Synthesis and evaluation of sphingoid analogs as inhibitors of sphingosine kinases (original) (raw)
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SphK1 and SphK2, Sphingosine Kinase Isoenzymes with Opposing Functions in Sphingolipid Metabolism
Journal of Biological Chemistry, 2005
The potent sphingolipid metabolite sphingosine-1-phosphate (S1P) is produced by phosphorylation of sphingosine catalyzed by sphingosine kinase (SphK) types 1 and 2. In contrast to pro-survival SphK1, the putative BH3only protein SphK2 inhibits cell growth and enhances apoptosis. Here we show that SphK2 catalytic activity also contributes to its ability to induce apoptosis. Overexpressed SphK2 also increased cytosolic free calcium induced by serum starvation. Transfer of calcium to mitochondria was required for SphK2induced apoptosis, as cell death and cytochrome c release was abrogated by inhibition of the mitochondrial Ca 2+ transporter. Serum-starvation increased the proportion of SphK2 in the ER and targeting SphK1 to the ER converted it from anti-apoptotic to pro-apoptotic. Overexpression of SphK2 increased incorporation of [ 3 H]palmitate, a s u b s t r a t e f o r b o t h s e r i n e palmitoyltransferase and ceramide synthase, into C16-ceramide, whereas SphK1 decreased it. ESI-MS/MS also revealed an opposite effect on ceramide mass levels. Importantly, specific downregulation of SphK2 reduced conversion of sphingosine to ceramide in the recycling pathway and conversely, downregulation of SphK1 increased it. Our results demonstrate that SphK1 and SphK2 have opposing roles in the regulation of ceramide biosynthesis and suggest that the location of S1P production dictates its functions.
Sphingosine kinase, sphingosine-1-phosphate, and apoptosis
Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, 2002
The sphingolipid metabolites ceramide (Cer), sphingosine (Sph), and sphingosine-1-phosphate (S1P) play an important role in the regulation of cell proliferation, survival, and cell death. Cer and Sph usually inhibit proliferation and promote apoptosis, while the further metabolite S1P stimulates growth and suppresses apoptosis. Because these metabolites are interconvertible, it has been proposed that it is not the absolute amounts of these metabolites but rather their relative levels that determines cell fate. The relevance of this ''sphingolipid rheostat'' and its role in regulating cell fate has been borne out by work in many labs using many different cell types and experimental manipulations. A central finding of these studies is that Sph kinase (SphK), the enzyme that phosphorylates Sph to form S1P, is a critical regulator of the sphingolipid rheostat, as it not only produces the pro-growth, anti-apoptotic messenger S1P, but also decreases levels of pro-apoptotic Cer and Sph.
Sphingosine kinases, sphingosine 1-phosphate, apoptosis and diseases
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2006
Sphingolipids are ubiquitous components of cell membranes and their metabolites ceramide (Cer), sphingosine (Sph), and sphingosine-1phosphate (S1P) have important physiological functions, including regulation of cell growth and survival. Cer and Sph are associated with growth arrest and apoptosis. Many stress stimuli increase levels of Cer and Sph, whereas suppression of apoptosis is associated with increased intracellular levels of S1P. In addition, extracellular/secreted S1P regulates cellular processes by binding to five specific G protein coupled-receptors (GPCRs). S1P is generated by phosphorylation of Sph catalyzed by two isoforms of sphingosine kinases (SphK), type 1 and type 2, which are critical regulators of the "sphingolipid rheostat", producing pro-survival S1P and decreasing levels of pro-apoptotic Sph. Since sphingolipid metabolism is often dysregulated in many diseases, targeting SphKs is potentially clinically relevant. Here we review the growing recent literature on the regulation and the roles of SphKs and S1P in apoptosis and diseases.
