PubMed Health⌕ Search

Biomedical subjects

Jun-ichiro Inoue

Publications and source records attributed to Jun-ichiro Inoue.

At least 19 recordsLinked to original sources
PubMed2006

Vertex corrections to the anomalous Hall effect in spin-polarized two-dimensional electron gases with a Rashba spin-orbit interaction.

We study the effect of disorder on the intrinsic anomalous Hall conductivity in a magnetic two-dimensional electron gas with a Rashba-type spin-orbit interaction. We find that anomalous Hall conductivity vanishes unless the lifetime is spin-dependent, similar to the spin Hall conductivity in the nonmagnetic system. In addition, we find that the spin Hall conductivity does not vanish in the presence of magnetic scatterers.

Journal Article↗
PubMed2006

Biological evaluation, chelation, and molecular modeling studies of novel metal-chelating inhibitors of NF-kappaB-DNA binding: structure activity relationships.

Previously, we have reported that aurintricarboxylic acid (ATA) is one of the most potent inhibitors of the DNA binding of transcription factor NF-kappaB. We now report the NF-kappaB-DNA binding inhibitory activity of ATA analogues. An electrophoretic mobility shift assay has shown that bromopyrogallol red (BPR) is the most effective inhibitor of NF-kappaB-DNA binding among the studied analogues. The molecular modeling studies showed that BPR makes a strong network of hydrogen bonds with the DNA-binding region of the p50 subunit of NF-kappaB and has electronegative potential on its peripheral surface. Because zinc has been reported to influence the DNA binding of NF-kappaB, the interaction of these analogues with zinc was studied. Chemical speciation and formation-constant studies showed that BPR forms the most stable 1:1 complex with zinc. BPR has also been found to be the most potent antioxidant among the studied analogues.

Antiviral Agents↗
PubMed2006

IL-18 produced by thymic epithelial cells induces development of dendritic cells with CD11b in the fetal thymus.

Thymic dendritic cells (DCs) are suggested to be involved in T cell selection; however, their exact origin and function remain to be established. Although DCs in the adult thymus are mostly CD8alpha(+)CD11b(-), we found that CD8alpha(-)CD11b(+) DCs were abundantly present in the fetal thymus and they possessed antigen-presenting activity. Interestingly, these CD11b(+) DCs were significantly decreased in mice deficient for TNFR-associated factor 6 (TRAF6), a key signaling molecule downstream of IL-1 and tumor necrosis factor-alpha that have been known to induce DCs from intra-thymic precursor cells. CD11b(+) DCs were induced from CD4(-)CD8(-) thymocytes by fetal thymic epithelial cells (TECs). Analysis of cytokine expression in TECs revealed that none of the cytokines previously shown to induce DCs were expressed. Instead, we found strong expression of IL-18 that transmits signals through TRAF6. IL-18 induced CD11b(+) DCs from CD4(-)CD8(-) thymocytes in vitro, which exhibited strong antigen-presenting activity and formed conjugates with CD4(+)CD8(+) T cells efficiently. Taken together, these results strongly suggest that CD11b(+) DCs are differentiated from CD4(-)CD8(-) thymocytes by IL-18 produced from TECs and that they are involved in T cell selection in the fetal thymus.

Animals↗
PubMed2006

Involvement of TNF receptor-associated factor 6 in IL-25 receptor signaling.

IL-25 (IL-17E) induces IL-4, IL-5, and IL-13 production from an unidentified non-T/non-B cell population and subsequently induces Th2-type immune responses such as IgE production and eosinophilic airway inflammation. IL-25R is a single transmembrane protein with homology to IL-17R, but the IL-25R signaling pathways have not been fully understood. In this study, we investigated the signaling pathway under IL-25R, especially the possible involvement of TNFR-associated factor (TRAF)6 in this pathway. We found that IL-25R cross-linking induced NF-kappaB activation as well as ERK, JNK, and p38 activation. We also found that IL-25R-mediated NF-kappaB activation was inhibited by the expression of dominant negative TRAF6 but not of dominant negative TRAF2. Furthermore, IL-25R-mediated NF-kappaB activation, but not MAPK activation, was diminished in TRAF6-deficient murine embryonic fibroblast. In addition, coimmunoprecipitation assay revealed that TRAF6, but not TRAF2, associated with IL-25R even in the absence of ligand binding. Finally, we found that IL-25R-mediated gene expression of IL-6, TGF-beta, G-CSF, and thymus and activation-regulated chemokine was diminished in TRAF6-deficient murine embryonic fibroblast. Taken together, these results indicate that TRAF6 plays a critical role in IL-25R-mediated NF-kappaB activation and gene expression.

