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T Kishimoto

Publications and source records attributed to T Kishimoto.

At least 325 records · Page 18Linked to original sources
PubMed1997

Structure and function of a new STAT-induced STAT inhibitor.

The signalling pathway that comprises JAK kinases and STAT proteins (for signal transducer and activator of transcription) is important for relaying signals from various cytokines outside the cell to the inside. The feedback mechanism responsible for switching off the cytokine signal has not been elucidated. We now report the cloning and characterization of an inhibitor of STAT activation which we name SSI-1 (for STAT-induced STAT inhibitor-1). We found that SSI-1 messenger RNA was induced by the cytokines interleukins 4 and 6 (IL-4, IL-6), leukaemia-inhibitory factor (LIF), and granulocyte colony-stimulating factor (G-CSF). Stimulation by IL-6 or LIF of murine myeloid leukaemia cells (M1 cells) induced SSI-1 mRNA expression which was blocked by transfection of a dominant-negative mutant of Stat3, indicating that the SSI-1 gene is a target of Stat3. Forced overexpression of SSI-1 complementary DNA interfered with IL-6- and LIF-mediated apoptosis and macrophage differentiation of M1 cells, as well as IL-6 induced tyrosine-phosphorylation of a receptor glycoprotein component, gp130, and of Stat3. When SSI-1 is overexpressed in COS7 cells, it can associate with the kinases Jak2 and Tyk2. These findings indicate that SSI-1 is responsible for negative-feedback regulation of the JAK-STAT pathway induced by cytokine stimulation.

Amino Acid Sequence↗
PubMed1997

Signals through gp130 upregulate bcl-x gene expression via STAT1-binding cis-element in cardiac myocytes.

We described recently the activation of the Janus kinasesignal transducer and activator of transcription (JakSTAT) and mitogen-activated protein (MAP) kinase pathways by leukemia inhibitory factor (LIF) through gp130, a signal transducer of IL-6-related cytokines, that transduces hypertrophic signals in cardiac myocytes. In addition, stimulation of gp130 by IL-6-related cytokines is known to exert a cytoprotective effect. In the present study, we investigated the possibility that activation of gp130 initiates activation of the cytoprotective genes in cardiac myocytes. Incubation of cardiac myocytes with LIF induced the expression of bcl-x, and the isoform that was induced by LIF was identified as bcl-xL. Induction of bcl-xL protein was also identified by Western blotting. Antisense oligonucleotide against bcl-x mRNA inhibited protective effect of LIF accompanied with the reduction in bclxL protein. We constructed bcl-x promoter-luciferase reporter gene plasmids (-639/+10- or -161/+10-luciferase), and transfected them to cardiac myocytes. LIF stimulation increased the luciferase activity of -639/+10-luciferase plasmids. Although -161/+10-luciferase plasmids presented comparable responsiveness to LIF, the basal transcription level was impaired. The LIF-responsive cis-element was localized to a DNA fragment (positions -161 to +10) that contains an interferon-gamma activation site (GAS) motif (GGA) at position -41 of the bcl-x gene promoter. This motif bound to STAT1, not to STAT3, and site-directed mutagenesis revealed that this motif was essential for LIF-responsive promoter activity. These data suggest that LIF induces bcl-x mRNA via STAT1 binding cis-element in cardiac myocytes, presenting cytoprotective effect.

Animals↗
PubMed1997

Interleukin 6 and AIDS-associated Kaposi's sarcoma: a nested case control study within the Multicenter AIDS Cohort Study.

Since the beginning of the AIDS epidemic, there has been considerable research on the etiology of Kaposi's sarcoma (KS) among HIV-infected individuals. A number of studies have confirmed that HIV or HIV-encoded products can interact with human cells to induce the production of cytokines, including interleukin 6 (IL-6). In vitro observations have indicated that AIDS-KS cells can produce significant levels of IL-6 and also respond to this cytokine. Preliminary data suggested that IL-6 may be elevated among HIV-infected individuals that subsequently develop AIDS-KS. The objective of this study was to determine if elevated levels of IL-6 are associated with an increased incidence of AIDS-KS compared to other AIDS-defining illnesses such as opportunistic infections (OIs). Serum IL-6 levels were determined by ELISA in frozen sera collected from participants in the Multicenter AIDS Cohort Study (MACS) at 6 months prior to AIDS diagnosis, in 73 cases (AIDS-KS), and 152 controls (OI). Elevated IL-6 levels were more prevalent among men with AIDS-OI than those with AIDS-KS: crude odds ratio (OR), 0.4 (95% CI, 0.2-0.9). Models of multivariate logistic regression were used to study potential confounders. Sexual behavior variables did not seem to confound the association between IL-6 and AIDS-KS. The higher prevalence of IL-6 among controls could be explained by the association of higher levels of IL-6 with lower levels of CD4 T cell number. IL-6 may be a marker of severe immune dysfunction among HIV-infected individuals.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Molecular cloning of a rat 49-kDa TBP-interacting protein (TIP49) that is highly homologous to the bacterial RuvB.

