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Biomedical subjects

A Miyajima

Publications and source records attributed to A Miyajima.

At least 145 records · Page 8Linked to original sources
PubMed1995

A human GM-CSF receptor expressed in transgenic mice stimulates proliferation and differentiation of hemopoietic progenitors to all lineages in response to human GM-CSF.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) mainly stimulates proliferation and maturation of myeloid progenitor cells. Although the signal transduction pathways triggered by GM-CSF receptor (GMR) have been extensively characterized, the roles of GMR signals in differentiation have remained to be elucidated. To examine the relationship between receptor expression and differentiation of hemopoietic cells, we used transgenic mice (Tg-mice) that constitutively express human (h) GMR at almost all stages of hemopoietic cell development. Proliferation and differentiation of hemopoietic progenitors in bone marrow cells from these Tg-mice were analyzed by methylcellulose colony formation assay. High affinity GMR interacts with GM-CSF in a species-specific manner, therefore one can analyze the effects of hGMR signals on differentiation of mouse hemopoietic progenitors using hGM-CSF. Although mouse (m) GM-CSF yielded only GM colonies, hGM-CSF supported various types of colonies including GM, eosinophil, mast cell, erythrocyte, megakaryocyte, blast cell, and mixed hemopoietic colonies. Thus, the effects of hGM-CSF on colony formation more closely resembled mIL-3 than those of mGM-CSF. In addition, hGM-CSF generated a much larger number of blast cell colonies and mixed cell colonies than did mIL-3. hGM-CSF also generated erythrocyte colonies in the absence of erythropoietin. Therefore, GM-CSF apparently has the capacity to promote growth of cells of almost all hemopoietic cell lineages, if functional hGMR is present.

Animals↗
PubMed1995

Sequential mutations in the interleukin-3 (IL3)/granulocyte-macrophage colony-stimulating factor/IL5 receptor beta-subunit genes are necessary for the complete conversion to growth autonomy mediated by a truncated beta C subunit.

An amino-terminally truncated beta C receptor (beta C-R) subunit of the interleukin-3 (IL3)/granulocyte-macrophage colony-stimulating factor/IL5 receptor complex mediates factor-independent and tumorigenic growth in two spontaneous mutants of a promyelocytic cell line. The constitutive activation of the JAK2 protein kinase in these mutants confirms that signaling occurs through the truncated receptor protein. Noteworthily, in addition to a 10-kb deletion in the beta C-R subunit gene encoding the truncated receptor, several secondary and independent mutations that result in the deletion or functional inactivation of the allelic beta C-R subunit and the closely related beta IL3-R subunit genes were observed in both mutants, suggesting that such mutations are necessary for the full oncogenic penetrance of the truncated beta C-R subunit. Reversion of these mutations by the expression of the wild-type beta C-R in the two mutants resulted in a fivefold decrease in cloning efficiency of the mutants in the absence of IL3, confirming a functional interaction between the wild-type and truncated proteins. Furthermore, expression of the truncated beta C-R subunit in factor-dependent myeloid cells did not immediately render the cells autonomous but increased the spontaneous frequency to factor-independent growth by 4 orders of magnitude. Implications for both leukemogenic progression and receptor-subunit interaction and signaling are discussed.

Amino Acid Sequence↗
PubMed1995

Functional regions of the mouse interleukin-10 receptor cytoplasmic domain.

The functions of wild-type and mutant mouse interleukin-10 receptors (mIL-10R) expressed in murine Ba/F3 cells were studied. As observed previously, IL-10 stimulates proliferation of IL-10R-expressing Ba/F3 cells. Accumulation of viable cells in the proliferation assay is to a significant extent balanced by concomitant cell death. Moreover, growth in IL-10 also induces a previously unrecognized response, differentiation of the cells, as evidenced both by formation of large clusters of cells in cultures with IL-10 and by induction or enhancement of expression of several cell surface antigens, including CD32/16, CD2, LECAM-1 (v-selectin), and heat-stable antigen. Two distinct functional regions near the C terminus of the mIL-10R cytoplasmic domain which mediate proliferation were identified; one of these regions also mediates the differentiation response. A third region proximal to the transmembrane domain was identified; removal of this region renders the cell 10- to 100-fold more sensitive to IL-10 in the proliferation assay. In cells expressing both wild-type and mutant IL-10R, stimulation with IL-10 leads to tyrosine phosphorylation of the kinases JAK1 and TYK2 but not JAK2 or JAK3 under the conditions tested.

