Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Polycystic kidney disease (PKD) is a common genetic disease characterized by the proliferation of epithelial cells, formation of cysts, and the progression of renal deficiency. We have investigated a possible role of glycosphingolipids in the proliferation of human kidney cells in this disease. The levels of glucosylceramide and lactosylceramide and the activity of glucosylceramide synthase (GlcT-1) and lactosylceramide synthase (GalT-2) were elevated 2-fold and 3-fold, respectively, in the PKD tissue compared to control. Lactosylceramide, but not glucosylceramide (10 microM) derived from PKD exerted a 4-fold stimulation in the proliferation of these cells. However, at a concentration of 40 microM, lactosylceramide and glucosylceramide both stimulated cell proliferation on the order of 10-fold and 2.5-fold, respectively, as compared to control. This phenomenon may be due to the enrichment of lactosylceramide containing shorter chain fatty acids (C16:0-C18:0). Lactosylceramide, but not glucosylceramide exerted a time-dependent stimulation in the phosphorylation of mitogen-activated protein kinase (p44 MAPK) in normal human kidney proximal tubular cells. Moreover, the kidneys and cultured cells from the PKD patients contained higher levels of the p44 MAPK as compared to normal human kidneys. In sum, our studies indicate that lactosylceramide present in the PKD kidney may stimulate cell proliferation via activation of the p44 MAPK, and contribute to the pathophysiology in this disease.
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PMID:Role of lactosylceramide and MAP kinase in the proliferation of proximal tubular cells in human polycystic kidney disease. 880 68

Previous studies have shown that the ceramide analogue, D-threo-1-phenyl-2-decanoylamin-3-morpholino-propanol (D-PDMP), inhibits glucosylceramide synthase and thus leads to extensive depletion of glycosphingolipids derived from glucosyl ceramide. Our previous studies have shown that cholera toxin B subunit, which specifically binds to the cell surface ganglioside GM1, and GM1 itself can enhance the action of nerve growth factor (NGF) in responsive cells by enhancing the NGF-induced autophosphorylation of the high affinity NGF receptor, Trk. Using D-PDMP, we examined the effects of the inhibition of the biosynthesis of glycosphingolipids on intracellular NGF signaling pathway. D-PDMP was found to inhibit NGF-induced neurite outgrowth of PC12 cells. Moreover, D-PDMP clearly inhibited NGF-induced autophosphorylation of Trk and prevented the activation of phosphatidylinositol 3-kinase and mitogen-activated protein kinase, downstream targets of Trk-initiated intracellular protein kinase cascades. These effects of D-PDMP were abolished by the addition of GM1 but not by the addition of other ganglioside subspecies to the culture medium. Furthermore, the effect of D-PDMP seemed to be specific for the Trk receptor, because intracellular signaling pathway of epidermal growth factor was not affected by D-PDMP. Dimethylsphingosine and the cell-permeable analogue, C2-ceramide, did not show such a strong inhibitory effect on neurite outgrowth or on the autophosphorylation of Trk. The present results and our previous observations clearly demonstrate that Trk requires endogenous gangliosides, especially GM1, for its normal function in mediating the neurotrophic activity of NGF at least in PC12 cells.
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PMID:Glucosylceramide synthase inhibitor inhibits the action of nerve growth factor in PC12 cells. 974 78

To address the role of brain gangliosides in synaptic plasticity, the synthetic ceramide analog, 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) was used to manipulate the biosynthesis of gangliosides in cultured cortical neurons. Spontaneous synchronized oscillatory activity of intracellular Ca2+ between the neurons, which represents synapse formation, was suppressed by the depletion of endogenous gangliosides by D-threo-PDMP, an inhibitor of glucosylceramide synthase. The decreased functional synapse formation was normalized by supplementation of GQ1b but not by the other gangliosides, suggesting that de novo synthesis of ganglioside GQ1b is essential for the synaptic activity (Mizutani A. et al., Biochem. Biophys. Res. Commun. 222, 494-498, 1996). On the other hand, the enantiomer of the inhibitor, L-threo-PDMP, could elevate cellular levels of glycosphingolipids including gangliosides. This paper presents our recent findings on the neurotrophic actions of L-threo-PDMP in vitro and in vivo. We found that L-PDMP could up-regulate neurite outgrowth, functional synapse formation and ganglioside biosynthesis through activating GM3, GD3 and GQ1b synthases. Simultaneously, the activity of p42 mitogen-activated protein kinase was also facilitated by L-PDMP. To evaluate the efficacy of this drug on long term memory, rats were trained for 2 weeks using an 8-arm radial maze task, and then forebrain ischemia was induced by 4-vessel occlusion (for 10 min x 2 with a 60 min interval). Repeated treatment of L-threo-PDMP (40 mg/kg, i.p. for 6 days, twice a day) starting 24 h after the ischemia, improved the deficit of the well-learned spatial memory, demonstrating the potential therapeutic use of the ceramide analog for treatment of neurodegenerative disorders.
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PMID:L-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol stimulates ganglioside biosynthesis, neurite outgrowth and synapse formation in cultured cortical neurons, and ameliorates memory deficits in ischemic rats. 982 77

