Glucosylceramide in T cells regulates the pathology of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disease in the colon characterized by excessive activation of T cells. Glycosphingolipids (GSLs) are composed of lipid rafts in cellular membranes, and their content is linked to immune cell function. In the present study, we investigated the involvement of GSLs in IBD. Microarray data showed that in IBD patients, the expression of only UDP-glucose ceramide glucosyltransferase (UGCG) decreased among the GSLs synthases. Ad libitum access to dextran sulfate sodium (DSS) resulted in decreased UGCG and glucosylceramide (GlcCer) content in mesenteric lymph nodes and T cells from the spleen. Furthermore, the knockdown of Ugcg in T cells exacerbated the pathogenesis of colitis, which was accompanied by a decrease in Treg levels. Treatment with GlcCer nanoparticles prevented DSS-induced colitis. These results suggested that GlcCer in T cells is involved in the pathogenesis of IBD. Furthermore, GlcCer nanoparticles are a potential efficacious therapeutic target for IBD patients.

Cellular and biochemical response to chaperone versus substrate reduction therapies in neuropathic Gaucher disease

Gaucher disease (GD) is caused by deficiency of the lysosomal membrane enzyme glucocerebrosidase (GCase) and the subsequent accumulation of its substrate, glucosylceramide (GC). Mostly missense mutations of the glucocerebrosidase gene (GBA) cause GCase misfolding and inhibition of proper lysosomal trafficking. The accumulated GC leads to lysosomal dysfunction and impairs the autophagy pathway. GD types 2 and 3 (GD2-3), or the neuronopathic forms, affect not only the Central Nervous System (CNS) but also have severe systemic involvement and progressive bone disease. Enzyme replacement therapy (ERT) successfully treats the hematologic manifestations; however, due to the lack of equal distribution of the recombinant enzyme in different organs, it has no direct impact on the nervous system and has minimal effect on bone involvement. Small molecules have the potential for better tissue distribution. Ambroxol (AMB) is a pharmacologic chaperone that partially recovers the mutated GCase activity and crosses the blood-brain barrier. Eliglustat (EGT) works by inhibiting UDP-glucosylceramide synthase, an enzyme that catalyzes GC biosynthesis, reducing GC influx load into the lysosome. Substrate reduction therapy (SRT) using EGT is associated with improvement in GD bone marrow burden score and bone mineral density parallel with the improvement in hematological parameters. We assessed the effects of EGT and AMB on GCase activity and autophagy-lysosomal pathway (ALP) in primary cell lines derived from patients with GD2-3 and compared to cell lines from healthy controls. We found that EGT, same as AMB, enhanced GCase activity in control cells and that an individualized response, that varied with GBA mutations, was observed in cells from patients with GD2-3. EGT and AMB enhanced the formation of lysosomal/late endosomal compartments and improved autophagy, independent of GBA mutations. Both AMB and EGT increased mitochondrial mass and density in GD2-3 fibroblasts, suggesting enhancement of mitochondrial function by activating the mitochondrial membrane potential. These results demonstrate that EGT and AMB, with different molecular mechanisms of action, enhance GCase activity and improve autophagy-lysosome dynamics and mitochondrial functions.

Sphingadienine-1-phosphate levels are regulated by a novel glycoside hydrolase family 1 glucocerebrosidase widely distributed in seed plants

Long-chain base phosphates (LCBPs) such as sphingosine-1-phosphate and phytosphingosine-1-phosphate function as abscisic acid (ABA)-mediated signaling molecules that regulate stomatal closure in plants. Recently, a glycoside hydrolase family 1 (GH1) β-glucosidase, Os3BGlu6, was found to improve drought tolerance by stomatal closure in rice, but the biochemical functions of Os3BGlu6 have remained unclear. Here we identified Os3BGlu6 as a novel GH1 glucocerebrosidase (GCase) that catalyzes the hydrolysis of glucosylceramide to ceramide. Phylogenetic and enzymatic analyses showed that GH1 GCases are widely distributed in seed plants and that pollen or anthers of all seed plants tested had high GCase activity, but activity was very low in ferns and mosses. Os3BGlu6 had high activity for glucosylceramides containing (4E,8Z)-sphingadienine, and GCase activity in leaves, stems, roots, pistils, and anthers of Os3BGlu6-deficient rice mutants was completely absent relative to that of wild-type rice. The levels of ceramides containing sphingadienine were correlated with GCase activity in each rice organ and were significantly lower in Os3BGlu6-deficient rice mutants than in the wild type. The levels of LCBPs synthesized from ceramides, especially the levels of sphingadienine-1-phosphate, were also correlated with GCase activity in each rice organ and were significantly lower in Os3BGlu6-deficient rice mutants than in the wild type. These results indicate that Os3BGlu6 regulates the level of ceramides containing sphingadienine, influencing the regulation of sphingadienine-1-phosphate levels and subsequent improvement of drought tolerance via stomatal closure in rice.

