Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The interleukin-2 (IL-2) receptor (IL-2R) consists of three distinct subunits (alpha, beta, and gamma c) and regulates proliferation of T lymphocytes. Intracellular signalling results from ligand-mediated heterodimerization of the cytoplasmic domains of the beta and gamma c chains. To identify the residues of gamma c critical to this process, mutations were introduced into the cytoplasmic domain, and the effects on signalling were analyzed in the IL-2-dependent T-cell line CTLL2 and T-helper clone D10, using chimeric IL-2R chains that bind and are activated by granulocyte-macrophage colony-stimulating factor. Whereas previous studies of fibroblasts and transformed T cells have suggested that signalling by gamma c requires both membrane-proximal and C-terminal subdomains, our results for IL-2-dependent T cells demonstrate that the membrane-proximal 52 amino acids are sufficient to mediate a normal proliferative response, including induction of the proto-oncogenes c-myc and c-fos. Although gamma c is phosphorylated on tyrosine upon receptor activation and could potentially interact with downstream molecules containing SH2 domains, cytoplasmic tyrosine residues were dispensable for mitogenic signalling. However, deletion of a membrane-proximal region conserved among other cytokine receptors (cytoplasmic residues 5 to 37) or an adjacent region unique to gamma c (residues 40 to 52) abrogated functional interaction of the receptor chain with the tyrosine kinase Jak3. This correlated with a loss of all signalling events analyzed, including phosphorylation of the IL-2R beta-associated kinase Jak1, expression of c-myc and c-fos, and induction of the proliferative response. Thus, it appears in T cells that Jak3 is a critical mediator of mitogenic signaling by the gamma c chain.
Mol Cell Biol 1996 Jan
PMID:A membrane-proximal region of the interleukin-2 receptor gamma c chain sufficient for Jak kinase activation and induction of proliferation in T cells. 852 10

Thrombopoietin (TPO) is the major regulator of growth and differentiation of megakaryocytes. To identify functionally important regions in the cytoplasmic domain of the TPO receptor, mpl, we introduced wild-type mpl and deletion mutants of murine mpl into the granulocyte-macrophage colony-stimulating factor (GM-CSF)- or erythropoietin (EPO)-dependent human cell line UT7. TPO induced differentiation of UT7-Wtmpl cells, not parental UT7 cells, along the megakaryocytic lineage, as evidenced by decreased proliferation, changes in cell morphology, and increased surface expression and mRNA levels of megakaryocytic markers CD41, CD61, and CD42b. When UT7-mpl cells were cultured long-term in EPO instead of GM-CSF, the TPO effect was dominant over that of EPO. Moreover, the differentiation induced by TPO was more pronounced for cells shifted from EPO to TPO than for cells shifted from GM-CSF to TPO, as shown by the appearance of polyploid cells. Mutational analysis of the cytoplasmic domain of mpl showed that proliferation and maturation functions of mpl can be uncoupled. Two functional regions were identified: (i) the first 69 amino acids comprising the cytokine receptor motifs, box I and box 2, which are necessary for both TPO-induced mitogenesis and maturation; and (ii) amino acids 71 to 94, which are dispensable for proliferation but required for differentiation. Surprisingly, however, EPO could complement this latter domain for TPO-induced differentiation, suggesting a close relationship between EPO and TPO signaling.
Mol Cell Biol 1996 May
PMID:Functional regions of the mouse thrombopoietin receptor cytoplasmic domain: evidence for a critical region which is involved in differentiation and can be complemented by erythropoietin. 862 15

