Sphingosine

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Julie D Saba - One of the best experts on this subject based on the ideXlab platform.

  • An update on Sphingosine-1-phosphate and other sphingolipid mediators
    Nature Chemical Biology, 2010
    Co-Authors: Henrik Fyrst, Julie D Saba
    Abstract:

    Sphingolipids comprise a complex family of naturally occurring molecules that are enriched in lipid rafts and contribute to their unique biochemical properties. Membrane sphingolipids also serve as a reservoir for bioactive metabolites including Sphingosine, ceramide, Sphingosine-1-phosphate and ceramide-1-phosphate. Among these, Sphingosine-1-phosphate has emerged as a central regulator of mammalian biology. Sphingosine-1-phosphate is essential for mammalian brain and cardiac development and for maturation of the systemic circulatory system and lymphatics. In addition, Sphingosine-1-phosphate contributes to trafficking and effector functions of lymphocytes and other hematopoietic cells and protects against various forms of tissue injury. However, Sphingosine-1-phosphate is also an oncogenic lipid that promotes tumor growth and progression. Recent preclinical and clinical investigations using pharmacological agents that target Sphingosine-1-phosphate, its receptors and the enzymes required for its biosynthesis and degradation demonstrate the promise and potential risks of modulating Sphingosine-1-phosphate signaling in treatment strategies for autoimmunity, cancer, cardiovascular disease and other pathological conditions.

  • The immune modulator FTY720 inhibits Sphingosine-1-phosphate lyase activity
    Journal of Biological Chemistry, 2005
    Co-Authors: Padmavathi Bandhuvula, Babak Oskouian, Julie D Saba
    Abstract:

    Abstract FTY720 is a novel immunomodulatory agent that inhibits lymphocyte trafficking and prevents allograft rejection. FTY720 is phosphorylated in vivo, and the phosphorylated drug acts as agonist for a family of G protein-coupled receptors that recognize Sphingosine 1-phosphate. Evidence suggests that FTY720-phosphate-induced activation of S1P1 is responsible for its mechanism of action. FTY720 was rationally designed by modification of myriocin, a naturally occurring sphingoid base analog that causes immunosuppression by interrupting sphingolipid metabolism. In this study, we examined interactions between FTY720, FTY720-phosphate, and Sphingosine-1-phosphate lyase, the enzyme responsible for irreversible Sphingosine 1-phosphate degradation. FTY720-phosphate was stable in the presence of active Sphingosine-1-phosphate lyase, demonstrating that the lyase does not contribute to FTY720 catabolism. Conversely, FTY720 inhibited Sphingosine-1-phosphate lyase activity in vitro. Treatment of mice with FTY720 inhibited tissue Sphingosine-1-phosphate lyase activity within 12 h, whereas lyase gene and protein expression were not significantly affected. Tissue Sphingosine 1-phosphate levels remained stable or increased throughout treatment. These studies raise the possibility that disruption of Sphingosine 1-phosphate metabolism may account for some effects of FTY720 on immune function and that Sphingosine-1-phosphate lyase may be a potential target for immunomodulatory therapy.

  • Characterization of the Drosophila Sphingosine kinases and requirement for Sk2 in normal reproductive function.
    The Journal of biological chemistry, 2004
    Co-Authors: Deron R. Herr, Henrik Fyrst, Julie D Saba, Michael B. Creason, Van H. Phan, Greg L. Harris
    Abstract:

    Sphingosine kinase is a highly conserved enzyme that catalyzes the synthesis of Sphingosine 1-phosphate and reduces cellular levels of Sphingosine and ceramide. Although ceramide is pro-apoptotic and Sphingosine is generally growth-inhibitory, Sphingosine 1-phosphate signaling promotes cell proliferation, survival, and migration. Sphingosine kinase is thus in a strategic position to regulate important cell fate decisions which may contribute to normal animal development. To facilitate studies examining the potential role of Sphingosine kinase and long chain base metabolism in Drosophila development, we characterized two putative Drosophila Sphingosine kinase genes, Sk1 and Sk2. Both genes functionally and biochemically complement a yeast Sphingosine kinase mutant, express predominantly cytosolic activities, and are capable of phosphorylating a range of endogenous and non-endogenous sphingoid base substrates. The two genes demonstrate overlapping but distinct temporal and spatial expression patterns in the Drosophila embryo, and timing of expression is consistent with observed changes in long chain base levels throughout development. A null Sk2 transposon insertion mutant demonstrated elevated long chain base levels, impaired flight performance, and diminished ovulation. This is the first reported mutation of a Sphingosine kinase in an animal model; the associated phenotypes indicate that Sk1 and Sk2 are not redundant in biological function and that Sphingosine kinase is essential for diverse physiological functions in this organism.

