掲載種別：研究論文（学術雑誌）   出版者・発行元：Public Library of Science (PLoS)  

Zinc is an essential metal for cells, but excess amounts are toxic. Other than by regulating the intracellular zinc concentration by zinc uptake or efflux, the mechanisms underlying bacterial resistance to excess zinc are unknown. In the present study, we searched for zinc-resistant mutant strains from the Keio collection, a gene knockout library of Escherichia coli, a model gram-negative bacteria. We found that knockout mutant of RpmJ (L36), a 50S ribosomal protein, exhibited zinc resistance. The rpmJ mutant was sensitive to protein synthesis inhibitors and had altered translation fidelity, indicating ribosomal dysfunction. In the rpmJ mutant, the intracellular zinc concentration was decreased under excess zinc conditions. Knockout of ZntA, a zinc efflux pump, abolished the zinc-resistant phenotype of the rpmJ mutant. RNA sequence analysis revealed that the rpmJ mutant exhibited altered gene expression of diverse functional categories, including translation, energy metabolism, and stress response. These findings suggest that knocking out RpmJ alters gene expression patterns and causes zinc resistance by lowering the intracellular zinc concentration. Knockouts of other ribosomal proteins, including RplA, RpmE, RpmI, and RpsT, also led to a zinc-resistant phenotype, suggesting that deletion of ribosomal proteins is closely related to zinc resistance.

DOI： 10.1371/journal.pone.0277162

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

We previously reported that knockout of the mazG (SA1292) gene decreases Staphylococcus aureus killing activity against silkworms. S. aureus MazG (SaMazG) has a nucleotide pyrophosphatase domain conserved among MazG family proteins, but its biochemical characteristics are unknown. In the present study, we purified recombinant N-terminal His-tagged SaMazG protein and examined its biochemical activity. SaMazG hydrolyzed GTP, UTP, dGTP, and TTP into nucleoside monophosphates. Hydrolytic activity of SaMazG against ATP, CTP, dATP, and dCTP was low or not detected. SaMazG exhibited high hydrolytic activity against 8-oxo-GTP and 8-oxo-dGTP, oxidized guanine nucleotides, with a Vmax/Km ratio more than 15-fold that of GTP. Furthermore, the S. aureus mazG knockout mutant was sensitive to hydrogen peroxide compared with the parent strain. These results suggest that SaMazG is a nucleotide pyrophosphatase hydrolyzing oxidized guanine nucleotides that contributes to the oxidative stress resistance of S. aureus.

DOI： 10.1016/j.biochi.2023.02.001

PubMed

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掲載種別：研究論文（学術雑誌）   出版者・発行元：American Society for Microbiology  

Although vancomycin is effective against Gram-positive bacteria, vancomycin-resistant bacteria are a major public health concern. While the vancomycin-resistance mechanisms of clinically important bacteria such as Staphylococcus aureus , Enterococcus faecium , and Streptococcus pneumoniae are well studied, they remain unclear in other Gram-positive bacteria.

DOI： 10.1128/jb.00387-22

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Public Library of Science (PLoS)  

The mlaA gene encodes a lipoprotein to maintain an outer membrane lipid asymmetry in gram-negative bacteria. Although the role of mlaA in bacterial virulence has been studied in several bacterial species, there are no reports of its role in E. coli virulence. In this study, we found that knockout of mlaA in E. coli increased its virulence against silkworms. The mlaA-knockout mutant was sensitive to several antibiotics and detergents, but resistant to vancomycin and chlorhexidine. The mlaA-knockout mutant grew faster than the parent strain in the presence of silkworm hemolymph. The mlaA-knockout mutant also produced a larger amount of outer membrane vesicles than the parent strain. These findings suggest that mlaA knockout causes E. coli resistance to specific antimicrobial substances and increases outer membrane vesicle production, thereby enhancing E. coli virulence properties in the silkworm infection model.

