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D Kitamura

Publications and source records attributed to D Kitamura.

At least 37 records · Page 2Linked to original sources
PubMed1997

Direct evidence for the contribution of B cells to the progression of insulitis and the development of diabetes in non-obese diabetic mice.

The non-obese diabetic (NOD) mouse is an excellent animal model of autoimmune diabetes associated with insulitis. The progression of insulitis causes the destruction of pancreatic beta cells, resulting in the development of hyperglycemia. Although it has been well documented that T cells are required for the development of insulitis and diabetes in NOD mice, the importance of B cells remains unclear. To clarify the role of B cells in the pathogenesis of NOD mice, we therefore generated B cell-deficient NOD (B-NOD) mice. Surprisingly, none (of 13) of the B-NOD mice developed diabetes by 40 weeks of age, while the control littermates with B cells (B+NOD) suffered from a high proportion (43 of 49) of diabetes. The insulin reactivity of B+NOD mice was significantly impaired, while the B-NOD mice showed a good insulin response, thus suggesting the pancreatic beta cell function to be well preserved in B-NOD mice. Although B-NOD mice did develop insulitis, the extent of insulitis was significantly suppressed. These data thus provide the direct evidence that B cells are essential for the progression of insulitis and the development of diabetes in NOD mice.

Animals↗
PubMed1996

Impaired locomotor activity and exploratory behavior in mice lacking histamine H1 receptors.

From pharmacological studies using histamine antagonists and agonists, it has been demonstrated that histamine modulates many physiological functions of the hypothalamus, such as arousal state, locomotor activity, feeding, and drinking. Three kinds of receptors (H1, H2, and H3) mediate these actions. To define the contribution of the histamine H1 receptors (H1R) to behavior, mutant mice lacking the H1R were generated by homologous recombination. In brains of homozygous mutant mice, no specific binding of [3H]pyrilamine was seen. [3H]Doxepin has two saturable binding sites with higher and lower affinities in brains of wild-type mice, but H1R-deficient mice showed only the weak labeling of [3H]doxepin that corresponds to lower-affinity binding sites. Mutant mice develop normally, but absence of H1R significantly increased the ratio of ambulation during the light period to the total ambulation for 24 hr in an accustomed environment. In addition, mutant mice significantly reduced exploratory behavior of ambulation and rearings in a new environment. These results indicate that through H1R, histamine is involved in circadian rhythm of locomotor activity and exploratory behavior as a neurotransmitter.

Animals↗
PubMed1996

Characteristics of the mouse genomic histamine H1 receptor gene.

We report here the molecular cloning of a mouse histamine H1 receptor gene. The protein deduced from the nucleotide sequence is composed of 488 amino acid residues with characteristic properties of GTP binding protein-coupled receptors. Our results suggest that the mouse histamine H1 receptor gene is a single locus, and no related sequences were detected. Interspecific backcross analysis indicated that the mouse histamine H1 receptor gene (Hrh1) is located in the central region of mouse Chromosome 6 linked to microphthalmia (Mitfmi), ras-related fibrosarcoma oncogene 1 (Raf1), and ret proto-oncogene (Ret) in a region of homology with human chromosome 3p.

