Structural analysis of neutral glycosphingolipids from the silkworm Bombyx mori and the difference in ceramide composition between larvae and pupae.

Glycosphingolipids (GSLs) from the silkworm Bombyx mori were identified and GSL expression patterns between larvae and pupae were compared. The structural analysis of neutral GSLs from dried pupae revealed the following predominant species: Glcß1Cer, Manß4Glcß1Cer, GlcNAcß3Manß4Glcß1Cer, Galß3Manß4Glcß1Cer, GalNAcα4Galß3Manß4Glcß1Cer, GlcNAcß3Galß3Manß4Glcß1Cer, Galα4Galß3Manß4Glcß1Cer and (GalNAcα4)1-4 GalNAcα4Galß3Manß4Glcß1Cer. Lin-ear elongation of α4-GalNAc was observed at the non-reducing end of Galß3Manß4Glcß1Cer with up to five GalNAc repeats. The arthro-series GSL GlcNAcß3Manß4Glcß1Cer, a characteristic GSL-glycan sequence of other Arthropoda, was detected in silkworms. The main ceramide species in each purified GSL fraction were h20:0-d14:1 and h22:0-d14:1. GSL expression patterns in larvae and pupae were compared using thin-layer chromatography, which demonstrated differences among acidic, polar and neutral GSL fractions, while the zwitterionic fraction showed no difference. Neutral GSLs such as ceramides di-, tri- and tetrasaccharides in larvae showed less abundant than those in pupae. MALDI-TOF MS analysis revealed that larval GSLs contained four types of ceramide species, whereas pupal GSLs contained only two types. The structural analysis of neutral GSLs from silkworms revealed a novel series of GSLs. The comparison of GSL expression patterns between larvae and pupae demonstrated differences in several fractions. Alterations in GSL ceramide composition between larvae and pupae were observed by MALDI-TOF MS analysis.

Characterization of a Novel Rhamnose-containing Acidic Glycosphingolipid from the Ascidian Halocynthia aurantium.

Halocynthia aurantium, an edible ascidian species belonging to Urochordata, was subjected to structural characterization of acidic glycosphingolipids to investigate these molecules in ascidians: sulfatide from Ciona intestinalis and the glucuronic acid-containing acidic glycosphingolipid from H. roretzi. Acidic glycosphingolipids containing three or five sugars were isolated from soft parts of the ascidian H. aurantium by chloroform-methanol extraction, mild-alkaline hydrolysis, precipitation with cold acetone, and subsequent column chromatography using a DEAE-Sephadex A-25 column, a Florisil column, and an Iatrobead column. The structures of these glycosphingolipids were determined by methylation studies, sugar analysis, fatty acid analysis, sphingoid analysis, mass spectrometry, and proton nuclear magnetic resonance spectroscopy. A novel glucuronic acid-containing glycosphingolipid having a rhamnose residue was identified as Rhaα1-3GlcNAcß1-3Galß1-4(Fucα1-3)GlcAß1-Cer (UGL-2). This novel structure is particularly unusual given that it contains both a rhamnose residue and a reducing terminal glucuronic acid residue within a single molecule. Rhamnose is a characteristic sugar, which is a component of cell wall pectin in plants and exopolysaccharides in bacteria. Ascidians acquired the cellulose synthase gene via lateral gene transfer, and therefore, it can be speculated that they also acquired the rhamnosyltransferase gene in the same manner. We also detected Galß1-4(Fucα1-3)GlcAß1-Cer (UGL-1), which was already identified in another ascidian, H. roretzi.

Structural Characterization of Neutral Glycosphingolipids from 3T3-L1 Adipocytes.

In recent years, obesity has been considered a pathological stage of early lifestyle-related diseases, and adipose tissue and adipocyte research has been active. Glycosphingolipids are involved in the pathogenesis of type 2 diabetes induced by insulin resistance, but the details of the glycosphingolipid molecular species composition of adipocytes have yet to be elucidated. We used 3T3-L1 adipocytes and the 1,2-dichloroethane-wash method to remove triacylglycerols, which are abundant in adipocytes, and analyzed the structures of glycosphingolipids, particularly neutral glycosphingolipids, using liquid chromatography-mass spectrometry.

