Hiromu Takematsu

The first step in influenza virus infection is the binding of hemagglutinin to sialic acid-containing glycans present on the cell surface. Over 50 different sialic acid modifications are known, of which N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc) are the two main species. Animal models with α2,6 linked Neu5Ac in the upper respiratory tract, similar to humans, are preferred to enable and mimic infection with unadapted human influenza A viruses. Animal models that are currently most often used to study human influenza are mice and ferrets. Additionally, guinea pigs, cotton rats, Syrian hamsters, tree shrews, domestic swine, and non-human primates (macaques and marmosets) are discussed. The presence of NeuGc and the distribution of sialic acid linkages in the most commonly used models is summarized and experimentally determined. We also evaluated the role of Neu5Gc in infection using Neu5Gc binding viruses and cytidine monophosphate-N-acetylneuraminic acid hydroxylase (CMAH)−/− knockout mice, which lack Neu5Gc and concluded that Neu5Gc is unlikely to be a decoy receptor. This article provides a base for choosing an appropriate animal model. Although mice are one of the most favored models, they are hardly naturally susceptible to infection with human influenza viruses, possibly because they express mainly α2,3 linked sialic acids with both Neu5Ac and Neu5Gc modifications. We suggest using ferrets, which resemble humans closely in the sialic acid content, both in the linkages and the lack of Neu5Gc, lung organization, susceptibility, and disease pathogenesis.

Background: The human natural killer-1 (HNK-1) carbohydrate, a unique trisaccharide possessing sulfated glucuronic acid in a non-reducing terminus (HSO3-3G1cA beta 1-3Galf beta-4G1cNAc-), is highly expressed in the nervous system and its spatiotemporal expression is strictly regulated. Mice deficient in the gene encoding a key enzyme, GIcAT-P, of the HNK-1 biosynthetic pathway exhibit almost complete disappearance of the HNK-1 epitope in the brain, significant reduction of long-term potentiation, and aberration of spatial learning and memory formation. In addition to its physiological roles in higher brain function, the HNK-1 carbohydrate has attracted considerable attention as an autoantigen associated with peripheral demyelinative neuropathy, which relates to IgM paraproteinemia, because of high immunogenicity. It has been suggested, however, that serum autoantibodies in IgM anti-myelin-associated glycoprotein (MAG) antibody-associated neuropathy patients show heterogeneous reactivity to the HNK-1 epitope. Scope of review: We have found that structurally distinct HNK-1 epitopes are expressed in specific proteins in the nervous system. Here, we overview the current knowledge of the involvement of these HNK-1 epitopes in the regulation of neural plasticity and discuss the impact of different HNK-1 antigens of anti-MAG neuropathy patients. Major conclusions: We identified the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptor subunit GluA2 and aggrecan as HNK-1 carrier proteins. The HNK-1 epitope on GluA2 and aggrecan regulates neural plasticity in different ways. Furthermore, we found the clinical relationship between reactivity of autoantibodies to the different HNK-1 epitopes and progression of anti-MAG neuropathy. General significance: The HNK-1 epitope is indispensable for the acquisition of normal neuronal function and can be a good target for the establishment of diagnostic criteria for anti-MAG neuropathy.

Remodeling of glycans on the cell surface is an essential technique to analyze cellular function of lectin-glycan ligand interaction. Here we describe the methods to identify the responsible enzyme (glycosyltransferase) regulating the expression of the glycan of interest and to modulate the glycan expression by overexpressing the glycosyltransferase gene. For the identification of the responsible enzyme, we introduce a new method, CIRES (correlation index-based responsible-enzyme gene screening), that consists of statistical comparison of glycan expression profile obtained by flow cytometry and gene expression profile obtained by DNA microarray. © 2014 Springer Science+Business Media New York.

糖脂質の発現制御の解析には多数の遺伝子を網羅的に解析可能なDNAマイクロアレイによる解析が非常に有用である。当研究室で、糖・脂質関連酵素を中心にしたDNAマイクロアレイを作成し、多くのサンプルについて糖脂質関連遺伝子の発現パターンの解析を行ってきた。今回、DNAマイクロアレイの新たな解析方法論の開発を試み、糖脂質の発現制御に関わる候補遺伝子を確からしさの順位とともに提示できるシステムを開発した。(著者抄録)

In this review, we focus on sphingolipids as potential regulators of the induction of multinuclear cell formation through the inhibition of cytokinesis. A sphingolipid, psychosine (Psy) (galactosylsphingosine), was demonstrated to be a trigger lipid for the inhibition of cytokinesis and the induction of multinuclear giant cells associated with a sphingolipid metabolic disease, globoid cell leukodystrophy (GLD). Indeed, Psy is known to accumulate in the patients' brains. Interestingly, inhibition of sphingolipid biosynthesis also induced multinuclear cells. When cells were treated with a new immunosuppressant, ISP-1/myriocin, which inhibits serine palmitoyltransferase, the first step enzyme of sphingolipid biosynthesis, the cells underwent multinucleation and apoptosis. At present, a definitive model of the function of sphingolipids as to the induction of multinuclear cell formation is not available due to the rudimentary information but possible mechanisms are discussed. (C) 2002 Elsevier Science B.V. All rights reserved.