Amino Acid Sequence↗
PubMed1996

Glycosylphosphatidylinositol-anchor-deficient mice: implications for clonal dominance of mutant cells in paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hematopoietic stem cell disorder characterized by complement-mediated hemolysis. Abnormal hematopoietic cells from patients with PNH are deficient in glycosylphosphatidylinositol (GPI)-anchored proteins and clonally dominate various hematopoietic lineages in the bone marrow and the peripheral blood. Analysis of many patients with PNH has showed that somatic mutation in the X-linked gene PIG-A is responsible for the GPI-anchor deficiency in PNH. The PIG-A mutation must also be relevant to the clonal dominance of GPI-anchor deficient (GPI-) blood cells because two or more PIG-A mutant clones become dominant in many patients. However, whether the PIG-A mutation alone is sufficient for clonal dominance is not known. To address this question, we generated chimeric mice using Pig-a (the murine homologue of PIG-A) disrupted embryonic stem (ES) cells, in which the animals are chimeric with respect to the surface expression of GPI-anchored proteins. The chimerism of hematopoietic and nonhematopoietic tissues in such mice was always low, suggesting that the higher contribution of Pig-a disrupted GPI- cells had a lethal effect on the chimera. GPI- cells appeared in the peripheral blood of some of the chimeric mice. However, the percentage of GPI- erythrocytes did not increase for 10 months after birth, implying that the Pig-a mutation alone does not immediately cause the clonal dominance of GPI- blood cells; another pathologic or physiologic change(s) in the hematopoietic environments or in the clone itself may be necessary.

Animals↗
PubMed1996

Immunity to viruses in B cell-deficient mice: influence of antibodies on virus persistence and on T cell memory.

Mice rendered B cell deficient by targeted disruption of the immunoglobulin mu chain gene (IgM-/- mice) were used to analyze the role of antibodies and B cells in viral infections; homozygous IgM-/- mice were bred in a way to avoid transmission of maternal antibodies. After infection with vesicular stomatitis virus (VSV), IgM-/- mice developed paralytic disease and subsequently died, whereas C57BL/6 control mice or IgM-/- mice passively protected with VSV-neutralizing antibodies survived. Furthermore, IgM-/- mice showed increased natural killer (NK) activity upon exposure to either lymphocytic choriomeningitis virus (LCMV) or to poly(I).poly(C), while NK activity in untreated IgM-/- mice was within normal ranges. Cytotoxic T cell responses were comparable in IgM-/- and control mice infected either with VSV or with vaccinia virus or with low doses of LCMV (10(2) infectious focus-forming units [ifu]). After intracerebral infection with LCMV-Armstrong, CD8+ T cell-mediated lethal lymphocytic choriomeningitis developed independently of the presence of B cells and antibodies. After infection with high doses (2 x 10(6) - 5 x 10(6) ifu) of LCMV-WE or LCMV-Docile, IgM-/- mice exhibited a reduced capacity to control these primary infections and had elevated virus titers for prolonged times (> 60 days). Nevertheless, the cytotoxic T cell response against LCMV in the early phase of infection was comparable in IgM-/- and control mice, but disappeared in those IgM-/- mice which had a persistent viral infection. Cytotoxic T cell memory was apparently unimpaired in low-dose-primed IgM-/- mice, which were able to control the primary virus infection; both IgM-/- and control mice cleared a high intravenous dose of virus within 2 days after challenge infection. This indicates that an efficient T cell memory against LCMV was established in the absence of B cells.

Animals↗
PubMed1996

The human HCLS1 gene maps to chromosome 3q13 by fluorescence in situ hybridization.

The human HS1 gene (HCLS1, hematopoietic cell-specific Lyn substrate 1) expressed in human hematopoietic cells encodes a major substrate of protein-tyrosine kinase, p75HS1. This intracellular protein is involved in the signal transduction pathways that initiate at the antigen receptors of both B and T lymphocytes. Fluorescence in situ hybridization using a 2.0-kb cDNA and an 8.0-kb genomic DNA clone of HCLS1 as probes revealed that the gene maps to 3q13.

Adaptor Proteins, Signal Transducing↗
PubMed1996

[Function of HS1 protein in B-cell antigen-receptor signaling and induction of apoptosis].

