Toshio Ariga

Developmental changes of glycosphingolipids and expression of glycogenes in mouse brains

Glycosphingolipids (GSLs) and their sialic acid‐containing derivatives, gangliosides, are important cellular components and are abundant in the nervous system. They are known to undergo dramatic changes during brain development. However, knowledge on the mechanisms underlying their qualitative and qualitative changes is still fragmentary. In this investigation, we have provided a detailed study on the developmental changes of the expression patterns of GSLs, GM3, GM1, GD3, GD1a, GD2, GD1b, GT1b, GQ1b, A2B5 antigens (c‐series gangliosides such as GT3 and GQ1c), Chol‐1α (GT1aα and GQ1bα), glucosylceramide, galactosylceramide (O1 antigen), sulfatide (O4 antigen), stage‐specific embryonic antigen‐1 (Lewis x) glycolipids, and human natural killer‐1 glycolipid (sulfoglucuronosyl paragloboside) in developing mouse brains [embryonic day 12 (E12) to adult]. In E12–E14 brains, GD3 was a predominant ganglioside. After E16, the concentrations of GD3 and GM3 markedly decreased, and the concentrations of a‐series gangliosides, such as GD1a, increased. GT3, glucosylceramide, and stage‐specific embryonic antigen‐1 were expressed in embryonic brains. Human natural killer‐1 glycolipid was expressed transiently in embryonic brains. On the other hand, Chol‐1α, galactosylceramide, and sulfatide were exclusively found after birth. To provide a better understanding of the metabolic basis for these changes, we analyzed glycogene expression patterns in the developing brains and found that GSL expression is regulated primarily by glycosyltransferases, and not by glycosidases. In parallel studies using primary neural precursor cells in culture as a tool for studying developmental events, dramatic changes in ganglioside and glycosyltransferase gene expression were also detected in neurons induced to differentiate from neural precursor cells, including the expression of GD3, followed by up‐regulation of complex a‐ and b‐series gangliosides. These changes in cell culture systems resemble that occurring in brain. We conclude that the dramatic changes in GSL pattern and content can serve as useful markers in neural development and that these changes are regulated primarily at the level of glycosyltransferase gene expression.

Functional roles of gangliosides in neurodevelopment: an overview of recent advances.

Gangliosides are sialic acid-containing glycosphingolipids that are most abundant in the nervous system. They are localized primarily in the outer leaflets of plasma membranes and participated in cell–cell recognition, adhesion, and signal transduction and are integral components of cell surface microdomains or lipid rafts along with proteins, sphingomyelin and cholesterol. Ganglioside-rich lipid rafts play an important role in signaling events affecting neural development and the pathogenesis of certain diseases. Disruption of gangloside synthase genes in mice induces developmental defects and neural degeneration. Targeting ganglioside metabolism may represent a novel therapeutic strategy for intervention in certain diseases. In this review, we focus on recent advances on metabolic and functional studies of gangliosides in normal brain development and in certain neurological disorders.

Ganglioside Molecular Mimicry and Its Pathological Roles in Guillain-Barré Syndrome and Related Diseases

Guillain-Barre syndrome (GBS) is the most frequent cause of acute flaccid paralysis in humans, occurring with an annual incidence of 1 to 2 cases per 100,000 people. In recent years, studies have shed new light on a number of disease aspects that have enhanced the understanding of the pathogenic

Abnormality of Long-Chain Fatty Acids in Erythrocyte Membrane Sphingomyelin from Patients with Adrenoleukodystrophy

Abstract: We have devised an analytical method for the determination of fatty acid composition of erythrocyte membrane sphingomyelin by chemical ionization mass spectrometry combined with capillary column gas‐liquid chromatography. Fatty acid composition of erythrocyte membrane sphingomyelin from 8 patients with adrenoleukodystrophy (ALD) and 16 healthy controls were examined by this method. The ratio of hexacosanoic acid (C26.0) to docosanoic acid (C22:0) in erythrocyte membrane sphingomyelin from ALD patients was 2.6‐fold higher than that of the controls. This result suggests that biochemical diagnosis of ALD is possible by the analysis of fatty acid composition of erythrocyte membrane sphingomyelin. Furthermore, it demonstrates that biochemical abnormality in ALD is the generalized abnormal metabolism of very long‐chain saturated fatty acids.

