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)

Earlier studies of murine leukemia viruses (MuLVs) have reported that a percentage of surface protein (SU) remains covalently associated with transmembrane protein (TM) through formation of disulfide bonds. Among MuLVs, there are three conserved cysteine residues within the extracellular domain of TM. These cysteine residues were substituted individually with serines to define their function and possible role in disulfide bonding with SU. Using oligonucleotide-directed mutagenesis, seven mutant constructs were generated with individual as well as multiple cysteine mutations. Transient transfection of all seven cysteine mutations resulted in nonviable virus. Analysis of intracellular proteins of producer mutant cell lines have demonstrated that precursor envelope protein (gPr80env; SU/TM) is being synthesized, but transport and processing of gPr80env is blocked in the endoplasmic reticulum. Two independent reversions of one cysteine mutation have been isolated and characterized.
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PMID:Analysis of cysteine mutations on the transmembrane protein of Moloney murine leukemia virus. 764 22

In this study, serotonin (5-HT) was found to diminish the intracellular calcium, [Ca2+]i, concentrations in a dose-dependent manner in Fura-2-loaded human leukemia (K 562) cells. Prior addition of verapamil (a calcium channel blocker) to the cells abolished the serotonin-induced response, suggesting that the diminution of free [Ca2+]i contents was due to the opening of calcium channels. Thapsigargin (an agent which increases [Ca2+]i via its action on endoplasmic reticulum) augmented the [Ca2+]i contents. Addition of serotonin before or after thapsigargin (THAP) curtailed the THAP-stimulated increases in [Ca2+]i, supporting the notion that 5-HT acts on the calcium channels and that it empties, in part, the THAP-stimulated calcium contents. Spiperone and NAN-190, antagonists to 5-HT1A receptor subtype, abolished the serotonin effects on calcium signaling, whereas an agonist to 5-HT1A receptor, 8OHDPAT, mimicked the serotonin-like action on the diminution of the intracellular calcium contents. These results indicate that the 5-HT response is mediated via 5-HT1A serotonergic receptors in these cells. Furthermore, we characterized the 5-HT receptors in K 562 cells. The specific binding of serotonin to these cells was saturable and hyperbolic. The Kd and the Bmax of serotonin binding were 100 nM and 1690 fmol/10(6) cells, respectively. 8-[3H]OH-DPAT also labeled these cells with a Bmax of 2.8 fmol/10(6) cells and a Kd of 20 nM. The specific binding of 8-[3H]OH-DPAT to K 562 cells was displaced by serotonin, 8OH-DPAT, and NAN-190. These results suggest that K 562 cells possess functional 5-HT1A receptors coupled with calcium signaling.
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PMID:Serotonin-induced calcium signaling via 5-HT1A receptors in human leukemia (K 562) cells. 767 19

Two anti-nerve growth factor receptor (LNGFR or p75NGFR) antibodies, Me20.4 and Me8211, label stromal cells with dendritic features in fresh smears and in formalin-fixed, paraffin-embedded human bone marrow (BM). The LNGFR+ cells have an oval nucleus, a scanty cytoplasm with long dendrites that intermingle with the hematopoietic cells, line the abluminal side of sinus endothelial cells, and provide the scaffold for the hematopoietic marrow. At the electron microscopy level, the immunogold tag labels the body and the long branching dendrites of fibroblast-like cells with scanty cytoplasm containing mitochondria, endoplasmic reticulum, and dense bodies. The LNGFR+ cells are positive for alkaline phosphatase, reticulin, collagen III, vimentin, TE-7, and CD13 but negative for endothelial (vWF, CD34, Pal-E), neural (CD56, neurofilament) and leukocyte markers (CD45, CD68). The LNGFR+ stromal cells appear in the fetal BM before the hematopoietic activity begins, originate from the vessel adventitia, and radiate in the Bm cavity. Long-term BM culture (LTBMC) in vitro contain LNGFR+ stromal cells. We document the presence of RNA message for the low- (LNGFR) and the high-affinity NGF receptor (NTRK1) by using RT-PCR on fresh BM aspirate and on LTBMC. BM biopsies from patients with hematologic fibrogenic diseases and in cytokine-treated cancer patients are evaluated for LNGFR+ cells: the amount of stained cells is correlated with the traditional reticulin stain in cases of myelofibrosis, therapy-related myelodysplasia, leukemia, and detected an increase of stromal cells in cytokine-treated patients. The anti-LNGFR antibodies represent a specific membrane marker for the adventitial reticular cells (ARC) of the human marrow and allow precise evaluation and quantitation of this important BM microenvironment component in vivo and in vitro.
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PMID:Bone marrow stroma in humans: anti-nerve growth factor receptor antibodies selectively stain reticular cells in vivo and in vitro. 768 1

