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)

We have designed a single polymerase chain reaction (PCR) primer pair that detects the MLL/AF-4 fusion mRNA encoded by the derivative 11 chromosome from t(4;11)(q21;q23) leukemia cells using the reverse transcriptase PCR technique. PCR amplification was possible in seven of seven cells studied. Sequencing of the amplified products showed three different breakpoints on 11q23 and three on 4q21, resulting in six unique fusion sequences. All fusion sequences maintained an open reading frame. The areas of the MLL and AF-4 genes that are conserved in all derivative 11 fusion RNAs and therefore likely to contribute to the function of the oncogenic fusion protein are centromeric regions of MLL through exon 6 (retaining the AT hook motif) and telomeric regions of AF-4 beginning at codon 491 (containing nuclear localization and GTP-binding motifs). A single primer pair was able to detect the derivative 11 fusion transcript in seven of seven cases of t(4;11) acute leukemia tested. Given the variability shown in specific fusion sequences, studies correlating differential exon usage with clinical parameters will require different fusion-specific oligonucleotides or PCR primer pairs.
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PMID:Heterogeneity in MLL/AF-4 fusion messenger RNA detected by the polymerase chain reaction in t(4;11) acute leukemia. 835 9

Various heterotrimeric GTP-binding proteins may have important functions in hematopoietic cells. There has been no comprehensive information, however, regarding their expression in various-lineage hematopoietic cells. In this report, the expression level of seven G protein alpha subunits (Gs alpha, Gi1 alpha, Gi2 alpha, Gi3 alpha, Go alpha-1, Go alpha-2, and Gx alpha) in 13 hematopoietic cell lines were analyzed by Northern blot analysis. Gi1 alpha, Go alpha-1, Go alpha-2, and Gx alpha, were expressed in a limited number of cell lines whereas Gs alpha, Gi2 alpha, and Gi3 alpha were expressed ubiquitously in nearly all cell lines tested. Gi1 alpha was expressed selectively in a pre-T cell line, P30/PHK among lymphoid-lineage cell lines and a myeloblastic cell line, KG-1 among myelomonocytoid cell lines. Go alpha-1 was expressed only in a chronic myelocytic-leukemia cell line, K-562, whereas Go alpha-2 was not expressed in any cell lines tested after ordinary exposure of autoradiography (within 4 days). Gx alpha was expressed abundantly in a rat basophilic-leukemia cell line, RBL-2H3, and expressed in K-562. A barely detectable amount of Gx alpha messenger ribonucleic acid (mRNA) was found after a long exposure of autoradiography in several cell lines with megakaryoblastoid phenotype.
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PMID:Analysis of the expression of seven G protein alpha subunit genes in hematopoietic cells. 836 97

Formyl peptides stimulate binding of the stable GTP analogue, guanosine 5'-O-[gamma-thio]triphosphate (GTP[S]), to G-proteins in membranes of myeloid differentiated human leukaemia (HL-60) cells. On the other hand, agonist-activated formyl peptide receptors can also cause rapid and substantial release of GTP[S] bound to HL-60 membrane G-proteins. For fMet-Leu-Phe-stimulated dissociation of labelled GTP[S], an additional guanine nucleotide, in the potency order, unlabelled GTP[S] >> GTP >> guanosine 5'-[beta,gamma-imino]triphosphate > or = guanosine 5'-O-[beta-thio]diphosphate > or = GDP > GMP = ATP (no effects at 1 mM), was absolutely necessary. While with unlabelled GTP[S] and GTP similar concentrations were required for control and fMet-Leu-Phe-stimulated release, about 50-100-fold higher concentrations of the other nucleotides were necessary for agonist-stimulated than for basal release of bound GTP[S]. The receptor action appeared to be catalytic, required Mg2+ and was pertussis toxin sensitive. The data indicate that binding of GTP[S] to HL-60 membrane G-proteins is reversible and that agonist-activated formyl peptide receptors can interact, either directly or indirectly, with GTP[S]-liganded Gi-proteins, resulting in release of bound GTP[S].
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PMID:Receptor-stimulated dissociation of GTP[S] from Gi-proteins in membranes of HL-60 cells. 837 24

Accumulating evidence indicates that the activation of cellular oncogenes is a cause of some human cancers. ErbB-1, erbB-2 and abl oncogenes encoding tyrosine kinases, ras oncogenes encoding GTP binding proteins and myc oncogenes whose functions are not well understood are some examples. Therefore, agents which inhibit the activity of these oncogene products may provide new means to overcome certain human tumors. Herbimycin A and tyrphostins have been found and developed as inhibitors of tyrosine kinases and the effectiveness of these agents against tumors of Ph1-positive leukemia (CML, ALL) or squamous cell carcinomas has been reported. Although specific inhibitors of ras or myc oncogene products have not yet been described, recent studies on the processing of Ras proteins toward the cell membrane provide a strategy to search for inhibitors of ras functions.
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PMID:[Anticancer agents targeting oncogene products]. 837 83

