Nippon Institute for Biological Science

Ōme, Japan

Nippon Institute for Biological Science

Ōme, Japan

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Kobayashi T.,Tokyo Medical University | Ogawa M.,Tokyo Medical University | Sanada T.,Tokyo Medical University | Mimuro H.,Tokyo Medical University | And 10 more authors.
Cell Host and Microbe | Year: 2013

Caspase-mediated inflammatory cell death acts as an intrinsic defense mechanism against infection. Bacterial pathogens deploy countermeasures against inflammatory cell death, but the mechanisms by which they do this remain largely unclear. In a screen for Shigella flexneri effectors that regulate cell death during infection, we discovered that Shigella infection induced acute inflammatory, caspase-4-dependent epithelial cell death, which is counteracted by the bacterial OspC3 effector. OspC3 interacts with the caspase-4-p19 subunit and inhibits its activation by preventing caspase-4-p19 and caspase-4-p10 heterodimerization by depositing the conserved OspC3 X1-Y-X 2-D-X3 motif at the putative catalytic pocket of caspase-4. Infection of guinea pigs with a Shigella ospC3-deficient mutant resulted in enhanced inflammatory cell death and associated symptoms, correlating with decreased bacterial burdens. Salmonella Typhimurium and enteropathogenic Escherichia coli infection also induced caspase-4-dependent epithelial death. These findings highlight the importance of caspase-4-dependent innate immune responses and demonstrate that Shigella delivers a caspase-4-specific inhibitor to delay epithelial cell death and promote infection. © 2013 Elsevier Inc.


Oshima A.,Nippon Institute for Biological Science | Yamashita R.,Nippon Institute for Biological Science | Nakamura K.,Nippon Institute for Biological Science | Wada M.,Tokyo Medical and Dental University | Shibuya K.,Nippon Institute for Biological Science
Environmental Toxicology and Chemistry | Year: 2012

Sex reversal effects of nonylphenol and bisphenol A on the gonads in F 1(AWE×WE) Japanese quail (Coturnix japonica) embryos were investigated using an in vivo screening model developed previously. The F 1 (AWE×WE) Japanese quail are a useful avian model because sex differentiation is confirmed by the plumage color before hatching, ruled by a criss-cross inheritance. The nonylphenol at 200, 2,000, 20,000, and 200,000ng/egg and bisphenol A at 20, 200, 2,000, and 20,000ng/egg were injected into the egg white just before incubation. At 16d of incubation, embryos were subjected to a complete necropsy, and their gonads were both grossly observed and examined histopathologically and morphometrically. Grossly, genetic sex was confirmed because plumage color coincided completely with the external sex phenotype of the gonads in all embryos. Histopathologically, feminization of the male gonad, called ovotestis, developed in the left testis in all nonylphenol- and bisphenol A-treated groups. The incidence of the lesion in all treated groups was significantly higher than that in the control group, whereas there were no dose-dependent changes in the incidence and area of the ovotestis in both nonylphenol- and bisphenol A-treated groups. The present study revealed that nonylphenol and bisphenol A have a dose-independent potential of ovotestis induction in the Japanese quail embryo. © 2012 SETAC.


Ashida H.,Tokyo Medical University | Nakano H.,Juntendo University | Sasakawa C.,Tokyo Medical University | Sasakawa C.,Nippon Institute for Biological Science | Sasakawa C.,Chiba University
PLoS Pathogens | Year: 2013

NF-κB plays a central role in modulating innate immune responses to bacterial infections. Therefore, many bacterial pathogens deploy multiple mechanisms to counteract NF-κB activation. The invasion of and subsequent replication of Shigella within epithelial cells is recognized by various pathogen recognition receptors as pathogen-associated molecular patterns. These receptors trigger innate defense mechanisms via the activation of the NF-κB signaling pathway. Here, we show the inhibition of the NF-κB activation by the delivery of the IpaH E3 ubiquitin ligase family member IpaH0722 using Shigella's type III secretion system. IpaH0722 dampens the acute inflammatory response by preferentially inhibiting the PKC-mediated activation of NF-κB by ubiquitinating TRAF2, a molecule downstream of PKC, and by promoting its proteasome-dependent degradation. © 2013 Ashida et al.


