Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The surface engagement of high affinity immunoglobulin E receptor (Fc epsilon RI) of rat basophilic leukemia 2H3 (RBL-2H3) cells induced histamine secretion and leukotriene release following activation of the tyrosine kinase Lyn together with phosphatidylinositol 3-kinase (PI3-kinase). Wortmannin inhibited the activity of partially purified PI3-kinase from calf thymus, as well as the PI3-kinase activity in anti-PI3-kinase p85 immunoprecipitates from RBL-2H3 cells, at a concentration as low as 1.0 nM and with IC50 values of 3.0 nM, but did not inhibit PI4-kinase activity. The inhibition of PI3-kinase by wortmannin was irreversible. Wortmannin inhibited both Fc epsilon RI-mediated histamine secretion and leukotriene release up to 80% with IC50 values of 2.0 and 3.0 nM, respectively. Wortmannin inhibited PI3-kinase activity in intact cells up to 80% with an IC50 value of 2.0 nM, which is almost equal to those for PI3-kinase in vitro and for histamine secretion and leukotriene release. With anti-wortmannin antibody, we have shown that wortmannin binds to the 110-kDa protein, but not to PI3-kinase 85-kDa regulatory subunit both in vitro and in whole cells. Furthermore, there was a positive correlation between the potencies of wortmannin derivatives as inhibitors of PI3-kinase and as inhibitors of histamine secretion. Wortmannin had no effect on the activation of the tyrosine kinase Lyn. These results suggest that PI3-kinase is involved in the signal transduction pathway responsible for histamine secretion following stimulation of Fc epsilon RI and that wortmannin blocks these responses through direct interaction with the catalytic subunit of this enzyme.
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PMID:Inhibition of histamine secretion by wortmannin through the blockade of phosphatidylinositol 3-kinase in RBL-2H3 cells. 750 89

The c-kit proto-oncogene encodes a receptor tyrosine kinase that is known to play a crucial role in mast cell growth and differentiation. In a human mast cell leukemia cell line (HMC-1), KitR was found to be constitutively phosphorylated on tyrosine, activated and associated with phosphatidylinositol 3-kinase (P13K) in the absence of autocrine production of SCF. Sequencing of c-kit cDNA revealed that c-kit genes of HMC-1 cells were composed of a normal, wild-type allele and a mutant allele with two point mutations in codon 560 and codon 816, resulting in intracellular amino acid substitutions of Gly-560 for Val and Val-816 for Asp, respectively. Murine c-kit mutants encoding Gly-559 and/or Val-814, corresponding to human Gly-560 and/or Val-816, were constructed by site-directed mutagenesis and expressed in cells of a human embryonic kidney cell line (293T). In the transfected cells, KitR (Gly-559 + Val-814) and KitR (Val-814) were strikingly phosphorylated on tyrosine and activated in the absence of SCF, whereas tyrosine phosphorylation and activation of KitR (Gly-559) or wild-type KitR was modest or little, respectively. These results suggest that constitutive activation of KitR in HMC-1 results from the activating mutations of c-kit gene, and raise the possibility that the activating mutations, particularly at codon 814 of murine c-kit or at codon 816 of human c-kit, may participate in oncogenesis of mast cells.
Leukemia 1994 Apr
PMID:Activating mutations of the c-kit proto-oncogene in a human mast cell leukemia cell line. 751 80

Because mutations in receptor tyrosine kinases may contribute to cellular transformation, studies were undertaken to examine c-kit in human leukemia. Isoforms of c-kit have been characterized in the human megakaryoblastic leukemia cell line M-07. Deletion of the four amino acids Gly-Asn-Asn-Lys in the extracellular domain represents an alternatively spliced isoform that has been shown by others, in mice, to be associated with constitutive receptor autophosphorylation (Reith et al, EMBO J 10:2451, 1991). Additional isoforms differ in the inclusion or exclusion of a serine residue in the interkinase domain, a region that contains the binding site for phosphatidylinositol 3-kinase. By RNase protection analysis, we have shown coexpression of the Gly-Asn-Asn-Lys+ and Gly-Asn-Asn-Lys- isoforms, with dominance of the Gly-Asn-Asn-Lys- transcript, in normal human bone marrow, normal melanocytes, a range of tumor cell lines, and the blasts of 23 patients with acute myeloid leukemia. Analysis of transcripts for the Ser+ and Ser- isoforms also showed coexpression in all normal and leukemic cells examined. The ratios of isoform expression for both the Gly-Asn-Asn-Lys and Ser variants were relatively constant, providing no evidence in the tumors examined that upregulation of one isoform contributes to the neoplastic process.
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PMID:Expression of isoforms of the human receptor tyrosine kinase c-kit in leukemic cell lines and acute myeloid leukemia. 768 88