DOI： 10.1371/journal.pone.0270166

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Mast cells are activated upon immunoglobulin E (IgE)-mediated antigen stimulation, and release a wide variety of mediators, including histamine to trigger inflammatory responses. The surface expression levels of Fcε receptor I (FcεRI), a high affinity receptor of IgE, were found to be positively regulated by IgE. IgE could protect murine cultured mast cells from apoptotic cell death induced by the deprivation of interleukin-3 and a certain kind of IgE could activate immature mast cells in the absence of antigens, leading to the release of pro-inflammatory cytokines and a transient increase in histamine synthesis. Histamine synthesis in mast cells was found to be required for the maturation of murine connective tissue-type mast cells, raising the possibility that IgE indirectly modulates local mast cell maturation. Although it remains controversial to what extent this concept of "monomeric IgE effects" could have relevance in the modulation of human mast cell functions, the therapeutic effects of anti-IgE antibodies might be accounted for in terms of the decreased serum IgE concentrations. Because drastic increases in serum IgE concentrations are often observed in patients with atopic dermatitis and chronic urticaria, a close investigation of the roles of IgE in mast cell maturation should contribute to development of novel therapeutic approaches for these inflammatory diseases.

DOI： 10.3390/cells10082170

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Clarifying the molecular mechanisms by which bacteria acquire virulence traits is important for understanding the bacterial virulence system. In the present study, we utilized a bacterial evolution method in a silkworm infection model and revealed that deletion of the opgGH operon, encoding synthases for osmoregulated periplasmic glucan (OPG), increased the virulence of a nonpathogenic laboratory strain of Escherichia coli against silkworms. The opgGH knockout mutant exhibited resistance to host antimicrobial peptides and antibiotics. Compared with the parent strain, the opgGH knockout mutant produced greater amounts of colanic acid, which is involved in E. coli resistance to antibiotics. RNA sequence analysis revealed that the opgGH knockout altered the expression of various genes, including the evgS/evgA two-component system that functions in antibiotic resistance. In both a colanic acid-negative background and an evgS-null background, the opgGH knockout increased E. coli resistance to antibiotics and increased the silkworm-killing activity of E. coli. In the null background of the envZ/ompR two-component system, which genetically interacts with opgGH, the opgGH knockout increased antibiotic resistance and virulence in silkworms. These findings suggest that the absence of OPG confers antimicrobial resistance and virulence in E. coli in a colanic acid-, evgS/evgA-, and envZ/ompR-independent manner. IMPORTANCE The gene mutation types that increase the bacterial virulence of Escherichia coli remain unclear, in part due to the limited number of methods available for isolating bacterial mutants with increased virulence. We utilized a bacterial evolution method in the silkworm infection model, in which silkworms were infected with mutagenized bacteria and highly virulent bacterial mutants were isolated from dead silkworms. We revealed that knockout of OPG synthases increased E. coli virulence against silkworms. The OPG knockout mutants were resistant to host antimicrobial peptides as well as antibiotics. Our findings not only suggest a novel mechanism for virulence acquisition in E. coli but also support the usefulness of the bacterial experimental evolution method in the silkworm infection model.

DOI： 10.1128/JB.00515-20

PubMed

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media LLC  

<title>Abstract</title>Bacterial and viral respiratory infections can initiate acute lung injury and acute respiratory distress syndrome. Neutrophils and their granule enzymes, including neutrophil elastase, are key mediators of the pathophysiology of acute respiratory failure. Although intracellular neutrophil elastase functions as a host defensive factor against pathogens, its leakage into airway spaces induces degradation of host connective tissue components. This leakage disrupts host innate immune responses via proteolytic cleavage of Toll-like receptors and cytokines. Here, we investigated whether neutrophils possess proteases that cleave adaptive immune molecules. We found that expression of the human leukocyte antigen (HLA) class II molecule HLA-DP β1 was decreased in THP-1-derived macrophages treated with supernatants from dead neutrophils. This decreased HLA-DP β1 expression was counteracted by treatment with neutrophil elastase inhibitor, suggesting proteolytic cleavage of HLA-DP β1 by neutrophil elastase. SDS-PAGE showed that neutrophil elastase cleaved recombinant HLA-DP α1, -DP β1, -DQ α1, -DQ β1, -DR α, and -DR β1. Neutrophil elastase also cleaved HLA-DP β1 on extracellular vesicles isolated from macrophages without triggering morphological changes. Thus, leakage of neutrophil elastase may disrupt innate immune responses, antigen presentation, and T cell activation. Additionally, inhibition of neutrophil elastase is a potential therapeutic option for treating bacterial and viral pneumonia.