The leukotriene (LT) B4 receptor has been characterized in the human monocyte leukemia THP-1 cell line. Scatchard analysis of [3H]LTB4 specific binding to THP-1 cell membranes revealed a single population of high affinity (KD = 56 pM) and saturable (2000 receptors/cell) binding sites. [3H]LTB4 specific binding was enhanced by divalent cations, but inhibited by both monovalent cations and a non-hydrolysable GTP analogue. Treatment with GTP analogue resulted in a concentration-dependent reduction in the number of high affinity binding sites, accompanied by the appearance of an equal number of binding sites of lower affinity (KD = 1250 pM). In contrast, Scatchard analysis with human polymorphonuclear leukocyte (PMN) membranes consistently revealed two populations of LTB4 receptors (KD = 48 pM and 270 pM). Treatment with GTP analogue, however, converted all these detectable binding sites to the lower affinity state. These data suggest that the LTB4 receptor in both THP-1 cell and PMN membranes exists in interconverting affinity states modulated by G-protein coupling. The similarity between the LTB4 receptors present in these two cell types was also substantiated by target-size analysis by radiation inactivation, which estimated a comparable molecular mass of 56.5 kDa and 52.8 kDa for the THP-1 cell and PMN LTB4 receptors, respectively. Finally, the presence of a single LTB4 receptor in PMN was demonstrated by direct photolabelling. Irradiation of frozen [3H]LTB4 equilibrium binding assay incubations resulted in complete photolysis of [3H]LTB4. Subsequent resolution of the tritiated PMN proteins by sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis (PAGE) revealed one major radioactive peak migrating with an apparent molecular weight of 61,000. This peak was identified as the LTB4 receptor since radiolabelling could be completely inhibited by the presence of excess unlabelled LTB4 or the LTB4-receptor antagonist, L-662,328. Photolabelling was also partially inhibited by pretreatment with GTP analogue, consistent with G-protein uncoupling reagents reducing receptor affinity without complete inhibition. In summary, the LTB4 receptor identified in human myeloid cells is a G-protein coupled receptor with interconvertible high and low affinity states, having a molecular mass of 53-61 kDa.
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PMID:Photoaffinity labelling and radiation inactivation of the leukotriene B4 receptor in human myeloid cells. 838 43

The leukotriene D4 receptor has been fully characterized by radioligand binding in membrane preparations from dimethyl sulphoxide-differentiated U937 cells, a human monocyte leukemia cell line, and, in parallel experiments, compared with leukotriene D4 receptor found in human lung and guinea-pig lung preparations. [3H]Leukotriene D4 specific binding in differentiated U937 cell membranes is of high affinity (KD = 0.35 nM), saturable (Bmax = 287 fmol/mg protein), with differentiation resulting in a 3-5-fold increase in the number of detectable binding sites. [3H]Leukotriene D4-specific binding in differentiated U937 cell membranes displays several features of G-protein-coupled receptors, being inhibited by GTP analogues and sodium ions, but increased by divalent cations. These characteristics are shared with [3H]leukotriene D4-specific binding in human and guinea-pig lung preparations. However, differences between these leukotriene D4 receptor types were observed. [3H]Leukotriene D4 equilibrium binding to differentiated U937 cell membranes could be dissociated to non-specific binding levels by 1000-fold excess of competing ligand, whereas binding to guinea-pig lung membranes was only partially dissociated under these conditions. In addition, differences in potency were demonstrated in competition studies with leukotriene E4 and leukotriene C4, although leukotriene D4 and the leukotriene D4-receptor antagonists MK-571 and ICI 204,219 were equipotent in competing for [3H]leukotriene D4-specific binding in all three membranes preparations. In conclusion, the leukotriene D4 receptor in differentiated U937 cell membranes resembles that in human lung, validating the use of this cell line as a suitable source of receptor in the development of potent specific antagonists.
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PMID:Characterization of the leukotriene D4 receptor in dimethylsulphoxide-differentiated U937 cells: comparison with the leukotriene D4 receptor in human lung and guinea-pig lung. 838 68

Deoxycytidine kinase is a key anabolic enzyme for the activation of ara-C and other antitumor drugs, as well as normal purine and pyrimidine deoxynucleotides. Previously, two forms of the kinase have been identified; deoxycytidine kinase I (70 kDa) and deoxycytidine kinase II (70 kDa). Deoxycytidine kinase I utilized dCyd and ara-C as substrates, while deoxycytidine kinase II used dCyd and dThd as substrates. Deoxycytidine kinase kinase II had very low activity on ara-C as a substrate. We report a procedure for the purification of a novel deoxycytidine kinase (52 kDa) from isolated human peripheral blood leukemia cell mitochondria. This enzyme has activity similar to deoxycytidine kinase II. The enzyme was extracted from the mitochondria with digitonin (1 mg/8 mg protein) and 0.3 M NaCl, and the extract was purified by DEAE-cellulose chromatography and thymidine-Sepharose affinity chromatography. This procedure produced a near homogeneous enzyme preparation with a yield of 70%. The mitochondrial deoxycytidine kinase was localized to the outer mitochondrial membrane. The enzyme phosphorylated dCyd (Km = 17 microM), however, ara-C was not a good substrate for the mitochondrial deoxycytidine kinase. ATP was the best phosphate donor, whereas dCTP and dTTP were potent inhibitors of mitochondrial deoxycytidine kinase. In contrast, phosphorylation of ara-C by deoxycytidine kinase I utilized GTP, dGTP, or ATP as a phosphate donor.
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PMID:Purification and characterization of deoxycytidine kinase from acute myeloid leukemia cell mitochondria. 839 94

