Publications

• C26-CoA-dependent ceramide synthesis of Saccharomyces cerevisiae is operated by Lag1p and Lac1p.

  Guillas I., Kirchman P.A., Chuard R., Pfefferli M., Jiang J.C., Jazwinski S.M., Conzelmann A.

  Lag1p and Lac1p are two highly homologous membrane proteins of the endoplasmic reticulum (ER). When both genes are deleted, cells cannot transport glycosylphosphatidylinositol (GPI)-anchored proteins from the ER to the Golgi at a normal rate. Here we show that microsomes or detergent extracts from ... >> More

  Lag1p and Lac1p are two highly homologous membrane proteins of the endoplasmic reticulum (ER). When both genes are deleted, cells cannot transport glycosylphosphatidylinositol (GPI)-anchored proteins from the ER to the Golgi at a normal rate. Here we show that microsomes or detergent extracts from lag1lac1 double mutants lack an activity transferring C26 fatty acids from C26-coenzyme A onto dihydrosphingosine or phytosphingosine. As a consequence, in intact cells, the normal ceramides and inositolphosphorylceramides are drastically reduced. lag1lac1 cells compensate for the lack of normal sphingolipids by making increased amounts of C26 fatty acids, which become incorporated into glycerophospholipids. They also contain 20-to 25-fold more free long chain bases than wild type and accumulate very large amounts of abnormally polar ceramides. They make small amounts of abnormal mild base-resistant inositolphospholipids. The lipid remodelling of GPI-anchored proteins is severely compromised in lag1lac1 double mutants since only few and mostly abnormal ceramides are incorporated into the GPI anchors. The participation of Lag1p and Lac1p in ceramide synthesis may explain their role in determining longevity. << Less

  EMBO J. 20:2655-2665(2001) [PubMed] [EuropePMC]

  This publication is cited by 9 other entries.

• A critical role for ceramide synthase 2 in liver homeostasis: I. alterations in lipid metabolic pathways.

  Pewzner-Jung Y., Park H., Laviad E.L., Silva L.C., Lahiri S., Stiban J., Erez-Roman R., Bruegger B., Sachsenheimer T., Wieland F., Prieto M., Merrill A.H. Jr., Futerman A.H.

  Ceramide is an important lipid signaling molecule that plays critical roles in regulating cell behavior. Ceramide synthesis is surprisingly complex and is orchestrated by six mammalian ceramide synthases, each of which produces ceramides with restricted acyl chain lengths. We have generated a CerS ... >> More

  Ceramide is an important lipid signaling molecule that plays critical roles in regulating cell behavior. Ceramide synthesis is surprisingly complex and is orchestrated by six mammalian ceramide synthases, each of which produces ceramides with restricted acyl chain lengths. We have generated a CerS2 null mouse and characterized the changes in the long chain base and sphingolipid composition of livers from these mice. Ceramide and downstream sphingolipids were devoid of very long (C22-C24) acyl chains, consistent with the substrate specificity of CerS2 toward acyl-CoAs. Unexpectedly, C16-ceramide levels were elevated, and as a result, total ceramide levels were unaltered; however, C16-ceramide synthesis in vitro was not increased. Levels of sphinganine were also significantly elevated, by up to 50-fold, reminiscent of the effect of the ceramide synthase inhibitor, fumonisin B1. With the exceptions of glucosylceramide synthase and neutral sphingomyelinase 2, none of the other enzymes tested in either the sphingolipid biosynthetic or degradative pathways were significantly changed. Total glycerophospholipid and cholesterol levels were unaltered, although there was a marked elevation in C18:1 and C18:2 fatty acids in phosphatidylethanolamine, concomitant with a reduction in C18:0 and C20:4 fatty acids. Finally, differences were observed in the biophysical properties of lipid extracts isolated from liver microsomes, with membranes from CerS2 null mice displaying higher membrane fluidity and showing morphological changes. Together, these results demonstrate novel modes of cross-talk and regulation between the various branches of lipid metabolic pathways upon inhibition of very long acyl chain ceramide synthesis. << Less

  J. Biol. Chem. 285:10902-10910(2010) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• 2-Hydroxy-ceramide synthesis by ceramide synthase family: enzymatic basis for the preference of FA chain length.