It was previously shown that amino acids 609-613 (REDLK) at the C-terminus of Pseudomonas exotoxin (PE) are necessary for cytotoxicity, presumably by directing the toxin to the endoplasmic reticulum (ER) [Chaudhary, Jinno, FitzGerald and Pastan (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 308-312]. Using the anti-[interleukin 2 receptor (IL2R)] immunotoxin anti-Tac(Fv)-PE38 (AT-PE38REDLK), it was found that removing the terminal lysine did not alter the activity, but replacing REDL with KDEL, the most common ER retention sequence, increased activity. To determine which amino acid in KDEL was responsible for the increase in activity, we tested eight C-terminal mutants of AT-PE38REDLK. Using IL2R-bearing MT-1 cells, we found that the glutamate residue of KDEL was required for high activity, as the cytotoxicity of AT-PE38 ending in KDEL, RDEL, KEEL or REEL was much greater than that of AT-PE38 ending in REDL, KEDL, RDDL or KDDL. Using freshly isolated lymphocytic leukaemia cells, AT-PE38 ending in KDEL, REEL or RDEL was more than 100-fold more cytotoxic than AT-PE38 ending in KEDL, REDL, RDDL or the native sequence REDLK. The RDEL sequence also improved the cytotoxic activity of an interleukin 4-PE38 toxin fusion protein. Improved cytotoxic activity correlated with improved binding of the C-termini to the KDEL receptor on rat Golgi membranes. These data indicate that the glutamate residue of KDEL improves the cytotoxicity of PE by increasing binding to a sorting receptor which transports the toxin from the transreticular Golgi apparatus to the ER, where it is translocated to the cytosol and inhibits protein synthesis.
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PMID:Importance of the glutamate residue of KDEL in increasing the cytotoxicity of Pseudomonas exotoxin derivatives and for increased binding to the KDEL receptor. 771 88

We developed a novel method for analysis of hepatitis C viral proteinase activity in cultured cells, in which the proteinase activity was measured as the enhancement of reporter gene expression. In this system, plasmids encoding a reporter gene, the enzyme gene, and the substrate gene were simultaneously transfected into COS-1 cells. The reporter plasmid contains chloramphenicol acetyltransferase (CAT) gene downstream of an enhancer/promoter sequence derived from the human T-cell leukemia virus type-1 (HTLV-I) long-terminal repeat (LTR). The substrate expression plasmid was a triple chimera; HCV nonstructural protein 2 (NS2) and the Tax1 protein of HTLV-I sandwiched the substrate polypeptide, which was inserted upstream of Tax1. This method assumes that since the HCV NS2 appears to be located in the lipid bilayer of endoplasmic reticulum (ER) membranes, the Tax1 of the chimeric substrate was trapped on the surface of the ER in the absence of HCV proteinase activity. After release from the chimera by HCV proteinase-dependent cleavage, Tax1 could transactivate the expression of the CAT gene through the enhancer sequence of HTLV-I LTR. This system should enable us to simply and safely screen the potential antiviral activity of proteinase inhibitors in vivo, although this system may be limited to proteinase inhibitors that are permeable to the plasma membrane.
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PMID:A novel method for analysis of viral proteinase activity encoded by hepatitis C virus in cultured cells. 777 61

A replication-defective feline leukemia virus molecular clone, 61B, has been shown to cause immunodeficiency in cats and cytopathicity in T cells after a long latency period when coinfected with a minimally pathogenic helper virus (J. Overbaugh, E. A. Hoover, J. I. Mullins, D. P. W. Burns, L. Rudensey, S. L. Quackenbush, V. Stallard, and P. R. Donahue, Virology 188:558-569, 1992). The long-latency phenotype of 61B has been mapped to four mutations in the extracellular domain of the envelope transmembrane protein, and we report here that these mutations cause a defect in envelope protein processing. Immunoprecipitation analyses demonstrated that the 61B gp85 envelope precursor was produced but that further processing to generate the surface protein (SU/gp70) and the transmembrane protein (TM/p15E) did not occur. The 61B precursor was not expressed on the cell surface and appeared to be retained in the endoplasmic reticulum or Golgi apparatus. Two of the four 61B-specific amino acid changes are located within a putative cysteine loop in a region of TM that is conserved among retroviruses. Introduction of these two amino acid changes into a replication-competent highly cytopathic virus resulted in the production of noninfectious virus that exhibited an envelope-protein-processing defect. This analysis suggests that mutations in a conserved region within a putative cysteine loop affect retroviral envelope protein maturation and viral infectivity.
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PMID:Mutations within a putative cysteine loop of the transmembrane protein of an attenuated immunodeficiency-inducing feline leukemia virus variant inhibit envelope protein processing. 788 59