DOI： 10.1038/s41598-021-82212-5

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その他リンク： http://www.nature.com/articles/s41598-021-82212-5

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The use of non-human animal models for infection experiments is important for investigating the infectious processes of human pathogenic bacteria at the molecular level. Mammals, such as mice and rabbits, are also utilized as animal infection models, but large numbers of animals are needed for these experiments, which is costly, and fraught with ethical issues. Various non-mammalian animal infection models have been used to investigate the molecular mechanisms of various human pathogenic bacteria, including Staphylococcus aureus, Streptococcus pyogenes, and Pseudomonas aeruginosa. This review discusses the desirable characteristics of non-mammalian infection models and describes recent non-mammalian infection models that utilize Caenorhabditis elegans, silkworm, fruit fly, zebrafish, two-spotted cricket, hornworm, and waxworm.

DOI： 10.1111/1348-0421.12834

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担当区分：最終著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In addition to antigen presentation to CD4+ T cells, aggregation of cell surface major histocompatibility complex class II (MHC-II) molecules induces signal transduction in antigen presenting cells that regulate cellular functions. We previously reported that crosslinking of MHC-II induced the endocytosis of MHC-II, which was associated with decreased surface expression levels in murine dendritic cells (DCs) and resulted in impaired activation of CD4+ T cells. However, the downstream signal that induces MHC-II endocytosis remains to be elucidated. In this study, we found that the crosslinking of MHC-II induced intracellular Ca2+ mobilization, which was necessary for crosslinking-induced MHC-II endocytosis. We also found that these events were suppressed by inhibitors of Syk and phospholipase C (PLC). Treatments with a phorbol ester promoted MHC-II endocytosis, whereas inhibitors of protein kinase C (PKC) suppressed crosslinking-induced endocytosis of MHC-II. These results suggest that PKC could be involved in this process. Furthermore, crosslinking-induced MHC-II endocytosis was suppressed by inhibitors of clathrin-dependent endocytosis. Our results indicate that the crosslinking of MHC-II could stimulate Ca2+ mobilization and induce the clathrin-dependent endocytosis of MHC-II in murine DCs.

DOI： 10.3390/cells9081810

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Extracellular ATP released from stimulated and/or damaged cells modulates physiological responses via stimulation of various purinoceptors. We previously showed that ATP potentiated the Ag-induced mast cell (MC) degranulation via purinoceptors pharmacologically similar to the ionotropic P2X4 receptor. In this study, we investigated the role of P2X4 receptor in MC degranulation induced by stimulation of IgE-FcεRI complex with Ag, using bone marrow-derived MCs (BMMCs) prepared from wild type and P2X4 receptor-deficient (P2rx4-/- ) mice. ATP significantly increased Ag-induced degranulation in BMMCs prepared from wild type mice. This effect of ATP was reduced in BMMCs prepared from P2rx4-/- mice. The potentiating effect of ATP was restored by expressing P2X4 receptor in P2rx4-/- BMMCs. The P2X4 receptor-mediated effects were maintained even after differentiating into the connective tissue-type MCs. P2X4 receptor stimulation did not affect the Ag-induced Ca2+ response but enhanced Ag-induced early signals, such as tyrosine phosphorylation of Syk and phospholipase C-γ. Interestingly, these effects of ATP on Syk phosphorylation were not impaired by pretreatment with Cu2+, an inhibitor of the P2X4 receptor channel, or removal of external Ca2+, suggesting that a mechanisms other than Ca2+ influx through ion channel activity may be involved. In vivo experiments revealed that systemic and intradermal passive anaphylaxis responses were significantly alleviated in P2rx4-/- mice. Taken together, the present data suggest that the P2X4 receptor plays an essential role in ATP-induced upregulation of MC degranulation in response to Ag, and also contributes to the Ag-induced allergic response in vivo.

