosphate ([35S]GTPgammaS) to pertussis toxin-sensitive G proteins has been characterized in membranes from NG108-15 mouse neuroblastoma X rat glioma cells. The presence of GDP, or its hydrolysis-resistant analog GDPbetaS, and Mg++ ions was essential to observe agonist-mediated stimulation of [35S]GTPgammaS binding, although the guanine dinucleotides alone had complex inhibitory and stimulatory effects on [35S]GTPgammaS binding. The relative ability of the delta antagonists benzylidenenaltrexone and naltriben to inhibit DPDPE-stimulated [35S]GTPgammaS binding suggested the opioid receptor involved was of the delta-2 subtype. Ligand binding assays demonstrated biphasic binding of these antagonists to this single receptor type. [35S]GTPgammaS binding was also stimulated by [D-Ser2,Leu5,Thr6]enkephalin > deltorphin II = DPDPE = etorphine > levallorphan = diprenorphine = nalorphine = naltrindole. The delta antagonists benzylidenenaltrexone, TIPP (Tyr-Tic-Phe-Phe) and naltriben had no effect, but ICI 174864 (N, N-diallyl-Tyr-Aib-Phe-Leu-OH) acted as an inverse agonist and inhibited [35S]GTPgammaS binding. Pertussis toxin pretreatment blocked agonist stimulation of [35S]GTPgammaS binding and also reduced basal binding, thus confirming the presence of constitutively active delta receptors. Replacement of Na+ in the assay buffer with K+ afforded an increased level of basal [35S]GTPgammaS binding and an apparent increase in both the inverse agonist activity of ICI 174864 and the agonist activity of the partial agonist diprenorphine relative to the full agonist [D-Ser2, Leu5,Thr6]enkephalin. The stimulation of [35S]GTPgammaS binding to NG108-15 cell membranes allows a functional measure of delta opioid activity that can provide systems of differing relative efficacy.
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PMID:Delta opioid modulation of the binding of guanosine-5'-O-(3-[35S]thio)triphosphate to NG108-15 cell membranes: characterization of agonist and inverse agonist effects. 940 3

ADP-ribosylation factors (ARFs) are highly conserved approximately 20-kDa guanine nucleotide-binding proteins that participate in both exocytic and endocytic vesicular transport pathways via mechanisms that are only partially understood. Although several ARF-like proteins (ARLs) are known, their biological functions remain unclear. To characterize its molecular properties, we cloned mouse and human ARL4 (mARL4 and hARL4) cDNA. The appearance of mouse ARL4 mRNA during embryonic development coincided temporally with the sequential formation of somites and the establishment of brain compartmentation. Using ARL4-specific antibody for immunofluorescence microscopy, we observed that endogenous mARL4 in cultured Sertoli and neuroblastoma cells was mainly concentrated in nuclei. When expressed in COS7 cells, ARL4-T34N mutant, predicted to exist with GDP bound, was concentrated in nucleoli. Yeast two-hybrid screening and in vitro protein-interaction assays showed that hARL4 interacted with importin-alpha through its C-terminal NLS region and that the interaction was not nucleotide-dependent. Like ARL2 and -3, recombinant hARL4 did not enhance cholera toxin-catalyzed auto-ADP-ribosylation. Its binding of guanosine 5'-O-(thiotriphosphate) was modified by phospholipid and detergent, and the N terminus of hARL4, like that of ARF, was myristoylated. Our findings suggest that ARL4, with its distinctive nuclear/nucleolar localization and pattern of developmental expression, may play a unique role(s) in neurogenesis and somitogenesis during embryonic development and in the early stages of spermatogenesis in adults.
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PMID:ARL4, an ARF-like protein that is developmentally regulated and localized to nuclei and nucleoli. 1098 Jan 93

A ligand-independent activator of heterotrimeric brain G-protein was partially purified from detergent-solubilized extracts of the neuroblastoma-glioma cell hybrid NG108-15. The G-protein activator (NG108-15 G-protein activator (NG-GPA)) increased [(35)S]guanosine 5'-O-(thiotriphosphate) ([(35)S]GTPgammaS) to purified brain G-protein in a magnesium-dependent manner and promoted GDP dissociation from Galpha(o). The NG-GPA also increased GTPgammaS binding to purified, recombinant Galpha(i2), Galpha(i3), and Galpha(o), but minimally altered nucleotide binding to purified transducin. The NG-GPA increased GTPgammaS binding to membrane-bound G-proteins and inhibited basal, forskolin- and hormone-stimulated adenylyl cyclase activity in DDT(1)-MF-2 cell membranes. In contrast to G-protein coupled receptor-mediated activation of heterotrimeric G-proteins in DDT(1)-MF-2 cell membrane preparations, the action of the NG-GPA was not altered by treatment of the cells with pertussis toxin. ADP-ribosylation of purified brain G-protein also failed to alter the increase in GTPgammaS binding elicited by the NG-GPA. Thus, the NG-GPA acts in a manner distinct from that of a G-protein coupled receptor and other recently described receptor-independent activators of G-protein signaling. These data indicate the presence of unexpected regulatory domains on G(i)/G(o) proteins and suggest the existence of pertussis toxin-insensitive modes of signal input to G(i)/G(o) signaling systems.
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PMID:Pertussis toxin-insensitive activation of the heterotrimeric G-proteins Gi/Go by the NG108-15 G-protein activator. 1242 23