TBP as a central component in transcriptional regulation can form complexes with various regulatory factors. Using histidine-tagged TBP for affinity-purification of TBP-bound proteins, we isolated a 49-kD protein termed TBP-interacting protein 49 (TIP49) from rat liver nuclear extracts. We cloned the entire cDNA of TIP49 encoding a novel polypeptide of 456 amino acids, and thereafter established an FM3A cell line that constitutively expressed an epitope-tagged TBP. Immunoprecipitation analysis of the cell extracts indicated that TIP49 and TBP were present in an identical complex. Interestingly, the amino acid sequence of TIP49 exhibited high similarity to those sequences of the RuvB bacterial recombination factors which direct branch migration of the Holliday junction and contain the Walker A and B motifs responsible for ATP binding and ATP hydrolysis. These findings suggest that TIP49 is a putative ATP-dependent DNA helicase.

ATPases Associated with Diverse Cellular Activitie↗
PubMed1997

Enhancement of gp130-mediated tyrosine phosphorylation of STAT3 and its DNA-binding activity in dexamethasone-treated AIDS-associated Kaposi's sarcoma cells: selective synergy between dexamethasone and gp130-related growth factors in Kaposi's sarcoma cell proliferation.

The soluble IL-6R (slL-6R alpha)/IL-6 complex and oncostatin M (OM), which exert biologic activities through the signal-transducing protein gp130, are potent growth factors for AIDS-associated Kaposi's sarcoma (KS) cells. Clinical observations indicate that glucocorticoid therapy is a possible risk factor in KS; however, little is known of specific interactions in KS cells between glucocorticoid and gp130-related growth factors. We obtained evidence that dexamethasone (Dex), in a synergistic manner, enhances gp130-mediated growth of KS cells. Anti-gp130 Abs or the glucocorticoid antagonist RU-486 abolished this synergistic effect. In addition, Dex had additive but not synergistic effects on stimulation of KS cell growth with IL-1beta or TNF-alpha, the signals of which are not mediated through gp130. Immunoblot analysis revealed sIL-6R alpha/IL-6- or OM-induced tyrosine phosphorylation of a similar set of proteins in KS cells, and which was augmented significantly in Dex-treated KS cells. Stimulation of KS cells with sIL-6R alpha/IL-6 or OM induced rapid tyrosine phosphorylation of the transcription factor STAT3, and Dex significantly enhanced the accumulation of tyrosine-phosphorylated STAT3. Electrophoretic mobility shift assays showed sIL-6R alpha/IL-6- or OM-induced DNA-binding activity of STAT3 in KS cells, and Dex further increased this activity. Thus, Dex appears to participate in the gp130-STAT3 signaling and transcriptional events by enhancing STAT3 activation, thereby leading to selective synergistic stimulation of KS cell growth with Dex and the gp130-related growth factors.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Targeted disruption of Cbfa1 results in a complete lack of bone formation owing to maturational arrest of osteoblasts.

A transcription factor, Cbfa1, which belongs to the runt-domain gene family, is expressed restrictively in fetal development. To elucidate the function of Cbfa1, we generated mice with a mutated Cbfa1 locus. Mice with a homozygous mutation in Cbfa1 died just after birth without breathing. Examination of their skeletal systems showed a complete lack of ossification. Although immature osteoblasts, which expressed alkaline phophatase weakly but not Osteopontin and Osteocalcin, and a few immature osteoclasts appeared at the perichondrial region, neither vascular nor mesenchymal cell invasion was observed in the cartilage. Therefore, our data suggest that both intramembranous and endochondral ossification were completely blocked, owing to the maturational arrest of osteoblasts in the mutant mice, and demonstrate that Cbfa1 plays an essential role in osteogenesis.

Animals↗
PubMed1997

CXCR4/fusin is not a species-specific barrier in murine cells for HIV-1 entry.