DOI： 10.4049/jimmunol.1900954

PubMed

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Accumulating evidence suggests that mast cells play critical roles in disruption and maintenance of intestinal homeostasis, although it remains unknown how they affect the local microenvironment. Interleukin-9 (IL-9) was found to play critical roles in intestinal mast cell accumulation induced in various pathological conditions, such as parasite infection and oral allergen-induced anaphylaxis. Newly recruited intestinal mast cells trigger inflammatory responses and damage epithelial integrity through release of a wide variety of mediators including mast cell proteases. We established a novel culture model (IL-9-modified mast cells, MCs/IL-9), in which murine IL-3-dependent bone-marrow-derived cultured mast cells (BMMCs) were further cultured in the presence of stem cell factor and IL-9. In MCs/IL-9, drastic upregulation of Mcpt1 and Mcpt2 was found. Although histamine storage and tryptase activity were significantly downregulated in the presence of SCF and IL-9, this was entirely reversed when mast cells were cocultured with a murine fibroblastic cell line, Swiss 3T3. MCs/IL-9 underwent degranulation upon IgE-mediated antigen stimulation, which was found to less sensitive to lower concentrations of IgE in comparison with BMMCs. This model might be useful for investigation of the spatiotemporal changes of newly recruited intestinal mast cells.

DOI： 10.3390/ijms21010236

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Mast cells play a pivotal role in allergic reactions and inflammations. Aggregation of the high affinity IgE receptor (FcεRI) eventually leads to the release of granule components such as histamine, as well as the de novo synthesis of inflammatory cytokines and lipid mediators. These substances are involved in the development of allergy and inflammation. Therefore, efficient inhibitors of mast cell activation would be therapeutically beneficial. We previously demonstrated that the synthetic peptide derived from the NH2-terminal region (2-17: GNIFANLFKGLFGKKE) of a small GTPase ARF1 (ADP-ribosylation factor1) inhibited FcεRI-induced mast cell degranulation. However, detailed structure-activity relationship study of NH2-terminal portion of ARF1 peptide has not been done. In addition, it is still unclear whether the NH2-terminal peptide of ARF1 suppresses FcεRI-induced production of cytokines and lipid mediators such as leukotriene C4 (LTC4) from mast cells. Here we show that amino acid residues K10-K16 are necessary for ARF1 peptide to efficiently inhibit FcεRI-induced activation of bone marrow-derived mast cells (BMMCs), indicated by decreased mast cell degranulation, cytokine secretion and leukotriene release. Furthermore, we show that ARF1 peptide inhibits IgE-mediated passive cutaneous anaphylaxis reaction. Our results suggest that the peptide derived from ARF1 could be developed into a novel anti-allergic agent for therapeutic intervention in allergy and mast cell-related pathologies.

DOI： 10.1016/j.molimm.2018.11.002

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3390/cells8020112

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/all.13555

PubMed

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3390/ijms19124083

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

Mast cells are secretory cells that play an important role in host defense by discharging various intragranular contents, such as histamine and serotonin, upon stimulation of Fc receptors. The granules also contain spermine and spermidine, which can act as modulators of mast cell function, although the mechanism underlying vesicular storage remains unknown. Vesicular polyamine transporter (VPAT), the fourth member of the SLC18 transporter family, is an active transporter responsible for vesicular storage of spermine and spermidine in neurons. In the present study, we investigated whether VPAT functions in mast cells. RT-PCR and Western blotting indicated VPAT expression in murine bone marrow-derived mast cells (BMMCs). Immunohistochemical analysis indicated that VPAT is colocalized with VAMP3 but not with histamine, serotonin, cathepsin D, VAMP2, or VAMP7. Membrane vesicles from BMMCs accumulated spermidine upon the addition of ATP in a reserpine- and bafilomycin A(1)-sensitive manner. BMMCs secreted spermine and spermidine upon the addition of either antigen or A23187 in the presence of Ca2+, and the antigen-mediated release, which was shown to be temperature-dependent and sensitive to bafilomycin A(1) and tetanus toxin, was significantly suppressed by VPAT gene RNA interference. Under these conditions, expression of vesicular monoamine transporter 2 was unaffected, but antigen-dependent histamine release was significantly suppressed, which was recovered by the addition of 1 mm spermine. These results strongly suggest that VPAT is expressed and is responsible for vesicular storage of spermine and spermidine in novel secretory granules that differ from histamine- and serotonin-containing granules and is involved in vesicular release of these polyamines from mast cells.