Agonist stimulation causes tubulin association with the plasma membrane and activation of PLC beta 1 through direct interaction with, and transactivation of, G alpha q. Here we demonstrate that G beta gamma interaction with tubulin down-regulates this signaling pathway. Purified G beta gamma, alone or with phosphatidylinositol 4,5-bisphosphate (PIP2), inhibited carbachol-evoked membrane recruitment of tubulin and G alpha q transactivation by tubulin. Polymerization of microtubules elicited by G beta gamma overrode tubulin translocation to the membrane in response to carbachol stimulation. G beta gamma sequestration of tubulin reduced the inhibition of PLC beta 1 observed at high tubulin concentration. G beta 1 gamma 2 interacted preferentially with tubulin-GDP, whereas G alpha q was transactivated by tubulin-GTP. Prenylation of the gamma 2 polypeptide was required for G beta gamma/tubulin interaction. Both confocal microscopy and coimmunoprecipitation studies revealed the spatiotemporal pattern of G beta gamma/tubulin interaction during carbachol stimulation of neuroblastoma SK-N-SH cells. In resting cells G beta gamma localized predominantly at the cell membrane, whereas tubulin was found in well defined microtubules in the cytosol. Within 2 min of agonist exposure, a subset of tubulin translocated to the plasma membrane and colocalized with G beta. Fifteen min post-carbachol addition, tubulin and G beta colocalized in vesicle-like structures in the cytosol. G beta/tubulin colocalization increased after pretreatment of cells with the microtubule-depolymerizing agent, colchicine, and was inhibited by taxol. Taxol also inhibited carbachol-induced PIP2 hydrolysis. It is suggested that G beta gamma/tubulin interaction mediates internalization of membrane-associated tubulin at the offset of PLC beta 1 signaling. Newly cytosolic G beta gamma/tubulin complexes might promote microtubule polymerization attenuating further tubulin association with the plasma membrane. Thus G protein-coupled receptors might evoke G alpha and G beta gamma to orchestrate regulation of phospholipase signaling by tubulin dimers and control of cell shape by microtubules.
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PMID:G beta gamma mediates the interplay between tubulin dimers and microtubules in the modulation of Gq signaling. 1280 15

Receptors as well as some G protein subunits internalize after agonist stimulation. It is not clear whether Galpha(q) or Gbetagamma undergo such regulated translocation. Recent studies demonstrate that m3 muscarinic receptor activation in SK-N-SH neuroblastoma cells causes recruitment of tubulin to the plasma membrane. This subsequently transactivates Galpha(q) and activates phospholipase Cbeta1. Interaction of tubulin-GDP with Gbetagamma at the offset of phospholipase Cbeta1 signaling appears involved in translocation of tubulin and Gbetagamma to vesicle-like structures in the cytosol (Popova, J. S., and Rasenick, M. M. (2003) J. Biol. Chem. 278, 34299-34308). The relationship of this internalization to the clathrin-mediated endocytosis of the activated m3 muscarinic receptors or Galpha(q) involvement in this process has not been clarified. To test this, SK-N-SH cells were treated with carbachol, and localization of Galpha(q), Gbetagamma, tubulin, clathrin, and m3 receptors were analyzed by both cellular imaging and biochemical techniques. Upon agonist stimulation both tubulin and clathrin translocated to the plasma membrane and co-localized with receptors, Galpha(q) and Gbetagamma. Fifteen minutes later receptors, Gbetagamma and tubulin, but not Galpha(q), internalized with the clathrin-coated vesicles. Coimmunoprecipitation of m3 receptors with Gbetagamma, tubulin, and clathrin from the cytosol of carbachol-treated cells was readily observed. These data suggested that Gbetagamma subunits might organize the formation of a multiprotein complex linking m3 receptors to tubulin since they interacted with both proteins. Such protein assemblies might explain the dynamin-dependent but beta-arrestin-independent endocytosis of m3 muscarinic receptors since tubulin interaction with dynamin might guide or insert the complex into clathrin-coated pits. This novel mechanism of internalization might prove important for other beta-arrestin-independent endocytic pathways. It also suggests cross-regulation between G protein-mediated signaling and the dynamics of the microtubule cytoskeleton.
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PMID:Clathrin-mediated endocytosis of m3 muscarinic receptors. Roles for Gbetagamma and tubulin. 1511 40

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