Publications

• Synaptic vesicle ceramide kinase. A calcium-stimulated lipid kinase that co-purifies with brain synaptic vesicles.

  Bajjalieh S.M., Martin T.F., Floor E.

  Much current work on the mechanism of neurosecretion has focused on proteins specific to neural secretory vesicles (synaptic vesicles). We report a calcium-stimulated lipid kinase that co-purifies with rat brain synaptic vesicles. This enzyme activity is found only in membrane fractions that conta ... >> More

  Much current work on the mechanism of neurosecretion has focused on proteins specific to neural secretory vesicles (synaptic vesicles). We report a calcium-stimulated lipid kinase that co-purifies with rat brain synaptic vesicles. This enzyme activity is found only in membrane fractions that contain synaptic vesicle markers. Based on identification of the lipid product as ceramide 1-phosphate and on the finding that ceramide kinase activity co-purifies with synaptic vesicles, the enzyme is proposed to be a ceramide kinase. Kinase activity is stimulated by micromolar concentrations of calcium. Calcium increases the apparent Vmax of the reaction with little effect on the Km for ceramide. The vesicular localization of this enzyme, the requirement for ATP, and the stimulation of enzyme activity by micromolar calcium suggest that ceramide phosphorylation may be associated with neurotransmitter release. << Less

  J Biol Chem 264:14354-14360(1989) [PubMed] [EuropePMC]

• Ceramides modulate programmed cell death in plants.

  Liang H., Yao N., Song J.T., Luo S., Lu H., Greenberg J.T.

  The balance between the bioactive sphingolipid ceramide and its phosphorylated derivative has been proposed to modulate the amount of programmed cell death (PCD) in eukaryotes. We characterized the first ceramide kinase (CERK) mutant in any organism. The Arabidopsis CERK mutant, called accelerated ... >> More

  The balance between the bioactive sphingolipid ceramide and its phosphorylated derivative has been proposed to modulate the amount of programmed cell death (PCD) in eukaryotes. We characterized the first ceramide kinase (CERK) mutant in any organism. The Arabidopsis CERK mutant, called accelerated cell death 5, accumulates CERK substrates and shows enhanced disease symptoms during pathogen attack and apoptotic-like cell death dependent on defense signaling late in development. ACD5 protein shows high specificity for ceramides in vitro. Strikingly, C2 ceramide induces, whereas its phosphorylated derivative partially blocks, plant PCD, supporting a role for ceramide phosphorylation in modulating cell death in plants. << Less

  Genes Dev. 17:2636-2641(2003) [PubMed] [EuropePMC]

• A conserved cysteine motif is critical for rice ceramide kinase activity and function.

  Bi F.C., Zhang Q.F., Liu Z., Fang C., Li J., Su J.B., Greenberg J.T., Wang H.B., Yao N.

  <h4>Background</h4>Ceramide kinase (CERK) is a key regulator of cell survival in dicotyledonous plants and animals. Much less is known about the roles of CERK and ceramides in mediating cellular processes in monocot plants. Here, we report the characterization of a ceramide kinase, OsCERK, from ri ... >> More

  <h4>Background</h4>Ceramide kinase (CERK) is a key regulator of cell survival in dicotyledonous plants and animals. Much less is known about the roles of CERK and ceramides in mediating cellular processes in monocot plants. Here, we report the characterization of a ceramide kinase, OsCERK, from rice (Oryza sativa spp. Japonica cv. Nipponbare) and investigate the effects of ceramides on rice cell viability.<h4>Principal findings</h4>OsCERK can complement the Arabidopsis CERK mutant acd5. Recombinant OsCERK has ceramide kinase activity with Michaelis-Menten kinetics and optimal activity at 7.0 pH and 40°C. Mg2+ activates OsCERK in a concentration-dependent manner. Importantly, a CXXXCXXC motif, conserved in all ceramide kinases and important for the activity of the human enzyme, is critical for OsCERK enzyme activity and in planta function. In a rice protoplast system, inhibition of CERK leads to cell death and the ratio of added ceramide and ceramide-1-phosphate, CERK's substrate and product, respectively, influences cell survival. Ceramide-induced rice cell death has apoptotic features and is an active process that requires both de novo protein synthesis and phosphorylation, respectively. Finally, mitochondria membrane potential loss previously associated with ceramide-induced cell death in Arabidopsis was also found in rice, but it occurred with different timing.<h4>Conclusions</h4>OsCERK is a bona fide ceramide kinase with a functionally and evolutionarily conserved Cys-rich motif that plays an important role in modulating cell fate in plants. The vital function of the conserved motif in both human and rice CERKs suggests that the biochemical mechanism of CERKs is similar in animals and plants. Furthermore, ceramides induce cell death with similar features in monocot and dicot plants. << Less

  PLoS ONE 6:E18079-E18079(2011) [PubMed] [EuropePMC]

• Further characterization of mammalian ceramide kinase: substrate delivery and (stereo)specificity, tissue distribution, and subcellular localization studies.