Animals↗
PubMed2005

Dependence of self-tolerance on TRAF6-directed development of thymic stroma.

The microenvironments of the thymus are generated by thymic epithelial cells (TECs) and are essential for inducing immune self-tolerance or developing T cells. However, the molecular mechanisms that underlie the differentiation of TECs and thymic compartmentalization are not fully understood. Here we show that deficiency in the tumor necrosis factor receptor-associated factor (TRAF) 6 results in disorganized distribution of medullary TECs (mTECs) and the absence of mature mTECs. Engraftment of thymic stroma of TRAF6(-/-) embryos into athymic nude mice induced autoimmunity. Thus, TRAF6 directs the development of thymic stroma and represents a critical point of regulation for self-tolerance and autoimmunity.

Animals↗
PubMed2005

RANK-mediated amplification of TRAF6 signaling leads to NFATc1 induction during osteoclastogenesis.

RANK and CD40 activate NF-kappaB and MAPKs to similar levels via TRAF6. Even though overexpression of TRAF6 results in osteoclast formation, RANK but not CD40 promotes osteoclastogenesis. To understand the molecular basis for RANK-specific activity in osteoclastogenesis, we created an osteoclast formation system driven by anti-human CD40 antibody-mediated stimulation of a chimeric receptor, h40/mRK, which consists of the extracellular domain of human CD40 and the transmembrane and cytoplasmic domains of mouse RANK. By introducing mutations into three TRAF6-binding sites of RANK, we found that h40/mRK with a single TRAF6-binding site efficiently induced Ca2+ oscillation and expression of NFATc1, a master switch in osteoclastogenesis, whereas CD40 carrying a single TRAF6-binding site did not. However, expression of CD40 that was approximately 100 times greater than that of h40/mRK resulted in osteoclast formation, indicating that the RANK-TRAF6 signal is more potent than the CD40-TRAF6 signal in terms of NFATc1 activation and osteoclastogenesis. These results suggest that RANK may harbor a specific domain that amplifies TRAF6 signaling.

Animals↗
PubMed2005

Inhibitory activity of polyhydroxycarboxylate chelators against recombinant NF-kappaB p50 protein-DNA binding.

The inhibitory effect of 7,8-dihydroxy-4-methylcoumarin (7,8-DHMC), 5,7-dihydroxy-4-methylcoumarin (5,7-DHMC), and gallic acid on the DNA binding of recombinant p50 protein and their interaction with zinc ion were studied. Electrophoretic mobility shift assay (EMSA) using p50 and biotin labeled DNA has shown that gallic acid is more effective than the dihydroxycoumarins in inhibiting the p50-DNA binding. Molecular modeling studies suggest an explanation for these observations. Effect of the addition of zinc after p50-DNA-binding inhibition by gallic acid was also studied. Chemical speciation and formation constant studies show that gallic acid forms a more stable 1:1 complex with zinc ion in comparison to the dihydroxycoumarins.

Cations, Divalent↗
PubMed2005

Identification of DRG family regulatory proteins (DFRPs): specific regulation of DRG1 and DRG2.