Complex formation of sphingomyelin synthase 1 with glucosylceramide synthase increases sphingomyelin and decreases glucosylceramide levels

Sphingolipids, including sphingomyelin (SM) and glucosylceramide (GlcCer), are generated by the addition of a polar head group to ceramide (Cer). Sphingomyelin synthase 1 (SMS1) and glucosylceramide synthase (GCS) are key enzymes that catalyze the conversion of Cer to SM and GlcCer, respectively. GlcCer synthesis has been postulated to occur mainly in cis-Golgi, and SM synthesis is thought to occur in medial/trans-Golgi; however, SMS1 and GCS are known to partially co-localize in cisternae, especially in medial/trans-Golgi. Here, we report that SMS1 and GCS can form a heteromeric complex, in which the N terminus of SMS1 and the C terminus of GCS are in close proximity. Deletion of the N-terminal sterile α-motif of SMS1 reduced the stability of the SMS1-GCS complex, resulting in a significant reduction in SM synthesis in vivo In contrast, chemical-induced heterodimerization augmented SMS1 activity, depending on an increase in the amount and stability of the complex. Fusion of the SMS1 N terminus to the GCS C terminus via linkers of different lengths increased SM synthesis and decreased GlcCer synthesis in vivo These results suggest that formation of the SMS1-GCS heteromeric complex increases SM synthesis and decreases GlcCer synthesis. Importantly, this regulation of relative Cer levels by the SMS1-GCS complex was confirmed by CRISPR/Cas9-mediated knockout of SMS1 or GCS combined with pharmacological inhibition of Cer transport protein in HEK293T cells. Our findings suggest that complex formation between SMS1 and GCS is part of a critical mechanism controlling the metabolic fate of Cer in the Golgi.

Changes in glucosylceramide structure affect virulence and membrane biophysical properties of Cryptococcus neoformans

Fungal glucosylceramide (GlcCer) is a plasma membrane sphingolipid in which the sphingosine backbone is unsaturated in carbon position 8 (C8) and methylated in carbon position 9 (C9). Studies in the fungal pathogen, Cryptococcus neoformans, have shown that loss of GlcCer synthase activity results in complete loss of virulence in the mouse model. However, whether the loss of virulence is due to the lack of the enzyme or to the loss of the sphingolipid is not known. In this study, we used genetic engineering to alter the chemical structure of fungal GlcCer and studied its effect on fungal growth and pathogenicity. Here we show that unsaturation in C8 and methylation in C9 is required for virulence in the mouse model without affecting fungal growth in vitro or common virulence factors. However, changes in GlcCer structure led to a dramatic susceptibility to membrane stressors resulting in increased cell membrane permeability and rendering the fungal mutant unable to grow within host macrophages. Biophysical studies using synthetic vesicles containing GlcCer revealed that the saturated and unmethylated sphingolipid formed vesicles with higher lipid order that were more likely to phase separate into ordered domains. Taken together, these studies show for the first time that a specific structure of GlcCer is a major regulator of membrane permeability required for fungal pathogenicity.

Elisidepsin Interacts Directly with Glycosylceramides in the Plasma Membrane of Tumor Cells to Induce Necrotic Cell Death

