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)

Calmodulin-dependent phosphoprotein phosphatase (CaMDP) activity has been found in each of three cultured cell lines: rat pheochromocytoma (PC12), glioma (C6), and pituitary adenoma (GH3) cells. These CaMDP activities bind to immobilized calmodulin in the presence of Ca2+ and are eluted by EGTA. Sucrose density centrifugation revealed that the phosphatase activities exhibited sedimentation coefficients of 4.37, 4.23, and 4.59 for proteins derived from C6, GH3, and PC12 cells, respectively. The Stokes radii measured for the PC12 and C6 activities were 41.8 and 40.0 A, respectively. The estimated molecular weights calculated for the enzymes from these data are 79,100 and 72,200. The phosphatase activities required the presence of divalent cations such as Ca2+ or Mn2+ for expression of activity, which was optimal only in the presence of calmodulin. The apparent Km for phosphorylated myelin basic protein substrate was 8 microM. Affinity-purified antibodies to the B subunit of bovine brain CaMDP were found by immunoblot (Western blot) to cross-react with a single protein among proteins extracted from PC12, C6, and GH3 cells that had been resolved by two-dimensional electrophoresis. In each case, the cross-reacting protein exhibited an Mr of 16,000 and an isoelectric point of 4.7, values virtually identical to those reported previously for the B subunit of bovine brain CaMDP (sometimes called calcineurin). This cross-reacting protein was found among cellular proteins eluted from immobilized calmodulin by EGTA. Immunocytochemical localization of the cross-reacting protein in undifferentiated PC12 cells or in cells differentiated in response to nerve growth factor revealed its presence diffusely throughout the cytoplasm. These experiments support the contention that each of these cell lines contains a calmodulin-regulated phosphatase homologous physically and kinetically, and immunologically related to bovine brain CaMDP.
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PMID:Calmodulin-dependent phosphatases of PC12, GH3, and C6 cells: physical, kinetic, and immunochemical properties. 329 45

Ionomycin stimulated membrane-associated protein kinase Cs (PKCs) activity in C6 rat glioma cells as much as the potent PKCs stimulator 12-O-tetradecanoyl phorbol 13-acetate (TPA). However, while TPA, as expected, powerfully stimulated the phosphorylation of the PKCs' 85-kDa myristoylated alanine-rich protein kinase C substrate (MARCKS) protein, ionomycin unexpectedly did not. Instead, ionomycin reduced the basal MARCKS phosphorylation. Pretreating the glioma cells with ionomycin prevented TPA-stimulated PKCs from phosphorylating the MARCKS protein. The stimulation of membrane PKCs activity and the prevention of MARCKS phosphorylation by ionomycin required external Ca2+ because they were both abolished by adding 5 mM EGTA to the culture medium. Recently (Chakravarthy, B. R., Isaacs, R. J., Morley, P., Durkin, J. P., and Whitfield, J. F. (1995) J. Biol. Chem. 270, 1362-1368), we proposed that Ca2+ x calmodulin complexes block MARCKS phosphorylation by the activated PKCs in keratinocytes stimulated by raising the external Ca2+ concentration. In the present experiments calmodulin prevented MARCKS phosphorylation by TPA-stimulated PKCs in glioma cell lysates, and this blockade was lifted by a calmodulin antagonist, the calmodulin-binding domain peptide. But, physiologically more significant, pretreating intact glioma cells with a cell-permeable calmodulin antagonist, calmidazolium, prevented ionomycin from blocking MARCKS phosphorylation by PKCs in unstimulated and TPA-stimulated cells. The effect of ionomycin on MARCKS phosphorylation was not due to the stimulation of Ca2+ x calmodulin-dependent phosphoprotein phosphatase, calcineurin, because cyclosporin A, a potent inhibitor of this phosphatase, did not stop ionomycin from preventing MARCKS phosphorylation. The ability of ionomycin to prevent TPA-stimulated PKCs from phosphorylating MARCKS depended on whether ionomycin was added before, with, or after TPA. Maximum blockade occurred when ionomycin was added before TPA but was less effective when added with or after TPA. These results indicate that Ca2+ x calmodulin can profoundly affect PKCs' signaling at the substrate level.
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PMID:Ca2+ x calmodulin prevents myristoylated alanine-rich kinase C substrate protein phosphorylation by protein kinase Cs in C6 rat glioma cells. 755 16

Cyclosporin A (CsA) exerts its immunosuppressive effect by inhibiting the activity of nuclear factor of activated T cells (NFAT), thus preventing transcriptional induction of several cytokine genes. This effect is mediated through inactivation of the phosphatase calcineurin, which inhibits translocation of an NFAT component to the nucleus. We have previously reported that CsA inhibits the growth of rat C6 glioma cells in a dose-dependent manner and induces apoptotic cell death. Here, we report that NFAT DNA-binding activity is present in the nuclear extracts from C6 glioma cells and that CsA treatment inhibits the formation of a functional NFAT complex. We provide evidence for the presence of a group of NFATc proteins in proliferating glioma cells. Immunoblot analyses show that stimulation of C6 glioma cells with a calcium-inducing agent, ionomycin, alters NFATc migration on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This alteration is inhibited by simultaneous treatment with CsA, suggesting a calcineurin involvement in the regulation of glioma NFATc proteins. Direct immunofluorescence reveals the presence of NFATc proteins in nuclei of proliferating glioma cells and their disappearance in CsA-treated cells. These data point to a new mechanism of transcription regulation in glioma cells and provide an explanation for the observed sensitivity of glioma cells to CsA.
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PMID:Nuclear factor of activated T cells (NFAT) as a new component of the signal transduction pathway in glioma cells. 964 59