  • The BST1 gene of Saccharomyces cerevisiae is the Sphingosine-1-phosphate lyase.
    Journal of Biological Chemistry, 1997
    Co-Authors: Julie D Saba, Alicia Bielawska, Futoshi Nara, Steven Garrett, Yusuf A Hannun
    Abstract:

    Abstract Sphingolipids elicit a wide variety of eukaryotic cellular responses, most involving regulation of cell growth, differentiation, and apoptosis. Sphingosine 1-phosphate, a sphingolipid catabolite, is mitogenic in fibroblasts and inhibits the chemotactic mobility and invasiveness of human tumor cells. Sphingosine 1-phosphate degradation requires cleavage at the C2–3 carbon bond by Sphingosine phosphate lyase. A yeast genetic approach was used to clone the first Sphingosine phosphate lyase gene, BST1. BST1 overexpression conferred resistance to Sphingosine in yeast.BST1 deletion produced sensitivity to exogenousd-erythro-Sphingosine and phytoSphingosine and intracellular accumulation of Sphingosine 1-phosphate upon exposure to exogenous Sphingosine. This study confirms that sphingoid base metabolism is similar in all eukaryotes and suggests that yeast genetics may be useful in the isolation and identification of other genes involved in sphingolipid signaling and metabolism.

Sarah Spiegel - One of the best experts on this subject based on the ideXlab platform.

  • Stimulation of nuclear Sphingosine kinase activity by platelet-derived growth factor.
    FEBS letters, 2001
    Co-Authors: Burkhard Kleuser, Sheldon Milstien, Michael Maceyka, Sarah Spiegel
    Abstract:

    Abstract Subcellular fractionation revealed that a significant fraction of total Sphingosine kinase, the enzyme that phosphorylates Sphingosine to form the bioactive lipid metabolite Sphingosine-1-phosphate, resides in the nuclei of Swiss 3T3 cells, localized to both the nuclear envelope and the nucleoplasm. Platelet-derived growth factor, in addition to rapidly stimulating cytosolic Sphingosine kinase, also induced a large increase in nucleoplasm-associated activity after 12–24 h that correlated with progression of cells to the S-phase of the cell cycle and translocation of Sphingosine kinase–green fluorescent protein fusion protein to the nuclear envelope. Our results add Sphingosine kinase to the growing list of lipid-metabolizing enzymes associated with the nucleus, and suggest that Sphingosine-1-phosphate may also play a role in signal transduction in the nucleus.

  • Effect of acidic phospholipids on Sphingosine kinase.
    Journal of cellular biochemistry, 1996
    Co-Authors: Ana Olivera, Jutta Rosenthal, Sarah Spiegel
    Abstract:

    Sphingosine-1-phosphate (SPP) is a unique sphingolipid metabolite involved in cell growth regulation and signal transduction. SPP is formed from Sphingosine in cells by the action of Sphingosine kinase, an enzyme whose activity can be stimulated by growth factors. Little is known of the mechanisms by which Sphingosine kinase is regulated. We found that acidic phospholipids, particularly phosphatidylserine, induced a dose-dependent increase in Sphingosine kinase activity due to an increase in the apparent Vmax of the enzyme. Other acidic phospholipids, such as phosphatidylinositol, phosphatidic acid, phosphatidylinositol bisphosphate, and cardiolipin stimulated Sphingosine kinase activity to a lesser extent than phosphatidylserine, whereas neutral phospholipids had no effect. Diacylglycerol, a structurally similar molecule which differs from phosphatidic acid in the absence of the phosphate group, failed to induce any changes in Sphingosine kinase activity. Our results suggest that the presence of negative charges on the lipid molecules is important for the potentiation of Sphingosine kinase activity, but the effect does not directly correlate with the number of negative charges. These results also support the notion that the polar group confers specificity in the stimulation of Sphingosine kinase by acidic glycerophospholipids. The presence of a fatty acid chain in position 2 of the glycerol backbone was not critical since lysophosphatidylserine also stimulated Sphingosine kinase, although it was somewhat less potent. Dioleoylphosphatidylserine was the most potent species, including a fourfold stimulation, whereas distearoyl phosphatidylserine was completely inactive. Thus, the degree of saturation of the fatty acid chain of the phospholipids may also play a role in the activation of Sphingosine kinase. © 1996 Wiley-Liss, Inc.