Cross-linking of antigen receptor complex on the surface of B cells induces activation of the associated protein-tyrosine kinases (PTKs) which, in turn, phosphorylate and activate a variety of intracellular proteins, some of those are known to transmit the signal to further downstream. In some circumstances, such signals eventually result in apoptosis, rather than proliferation, of the cells. The programmed B-cell death is thought to be crucial in developmental selection of functional cells, self-tolerance, regulation of immune response, and so on. Molecular mechanisms of the intracellular signaling pathways leading to the apoptosis are still obscure. HS1, a hematopoietic-lineage specific protein, is a major substrate of the antigen-receptor associated PTKs. The biochemical and predicted structural features suggest HS1 actively involves in the signal transduction pathway from the antigen receptors and may directly regulate a gene transcription. In this review article, discussed are the roles of non-receptor type tyrosine kinases and HS1 in the pathway leading to apoptosis of B cells, recently evidenced by cell- and mouse-genetics.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Antigen-receptor induced clonal expansion and deletion of lymphocytes are impaired in mice lacking HS1 protein, a substrate of the antigen-receptor-coupled tyrosine kinases.

HS1, an intracellular protein expressed specifically in hematopoietic cells, is rapidly tyrosine phosphorylated after cross-linking of antigen receptors on B and T lymphocytes, implicating involvement of this molecule in the signal transduction pathways from the antigen receptors as a substrate of membrane-associated tyrosine kinase(s). The development of lymphoid cells in HS1-deficient mice, generated through gene targeting, appeared normal. However, antibody production to T-independent antigen and proliferative responses of splenic B and T cells after cross-linking of the antigen receptors were impaired in these mutant mice. Furthermore, B cells in the peritoneal cavity of the mutant mice were resistant to multivalent cross-linking of the antigen receptor, which causes apoptosis of such cells in normal mice. Crossing the HS1-deficient mice with the mice harboring transgenes encoding alpha and beta chains of T-cell antigen receptor against a male H-Y antigen resulted in a progeny that demonstrated a significantly impaired ability of thymic negative selection. These results indicate that HS1 is a novel molecule involved in the antigen-receptor-derived signaling pathways and plays important roles not only in clonal expansion, but also in clonal deletion of B and T cells.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Restoration of surface IgM-mediated apoptosis in an anti-IgM-resistant variant of WEHI-231 lymphoma cells by HS1, a protein-tyrosine kinase substrate.

The HS1 protein is one of the major substrates of non-receptor-type protein-tyrosine kinases and is phosphorylated immediately after crosslinking of the surface IgM on B cells. The mouse B-lymphoma cell line WEHI-231 is known to undergo apoptosis upon crosslinking of surface IgM by anti-IgM antibodies. Variants of WEHI-231 that were resistant to anti-IgM-induced apoptosis expressed dramatically reduced levels of HS1 protein. Expression of the human HS1 protein from an expression vector introduced into one of the variant cell lines restored the sensitivity of the cells to apoptosis induced by surface IgM crosslinking. These results suggest that HS1 protein plays a crucial role in the B-cell antigen receptor-mediated signal transduction pathway that leads to apoptosis.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Molecular cloning and characterization of mouse HS1.

Here we report the cloning of a cDNA and a genomic DNA encoding the mouse homolog of human HS1, a hematopoietic cell-specific protein-substrate of non-receptor type protein-tyrosine kinase(s). Sequence analysis of the mouse HS1 cDNA revealed that it is highly homologous to human HS1 (total percent match = 84%) especially in the amino-terminal half, which contains unique repeating motifs, and in the carboxyl-terminal Src-homology 3 domain. As is the human counterpart, the mouse HS1 gene is expressed exclusively in hematopoietic cells. Genomic fragments covering most of the HS1 gene were isolated and used to map this gene to mouse chromosome 16.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Impaired proliferation of peripheral B cells and indication of autoimmune disease in lyn-deficient mice.