The human interleukin-3 receptor (IL-3R) is a heterodimer that comprises an IL-3 specific alpha chain (IL-3R alpha) and a common beta chain (beta C) that is shared with the receptors for granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-5. These receptors belong to the cytokine receptor superfamily, but they are structurally and functionally more related to each other and thus make up a distinct subfamily. Although activation of the normal receptor occurs only in the presence of ligand, the underlying mechanisms are not known. We show here that human IL-3 induces heterodimerization of IL-3R alpha and beta c and that disulfide linkage of these chains is involved in receptor activation but not high-affinity binding. Monoclonal antibodies (MAb) to IL-3R alpha and beta c were developed which immunoprecipitated, in the absence of IL-3, the respective chains from cells labelled with 125I on the cell surface. However, in the presence of IL-3, each MAb immunoprecipitated both IL-3R alpha and beta c. IL-3-induced receptor dimers were disulfide and nondisulfide linked and were dependent on IL-3 interacting with both IL-3R alpha and beta c. In the presence of IL-3 and under nonreducing conditions, MAb to either IL-3R alpha or beta c immunoprecipitated complexes with apparent molecular weights of 215,000 and 245,000 and IL-3R alpha and beta c monomers. Preincubation with iodoacetamide prevented the formation of the two high-molecular-weight complexes without affecting noncovalent dimer formation or high-affinity IL-3 binding. Two-dimensional gel electrophoresis and Western blotting (immunoblotting) demonstrated the presence of both IL-3R alpha and beta c in the disulfide-linked complexes. IL-3 could also be coimmunoprecipitated with anti-IL-3R alpha or anti-beta c MAB, but it was not covalently attached to the receptor. Following IL-3 stimulation, only the disulfide-linked heterodimers exhibited reactivity with antiphosphotyrosine antibodies, with beta c but not IL-3R alpha being the phosphorylated species. A model of IL-3R activation is proposed which may be also applicable to the related GM-CSF and IL-5 receptors.
Mol Cell Biol 1996 Jun
PMID:Human interleukin-3 (IL-3) induces disulfide-linked IL-3 receptor alpha- and beta-chain heterodimerization, which is required for receptor activation but not high-affinity binding. 864 15

Transcription factors of the NFAT family play a key role in the transcription of cytokine genes and other genes during the immune response. We have identified two new isoforms of the transcription factor NFAT1 (previously termed NFATp) that are the predominant isoforms expressed in murine and human T cells. When expressed in Jurkat T cells, recombinant NFAT1 is regulated, as expected, by the calmodulin-dependent phosphatase calcineurin, and its function is inhibited by the immunosuppressive agent cyclosporin A (CsA). Transactivation by recombinant NFAT1 in Jurkat T cells requires dual stimulation with ionomycin and phorbol 12-myristate 13-acetate; this activity is potentiated by coexpression of constitutively active calcineurin and is inhibited by CsA. Immunocytochemical analysis indicates that recombinant NFAT1 localizes in the cytoplasm of transiently transfected T cells and translocates into the nucleus in a CsA-sensitive manner following ionomycin stimulation. When expressed in COS cells, however, NFAT1 is capable of transactivation, but it is not regulated correctly: its subcellular localization and transcriptional function are not affected by stimulation of the COS cells with ionomycin and phorbol 12-myristate 13-acetate. Recombinant NFAT1 can mediate transcription of the interleukin-2, interleukin-4, tumor necrosis factor alpha, and granulocyte-macrophage colony-stimulating factor promoters in T cells, suggesting that NFAT1 contributes to the CsA-sensitive transcription of these genes during the immune response.
Mol Cell Biol 1996 Jul
PMID:Recombinant NFAT1 (NFATp) is regulated by calcineurin in T cells and mediates transcription of several cytokine genes. 866 13

