Faculty Profiles - SATO, Chihiro

Mental disorders and an acidic glycan-from the perspective of polysialic acid (PSA/polySia) and the synthesizing enzyme, ST8SIA2. Reviewed

Sato C, Hane M

Glycoconjugate journal Vol. 35 ( 4 ) page： 353 - 373 2018.8

酸性糖鎖ポリシアル酸の新機能の発見とその応用展開 Reviewed

佐藤ちひろ

化学と生物 Vol. 56 page： 422 - 431 2018

Positive selection on schizophrenia-associated ST8SIA2 gene in post-glacial Asia. Reviewed Open Access

Fujito NT, Satta Y, Hane M, Matsui A, Yashima K, Kitajima K, Sato C, Takahata N, Hayakawa T

PloS one Vol. 13 ( 7 ) page： e0200278 2018

Language：English Publishing type：Research paper (scientific journal) Publisher：PUBLIC LIBRARY SCIENCE

A number of loci are associated with highly heritable schizophrenia and the prevalence of this mental illness has had considerable negative fitness effects on human populations. Here we focused on one particular schizophrenia-associated gene that encodes a sialyl-transferase (ST8SIA2) and is expressed preferentially in the brain with the level being largely determined by three SNPs in the promoter region. It is suggested that the expression level of the ST8SIA2 gene is a genetic determinant of schizophrenia risk, and we found that a geographically differentiated non-risk SNP type (CGC-type) has significantly reduced promoter activity. A newly developed method for detecting ongoing positive selection was applied to the ST8SIA2 genomic region with the identification of an unambiguous sweep signal in a rather restricted region of 18 kb length surrounding the promoter. We also found that while the CGC-type emerged in anatomically modern humans in Africa over 100 thousand years ago, it has increased its frequency in Asia only during the past 20-30 thousand years. These findings support that the positive selection is driven by psychosocial stress due to changing social environments since around the last glacial maximum, and raise a possibility that schizophrenia extensively emerged during the Upper Paleolithic and Neolithic era.

DOI： 10.1371/journal.pone.0200278

Different properties of polysialic acids synthesized by the polysialyltransferases ST8SIA2 and ST8SIA4

Airi Mori, Masaya Hane, Yuki Niimi, Ken Kitajima, Chihiro Sato

GLYCOBIOLOGY Vol. 27 ( 9 ) page： 834 - 846 2017.9

Language：English Publishing type：Research paper (scientific journal) Publisher：OXFORD UNIV PRESS INC

Polysialic acid (polySia) is mainly found as a modification of neural cell adhesion molecule (NCAM) in whole embryonic brains, as well as restricted areas of adult vertebrate brains, including the hippocampus. PolySia shows not only repulsive effects on NCAM-involved cell-cell interactions due to its bulky and hydrated properties, but also attractive effects on the interaction with neurologically active molecules, which exerts a reservoir function. Two different polysialyltransferases, ST8SIA2 and ST8SIA4, are involved in the synthesis of polySia chains; however, to date, the differences of the properties between polySia chains synthesized by these two enzymes remain unknown. In this study, to clarify this point, we first prepared polySia-NCAMs from HEK293 cells stably expressing ST8SIA4 and ST8SIA2, or ST8SIA2 (SNP-7), a mutant ST8SIA2 derived from a schizophrenia patient. The conventional sensitive chemical and immunological characterizations showed that the quantity and quality (structural features) of polySia are not so much different between ST8SIA4-and ST8SIA2-synthesized ones, apart from those of ST8SIA2 (SNP-7). Then, we assessed the homophilic and heterophilic interactions mediated by polySia-NCAM by adopting a surface plasmon resonance measurement as an in vitro analytical method. Our novel findings are as follows: (i) the ST8SIA2-and ST8SIA4-synthesized polySia-NCAMs exhibited different attractive and repulsive effects than each other; (ii) both polySia-and oligoSia-NCAMs synthesized by ST8SIA2 were able to bind polySia-NCAMs; (iii) the polySia-NCAM synthesized by a ST8SIA2 (SNP-7) showed markedly altered attractive and repulsive properties. Collectively, polySia-NCAM is suggested to simultaneously possess both attractive and repulsive properties that are highly regulated by the two polysialyltransferases.