  Van Overloop H., Gijsbers S., Van Veldhoven P.P.

  Recombinant human ceramide kinase (HsCERK) was analyzed with regard to dependence on divalent cations and to substrate delivery, spectrum, specificity, and stereoselectivity. Depending on the chain length of the ceramide, either albumin for short-chain ceramide or a mixed micellar form (octylgluco ... >> More

  Recombinant human ceramide kinase (HsCERK) was analyzed with regard to dependence on divalent cations and to substrate delivery, spectrum, specificity, and stereoselectivity. Depending on the chain length of the ceramide, either albumin for short-chain ceramide or a mixed micellar form (octylglucoside/cardiolipin) for long-chain ceramide was preferred for the substrate delivery, the former resulting in higher activities. Bacterially expressed HsCERK was highly dependent on Mg2+ ions, much less on Ca2+ ions. A clear preference for the d-erythro isomer was seen. Various N-acylated amino alcohols were no substrate, but N-hexanoyl-1-O-hexadecyl-2-desoxy-2-amino-sn-glycerol and N-tetradecanoyl-2S-amino-1-butanol were phosphorylated, suggesting that the secondary hydroxy group is not required for recognition. The properties of HsCERK, expressed in CHO cells, were similar to those of the bacterially expressed protein, including the Mg2+ dependence. In mouse, the highest activities were found in testis and cerebellum, and upon subcellular fractionation the activity was recovered mainly in the microsomal fraction. This fits with the plasma membrane localization in CHO cells, which was mediated by the N-terminal putative pleckstrin domain. No evidence for phosphorylation of ceramide by the recently described multiple lipid kinase was found. The latter kinase is localized in the mitochondria, but no firm conclusions with regard to its substrate could be drawn. << Less

  J. Lipid Res. 47:268-283(2006) [PubMed] [EuropePMC]

  This publication is cited by 4 other entries.

• A lipid binding domain in sphingosine kinase 2.

  Don A.S., Rosen H.

  The lipid second messenger sphingosine 1-phosphate (S1P) is a critical mediator of cellular proliferation and survival signals, and is essential for vasculogenesis and neurogenesis. S1P formation is catalysed by sphingosine kinases 1 and 2 (Sphk1 and Sphk2). We have found that the endogenous glyco ... >> More

  The lipid second messenger sphingosine 1-phosphate (S1P) is a critical mediator of cellular proliferation and survival signals, and is essential for vasculogenesis and neurogenesis. S1P formation is catalysed by sphingosine kinases 1 and 2 (Sphk1 and Sphk2). We have found that the endogenous glycolipid sulfatide (3-O-sulfogalactosylceramide) binds to and inhibits the activity of Sphk2 and the closely related ceramide kinase (Cerk), but not Sphk1. Using sulfatide as a probe, we mapped the lipid binding domain to the N-terminus of Sphk2 (residues 1-175), a region of sequence that is absent in Sphk1, but aligns with a pleckstrin homology domain in Cerk. Accordingly, Sphk2 bound to phosphatidylinositol monophosphates but not to abundant cellular phospholipids. Deleting the N-terminal domain reduced Sphk2 membrane localisation in cells. We have therefore identified a lipid binding domain in Sphk2 that is important for the enzyme's sub-cellular localisation. << Less

  Biochem. Biophys. Res. Commun. 380:87-92(2009) [PubMed] [EuropePMC]

• MuLK, a eukaryotic multi-substrate lipid kinase.

  Waggoner D.W., Johnson L.B., Mann P.C., Morris V., Guastella J., Bajjalieh S.M.

  We report the identification and characterization of a novel lipid kinase that phosphorylates multiple substrates. This enzyme, which we term MuLK for multi-substrate lipid kinase, does not belong to a previously described lipid kinase family. MuLK has orthologs in many organisms and is broadly ex ... >> More

  We report the identification and characterization of a novel lipid kinase that phosphorylates multiple substrates. This enzyme, which we term MuLK for multi-substrate lipid kinase, does not belong to a previously described lipid kinase family. MuLK has orthologs in many organisms and is broadly expressed in human tissues. Although predicted to be a soluble protein, MuLK co-fractionates with membranes and localizes to an internal membrane compartment. Recombinant MuLK phosphorylates diacylglycerol, ceramide, and 1-acylglycerol but not sphingosine. Although its affinity for diacylglycerol and ceramide are similar, MuLK exhibits a higher V(max) toward diacylglycerol in vitro, consistent with it acting primarily as a diacylglycerol kinase. MuLK activity was inhibited by sphingosine and enhanced by cardiolipin. It was stimulated by calcium when magnesium concentrations were low and inhibited by calcium when magnesium concentrations were high. The effects of charged lipids and cations on MuLK activity in vitro suggest that its activity in vivo is tightly regulated by cellular conditions. << Less

  J. Biol. Chem. 279:38228-38235(2004) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.