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Shun-ichiro Kawabata

Seung Ah Lee, Seong Han Jang, Byung Hyun Kim, Toshio Shibata, Jinwook Yoo, Yunjin Jung, Shun-Ichiro Kawabata, Bok Luel Lee
The biochemical characterization of virulence factors from entomopathogenic bacteria is important to understand entomopathogen-insect molecular interactions. Pseudomonas entomophila is a typical entomopathogenic bacterium that harbors virulence factors against several insects. However, the molecular actions of these factors against host innate immune responses are not clearly elucidated. In this study, we observed that bean bugs (Riptortus pedestris) that were injected with P. entomophila were highly susceptible to this bacterium...
April 2018: Developmental and Comparative Immunology
Toshio Shibata, Shun-Ichiro Kawabata
Transglutaminase (TG) catalyzes the formation of an isopeptide bond between glutamine and lysine residues and amine incorporation into specific glutamine residues. TG is conserved in all metazoans and functions both intracellularly and extracellularly. Here we review the existing knowledge of Drosophila TG with an emphasis on its pluripotency: Drosophila TG (i) plays a key role in cuticular morphogenesis, hemolymph coagulation, and entrapment against invading pathogens, (ii) suppresses the immune deficiency pathway to enable immune tolerance against commensal bacteria through the incorporation of polyamines into the NF-κB-like transcription factor Relish as well as through the protein-protein cross-linking of Relish, (iii) forms a physical matrix in the gut through cross-linking of chitin-binding proteins, and (iv) is involved in the maintenance of homeostasis in microbiota in the gut...
September 5, 2017: Journal of Biochemistry
Toshio Shibata, Jinki Hadano, Daichi Kawasaki, Xiaoqing Dong, Shun-Ichiro Kawabata
Transglutaminases (TGs) play essential intracellular and extracellular roles by covalently cross-linking many proteins. Drosophila TG is encoded by one gene and has two alternative splicing-derived isoforms, TG-A and TG-B, which contain distinct N-terminal 46- and 38-amino acid sequences, respectively. The TGs identified to date do not have a typical endoplasmic reticulum (ER)-signal peptide, and the molecular mechanisms of their secretion under physiologic conditions are unclear. Immunocytochemistry revealed that TG-A localizes to multivesicular-like structures, whereas TG-B localizes to the cytosol...
June 23, 2017: Journal of Biological Chemistry
Kouki Maki, Toshio Shibata, Shun-Ichiro Kawabata
In Drosophila , the final immune deficiency (IMD) pathway-dependent signal is transmitted through proteolytic conversion of the nuclear factor-κB (NF-κB)-like transcription factor Relish to the active N-terminal fragment Relish-N. Relish-N is then translocated from the cytosol into the nucleus for the expression of IMD-controlled genes. We previously demonstrated that transglutaminase (TG) suppresses the IMD pathway by polymerizing Relish-N to inhibit its nuclear translocation. Conversely, we also demonstrated that orally ingested synthetic amines, such as monodansylcadaverine (DCA) and biotin-labeled pentylamine, are TG-dependently incorporated into Relish-N, causing the nuclear translocation of modified Relish-N in gut epithelial cells...
April 14, 2017: Journal of Biological Chemistry
Hikaru Mizumura, Norihiko Ogura, Jun Aketagawa, Maki Aizawa, Yuki Kobayashi, Shun-Ichiro Kawabata, Toshio Oda
The bacterial endotoxin test, which uses amebocyte lysate reagents of horseshoe crab origin, is a sensitive, reproducible and simple assay to measure endotoxin concentration. To develop sustainable raw materials for lysate reagents that do not require horseshoe crabs, three recombinant protease zymogens (factor C, derived from mammalian cells; factor B; and the proclotting enzyme derived from insect cells) were prepared using a genetic engineering technique. Recombinant cascade reagents (RCRs) were then prepared to reconstruct the reaction cascade in the amebocyte lysate reagent...
February 2017: Innate Immunity
Hina Satone, Shohei Nonaka, Jae Man Lee, Yohei Shimasaki, Takahiro Kusakabe, Shun-Ichiro Kawabata, Yuji Oshima
We investigated the ability of recombinant pufferfish saxitoxin and tetrodotoxin binding protein types 1 and 2 of Takifugu rubripes (rTrub.PSTBP1 and rTrub.PSTBP2) to bind to tetrodotoxin (TTX) and tributyltin. Both rTrub.PSTBPs bound to tributyltin in an ultrafiltration binding assay but lost this ability on heat denaturation. In contrast, only rTrub.PSTBP2 bound to TTX even heat denaturation. This result suggests that the amino acid sequence of PSTBP2 may be contributed for its affinity for TTX.