DOI： 10.1074/jbc.M116.756197

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-BLACKWELL  

Accumulating evidence suggests that activated mast cells are involved in contact hypersensitivity, although the precise mechanisms of their activation are still not completely understood. We investigated the potential of common experimental allergens to induce mast cell activation using murine bone marrow-derived cultured mast cells and rat peritoneal mast cells. Among these allergens, 1-chloro-2,4-dinitrobenzene and 1-fluoro-2,4-dinirobenzene (DNFB) were found to induce degranulation of rat peritoneal mast cells. DNFB-induced degranulation is accompanied by cytosolic Ca2+ mobilization and is significantly inhibited by pertussis toxin, U73122 (a phospholipase C inhibitor), and BAPTA (a Ca2+ chelator), raising the possibility that DNFB acts on the G protein-coupled receptors and activates Gi, which induces activation of phospholipase C, as well as known mast cell secretagogues, such as compound 48/ 80. DNFB could induce mast cell degranulation in the absence of serum proteins and IgE. Structure-activity relationship analyses revealed an inverse correlation between the degree of degranulation and the electron density of the C1 carbon of the DNFB derivatives. These findings raise a possibility that DNFB functions as a potent contact allergen through induction of cutaneous mast cell degranulation.

DOI： 10.1002/eji.201646536

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

Accumulating evidence suggests that several IgE clones can activate mast cells during the sensitization phase even in the absence of antigen. They were found to induce pro-inflammatory cytokine release, histamine synthesis, chemotaxis, adhesion, and accelerated maturation of mast cells, although it remains unknown whether antigen-induced responses can be affected by differences of IgE clones. We compared two IgE clones, which were different in the capacity to activate mast cells during sensitization, in terms of potentials to affect antigen-induced degranulation and cytokine releases using IL-3-dependent murine bone marrow-derived cultured mast cells (BMMCs). Antigen-induced degranulation and pro-inflammatory cytokine release were augmented, when BMMCs were sensitized with elevated concentrations of a clone IgE-3, which did not induce phosphorylation of JNK and cytokine release in the absence of antigen, whereas those were significantly rather decreased, when BMMCs were sensitized with elevated concentrations of a clone SPE-7, one of the most potent cytokinergic IgE clones, which intensively induced phosphorylation of JNK. This attenuated response with SPE-7 was accompanied by decreased tyrosine phosphorylation of the cellular proteins including Syk upon antigen stimulation. SP600125, which is known to inhibit JNK, restored the levels of antigen-induced degranulation and phosphorylation of Syk in BMMCs sensitized with higher concentrations of a clone SPE-7 when it was added before sensitization. Treatment with anisomycin, a potent activator of JNK, before IgE sensitization significantly suppressed antigen-induced degranulation. These findings suggest that differences of sensitizing IgE clones can affect antigen-induced responses and activation of JNK during sensitization might suppress antigen-induced activation of mast cells. (C) 2016 European Federation of Immunological Societies. Published by Elsevier B.V. All rights reserved.

DOI： 10.1016/j.imlet.2016.04.003

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER CHEMICAL SOC  

Mast cells secrete histamine upon degranulation triggered by various stimuli. Herein, we report the new detection method of mast cell degranulation using the fluorescent probe capable of detection of the released histamine. The probe was designed as the Co(II) complex of a cyanine dye, which shows a turn-on fluorescence signal based on a histamine-induced coordination displacement mechanism. Fluorescence imaging using the cell surface-anchored fluorescent probe enabled the real-time detection of mast cell degranulation induced by various secretagogues.

DOI： 10.1021/acs.analchem.5b04758

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATURE PUBLISHING GROUP  

Antigenic peptide-loaded MHC class II molecules (peptide-MHC class II) are constitutively expressed on the surface of professional antigen-presenting cells (APCs), including dendritic cells, B cells, macrophages and thymic epithelial cells, and are presented to antigen-specific CD4(+) T cells. The mechanisms of antigen uptake, the nature of the antigen processing compartments and the lifetime of cell surface peptide-MHC class II complexes can vary depending on the type of APC. It is likely that these differences are important for the function of each distinct APC subset in the generation of effective adaptive immune responses. In this Review, we describe our current knowledge of the mechanisms of uptake and processing of antigens, the intracellular formation of peptide-MHC class II complexes, the intracellular trafficking of peptide-MHC class II complexes to the APC plasma membrane and their ultimate degradation.