Animals↗
PubMed1995

[Use of semirigid ureteroscopes for treatment of ureteral calculi].

BACKGROUND: The objective of this study is to evaluate the efficacy of ureteroscopic lithotripsy as the treatment of ureteral stones in the recent era by comparing the result using a semirigid ureteroscope with the result using a conventional ureteroscope. METHODS: Between 1991 and 1994, 136 patients with ureteral calculi underwent transurethral ureteroscopic lithotripsy in our hospital. From July 1991 to March 1993, 14F rigid ureteroscope with the rod lens system was used for 82 patients (group 1), whereas from April 1993 to July 1994 either a 9.5F or 7F semirigid fiberoptic ureteroscope was used for 54 patients (group 2). Insertion of ureteroscopes was performed under continuous irrigation of saline without mechanical dilation of the ureteral orifice in both groups. RESULTS: The rates of complete removal of stone at the first trial were 56.1% in group 1 and 72.2% in group 2 with the overall complete removal rate of 62.5%. The complete removal rates of stones in the upper, middle and lower ureters were 18.2%, 54.8% and 72.4% in group 1 and 14.3%, 72.7% and 88.0% in group 2, respectively. The major reasons for unsuccessful treatments was upward migration of stones during the procedure. As intraoperative complications, ureteral disruption occurred in 1 case in group 1, and ureteral perforation in 5 patients in group 1 (6.1%) and 2 in group 2 (3.8%). Acute bacterial infection with prolonged fever was observed in 3 patients in group 1 and in none in group 2. CONCLUSION: From these results, the new semirigid ureteroscope with fiberoptic imaging bundles made the transurethral lithotripsy a safer and more efficient procedure for the treatment of ureteral calculi especially those in the lower ureters.

Adolescent↗
PubMed1995

[Spontaneous rupture of ureter caused by ureteral cancer].

A 63-year-old man was admitted with right flank pain, nausea and chill. CT scan revealed right hydronephrosis and rupture of ureter, but tumor or stone was not detected in the CT scan. However retrogradepylelography revealed right lower ureteral tumor, and this patient was treated by right nephroureterectomy and partial cystectomy. Histopathological examination of ureteral tumor showed transitional cell carcinoma. Spontaneous rupture of ureter due to ureteral cancer is a rare case, which has not been reported in the Japanese literature. Clinical study was performed about cases of spontaneous rupture of ureter which have been previously reported.

Carcinoma, Transitional Cell↗
PubMed1995

[A case of huge prostate cancer].

An 89-year-old man with bilateral leg edema and a huge abdominal mass was admitted for further evaluation. CT scan showed a hugh prostatic mass which occupied the whole pelvis cavity accompanying multiple pelvic bone metastases. Suprapubic needle biopsy revealed that the mass was well differentiated adenocarcinoma of prostate origin. The treatment was initiated by 500 mg per day of estramustine phosphate combined with injectable LH-RH analogue 2 months later. The serum levels of tumor markers were markedly elevated at the first visit; PSA 210ng/ml, PAP 110ng/ml, gamma-Sm 800ng/ml. They became normalized 3 months after the initiation of the treatment, and the mass was reduced to 11.5% of the initial size, which lead to removal of indwelling urethral catheter. The patient and his family, however, refused further treatment and the patient died of disseminated disease 8 months later.

Adenocarcinoma↗
PubMed1994

Characterization of cell phenotype by a novel cDNA library subtraction system: expression of CD8 alpha in a mast cell-derived interleukin-4-dependent cell line.