The effects of immunosuppressant cyclosporin A (CsA) on nitric oxide (NO) production and inducible NO synthase (iNOS) mRNA expression in rat C6 glioma cell line were investigated. CsA applied simultaneously with iNOS activator IFN-gamma caused dose-dependent reduction of NO synthesis in confluent C6 cells, as determined by measuring accumulation of nitrite, an indicator of NO production, in 48 h culture supernatants. IFN-gamma-induced expression of iNOS, but not interferon regulatory factor-1 (IRF-1) mRNA was reduced in CsA-treated cells. The enzymatic activity of iNOS was not changed by CsA, since it failed to affect NO production in cells in which iNOS had already been induced with IFN-gamma and any further induction was blocked by protein synthesis inhibitor cycloheximide (CHX). FK506 was not able to mimic inhibitory effect of CsA on NO production in C6 cells, suggesting calcineurin-independent mechanism of CsA action.
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PMID:Cyclosporin A inhibits activation of inducible nitric oxide synthase in C6 glioma cell line. 987 97

Calcineurin, a ubiquitous calcium-activated serine phosphatase, plays an important role in the signal transduction. We have previously reported that cyclosporin A (CsA) inhibits the growth and survival of the rat C6 glioma cells due to the inhibition of signaling pathway involving calcineurin and transcription factor nuclear factor of activated T cells (NFAT). In the present study, we show that CsA affects the survival of reactive astrocyte cultures derived from striatal trauma. Exposure of reactive astrocytes to doses of CsA >50 microg/ml for 24--72 h produces morphological changes, including cell body shrinkage and loss of extensions, followed by cell death. This death was accompanied by apoptotic changes in nuclear morphology and DNA fragmentation, as revealed by Hoechst 33258 and positive TUNEL staining. We demonstrated the presence of calcineurin A subunit in reactive astrocytes and corpus callosum (brain structure enriched in astrocytes) and an additional calcineurin-like protein occurring solely in reactive astrocytes. FK506, a calcineurin inhibitor unrelated to CsA, inhibits proliferation of astrocytes and induces death accompanied by apoptotic changes in nuclear morphology and DNA fragmentation. Since calcineurin is a major target for both CsA and FK506, the results suggest that this phosphatase is involved in the regulation of reactive astrocyte survival.
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PMID:Cyclosporin A-sensitive signaling pathway involving calcineurin regulates survival of reactive astrocytes. 1122 21

Muscarinic acetylcholine receptors in NG108-15 neuroblastoma x glioma cells, and beta-adrenergic or angiotensin II receptors in cortical astrocytes and/or ventricular myocytes, utilize the direct signaling pathway to ADP-ribosyl cyclase within cell membranes to produce cyclic ADP-ribose (cADPR) from beta-NAD+. This signal cascade is analogous to the previously established transduction pathways from bradykinin receptors to phospholipase Cbeta and beta-adrenoceptors to adenylyl cyclase via G proteins. Upon receptor stimulation, the newly-formed cADPR may coordinately function to upregulate the release of Ca2+ from the type II ryanodine receptors as well as to facilitate Ca2+ influx through voltage-dependent Ca2+ channels. cADPR interacts with FK506, an immunosuppressant, at FKBP12.6, FK506-binding-protein, and calcineurin, or ryanodine receptors. cADPR also functions through activating calcineurin released from A-kinase anchoring protein (AKAP79). Thus, some G(q/11)-coupled receptors can control cADPR-dependent modulation in Ca2+ signaling.
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PMID:Signal transduction from bradykinin, angiotensin, adrenergic and muscarinic receptors to effector enzymes, including ADP-ribosyl cyclase. 1125 66

Interleukin (IL)-8 produced from glioblastoma is suggested to contribute to its own proliferation and progression. Since various external stimuli have been shown to increase intracellular Ca(2+) in glioma cells, we investigated Ca(2+) mobilization-dependent IL-8 expression and effect of cyclosporin A (CsA), an inhibitor of calcineurin (Cn), on the expression and invasive potential of human glioblastoma U251MG cells. Combined treatment with Ca(2+)-ionophore and phorbol-myristate-acetate (A23187/PMA) increased IL-8 mRNA and protein levels. This increase was suppressed by CsA and by another Cn inhibitor FK506. Luciferase reporter gene assay and electrophoretic mobility shift assay revealed that activation of p65-containing nuclear factor-kappaB was essential for A23187/PMA-dependent activation of IL-8 promoter. CsA suppressed the promoter activity by attenuating IkappaB-alpha degradation. U251MG cells expressed IL-8 receptors CXCR-1 and -2, and Matrigel invasion assay revealed that CsA attenuated A23187/PMA-dependent stimulation of invasive potential, probably by inhibiting IL-8 production. In addition, IL-8-dependent proliferation was also suppressed by CsA. Taken together, these results demonstrate the novel inhibitory effects of CsA on glioblastoma cell functions, suggesting CsA as a potential therapeutic adjuvant for glioma treatment.
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PMID:Inhibitory effects of cyclosporin A on calcium mobilization-dependent interleukin-8 expression and invasive potential of human glioblastoma U251MG cells. 1528 17