DOI： 10.1093/glycob/cwx057

Chemical Synthesis and Evaluation of a Disialic Acid-Containing Dextran Polymer as an Inhibitor for the Interaction between Siglec 7 and Its Ligand

Sho Yamaguchi, Atsushi Yoshimura, Yu Yasuda, Airi Mori, Hiroshi Tanaka, Takashi Takahashi, Ken Kitajima, Chihiro Sato

CHEMBIOCHEM Vol. 18 ( 13 ) page： 1194 - 1203 2017.7

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

A new sialic acid (Sia)-containing glycopolymer-a fluorescent probe with high-density disialic acid (diSia) on the surface of polysaccharide dextran (diSia-Dex)-was synthesized as a key molecule to regulate the Sia recognition lectins, Siglecs, that are involved in the immune system. According to our original methods, diSia was synthesized by alpha-selective sialylation, and a dextran template possessing terminal acetylenes and amino groups was prepared. A diSia and a fluorescent molecule were subsequently introduced to surface-modified dextran by Huisgen reaction and amidation, respectively. The modulatory activity of Siglec7 was evaluated by using synthetic probes. DiSia-Dex showed high binding avidity toward Siglec7, with a KD value of 5.87 x 10(-10) M, and a high inhibitory activity for the interaction between Siglec7 and a ligand (GD3), with a IC50 value of 1.0 nM. Notably, diSia-Dex was able to release Siglec7 from the pre-existing Siglec7-GD3 complex, possibly due to its unique properties of a slow dissociation rate and a high association rate. Together, these data show that diSia-Dex can be widely applicable as a modulator of Siglec7 functions.

DOI： 10.1002/cbic.201600694

Alpha-2 macroglobulin as a region-specific secretory protein in male reproductive tract, and its dynamics during sperm transit toward the female spermatheca in the blue crab

Thanyaporn Senarai, Rapeepun Vanichviriyakit, Shinji Miyata, Chihiro Sato, Prapee Sretarugsa, Wattana Weerachatyanukul, Ken Kitajima

MOLECULAR REPRODUCTION AND DEVELOPMENT Vol. 84 ( 7 ) page： 585 - 595 2017.7

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY

A 250-kDa protein was isolated from fluid in the middle spermatic duct (MSD) of the blue crab (Portunus pelagicus). N-terminal and partial amino acid sequences revealed that this MSD-specific protein is highly similar to the plasma-enriched protein Alpha-2 macroglobulin (alpha 2M). The P. pelagicus ortholog (Pp alpha 2M) is a large glycoprotein possessing mannose and N-acetylglucosamine residues. Pp alpha 2M mRNA was detected in the spermatic duct, androgenic gland, and hematopoietic tissue, whereas the protein was primarily observed in the apical cytoplasm of MSD epithelium and in the matrix of the acrosome of MSD sperm; distally within spermatic duct, Pp alpha 2M was lost from the sperm membrane but remained in the sperm acrosome. These results suggest that Pp alpha 2M is expressed and glycosylated in the epithelium of spermatic ducts, secreted into MSD fluid, taken up by sperm in the MSD, and removed from the surface of sperm during its transit towards the female spermatheca. Given that Pp alpha 2M also exhibits protease inhibitor activity, we hypothesize that acrosome localized Pp alpha 2M may suppress premature acrosome reaction during post-testicular sperm maturation in this crab.