DOI： 10.1038/nri3818

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY  

DOI： 10.1002/eji.201343838

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1248/bpb.b13-00616

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATL ACAD SCIENCES  

As sentinels of the immune system, dendritic cells (DCs) continuously generate and turnover antigenic peptide-MHC class II complexes (pMHC-II). pMHC-II generation is a complex process that involves many well-characterized MHC-II biosynthetic intermediates; however, the mechanisms leading to MHC-II turnover/degradation are poorly understood. We now show that pMHC-II complexes undergoing clathrin-independent endocytosis from the DC surface are efficiently ubiquitinated by the E3 ubiquitin ligase March-I in early endosomes, whereas biosynthetically immature MHC-II-Invariant chain (Ii) complexes are not. The inability of MHC-II-Ii to serve as a March-I substrate is a consequence of Ii sorting motifs that divert the MHC-II-Ii complex away from March-I+ early endosomes. When these sorting motifs are mutated, or when clathrin-mediated endocytosis is inhibited, MHC-II-Ii complexes internalize by using a clathrin-independent endocytosis pathway and are now ubiquitinated as efficiently as pMHC-II complexes. These data show that the selective ubiquitination of internalizing surface pMHC-II in March-I+ early endosomes promotes degradation of "old" pMHC-II and spares forms of MHC-II that have not yet loaded antigenic peptides or have not yet reached the DC surface.

DOI： 10.1073/pnas.1312994110

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATL ACAD SCIENCES  

Major histocompatibility complex class II molecules (MHC-II) on antigen presenting cells (APCs) engage the TCR on antigen-specific CD4 T cells, thereby providing the specificity required for T cell priming and the induction of an effective immune response. In this study, we have asked whether antigen-loaded dendritic cells (DCs) that have been in contactwith antigen-specific CD4 T cells retain the ability to stimulate additional naive T cells. We show that encounter with antigen-specific primed CD4 T cells induces the degradation of surface MHC-II in antigen-loaded DCs and inhibits the ability of these DCs to stimulate additional naive CD4 T cells. Cross-linking with MHC-II mAb as a surrogate for T-cell engagement also inhibits APC function and induces MHC-II degradation by promoting the clustering of MHC-II present in lipid raft membrane microdomains, a process that leads to MHC-II endocytosis and degradation in lysosomes. Encounter of DCs with antigen-specific primed T cells or engagement of MHC-II with antibodies promotes the degradation of both immunologically relevant and irrelevant MHC-II molecules. These data demonstrate that engagement of MHC-II on DCs after encounter with antigen-specific primed CD4 T cells promotes the down-regulation of cell surface MHC-II in DCs, thereby attenuating additional activation of naive CD4 T cells by these APCs.

DOI： 10.1073/pnas.1213868109

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PHARMACEUTICAL SOC JAPAN  

Appropriate culture models for tissue mast cells are required to determine how they are involved in regulation of local immune responses. We previously established a culture model for cutaneous mast cells, in which bone marrow-derived immature mast cells were co-cultured with Swiss 3T3 fibroblasts in the presence of stem cell factor. In this study, we focused on the roles of hyaluronan, which is produced by the feeder fibroblasts and forms the extracellular matrix during the co-culture period. Hyaluronan synthesis was found to be mediated by hyaluronan synthase 2 (HAS2) expressed in Swiss 3T3 cells. A decreases in the amount of hyaluronan, which was achieved by retroviral expression of short hairpin RNA for Has2 or by addition of hyaluronidase, significantly enhanced the proliferation of the cultured mast cells without any obvious effects on their maturation. Although we previously demonstrated that CD44 is required for proliferation of cutaneous mast cells, the deficiency of hyaluronan did not affect the proliferation of the cultured mast cells that lack CD44. These findings suggest that the extracellular matrix containing hyaluronan may have a potential to restrict proliferation of cutaneous mast cells in a CD44-independent manner.

DOI： 10.1248/bpb.35.408

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

The expression of MHC class II (MHC-II) on the surface of antigen-presenting cells, such as dendritic cells (DCs), is tightly regulated during cellular activation. Many cells, including DCs, are activated following stimulation of innate Toll-like receptors (TLRs) by products of microorganisms. In the resting (immature) state, MHC-II is ubiquitinated in immature DCs and is rapidly degraded; however, after activation of these cells with MyD88-dependent TLR ligands, MHC-II ubiquitination is blocked, and MHC-II survival is prolonged. We now show that DC activation using MyD88-dependent TLR ligands, MyD88-independent TLR ligands, and even infection with the intracellular parasite Toxoplasma gondii leads to identical changes in MHC-II expression, ubiquitination, and surface stability, revealing a conserved role for enhanced MHC-II stability after DC activation by different stimuli.