With the recent advances in molecular technology, diagnostic procedures of the diseases at a DNA level have been introduced in hematological fields. The diagnostic methods used are Southern blotting to detect gene rearrangements, Northern blotting to find gene expressions, RT-PCR (reverse transcriptase-polymerase chain reaction) to identify transcribed fusion messages, and PCR-SSCR (single strand conformation polymorphism) to detect mutated genes. Rearrangements within major Bcr (breakpoint cluster region) were observed in almost all cases in chronic myelogenous leukemia, and breakpoint were found within minor Bcr in Philadelphia-positive leukemia. The rearrangements within the second intron of the retinoic acid receptor-alpha and sixth intron (bcr 1), third intron (bcr 3) and sixth exon (bcr 2) of the PML gene were detected in all cases with acute promyelocytic leukemia. In malignant lymphoma, the rearrangements of immunoglobulin and T-cell receptor genes, and new genes such as Bcl-1, Bcl-2, Bcl-5, Tal-1, and Tal-2 were also reported and rearrangements of the Bcl-5 gene were found in this study using Bcl-5 specific probe which we have cloned. Point mutations and deletions of the genes involved in the coagulation and fibrinolysis system have been reported. One base insertion resulting in elongation of carboxy terminal region and one amino acid deletion in alpha 2-plasmin inhibitor gene were found in two cases of its deficiency. Further study revealed that mutated proteins were retained in the endoplasmic reticulum in the cells. With the development of the PCR method, identification of gene mutation is gradually carried out as a routine work.
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PMID:[Molecular study of hematological diseases]. 791 42

Erythropoietin (Epo) autocrine stimulation has been implicated in erythroblastic leukemia. To examine whether this stimulation could occur intracellularly, we developed Epo autocrine models of stimulation in the human pluripotent UT-7 cell line. Retroviral expression of Epo totally abolished the growth factor requirement of UT-7 cells. Autonomous proliferation was not cell density-dependent and occurred at a unicellular level, showing a genuine autocrine mode of stimulation. Total blockage of Epo secretion induced by the endoplasmic reticulum-retention amino acids Lys-Asp-Glu-Leu (KDEL) signals in 11 lines prevented autonomous proliferation, whereas a leaky retention system, observed in 3 other lines, resulted in limited autocrine stimulation without true long-term autonomous proliferation. Production of Epo, in contrast to KDEL-modified Epo, induced reductions in Epo binding, Epo receptor (EpoR) mRNA, and phosphorylation levels similar to those induced by the addition of exogenous Epo to the parental cell line. In addition, autonomous growth and survival were inhibited by the addition of Epo-neutralizing antibodies, affording evidence that autocrine stimulation through EpoR activation takes place on the cell surface. Finally, phenotypic analysis of the virus-infected clones indicated that Epo production did not change the differentiative capacities of UT-7 cells. All these data show that Epo autocrine stimulation is dependent on Epo secretion and takes place on the cell surface. From all analyzed parameters, the effects of Epo autocrine stimulation and those of exogenously added Epo appear to be identical.
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PMID:Autocrine stimulation by erythropoietin (Epo) requires Epo secretion. 791 79

Processing of the env polyprotein of a noninfectious feline leukemia virus (FeLV) recombinant, named r6gp, was examined in human-transfected cells. The r6gp provirus was previously generated in the frame of FeLV, subgroup B, GA clone with substitution of all but 40 C-terminal amino acid sequences of the surface glycoprotein (SU) from an endogenous FeLV provirus element (CFE-6). Although r6gp produced a normal size (85 kDa) env glycoprotein precursor, the product, unlike the precursor of the parental virus, was neither additionally glycosylated nor further processed into mature env proteins. Biochemical observations were consistent with the idea that the chimeric env polyprotein was trapped in the endoplasmic reticulum (ER) and were directly supported by immunofluorescence microscopy analyses. Interestingly, the residence of the chimeric protein in the ER specifically interfered with FeLV, subgroup C (Sarma) virus infection but not the parental FeLV-B virus infection. Since FeLV-C provirus sequences could be readily detected in the infected cells, it appeared that r6gp env expression did not block entry of the challenge virus. While FeLV-B and CFE-6 env genes share an extensive overall sequence homology, a variable region (region VI) of CFE-6 near the C-terminus of SU, which was retained in the r6gp construct, exhibits a considerably higher degree of homology to FeLV-C than FeLV-B. Thus, we propose that region VI is involved in conferring specificity for the env polyprotein oligomerization in the ER, and that co-oligomerization of the trapped r6gp env with FeLV-C is the reason for specific interference with FeLV-C infection. The results also demonstrate for the first time a functional abnormality of a recombinant FeLV env gene which is structurally similar to those commonly detected in FeLV-induced feline lymphosarcomas.
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PMID:Abnormal processing of a recombinant feline leukemia virus envelope polyprotein and its interference with subgroup C virus infection. 800 44

Interaction between the previously obtained dominant negative mutant, referred to as fcr (T. Matano, T. Odawara, M. Ohshima, H. Yoshikura, and A. Iwamoto, J. Virol. 67:2026-2033, 1993), and the wild-type envelope proteins (Env) of Friend murine leukemia virus was examined. The wild-type Env was bound to the fcr mutant Env and trapped in the endoplasmic reticulum. The virus receptor was not involved in this interaction.
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PMID:Interaction between the dominant negative mutant and the wild-type envelope proteins of Friend murine leukemia virus. 805 86


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