  • stereospecificity of Sphingosine induced intracellular calcium mobilization and cellular proliferation
    Journal of Biological Chemistry, 1994
    Co-Authors: Ana Olivera, Mark E. Mattie, Hong Zhang, R O Carlson, R R Schmidt, Sarah Spiegel
    Abstract:

    Abstract Sphingosine is a positive regulator of cell growth in Swiss 3T3 fibroblasts (Zhang, H., Buckley, N. E., Gibson, K., and Spiegel, S. (1990) J. Biol. Chem. 265, 76-81). The present study investigated the stereospecificity of Sphingosine-induced cell proliferation and its mitogenic signal transduction mechanisms. D-(+)-erythro Stereoisomers (cis and trans) stimulated DNA synthesis, whereas neither L-(-)-threo-Sphingosine (cis or trans) nor DL-threo-dihydroSphingosine had any effect. Previously, we have shown that Sphingosine-1-phosphate may mediate the mitogenic effect of Sphingosine (Zhang, H., Desai, N. N., Olivera, A., Seki, T., Brooker, G., and Spiegel, S. (1991) J. Cell Biol. 114, 155-167). However, no major differences were found in the formation of D-(+)-erythro- and L-(-)-threo- Sphingosine-1-phosphate derived from the respective Sphingosine isomers in intact cells. Thus, the stereospecificity of the response to Sphingosine may reside at the level of specific intracellular targets for Sphingosine-1-phosphate. Sphingosine-1-phosphate triggers dual signal transduction pathways of activation of phospholipase D leading to increases in the levels of phosphatidic acid and mobilization of calcium from internal stores. Both D-(+)-erythro- and L-(-)-threo-Sphingosine isomers induced similar increases in phosphatidic acid concomitant with identical decreases in phosphatidylcholine levels. In contrast, only the D-(+)-erythro-stereoisomers (cis and trans) were effective in releasing calcium from intracellular stores. Our results suggest that the formation of phosphatidic acid is not sufficient to mediate Sphingosine-stimulated DNA synthesis. However, the stereospecificity of the Sphingosine-induced mobilization of calcium from internal stores seems to correlate with the induction of DNA synthesis by Sphingosine stereoisomers.

  • Sphingosine-1-phosphate, a metabolite of Sphingosine, increases phosphatidic acid levels by phospholipase D activation.
    Journal of Biological Chemistry, 1992
    Co-Authors: N. N. Desai, Mark E. Mattie, Ana Olivera, Hong Zhang, Sarah Spiegel
    Abstract:

    Abstract Sphingosine and Sphingosine-1-phosphate, metabolites of membrane sphingolipids, have recently been shown to stimulate release of calcium from internal sources and to increase proliferation of quiescent Swiss 3T3 fibroblasts (Zhang, H., Desai, N. N., Olivera, A., Seki, T., Brooker, G., and Spiegel, S. (1991) J. Cell Biol. 114, 155-167). The present study demonstrates that mitogenic concentrations of Sphingosine induce early increases in Sphingosine-1-phosphate levels which precede the increase in the potent mitogen, phosphatidic acid. Sphingosine-1-phosphate itself induces a more rapid increase in phosphatidic acid, thus suggesting that it may mediate the effects of Sphingosine on phosphatidic acid accumulation. The concentration dependence for the formation of phosphatidic acid induced by Sphingosine-1-phosphate correlates with its effect on DNA synthesis. Similar to Sphingosine, Sphingosine-1-phosphate also stimulates the activity of phospholipase D, although a significant effect is observed at a much lower concentration. However, in contrast to previous reports with Sphingosine, Sphingosine-1-phosphate does not inhibit the phosphatidic acid phosphohydrolase activity in cell homogenates. Thus, in addition to its effect on mobilization of calcium, Sphingosine-1-phosphate can increase the level of phosphatidic acid, most likely via activation of phospholipase D. We suggest that Sphingosine-1-phosphate mediates the effect of Sphingosine on phosphatidic acid accumulation in Swiss 3T3 fibroblasts and may regulate cellular proliferation by affecting multiple transmembrane signaling pathways.