Fukumatsu M.,University of Tokyo | Ogawa M.,Tokyo Medical University | Arakawa S.,Tokyo Medical and Dental University | Suzuki M.,Tokyo Medical University | And 7 more authors.
Cell Host and Microbe | Year: 2012

Bacteria move between cells in the epithelium using a sequential pseudopodium-mediated process but the underlying mechanisms remain unclear. We show that during cell-to-cell movement, Shigella-containing pseudopodia target epithelial tricellular junctions, the contact point where three epithelial cells meet. The bacteria-containing pseudopodia were engulfed by neighboring cells only in the presence of tricellulin, a protein essential for tricellular junction integrity. Shigella cell-to-cell spread, but not pseudopodium protrusion, also depended on phosphoinositide 3-kinase, clathrin, Epsin-1, and Dynamin-2, which localized beneath the plasma membrane of the engulfing cell. Depleting tricellulin, Epsin-1, clathrin, or Dynamin-2 expression reduced Shigella cell-to-cell spread, whereas AP-2, Dab2, and Eps15 were not critical for this process. Our findings highlight a mechanism for Shigella dissemination into neighboring cells via targeting of tricellular junctions and a noncanonical clathrin-dependent endocytic pathway. © 2012 Elsevier Inc.


Ashida H.,Tokyo Medical University | Mimuro H.,Tokyo International University | Sasakawa C.,Tokyo Medical University | Sasakawa C.,Nippon Institute for Biological Science | Sasakawa C.,Chiba University
Frontiers in Immunology | Year: 2015

The intestinal epithelium deploys multiple defense systems against microbial infection to sense bacterial components and danger alarms, as well as to induce intracellular signal transduction cascades that trigger both the innate and the adaptive immune systems, which are pivotal for bacterial elimination. However, many enteric bacterial pathogens, including Shigella, deliver a subset of virulence proteins (effectors) via the type III secretion system (T3SS) that enable bacterial evasion from host immune systems; consequently, these pathogens are able to efficiently colonize the intestinal epithelium. In this review, we present and select recently discovered examples of interactions between Shigella and host immune responses, with particular emphasis on strategies that bacteria use to manipulate inflammatory outputs of host-cell responses such as cell death, membrane trafficking, and innate and adaptive immune responses. © 2015 Ashida, Mimuro and Sasakawa.


Ashida H.,Tokyo Medical University | Sasakawa C.,Tokyo Medical University | Sasakawa C.,Nippon Institute for Biological Science | Sasakawa C.,Chiba University
EMBO Journal | Year: 2014

Bacterial pathogens alter host transcriptional programs to promote infection. Shigella OspF is an essential virulence protein with a unique phosphothreonine lyase activity. A new study in The EMBO Journal (Harouz et al,) reveals a novel function of OspF: targeting of heterochromatin protein 1γ (HP1γ) and downregulation of a subset of immune genes. These results illustrate how bacterial pathogens exploit epigenetic modifications to counteract host immune responses. During infection, Shigella injects effector protein OspF to modulate the epigenetic status of specific host genes. This effect involves dual targeting of both histones and the chromatin reader HP1γ. © 2014 The Authors.


Doi K.,Nippon Institute for Biological Science | Doi K.,University of Tokyo | Uetsuka K.,Nippon Institute for Biological Science
International Journal of Molecular Sciences | Year: 2011

Among many mycotoxins, T-2 toxin, macrocyclic trichothecenes, fumonisin B 1 (FB 1) and ochratochin A (OTA) are known to have the potential to induce neurotoxicity in rodent models. T-2 toxin induces neuronal cell apoptosis in the fetal and adult brain. Macrocyclic trichothecenes bring about neuronal cell apoptosis and inflammation in the olfactory epithelium and olfactory bulb. FB 1 induces neuronal degeneration in the cerebral cortex, concurrent with disruption of de novo ceramide synthesis. OTA causes acute depletion of striatal dopamine and its metabolites, accompanying evidence of neuronal cell apoptosis in the substantia nigra, striatum and hippocampus. This paper reviews the mechanisms of neurotoxicity induced by these mycotoxins especially from the viewpoint of oxidative stress-associated pathways. © 2011 by the authors; licensee MDPI, Basel, Switzerland.