We have established a unique variant cell line, MC/9.IL-4, which continuously proliferates in the presence of interleukin-4 (IL-4), from a murine interleukin-3 (IL-3)-dependent mast cell line, MC/9 (referred to as MC/9.IL-3). Compared with MC/9.IL-3 cells, MC/9.IL-4 cells are smaller, lack cytoplasmic granules and metachromasia, carry a very small amount of histamine, and express fewer high-affinity IgE receptors (IgERs) and IL-3 receptors. To further characterize MC/9.IL-4, we developed a novel method to enrich cell type-specific cDNAs by cDNA library subtraction and applied it for MC/9.IL-3 versus MC/9.IL-4. Sequence analysis of cDNA clones isolated by this technique showed that MC/9.IL-4 cells specifically express CD8 alpha and expression of mast cell-specific proteases and major histocompatibility complex class II (MHCII) is considerably decreased. It was also noted that responsiveness to the IL-3-agonistic antibody F9 and expression of the transcription factor GATA-2 is diminished in MC/9.IL-4, indicating that MC/9.IL-4 have lost major characteristics of the bone marrow-derived cultured mast cells. Because other T-cell marker antigens, CD8 beta, CD4, Thy-1, were not detected on MC/9.IL-4 cells, MC/9.IL-4 cells may represent an unknown class of hematopoietic cells that express CD8 alpha. This cell line will be useful in studies of IL-4-mediated signal transduction, as well as transcriptional regulation of mast cell characteristic genes. This study also demonstrates the effective use of the cDNA library subtraction strategy to characterize unknown types of hematopoietic cells at the molecular level.

Animals↗
PubMed1994

Regulation of the interleukin-3 (IL-3) receptor by IL-3 in the fetal liver-derived FL5.12 cell line.

To determine the effects of a cytokine on cognate receptor expression in normal and neoplastic cells, the interleukin-3 receptor (IL-3R) complex was examined in the parental IL-3-dependent line FL5.12, which was isolated from fetal liver, and in autocrine- and v-abl-transformed derivative lines. IL-3 decreased the amount of the IL-3R alpha and beta chains detected on the cell surface of the parental IL-3-dependent cells. In contrast, high levels of IL-3R beta were constitutively detected on the autocrine-transformed lines in the absence and presence of exogenous IL-3. Only low levels of IL-3R beta were observed in the two v-abl-transformed derivative cell lines examined, which no longer required IL-3 for growth. The levels of the IL-3R alpha chain detected were similar in these transformed cells and were not regulated by IL-3. These results were substantiated further by RNA analysis, because IL-3 decreased the levels of IL-3R transcripts in the parental factor-dependent FL5.12 line. The pattern of IL-3R gene expression was opposite to that of other receptors or proto-oncogenes, because RNA transcripts for all other genes examined were induced by IL-3. We conclude that IL-3 tightly controls IL-3R expression in the IL-3-dependent FL5.12 cells, whereas steady-state mRNA levels were not altered in the two v-abl-transformed derivative cell lines examined in this study.

Animals↗
PubMed1994

Structure of the gene encoding the alpha subunit of the human granulocyte-macrophage colony stimulating factor receptor. Implications for the evolution of the cytokine receptor superfamily.

The receptor for granulocyte-macrophage colony-stimulating factor (GM-CSF) is composed of at least two subunits, alpha and beta. In addition to the conserved cysteine residues and a "WSxWS" motif, the extracellular segments of both subunits have domains that are structurally related to a fibronectin type III domain. This structure is conserved in all members of the cytokine receptor superfamily. We isolated and characterized genomic DNA clones containing the entire coding sequences of the alpha subunit of the human GM-CSF receptor (hGMR alpha). The gene spans approximately 44 kilobases and has 13 exons. The major transcription initiation site was determined to be 195 base pairs upstream of the translation initiation site. The putative promoter region lacks a typical TATA motif and an Sp1 binding site, but contains a purine-rich stretch about 30 base pairs upstream of the transcription initiation site. This stretch is also found in the human interleukin 2 receptor gamma subunit and granulocyte colony-stimulating factor receptor genes. We compared the exon-intron organization of the hGMR alpha gene with other members of the cytokine receptor superfamily and found the genomic organizations to be remarkably well conserved. On the basis of these observations, we propose a model for evolution of this gene family.