Studies from several laboratories have revealed that structurally diverse substances including the wasp venom, mastoparan (MP), activate purified regulatory heterotrimeric guanine nucleotide-binding proteins (G-proteins) in a receptor-independent manner, presumably by mimicking the effects of heptahelical receptors. Mast cells and differentiated HL-60 human leukemic cells are useful model systems for the analysis of receptor-independent G-protein activation. We compared the effects of 2-phenylhistamines which are cationic-amphiphilic, too, and of MP on G-protein activation in dibutyryl cAMP-differentiated HL-60 cells and in the rat basophilic leukemia cell line, RBL 2H3. In HL-60 cells, 2-phenylhistamines show stimulatory effects which resemble those of formyl peptide receptor agonists but which cannot be attributed to agonism at classical receptors. 2-phenylhistamines do not, however, activate RBL 2H3 cells and various other myeloid cell types, pointing to cell type-specificity of receptor-independent G-protein activation. In HL-60 cells, MP shows effects on G-protein activation which differ substantially from those of formyl peptides. In RBL 2H3 membranes, MP shows similar effects on G-protein activation as in HL-60 membranes. We develop a model according to which receptor-independent G-protein activation can be subdivided into direct and indirect receptor-independent G-protein activation. In case of the former mechanism, substances like 2-phenylhistamines interact with G-protein alpha-subunits and in case of the latter mechanism, substances like MP interact with nucleoside diphosphate kinase which catalyzes the formation of GTP. This newly formed GTP is then transferred to, and cleaved by, G-protein alpha-subunits.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Direct and indirect receptor-independent G-protein activation by cationic-amphiphilic substances. Studies with mast cells, HL-60 human leukemic cells and purified G-proteins. 852 95

Ras (Ha-Ras, Ki-Ras, N-Ras) is implicated in the regulation of various cell functions such as gene expression and cell proliferation downstream from specific extracellular signals. Here, we partially purified a Ras-interacting protein with molecular mass of about 180 kDa (p180) from bovine brain membrane extract by glutathione S-transferase (GST)-Ha-Ras affinity column chromatography. This protein bound to the GTP gamma S (guanosine 5'-(3-O-thio)triphosphate, a nonhydrolyzable GTP analog).GST-Ha-Ras affinity column but not to those containing GDP.GST-Ha-Ras or GTP gamma S.GST-Ha-Ras with a mutation in the effector domain (Ha-RasA38). The amino acid sequences of the peptides derived from p180 were almost identical to those of human AF-6 that is identified as the fusion partner of the ALL-1 protein. The ALL-1/AF-6 chimeric protein is the critical product of the t (6:11) abnormality associated with some human leukemia. AF-6 has a GLGF/Dlg homology repeat (DHR) motif and shows a high degree of sequence similarity with Drosophila Canoe, which is assumed to function downstream from Notch in a common developmental pathway. The recombinant N-terminal domain of AF-6 and Canoe specifically interacted with GTP gamma S.GST-Ha-Ras. The known Ras target c-Raf-1 inhibited the interaction of AF-6 with GTP gamma S.GST-Ha-Ras. These results indicate that AF-6 and Canoe are putative targets for Ras.
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PMID:Identification of AF-6 and canoe as putative targets for Ras. 855 59

Individuals with neurofibromatosis type 1 (NF1) are predisposed to certain cancers including juvenile chronic myelogenous leukaemia (JCML). The NF1 tumour-suppressor gene encodes a protein (neurofibromin) that accelerates GTP hydrolysis on Ras proteins. Here we show that primary leukaemic cells from children with NF1 show a selective decrease in NF1-like GTPase activating protein (GAP) activity for Ras but retain normal cellular GAP activity. Leukaemic cells also show an elevated percentage of Ras in the GTP-bound conformation. JCML cells are hypersensitive to granulocyte-macrophage colony stimulating factor (GM-CSF), and we observed a similar pattern of aberrant growth in haematopoietic cells from Nf1-/- mouse embryos. These data define a specific role for neurofibromin in negatively regulating GM-CSF signaling through Ras in haematopoietic cells and they suggest that hypersensitivity to GM-CSF may be a primary event in the development of JCML.
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PMID:Loss of NF1 results in activation of the Ras signaling pathway and leads to aberrant growth in haematopoietic cells. 856 51


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