DOI： 10.1002/mrd.22817

Chlorpromazine Increases the Expression of Polysialic Acid (PolySia) in Human Neuroblastoma Cells and Mouse Prefrontal Cortex

Chikara Abe, Saki Nishimura, Airi Mori, Yuki Niimi, Yi Yang, Masaya Hane, Ken Kitajima, Chihiro Sato

INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol. 18 ( 6 ) 2017.5

Language：English Publishing type：Research paper (scientific journal) Publisher：MDPI AG

The neural cell adhesion molecule (NCAM) is modified by polysialic acid (polySia or PSA) in embryonic brains. In adult brains, polySia modification of NCAM is only observed in restricted areas where neural plasticity, remodeling of neural connections, or neural generation is ongoing although the amount of NCAM remains unchanged. Impairments of the polySia-expression and several single nucleotide polymorphisms (SNPs) of the polysialyltransferase (polyST) ST8SIA2 gene are reported to be associated with schizophrenia and bipolar disorder. Chlorpromazine (CPZ) is well-known as an agent for treating schizophrenia, and our hypothesis is that CPZ may affect the polySia expression or the gene expression of polySTs or NCAM. To test this hypothesis, we analyzed the effects of CPZ on the expression of polySia-NCAM on human neuroblastoma cell line, IMR-32 cells, by immunochemical and chemical methods. Interestingly, the cell surface expression of polySia, especially those with lower chain lengths, was significantly increased on the CPZ-treated cells, while mRNAs for polySTs and NCAM, and the amounts of total polySia-NCAM remained unchanged. The addition of brefeldin A, an inhibitor of endocytosis, suppressed the CPZ-induced cell surface polySia expression. In addition, polySia-NCAM was also observed in the vesicle compartment inside the cell. All these data suggest that the level of cell surface expression of polySia in IMR-32 is highly regulated and that CPZ changes the rate of the recycling of polySia-NCAM, leading to the up-regulation of polySia-NCAM on the cell surface. We also analyzed the effect of CPZ on polySia-expression in various brain regions in adult mice and found that CPZ only influenced the total amounts of polySia-NCAM in prefrontal cortex. These results suggest a brain-region-specific effect of CPZ on the expression of total polySia in mouse brain. Collectively, anti-schizophrenia agent CPZ consistently up-regulates the expression polySia at both cellular and animal levels.

DOI： 10.3390/ijms18061123

Altered expression of ganglioside GM3 molecular species and a potential regulatory role during myoblast differentiation

Shinji Go, Shiori Go, Lucas Veillon, Maria Grazia Ciampa, Laura Mauri, Chihiro Sato, Ken Kitajima, Alessandro Prinetti, Sandro Sonnino, Jin-ichi Inokuchi

JOURNAL OF BIOLOGICAL CHEMISTRY Vol. 292 ( 17 ) page： 7040 - 7051 2017.4

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

Gangliosides (sialic acid-containing glycosphingolipids) help regulate many important biological processes, including cell proliferation, signal transduction, and differentiation, via formation of functional microdomains in plasma membranes. The structural diversity of gangliosides arises from both the ceramide moiety and glycan portion. Recently, differing molecular species of a given ganglioside are suggested to have distinct biological properties and regulate specific and distinct biological events. Elucidation of the function of each molecular species is important and will provide new insights into ganglioside biology. Gangliosides are also suggested to be involved in skeletal muscle differentiation; however, the differential roles of ganglioside molecular species remain unclear. Here we describe striking changes in quantity and quality of gangliosides (particularly GM3) during differentiation of mouse C2C12 myoblast cells and key roles played by distinct GM3 molecular species at each step of the process.

DOI： 10.1074/jbc.M116.771253

Diverse subcellular localizations of the insect CMP-sialic acid synthetases

Wu Di, Akiko Fujita, Kayo Hamaguchi, Philippe Delannoy, Chihiro Sato, Ken Kitajima

GLYCOBIOLOGY Vol. 27 ( 4 ) page： 329 - 341 2017.4

Language：English Publishing type：Research paper (scientific journal) Publisher：OXFORD UNIV PRESS INC