Suzuki S.,University of Michigan | Suzuki S.,Tokyo Medical University | Franchi L.,University of Michigan | Franchi L.,Lycera Corporation | And 7 more authors.
PLoS Pathogens | Year: 2014

Recognition of intracellular pathogenic bacteria by members of the nucleotide-binding domain and leucine-rich repeat containing (NLR) family triggers immune responses against bacterial infection. A major response induced by several Gram-negative bacteria is the activation of caspase-1 via the Nlrc4 inflammasome. Upon activation, caspase-1 regulates the processing of proIL-1β and proIL-18 leading to the release of mature IL-1β and IL-18, and induction of pyroptosis. The activation of the Nlrc4 inflammasome requires the presence of an intact type III or IV secretion system that mediates the translocation of small amounts of flagellin or PrgJ-like rod proteins into the host cytosol to induce Nlrc4 activation. Using the Salmonella system, it was shown that Naip2 and Naip5 link flagellin and the rod protein PrgJ, respectively, to Nlrc4. Furthermore, phosphorylation of Nlrc4 at Ser533 by Pkcδ was found to be critical for the activation of the Nlrc4 inflammasome. Here, we show that Naip2 recognizes the Shigella T3SS inner rod protein MxiI and induces Nlrc4 inflammasome activation. The expression of MxiI in primary macrophages was sufficient to induce pyroptosis and IL-1β release, which were prevented in macrophages deficient in Nlrc4. In the presence of MxiI or Shigella infection, MxiI associated with Naip2, and Naip2 interacted with Nlrc4. siRNA-mediated knockdown of Naip2, but not Naip5, inhibited Shigella-induced caspase-1 activation, IL-1β maturation and Asc pyroptosome formation. Notably, the Pkcδ kinase was dispensable for caspase-1 activation and secretion of IL-1β induced by Shigella or Salmonella infection. These results indicate that activation of caspase-1 by Shigella is triggered by the rod protein MxiI that interacts with Naip2 to induce activation of the Nlrc4 inflammasome independently of the Pkcδ kinase. © 2014 Suzuki et al.


Jo E.-K.,Chungnam National University | Kim J.K.,Chungnam National University | Shin D.-M.,Chungnam National University | Sasakawa C.,Chiba University | Sasakawa C.,Nippon Institute for Biological Science
Cellular and Molecular Immunology | Year: 2016

Inflammasomes are multi-protein signaling complexes that trigger the activation of inflammatory caspases and the maturation of interleukin-1β. Among various inflammasome complexes, the NLRP3 inflammasome is best characterized and has been linked with various human autoinflammatory and autoimmune diseases. Thus, the NLRP3 inflammasome may be a promising target for anti-inflammatory therapies. In this review, we summarize the current understanding of the mechanisms by which the NLRP3 inflammasome is activated in the cytosol. We also describe the binding partners of NLRP3 inflammasome complexes activating or inhibiting the inflammasome assembly. Our knowledge of the mechanisms regulating NLRP3 inflammasome signaling and how these influence inflammatory responses offers further insight into potential therapeutic strategies to treat inflammatory diseases associated with dysregulation of the NLRP3 inflammasome. © 2016 CSI and USTC. All rights reserved.


Ashida H.,Tokyo Medical University | Kim M.,Nippon Institute for Biological Science | Sasakawa C.,Tokyo Medical University | Sasakawa C.,Nippon Institute for Biological Science | Sasakawa C.,Chiba University
Nature Reviews Microbiology | Year: 2014

Ubiquitylation is a crucial post-translational protein modification that regulates several cellular processes in eukaryotes, including inflammatory responses, endocytic trafficking and the cell cycle. Importantly, ubiquitylation also has a central role in modulating eukaryotic defence systems; however, accumulating evidence shows that many bacterial pathogens exploit host ubiquitin systems for their own benefit. In this Review, we highlight the ways in which human bacterial pathogens target ubiquitylation to subvert and manipulate host defence systems, with a focus on the role of molecular mimicry and secreted bacterial effector proteins. These strategies enable bacterial pathogens to maximize effector function and obtain nutrients, thereby promoting bacterial proliferation. © 2014 Macmillan Publishers Limited. All rights reserved.

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