  • Sphingosine-1-phosphate, a novel lipid, involved in cellular proliferation.
    Journal of Cell Biology, 1991
    Co-Authors: Hong Zhang, N. N. Desai, Ana Olivera, T. Seki, Gary Brooker, Sarah Spiegel
    Abstract:

    Sphingosine, a metabolite of membrane sphingolipids, regulates proliferation of quiescent Swiss 3T3 fibroblasts (Zhang, H., N. E. Buckley, K. Gibson. and S. Spiegel. 1990. J. Biol. Chem. 265:76-81). The present study provides new insights into the formation and function of a unique phospholipid, a metabolite of Sphingosine, which was unequivocally identified as Sphingosine-1-phosphate. The rapid increase in 32P-labeled Sphingosine-1-phosphate levels induced by Sphingosine was concentration dependent and correlated with its effect on DNA synthesis. Similar to the mitogenic effects of Sphingosine, low concentrations of Sphingosine-1-phosphate stimulated DNA synthesis and induced pronounced morphological alterations. Both Sphingosine and Sphingosine-1-phosphate stimulated DNA synthesis in cells made protein kinase C deficient by prolonged treatment with phorbol ester and Sphingosine still elicited similar increases in Sphingosine-1-phosphate levels in these cells. Although both Sphingosine and Sphingosine-1-phosphate acted synergistically with a wide variety of growth factors, there was no additive or synergistic effect in response to a combination of Sphingosine and Sphingosine-1-phosphate. Using a digital imaging system for measurement of calcium changes, we observed that both Sphingosine and Sphingosine-1-phosphate are potent calcium-mobilizing agonists in viable 3T3 fibroblasts. The rapid rise in cytosolic free calcium was independent of the presence of calcium in the external medium, indicating that the response is due to the mobilization of calcium from internal store. Our results suggest that Sphingosine-1-phosphate may be a component of the intracellular second messenger system that is involved in calcium release and the regulation of cell growth induced by Sphingosine.

Osamu Kozawa - One of the best experts on this subject based on the ideXlab platform.

  • Involvement of Rho-kinase in Sphingosine 1-phosphate-stimulated HSP27 induction in osteoblasts
    International Journal of Molecular Medicine, 2009
    Co-Authors: Chiho Minamitani, Yoshiteru Hanai, Jun Mizutani, Shinji Takai, Haruhiko Tokuda, Rie Matsushima-nishiwaki, Takanobu Otsuka, Seiji Adachi, Osamu Kozawa
    Abstract:

    We previously reported that Sphingosine 1-phosphate induces heat shock protein 27 (HSP 27) via activation of phosphatidylinositol 3-kinase (PI3K)/Akt and p38 mitogen- activated protein (MAP) kinase in osteoblast-like MC3T3-E1 cells. In the present study, we investigated whether Rho-kinase is implicated in Sphingosine 1-phosphate-stimulated induction of HSP27 in MC3T3-E1 cells. Sphingosine 1-phosphate time- dependently induced the phosphorylation of myosin phos- phatase targeting subunit (MYPT-1), a Rho-kinase substrate. Y27632, a specific Rho-kinase inhibitor, significantly reduced Sphingosine 1-phosphate-stimulated HSP27 induction, as well as MYPT-1 phosphorylation. Fasudil, another inhibitor of Rho- kinase, also suppressed Sphingosine 1-phosphate-stimulated HSP27 induction. Y27632, as well as fasudil, attenuated Sphingosine 1-phosphate-induced phosphorylation of p38 MAP kinase. However, Akt phosphorylation induced by Sphingosine 1-phosphate was not affected by either Rho-kinase inhibitor. These results strongly suggest that Rho-kinase regulates Sphingosine 1-phosphate-stimulated induction of HSP27 at a point upstream of p38 MAP kinase in osteoblasts.

  • Sphingosine 1-phosphate induces heat shock protein 27 via p38 mitogen-activated protein kinase activation in osteoblasts.
    Journal of Bone and Mineral Research, 1999
    Co-Authors: Osamu Kozawa, Masaichi Miwa, Kanefusa Kato, Haruhiko Tokuda, Masayuki Niwa, Hiroyuki Matsuno, Toshihiko Uematsu
    Abstract:

    We previously showed that Sphingosine 1-phosphate acts as a second messenger for tumor necrosis factor α–induced interleukin-6 synthesis in osteoblast-like MC3T3-E1 cells and that the synthesis by Sphingosine 1-phosphate is dependent on p42/p44 mitogen-activated protein (MAP) kinase activation. In the present study, we investigated the effect of Sphingosine 1-phosphate on the induction of heat shock protein 27 (HSP27) in MC3T3-E1 cells. Not C2-ceramide, but Sphingosine and Sphingosine 1-phosphate significantly induced HSP27 accumulation dose dependently in the range between 1μM and 30 μM. DL-threo-dihydroSphingosine, an inhibitor of Sphingosine kinase, markedly inhibited the Sphingosine-induced HSP27 accumulation. Sphingosine 1-phosphate induced increase in the levels of the mRNA for HSP27. Sphingosine 1-phosphate stimulated the phosphorylation of p38 MAP kinase. The Sphingosine 1-phosphate–induced HSP27 accumulation was dose dependently suppressed by SB203580, an inhibitor of p38 MAP kinase, but not PD98059, an inhibitor of the upstream kinase that activates p42/p44 MAP kinase. SB203580 reduced the Sphingosine 1-phosphate–induced increase of mRNA for HSP27. These results strongly suggest that Sphingosine 1-phosphate–stimulated HSP27 induction is mediated via p38 MAP kinase activation in osteoblasts.