We first examined the involvement of the complex sphingolipids in cell-substratum adhesion using GM-95, a mutant cell line deficient in glycosphingolipids (GSLs) due to the lack of ceramide glucosyltransferase activity. We determined the adhesion of the mutant cells and stable transfectants expressing GSLs, which were established by transfection of GlcT-1 cDNA into GM-95 cells under neutral sphingomyelinase (sm) treatment. We confirmed that complex sphingolipids play critical roles in cell-substratum adhesion, and the presence of either GSLs or SM is sufficient for the adhesion. We also investigated intracellular signaling (glycosignaling) mediated by endogenous GM1a involved in the neuronal differentiation of PC12 cells using the cholera toxin B subunit (CTB) that specifically binds to ganglioside GM1a. Treatment with CTB induced neuron-like differentiation of PC12 cells. Biochemical analyses demonstrated that the tyrosine phosphorylation induced by CTB was responsible for neuron-like differentiation of PC12 cells and that the MEK-ERK cascade is a part of the biological signals mediated by endogenous ganglioside GM1a on PC12 cells. We further demonstrated that glycosignaling is mediated through a high-affinity ligand, PSGL-1, for P-selection on neutrophils. In this case, engagement of PSGL-1 on the cell surface strongly induced tyrosine phosphorylation of several cellular proteins including ERKs and activated a canonical MAP kinase pathway. Tyrosine phosphorylation induced by engagement of PSGL-1 is responsible for the secretion of interleukin-8 from neutrophils, suggesting that PSGL-1-mediated glycosignals are involved in the progression of the inflammatory response. In this review, we mainly discuss the biological and pathological significance of glycoconjugates in relation to the above issues.
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PMID:[Functional glycoconjugates involved in cellular interaction]. 1277 88

Antimicrobial peptides such as defensins are crucial for host defense at mucosal surfaces. We reported previously that Salmonella enteritidis flagellin (FliC) induced human beta-defensin-2 (hBD-2) mRNA expression in Caco-2 cells via NF-kappaB activation (Ogushi, K., Wada, A., Niidome, T., Mori, N., Oishi, K., Nagatake, T., Takahashi, A., Asakura, H., Makino, S., Hojo, H., Nakahara, Y., Ohsaki, M., Hatakeyama, T., Aoyagi, H., Kurazono, H., Moss, J., and Hirayama, T. (2001) J. Biol. Chem. 276, 30521-30526). In this study, we examined the role of ganglioside as co-receptors with Toll-like receptor 5 (TLR5) on FliC induction of hBD-2 expression in Caco-2 cells. Exogenous gangliosides suppressed FliC induction of hBD-2 promoter activity and binding of FliC to Caco-2 cells. Incorporation of exogenous ganglioside GD1a into Caco-2 cell membranes increased the effect of FliC on hBD-2 promoter activity. In support of a role for endogenous gangliosides, incubation of Caco-2 cells with dl-threo-2-hexadecanoylamino-3-morpholino-1-phenylpropanol, a glucosylceramide synthase inhibitor, reduced FliC induction of hBD-2 promoter activity. GD1a-loaded CHO-K1-expressing TLR5 cells had a higher potential for hBD-2 induction following FliC stimulation than GD1a-loaded CHO-K1 cells not expressing TLR5. FliC increased phosphorylation of mitogen-activated protein kinase, p38, and ERK1/2. Exogenous gangliosides GD1a, GD1b, and GT1b each suppressed FliC induction of p38 and ERK1/2 phosphorylation. Furthermore, FliC did not enhance luciferase activity in Caco-2 cells transfected with a plasmid containing a mutated activator protein 1-binding site. These results suggest that gangliosides act as co-receptors with TLR5 for FliC and promote hBD-2 expression via mitogen-activated protein kinase.
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PMID:Gangliosides act as co-receptors for Salmonella enteritidis FliC and promote FliC induction of human beta-defensin-2 expression in Caco-2 cells. 1470 35