Base Sequence↗
PubMed1994

Activation of early response genes and cell proliferation by human interleukin-3, granulocyte-macrophage colony-stimulating factor, and interleukin-5 receptors: comparison with human interleukin-4 receptor signaling.

Interleukin (IL)-3, granulocyte-macrophage colony-stimulating factor, and IL-5 receptors (IL-3R, GMR, and IL-5R) are composed of the alpha chain specific to each and the common beta chain, and both the alpha and beta subunits are members of the cytokine receptor superfamily. We previously showed that the high-affinity human GMR reconstituted by cotransfecting the alpha and beta chain cDNA clones transduces signals in response to hGM-CSF to activate transcription of c-fos, c-jun, and c-myc proto-oncogenes in mouse proB cell line BA/F3 or in mouse fibroblast NIH3T3 cells. These results indicated that molecules, such as tyrosine kinase, unique to hematopoietic cells are not essential to transduce signals. In this study, the function of the alpha subunit of GMR was compared with those of IL-3R and IL-5R by cotransfecting human cDNAs encoding the alpha subunit of IL-3R or IL-5R and the common beta subunit into BA/F3 or NIH3T3 cells. We found that the reconstituted human IL-3R, in response to hIL-3, transduced signals to activate transcription of c-fos promoter and induced DNA synthesis in both types of cells in a manner similar to hGMR. Likewise, hIL-5 activates c-fos promoter in transfected NIH3T3 cells expressing hIL-5R. These results indicated that the alpha subunits of IL-3R and IL-5R have properties similar to those of the GMR alpha subunit. In contrast, transfected human IL-4 receptor (hIL-4R) cDNA, which weakly activated c-fos promoter and induced DNA synthesis in BA/F3 cells, failed to elicit these activities in NIH3T3 cells in response to hIL-4.(ABSTRACT TRUNCATED AT 250 WORDS)

3T3 Cells↗
PubMed1994

Multimeric cytokine receptors: common versus specific functions.

The class I cytokine receptors consist of multiple subunits without any intrinsic enzymatic activities. Receptors for a subset of cytokines with overlapping biological activities often share a common receptor subunit with a signaling function. Each receptor regulates its specific signaling pathways, as well as common pathways depending on the target cell type.

Animals↗
PubMed1994

Cytokine receptors and signal transduction.

Cytokines are important regulators of hemopoiesis which exert their actions by binding to specific, high affinity, cell surface receptors. In the past several years, molecular cloning of these receptors has revealed a new superfamily referred to as the hemopoietic growth factor receptors. Members of this family are defined by a 200 amino acid conserved domain; however, it has become increasingly apparent that another characteristic of these receptors is the shared usage of a common signalling subunit among subgroups in this family. The shared signalling component explains the functional redundancy of many cytokines; however, the mechanism by which these receptors transduce a signal across the membrane is not yet clear. Studies into cytokine action have shown that many of the events that occur in response to ligand stimulation are similar to those observed for the better characterized intrinsic tyrosine kinase receptors. Thus, although the cytokine receptors do not possess intrinsic tyrosine kinase activity, these observations have led to a model of cytokine signal transduction adapted from the signalling mechanisms described for the tyrosine kinase receptors.

Animals↗
PubMed1994

Regulation of IL-3 receptor expression: evidence for a post-transcriptional mechanism that dominantly suppresses the expression of beta subunits.