DRG1 and DRG2 comprise a highly conserved subfamily of GTP-binding proteins and are thought to act as critical regulators of cell growth. Their abnormal expressions may trigger cell transformation or cell cycle arrest. Our aim is to clarify their physiological functions and regulatory mechanisms. Here we report identification of novel proteins, DRG family regulatory protein (DFRP) 1 and DFRP2, which regulate expression of DRG proteins through specific binding. In transient transfection experiments, DFRP1 specifically binds DRG1, and DFRP2 preferentially binds DRG2. DFRPs provide stability to the target DRG proteins through physical association, possibly by blocking the poly-ubiquitination that would precede proteolysis of DRG proteins. DFRPs are highly conserved in eucaryotes, and the expression patterns of dfrp1 and drg1 transcripts in Xenopus embryos and tissues are similar, indicating that these genes work cooperatively in various types of eukaryotic cells. Immunofluorescence experiments have revealed that the interaction between DRG1 and DFRP1 may occur in the cytoplasm. We generated dfrp1- knockout cells and found that endogenous expression of DRG1 is regulated by DFRP1, confirming that DFRP1 is a specific up-regulator of DRG1 in vivo. On the basis of these results, we propose that DRG1 and DRG2 are regulated differently despite their structural similarities.

Amino Acid Sequence↗
PubMed2005

Interaction of anti-proliferative protein Tob with poly(A)-binding protein and inducible poly(A)-binding protein: implication of Tob in translational control.

Tob is a member of an emerging family of anti-proliferative proteins that suppress cell growth when over-expressed. tob mRNA is highly expressed in anergic T cells and over-expression of Tob suppresses transcription of interleukin-2 (IL-2) through its interaction with Smads. Here, we identified two types of cDNA clones coding for poly(A)-binding protein (PABP) and inducible PABP (iPABP) by screening an expression cDNA library with the GST-Tob probe. Co-immunoprecipitation and GST-pull down experiments showed that Tob associated with the carboxyl-terminal region of iPABP. We then found that iPABP, like PABP, was involved in regulation of translation: iPABP enhanced translation of IL-2 mRNA in vitro. The enhanced translation of IL-2 mRNA required the 3'UTR and poly(A) sequences. Tob abrogated the enhancement of translation through its interaction with carboxyl-terminal region of iPABP in vitro. Consistently, over-expression of Tob in NIH3T3 cells, in which exogenous iPABP was stably expressed, resulted in suppression of IL-2 production from the simultaneously transfected IL-2 expression plasmid. Finally, Tob, whose expression was induced by anergic stimulation, was co-immunoprecipitated with iPABP in human T cells. These findings suggest that Tob is involved in the translational suppression of IL-2 mRNA in anergic T cells through its interaction with iPABP.

3' Untranslated Regions↗
PubMed2004

Evans Blue is an inhibitor of nuclear factor-kappa B (NF-kappaB)-DNA binding.

Nuclear factor-kappa B (NF-kappaB) is an important transcription factor, involved in many immune and inflammatory responses. It is critical in HIV gene expression as it has kappa B binding sites in the HIV-1 long-terminal repeat. Hence, targeting NF-kappaB to prevent its DNA binding holds a significant therapeutic potential. In this context, we report Evans Blue as a novel inhibitor of NF-kappaB-DNA binding. Evans Blue was found to be inhibiting DNA binding of NF-kappaB at a low concentration of 100 microM. Further, molecular modeling studies using docking and generation of electrostatic potential maps predicted a possible binding mode of EB to the DNA binding region of NF-kappaB, consistent with the experimental activity.

Cell Nucleus↗
PubMed2004

Neurotrophin signaling through the p75 receptor is deficient in traf6-/- mice.

Activation of the neurotrophin receptor p75 has been shown to elicit opposing cellular signals. Depending on the context of the cell, p75 will either promote survival or induce apoptosis after neurotrophin stimulation. p75-induced apoptosis occurs through activation of c-Jun N-terminal kinase (JNK), whereas the survival signal is mediated by nuclear factor kappaB (NFkappaB). The receptor proximal signals that produce these responses are unknown, although several molecules have been identified that associate with the intracellular domain of p75. One such interactor, TRAF6, a member of the tumor necrosis factor receptor-associated factor family, has been implicated in p75 signaling. To assess the role of TRAF6 in p75 signaling, we analyzed mice with this gene deleted. In Schwann cells isolated from traf6+/+ animals, NGF elicited an 80% increase in transcription of an NFkappaB reporter; however, in traf6-/- cells, the NGF response was abrogated. Similarly, NGF activation of JNK was not apparent in Schwann cells from mice lacking traf6. Deficiencies in p75 signaling in traf6-/- animals resulted in a loss of p75-mediated apoptosis. In sympathetic neurons cultured from traf6+/+ superior cervical ganglia (SCGs), there was an increase in JNK activation and apoptosis after BDNF binding to p75; however, traf6-/- neurons did not respond. In vivo during naturally occurring cell death, there was a 55.6% reduction in TUNEL (terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling)-positive cells in the SCG of postnatal day 4 traf6-/- animals relative to traf6+/+ littermates. These results indicate that TRAF6 plays an essential role in mediating p75 signal transduction and induction of apoptosis.