DOI： 10.1074/jbc.M110.157586

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATL ACAD SCIENCES  

The expression and turnover of MHC class II-peptide complexes (pMHC-II) on the surface of dendritic cells (DCs) is essential for their ability to activate CD4 T cells efficiently. The half-life of surface pMHC-II is significantly greater in activated (mature) DCs than in resting (immature) DCs, but the molecular mechanism leading to this difference remains unknown. We now show that ubiquitination of pMHC-II by the E3 ubiquitin ligase membrane-associated RING-CH 1 (March-I) regulates surface expression, intracellular distribution, and survival of pMHC-II in DCs. DCs isolated from MarchI- KO mice express very high levels of pMHC-II on the plasma membrane even before DC activation. Although ubiquitination does not affect the kinetics of pMHC-II endocytosis from the surface of DCs, the survival of pMHC-II is enhanced in DCs obtained from March-I-deficient and MHC-II ubiquitination-mutant mice. Using pMHC-II-specific mAb, we show that immature DCs generate large amounts of pMHC-II that are remarkably stable under conditions in which pMHC-II ubiquitination is blocked. Thus, the cellular distribution and stability of surface pMHC-II in DCs is regulated by ubiquitin-dependent degradation of internalized pMHC-II.

DOI： 10.1073/pnas.1010990107

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

We investigated IgE-mediated allergic responses in a metabolic syndrome model rat strain, SHRSP.Z, which develops obesity and hypertension to cast light on the relationship between metabolic disturbances and allergic responses. IgE-mediated cutaneous anaphylactic responses were severely attenuated in this strain regardless of the presence of fa/fa mutation, compared with the parental WKY/Izm strain. Furthermore, in the peritoneal mast cells of both the SHRSP.Z and SHRSP/Izm strains, IgE-mediated activation, such as degranulation and protein tyrosine phosphorylation, was severely impaired whereas no significant differences were found in morphology and number of peritoneal mast cells. Immunoblot analyses revealed that phosphorylation levels of Syk upon IgE-mediated antigen stimulation were significantly decreased and basal expression of linker for activation of T cells (LAT) was down-regulated in peritoneal mast cells of the SHRSP strains. These results suggest that attenuated cutaneous allergic responses in the SHRSP.Z strain might be attributed to impaired Fc epsilon RI-mediated signal transduction in mast cells. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.imlet.2009.11.007

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATURE PUBLISHING GROUP  

By using the recently established culture system that reproduces the terminal differentiation process of connective tissue-type mast cells, we found significant transcriptional induction of CD44. As CD44 is a primary receptor for hyaluronan (HA), which is one of the major extracellular matrix components, we investigated the role of CD44 in cutaneous mast cells. When co-cultured with fibroblasts, mouse bone marrow-derived cultured mast cells (BMMCs) were found to form clusters in an HA-dependent manner. As compared with BMMCs derived from the wild-type mice, those from the CD44(-/-) mice exhibited impaired growth during the co-cultured period. Furthermore, in the peritoneal cavities and ear tissues, mature mast cells were fewer in number in the CD44(-/-) mice than in the wild-type mice. We investigated roles of CD44 in mast cell proliferation by reconstituting BMMCs into the tissues of mast cell-deficient, Kit(W)/Kit(W-v) mice, and found that the number of metachromatic cells upon acidic toluidine blue staining in the tissues transplanted with CD44(-/-) BMMCs was not significantly changed for 10 weeks, whereas that in the tissues transplanted with the CD44(+/+) BMMCs was significantly increased. These results suggest that CD44 plays a crucial role in the regulation of the cutaneous mast cell number.