  • Sphingosine 1-phosphate regulates heat shock protein 27 induction by a p38 MAP kinase-dependent mechanism in aortic smooth muscle cells.
    Experimental Cell Research, 1999
    Co-Authors: Osamu Kozawa, Kanefusa Kato, Masayuki Niwa, Hiroyuki Matsuno, Kumiko Tanabe, Toshihiko Uematsu
    Abstract:

    Abstract In an aortic smooth muscle cell line, A10 cells, we investigated the effect of Sphingosine 1-phosphate on the induction of heat shock protein 27 (HSP27), a low-molecular-weight heat shock protein. Sphingosine 1-phosphate significantly induced the accumulation of HSP27 in a pertussis toxin-sensitive manner. The effect was dose-dependent in the range between 0.1 and 30 μM. Sphingosine 1-phosphate stimulated an increase in the levels of mRNA for HSP27. Sphingosine 1-phosphate stimulated both p42/p44 mitogen-activated protein (MAP) kinase and p38 MAP kinase activation. PD98059, an inhibitor of the upstream kinase that activates p42/p44 MAP kinase, did not affect Sphingosine 1-phosphate-stimulated HSP27 induction. In contrast, SB203580, an inhibitor of p38 MAP kinase, reduced Sphingosine 1-phosphate-induced HSP27 induction. SB203580 reduced the levels of mRNA for HSP27 induced by Sphingosine 1-phosphate. These results indicate that Sphingosine 1-phosphate stimulates the induction of HSP27 via p38 MAP kinase activation in aortic smooth muscle cells.

  • Sphingosine MODULATES INTERLEUKIN-6 SYNTHESIS IN OSTEOBLASTS
    Journal of cellular biochemistry, 1998
    Co-Authors: Osamu Kozawa, Haruhiko Tokuda, Hiroyuki Matsuno, Toshihiko Uematsu
    Abstract:

    We previously reported that prostaglandin (PG)E1 and PGF2alpha induce the synthesis of interleukin-6 (IL-6) via activation of protein kinase (PK)A and PKC, respectively, in osteoblast-like MC3T3-E1 cells. In addition, we have shown that basic fibroblast growth factor (bFGF) elicits IL-6 synthesis through intracellular Ca2+ mobilization in these cells and that tumor necrosis factor-alpha (TNF) induces IL-6 synthesis through Sphingosine 1-phosphate produced by sphingomyelin hydrolysis. In the present study, among sphingomyelin metabolites, we examined the effect of Sphingosine on IL-6 synthesis induced by various agonists in MC3T3-E1 cells. Sphingosine inhibited the IL-6 synthesis induced by PGF2alpha or 12-O-tetradecanoylphorbol-13-acetate, an activator of PKC. Sphingosine suppressed the PGE1-induced IL-6 synthesis. The IL-6 synthesis induced by cholera toxin, forskolin, or dibutyryl cAMP was inhibited by Sphingosine. Sphingosine inhibited the IL-6 synthesis induced by bFGF or A23187. However, Sphingosine did not affect the IL-6 synthesis induced by interleukin-1. On the contrary, Sphingosine enhanced the TNF-induced IL-6 synthesis. DL-threo-DihydroSphingosine, an inhibitor of Sphingosine kinase, reduced the enhancement by Sphingosine as well as the TNF-effect. These results indicate that Sphingosine modulates the IL-6 synthesis stimulated by various agonists in osteoblasts.

Toshihiko Uematsu - One of the best experts on this subject based on the ideXlab platform.

