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Toshiyuki Takai

Publications and source records attributed to Toshiyuki Takai.

At least 19 recordsLinked to original sources
PubMed2007

Dual assemblies of an activating immune receptor, MAIR-II, with ITAM-bearing adapters DAP12 and FcRgamma chain on peritoneal macrophages.

Certain activating immune receptors expressed on myeloid cells noncovalently associate with either DAP12 or FcepsilonRIgamma (FcRgamma chain), the ITAM-bearing transmembrane adapter proteins. An activating receptor, myeloid-associated Ig-like receptor (MAIR) II, is expressed on a subset of B cells and macrophages in the spleen and peritoneal cavity of mice and associates with DAP12 in these cells. However, we demonstrate here that cross-linking MAIR-II with mAb induced secretion of a significant amount of the inflammatory cytokines TNF-alpha and IL-6 from DAP12(-/-) as well as wild-type (WT) peritoneal macrophages. We show that MAIR-II associates with not only DAP12 but also FcRgamma chain homodimers in peritoneal macrophages. LPS enhanced the FcRgamma chain expression and FcRgamma chain-dependent cell surface expression of MAIR-II and had additive effects on MAIR-II-mediated inflammatory cytokine secretion from peritoneal macrophages. The lysine residue in the transmembrane region of MAIR-II was involved in the association with FcRgamma chain as well as DAP12. Our findings present the first case of an activating receptor that uses either DAP12 or FcRgamma chain as a signaling adapter. The FcRgamma chain may provide cooperation with and/or compensation for DAP12 in MAIR-II-mediated inflammatory responses by peritoneal macrophages.

Adaptor Proteins, Signal Transducing↗
PubMed2007

Critical role of the Fc receptor gamma-chain on APCs in the development of allergen-induced airway hyperresponsiveness and inflammation.

The FcR common gamma-chain (FcRgamma) is an essential component of the receptors FcepsilonRI, FcgammaRI, and FcgammaRIII, which are expressed on many inflammatory cell types. The role of these receptors in the initiation or maintenance of allergic inflammation has not been well defined. FcRgamma-deficient (FcRgamma(-/-)) and control (wild-type (WT)) mice were sensitized and subsequently challenged with OVA. Following sensitization and challenge to OVA, FcRgamma-deficient (FcRgamma(-/-)) mice developed comparable levels of IgE and IgG1 as WT mice. However, numbers of eosinophils, levels of IL-5, IL-13, and eotaxin in bronchoalveolar lavage fluid, and mononuclear cell (MNC) proliferative responses to OVA were significantly reduced, as was airway hyperresponsiveness (AHR) to inhaled methacholine. Reconstitution of FcRgamma(-/-) mice with whole spleen MNC from WT mice before sensitization restored development of AHR and the numbers of eosinophils in bronchoalveolar lavage fluid; reconstitution after sensitization but before OVA challenge only partially restored these responses. These responses were also restored when FcRgamma(-/-) mice received T cell-depleted MNC, T and B cell-depleted MNC, or bone marrow-derived dendritic cells before sensitization from FcR(+/+) or FcgammaRIII-deficient but not FcRgamma(-/-) mice. The expression levels of FcgammaRIV on bone marrow-derived dendritic cells from FcR(+/+) mice were found to be low. These results demonstrate that expression of FcRgamma, most likely FcgammaRI, on APCs is important during the sensitization phase for the development of allergic airway inflammation and AHR.

Allergens↗
PubMed2006

Regulation of osteoclast differentiation and function by the CaMK-CREB pathway.

Calcium (Ca(2+)) signaling is essential for a variety of cellular responses and higher biological functions. Ca(2+)/calmodulin-dependent kinases (CaMKs) and the phosphatase calcineurin activate distinct downstream pathways that are mediated by the transcription factors cAMP response element (CRE)-binding protein (CREB) and nuclear factor of activated T cells (NFAT), respectively. The importance of the calcineurin-NFAT pathway in bone metabolism has been demonstrated in osteoclasts, osteoblasts and chondrocytes. However, the contribution of the CaMK-CREB pathway is poorly understood, partly because of the difficulty of dissecting the functions of homologous family members. Here we show that the CaMKIV-CREB pathway is crucial for osteoclast differentiation and function. Pharmacological inhibition of CaMKs as well as the genetic ablation of Camk4 reduced CREB phosphorylation and downregulated the expression of c-Fos, which is required for the induction of NFATc1 (the master transcription factor for osteoclastogenesis) that is activated by receptor activator of NF-kappaB ligand (RANKL). Furthermore, CREB together with NFATc1 induced the expression of specific genes expressed by differentiated osteoclasts. Thus, the CaMK-CREB pathway biphasically functions to regulate the transcriptional program of osteoclastic bone resorption, by not only enhancing induction of NFATc1 but also facilitating NFATc1-dependent gene regulation once its expression is induced. This provides a molecular basis for a new therapeutic strategy for bone diseases.