The IL-3 receptor (IL-3R) is composed of alpha and beta subunits. Two homologous beta subunits of IL-3R are present in the mouse: AIC2A is the IL-3 specific beta subunit, and AIC2B is the common beta subunit shared by IL-3, IL-5 and granulocyte macrophage colony stimulating (GM-CSF) factor receptors. Both beta subunits form functionally indistinguishable high-affinity IL-3Rs with the same IL-3R specific alpha subunit (IL-3R alpha or SUT-1). Cell surface expression of the alpha and beta subunits of IL-3R was found to be diminished in an IL-3 non-responsive variant (MC/9.IL-4) derived from an IL-3-dependent mast cell line, MC/9. This IL-3R-defective phenotype was dominant based on cell fusion experiments. Moreover, regulatory mechanisms of the alpha and beta subunits are distinct since cell hybrids between MC/9.IL-4 and a CTLL-2 transfectant (CTLL/AS) expressing AIC2A and IL-3R alpha showed a significantly reduced expression of the AIC2A mRNA, while the IL-3R alpha expression was unchanged. Since transcription of both AIC2A and IL-3R alpha cDNAs in the CTLL/AS was driven by an artificial promoter, SR alpha, and nuclear run-off assays showed similar transcriptional rates of the AIC2A gene in both CTLL/AS and the cell hybrids between MC/9.IL-4 and CTLL/AS, the dominant suppression of the beta subunits is post-transcriptional and sequence-specific. A target sequence of the negative regulator must be present within 2756 bases of AIC2A mRNA, which is transcribed from the transfected cDNA in CTLL/AS cells. Similar dominant suppression of the beta subunit expression was also found in a B cell line WEHI231. As the negative regulator suppresses expression of the beta subunits of IL-3, IL-5 and GM-CSF receptors, it has the potential to eliminate all three high-affinity receptors simultaneously.

Animals↗
PubMed1994

JAK2 associates with the beta c chain of the receptor for granulocyte-macrophage colony-stimulating factor, and its activation requires the membrane-proximal region.

The high-affinity receptor for granulocyte-macrophage colony-stimulating factor (GM-CSF) consists of a unique alpha chain and a beta c subunit that is shared with the receptors for interleukin-3 (IL-3) and IL-5. Two regions of the beta c chain have been defined; these include a membrane-proximal region of the cytoplasmic domain that is required for mitogenesis and a membrane-distal region that is required for activation of Ras, Raf-1, mitogen-activated protein kinase, and S6 kinase. Recent studies have implicated the cytoplasmic protein tyrosine kinase JAK2 in signalling through a number of the cytokine receptors, including the IL-3 and erythropoietin receptors. In the studies described here, we demonstrate that GM-CSF stimulation of cells induces the tyrosine phosphorylation of JAK2 and activates its in vitro kinase activity. Mutational analysis of the beta c chain demonstrates that only the membrane-proximal 62 amino acids of the cytosolic domain are required for JAK2 activation. Thus, JAK2 activation is correlated with induction of mitogenesis but does not, alone, activate the Ras pathway. Carboxyl truncations of the alpha chain, which inactivate the receptor for mitogenesis, are unable to mediate GM-CSF-induced JAK2 activation. Using baculovirus-expressed proteins, we further demonstrate that JAK2 physically associates with the beta c chain but not with the alpha chain. Together, the results further support the hypothesis that the JAK family of kinase are critical to coupling cytokine binding to tyrosine phosphorylation and ultimately mitogenesis.

Animals↗
PubMed1994

Interleukin-3 and granulocyte-macrophage colony-stimulating factor receptor signal transduction.

The cytokines, interleukin-3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF), share many similar activities on cells of the hemopoietic system. Cloning of the receptors for IL-3 and GM-CSF revealed that these two cytokines utilize receptors consisting of a ligand-specific alpha unit and a beta subunit which is shared. Neither subunit contains intrinsic tyrosine kinase activity, but deletion analysis of the beta subunit cytoplasmic domain has defined certain regions which are important for signal transduction.

Animals↗
PubMed1993

Interleukin-2 receptor gamma chain: a functional component of the interleukin-4 receptor.

The interleukin-2 (IL-2) receptor gamma chain (IL-2R gamma) is an essential component of high- and intermediate-affinity IL-2 receptors. IL-2R gamma was demonstrated to be a component of the IL-4 receptor on the basis of chemical cross-linking data, the ability of IL-2R gamma to augment IL-4 binding affinity, and the requirement for IL-2R gamma in IL-4-mediated phosphorylation of insulin receptor substrate-1. The observation that IL-2R gamma is a functional component of the IL-4 receptor, together with the finding that IL-2R gamma associates with the IL-7 receptor, begins to elucidate why deficiency of this common gamma chain (gamma c) has a profound effect on lymphoid function and development, as seen in X-linked severe combined immunodeficiency.

Animals↗