The neuropathy of plasma cell dyscrasia Binding of IgM M‐proteins to peripheral nerve glycolipids

In some patients with neuropathy and plasma cell dyscrasia, the M-proteins bind to peripheral nerves. Binding of M-proteins to peripheral nerve glycolipids was examined by immunostaining after thin-layer chromatography. The IgM from 16 patients with anti-MAG M-proteins bound to the same two glycolipid bands in peripheral nerve. The IgM that bound to the glycolipids had the same idiotype as the anti-MAG M-protein, indicating that it was the M-protein that bound to both glycolipids. The reactive glycolipids did not contain sialic acid and were not gangliosides. No immunostaining of peripheral nerve glycolipids was observed with IgM from patients with neuropathy and IgM M-proteins that did not bind to MAG, and the anti-MAG antibodies did not bind to brain glycolipids. Anti-MAG M-proteins probably bind to the same or closely related carbohydrate determinants that are shared by a number of glycoproteins and glycolipids of peripheral nerve.

Thermotropic behavior of binary mixtures of diplamitoylphosphatidylcholine and glycosphingolipids in aqueous dispersions

The thermotropic behavior of mixtures of dipalmitoylphosphatidylcholine (DPPC) with natural glycosphingolipids (galactosylceramide, phrenosine, kerasine, glucosylceramide, lactosylceramide, asialo-GM1, sulfatide, GM3, GM1, GD1a, GT1b) in dilute aqueous dispersions were studied by high sensitivity differential scanning calorimetry over the entire composition range. The pretransition of DPPC is abolished and the cooperativity of the main transition decreases sharply at mole fractions of glycosphingolipids below 0.2. All systems exhibit non-ideal temperature-composition phase diagrams. The mono- and di-hexosylceramides are easily miscible with DPPC when the proportion of glycosphingolipids in the system is high. A limited quantity (1-6 molecules of DPPC per molecule of glycosphingolipid (GSL) can be incorporated into a homogeneously mixed lipid phase. Domains of DPPC, immiscible with the rest of a mixed GSL-DPPC phase that shows no cooperative phase transition, are established as DPPC exceeds a certain proportion in the system. One negative charge (sulfatide) or four neutral carbohydrate residues (asialo-GM1) in the oligosaccharide chain of the glycosphingolipids results in phase diagrams exhibiting coexistence of gel and liquid phases over a broad temperature-composition range. Systems containing gangliosides show complex phase diagrams, with more than one phase transition. However, no evidence for phase-separated domains of pure ganglioside species is found. The thermotropic behavior of systems containing DPPC and glycosphingolipids correlates well with their interactions in mixed monolayers at the air/water interface.

Antiganglioside antibodies and their pathophysiological effects on Guillain-Barré syndrome and related disorders - a review.

Guillain-Barré syndrome (GBS) is an acute immune-mediated polyradiculoneuropathy which can cause acute quadriplegia. Infection with micro-organisms, including Campylobacter jejuni (C. jejuni), Haemophilus influenzae, and Cytomegalovirus (CMV), is recognized as a main triggering event for the disease. Lipooligosaccharide (LOS) genes are responsible for the formation of human ganglioside-like LOS structures in infectious micro-organisms that can induce GBS. Molecular mimicry of LOSs on the surface of infectious agents and of ganglioside antigens on neural cells is thought to induce cross-reactive humoral and cellular immune responses. Patients with GBS develop antibodies against those gangliosides, resulting in autoimmune targeting of peripheral nerve sites, leading to neural damage. Heterogeneity of ganglioside expression in the peripheral nervous system (PNS) may underlie the differential clinical manifestation of the GBS variants. Recent studies demonstrate that some GBS sera react with ganglioside complexes consisting of two different gangliosides, such as GD1a and GD1b, or GM1 and GD1a, but not with each constituent ganglioside alone. The discovery of antiganglioside complex antibodies not only improves the detection rate of autoantibodies in GBS, but also provides a new concept in the antibody-antigen interaction through clustered carbohydrate epitopes. Although ganglioside mimicry is one of the possible etiological causes of GBS, unidentified factors may also contribute to the pathogenesis of GBS. While GBS is not considered a genetic disease, host factors, particularly human lymphocyte antigen type, appear to have a role in the pathogenesis of GBS following C. jejuni infection.

Is IgG anti-GT1a antibody associated with pharyngeal–cervical–brachial weakness or oropharyngeal palsy in Guillain–Barré syndrome?