  • Sphingosine 1-phosphate induces heat shock protein 27 via p38 mitogen-activated protein kinase activation in osteoblasts.
    Journal of Bone and Mineral Research, 1999
    Co-Authors: Osamu Kozawa, Masaichi Miwa, Kanefusa Kato, Haruhiko Tokuda, Masayuki Niwa, Hiroyuki Matsuno, Toshihiko Uematsu
    Abstract:

    We previously showed that Sphingosine 1-phosphate acts as a second messenger for tumor necrosis factor α–induced interleukin-6 synthesis in osteoblast-like MC3T3-E1 cells and that the synthesis by Sphingosine 1-phosphate is dependent on p42/p44 mitogen-activated protein (MAP) kinase activation. In the present study, we investigated the effect of Sphingosine 1-phosphate on the induction of heat shock protein 27 (HSP27) in MC3T3-E1 cells. Not C2-ceramide, but Sphingosine and Sphingosine 1-phosphate significantly induced HSP27 accumulation dose dependently in the range between 1μM and 30 μM. DL-threo-dihydroSphingosine, an inhibitor of Sphingosine kinase, markedly inhibited the Sphingosine-induced HSP27 accumulation. Sphingosine 1-phosphate induced increase in the levels of the mRNA for HSP27. Sphingosine 1-phosphate stimulated the phosphorylation of p38 MAP kinase. The Sphingosine 1-phosphate–induced HSP27 accumulation was dose dependently suppressed by SB203580, an inhibitor of p38 MAP kinase, but not PD98059, an inhibitor of the upstream kinase that activates p42/p44 MAP kinase. SB203580 reduced the Sphingosine 1-phosphate–induced increase of mRNA for HSP27. These results strongly suggest that Sphingosine 1-phosphate–stimulated HSP27 induction is mediated via p38 MAP kinase activation in osteoblasts.

  • Sphingosine 1-phosphate regulates heat shock protein 27 induction by a p38 MAP kinase-dependent mechanism in aortic smooth muscle cells.
    Experimental Cell Research, 1999
    Co-Authors: Osamu Kozawa, Kanefusa Kato, Masayuki Niwa, Hiroyuki Matsuno, Kumiko Tanabe, Toshihiko Uematsu
    Abstract:

    Abstract In an aortic smooth muscle cell line, A10 cells, we investigated the effect of Sphingosine 1-phosphate on the induction of heat shock protein 27 (HSP27), a low-molecular-weight heat shock protein. Sphingosine 1-phosphate significantly induced the accumulation of HSP27 in a pertussis toxin-sensitive manner. The effect was dose-dependent in the range between 0.1 and 30 μM. Sphingosine 1-phosphate stimulated an increase in the levels of mRNA for HSP27. Sphingosine 1-phosphate stimulated both p42/p44 mitogen-activated protein (MAP) kinase and p38 MAP kinase activation. PD98059, an inhibitor of the upstream kinase that activates p42/p44 MAP kinase, did not affect Sphingosine 1-phosphate-stimulated HSP27 induction. In contrast, SB203580, an inhibitor of p38 MAP kinase, reduced Sphingosine 1-phosphate-induced HSP27 induction. SB203580 reduced the levels of mRNA for HSP27 induced by Sphingosine 1-phosphate. These results indicate that Sphingosine 1-phosphate stimulates the induction of HSP27 via p38 MAP kinase activation in aortic smooth muscle cells.

  • Sphingosine MODULATES INTERLEUKIN-6 SYNTHESIS IN OSTEOBLASTS
    Journal of cellular biochemistry, 1998
    Co-Authors: Osamu Kozawa, Haruhiko Tokuda, Hiroyuki Matsuno, Toshihiko Uematsu
    Abstract:

    We previously reported that prostaglandin (PG)E1 and PGF2alpha induce the synthesis of interleukin-6 (IL-6) via activation of protein kinase (PK)A and PKC, respectively, in osteoblast-like MC3T3-E1 cells. In addition, we have shown that basic fibroblast growth factor (bFGF) elicits IL-6 synthesis through intracellular Ca2+ mobilization in these cells and that tumor necrosis factor-alpha (TNF) induces IL-6 synthesis through Sphingosine 1-phosphate produced by sphingomyelin hydrolysis. In the present study, among sphingomyelin metabolites, we examined the effect of Sphingosine on IL-6 synthesis induced by various agonists in MC3T3-E1 cells. Sphingosine inhibited the IL-6 synthesis induced by PGF2alpha or 12-O-tetradecanoylphorbol-13-acetate, an activator of PKC. Sphingosine suppressed the PGE1-induced IL-6 synthesis. The IL-6 synthesis induced by cholera toxin, forskolin, or dibutyryl cAMP was inhibited by Sphingosine. Sphingosine inhibited the IL-6 synthesis induced by bFGF or A23187. However, Sphingosine did not affect the IL-6 synthesis induced by interleukin-1. On the contrary, Sphingosine enhanced the TNF-induced IL-6 synthesis. DL-threo-DihydroSphingosine, an inhibitor of Sphingosine kinase, reduced the enhancement by Sphingosine as well as the TNF-effect. These results indicate that Sphingosine modulates the IL-6 synthesis stimulated by various agonists in osteoblasts.