  Mizutani Y., Kihara A., Chiba H., Tojo H., Igarashi Y.

  Ceramide is unusually abundant in epidermal stratum corneum and is important for permeability barrier function. Ceramides in epidermis also comprise an unusual variety, including 2-hydroxy (alpha-hydroxy)-ceramide. Six mammalian ceramide synthase/longevity assurance homologue (CerS/LASS) family me ... >> More

  Ceramide is unusually abundant in epidermal stratum corneum and is important for permeability barrier function. Ceramides in epidermis also comprise an unusual variety, including 2-hydroxy (alpha-hydroxy)-ceramide. Six mammalian ceramide synthase/longevity assurance homologue (CerS/LASS) family members have been identified as synthases responsible for ceramide (CER) production. We reveal here that of the six, CerS3/LASS3 mRNA is the most predominantly expressed in keratinocytes. Moreover, its expression is increased upon differentiation. CerS family members have known substrate specificities for fatty acyl-CoA chain length and saturation, yet their abilities to produce 2-hydroxy-CER have not been examined. In the present study, we demonstrate that all CerS members can produce 2-hydroxy-CER when overproduced in HEK 293T cells. Each produced a 2-hydroxy-CER with a chain length similar to that of the respective nonhydroxy-CER produced. In HeLa cells overproducing the FA 2-hydroxylase FA2H, knock-down of CerS2 resulted in a reduction in total long-chain 2-hydroxy-CERs, confirming enzyme substrate specificity for chain length. In vitro CerS assays confirmed the ability of CerS1 to utilize 2-hydroxy-stearoyl-CoA as a substrate. These results suggest that all CerS members can synthesize 2-hydroxy-CER with specificity for 2-hydroxy-fatty acyl-CoA chain length and that CerS3 may be important in CER and 2-hydroxy-CER synthesis in epidermis. << Less

  J. Lipid Res. 49:2356-2364(2008) [PubMed] [EuropePMC]

  This publication is cited by 9 other entries.

• Kinetic characterization of mammalian ceramide synthases: determination of K(m) values towards sphinganine.

  Lahiri S., Lee H., Mesicek J., Fuks Z., Haimovitz-Friedman A., Kolesnick R.N., Futerman A.H.

  Ceramide is a key metabolite in the pathway of sphingolipid biosynthesis. In mammals, ceramide is synthesized by N-acylation of a sphingoid long-chain base by a family of ceramide synthases (CerS), each of which displays a high specificity towards acyl CoAs of different chain lengths. We now optim ... >> More

  Ceramide is a key metabolite in the pathway of sphingolipid biosynthesis. In mammals, ceramide is synthesized by N-acylation of a sphingoid long-chain base by a family of ceramide synthases (CerS), each of which displays a high specificity towards acyl CoAs of different chain lengths. We now optimize a previously-described assay for measuring CerS activity for use upon over-expression of mammalian CerS, and using these conditions, establish the K(m) value of each CerS towards sphinganine. Remarkably, the K(m) values towards sphinganine are all similar, ranging from 2 to 5microM, even for CerS proteins that are able to use more than one acyl CoA for ceramide synthesis (i.e. CerS4). The availability of this assay will permit further accurate characterization of the kinetic parameters of mammalian CerS proteins. << Less

  FEBS Lett. 581:5289-5294(2007) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Loss of ceramide synthase 3 causes lethal skin barrier disruption.

  Jennemann R., Rabionet M., Gorgas K., Epstein S., Dalpke A., Rothermel U., Bayerle A., van der Hoeven F., Imgrund S., Kirsch J., Nickel W., Willecke K., Riezman H., Groene H.J., Sandhoff R.

  The stratum corneum as the outermost epidermal layer protects against exsiccation and infection. Both the underlying cornified envelope (CE) and the intercellular lipid matrix contribute essentially to these two main protective barriers. Epidermis-unique ceramides with ultra-long-chain acyl moitie ... >> More