Renal transplantation is method of choice for treatment of patients with end-stage renal disease without contraindications for immunosuppressive therapy. Neurological complications occur frequently in renal transplant recipients. They may be the consequence of immunosuppressive treatment, but more often evolve as the consequence of previous disturbances which developed during the state of uraemia and treatment with dialysis. The most pronounced neurotoxic effect has calcineurin inhibitors tacrolimus and cyclosporine. The spectrum of neurological disturbances caused by calcineurin inhibitors range from very mild symptoms as paraesthesiae, tremor, headache or flushing, to severe changes that may cause lethal outcome. Peripheral neuropathies in renal transplant recipients may occur in the form of mononeuropathy or polyneuropathy. Cerebrovascular diseases are consequence of changes on blood vessels caused by uraemia, dialysis and side effects of immunosuppressive drugs. They cause death in 8% of renal transplant recipients. Central nervous system (CNS) infections usually occur during the first posttransplant year. Unclear symptomatology frequently postpones the diagnosis. Diagnostic evaluation should include magnetic resonance imaging for localization of the process, as well as lumbal puncture in cases without contraindications for the procedure, in order to determine the causative agent. Regarding the ominous prognosis of CNS infections in the immunocompromised host, only timely diagnosis may improve survival. The most common causative agents are Cryptococcus neoformans, Listeria monocytogenes and Aspergillus funigatus. Viral infections also occur, and are commonly caused by herpes virideae, varicella-zoster virus and papova virus. CNS infections clinically present as meningitis, progressive dementia or focal neurological defect. The most common primary brain tumors are B-cell lymphomas, but glioblastoma, hemangioblastoma, leiomyosarcoma or glioma may also occur. In cases of neurological posttransplant complications, optimal treatment should be guided by neurologist, nephrologist and infectologist, in some cases also by neurosurgeons.
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PMID:[Neurological complications in renal transplant recipients]. 1857 36

Glioblastoma multiforme (GBM) is the most frequent and incurable type of brain tumor of adults. Hypoxia has been shown to direct GBM toward a more aggressive and malignant state. Here we show that hypoxia increases Notch1 activation, which in turn induces the expression of transient receptor potential 6 (TRPC6) in primary samples and cell lines derived from GBM. TRPC6 is required for the development of the aggressive phenotype because knockdown of TRPC6 expression inhibits glioma growth, invasion, and angiogenesis. Functionally, TRPC6 causes a sustained elevation of intracellular calcium that is coupled to the activation of the calcineurin-nuclear factor of activated T-cell (NFAT) pathway. Pharmacologic inhibition of the calcineurin-NFAT pathway substantially reduces the development of the malignant GBM phenotypes under hypoxia. Clinically, expression of TRPC6 was elevated in GBM specimens in comparison with normal tissues. Collectively, our studies indicate that TRPC6 is a key mediator of tumor growth of GBM in vitro and in vivo and that TRPC6 may be a promising therapeutic target in the treatment of human GBM.
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PMID:Receptor channel TRPC6 is a key mediator of Notch-driven glioblastoma growth and invasiveness. 2002 70

Glioma growth and progression depend on a specialized subpopulation of tumour cells, termed tumour stem cells. Thus, tumour stem cells represent a critical therapeutic target, but the molecular mechanisms that regulate them are poorly understood. Hypoxia plays a key role in tumour progression and in this study we provide evidence that the hypoxic tumour microenvironment also controls tumour stem cells. We define a detailed molecular signature of tumour stem cell genes, which are overexpressed by tumour cells in vascular and perinecrotic/hypoxic niches. Mechanistically, we show that hypoxia plays a key role in the regulation of the tumour stem cell phenotype through hypoxia-inducible factor 2alpha and subsequent induction of specific tumour stem cell signature genes, including mastermind-like protein 3 (Notch pathway), nuclear factor of activated T cells 2 (calcineurin pathway) and aspartate beta-hydroxylase domain-containing protein 2. Notably, a number of these genes belong to pathways regulating the stem cell phenotype. Consistently, tumour stem cell signature genes are overexpressed in newly formed gliomas and are associated with worse clinical prognosis. We propose that tumour stem cells are maintained within a hypoxic niche, providing a functional link between the well-established role of hypoxia in stem cell and tumour biology. The identification of molecular regulators of tumour stem cells in the hypoxic niche points to specific signalling mechanisms that may be used to target the glioblastoma stem cell population.
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PMID:A hypoxic niche regulates glioblastoma stem cells through hypoxia inducible factor 2 alpha. 2037 33


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