Stuart M Pitson - One of the best experts on this subject based on the ideXlab platform.

  • Cigarette smoke inhibits efferocytosis via deregulation of Sphingosine kinase signaling: reversal with exogenous S1P and the S1P analogue FTY720
    Journal of leukocyte biology, 2016
    Co-Authors: Hai B. Tran, Stuart M Pitson, Jameel Barnawi, Miranda P. Ween, Rhys Hamon, Eugene Roscioli, Greg Hodge, Paul N. Reynolds, Lorena T. Davies, Rainer Viktor Haberberger
    Abstract:

    Alveolar macrophages from chronic obstructive pulmonary disease patients and cigarette smokers are deficient in their ability to phagocytose apoptotic bronchial epithelial cells (efferocytosis). We hypothesized that the defect is mediated via inhibition of Sphingosine kinases and/or their subcellular mislocalization in response to cigarette smoke and can be normalized with exogenous Sphingosine-1-phosphate or FTY720 (fingolimod), a modulator of Sphingosine-1-phosphate signaling, which has been shown to be clinically useful in multiple sclerosis. Measurement of Sphingosine kinase 1/2 activities by [(32)P]-labeled Sphingosine-1-phosphate revealed a 30% reduction of Sphingosine kinase 1 (P < 0.05) and a nonsignificant decrease of Sphingosine kinase 2 in THP-1 macrophages after 1 h cigarette smoke extract exposure. By confocal analysis macrophage Sphingosine kinase 1 protein was normally localized to the plasma membrane and cytoplasm and Sphingosine kinase 2 to the nucleus and cytoplasm but absent at the cell surface. Cigarette smoke extract exposure (24 h) led to a retraction of Sphingosine kinase 1 from the plasma membrane and Sphingosine kinase 1/2 clumping in the Golgi domain. Selective inhibition of Sphingosine kinase 2 with 25 µM ABC294640 led to 36% inhibition of efferocytosis (P < 0.05); 10 µM Sphingosine kinase inhibitor/5C (Sphingosine kinase 1-selective inhibitor) induced a nonsignificant inhibition of efferocytosis, but its combination with ABC294640 led to 56% inhibition (P < 0.01 vs. control and < 0.05 vs. single inhibitors). Cigarette smoke-inhibited efferocytosis was significantly (P < 0.05) reversed to near-control levels in the presence of 10-100 nM exogenous Sphingosine-1-phosphate or FTY720, and FTY720 reduced cigarette smoke-induced clumping of Sphingosine kinase 1/2 in the Golgi domain. These data strongly support a role of Sphingosine kinase 1/2 in efferocytosis and as novel therapeutic targets in chronic obstructive pulmonary disease.

  • Sphingosine kinase localization in the control of sphingolipid metabolism
    Advances in enzyme regulation, 2010
    Co-Authors: Deanna L. Siow, Stuart M Pitson, Charles D. Anderson, Evgeny V. Berdyshev, Anastasia Skobeleva, Viswanathan Natarajan, Binks W. Wattenberg
    Abstract:

    The Sphingosine kinases (Sphingosine kinase-1 and −2) have been implicated in a variety of physiological functions. Discerning their mechanism of action is complicated because in addition to producing the potent lipid second messenger Sphingosine-1-phoshphate, Sphingosine kinases, both by producing Sphingosine-1-phosphate and consuming Sphingosine, have profound effects on sphingolipid metabolism. Sphingosine kinase-1 translocates to the plasma membrane upon agonist stimulation and this translocation is essential for the pro-oncogenic properties of this enzyme. Many of the enzymes of sphingolipid metabolism, including the enzymes that degrade Sphingosine-1-phosphate, are membrane-bound with restricted subcellular distributions. In the work describe here we explore how subcellular localization of Sphingosine kinase-1 affects the downstream metabolism of Sphingosine-1-phosphate and the access of Sphingosine kinase to its substrates. We find, surprisingly, that restricting Sphingosine kinase to either the plasma membrane or the endoplasmic reticulum has a negligible effect on the rate of degradation of the Sphingosine-1-phosphate that is produced. This suggests that Sphingosine-1-phosphate is rapidly transported between membranes. However we also find that cytosolic or endoplasmic-reticulum targeted Sphingosine kinase expressed at elevated levels produces extremely high levels of dihydroSphingosine-1-phosphate. DihydroSphingosine is a proximal precursor in ceramide biosynthesis. Our data indicate that Sphingosine kinase can divert substrate from the ceramide de novo synthesis pathway. However plasma membrane-restricted Sphingosine kinase cannot access the pool of dihydroSphingosine. Therefore whereas Sphingosine kinase localization does not affect downstream metabolism of Sphingosine-1-phosphate, localization has an important effect on the pools of substrate to which this key signaling enzyme has access.