Animals↗
PubMed2006

Vav1 controls DAP10-mediated natural cytotoxicity by regulating actin and microtubule dynamics.

The NK cell-activating receptor NKG2D recognizes several MHC class I-related molecules expressed on virally infected and tumor cells. Human NKG2D transduces activation signals exclusively via an associated DAP10 adaptor containing a YxNM motif, whereas murine NKG2D can signal through either DAP10 or the DAP12 adaptor, which contains an ITAM sequence. DAP10 signaling is thought to be mediated, at least in part, by PI3K and is independent of Syk/Zap-70 kinases; however, the exact mechanism by which DAP10 induces natural cytotoxicity is incompletely understood. Herein, we identify Vav1, a Rho GTPase guanine nucleotide exchange factor, as a critical signaling mediator downstream of DAP10 in NK cells. Specifically, using mice deficient in Vav1 and DAP12, we demonstrate an essential role for Vav1 in DAP10-induced NK cell cytoskeletal polarization involving both actin and microtubule networks, maturation of the cytolytic synapse, and target cell lysis. Mechanistically, we show that Vav1 interacts with DAP10 YxNM motifs through the adaptor protein Grb2 and is required for activation of PI3K-dependent Akt signaling. Based on these findings, we propose a novel model of ITAM-independent signaling by Vav downstream of DAP10 in NK cells.

Actins↗
PubMed2006

Establishment and functional characterization of novel natural killer cell lines derived from a temperature-sensitive SV40 large T antigen transgenic mouse.

Natural killer (NK) cells belong to an important lymphocyte population that eliminates transformed cells and invading pathogens without any prior sensitization. NK cells possess not only natural killing activity against non-self and altered-self cells but also exhibit cytokine production and antibody-dependent cell-mediated cytotoxicity (ADCC). Despite their important roles in the innate immune system, little is known about the details of NK cell biology. In spite of that several murine NK cell clones have been established, studies have mainly focused on their natural killing activity but not their cytokine production or ADCC. In this study, we established and characterized eight novel, immortalized murine NK cell clones derived from a temperature-sensitive SV40 large-T antigen transgenic mouse. These NK cell lines continuously proliferated for more than 30 months in a culture medium supplemented with interleukin 2. All cell lines contained azurophilic granules in the cytoplasm, and a few clones retained the NK cell functions, such as natural killing activity, cytokine production, and ADCC. In addition, one clone could serve as a host for transient as well as stable gene transfection. Taken together, these findings indicate that the cell lines could constitute useful tools for detailed analysis of murine NK cell biology.

Animals↗
PubMed2006

Novel mast cell lines with enhanced proliferative and degranulative abilities established from temperature-sensitive SV40 large T antigen transgenic mice.

Mast cells (MCs) play crucial roles in innate immunity to parasitic and bacterial infections as well as in hypersensitivity, such as the induction and exacerbation of allergy and autoimmune diseases. The regulatory mechanisms for MC development and effector functions are of great interest for developing novel therapeutic strategies against such disorders. Here we report the establishment of novel, immortalized MC lines from bone marrow (BM) cells of a temperature-sensitive mutant of SV40 large T antigen-transgenic mice (termed SVMCs). BM cells from tsSV40LT mice were cultured in the presence of interleukin (IL)-3 for 3 weeks, and then subjected to limiting dilution and single-cell cloning, yielding 27 independent MC clones, three of which were subjected to further analysis. On culture with nerve growth factor, stem cell factor and IL-3, these SVMC clones showed morphologic and biochemical changes from mucosal MC-like to connective-tissue MC-like phenotypes. These SVMC lines exhibited a significantly enhanced proliferation rate, and a higher responsiveness to the high affinity Fc receptor for IgE-mediated intracellular calcium mobilization and degranulation than those of BM-derived cultured MCs. These cell lines should facilitate studies on the mechanisms for the development, differentiation and effector functions of MCs in health and diseases.