In the present study a possible role of glycosphingolipids (GSLs) in inducible nitric oxide synthase (iNOS) gene expression and nitric oxide (NO) production after spinal cord injury (SCI) in rats has been established. In primary rat astrocytes lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) treatment increased the intracellular levels of lactosylceramide (LacCer) and induced iNOS gene expression. d-Threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol.HCI (PDMP), a glucosylceramide synthase and LacCer synthase (galactosyltransferase, GalT-2) inhibitor, inhibited LPS/IFN-gamma induced iNOS expression, which was reversed by exogenously supplied LacCer, but not by other glycosphingolipids. LPS/IFN-gamma caused a rapid increase in the activity of GalT-2 and synthesis of LacCer. Silencing of GalT-2 gene with the use of antisense oligonucleotides resulted in decreased LPS/IFN-gamma-induced iNOS, TNF-alpha, and IL-1beta gene expression. The PDMP-mediated reduction in LacCer production and inhibition of iNOS expression correlated with decreased Ras and ERK1/2 activation along with decreased IkappaB phosphorylation, NF-kappaB DNA binding activity, and NF-kappaB-luciferase reporter activity. LacCer-mediated Ras activation was redox-mediated and was attenuated by antioxidants N-acetyl cysteine (NAC) and pyrrolidine dithiocarbamate (PDTC). In vivo administration of PDMP after SCI resulted in improved functional outcome (Basso, Beattie, Bresnahan score); inhibition of iNOS, TNF-alpha, and IL-1beta expression; decreased neuronal apoptosis; and decreased tissue necrosis and demyelination. The in vivo studies supported the conclusions drawn from cell culture studies and provided evidence for the possible role of GalT-2 and LacCer in SCI-induced inflammation and pathology. To our knowledge this is the first report of a role of LacCer in iNOS expression and the advantage of GSL depletion in attenuating post-SCI inflammation to improve the outcome of SCI.
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PMID:A novel role of lactosylceramide in the regulation of lipopolysaccharide/interferon-gamma-mediated inducible nitric oxide synthase gene expression: implications for neuroinflammatory diseases. 1522 42

Interleukin 2 (IL-2) rescued human natural killer (NK) KHYG-1 cells from apoptosis along with a reduction of ceramide. Conversely, an increase of ceramide inhibited IL-2-rescued survival. IL-2 deprivation-induced activation of acid sphingomyelinase (SMase) and inhibition of glucosylceramide synthase (GCS) and sphingomyelin synthase (SMS) were normalized by IL-2 supplementation. A phosphatidyl inositol-3 (PI-3) kinase inhibitor, LY294002, inhibited IL-2-rescued survival, but a mitogen-activated protein kinase inhibitor, PD98059, and an inhibitor of Janus tyrosine kinase/signal transducer and activator of transcription pathway, AG490, did not. LY294002 inhibited IL-2-induced reduction of ceramide through activation of acid SMase and inhibition of GCS and SMS, suggesting the positive involvement of PI-3 kinase in ceramide reduction through enzymatic regulation. Indeed, a constitutively active PI-3 kinase enhanced growth rate and ceramide reduction through inhibition of acid SMase and activation of GCS and SMS. Further, LY294002 inhibited IL-2-induced changes of transcriptional level as well as mRNA and protein levels in acid SMase and GCS but did not affect the stability of the mRNAs. These results suggest that PI-3 kinase-dependent reduction of ceramide through regulation of acid SMase, GCS, and SMS plays a role in IL-2-rescued survival of NK cells.
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PMID:Interleukin-2-induced survival of natural killer (NK) cells involving phosphatidylinositol-3 kinase-dependent reduction of ceramide through acid sphingomyelinase, sphingomyelin synthase, and glucosylceramide synthase. 1527

Fumonisin B(1) (FB(1)) is a fungal toxin produced by Fusarium verticillioides that inhibits ceramide synthase (CS), a key enzyme in the de novo sphingolipid biosynthesis pathway. In LLC-PK(1) cells, FB(1) inhibits cell proliferation and induces apoptosis, which can be prevented by inhibitors of serine palmitoyltransferase (SPT). Inhibition of SPT prevents the FB(1)-induced accumulation of free sphinganine, a precursor of ceramide biosynthesis. However, not all of the effects of FB(1) in LLC-PK(1) cells can be explained solely by the increase in free sphingoid bases. The downstream signaling pathways that are affected by FB(1)-induced disruption of sphingolipid biosynthesis are not well understood. This study determined, in LLC-PK(1) cells, changes in p42 MAP kinase (phosphorylated ERK2 [pERK2]) phosphorylation in response to various inhibitors of key enzymes of the de novo sphingolipid biosynthesis pathway (CS, SPT, and glucosylceramide synthase [GlcCer synthase]). The results show that inhibition of any of the three enzymes caused a similar decrease in the extent of phosphorylation of ERK2 with no reduction in total ERK2. The co-treatment of FB(1) (CS inhibitor) with SPT inhibitors or the GlcCer synthase inhibitor had no effect on the FB(1)-induced reduction in pERK2 phosphorylation, indicating that FB(1)-mediated changes in phosphorylation of pERK2 was independent of increases in free sphinganine or its metabolites or a reduction in ceramide. Nonetheless, the decrease in pERK2 phosphorylation was dependent on inhibition of de novo sphingolipid biosynthesis. Decreased pERK2 activity could contribute to the physiological effects of FB(1) in LLC-PK(1) cells that are not due to alteration in pathways modulated by free sphingoid bases and their metabolites but are sensitive to inhibition of glycosphingolipid biosynthesis.
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PMID:Inhibition of sphingolipid biosynthesis decreases phosphorylated ERK2 in LLC-PK1 cells. 1558 4