Plasma membrane integrity is essential for cell life. Any major break on it immediately induces the death of the affected cell. Different molecules were described as disrupting this cell structure and thus showing antitumor activity. We have previously defined that elisidepsin (Irvalec^®, PM02734) inserts and self-organizes in the plasma membrane of tumor cells, inducing a rapid loss of membrane integrity, cell permeabilization and necrotic death. Here we show that, in sensitive HCT-116 colorectal cells, all these effects are consequence of the interaction of elisidepsin with glycosylceramides in the cell membrane. Of note, an elisidepsin-resistant subline (HCT-116-Irv) presented reduced levels of glycosylceramides and no accumulation of elisidepsin in the plasma membrane. Consequently, drug treatment did not induce the characteristic necrotic cell death. Furthermore, GM95, a mutant derivative from B16 mouse melanoma cells lacking ceramide glucosyltransferase (UGCG) activity and thus the synthesis of glycosylceramides, was also resistant to elisidepsin. Over-expression of UGCG gene in these deficient cells restored glycosylceramides synthesis, rendering them sensitive to elisidepsin, at a similar level than parental B16 cells. These results indicate that glycosylceramides act as membrane targets of elisidepsin, facilitating its insertion in the plasma membrane and the subsequent membrane permeabilization that leads to drug-induced cell death. They also indicate that cell membrane lipids are a plausible target for antineoplastic therapy.

Reducing GBA2 Activity Ameliorates Neuropathology in Niemann-Pick Type C Mice

The enzyme glucocerebrosidase (GBA) hydrolyses glucosylceramide (GlcCer) in lysosomes. Markedly reduced GBA activity is associated with severe manifestations of Gaucher disease including neurological involvement. Mutations in the GBA gene have recently also been identified as major genetic risk factor for Parkinsonism. Disturbed metabolism of GlcCer may therefore play a role in neuropathology. Besides lysosomal GBA, cells also contain a non-lysosomal glucosylceramidase (GBA2). Given that the two β-glucosidases share substrates, we speculated that over-activity of GBA2 during severe GBA impairment might influence neuropathology. This hypothesis was studied in Niemann-Pick type C (Npc1^-/-) mice showing secondary deficiency in GBA in various tissues. Here we report that GBA2 activity is indeed increased in the brain of Npc1^-/- mice. We found that GBA2 is particularly abundant in Purkinje cells (PCs), one of the most affected neuronal populations in NPC disease. Inhibiting GBA2 in Npc1^-/- mice with a brain-permeable low nanomolar inhibitor significantly improved motor coordination and extended lifespan in the absence of correction in cholesterol and ganglioside abnormalities. This trend was recapitulated, although not to full extent, by introducing a genetic loss of GBA2 in Npc1^-/- mice. Our findings point to GBA2 activity as therapeutic target in NPC.

Accumulation of glucosylceramide in the absence of the beta-glucosidase GBA2 alters cytoskeletal dynamics

Glycosphingolipids are key elements of cellular membranes, thereby, controlling a variety of cellular functions. Accumulation of the simple glycosphingolipid glucosylceramide results in life-threatening lipid storage-diseases or in male infertility. How glucosylceramide regulates cellular processes is ill defined. Here, we reveal that glucosylceramide accumulation in GBA2 knockout-mice alters cytoskeletal dynamics due to a more ordered lipid organization in the plasma membrane. In dermal fibroblasts, accumulation of glucosylceramide augments actin polymerization and promotes microtubules persistence, resulting in a higher number of filopodia and lamellipodia and longer microtubules. Similar cytoskeletal defects were observed in male germ and Sertoli cells from GBA2 knockout-mice. In particular, the organization of F-actin structures in the ectoplasmic specialization and microtubules in the sperm manchette is affected. Thus, glucosylceramide regulates cytoskeletal dynamics, providing mechanistic insights into how glucosylceramide controls signaling pathways not only during sperm development, but also in other cell types.

During mammalian spermatogenesis, sperm with a head and a tail are formed from a round cell. This process is tightly regulated and involves the close interaction of somatic Sertoli cells and germ cells. Accumulation of the glycosphingolipid glucosylceramide in the absence of the beta-glucosidase GBA2 has been proposed to disturb sperm development, leading to morphological defects. However, the underlying mechanism is not known. Here, we demonstrate that accumulation of glucosylceramide in GBA2 knockout-mice controls the dynamics of the actin and microtubule cytoskeleton, which are crucial for sperm development. In particular, cytoskeletal structures at the interface between Sertoli and germ cells are disorganized, leading to malformation of the sperm head and a defect in acrosome formation. In summary, we provide mechanistic insights into how glucosylceramide controls cellular signaling and dysregulation of this essential glycosphingolipid leads to male infertility.