The Src family protein-tyrosine kinase Lyn associates physically with the BCR and has been suggested to play an important role in BCR-mediated signaling. Studies with lyn-/- mice showed that the number of B cells decreased by half in their peripheral tissues. In addition, these B cells do not respond normally to a number of stimuli, including BCR cross-linking and CD40 ligand. Induction of tyrosine phosphorylation on a variety of cellular proteins, such as Vav, Cbl, and HS1, upon BCR cross-linking was also abolished in these B cells. Despite the impaired BCR-mediated signaling, concentrations of IgM and IgA in sera were remarkably elevated, and production of autoantibodies was detected in lyn-/- mice. Histological study showed splenomegaly and enlargement of lymph nodes that became evident with age in the mutant mice. The spleen contained significant number of plasma cells as well as unusual lymphoblast-like cells carrying Mac1 antigen and cytoplasmic IgM. These cells spontaneously secreted a large amount of IgM in vitro. Finally, significant number of lyn-/- mice show glomerulonephritis, an indication of autoimmune disease. From these data, we conclude that Lyn plays a role in signal transduction for not only clonal expansion and terminal differentiation of peripheral B cells but also elimination of autoreactive B cells.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Phosphorylation of HS1, GAP-associated p190 and a novel GAP-associated p60 protein by cross-linking of Fc gamma RIIIA.

Human Fc gamma receptor IIIA (hFc gamma RIIIA) cDNA was introduced into mouse macrophage/monocyte cell line P388D1, and several stable cell clones expressing hFc gamma RIIIA were isolated. This facilitated the study of the biological function of Fc gamma RIIIA in monocytes/macrophages. The cloned cells showed the high phagocytic activity mediated by hFc gamma-RIIIA, while the original P388D1 cells did not. In order to examine the phosphorylation of proteins involved in hFc gamma RIIIA signal transduction, these receptors were stimulated by cross-linking. The cross-linking of hFc gamma RIIIA induced a rapid increase in tyrosine phosphorylation of several proteins, including PLC-gamma 1, Syk, HS1, and p21rasGAP-associated p190 and p60 proteins. Immunoblotting with a polyclonal antibody specific for the GAP-associated p62 protein, which was originally found in fibroblasts and is homologous with an RNA-binding protein, revealed that the p60 phosphorylated after cross-linking of hFc gamma RIIIA seemed to represent a novel GAP-associated protein unrelated to the known GAP-associated p62 protein, which was also present in the P388D1 cells.

Adaptor Proteins, Signal Transducing↗
PubMed1994

IL-5 receptor-mediated tyrosine phosphorylation of SH2/SH3-containing proteins and activation of Bruton's tyrosine and Janus 2 kinases.

Interleukin 5 (IL-5) induces proliferation and differentiation of B cells and eosinophils by interacting with its receptor (IL-5R) which consists of two distinct polypeptide chains, alpha and beta (beta c). Although both IL-5R alpha and beta c lack a kinase catalytic domain, IL-5 is capable of inducing tyrosine phosphorylation of cellular proteins. We investigated the role of IL-5R alpha in tyrosine phosphorylation of molecules involved in IL-5 signal transduction, using an IL-5-dependent early B cell line, Y16 and transfectants expressing intact or mutant IL-5R alpha together with intact beta c. The results revealed that the transfectants expressing truncated IL-5R alpha, which entirely lacks a cytoplasmic domain, together with beta c, showed neither protein-tyrosine phosphorylation nor proliferation in response to IL-5. This confirms that IL-5R alpha plays a critical role in protein-tyrosine phosphorylation which triggers cell growth. IL-5 stimulation results in rapid tyrosine phosphorylation of beta c and proteins containing Src homology 2 (SH2) and/or SH3 domains such as phosphatidyl-inositol-3 kinase, Shc, Vav, and HS1, suggesting their involvement in IL-5-mediated signal transduction. IL-5 stimulation significantly enhanced activities of Janus 2 and B cell-specific Bruton's tyrosine kinases (JAK2 and Btk) and increased the tyrosine phosphorylation of JAK2 kinase. These results and recent data on signaling of growth factors taken together, multiple biochemical pathways driven by tyrosine kinases such as JAK2 and Btk are involved in IL-5 signal transduction.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1994

B cells are essential for murine mammary tumor virus transmission, but not for presentation of endogenous superantigens.