Brain injury in hemolytic-uremic syndrome (HUS) may be enhanced by inflammatory cytokine up-regulation of endothelial cell sensitivity to shigatoxin (Stx). The present study investigated whether inflammatory cytokine up-regulation of Stx toxicity could be ameliorated by inhibiting candidate signal transduction pathways. Exposure of human brain endothelial cells (HBECs) to tumor necrosis factor (TNF) greatly increased Stx-1 and Stx-2 cytotoxicity; this was reduced by inhibition of p38 mitogen-activated protein kinase (MAPK), but not c-Jun kinase. SB203580, a specific inhibitor of p38 MAPK, reduced TNF-stimulated Stx cytotoxicity in HBECs, TNF-stimulated (125)Stx-1 binding to intact HBECs, the cellular content of Gb3 (galactose alpha 1,4, galactose ss 1,4, glucose-ceramide) (the Stx receptor), and TNF-stimulated Gb3 synthase and glucosylceramide synthase activities but did not affect lactosylceramide synthase activities or mRNA content. Thus, inhibition of p38 MAPK substantially reduces inflammatory cytokine up-regulation of Stx-receptor synthesis and cell-surface expression, thereby decreasing Stx cytotoxicity. Inhibition of p38 MAPK may be of therapeutic benefit in HUS.
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PMID:Inhibition of p38 mitogen-activated protein kinase ameliorates cytokine up-regulated shigatoxin-1 toxicity in human brain microvascular endothelial cells. 1563 6

The present study describes the role of glycosphingolipids in neuroinflammatory disease and investigates tumor necrosis factor alpha (TNFalpha)-induced astrogliosis following spinal cord injury. Astrogliosis is the hallmark of neuroinflammation and is characterized by proliferation of astrocytes and increased glial fibrillary acidic protein (GFAP) gene expression. In primary astrocytes, TNFalpha stimulation increased the intracellular levels of lactosylceramide (LacCer) and induced GFAP expression and astrocyte proliferation. D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol.HCl (PDMP), a glucosylceramide synthase and LacCer synthase (GalT-2) inhibitor, inhibited astrocyte proliferation and GFAP expression, which were reversed by exogenous supplementation of LacCer but not by other glycosphingolipids. TNFalpha caused a rapid increase in the activity of GalT-2 and synthesis of LacCer. Silencing of GalT-2 gene using antisense oligonucleotides also attenuated the proliferation of astrocytes and GFAP expression. The PDMP and antisense-mediated inhibition of proliferation and GFAP expression was well correlated with decreased Ras/ERK1/2 pathway activation. Furthermore, TNFalpha-mediated astrocyte proliferation and GFAP expression was also inhibited by LY294002, a phosphatidylinositol 3-kinase inhibitor, which was reversed by exogenous LacCer. LY294002 also inhibited TNFalpha-induced GalT-2 activation and LacCer synthesis, suggesting a phosphatidylinositol 3-kinase-mediated regulation of GalT-2. In vivo, PDMP treatment attenuated chronic ERK1/2 activation and spinal cord injury (SCI)-induced astrocyte proliferation with improved functional recovery post-SCI. Therefore, the in vivo studies support the conclusions drawn from cell culture studies and provide evidence for the role of LacCer in TNFalpha-induced astrogliosis in a rat model of SCI. To our knowledge, this is the first report demonstrating the role of LacCer in the regulation of TNFalpha-induced proliferation and reactivity of primary astrocytes.
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PMID:A novel role of lactosylceramide in the regulation of tumor necrosis factor alpha-mediated proliferation of rat primary astrocytes. Implications for astrogliosis following neurotrauma. 1566 27


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