Substrate compositional variation with tissue/region and Gba1 mutations in mouse models--implications for Gaucher disease

Gaucher disease results from GBA1 mutations that lead to defective acid β-glucosidase (GCase) mediated cleavage of glucosylceramide (GC) and glucosylsphingosine as well as heterogeneous manifestations in the viscera and CNS. The mutation, tissue, and age-dependent accumulations of different GC species were characterized in mice with Gba1 missense mutations alone or in combination with isolated saposin C deficiency (C*). Gba1 heteroallelism for D409V and null alleles (9V/null) led to GC excesses primarily in the visceral tissues with preferential accumulations of lung GC24∶0, but not in liver, spleen, or brain. Age-dependent increases of different GC species were observed. The combined saposin C deficiency (C*) with V394L homozygosity (4L;C*) showed major GC18∶0 degradation defects in the brain, whereas the analogous mice with D409H homozygosity and C* (9H;C*) led to all GC species accumulating in visceral tissues. Glucosylsphingosine was poorly degraded in brain by V394L and D409H GCases and in visceral tissues by D409V GCase. The neonatal lethal N370S/N370S genotype had insignificant substrate accumulations in any tissue. These results demonstrate age, organ, and mutation-specific quantitative differences in GC species and glucosylsphingosine accumulations that can have influence in the tissue/regional expression of Gaucher disease phenotypes.

The roles of antiapoptotic sphingosine kinase-1 and glucosylceramide genes in drug induced cell death of MCF-7 breast cancer cells

PURPOSE

Sphingolipids are important signaling molecules mediating cell survival, proliferation, cell cycle regulation and apoptosis. Ceramide is the most vital sphingolipid which induces growth arrest, senescence, and apoptosis. In this study, we aimed to determine the roles of sphingosine kinase-1 (SK-1) and glucosylceramide synthase (GCS) genes in paclitaxel, doxorubicin, tamoxifen, cyclophosphamide and docetaxel induced apoptosis in human MCF-7 breast cancer cells.

METHODS

IC50 values (drug concentration inhibiting cell growth by 50%) of the anticancer agents were calculated using XTT cell proliferation assay. Changes in mitochondrial membrane potential (MMP) were determined using JC-1 assay kit. Changes in the mRNA levels of SK-1 and GCS genes were measured by using RT-PCR technique.

RESULTS

The results demonstrated significant decrease in cellular proliferation and increase in loss of MMP in a dose-dependent manner. Paclitaxel, doxorubicin, tamoxifen, cyclophosphamide and docetaxel application downregulated SK-1 expression while paclitaxel, tamoxifen, cyclophosphamide and docetaxel but not doxorubicin downregulated GCS comparing to untreated control cells.

CONCLUSION

These results show for the first time that these agents induce apoptosis in MCF-7 cells by downregulating the antiapoptotic SK-1 and GCS genes that may result in accumulation of apoptotic ceramides.

Velaglucerase alfa, a human recombinant glucocerebrosidase enzyme replacement therapy for type 1 Gaucher disease

Gaucher disease (GD) is caused by a deficiency of the lysosomal enzyme glucocerebrosidase, which results in the accumulation of its substrate, glucocerebroside, in macrophages. This excess in lipid storage within macrophages (subsequently recognized as Gaucher cells) leads to the development of disease, which presents clinical features including anemia, thrombocytopenia and hepatosplenomegaly, and can also lead to the development of neurological problems or bone disease. Velaglucerase alfa is a gene-activated human recombinant glucocerebrosidase being developed by Shire Human Genetic Therapies Inc as an enzyme replacement therapy for type 1 GD. In vitro, velaglucerase alfa was internalized by human macrophages more rapidly than imiglucerase, which has been the sole standard of care for GD for over 15 years. Clinical trials in patients with GD demonstrated that the safety and efficacy of velaglucerase alfa appeared to be comparable with historical imiglucerase data, although head-to-head data were unavailable. Recent problems with the production of imiglucerase led to the unanticipated introduction of velaglucerase alfa to patients with GD through a pre-approval expanded access protocol. Whether this will prove beneficial, in terms of uptake and prescribing of the enzyme, remains to be seen in a market dominated by imiglucerase.