Pharmacological Research, 2003
Whereas some sphingolipids such as sphingoid bases and ceramide can mediate and induce cell killing, other sphingolipids such as sphingosine 1-phosphate promote cell survival or proliferation. The tight equilibrium between the intracellular levels of each of these biomodulators is controlled by the various enzymes that either produce or degrade these lipid molecules. Herein, the effects of sphingoid bases and their derivatives on the regulation of (cancer) cell growth and death are reviewed. In addition, the consequences of pharmacological manipulation of the enzymes that govern sphingoid base metabolism on in vitro and in vivo tumor cell growth are presented. Further development of pharmacological tools aimed at interfering with the metabolism of sphingolipids is expected to provide new avenues in the treatment of cancers as well as other diseases.
Advances in Biological Regulation, 2016
Sphingosine kinase (there are two isoforms, SK1 and SK2) catalyses the formation of sphingosine 1-phosphate (S1P), a bioactive lipid that can be released from cells to activate a family of G protein-coupled receptors, termed S1P 1-5. In addition, S1P can bind to intracellular target proteins, such as HDAC1/2, to induce cell responses. There is increasing evidence of a role for S1P receptors (e.g. S1P 4) and SK1 in cancer, where high expression of these proteins in ER negative breast cancer patient tumours is linked with poor prognosis. Indeed, evidence will be presented here to demonstrate that S1P 4 is functionally linked with SK1 and the oncogene HER2 (ErbB2) to regulate mitogen-activated protein kinase pathways and growth of breast cancer cells. Although much emphasis is placed on SK1 in terms of involvement in oncogenesis, evidence will also be presented for a role of SK2 in both T-cell and B-cell acute lymphoblastic leukemia. In patient TALL lymphoblasts and TALL cell lines, we have demonstrated that SK2 inhibitors promote TALL cell death via autophagy and induce suppression of c-myc and PI3K/AKT pathways. We will also present evidence demonstrating that certain SK inhibitors promote oxidative stress and protein turnover via proteasomal degradative pathways linked with induction of p53-and p21-induced growth Introduction-Formation of the bioactive lipid, sphingosine 1-phosphate (S1P) is catalysed by sphingosine kinase. There are two isoforms of sphingosine kinase (SK1 and SK2) which differ in their subcellular localisations, regulation and functions (Pyne et al., 2009). The S1P formed by these enzymes can either be exported from cells (through transporter proteins e.g. Spns2) and act as a ligand on a family of five S1P-specific G protein coupled receptors (S1P 1-5) (Blaho and Hla, 2014) or can bind to specific intracellular target proteins. For instance S1P formed by nuclear SK2 inhibits HDAC1/2 activity to induce c-fos and p21 expression (Hait et al., 2009). Dephosphorylation of S1P is catalysed by S1P phosphatase and the sphingosine formed is then acylated to ceramide catalysed by ceramide synthase isoforms (Stiban et al., 2010). S1P can also be irreversibly cleaved by S1P lyase to produce (E)-2 hexadecenal and phosphoethanolamine (Degagné et al., 2014). The interconversion of ceramide to sphingosine and S1P has been termed the sphingolipid rheostat (Newton et al., 2015). In this model, shifting the balance toward ceramide induces apoptosis, while predominance of S1P formation promotes cell survival. For instance, ceramide activates protein phosphatase 2A (Dobrowsky et al., 1993), which dephosphorylates phosphorylated AKT (Zhou et al., 1998) and thereby alters BAD/Bcl2 regulation to induce apoptosis (Zundel and Giaccia, 1998). In contrast, S1P promotes cell survival, involving for instance, activation of the extracellular signal regulated kinase-1/2 (ERK-1/2) pathway (Pyne et al., 2009). However, the sphingolipid rheostat exhibits greater complexity, as certain ceramide species regulate processes other than apoptosis, such as autophagy and proliferation. This suggests temporal and spatial regulation, where the functionality of the sphingolipid rheostat is governed by compartmentalised signalling involving, for instance, ceramide synthase isoforms that produce different ceramide species with specific stress-dependent signalling functions that govern a defined cellular outcome e.g. apoptosis versus proliferation. The conversion of S1P to (E)-2 hexadecenal and phosphoethanolamine is also considered an exit point in the
Sphingosine in apoptosis signaling
Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, 2002
The sphingolipid metabolites ceramide, sphingosine, and sphingosine 1-phosphate contribute to controlling cell proliferation and apoptosis. Ceramide and its catabolite sphingosine act as negative regulators of cell proliferation and promote apoptosis. Conversely, sphingosine 1-phosphate, formed by phosphorylation of sphingosine by a sphingosine kinase, has been involved in stimulating cell growth and inhibiting apoptosis. As the phosphorylation of sphingosine diminishes apoptosis, while dephosphorylation of sphingosine 1-phosphate potentiates it, the role of sphingosine as a messenger of apoptosis is of importance. Herein, the effects of sphingosine on diverse signaling pathways implicated in the apoptotic process are reviewed.
