Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0017638 (glioma)
 30,880 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In membranes of neuroblastoma x glioma hybrid (NG108-15) cells, bradykinin (EC50 approximately equal to 5 nM) stimulates GTP hydrolysis by a high-affinity GTPase (Km approximately equal to 0.2 microM). The octapeptide, des-Arg9-bradykinin, was inactive. Stimulation of GTP hydrolysis by bradykinin and an opioid agonist was partially additive. Treatment of NG108-15 cells with pertussis toxin, which inactivates Ni, eliminated GTPase stimulation by the opioid agonist but not by bradykinin. The data suggest that bradykinin activates in NG108-15 membranes a guanine nucleotide-binding protein which is not sensitive to pertussis toxin and which may be involved in bradykinin-induced stimulation of phosphoinositide metabolism in these cells.
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PMID:Bradykinin stimulates GTP hydrolysis in NG108-15 membranes by a high-affinity, pertussis toxin-insensitive GTPase. 300 34

Stimulation of basal adenylate cyclase activity in membranes of neuroblastoma x glioma hybrid cells by prostaglandin E1 (PGE1) is half-maximal and maximal (about 8-fold) at 0.1 and 10 microM respectively. This hormonal effect requires GTP, being maximally effective at 10 microM. However, at the same concentrations that stimulate adenylate cyclase in the presence of GTP, PGE1 inhibited basal adenylate cyclase activity when studied in the absence of GTP, by maximally 60%. A similar dual action of PGE1 was observed with the forskolin-stimulated adenylate cyclase, although the potency of PGE1 in both stimulating and inhibiting adenylate cyclase was increased and the extent of stimulation and inhibition of the enzyme by PGE1 was decreased by the presence of forskolin. The inhibition of forskolin-stimulated adenylate cyclase by PGE1 occurred without apparent lag phase and was reversed by GTP and its analogue guanosine 5'-[gamma-thio]triphosphate at low concentrations. Treatment of neuroblastoma x glioma hybrid cells or membranes with agents known to eliminate the function of the inhibitory GTP-binding protein were without effect on PGE1-induced inhibition of adenylate cyclase. The data suggest that stimulatory hormone agonist, apparently by activating one receptor type, can cause both stimulation and inhibition of adenylate cyclase, and that the final result depends only on the activity state of the stimulatory GTP-binding protein, Gs. Possible mechanisms responsible for the observed adenylate cyclase inhibition by the stimulatory hormone PGE1 are discussed.
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PMID:Guanine nucleotide-independent inhibition of adenylate cyclase by a stimulatory hormone. 305 32

Rat glioma C6 BU1 cells contain a pertussis toxin substrate of 40 kDa which does not appear to be identical with Gi,Go or transducin. The GTP analogue, GTP[gamma S], inhibited the rate of pertussis toxin-catalysed ADPribosylation of this protein, while the GDP analogue GDP[beta S] stimulated this reaction. A protein of the same kDa value was ADPribosylated by cholera toxin in the absence of added guanine nucleotides. It is suggested that this 40 kDa protein can be a substrate for both cholera and pertussis toxins under appropriate conditions.
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PMID:Guanine nucleotide regulation of the pertussis and cholera toxin substrates of rat glioma C6 BU1 cells. 310 99

Incubation of membranes of neuroblastoma x glioma hybrid, NG108-15 cells with GDP beta S followed by immunoblotting of resolved membrane and supernatant fractions with specific anti-peptide antisera showed essentially all of the alpha subunit of Go to be associated with the membrane. Similar experiments with poorly hydrolyzed analogues of GTP caused release of a significant fraction (some 50% within 60 minutes) of Go alpha into the supernatant. This was not mimicked by analogues of ATP. Antisera directed against peptides corresponding to the extreme N and C-termini of GO alpha demonstrated that the released polypeptide was not proteolytically clipped. These experiments show that the alpha subunit of GO need not be invariably bound to the plasma membrane and that guanine nucleotide activation can release the alpha subunit of GO from its site of membrane attachment.
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PMID:GTP analogues cause release of the alpha subunit of the GTP binding protein, GO, from the plasma membrane of NG108-15 cells. 312 78