January 2017: Toxicon: Official Journal of the International Society on Toxinology
Sanae Sekihara, Toshio Shibata, Mai Hyakkendani, Shun-Ichiro Kawabata
We recently reported that transglutaminase (TG) suppresses immune deficiency pathway-controlled antimicrobial peptides (IMD-AMPs), thereby conferring immune tolerance to gut microbes, and that RNAi of the TG gene in flies decreases the lifespan compared with non-TG-RNAi flies. Here, analysis of the bacterial composition of the Drosophila gut by next-generation sequencing revealed that gut microbiota comprising one dominant genus of Acetobacter in non-TG-RNAi flies was shifted to that comprising two dominant genera of Acetobacter and Providencia in TG-RNAi flies...
November 25, 2016: Journal of Biological Chemistry
Toshio Shibata, Kouki Maki, Jinki Hadano, Takumi Fujikawa, Kazuki Kitazaki, Takumi Koshiba, Shun-Ichiro Kawabata
[This corrects the article DOI: 10.1371/journal.ppat.1005244.].
June 2016: PLoS Pathogens
Toshio Shibata, Kouki Maki, Jinki Hadano, Takumi Fujikawa, Kazuki Kitazaki, Takumi Koshiba, Shun-ichiro Kawabata
Transglutaminase (TG) catalyzes protein-protein crosslinking, which has important and diverse roles in vertebrates and invertebrates. Here we demonstrate that Drosophila TG crosslinks drosocrystallin, a peritrophic matrix protein, to form a stable fiber structure on the gut peritrophic matrix. RNA interference (RNAi) of the TG gene was highly lethal in flies and induced apoptosis of gut epithelial cells after oral infection with Pseudomonas entomophila. Moreover, AprA, a metalloprotease secreted by P. entomophila, digested non-crosslinked drosocrystallin fibers, but not drosocrystallin fibers crosslinked by TG...
October 2015: PLoS Pathogens
Yuki Kobayashi, Toshiaki Takahashi, Toshio Shibata, Shunsuke Ikeda, Takumi Koshiba, Hikaru Mizumura, Toshio Oda, Shun-ichiro Kawabata
Factor B is a serine-protease zymogen in the horseshoe crab coagulation cascade, and it is the primary substrate for activated factor C, the LPS-responsive initiator of the cascade. Factor C is autocatalytically activated to α-factor C on LPS and is artificially converted to β-factor C, another activated form, by chymotrypsin. It is not known, however, whether LPS is required for the activation of factor B. Here we found that wild-type factor B expressed in HEK293S cells is activated by α-factor C, but not by β-factor C, in an LPS-dependent manner and that β-factor C loses the LPS binding activity of factor C through additional cleavage by chymotrypsin within the N-terminal LPS-binding region...
July 31, 2015: Journal of Biological Chemistry
Bok Luel Lee, Shun-ichiro Kawabata, Chengshu Wang, Yonggyun Kim
No abstract text is available yet for this article.
January 2015: Archives of Insect Biochemistry and Physiology
Takuma Yoshizumi, Takeshi Ichinohe, Osamu Sasaki, Hidenori Otera, Shun-ichiro Kawabata, Katsuyoshi Mihara, Takumi Koshiba
Mitochondria contribute to cellular innate immunity against RNA viruses. Mitochondrial-mediated innate immunity is regulated by signalling molecules that are recruited to the mitochondrial membrane, and depends on the mitochondrial inner membrane potential (Δψm). Here we examine the physiological relevance of Δψm and the mitochondrial-associating influenza A viral protein PB1-F2 in innate immunity. When expressed in host cells, PB1-F2 completely translocates into the mitochondrial inner membrane space via Tom40 channels, and its accumulation accelerates mitochondrial fragmentation due to reduced Δψm...
August 20, 2014: Nature Communications
Yuki Kobayashi, Takafumi Shiga, Toshio Shibata, Miyuki Sako, Katsumi Maenaka, Takumi Koshiba, Hikaru Mizumura, Toshio Oda, Shun-ichiro Kawabata
Factor C, a serine protease zymogen involved in innate immune responses in horseshoe crabs, is known to be autocatalytically activated on the surface of bacterial lipopolysaccharides, but the molecular mechanism of this activation remains unknown. In this study, we show that wild-type factor C expressed in HEK293S cells exhibits a lipopolysaccharide-induced activity equivalent to that of native factor C. Analysis of the N-terminal addition, deletion, or substitution mutants shows that the N-terminal Arg residue and the distance between the N terminus and the tripartite of lipopolysaccharide-binding site are essential factors for autocatalytic activation, and that the positive charge of the N terminus may interact with an acidic amino acid(s) of the molecule to convert the zymogen into an active form...
September 12, 2014: Journal of Biological Chemistry
Takahiro Kushibiki, Masakatsu Kamiya, Tomoyasu Aizawa, Yasuhiro Kumaki, Takashi Kikukawa, Mineyuki Mizuguchi, Makoto Demura, Shun-ichiro Kawabata, Keiichi Kawano
Lipopolysaccharide (LPS) is a major constituent of the outer membrane of Gram-negative bacteria and is the very first site of interactions with antimicrobial peptides (AMPs). In order to gain better insight into the interaction between LPS and AMPs, we determined the structure of tachyplesin I (TP I), an antimicrobial peptide derived from horseshoe crab, in its bound state with LPS and proposed the complex structure of TP I and LPS using a docking program. CD and NMR measurements revealed that binding to LPS slightly extends the two β-strands of TP I and stabilizes the whole structure of TP I...