Inhibition of MAP kinase by sphingosine and its methylated derivative, N,N-dimethylsphingosine
International Journal of Oncology, 1997
Endogenous sphingolipid metabolites such as ceramides and sphingosines have been increasingly recognized as lipid mediators of cell growth, differentiation and apoptosis. We have previously studied the ability of sphingosine (Sph) and N,N-dimethylsphingosine (DMS) to induce apoptosis in a variety of solid tumor cell lines. Here we report that in tumor cell lines displaying high mitogen-activated protein kinase activity (MAPK), treatment with 5 |oM of these sphingolipids significantly inhibited MAPK activity within 2-5 min (p<0.005-0.01 as compared to controls) and induced apoptosis within hours. In contrast, untransformed cells and those tumor cell lines with low MAPK activity showed no significant change in activity and no apoptosis. High concentrations of C2-ceramide (50-100 mM), which induced apoptosis in the solid tumor cells, did not show significant effect on MAPK activity. MAPK activity was not directly inhibited in vitro, but tyrosine phosphatase activity was increased 2-4 fold in solid tumor cells by Sph or DMS (p<0.01-0.05), suggesting that a phosphatase may play an
Sphingosine-1-phosphate phosphohydrolase in regulation of sphingolipid metabolism and apoptosis
The Journal of Cell Biology, 2002
phingosine-1-phosphate (S1P) is a bioactive sphingolipid metabolite that regulates diverse biological processes by binding to a family of G protein-coupled receptors or as an intracellular second messenger. Mammalian S1P phosphatase (SPP-1), which degrades S1P to terminate its actions, was recently cloned based on homology to a lipid phosphohydrolase that regulates the levels of phosphorylated sphingoid bases in yeast. Confocal microscopy surprisingly revealed that epitope-tagged SPP-1 is intracellular and colocalized with the ER marker calnexin. Moreover, SPP-1 activity and protein appeared to be mainly enriched in the intracellular membranes with lower expression in the plasma membrane. Treatment of SPP-1 transfectants with S1P markedly increased ceramide levels, predominantly S in the intracellular membranes, diminished survival, and enhanced apoptosis. Remarkably, dihydro-S1P, although a good substrate for SPP-1 in situ, did not cause significant ceramide accumulation or increase apoptosis. Ceramide accumulation induced by S1P was completely blocked by fumonisin B1, an inhibitor of ceramide synthase, but only partially reduced by myriocin, an inhibitor of serine palmitoyltransferase, the first committed step in de novo synthesis of ceramide. Furthermore, S1P, but not dihydro-S1P, stimulated incorporation of [ 3 H]palmitate, a substrate for both serine palmitoyltransferase and ceramide synthase, into C16-ceramide. Collectively, our results suggest that SPP-1 functions in an unprecedented manner to regulate sphingolipid biosynthesis and is poised to influence cell fate.
Sphingosine-1-Phosphate, a Novel Lipid, Involved In Cellular Proliferation
The Journal of cell …, 1991
Abstract. Sphingosine, a metabolite of membrane sphingolipids, regulates proliferation of quiescent Swiss 3T3 fibroblasts (Zhang, H., NE Buckley, K. Gibson, and S. Spiegel. 1990. J. Biol. Chem. 265:76-81). The present study provides new insights into the formation and ...