Treatment of rat basophilic leukemia (RBL) 2H3-hm1 cells with Clostridium difficile toxin B (2 ng/ml), which reportedly depolymerizes the actin cytoskeleton, blocked [3H]serotonin release induced by 2,4-dinitrophenyl-bovine serum albumin, carbachol, mastoparan, and reduced ionophore A23187-stimulated degranulation by about 55-60%. In lysates of RBL cells, toxin B 14C-glucosylated two major and one minor protein. By using two-dimensional gel electrophoresis and immunoblotting, RhoA and Cdc42 were identified as protein substrates of toxin B. In contrast to toxin B, Clostridium botulinum transferase C3 that selectively inactivates RhoA by ADP-ribosylation did not inhibit degranulation up to a concentration of 150 microg/ml. Antigen-stimulated tyrosine phosphorylation of a 110-kDa protein was inhibited by toxin B as well as by the phosphatidylinositol 3-kinase inhibitor wortmannin. Depolymerization of the microfilament cytoskeleton of RBL cells by C. botulinum C2 toxin or cytochalasin D resulted in an increased [3H]serotonin release induced by antigen, carbachol, mastoparan, or by calcium ionophore A23187, but without affecting toxin B-induced inhibition of degranulation. The data indicate that toxin B inhibits activation of RBL cells by glucosylation of low molecular mass GTP-binding proteins of the Rho subfamily (most likely Cdc42) by a mechanism not involving the actin cytoskeleton.
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PMID:Inhibition of Fc epsilon-RI-mediated activation of rat basophilic leukemia cells by Clostridium difficile toxin B (monoglucosyltransferase) 863 52

CD28/B7 interactions have been demonstrated to provide a co-stimulatory signal for the generation of CD8+ cytotoxic T lymphocytes in the absence of CD4+ T helper cells. The CD28 signals required for induction of cytotoxicity have yet to be described. To investigate further the biochemical signaling pathways associated with CD28-dependent cytotoxicity, we have studied the human thymic leukemia cell line, YT. YT cells kill B7+ targets in a non-major histocompatibility complex (MHC)-restricted, CD28-dependent manner. CD28 ligation on the surface of YT cells caused a rapid increase in the tyrosine phosphorylation of four major cellular substrates with masses estimated to be 110, 95, 85, and 44 kDa. The 110 and 85 kDa substrates were identified as the catalytic and regulatory subunits, respectively, of phosphatidylinositol 3-kinase (PI3-K). Engagement of CD28 caused the rapid receptor association and activation of PI3-K but did not activate phospholipase C gamma. CD28-induced tyrosine phosphorylation and PI3-K activation was independent of p56lck protein tyrosine kinase (PTK) activity (previously reported to be associated with CD28) and was insensitive to inhibition by the PTK inhibitor herbimycin A. Two structurally and mechanistically dissimilar inhibitors of PI3-K, wortmannin and 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002) also failed to block CD28-dependent tyrosine phosphorylation events or the association of PI3-K with the CD28 receptor. However, both drugs inhibited CD28-dependent cytotoxicity and CD28 receptor associated PI3-K activity with IC50 values similar to the reported IC50 values for PI3-K inhibition. Although herbimycin A did not significantly block the observed CD28-dependent tyrosine phosphorylation or PI3-K activation, herbimycin did block CD28-dependent cytotoxicity in a dose-dependent manner. These data support a role for PI3-K activation in the CD28-dependent initiation of cytotoxic effector function and suggest that a herbimycin sensitive step(s) is either CD28-independent, resides within a PI3-K-independent CD28 signaling pathway, or is downstream of CD28-dependent PI3-K activation.
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PMID:CD28-dependent killing by human YT cells requires phosphatidylinositol 3-kinase activation. 864 5

Exocytosis of secretory granules, including histamine, in rat basophilic leukemia (RBL-2H3) cells, which exhibit Ca(2+)-dependent secretion of granules when stimulated with antigen or Ca(2+)-ionophore (A23187), was observed under a video-enhanced light microscope. Exocytotic events of individual granules including fusion, extrusion, and membrane retrieval were visualized in individual cells stimulated with antigen or A23187. Exocytosis of granules stimulated with A23187 showed two peaks in its time courses. The earlier one of the peaks was inhibited by wortmannin ( > 100 nM), as an inhibitor of myosin light chain kinase (MLCK), and the other was not. Exocytosis by antigen-stimulation, however, showed only one peak, which was inhibited by low concentration of wortmannin ( < 50 nM) as an inhibitor of phosphatidylinositol 3-kinase (PI3-kinase). These results indicate that quantitative analysis of exocytosis visualized by video-enhanced light microscope reveals two different pathways, through P13-kinase and MLCK, of inhibitory effects on exocytosis by wortmannin in RBL-2H3 cells.
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PMID:Different pathways of inhibitory effects of wortmannin on exocytosis are revealed by video-enhanced light microscope. 867 Jan 90