Animals↗
PubMed2006

Plexin-A1 and its interaction with DAP12 in immune responses and bone homeostasis.

Semaphorins and their receptors have diverse functions in axon guidance, organogenesis, vascularization and/or angiogenesis, oncogenesis and regulation of immune responses. The primary receptors for semaphorins are members of the plexin family. In particular, plexin-A1, together with ligand-binding neuropilins, transduces repulsive axon guidance signals for soluble class III semaphorins, whereas plexin-A1 has multiple functions in chick cardiogenesis as a receptor for the transmembrane semaphorin, Sema6D, independent of neuropilins. Additionally, plexin-A1 has been implicated in dendritic cell function in the immune system. However, the role of plexin-A1 in vivo, and the mechanisms underlying its pleiotropic functions, remain unclear. Here, we generated plexin-A1-deficient (plexin-A1(-/-)) mice and identified its important roles, not only in immune responses, but also in bone homeostasis. Furthermore, we show that plexin-A1 associates with the triggering receptor expressed on myeloid cells-2 (Trem-2), linking semaphorin-signalling to the immuno-receptor tyrosine-based activation motif (ITAM)-bearing adaptor protein, DAP12. These findings reveal an unexpected role for plexin-A1 and present a novel signalling mechanism for exerting the pleiotropic functions of semaphorins.

Adaptor Proteins, Signal Transducing↗
PubMed2006

Genotypic difference in canopy diffusive conductance measured by a new remote-sensing method and its association with the difference in rice yield potential.

There have been few practical ways of measuring physiological determinants of rice yield. Rapid evaluation of yield determination traits may expedite breeding of high-yielding rice. Here, we report a new remote-sensing technique for the evaluation of canopy ecophysiological status under field conditions developed based on simultaneous measurements of sunlit and suddenly shaded canopy temperatures. This technique has the advantage of instantaneous estimation of aerodynamic resistance (r(a)) and canopy diffusive resistance (r(c) without measuring wind velocity. Canopy diffusive conductance (1 / r(c)) estimated by the remote sensing method was closely related to leaf stomatal conductance (g(s)) measured with a portable gas exchange system. This result supported the validity of this new method for quantitative estimation of canopy physiological characteristics. Significant genotypic differences were obtained in canopy-air temperature difference (Tc-Ta), r(c) and 1 / r(c) during the 2-week period preceding full heading for two years, and 1 / r(c) was highly correlated with crop growth rate (CGR), which was closely related to the final yield. These results suggest that 1 / r(c) can be an effective criterion for the selection of high-yielding rice genotypes, and the remote sensing technique proposed here can be a powerful tool for the rapid evaluation of 1 / r(c) under field conditions.

Agriculture↗
PubMed2005

Hydronephrosis associated with antiurothelial and antinuclear autoantibodies in BALB/c-Fcgr2b-/-Pdcd1-/- mice.

Because most autoimmune diseases are polygenic, analysis of the synergistic involvement of various immune regulators is essential for a complete understanding of the molecular pathology of these diseases. We report the regulation of autoimmune diseases by epistatic effects of two immunoinhibitory receptors, low affinity type IIb Fc receptor for IgG (FcgammaRIIB) and programmed cell death 1 (PD-1). Approximately one third of the BALB/c-Fcgr2b(-/-)Pdcd1(-/-) mice developed autoimmune hydronephrosis, which is not observed in either BALB/c-Fcgr2b(-/-) or BALB/c-Pdcd1(-/-) mice. Hydronephrotic mice produced autoantibodies (autoAbs) against urothelial antigens, including uroplakin IIIa, and these antibodies were deposited on the urothelial cells of the urinary bladder. In addition, approximately 15% of the BALB/c-Fcgr2b(-/-)Pdcd1(-/-) mice produced antinuclear autoAbs. In contrast, the frequency of the autoimmune cardiomyopathy and the production of anti-parietal cell autoAb, which were observed in BALB/c-Pdcd1(-/-) mice, were not affected by the additional FcgammaRIIB deficiency. These observations suggest cross talk between two immunoinhibitory receptors, FcgammaRIIB and PD-1, on the regulation of autoimmune diseases.

Animals↗
PubMed2005

Siglec-H is an IPC-specific receptor that modulates type I IFN secretion through DAP12.