March 2014: Biochimica et Biophysica Acta
Hina Satone, Eriko Akahoshi, Aiko Nakamura, Jae Man Lee, Masato Honda, Yohei Shimasaki, Shun-Ichiro Kawabata, Takahiro Kusakabe, Yuji Oshima
Tributyltin-binding proteins (TBT-bps) are members of the fish lipocalins that were isolated from the blood of Japanese flounder (Paralichthys olivaceus) and function in the binding and detoxification of TBT. In this study, we constructed a baculovirus-silkworm expression system and obtained recombinant TBT-bp2 (rTBT-bp2; 31.5 kDa) from the hemolymph of silkworm larvae injected with a recombinant baculovirus containing the TBT-bp2 gene. The binding potential of rTBT-bp2 was investigated and compared to that of the previously available recombinant TBT-bp1 (rTBT-bp1)...
2013: Journal of Toxicological Sciences
Toshio Shibata, Sanae Sekihara, Takumi Fujikawa, Ryuta Miyaji, Kouki Maki, Takeshi Ishihara, Takumi Koshiba, Shun-ichiro Kawabata
Cross-linking of proteins by mammalian transglutaminases (TGs) plays important roles in physiological phenomena such as blood coagulation and skin formation. We show that Drosophila TG suppressed innate immune signaling in the gut. RNA interference (RNAi) directed against TG reduced the life span of flies reared under conventional nonsterile conditions but not of those raised under germ-free conditions. In conventionally reared flies, TG RNAi enhanced the expression of genes encoding antimicrobial peptides in the immune deficiency (IMD) pathway...
July 23, 2013: Science Signaling
Osamu Sasaki, Takuma Yoshizumi, Misa Kuboyama, Takeshi Ishihara, Emiko Suzuki, Shun-ichiro Kawabata, Takumi Koshiba
In most eukaryotic cells, mitochondria have various essential roles for proper cell function, such as energy production, and in mammals mitochondria also act as a platform for antiviral innate immunity. Mitochondrial-mediated antiviral immunity depends on the activation of the cytoplasmic retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs) signaling pathway, and on the participation of mitochondrial antiviral signaling (MAVS), which is localized on the mitochondrial outer membrane. After RNA virus infection, RLRs translocate to the mitochondrial surface to interact with MAVS, and the adaptor protein undergoes a conformational change that is essential for downstream signaling, although its structural features are poorly understood...
May 2013: Biochimica et Biophysica Acta
Keisuke Tagawa, Toyoki Yoshihara, Toshio Shibata, Kazuki Kitazaki, Yuichi Endo, Teizo Fujita, Takumi Koshiba, Shun-ichiro Kawabata
Complement C3 plays an essential role in the opsonization of pathogens in the mammalian complement system, whereas the molecular mechanism underlying C3 activation in invertebrates remains unknown. To understand the molecular mechanism of C3b deposition on microbes, we characterized two types of C2/factor B homologs (designated TtC2/Bf-1 and TtC2/Bf-2) identified from the horseshoe crab Tachypleus tridentatus. Although the domain architectures of TtC2/Bf-1 and TtC2/Bf-2 were identical to those of mammalian homologs, they contained five-repeated and seven-repeated complement control protein domains at their N-terminal regions, respectively...
2012: PloS One
Shun-ichiro Kawabata
Horseshoe crab hemocyte selectively responds to bacterial lipopolysaccharides (LPS), which depends critically on the proteolytic activity of the LPS-responsive serine protease zymogen factor C. In response to stimulation by LPS, the hemocyte secretes several kinds of immunocompetent proteins. The coagulation cascade triggered by LPS or beta-1,3-D-glucans (BDG) results in the formation of coagulin fibrils that are subsequently stabilized by transglutaminase (TGase)-dependent cross-linking. Invading pathogens are recognized and agglutinated by lectins and then killed by antimicrobial peptides...
2010: Advances in Experimental Medicine and Biology
Hina Satone, Jae Man Lee, Yumi Oba, Takahiro Kusakabe, Eriko Akahoshi, Shizuho Miki, Nobuo Suzuki, Yuichi Sasayama, Mohamed Nassef, Yohei Shimasaki, Shun-Ichiro Kawabata, Tsuneo Honjo, Yuji Oshima
Tributyltin-binding protein type 1 (TBT-bp1) is a member of the lipocalin family of proteins which bind to small hydrophobic molecules. In this study, we expressed a recombinant TBT-bp1 (rTBT-bp1, ca. 35kDa) in a baculovirus expression system and purified the protein from the hemolymph of silkworm larvae injected with recombinant baculovirus. After incubation of a mixture of rTBT-bp1 and TBT and its fractionation by means of gel filtration chromatography, TBT was detected in the elution peak of rTBT-bp1, confirming the binding potential of rTBT-bp1 for TBT...
May 2011: Aquatic Toxicology
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