A central factor in the pathogenesis of inflammatory and fibrotic lung disease (adult respiratory distress syndrome, sarcoidosis, idiopathic pulmonary fibrosis) is the locally elevated number of alveolar macrophages (AM). An elevation in the production rate of AM, chemoattraction and differentiation of monocytes, or a diminution in the death rate might be underlying mechanisms. The aim of the present study was to investigate the modulatory role of endotoxin and cytokines on the death rate of human AM. Lipopolysaccharide (LPS) treatment resulted in a 4-fold increase (7.6 to 30.2%) of AM death. AM death was apoptotic as assessed by in situ DNA end labeling (ISDE), transmission electron microscopy, DNA gel electrophoresis, fluorometry of fragmented DNA, and an ELISA specific for histone-associated DNA fragments. Among the different bacterial cell wall components tested, LPS was the only inducer of apoptosis in human AM. None of the tested cytokines (interleukin-1 beta [IL-1 beta], IL-4, IL-6, IL-10, tumor necrosis factor-alpha [TNF-alpha], transforming growth factor-beta 2 [TGF-beta 2], interferon-gamma [IFN-gamma], macrophage colony-stimulating factor [M-CSF], granulocyte colony-stimulating factor [G-CSF], and granulocyte-macrophage colony-stimulating factor [GM-CSF]) was capable of enhancing the spontaneous rate of apoptosis. However, LPS-induced apoptosis was significantly enhanced by the macrophage-activating cytokine IFN-gamma, and reduced by the macrophage-deactivating cytokines IL-4, IL-10, and TGF-beta.
Am J Respir Cell Mol Biol 1996 Jul
PMID:Apoptosis in human alveolar macrophages is induced by endotoxin and is modulated by cytokines. 867 23

Cytokines regulate cell growth and differentiation by inducing the expression of specific target genes. We have recently isolated a cytokine-inducible, immediate-early cDNA, DUB-1, that encodes a deubiquitinating enzyme. The DUB-1 mRNA was specifically induced by the receptors for interleukin-3, granulocyte-macrophage colony-stimulating factor, and interleukin-5, suggesting a role for the beta common (betac subunit known to be shared by these receptors. In order to identify the mechanism of cytokine induction, we isolated a murine genomic clone for DUB-1 containing a functional promoter region. The DUB-1 gene contains two exons, and the nucleotide sequence of its coding region is identical to the sequence of DUB-1 cDNA. Various regions of the 5' flanking region of the DUB-1 gene were assayed for cytokine-inducible activity. An enhancer region that retains the beta c-specific inducible activity of the DUB-1 gene was identified. Enhancer activity was localized to a 112-bp fragment located 1.4 kb upstream from the ATG start codon. Gel mobility shift assays revealed two specific protein complexes that bound to this minimal enhancer region. One complex was induced by betac signaling, while the other was noninducible. Finally, the membrane-proximal region of human betac was required for DUB-1 induction. In conclusion, DUB-1 is the first example of an immediate-early gene that is induced by a specific subunit of a cytokine receptor. Further analysis of the DUB-1 enhancer element may reveal specific determinants of a betac-specific signaling pathway.
Mol Cell Biol 1996 Sep
PMID:The murine DUB-1 gene is specifically induced by the betac subunit of interleukin-3 receptor. 875 39

The growth and differentiation of mast cells are regulated by cytokines produced in tissue microenvironments. We previously reported that mast cells isolated from the epithelial compartment of nasal polyp tissue contain significantly less tryptase when compared with mast cells isolated from the stroma of the same tissue. In an attempt to explore this finding, we analyzed the ability of supernatants obtained from cultured nasal polyp epithelial cells (NP-EpCM) or nasal polyp fibroblasts (NP-FbCM) to regulate the tryptase content of the immature human mast cell line HMC-1. HMC-1 cells were cultured for 7 days in Iscove's modified Dulbecco's medium (IMDM) with 30% of either NP-FbCM or NP-EpCM or 20% MoCM (supernatant of a leukemic T cell line). As assessed by radioimmunoassay and test for enzymatic activity, all three conditioned media were shown to significantly decrease tryptase protein expression in HMC-1, when compared with cultures performed with IMDM alone (NP-EpCM P < 0.001; NP-FbCM P < 0.04; MoCM P < 0.004). In addition, Northern blot analysis demonstrated lower tryptase mRNA levels upon exposure to all three conditioned media tested, suggesting that tryptase downregulation occurs at the transcriptional level. In further studies we found that preincubation of MoCM with anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) completely blocked the observed downregulation of tryptase expression mediated by this conditioned medium. The findings suggest that GM-CSF has a suppressive effect on expression of protease in mast cells, and may thus play a modulatory role in determining the extent of tissue inflammation in allergic airways disease.
Am J Respir Cell Mol Biol 1996 Sep
PMID:Specific inhibition of beta-tryptase expression in a human mast cell line by granulocyte-macrophage colony-stimulating factor produced by airways structural cells. 881 Jun 39