Since some murine cells expressing human CD4 fail to internalize HIV-1, another block was thought to be located at the level of viral entry in addition to CD4. Recently, CXCR4 was shown to function as a coreceptor for T cell line-tropic HIV-1 entry. Here we demonstrated that cells expressing murine CXCR4 and human CD4 fused with cells expressing the env proteins derived from T cell line-tropic HIV-1 and were infected with T cell line-tropic HIV-1 strains. In contrast, the same cells were not infected with chimeric clones constructed by substitution of monocyte- or macrophage-tropic strain-derived env region or V3 region into T cell line-tropic HIV-1, indicating V3 loop of envelope protein is required for murine CXCR4mediated HIV-1 entry. We conclude that murine CXCR4 is not a species specific barrier to the entry of T cell line-tropic HIV-1.

3T3 Cells↗
PubMed1997

Targeted disruption of the mouse Stat3 gene leads to early embryonic lethality.

Signal transducer and activator of transcription (STAT) proteins have been shown to mediate biological actions in response to cytokines. Stat3, a member of the STAT family, is activated by a variety of cytokines, including the interleukin 6 family of cytokines, leptin, granulocyte colony-stimulating factor, and epidermal growth factor. To address the biological function of Stat3, we generated mice deficient in Stat3 by gene targeting. No viable Stat3-deficient mice could be obtained from heterozygote intercross. Analysis of embryos at several gestation times revealed that Stat3-deficient embryos showed a rapid degeneration between embryonic days 6.5 and 7.5, although they developed into the egg cylinder stage until embryonic day 6.0. These results demonstrate that Stat3 is essential for the early development of mouse embryos.

Animals↗
PubMed1997

The amino acid residues immediately carboxyl-terminal to the tyrosine phosphorylation site contribute to interleukin 6-specific activation of signal transducer and activator of transcription 3.

Signal transducers and activators of transcription (Stat) proteins play an important role in signaling through a variety of cytokine and growth factor receptors. Each of the Stat proteins is activated in a ligand-specific manner. Only the Src homology 2 (SH2) domains of Stat1 and Stat2 are critical for the ligand-specific activation of interferon signaling. In this study we determined the domains in Stat3 protein that contribute to interleukin 6 (IL-6)-specific phosphorylation. Based on evidence that Stat3, but not Stat1, is activated in the presence of low levels of IL-6 and soluble IL-6 receptor, we constructed various swap mutants between Stat3 and Stat1 and examined their response to IL-6 after their transient expression into COS7 cells. The region upstream of the SH2 domain was exchangeable between Stat1 and Stat3, whereas the region carboxyl-terminal to the SH2 domain of Stat3 was critical to phosphorylation by IL-6. However, unlike Stat1 and Stat2 in interferon signaling, the swap mutant in which 5 amino acid residues just carboxyl-terminal to the tyrosine phosphorylation site (Tyr705) in Stat3 was replaced by the corresponding region derived from Stat1 was not phosphorylated in response to IL-6. Substituting 1 amino acid (Lys709) at position +4 relative to Tyr705 abolished the tyrosine phosporylation of Stat3 in response to IL-6. Co-immunoprecipitation experiments demonstrated that these mutants were associated with gp130 at an extent similar to wild-type Stat3. Taken together, these results show that the amino acid residues immediately carboxyl-terminal to the tyrosine phosphorylation site are involved in IL-6-specific activation of Stat3.

Acute-Phase Proteins↗
PubMed1997

The anti-human tumor effect and generation of human cytotoxic T cells in SCID mice given human peripheral blood lymphocytes by the in vivo transfer of the Interleukin-6 gene using adenovirus vector.