Investigation of glycan evolution based on a comprehensive analysis of glycosyltransferases using phylogenetic profiling.

Glycans play important roles in such cell-cell interactions as signaling and adhesion, including processes involved in pathogenic infections, cancers, and neurological diseases. Glycans are biosynthesized by multiple glycosyltransferases (GTs), which function sequentially. Excluding mucin-type O-glycosylation, the non-reducing terminus of glycans is biosynthesized in the Golgi apparatus after the reducing terminus is biosynthesized in the ER. In the present study, we performed genome-wide analyses of human GTs by investigating the degree of conservation of homologues in other organisms, as well as by elucidating the phylogenetic relationship between cephalochordates and urochordates, which has long been controversial in deuterostome phylogeny. We analyzed 173 human GTs and functionally linked glycan synthesis enzymes by phylogenetic profiling and clustering, compiled orthologous genes from the genomes of other organisms, and converted them into a binary sequence based on the presence (1) or absence (0) of orthologous genes in the genomes. Our results suggest that the non-reducing terminus of glycans is biosynthesized by newly evolved GTs. According to our analysis, the phylogenetic profiles of GTs resemble the phylogenetic tree of life, where deuterostomes, metazoans, and eukaryotes are resolved into separate branches. Lineage-specific GTs appear to play essential roles in the divergence of these particular lineages. We suggest that urochordates lose several genes that are conserved among metazoans, such as those expressing sialyltransferases, and that the Golgi apparatus acquires the ability to synthesize glycans after the ER acquires this function.

Biochemical studies on sphingolipids of Artemia franciscana: complex neutral glycosphingolipids.

Brine shrimp are primitive crustacean arthropodal model organisms, second to daphnia, which can survive in high-salinity environments. Their oviposited cysts, cuticle-covered diapausing eggs, are highly resistant to dryness. To elucidate specialties of brine shrimp, this study characterized glycosphingolipids, which are signal transduction-associated material. A group of novel and complex fucosyl glycosphingolipids were separated and identified from cysts of the brine shrimp Artemia franciscana by repeated lipid extraction, alkaline methanolysis, acid treatment, successive column chromatography, and post-source decay measurements by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Structures of the glycosphingolipids were elucidated by conventional structural characterization and mass spectrometry, and the compounds were identified as GlcNAcß1-3GalNAcß1-4(GlcNAcα1-2Fucα1-3)GlcNAcß1-3Manß1-4Glcß1-Cer, GalNAcß1-4(Fucα1-3)GlcNAcß1-3GalNAcß1-4(GlcNAcα1-2Fucα1-3)GlcNAcß1-3Manß1-4Glcß1-Cer, and GalNAcß1-4(GlcNAcα1-2Fucα1-3)GlcNAcß1-3GalNAcß1-4(GlcNAcα1-2Fucα1-3)GlcNAcß1-3Manß1-4Glcß1-Cer. These compounds also contained a branching, non-arthro-series disaccharide with an α-GlcNAc terminus, similar to that found in a previously reported ceramide hexasaccharide (III(3)(GlcNAcα2Fucα)-At4Cer). The glycans within these complex GSLs are longer than reported glycans of the animal kingdom containing α-GlcNAc terminus. These complex GSLs as well as the longest GSL with ten sugar residues, ceramide decasaccharide (CDeS), contain the fucosylated LacdiNAc sequence reported to associate with parasitism/immunosuppression and the α-GlcNAc terminus reported to show a certain antibacterial effect in other reports. CDeS, the longest GSL of this species, was found in the highest amount, which indicates that CDeS may be functionally important.

Biochemical studies on sphingolipids of Artemia franciscana: novel neutral glycosphingolipids.