DOI： 10.1038/labinvest.2008.159

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

To understand physiological roles of tissue mast cells, we established a culture system where bone marrow-derived immature mast cells differentiate into the connective tissue-type mast cell (CTMC)-like cells through modifying the previous co-culture system with Swiss 3T3 fibroblasts. Our system was found to reproducibly mimic the differentiation of CTMCs on the basis of several criteria, such as granule maturation and sensitivity to cationic secretagogues. The gene expression pro. le obtained by the microarray analyses was found to reflect many aspects of the differentiation. Our system is thus helpful to gain deeper insights into terminal differentiation of CTMCs. (C) 2008 Published by Elsevier B. V. on behalf of the Federation of European Biochemical Societies.

DOI： 10.1016/j.febslet.2008.03.033

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

(L)-Histidine decarboxylase (HDC) is the rate-limiting enzyme for histamine synthesis in mammals. Although accumulating evidence has indicated the post-translational processing of HDC, it remains unknown what kinds of proteases are involved. We investigated the processing of HDC in a mouse mastocytoma, P-815, using a lentiviral expression system. HDC was expressed as a 74-kDa precursor form, which is cleaved to yield the 55- and 60-kDa forms upon treatment with butyrate. Alanine-scanning mutations revealed that two tandem aspartate residues (Asp(517) -Asp(518), Asp(550)- Asp(551)) are critical for the processing. Treatment with butyrate caused an increase in the enzyme activity of the cells expressing the wild type HDC, but not in the cells expressing the processing-incompetent mutant. An increase in histamine synthesis by butyrate was accompanied by formation of the 55- and 60-kDa form of HDC. In addition, the in vitro translated 74-kDa form of HDC was found to undergo a limited cleavage by purified human caspase-9, whereas the alanine-substituted mutants were not. Processing and enzymatic activation of HDC in P-815 cells was enhanced in the presence of a Zn2+ chelator, TPEN. Although treatment with butyrate and TPEN drastically augmented the protease activity of caspase-3, and -9, no apoptotic cell death was observed. Both enzymatic activation and processing of HDC were completely suppressed by a pan-caspase inhibitor, partially but significantly by a specific inhibitor for caspase-9, but not by a caspase-3 inhibitor. These results suggest that, in P-815 cells, histamine synthesis is augmented through the post-translational cleavage of HDC, which is mediated by caspase-9.

DOI： 10.1074/jbc.M609943200

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：BIRKHAUSER VERLAG AG  

Objective: We previously demonstrated that, when expressed in COS-7 cells, L-histidine decarboxylase (HDC), which has neither an amino terminal signal sequence nor a hydrophobic membrane anchor, was localized in the endoplasmic reticulum (ER), although its orientation in the membrane remains to be clarified.
Methods & Results: Protease digestion and immunofluorescence analyses of the cells, of which plasma membrane was selectively permeabilized, revealed that the amino terminal 50-kDa portion of HDC is hardly accessible to proteases and antibodies added exogenously from the cytosolic side. Green fluorescent protein fused with the carboxyl terminal 20-kDa region of HDC at its carboxyl terminus exhibited the same characteristics as native HDC.
Conclusion: These results indicate that HDC is tightly associated with the ER membrane with its carboxyl terminal region exposed on the cytosolic side.

DOI： 10.1007/s00011-006-0069-x

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1074/jbc.M506351200

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACADEMIC PRESS INC ELSEVIER SCIENCE  

Accumulating evidence indicates that histamine is involved in the modulation of cytokine expression patterns. We previously reported that daily treatment with the H-2 receptor antagonist, cimetidine, suppressed tumor growth through alteration of the local cytokine expression pattern. In this study, we used a mouse strain genetically lacking histidine decarboxylase (HDC), to evaluate the role of endogenous histamine synthesis on cytokine expression and tumor development. In the mutant mice, cimetidine had no effect on tumor growth, whereas an H-2 agonist, dimaprit, significantly enhanced tumor growth. When the HDC-deficient mice were implanted with mutant CT-26 cells stably expressing HDC, drastic suppression of tumor growth by cimetidine was observed, which was accompanied by augmentation of mRNA expression of LT-beta, TNF-alpha, and IFN-gamma in the tumor tissues. These results suggest that endogenous histamine synthesis in tumor tissues suppresses local tumor immunity via the H2 receptors, resulting in tumor growth promotion. (C) 2002 Elsevier Science (USA). All rights reserved.

DOI： 10.1016/S0006-291X(02)02360-4

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：AMER ASSOC IMMUNOLOGISTS  

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