The occurrence and biological importance of sialic acid (Sia) and its metabolic enzymes in insects have been studied using Drosophila melanogaster. The most prominent feature of D. melanogaster CMP-Sia synthetase (DmCSS) is its Golgi-localization, contrasted with nuclear localization of vertebrate CSSs. However, it remains unclear if the Golgi-localization is common to other insect CSSs and why it happens. To answer these questions, Aedes aegypti (mosquito) CSS (AaCSS) and Tribolium castaneum (beetle) CSS (TcCSS) were cloned and characterized for their activity and subcellular localization. Our new findings show: (1) AaCSS and TcCSS share a common overall structure with DmCSS in terms of evolutionarily conserved motifs and the absence of the C-terminal domain typical to vertebrate CSSs; (2) when expressed in mammalian and insect cells, AaCSS and TcCSS showed in vivo and in vitro CSS activities, similar to DmCSS. In contrast, when expressed in bacteria, they lacked CSS activity because the N-terminal hydrophobic region appeared to induce protein aggregation; (3) when expressed in Drosophila S2 cells, AaCSS and TcCSS were predominantly localized in the ER, but not in the Golgi. Surprisingly, DmCSS was mainly secreted into the culture medium, although partially detected in Golgi. Consistent with these results, the N-terminal hydrophobic regions of AaCSS and TcCSS functioned as a signal peptide to render them soluble in the ER, while the N-terminus of DmCSS functioned as a membrane-spanning region of type II transmembrane proteins whose cytosolic KLK sequence functioned as an ER export signal. Accordingly, the differential subcellular localization of insect CSSs are distinctively more diverse than previously recognized.

DOI： 10.1093/glycob/cww128

Synthesis of end-functionalized glycopolymers containing alpha(2,8) disialic acids via pi-allyl nickel catalyzed coordinating polymerization and their interaction with Siglec-7 Reviewed

Shuichi Ohira, Yu Yasuda, Ikuyoshi Tomita, Ken Kitajima, Takashi Takahashi, Chihiro Sato, Hiroshi Tanaka

CHEMICAL COMMUNICATIONS Vol. 53 ( 3 ) page： 553 - 556 2017.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

An allene monomer containing an alpha(2,8) disialic acid was polymerized by a pi-allyl nickel complex with an azido group to produce end-functional glycopolymers with an excellent polydispersity index. The polymers allowed terminal modification with a fluorescent dye by click chemistry. The glycopolymers can dissociate Siglec-7-GD3 interactions at low concentrations.

DOI： 10.1039/c6cc07115e

Synthesis of end-functionalized glycopolymers containing α(2,8) disialic acids via π-allyl nickel catalyzed coordinating polymerization and their interaction with Siglec-7. Reviewed

Ohira S, Yasuda Y, Tomita I, Kitajima K, Takahashi T, Sato C, Tanaka H.

Chem Commun (Camb). Vol. 53 ( 3 ) page： 553-556. 2017.1

Releasing Mechanism of Neurotrophic Factors via Polysialic Acid

C. Sato

NEUROTROPHINS Vol. 104 page： 89 - 112 2017

Language：English Publishing type：Part of collection (book) Publisher：ELSEVIER ACADEMIC PRESS INC

Neurotrophins are well-characterized neurologically active molecules in the central nervous system. The regulation of these signaling molecules, which are involved in cell growth, differentiation, and survival, is critical for normal brain function. Among the different types of neurotrophins, brain-derived neurotrophic factor (BDNF) is involved in various brain functions, including memory consolidation, synaptic plasticity, and adult neurogenesis, and is therefore a key molecule for understanding comprehensive brain function and neurodevelopmental and psychiatric diseases. The concentration of BDNF in body fluid is highly related to several neurodevelopmental and psychiatric diseases, including Alzheimer's diseases, depression, schizophrenia, and bipolar disorder. In the present review, the mechanisms by which BDNF is released from secretory vesicles are reviewed, with a particular focus on the recently described glycan-mediated release. In addition, the impact of glycan-mediated BDNF release on psychiatric disorders is also discussed.

DOI： 10.1016/bs.vh.2016.11.004