Characterization of Gaucher disease bone marrow mesenchymal stromal cells reveals an altered inflammatory secretome

Gaucher disease causes pathologic skeletal changes that are not fully explained. Considering the important role of mesenchymal stromal cells (MSCs) in bone structural development and maintenance, we analyzed the cellular biochemistry of MSCs from an adult patient with Gaucher disease type 1 (N370S/L444P mutations). Gaucher MSCs possessed a low glucocerebrosidase activity and consequently had a 3-fold increase in cellular glucosylceramide. Gaucher MSCs have a typical MSC marker phenotype, normal osteocytic and adipocytic differentiation, growth, exogenous lactosylceramide trafficking, cholesterol content, lysosomal morphology, and total lysosomal content, and a marked increase in COX-2, prostaglandin E2, interleukin-8, and CCL2 production compared with normal controls. Transcriptome analysis on normal MSCs treated with the glucocerebrosidase inhibitor conduritol B epoxide showed an up-regulation of an array of inflammatory mediators, including CCL2, and other differentially regulated pathways. These cells also showed a decrease in sphingosine-1-phosphate. In conclusion, Gaucher disease MSCs display an altered secretome that could contribute to skeletal disease and immune disease manifestations in a manner distinct and additive to Gaucher macrophages themselves.

Depletion of alveolar macrophages decreases the dissemination of a glucosylceramide-deficient mutant of Cryptococcus neoformans in immunodeficient mice

In previous studies we showed that a Cryptococcus neoformans mutant lacking glucosylceramide (Deltagcs1) is avirulent and unable to reach the brain when it is administered intranasally into an immunocompetent mouse and is contained in a lung granuloma. To determine whether granuloma formation is key for containment of C. neoformans Deltagcs1, we studied the role of C. neoformans glucosylceramide in a T- and NK-cell-immunodeficient mouse model (Tgepsilon26) in which alveolar macrophages (AMs) are not activated and granuloma formation is not expected. The results show that Tgepsilon26 mice infected with Deltagcs1 do not produce a lung granuloma and that the Deltagcs1 mutant proliferates in the lungs and does disseminate to the brain, although its virulence phenotype is dramatically reduced. Since Deltagcs1 can grow only in acidic niches, such as the phagolysosome of AMs, and not in neutral or alkaline environments, such as the extracellular spaces, we hypothesize that in immunodeficient mice Deltagcs1 proliferates inside AMs. Indeed, we found that depletion of AMs significantly improved Tgepsilon26 mouse survival and decreased the dissemination of Deltagcs1 cells to the central nervous system. Thus, these results suggest that the growth of Deltagcs1 in immunodeficient mice is maintained within AMs. This study highlights the hypothesis that AMs may exacerbate C. neoformans infection in conditions in which there is severe host immunodeficiency.

Therapeutic strategies to ameliorate lysosomal storage disorders – a focus on Gaucher disease

The lysosomal storage disorders encompass more than 40 distinct diseases, most of which are caused by the deficient activity of a lysosomal hydrolase leading to the progressive, intralysosomal accumulation of substrates such as sphingolipids, mucopolysaccharides, and oligosaccharides. Here, we primarily focus on Gaucher disease, one of the most prevalent lysosomal storage disorders, which is caused by an impaired activity of glucocerebrosidase, resulting in the accumulation of the glycosphingolipid glucosylceramide in the lysosomes. Enzyme replacement and substrate reduction therapies have proven effective for Gaucher disease cases without central nervous system involvement. We discuss the promise of chemical chaperone therapy to complement established therapeutic strategies for Gaucher disease. Chemical chaperones are small molecules that bind to the active site of glucocerebrosidase variants stabilizing their three-dimensional structure in the endoplasmic reticulum, likely preventing their endoplasmic reticulum-associated degradation and allowing their proper trafficking to the lysosome where they can degrade accumulated substrate to effectively ameliorate Gaucher disease.

Presence of glucosylceramide in yeast and its relation to alkali tolerance of yeast

Glycosylceramide is a membrane lipid that has physiological functions in eukaryotic organisms. The presence of glucosylceramide has been confirmed in some yeast; however, the extent of the role of glucosylceramide in yeast is unknown. Thus, the extent of presence of glucosylceramide in yeast was surveyed using 90 strains of 24 genera. The strains were divided into two groups according to whether they had glucosylceramide (45 strains) or not (45 strains). The distribution of the ceramide glucosyltransferase gene (EC 2.4.1.80), which catalyzes glucosylation to a sphingoid lipid in glucosylceramide synthesis, and the phylogenetic classification of the strains were in agreement with those of glucosylceramide. Thus, the presence of glucosylceramide in yeast was caused by the presence of the gene involved in glucosylceramide synthesis and was closely associated with yeast evolution. Furthermore, the relationship between glucosylceramide presence and alkali tolerance of yeast was evaluated. The yeast with glucosylceramide tended to grow at higher pH, and a ceramide-glucosyltransferase-defective mutant from Kluyveromyces lactis did not grow at pH 8.5 even though the parent strain could grow under the same conditions. These results indicate that glucosylceramide in yeast might be a component that enables yeast to grow under alkali conditions.