NG108-15 neuroblastoma x glioma hybrid cells express a major 45 kDa substrate for cholera toxin and a 40 kDa substrate(s) for pertussis toxin when ADP-ribosylation is performed in the presence of GTP. In the absence of exogenous GTP, however, cholera toxin was shown to catalyse incorporation of radioactivity into a 40 kDa protein as well as into the 45 kDa polypeptide. In membranes of cells which had been pretreated in vivo with pertussis toxin, the 40 kDa band was no longer a substrate for either pertussis or cholera toxin in vitro, whereas in membranes from cholera-toxin-pretreated cells the 40 kDa band was still a substrate for fresh cholera toxin in vitro and for pertussis toxin. In this cell line, opioid peptides have been shown to inhibit adenylate cyclase exclusively by interacting with Gi (inhibitory G-protein) and with no other pertussis-toxin-sensitive G-protein. Opioid agonists, but not antagonists, promoted the cholera-toxin-catalysed ADP-ribosylation of the 40 kDa polypeptide, hence demonstrating that this cholera-toxin substrate was indeed the alpha-subunit of Gi. These results demonstrate that Gi can be a substrate for either cholera or pertussis toxin under appropriate conditions.
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PMID:Opioid peptides promote cholera-toxin-catalysed ADP-ribosylation of the inhibitory guanine-nucleotide-binding protein (Gi) in membranes of neuroblastoma x glioma hybrid cells. 313 27

The major pertussis-toxin-sensitive guanine nucleotide-binding protein of rat glioma C6 BU1 cells corresponded immunologically to Gi2. Antibodies which recognize the alpha subunit of this protein indicated that it has an apparent molecular mass of 40 kDa and a pI of 5.7. Incubation of membranes of these cells with guanosine 5'-[beta gamma-imido]triphosphate, or other analogues of GTP, caused release of this polypeptide from the membrane in a time-dependent manner. Analogues of GDP or of ATP did not mimic this effect. The GTP analogues similarly caused release of the alpha subunit of Gi2 from membranes of C6 cells in which this G-protein had been inactivated by pretreatment with pertussis toxin. The beta subunit was not released from the membrane under any of these conditions, indicating that the release process was a specific response to the dissociation of the G-protein after binding of the GTP analogue. Similar nucleotide profiles for release of the alpha subunits of forms of Gi were noted for membranes of both the neuroblastoma x glioma hybrid cell line NG108-15 and of human platelets. These data provide evidence that: (1) pertussis-toxin-sensitive G-proteins, in native membranes, do indeed dissociate into alpha and beta gamma subunits upon activation; (2) the alpha subunit of 'Gi-like' proteins need not always remain in intimate association with the plasma membrane; and (3) the alpha subunit of Gi2 can still dissociate from the beta/gamma subunits after pertussis-toxin-catalysed ADP-ribosylation.
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PMID:GTP analogues promote release of the alpha subunit of the guanine nucleotide binding protein, Gi2, from membranes of rat glioma C6 BU1 cells. 314 Aug 1

Subcellular fractions of neuroblastoma x glioma (NG108-15) hybrid cells were used to study the mechanism of inositol 1,4,5-trisphosphate-induced calcium release. A microsomal fraction, enriched in endoplasmic reticulum and plasma membranes and almost devoid of mitochondria, was the most active in inositol trisphosphate- or GTP-dependent release of calcium. Neither GTP nor inositol 1,4,5-trisphosphate affected the calcium efflux mediated by the other reagent, suggesting that inositol trisphosphate and GTP act on different calcium-sequestrating vesicles. The stimulation of calcium release by GTP was relatively slow (t1/2 = 90 s), dependent on polyethyleneglycol, and greater at 2 X 10(-5) M calcium (5 nmol X min-1 X mg-1) than at 10(-6) M calcium (0.8 nmol X min-1 X mg-1). The inositol trisphosphate-induced calcium efflux was not mimicked by inositol monophosphate; it was fast (t1/2 less than 10 s) and unaffected by 3% polyethyleneglycol. The amount of calcium released by inositol trisphosphate was greatest at 10(-6) M external calcium (1 nmol X min-1 X mg-1) and it was undetectable at 2 X 10(-5) M calcium. A feedback inhibition of the inositol trisphosphate-induced calcium release by cytoplasmic calcium provides a safety mechanism preventing deleterious effects of abnormally high calcium levels.
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PMID:Calcium modulation of inositol 1,4,5-trisphosphate-induced calcium release from neuroblastoma x glioma hybrid (NG108-15) microsomes. 349 Oct 73