Murine mammary tumor viruses (MMTVs) are retroviruses that encode superantigens capable of stimulating T cells via superantigen-reactive T cell receptor V beta chains. MMTVs are transmitted to the suckling offspring through milk. Here we show that B cell-deficient mice foster nursed by virus-secreting mice do not transfer infectious MMTVs to their offspring. No MMTV proviruses could be detected in the spleen and mammary tissue of these mice, and no deletion of MMTV superantigen-reactive T cells occurred. By contrast, T cell deletion and positive selection due to endogenous MMTV superantigens occurred in B cell-deficient mice. We conclude that B cells are essential for the completion of the viral life cycle in vivo, but that endogenous MMTV superantigens can be presented by cell types other than B cells.

Animals↗
PubMed1994

Antibodies generated from human immunoglobulin miniloci in transgenic mice.

One approach to the production of human monoclonal antibodies focusses on the creation of transgenic mice bearing human immunoglobulin gene miniloci. Whilst such loci undergo lymphoid-specific gene rearrangement, only a small proportion of mouse B cells express the human immunoglobulin chains; the miniloci thus contribute poorly to serum immunoglobulin. Attributing this poor performance to competition between the transgenic and endogenous immunoglobulin loci, we crossed mice bearing a human immunoglobulin heavy-chain (HulgH) minilocus with animals that had been rendered B cell-deficient by disruption of their endogenous heavy-chain locus. The results were dramatic: the human minilocus rescued B cell differentiation such that effectively all B cells now expressed human mu chains. The concentration of antibody in the mouse serum recognised by anti-human mu increased to a concentration about one sixth that in human serum. The HulgH antibodies are heterogenous with diversity being generated by both combinatorial and junctional processes. Following antigen challenge, specific antibody is elicited but at low titre.

Amino Acid Sequence↗
PubMed1994

Signaling properties of anti-immunoglobulin--resistant variants of WEHI-231 B lymphoma cells.

Stimulation of the B cell antigen receptor (BCR) of the murine immature WEHI-231 B lymphoma with anti-immunoglobulin antibodies leads to irreversible growth arrest and apoptosis. As in normal B cells, membrane immunoglobulin (mIg) ligation in WEHI-231 cells triggers a series of signaling cascades from the BCR to intracellular compartments. In order to address the role of early signals in mediating the growth arrest of WEHI-231 cells, we have generated two variants resistant to the anti-Ig-mediated inhibitory effect. Some of the properties of these variants have been recently described in terms of bcl-2 and c-myc gene regulation. We report here that these variants can be further distinguished from the wild type on the basis of significant alterations in the early biochemical events which follow mIg ligation. Both Ca2+ signals and patterns of protein tyrosine phosphorylation were affected in these variants, suggesting that alterations in the early signal transduction machinery may have profound effects on the fate of B cells. In addition, we found that expression of the p75HS1 substrate of p53/56lyn was strikingly reduced in both variants as compared to the wild type. These findings support the view that p75HS1 may play a critical role in BCR-dependent signaling cascades.

Animals↗
PubMed1993

Identification of HS1 protein as a major substrate of protein-tyrosine kinase(s) upon B-cell antigen receptor-mediated signaling.

Crosslinking of membrane-bound immunoglobulins, which are B-cell antigen receptors, causes proliferation and differentiation of B cells or inhibition of their growth. The receptor-mediated signaling involves tyrosine phosphorylation of cellular proteins and rapid activation of Src-like kinases. The amino acid sequences of five proteolytic peptides of p75, a major substrate of protein-tyrosine(s) in the signaling, showed that p75 is the human HS1 gene product. The HS1 gene is expressed specifically in hematopoietic cells and encodes p75HS1, which carries both helix-turn-helix and Src homology 3 motifs. p75HS1 showed rapid tyrosine phosphorylation and association with a Src-like kinase, Lyn, after crosslinking of membrane-bound IgM. Thus, p75HS1 may be an important substrate of Lyn and possibly other protein-tyrosine kinases upon B-cell antigen receptor-mediated signaling.

Adaptor Proteins, Signal Transducing↗