Interleukin-6 (IL-6) was found to function as a late-acting killer helper factor in the differentiation of CTLs. In the model of tumor-bearing mice, the systemic administration of recombinant IL-6 was found to mediate the antitumor effect on the immunogenic murine tumors via the in vivo induction of murine CTLs but not on the poorly immunogenic murine tumors in our previous study. However, an in vivo experimental model capable of analyzing the anti-human tumor effect via the in vivo induction of human CTLs has not yet been established. Therefore, in the present study, severe combined immunodeficient mice were given human peripheral blood lymphocytes (SCID-PBL/hu), and thereafter human tumor cells were administered i.p. into these SCID-PBL/hu mice as a model of human patients with cancer. When these SCID-PBL/hu mice bearing allogeneic human CESS B blastoid tumor cells were treated in vivo with recombinant adenovirus vector expressing IL-6 cDNA, both the induction of CD8+ human CTLs against CESS cells in the spleen cells and peritoneal exudate cells and a prolongation in the survival of these mice were observed. Furthermore, SCID-PBL/hu mice were given peripheral blood lymphocytes from patients with cancer (gastric or rectal cancers) and autologous human tumor cells. The in vivo administration of recombinant adenovirus vector expressing IL-6 cDNA induced CD8+ human CTLs specific for autologous human tumor cells from human precursor T cells. The in vivo injection of the IL-6 gene also inhibited growth and metastasis in autologous human cancers. Based on the above findings, the experimental model using SCID-PBL/hu mice and the IL-6 gene delivered in vivo by an adenovirus vector might therefore provide a new strategy capable of analyzing an anti-human tumor effect and the in vivo induction of human CTLs by cytokine gene therapy without using the human body.

Adenoviridae↗
PubMed1997

Impairment of antigen-specific antibody production in transgenic mice expressing a dominant-negative form of gp130.

gp130 is a common signal-transducing receptor component for the interleukin 6 family of cytokines functioning in, for example, immune, hematopoietic, and nervous systems. In this study, to investigate the physiological functions of gp130 and to determine the pathological consequences of impaired gp130 signals, we have generated transgenic mice expressing a cytoplasmically truncated form of mouse gp130. Expression of this form of gp130 in lymphocytes significantly suppressed interleukin 6-induced tyrosine phosphorylation of endogenous gp130 and a downstream signaling molecule, signal transducer and activator of transcription 3, indicating that this form has a dominant negative function. In spite of the impaired gp130 signals, the development of lymphocytes in the transgenic mice appeared normal in terms of surface marker phenotypes. These mice, however, exhibited severe defects in antigen-specific antibody production of most immunoglobulin isotypes other than IgM after immunization with 2,4-dinitrophenol-conjugated ovalbumin. These results demonstrate in vivo that gp130 is essential for antigen-specific antibody production.

Actins↗
PubMed1997

Kinetic diversity in the fusion of exocytotic vesicles.

The speed at which secretory vesicles fuse with the plasma membrane is a key parameter for neuronal and endocrine functions. We determined the precise time courses for fusion of small clear and large dense-core vesicles in PC12 and chromaffin cells by simultaneously measuring both plasma membrane areas and release of vesicular contents. We found that instantaneous increases in cytosolic Ca2+ concentration evoked vesicle fusion, but with time constants that varied over four orders of magnitude among different types of vesicles and cells. This indicates that the molecular machinery for the final Ca2+-dependent fusion steps of exocytosis is highly variable and is as critical as Ca2+ signalling processes in determining the speed and amount of secretion of neurotransmitters and hormones. Our results suggest a new possibility that the molecules responsible for the final fusion reaction that leads to vesicle fusion are key determinants for neuronal plasticity and hormonal disorders.

Acetylcholine↗
PubMed1997

Significance of cyclin D1 overexpression in transitional cell carcinomas of the urinary bladder and its correlation with histopathologic features.

BACKGROUND: Genetic alterations leading to neoplastic transformation of the urothelium are likely to involve the activation of oncogenes and loss of functional tumor suppressor genes. Cyclin D1 has been implicated as a putative protooncogene whereas mutations of the p53 gene occur frequently in invasive transitional cell carcinomas (TCCs) of the urinary bladder. In this study, cyclin D1 overexpression and nuclear accumulation of p53 were evaluated and the results correlated with histopathologic features. METHODS: TCCs of the urinary bladder from 161 surgical procedures were evaluated for cyclin D1 overexpression and nuclear accumulation of p53. Results were correlated with tumor grade, T classification, and papillary status. Topologic distributions of cyclin D1, p53, and proliferating cellular nuclear antigen (PCNA) were evaluated. Northern blot analysis was performed on selected specimens. RESULTS: Overexpression of cyclin D1 was observed in 47% (24 of 51) of Grade 1 TCCs and 20% (13 of 65) of Grade 2 TCCs but in no Grade 3 TCCs. Approximately 34% (14 of 41) of Ta classified TCCs and 21% (13 of 63) of T1 classified TCCs were immunoreactive for cyclin D1 whereas none of the TCCs beyond T1 was immunoreactive. Overexpression of cyclin D1 was observed only in papillary type TCCs. Results of Northern blot analysis for cyclin D1 were comparable to those of immunohistochemistry. CONCLUSIONS: The observed significant relation between cyclin D1 overexpression and tumor grade/T classification suggests that cyclin D1 may be a useful biologic marker for biopsied materials or urine cytology specimens. The prognostic significance of cyclin D1 overexpression in TCCs remains to be determined.