The pharyngeal-cervical-brachial variant (PCB) of Guillain-Barré syndrome (GBS) has clinical features similar to those of botulism and diphtheria. Mizoguchi et al. (1994) [Mizoguchi, K., Hase, A., Obi, T., Matsuoka, H., Takatsu, M., Nishimura, Y., Irie, F., Seyama, Y., Hirabayashi, Y., 1994. Two species of antiganglioside antibodies in a patient with a pharyngeal-cervical-brachial variant of Guillain-Barré syndrome. J. Neurol. Neurosurg. Psychiatry 57, 1121-1123] reported a patient with PCB-like symptoms who had serum IgG anti-GT1a antibodies which did not cross-react with GQ1b. We assumed that PCB is associated with anti-GT1a antibodies that do not have reactivity to GQ1b and made a serological study of a PCB patient. We searched for PCB patients prospectively and found one with PCB. This patient had IgG anti-GT1a antibodies which were not absorbed with GQ1b in an absorption study, whereas IgG anti-GT1a antibodies from Fishers syndrome patients were. The frequency of positive IgG anti-GT1a antibody did not differ in patients with and without bulbar palsy. Our findings indicate that IgG anti-GT1a antibodies which do not cross-react with GQ1b are specifically detectable in PCB and can be used as a diagnostic marker of PCB.

Role of proteoglycans and glycosaminoglycans in the pathogenesis of Alzheimer's disease and related disorders: Amyloidogenesis and therapeutic strategies—A review

The extracellular accumulation of amyloid β proteins (Aβs) in neuritic plaques is one of the hallmarks of Alzheimers disease (AD). The binding of Aβs to extracellular membranes (ECMs) is a critical step in developing AD. Aβs bind to many biomolecules, including lipids, proteins, and proteoglycans (PGs). PGs play several roles in amyloid formation, including promoting the aggregation of Aβs into insoluble amyloid fibrils, which contributes to the increased neurotoxicity of Aβs. Although Aβs readily self‐aggregate to form amyloid fibrils in vitro, their binding to PGs and heparin enhances amyloid aggregation and fibril formation. The sulfate moiety in glycosaminoglycans (GAGs), the carbohydrate portion of PGs, is necessary for the formation of amyloid fibrils; no fibrils are observed in the presence of hyaluronic acid (HA), a nonsulfated GAG. PGs and Aβs are known to colocalize in senile plaques (SPs) and neurofibrillary tangles (NFTs) in the AD brain. The binding site of PGs to Aβs has been identified in the 13–16‐amino‐acid region (His‐His‐Gln‐Lys) of Aβs and represents a unique target site for inhibition of amyloid fibril formation; His13 in particular is an important residue critical for interaction with GAGs. The sulfate moieties of GAGs play a critical role in the binding to Aβs and enhance Aβ fibril formation. Low‐molecular‐weight heparins (LMWHs) can reverse the process of amyloidosis to inhibit fibril formation by blocking the formation of β‐plated structures, suggesting a possible therapeutic approach using LMWHs to interfere with the interaction between PGs and Aβs and to arrest or prevent amyloidogenesis.

Characterization of glycoconjugate antigens in mouse embryonic neural precursor cells

Neuronal and glial cells organizing the central nervous system (CNS) are generated from common neural precursor cells (NPCs) during neural development. However, the expression of cell‐surface glycoconjugates that are crucial for determining the properties and biological function of these cells at different stages of development has not been clearly defined. In this study, we investigated the expression of several stage‐specific glycoconjugate antigens, including several b‐series gangliosides GD3, 9‐O‐acetyl GD3, GT1b and GQ1b, stage‐specific embryonic antigen‐1 (SSEA‐1) and HNK‐1, in mouse embryonic NPCs employing immunocytochemistry and flow cytometry. In addition, several of these antigens were positively identified by chemical means for the first time. We further showed that the SSEA‐1 immunoreactivity was contributed by both glycoprotein and glycolipid antigens, and that of HNK‐1 was contributed only by glycoproteins. Functionally, SSEA‐1 may participate in migration of the cells from neurospheres in an NPC cell culture system, and the effect could be repressed by anti‐SSEA‐1 antibody. Based on this observation, we identified β1 integrin as one of the SSEA‐1 carrier glycoproteins. Our data thus provide insights into the functional role of certain glycoconjugate antigens in NPCs during neural development.