  The stratum corneum as the outermost epidermal layer protects against exsiccation and infection. Both the underlying cornified envelope (CE) and the intercellular lipid matrix contribute essentially to these two main protective barriers. Epidermis-unique ceramides with ultra-long-chain acyl moities (ULC-Cers) are key components of extracellular lipid lamellae (ELL) and are bound to CE proteins, thereby contributing to the cornified lipid envelope (CLE). Here, we identified human and mouse ceramide synthase 3 (CerS3), among CerS1-6, to be exclusively required for the ULC-Cer synthesis in vitro and of mouse CerS3 in vivo. Deficiency of CerS3 in mice results in complete loss of ULC-Cers (≥C26), lack of continuous ELL and a non-functional CLE. Consequently, newborn mutant mice die shortly after birth from transepidermal water loss. Mutant skin is prone to Candida albicans infection highlighting ULC-Cers to be pivotal for both barrier functions. Persistent periderm, hyperkeratosis and deficient cornification are hallmarks of mutant skin demonstrating loss of Cers to trigger a keratinocyte maturation arrest at an embryonic pre-barrier stage. << Less

  Hum. Mol. Genet. 21:586-608(2012) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.

• Human homologues of LAG1 reconstitute Acyl-CoA-dependent ceramide synthesis in yeast.

  Guillas I., Jiang J.C., Vionnet C., Roubaty C., Uldry D., Chuard R., Wang J., Jazwinski S.M., Conzelmann A.

  Lag1p and Lac1p are two highly homologous membrane proteins of the endoplasmic reticulum. lag1delta lac1delta double mutants in Saccharomyces cerevisiae lack an acyl-CoA-dependent ceramide synthase and are either very sick or nonviable, depending on the genetic background. LAG1 and LAC1 are member ... >> More

  Lag1p and Lac1p are two highly homologous membrane proteins of the endoplasmic reticulum. lag1delta lac1delta double mutants in Saccharomyces cerevisiae lack an acyl-CoA-dependent ceramide synthase and are either very sick or nonviable, depending on the genetic background. LAG1 and LAC1 are members of a large eukaryotic gene family that shares the Lag1 motif, and some members of this family additionally contain a DNA-binding HOX homeodomain. Here we show that several human LAG1 homologues can rescue the viability of lag1delta lac1delta yeast cells and restore acyl-CoA-dependent ceramide and sphingolipid biosynthesis. When tested in a microsomal assay, Lac1p and Lag1p had a strong preference for C26:0-CoA over C24:0-CoA, C20-CoA, and C16-CoA, whereas some human homologues preferred C24:0-CoA and CoA derivatives with shorter fatty acids. This suggests that LAG1 proteins are related to substrate recognition and to the catalytic activity of ceramide synthase enzymes. CLN8, another human LAG1 homologue implicated in ceroid lipofuscinosis, could not restore viability to lag1delta lac1delta yeast mutants. << Less

  J. Biol. Chem. 278:37083-37091(2003) [PubMed] [EuropePMC]

  This publication is cited by 5 other entries.

• LASS3 (longevity assurance homologue 3) is a mainly testis-specific (dihydro)ceramide synthase with relatively broad substrate specificity.

  Mizutani Y., Kihara A., Igarashi Y.

  The LASS (longevity assurance homologue) family members are highly conserved from yeasts to mammals. Five mouse and human LASS family members, namely LASS1, LASS2, LASS4, LASS5 and LASS6, have been identified and characterized. In the present study we cloned two transcriptional variants of hithert ... >> More

  The LASS (longevity assurance homologue) family members are highly conserved from yeasts to mammals. Five mouse and human LASS family members, namely LASS1, LASS2, LASS4, LASS5 and LASS6, have been identified and characterized. In the present study we cloned two transcriptional variants of hitherto-uncharacterized mouse LASS3 cDNA, which encode a 384-amino-acid protein (LASS3) and a 419-amino-acid protein (LASS3-long). In vivo, [3H]dihydrosphingosine labelling and electrospray-ionization MS revealed that overproduction of either LASS3 isoform results in increases in several ceramide species, with some preference toward those having middle-to long-chain-fatty acyl-CoAs. A similar substrate preference was observed in an in vitro (dihydro)ceramide synthase assay. These results indicate that LASS3 possesses (dihydro)ceramide synthesis activity with relatively broad substrate specificity. We also found that, except for a weak display in skin, LASS3 mRNA expression is limited almost solely to testis, implying that LASS3 plays an important role in this gland. << Less

  Biochem. J. 398:531-538(2006) [PubMed] [EuropePMC]

  This publication is cited by 4 other entries.

• Mammalian Lass6 and its related family members regulate synthesis of specific ceramides.