Animals↗
PubMed2004

Interferon-alpha induction through Toll-like receptors involves a direct interaction of IRF7 with MyD88 and TRAF6.

Toll-like receptors (TLRs) are involved in the recognition of microbial pathogens. A subset of TLRs, TLR7, TLR8 and TLR9, induces antiviral responses by producing interferon-alpha (IFN-alpha). Production of IFN-alpha is dependent on the Toll-interleukin-1 receptor domain-containing adaptor MyD88. Here we show that MyD88 formed a complex with the transcription factor IRF7 but not with IRF3. The death domain of MyD88 interacted with an inhibitory domain of IRF7, and this interaction resulted in activation of the IFN-alpha-dependent promoters. Furthermore, the adaptor molecule TRAF6 also bound and activated IRF7. Ubiquitin ligase activity of TRAF6 was required for IRF7 activation. These results indicate that TLR-mediated IFN-alpha induction requires the formation of a complex consisting of MyD88, TRAF6 and IRF7 as well as TRAF6-dependent ubiquitination.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Cutting edge: TNFR-associated factor (TRAF) 6 is essential for MyD88-dependent pathway but not toll/IL-1 receptor domain-containing adaptor-inducing IFN-beta (TRIF)-dependent pathway in TLR signaling.

Signaling pathways from TLRs are mediated by the Toll/IL-1R (TIR) domain-containing adaptor molecules. TNF receptor-associated factor (TRAF) 6 is thought to activate NF-kappaB and MAPKs downstream of these TIR domain-containing proteins to induce production of inflammatory cytokines. However, the precise role of TRAF6 in signaling from individual TLRs has not been appropriately addressed. We analyzed macrophages from TRAF6-deficient mice and made the following observations. In the absence of TRAF6, 1) ligands for TLR2, TLR5, TLR7, and TLR9 failed to induce activation of NF-kappaB and MAPKs or production of inflammatory cytokines; 2) TLR4 ligand-induced cytokine production was remarkably reduced and activation of NF-kappaB and MAPKs was observed, albeit with delayed kinetics; and 3) in contrast with previously reported findings, TLR3 signaling was not affected. These results indicate that TRAF6 is essential for MyD88-dependent signaling but is not required for TIR domain-containing adaptor-inducing IFN-beta (TRIF)-dependent signaling.

Adaptor Proteins, Signal Transducing↗
PubMed2004

TIFAB inhibits TIFA, TRAF-interacting protein with a forkhead-associated domain.

Tumor necrosis factor receptor-associated factor 6 (TRAF6) transduces signals that lead to activation of NFkappaB and AP-1, which is essential for cell differentiation and establishment of the immune and inflammatory systems. TRAF-interacting protein with a forkhead-associated domain (TIFA) was identified as a TRAF6-binding protein that could link IRAK-1 to TRAF6 and then activate TRAF6 upon stimulation. We report identification of a TIFA-related protein, TIFAB, that inhibits TIFA-mediated activation of NFkappaB. TIFAB does not associate with members of the TRAF family but does bind TIFA. We analyzed the effect of TIFAB expression on the TRAF6/TIFA interaction by immunoprecipitation of TRAF6 and found that TIFA coprecipitated with TRAF6 was not changed. However, when we analyzed this interaction by immunoprecipitation of TIFA, we found that TIFAB significantly increased the amount of TRAF6 coprecipitated with TIFA. These findings suggest that TIFAB inhibits the TIFA-mediated TRAF6 activation possibly by inducing a conformational change in TIFA.