Neutral glycosphingolipids containing one to six sugars in their oligosaccharide chains have been isolated from cysts of the brine shrimp Artemia franciscana. The structures of these glycolipids were identified by methylation analysis, partial acid hydrolysis, gas-liquid chromatography, combined gas-liquid chromatography-mass spectrometry, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and proton nuclear magnetic resonance spectroscopy to be Glcß1-Cer, Manß1-4Glcß1-Cer, Fucα1-3Manß1-4Glcß1-Cer, GlcNAcß1-3Manß1-4Glcß1-Cer, GlcNAcα1-2Fucα1-3Manß1-4Glcß1-Cer, GalNAcß1-4GlcNAcß1-3Manß1-4Glcß1-Cer, GalNAcß1-4(Fucα1-3)GlcNAcß1-3Manß1-4Glcß1-Cer (CPS), and GalNAcß1-4(GlcNAcα1-2Fucα1-3)GlcNAcß1-3Manß1-4Glcß1-Cer (CHS). Two glycosphingolipids, CPS and CHS, were characterized as novel structures. Because Artemia contains a certain series of glycosphingolipids (-Fucα3Manß4GlcßCer), which differ from the core sugar sequences reported thus far, we tentatively designated the glycosphingolipids characterized as nonarthro-series ones. Furthermore, CHS exhibited a hybrid structure of arthro-series and nonarthro-series sugar chain. Two novel glycosphingolipids were characterized from the brine shrimp Artemia franciscana; one was composed of arthrotetraose and a branching fucose attached to N-acetylglucosamine residue, and the other was composed of CPS with an additional N-acetylglucosamine residue attached to the branching fucose.

Biochemical studies on sphingolipid of Artemia franciscana (I) isolation and characterization of sphingomyelin.

Sphingomyelin was isolated from cysts of the brine shrimp Artemia franciscana using QAE-Sephadex A25, Florisil and Iatrobeads column chromatographies. The chemical structure was identified using thin-layer chromatography, gas-liquid chromatography, infrared spectroscopy and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The ceramide moiety of sphingomyelin consisted of stearic, arachidic, and behenic acids as fatty acids, and hexadeca-4- and heptadeca-4-sphingenines as sphingoids. By comparative analysis, the ceramide component of Artemia sphingomyelin appears unique in invertebrates and vertebrates. Biological functions of sphingomyelin have largely been investigated using mammalian-derived sphingomyelin. In mammals, a wide variety of molecular species of sphingomyelins have been reported, especially derived from nerve tissue, while the lower animal Artemia contains this unusual sphingomyelin perhaps because of having a much simpler nervous system. The purified unusual sphingomyelin derived from Artemia franciscana might be a very useful tool in elucidating the functions and mechanisms of action of this mediator.

Cell-specific expression of enhanced green fluorescence protein under the control of neuropeptide gene promoters in the brain of the silkworm, Bombyx mori, using Bombyx mori nucleopolyhedrovirus-derived vectors.

Using the larvae of the silkworm, Bombyx mori, we examined the baculovirus expression vector system for the expression of the enhanced green fluorescence protein (EGFP) gene under the control of several gene promoters in vivo. To investigate the gene-delivery efficiency of the baculovirus into various larval tissues, we constructed two recombinant baculoviruses carrying the EGFP gene downstream of the Drosophila melanogaster hsp70 gene promoter from B. mori nucleopolyhedrovirus (BmNPV) and Autographa californica nucleopolyhedrovirus (AcNPV). After injection of these recombinant baculoviruses into newly ecdysed 5th instar larvae, hsp70::EGFP-BmNPV, but not hsp70::EGFP-AcNPV, caused intense expression of EGFP not only in various non-neural tissues, but also in the neural organs including the brain 5 days postinfection. To investigate the cell-specific expression in the brain, we constructed recombinant C4/B3::EGFP-BmNPV and PTTH::EGFP-BmNPV which carry the EGFP gene under the control of bombyxin B3 and prothoracicotropic hormone (PTTH) gene promoters, respectively. Injection of these recombinant baculoviruses caused specific expression of EGFP with a high gene-expression efficiency in the neurosecretory cells of the brain depending on the neurohormone gene promoters. Present results indicate that this in vivo gene-expression system mediated by the baculovirus can serve as an efficient system permitting gene delivery into neural tissues in insects.