Adult↗
PubMed1997

Aberrant overexpression of the Wilms tumor gene (WT1) in human leukemia.

To clarify whether the expression of the WT1 gene in leukemic cells is aberrant or merely reflects that in normal counterparts, the expression levels of the WT1 gene were quantitated for normal hematopoietic progenitor cells. Bone marrow (BM) and umbilical cord blood (CB) cells were fluorescence-activated cell sorting (FACS)-sorted into CD34+ and CD34- cell populations, and the CD34+ cells into nine subsets (CD34+ CD33-, CD34+ CD33+, CD34+ CD38-, CD34+ CD38+, CD34+ HLA-DR-, CD34+ HLA-DR+, CD34+ c-kit(high), CD34+ c-kit(low), and CD34+ c-kit-) according to the expression levels of CD34, CD33, CD38, HLA-DR, and c-kit. Moreover, acute myeloid leukemic cells were also FACS-sorted into four populations (CD34+ CD33-, CD34+ CD33+, CD34- CD33+, and CD34- CD33-). FACS-sorted normal hematopoietic progenitor and leukemic cells and FACS-unsorted leukemic cells were examined for the WT1 expression by quantitative reverse transcriptase-polymerase chain reaction. The WT1 expression in the CD34+ and CD34- cell populations and in the nine CD34+ subsets of BM and CB was at either very low (1.0 to 2.4 x 10(-2)) or undetectable (< 10(-2)) levels (the WT1 expression level of K562 cells was defined as 1.0), whereas the average levels of WT1 expression in FACS-sorted and -unsorted leukemic cells were 2.4 to 9.3 x 10(-1). Thus, the WT1 expression levels in normal hematopoietic progenitor cells were at least 10 times less than those in leukemic cells. Therefore, we could not find any normal counterparts of BM or CB that expressed the WT1 at levels comparable with those in leukemic cells. These results indicate an aberrant overexpression of the WT1 gene in leukemic cells and imply the involvement of this gene in human leukemogenesis.

Acute Disease↗
PubMed1997

Vav is associated with signal transducing molecules gp130, Grb2 and Erk2, and is tyrosine phosphorylated in response to interleukin-6.

Vav is a hematopoietic cell-specific proto-oncogene. We show that interleukin-6 (IL-6) induces transient tyrosine phosphorylation of Vav in a human myeloma cell line, U266. A membrane-distal part of the cytoplasmic region of gp130 is critical for association between Vav and gp130, and the IL-6-induced tyrosine phosphorylation of Vav. Mitogen-activated protein kinase (MAPK) (p42MAPK or extracellular signal-regulated kinase 2 (Erk2)) is coprecipitated with Vav. MAPK activity in the anti-Vav immunoprecipitates is upregulated by IL-6 stimulation. Furthermore Vav is associated with Grb2 which is known as an adapter protein leading to Ras activation. The results imply that Vav may link gp130 activation to downstream MAPK activation in hematopoietic cells.

Adaptor Proteins, Signal Transducing↗
PubMed1997

Interleukin 6 activates heat-shock protein 90 beta gene expression.

The levels of the cytokine interleukin-6 (IL-6) and the heat-shock protein hsp90 have both been reported to be elevated in patients with active systemic lupus erythematosus (SLE). We show that hsp90 protein accumulates to increased levels in both HuH7 hepatoma cells and peripheral blood mononuclear cells (PBMCs) treated with IL-6. In PBMCs this effect occurs without induction of the other hsps, paralleling the specific elevation of hsp90 in SLE. IL-6 is able to activate the hsp90 gene promoter directly; this activation can also be achieved by overexpressing either of the transcription factors NF-IL-6 or NF-IL-6 beta whose synthesis is induced by IL-6 treatment. Hence the induction of hsp90 protein accumulation by IL-6 is likely to be dependent on the enhanced activity of the hsp90 beta gene promoter produced by increased levels of NF-IL-6 and/or NF-IL-6 beta. These effects are discussed in terms of the role of hsp90 in the normal immune system and the mechanism of its activation in patients with SLE.

Blotting, Western↗