Previously, we have demonstrated that tyrosine phosphorylation of 78 and 92 kDa proteins in rat basophilic leukemia cells (RBL-2H3) is involved in a signal transduction system for high-affinity IgE receptor (Fc epsilon RI)-mediated histamine secretion. However, it is not clarified whether the tyrosine phosphorylation of 78 and 92 kDa proteins in RBL-2H3 cells is regulated by activation of protein kinase C (PKC) or phosphatidylinositol 3-kinase (PI3-kinase). In this study, therefore, the effect of depletion of PKC in RBL-2H3 cells, or the influence of PKC, PI3-kinase and tyrosine kinase inhibitors on histamine release from RBL-2H3 cells was examined. The elimination of PKC in RBL-2H3 cells induced significant suppression of histamine release, although the tyrosine phosphorylation of 78 and 92 kDa proteins was not inhibited. The inhibition of histamine release was also observed by the treatment with a PKC inhibitor such as H-7, calphostin C, a PI3-kinase inhibitor such as wortmannin or a tyrosine kinase inhibitor such as ST638, genistein, hervimycin A, although the tyrosine phosphorylation of both proteins was inhibited by only ST638. These results suggest that the 78 kDa protein in RBL-2H3 cells is not identical to the protein-tyrosine kinase PTK72 and the tyrosine phosphorylation of 78 and 92 kDa proteins in RBL-2H3 cells occurs upstream of PKC and PI3-kinase activation or is regulated independently of the PKC- and PI3-kinase-dependent signaling pathway.
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PMID:The characterization of tyrosine phosphorylation of 78 and 92 kDa proteins in rat basophilic RBL-2H3 cells. 889 56

Signaling by the CD28 T cell costimulatory receptor is known to involve recruitment and activation of phosphatidylinositol 3-kinase (PI3-kinase) which is dependent upon phosphorylation of tyrosine 173 of the CD28 cytoplasmic tail, present in a YMNM motif. However, whether this phosphorylation is required for CD28 costimulation and whether or not phosphorylation of any of the other three tyrosines of the CD28 cytoplasmic tail (tyrosines 188, 191 and 200) is also important for CD28 induced responses is unclear. To address this we examined the ability of chimeric receptors, consisting of the extracellular plus transmembrane membrane domain of human CD8 alpha linked to different mutated human CD28 cytoplasmic tails, to induce IL-2 secretion in Jurkat T leukemia cells in the presence of PMA and ionomycin. A receptor in which tyrosine 173 of the CD28 tail was mutated to phenylalanine was able to induce IL-2. By contrast, receptors which contained single tyrosine 188, 191 or 200 to phenylalanine substitutions were unable to induce IL-2. These results imply that in this system phosphorylation of tyrosine 173 and hence activation of PI3-kinase is not required for CD28 induced IL-2 secretion. Further, they imply that phosphorylation of each of tyrosines 188, 191 and 200 is necessary for this response. Despite an apparent requirement for phosphorylation of all three of these tyrosines, however, receptors which contain tyrosine only at positions 191 or 200 and a truncated receptor which does not contain tyrosine 200 induce normal IL-2. These last findings, therefore, illustrate the complexity of CD28 mediated activation signals.
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PMID:Phosphorylation of each of the distal three tyrosines of the CD28 cytoplasmic tail is required for CD28-induced T cell IL-2 secretion. 894 78

New C-11 esters of the fermentation product wortmannin have been synthesized, with some of them further derivatized at C-17. The new esters show greater inhibition of isolated phosphatidylinositol 3-kinase and increased cell cytotoxicity in a rapidly proliferating leukemia cell line, when compared to wortmannin. Reduction of the C-17 ketone caused a slight increase in activity, while acylation of this new alcohol caused severe loss of activity. With their increased activity, the new C-11 esters may be good candidates to explore the in vivo antitumor effects of phosphatidylinositol 3-kinase inhibitors.
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PMID:Synthesis and in vitro evaluation of new wortmannin esters: potent inhibitors of phosphatidylinositol 3-kinase. 896 May 64

The CD28 cell surface receptor provides an important costimulatory signal for T cells necessary for their response to Ag. Early events in CD28 signaling include recruitment and activation of phosphatidylinositol 3-kinase (PI3-kinase) and activation of the protein tyrosine kinases (PTKs), LCK and EMT. Recruitment and activation of PI3-kinase is known to be dependent upon phosphorylation of tyrosine 173 of the CD28 cytoplasmic tail contained within a YMNM motif. By contrast, little is known of which residues of the CD28 tail, including tyrosines, are required for the activation of PTKs. To address this we studied the ability of truncation mutants and tyrosine to phenylalanine substitution mutants of the CD28 cytoplasmic tail to activate LCK and EMT in Jurkat T leukemia cells. Our results indicate that 1) activation of EMT is partially dependent upon tyrosine 173 of the CD28 tail, although it does not require PI3-kinase activation; 2) activation of LCK is independent of CD28 cytoplasmic tail tyrosine residues; and 3) elements sufficient for the activation of both kinases are contained within the first half of the tail. In addition we studied the CD28 tail as a substrate for both PTKs in in vitro kinase assays. We demonstrate that EMT can phosphorylate all four tyrosines of the CD28 tail, in contrast to LCK, which phosphorylates only tyrosine 173. Together with evidence that in vivo, tyrosines other than tyrosine 173 become phosphorylated following CD28 stimulation, this finding suggests that, like LCK, one function of EMT during CD28 signaling is phosphorylation of the receptor.
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PMID:Analysis of CD28 cytoplasmic tail tyrosine residues as regulators and substrates for the protein tyrosine kinases, EMT and LCK. 899 71


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