Natural interferon (IFN)-producing cells are the primary cell type responsible for production of type I IFN in response to viruses. Herein we report the identification of the first molecular marker of mouse natural interferon-producing cells (IPCs), a novel member of the sialic acid-binding immunoglobulin (Ig)-like lectin (Siglec) family termed Siglec-H. Siglec-H is expressed exclusively on IPCs and is unique among Siglec proteins in that it associates with the adaptor protein DAP12. Moreover, we show that DAP12 modulates the type I IFN response of IPCs to a Toll-like receptor 9 (TLR9) agonist. This observation explains our previous finding that stimulation of IPCs with 440c, a Siglec-H-specific antibody, reduces IPC secretion of type I IFN. Moreover, it supports a model in which engagement of DNAX-activation protein 12 (DAP12)-associated receptors with antibodies or low avidity endogenous ligands interferes with TLR-mediated cellular activation.

Adaptor Proteins, Signal Transducing↗
PubMed2005

DAP12 (KARAP) amplifies inflammation and increases mortality from endotoxemia and septic peritonitis.

DAP12 (KARAP) is a transmembrane signaling adaptor for a family of innate immunoreceptors that have been shown to activate granulocytes and monocytes/macrophages, amplifying production of inflammatory cytokines. Contrasting with these data, recent studies suggest that DAP12 signaling has an inhibitory role in the macrophage response to microbial products (Hamerman, J.A., N.K. Tchao, C.A. Lowell, and L.L. Lanier. 2005. Nat. Immunol. 6:579-586). To determine the in vivo role for DAP12 signaling in inflammation, we measured the response of wild-type (WT) and DAP12-/- mice to septic shock. We show that DAP12-/- mice have improved survival from both endotoxemia and cecal ligation and puncture-induced septic shock. As compared with WT mice, DAP12-/- mice have decreased plasma cytokine levels and a decreased acute phase response during sepsis, but no defect in the recruitment of cells or bacterial control. In cells isolated after sepsis and stimulated ex vivo, DAP12 signaling augments lipopolysaccharide-mediated cytokine production. These data demonstrate that, during sepsis, DAP12 signaling augments the response to microbial products, amplifying inflammation and contributing to mortality.

Acute-Phase Reaction↗
PubMed2005

Time-related mapping of quantitative trait loci controlling grain-filling in rice (Oryza sativa L.).

Grain-filling is a crucial process that determines final grain yield in rice (Oryza sativa L.). To understand the genetic basis of dynamics of grain-filling, quantitative trait locus (QTL) analysis was conducted using time-related phenotypic data on grain-filling collected from a population of 155 recombinant inbred lines (F12), derived from a cross between Milyang 23 and Akihikari. Two QTLs detected on chromosomes 8 and 12 were strongly associated with increased filling percentage per panicle. These QTLs were not linked with those controlling spikelet numbers per panicle. This result confers the possibility of improving grain-filling together with an enlargement of sink size. The QTL for filling percentage per panicle on chromosome 8 exactly overlapped that for non-structural carbohydrate (NSC) content in the culm and leaf sheaths during grain-filling, and the Milyang 23 allele associated with increased grain-filling percentage per panicle was associated with decreased NSC content. Therefore, this QTL may be directly involved in NSC translocation from the culm and leaf sheaths to panicle. In addition, the Milyang 23 alleles of QTLs associated with greater spikelet number per panicle on chromosomes 1 and 6 were also related with a reduction in NSC content in the culm and leaf sheaths during grain-filling. These results indicate that NSC dynamics during grain-filling is partly dependent on sink size. NSC accumulation in the culm and leaf sheaths at the heading stage was mainly controlled by different genetic regulations from NSC dynamics during grain-filling. Nitrogen dynamics during grain-filling may also be involved in carbohydrate dynamics.

Chromosome Mapping↗
PubMed2005

Pathways participating in activation of mouse uterine natural killer cells during pregnancy.