  • Sphingosine kinase 1 is a critical component of the copper-dependent FGF1 export pathway.
    Experimental cell research, 2007
    Co-Authors: Raffaella Soldi, Stuart M Pitson, Mathew Alexander Vadas, Anna Mandinova, Krishnan Venkataraman, Timoty Hla, Maria F. Duarte, Irene Graziani, Vihren Kolev, Doreen Kacer
    Abstract:

    Sphingosine kinase 1 catalyzes the formation of Sphingosine-1-phosphate, a lipid mediator involved in the regulation of angiogenesis. Sphingosine kinase 1 is constitutively released from cells, even though it lacks a classical signal peptide sequence. Because copper-dependent non-classical stress-induced release of FGF1 also regulates angiogenesis, we questioned whether Sphingosine kinase 1 is involved in the FGF1 release pathway. We report that (i) the coexpression of Sphingosine kinase 1 with FGF1 inhibited the release of Sphingosine kinase 1 at 37 °C; (ii) Sphingosine kinase 1 was released at 42 °C in complex with FGF1; (iii) Sphingosine kinase 1 null cells failed to release FGF1 at stress; (iv) Sphingosine kinase 1 is a high affinity copper-binding protein which formed a complex with FGF1 in a cell-free system, and (v) Sphingosine kinase 1 over expression rescued the release of FGF1 from inhibition by the copper chelator, tetrathiomolybdate. We propose that Sphingosine kinase 1 is a component of the copper-dependent FGF1 release pathway.

  • An assay for Sphingosine kinase activity using biotinylated Sphingosine and streptavidin-coated membranes.
    Analytical biochemistry, 2004
    Co-Authors: Jane Roberts, Claudia K Derian, Paul A.b. Moretti, Andrew L. Darrow, Mathew Alexander Vadas, Stuart M Pitson
    Abstract:

    Sphingosine kinase catalyses the phosphorylation of Sphingosine to generate Sphingosine 1-phosphate, a lipid signaling molecule implicated in roles in a diverse range of mammalian cell processes through its action as both a ligand for G-protein-coupled cell-surface receptors and an apparent intracellular second messenger. This paper describes a rapid, sensitive, and reproducible assay for Sphingosine kinase activity using biotinylated Sphingosine (biotinyl-Sph) as a substrate and capturing the phosphorylated product with streptavidin-coated membranes. We have shown that both human Sphingosine kinase 1 and 2 (hSK1 and hSK2) can efficiently phosphorylate biotinyl-Sph, with K(m) values similar to those of Sphingosine. The assay utilizing this substrate has high sensitivity for hSK1 and hSK2, with detection limits in the low-femtomole range for both purified recombinant enzymes. Importantly, we have also demonstrated the capacity of this assay to measure endogenous Sphingosine kinase activity in crude cell extracts and to follow changes in this activity following Sphingosine kinase activation. Together, these results demonstrate the potential utility of this assay in both cell-based analysis of Sphingosine kinase signaling pathways and high-throughput screens for agents affecting Sphingosine kinase activity in vitro.

  • Activation of Sphingosine kinase 1 by ERK1/2‐mediated phosphorylation
    The EMBO journal, 2003
    Co-Authors: Stuart M Pitson, Paul A.b. Moretti, Julia R Zebol, Mathew Alexander Vadas, Helen E. Lynn, Pu Xia, Binks W. Wattenberg
    Abstract:

    Sphingosine kinase 1 is an agonist-activated signalling enzyme that catalyses the formation of Sphingosine 1-phosphate, a lipid second messenger that has been implicated in a number of agonist-driven cellular responses, including stimulation of cell proliferation, inhibition of apoptosis and expression of inflammatory molecules. Although agonist-induced stimulation of Sphingosine kinase activity is critical in a number of signalling pathways, nothing has been known of the molecular mechanism of this activation. Here we show that this activation results directly from phosphorylation of Sphingosine kinase 1 at Ser225, and present several lines of evidence to show compellingly that the activating kinase is ERK1/2 or a close relative. Furthermore, we show that phosphorylation of Sphingosine kinase 1 at Ser225 results not only in an increase in enzyme activity, but is also necessary for translocation of the enzyme from the cytosol to the plasma membrane. Thus, these studies have elucidated the mechanism of agonist-mediated Sphingosine kinase activation, and represent a key finding in understanding the regulation of Sphingosine kinase/Sphingosine 1-phosphate-controlled signalling pathways.