Defensins from insects and plants interact with fungal glucosylceramides

Growth of the yeast species Candida albicans and Pichia pastoris is inhibited by RsAFP2, a plant defensin isolated from radish seed (Raphanus sativus), at micromolar concentrations. In contrast, gcs-deletion mutants of both yeast species are resistant toward RsAFP2. GCS genes encode UDP-glucose:ceramide glucosyltransferases, which catalyze the final step in the biosynthesis of the membrane lipid glucosylceramide. In an enzyme-linked immunosorbent assay-based binding assay, RsAFP2 was found to interact with glucosylceramides isolated from P. pastoris but not with soybean nor human glucosylceramides. Furthermore, the P. pastoris parental strain is sensitive toward RsAFP2-induced membrane permeabilization, whereas the corresponding gcs-deletion mutant is highly resistant to RsAFP2-mediated membrane permeabilization. A model for the mode of action of RsAFP2 is presented in which all of these findings are linked. Similarly to RsAFP2, heliomicin, a defensin-like peptide from the insect Heliothis virescens, is active on C. albicans and P. pastoris parental strains but displays no activity on the gcs-deletion mutants of both yeast species. Furthermore, heliomicin interacts with glucosylceramides isolated from P. pastoris and soybean but not with human glucosylceramides. These data indicate that structurally homologous anti-fungal peptides present in species from different eukaryotic kingdoms interact with the same target in the fungal plasma membrane, namely glucosylceramides, and as such support the hypothesis that defensins from plants and insects have evolved from a single precursor.

Recently discovered functions of glucosylceramides in plants and fungi

Glycosphingolipids are ubiquitous membrane lipids of eukaryotic organisms and a few bacteria. Whereas inositol-containing glycosphingolipids are restricted to plants and fungi, galactosylceramide occurs only in fungi and animals. In contrast, glucosylceramide is the unique glycosphingolipid which plants, fungi and animals have in common. However, there are specific differences in the structure of the ceramide backbone of glucosylceramides from these organisms. A comparison of the structural features and the biosynthesis of glucosylceramides from plants, fungi and animals will contribute to our understanding of their functions, which so far have been analysed mainly in animals. The availability of nearly all genes involved in the biosynthesis of glucosylceramides enables the specific manipulation of glycosphingolipid metabolism by techniques of forward and reverse genetics. Application of this approach to unicellular organisms like yeasts, multicellular filamentous fungi, as well as to complex organisms like plants will reveal common and different glucosylceramide functions in these organisms. These glycolipids play a role both in intracellular processes and in cell-to-cell interactions. These interactions may occur between cells of a multicellular organism or between cells of different species, as in host-pathogen interactions.

Enzymatic and molecular diagnosis of Gaucher disease

Advances in the knowledge of the molecular genetics of Gaucher disease has made diagnosis more certain. Carrier detection in kindreds in which the responsible mutation has been defined is completely reliable now. Coupled with enzymatic assays, the diagnostic capabilities are greater than before. Use of these methods provides important information to individuals at risk and allows them to make critical decisions. The new, simplified methods reviewed in this article permit the molecular diagnosis of the disease and carrier stage of large numbers of samples within 1 week.

Phylogenetic dichotomy of nerve glycosphingolipids

Galactocerebrosides and sulfatides are major characteristic components of vertebrate myelin. In contrast, glucocerebroside is the major glycosphingolipid of shrimp nerve. In this study, the concentrations of these glycosphingolipids in the nervous systems of animals from several evolutionary branches were determined by use of high-performance liquid chromatography. In nerves of protostome animals only glucose-containing glycosphingolipids were detected, whereas glycosphingolipids from deuterostomes contained predominantly galactose. Neither the glycolipids containing alpha-hydroxy fatty acids nor sulfate esters of the glycolipids, both of which always accompany galactocerebrosides in deuterostome myelin, were present in protostome nerves. This correlation suggests an evolutionary trend from gluco- to galactocerebrosides, which corresponds with changes in the nervous system from loosely structured membrane-enwrapped axons to multilamellar highly structured myelin.