Activated natural killer (NK) cells proliferate in large numbers in murine mesometrial endometrium from Day 6 to Day 12 of gestation (term = 19 gestation days) to become the most abundant uterine lymphocytes. Early human decidua contains analogous CD56+/CD16- cells. Murine uterine (u)NK cells localize to decidua basalis and mesometrial lymphoid aggregate of pregnancy (MLAp). Decidua and MLAp are transient, pregnancy-associated tissues traversed by maternal arteries to the placentas. Uterine NK cells sensitize these arteries, facilitating their structural changes into high-volume conduits by Gestation Day 10 through release of interleukin (IL)-18, interferon (IFN)-gamma, vascular endothelial growth factor (VEGF), and other molecules. Little information exists concerning where, when, or how murine or human uNK cells become activated. In murine lymphoid tissue, three NK cell adaptor-mediated activation pathways are known: FcRgamma/CD3zeta, DNAX-activating protein (DAP) 10, and DAP12 (genes Fcgr3/Cd3z, Hcst, and Tyrobp, respectively). Expression of ligands for these receptors was demonstrated in implantation sites of normal C57BL/6J mice. Then, histological and morphometric analyses of implantation sites in mice with genetic inactivation of each pathway were undertaken. Implantation sites in DAP10-/- (Hcst deleted) mice appeared normal, spiral artery modification occurred, and concentrations of IFN-gamma in MLAp and decidua basalis were similar to those in time-matched C57BL/6J. Implantation sites of FcRgamma-/-/CD3zeta-/- (Fcgr3/Cd3z double knockout), DAP12 (Tyrobp)-loss-of-function-mutant, and FcRgamma-/-/DAP12-/- (Fcgr3/Tyrobp double knockout) mice differentiated abundant but functionally impaired uNK cells that could not modify spiral arteries. These data reveal key importance of FcRgamma-/-/CD3zeta-/- and thus maternal IgG during activation of mouse uNK cells and assign DAP12 but not DAP10 signaling contributions.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Fc receptors and their role in immune regulation and autoimmunity.

The activation threshold of cells in the immune system is often tuned by cell surface molecules. The Fc receptors expressed on various hematopoietic cells constitute critical elements for activating or downmodulating immune responses and combines humoral and cell-mediated immunity. Thus, Fc receptors are the intelligent sensors of the immune status in the individual. However, impaired regulation by Fc receptors will lead to unresponsiveness or hyperreactivity to foreign as well as self-antigens. Murine models for autoimmune disease indicate the indispensable roles of the inhibitory Fc receptor in the suppression of such disorders, whereas activating-type FcRs are crucial for the onset and exacerbation of the disease. The development of many autoimmune diseases in humans may be caused by impairment of the human Fc receptor regulatory system. This review is aimed at providing a current overview of the mechanism of Fc receptor-based immune regulation and the possible scenario of how autoimmune disease might result from their dysfunction.

Animals↗
PubMed2005

The Src family kinases Hck and Fgr negatively regulate neutrophil and dendritic cell chemokine signaling via PIR-B.

In classical descriptions of leukocyte chemokine signaling, Src family kinases are thought to function in a positive fashion by coupling receptor associated Galpha subunits to downstream mitogen activated protein (MAP) kinase activation. However, neutrophils derived from hck-/-fgr-/- mice and dendritic cells (DCs) from fgr-/- animals manifested significantly higher intracellular signaling (Ca2+ flux, MAP kinase activation, actin polymerization) and functional responses (chemotaxis in vitro and migration in vivo) to a number of different chemokines. These kinases may mediate their effect through the inhibitory receptor PIR-B since neutrophils and DCs from pir-b-/- mice were also hyperresponsive to chemokine stimulation. In wild-type (wt) cells dephosphorylation of PIR-B was associated with maximal chemokine signaling, whereas in hck-/-fgr-/- cells PIR-B was unphosphorylated. These data support a model in which the Src family kinases Hck and Fgr function as negative regulators of myeloid cell chemokine signaling by maintaining the tonic phosphorylation of PIR-B.

Animals↗
PubMed2005

A novel recognition system for MHC class I molecules constituted by PIR.

The paired immunoglobulin (Ig)-like receptors (PIRs) represent a typical receptor pair of the Ig-like receptor family in which various combinations of ligand-receptor interaction provide a positive and negative regulation of immune cells, thus enabling those cells to respond properly to extrinsic stimuli. Activating PIR-A and inhibitory PIR-B are expressed in a wide range of cells in the murine immune system, such as B cells, mast cells, macrophages, and dendritic cells, mostly in a pair-wise fashion. PIRs bind to MHC class I molecules expressed ubiquitously on hematopoietic as well as nonhematopoietic cells. The unbalanced binding of PIR-A and PIR-B to MHC class I molecules may lead to the perturbation of cell development, regulation, and function as observed in PIR-B-deficient mice. Thus, PIR-A and PIR-B are indispensable for the regulation of cellular signaling and important for homeostasis of the immune system.

Animals↗