We have compared the regulation of adenylate cyclase activity in membrane fractions from C6 glioma cells and in monolayer cultures of C6 cells that had been permeabilized with saponin. Guanine nucleotides (GTP and GTP gamma S) and isoproterenol increase adenylate cyclase activity in C6 membranes and in permeabilized C6 cells. In C6 membranes, guanine nucleotides activate adenylate cyclase in the presence or absence of isoproterenol; in permeabilized cells, however, guanine nucleotides increase adenylate cyclase activity only in the presence of isoproterenol. We suggest that the properties of the permeabilized cells more closely resemble those of intact cells, and that some component which is present in permeabilized cells but is lost following cell disruption may be important for the normal regulation of adenylate cyclase activity.
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PMID:Guanine nucleotide activation of adenylate cyclase in saponin permeabilized glioma cells. 353 31

Immunocytochemistry is routinely used to examine the occurrence and distribution of cytoskeletal proteins in cells, but the results are usually evaluated visually and subjectively. Little use has been made of the potential the method offers for quantitative work. Here we report on application of cytofluorometry to quantify binding of antibodies to the cytoskeleton of U-251 MG human malignant glioma cells in culture. The results show that cytofluorometry is a simple and reliable procedure for: (a) determining the optimal concentrations of primary and secondary antibodies and other labeling reagents; (b) evaluating the binding specificity of commercial secondary antisera; and (c) evaluating the effect of different preparatory procedures on preservation of and binding of antibodies to cytoskeletal structures. Experiments with a monoclonal antibody to tubulin show that preservation of tubulin is very sensitive to the preparatory procedures used. Maximum labeling of tubulin in intact cells was obtained when the cells were pre-fixed with formaldehyde before permeabilization with solvent. Maximum labeling of tubulin in Triton-extracted cytoskeletons was achieved by pre-fixing the cells with the bifunctional protein crosslinking reagent dithiobis (succinimidyl propionate), extracting with Triton in a microtubule-stabilizing buffer, and post-fixing with formaldehyde. GTP was not required to preserve tubulin in cytoskeletons.
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PMID:Use of cytofluorometry to evaluate binding of antibodies to the cytoskeleton of cultured cells. 368 Sep 31

Inhibitory coupling of receptors to adenylate cyclase previously has been shown to be relatively sensitive to inactivation by alkylation with N-ethylmaleimide (NEM). Modification of the inhibitory guanine nucleotide regulatory protein, Ni, has been proposed to be responsible for this effect. The effects of NEM on GTP-sensitive binding of carbachol to muscarinic cholinergic receptors has been compared in a cell line (1321N1 human astrocytoma cells) in which these receptors stimulate phosphoinositide breakdown and in a cell line (NG108-15 neuroblastoma X glioma cells) in which activation of these receptors results in inhibition of adenylate cyclase. Pretreatment of membrane preparations from 1321N1 cells with NEM resulted in a concentration-dependent decrease in the extent of pertussis toxin-catalysed [32P]ADP-ribosylation of a 41 000 Da protein previously proposed to be the alpha subunit of Ni. Under conditions where 32P-labelling of Ni in 1321N1 membranes was reduced by NEM by 90%, no effect was observed on the extent of guanine nucleotide-sensitive high-affinity binding of carbachol to muscarinic cholinergic receptors. In contrast, treatment of NG108-15 membranes with NEM under the same conditions resulted in complete loss of high-affinity guanine nucleotide sensitive binding of carbachol. These results illustrate another difference between the muscarinic receptor population of these two cell lines, and support the previous proposal that muscarinic receptors of 1321N1 cells couple to a guanine nucleotide regulatory protein that is not Ni.
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PMID:Further evidence that muscarinic cholinergic receptors of 1321N1 astrocytoma cells couple to a guanine nucleotide regulatory protein that is not Ni. 392 72


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