  Mizutani Y., Kihara A., Igarashi Y.

  The Lass (longevity-assurance homologue) family members, which are highly conserved among eukaryotes, function in ceramide synthesis. In the mouse, there are at least five Lass family members, Lass1, Lass2, Lass4, Lass5 and the hitherto uncharacterized Lass6. To investigate specific roles for each ... >> More

  The Lass (longevity-assurance homologue) family members, which are highly conserved among eukaryotes, function in ceramide synthesis. In the mouse, there are at least five Lass family members, Lass1, Lass2, Lass4, Lass5 and the hitherto uncharacterized Lass6. To investigate specific roles for each Lass member in ceramide synthesis, we cloned these five mouse proteins. Overproduction of any Lass protein in cultured cells resulted in an increase in cellular ceramide, but the ceramide species produced varied. Overproduction of Lass1 increased C18:0-ceramide levels preferentially, and overproduction of Lass2 and Lass4 increased levels of longer ceramides such as C22:0- and C24:0-ceramides. Lass5 and Lass6 produced shorter ceramide species (C14:0- and C16:0-ceramides); however, their substrate preferences towards saturated/unsaturated fatty acyl-CoA differed. In addition to differences in substrate preferences, we also demonstrated by Northern blotting that Lass family members are differentially expressed among tissues. Additionally, we found that Lass proteins differ with regard to glycosylation. Of the five members, only Lass2, Lass5 and Lass6 were N-glycosylated, each at their N-terminal Asn residue. The occurrence of N-glycosylation of some Lass proteins provides topological insight, indicating that the N-termini of Lass family members probably face the luminal side of the endoplasmic reticulum membrane. Furthermore, based on a proteinase K digestion assay, we demonstrated that the C-terminus of Lass6 faces the cytosolic side of the membrane. From these data we propose topology for the conserved Lag1 motif in Lass family members, namely that the N-terminal region faces the luminal side and the C-terminal region the cytosolic side of the endoplasmic reticulum membrane. << Less

  Biochem. J. 390:263-271(2005) [PubMed] [EuropePMC]

  This publication is cited by 7 other entries.

• Characterization of ceramide synthase 2: tissue distribution, substrate specificity, and inhibition by sphingosine 1-phosphate.

  Laviad E.L., Albee L., Pankova-Kholmyansky I., Epstein S., Park H., Merrill A.H. Jr., Futerman A.H.

  Ceramide is an important lipid signaling molecule and a key intermediate in sphingolipid biosynthesis. Recent studies have implied a previously unappreciated role for the ceramide N-acyl chain length, inasmuch as ceramides containing specific fatty acids appear to play defined roles in cell physio ... >> More

  Ceramide is an important lipid signaling molecule and a key intermediate in sphingolipid biosynthesis. Recent studies have implied a previously unappreciated role for the ceramide N-acyl chain length, inasmuch as ceramides containing specific fatty acids appear to play defined roles in cell physiology. The discovery of a family of mammalian ceramide synthases (CerS), each of which utilizes a restricted subset of acyl-CoAs for ceramide synthesis, strengthens this notion. We now report the characterization of mammalian CerS2. qPCR analysis reveals that CerS2 mRNA is found at the highest level of all CerS and has the broadest tissue distribution. CerS2 has a remarkable acyl-CoA specificity, showing no activity using C16:0-CoA and very low activity using C18:0, rather utilizing longer acyl-chain CoAs (C20-C26) for ceramide synthesis. There is a good correlation between CerS2 mRNA levels and levels of ceramide and sphingomyelin containing long acyl chains, at least in tissues where CerS2 mRNA is expressed at high levels. Interestingly, the activity of CerS2 can be regulated by another bioactive sphingolipid, sphingosine 1-phosphate (S1P), via interaction of S1P with two residues that are part of an S1P receptor-like motif found only in CerS2. These findings provide insight into the biochemical basis for the ceramide N-acyl chain composition of cells, and also reveal a novel and potentially important interplay between two bioactive sphingolipids that could be relevant to the regulation of sphingolipid metabolism and the opposing functions that these lipids play in signaling pathways. << Less

  J. Biol. Chem. 283:5677-5684(2008) [PubMed] [EuropePMC]

  This publication is cited by 7 other entries.