Amino Acid Sequence↗
PubMed2004

Critical roles of c-Jun signaling in regulation of NFAT family and RANKL-regulated osteoclast differentiation.

Receptor activator of NF-kappaB ligand (RANKL) plays an essential role in osteoclast formation and bone resorption. Although genetic and biochemical studies indicate that RANKL regulates osteoclast differentiation by activating receptor activator of NF-kappaB and associated signaling molecules, the molecular mechanisms of RANKL-regulated osteoclast differentiation have not yet been fully established. We investigated the role of the transcription factor c-Jun, which is activated by RANKL, in osteoclastogenesis using transgenic mice expressing dominant-negative c-Jun specifically in the osteoclast lineage. We found that the transgenic mice manifested severe osteopetrosis due to impaired osteoclastogenesis. Blockade of c-Jun signaling also markedly inhibited soluble RANKL-induced osteoclast differentiation in vitro. Overexpression of nuclear factor of activated T cells 1 (NFAT1) (NFATc2/NFATp) or NFAT2 (NFATc1/NFATc) promoted differentiation of osteoclast precursor cells into tartrate-resistant acid phosphatase-positive (TRAP-positive) multinucleated osteoclast-like cells even in the absence of RANKL. Overexpression of NFAT1 also markedly transactivated the TRAP gene promoter. These osteoclastogenic activities of NFAT were abrogated by overexpression of dominant-negative c-Jun. Importantly, osteoclast differentiation and induction of NFAT2 expression by NFAT1 overexpression or soluble RANKL treatment were profoundly diminished in spleen cells of the transgenic mice. Collectively, these results indicate that c-Jun signaling in cooperation with NFAT is crucial for RANKL-regulated osteoclast differentiation.

Adenoviridae↗
PubMed2003

MIP-T3 associates with IL-13Ralpha1 and suppresses STAT6 activation in response to IL-13 stimulation.

To unravel the mechanism of interleukin-13 (IL-13)-specific functions, we sought to identify IL-13 receptor (IL-13R) binding molecules. A novel human IL-13Ralpha1 binding protein (IL13RBP1) has been identified using yeast tri-hybrid system, which was found to encode the same protein as MIP-T3 (microtubule interacting protein that associates with tumor necrosis factor (TNF) receptor associating factor-3 (TRAF3)). It constitutively associates with IL-13Ralpha1 and suppresses IL-4/13-induced signal transducer and activator of transcription-6 (STAT6) phosphorylation. IL-13-induced STAT6 activation was also inhibited as determined by dual luciferase assay and electrophoretic mobility shift assay (EMSA). These results suggest that MIP-T3 is a novel inhibitor of IL-13 signaling and may be a useful molecule in ameliorating various conditions in which IL-13 plays a central role.

Animals↗
PubMed2003

Elimination of the vertebrate Escherichia coli Ras-like protein homologue leads to cell cycle arrest at G1 phase and apoptosis.

Homologues of the Escherichia coli (E. coli) Ras-like protein (ERA), a GTP-binding protein with RNA binding activity, have recently been found in various species, including human, mouse, and Antirrhinum majus. Depletion of prokaryotic ERA blocks cell division without affecting chromosome segregation. However, the physiological function of eukaryotic ERA is largely unknown. We have performed a genetic analysis of chicken ERA (GdERA) in DT40 cells. Depletion of GdERA diminished the growth rate of the cells, accompanied by an accumulation of apoptotic cells. The analysis of cell cycle indicates that the elimination of GdERA caused arrest at G1 phase, but not at M phase, which highlights the distinct role of vertebrate ERA in the cell cycle progression compared to prokaryotic ERA. Furthermore, human ERA (HsERA) rescued the phenotype of GdERA-deficient cells, whereas a mutant of HsERA deprived of RNA-binding activity did not. These data suggest that vertebrate ERA regulates the G1 phase progression via an as yet unknown molecular mechanism, which involves RNA recognition by ERA.

Animals↗