Tumor necrosis factor alpha(TNF alpha), a proinflammatory cytokine secreted predominantly by monocytemacrophages, interacts with two cell-surface receptors: TNF-R55 and TNF-R75. Few studies have been devoted to their modulation on human alveolar macrophages (AM). Both source and target of TNF(alpha), AM also release its inhibitors, the soluble receptors, following the cleavage of the extracellular domain of TNF-R55 and TNF-R75. Because in vivo AM are subject to activation by exogenous or endogenous stimuli, we analyzed the release of both receptors into the cell culture supernatant in response to lipopolysaccharide (LPS), phorbol myristate acetate (PMA), and cytokines such as interleukin 2(IL-2), IL-4, IL-6, granulocyte-macrophage colony-stimulating factor (GM-CSF), and interferon gamma (IFN-gamma). Results were compared with those obtained on peripheral blood monocytes (Mo), and the role of receptor recycling was investigated using inhibitors such as monensin and chloroquine. In our culture conditions, basal release by unstimulated AM amounted to 0.3 +/- 0.1 and 0.5 +/- 0.1 ng/ml for TNF-sR55 and TNF-sR75, respectively. In the same conditions, Mo released 1.2 +/- 1.2 ng/ml of TNF-sR55 and 5.1 +/- 0.1 ng/ml of TNF-sR75. PMA slightly increased mRNA expression and release of TNF-sR55, but those of TNF-sR75 were enhanced approximately 4-fold. After 24 h of culture, the release of TNF-sR75 was 2.5-fold higher on Mo than on AM. Of the cytokines tested on AM, IFN-gamma increased the release of TNF-sR75 3-fold, but that of TNF-sR55 only between 1.5- and 2-fold. GM-CSF enhanced them to a lower extent (approximately 1.5-fold). Shedding occurred despite the presence of chloroquine, monensin and colchicine, suggesting that cleavage takes place on the cell surface rather than after internalization. Addition of colchicine increased the release of TNF-sR75 induced by LPS and IFN-gamma, but not by PMA. In conclusion, Mo and AM differ in their ability to release TNF(alpha) and TNF-sR. On AM the release of each receptor appears to be regulated separately. Finally, IFN-gamma was among the most efficacious cytokines to induce the release of both receptors, with TNF-sR75 being more liable to shedding. Thus, the two TNF-R seem to be ruled by separate mechanisms and to differ in terms of release sensitivity.
Am J Respir Cell Mol Biol 1996 Mar
PMID:Tumor necrosis factor soluble receptor 75: the principal receptor form released by human alveolar macrophages and monocytes in the presence of interferon gamma. 884 79

MHC class II+ lung dendritic cells (DC) increase in number following treatment of animals with interferon-gamma (IFN-gamma) [Kradin et al. (1991) Am. J. Resp. Mol. Biol. 4, 210; Gong et al. (1992)J. Exp. Med. 175, 797]. To test whether this is due to increased sequestration and/or trafficking of DC to the lung, bone marrow DC from BALB/c mice were obtained by culturing bone marrow with granulocyte-macrophage colony-stimulating factor (GM-CSF). Recipient BALB/c mice were injected intraperitoneally (i.p.) for 4 days with one of the following: IFN-gamma, dexamethasone (Dex), or phosphate-buffered saline (PBS). Twenty-four hours after the last dose, they were injected intravenously (i.v.) with carboxyfluorescein (F1) -labeled DC (1 x 10(6)/mouse) and killed 4 h later. DC, double immunostained for Ia and F1, were quantified by morphometry in frozen sections of lung. The number of injected dual-labeled DC/cm2 was reduced by 90% in IFN-gamma-treated mice. By contrast, there was no significant difference between Dex- and PBS-treated animals in the number of double-labeled DC retained in pulmonary capillaries. Biodistribution and imaging studies were conducted on IFN-gamma- and PBS-treated mice using 111In-labeled DC. Reduced radioactivity in the lung was accounted for by an equivalent increase in the liver of IFN-gamma-treated mice; imaging studies confirmed these observations. Removal of >80% of alveolar macrophages (AM) by pretreatment with intratracheally administered chlodronate-loaded liposomes did not change the biodistribution of DC in IFN-gamma- and PBS-injected mice. Serum levels of tumor necrosis factor-alpha (TNF-alpha and nitrite/nitrate in IFN-gamma-treated mice were similar to those of controls. Immunostaining for inducible nitric oxide synthase (iNOS), however, revealed a 1.5-and 6-fold increase in the number of positively stained cells in the lung and liver, respectively, of IFN-gamma-treated mice; the number of iNOS-expressing cells was markedly reduced in Dex-treated animals relative to controls. To test whether the systemic treatment with IFN-gamma stimulated the cytotoxic activity of Kupffer cells, mice were injected with chlodronate liposomes 5 days before death. After treating the mice in the ensuing 4 days with IFN-gamma or PBS, biodistribution and imaging studies with 111In-labeled DC were conducted on the 5th day. After administration of chlodronate liposomes, there was a significant increase in the radioactivity detected in the lungs of IFN-gamma-injected mice but not in those of PBS- injected controls, a finding confirmed by imaging studies. We conclude that IFN-gamma treatment augmented Kupffer cell cytotoxic activity, which, in turn, effectively reduced the number of injected DC in circulation, with the result that fewer of these cells were retained in the lung vasculature. We further conclude that IFN-gamma increases the number of Ia+ lung DC by up-regulating Ia expression of resident Ia- DC precursors and not by promoting the migration of circulating DC to the lung.
 ...
PMID:Interferon-gamma reduces Ia+ dendritic cell traffic to the lung. 886 37

Tyrosine phosphorylation and activation of the transcription factor Stat5 occur in response to stimuli like granulocyte-macrophage colony-stimulating factor, interleukin-3, or erythropoietin that stimulate both proliferation and differentiation of hematopoietic cells. It is unclear whether Stat5 is part of a proliferative response or part of the events leading to cellular differentiation. Here we report that agents promoting differentiation but not proliferation of hematopoietic cells, like phorbol ester or both types of interferons (IFNs), activate Stat5 in promonocytic U937 cells. Both IFN types caused tyrosine phosphorylation and DNA binding of predominantly one Stat5 isoform (Stat5a) despite expression of both Stat5a and Stat5b proteins. Monocytic differentiation of U937 cells led to a strong decrease in IFN-gamma-mediated activation of Stat5 but not of Stat1. Transactivation of Stat5-target genes occurred in response to IFN-gamma, which activates both Stat5 and Stat1, but not in response to granulocyte-macrophage colony-stimulating factor, which activates only Stat5. Tyrosine phosphorylation of Stat5 is not generally part of the IFN response. IFN-gamma did not cause Stat5 activation in HeLa cells, despite the expression of both Stat5 isoforms at similar levels. By contrast, IFN-alpha caused tyrosine phosphorylation and DNA binding of exclusively the b isoform of Stat5, and activated Stat5b formed a DNA binding activity previously found in HeLa cells and designated IFN-alpha activation factor 2. Taken together, our results demonstrate that ligand binding of IFN receptors leads to an isoform-specific activation of Stat5 in a restricted number of cell lineages. Moreover, they suggest that Stat5 might be part of the differentiation response of myeloid cells.
Mol Cell Biol 1996 Dec
PMID:Activation of different Stat5 isoforms contributes to cell-type-restricted signaling in response to interferons. 894 49


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>