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H Amanuma

Publications and source records attributed to H Amanuma.

At least 19 recordsLinked to original sources
PubMed1995

Both the changes of six amino acids and the C-terminal truncation caused by a one-base insertion in the defective env gene of Friend spleen focus-forming virus significantly affect the pathogenic activity of the encoded leukemogenic membrane glycoprotein (gp55).

Friend spleen focus-forming virus (F-SFFV) causes acute erythroleukemia in mice and encodes in its defective env gene an Env-like membrane glycoprotein (gp55). The F-SFFV env gene has three characteristic structures compared with that of ecotropic murine leukemia viruses (MuLVs): substitution by the polytropic MuLV env sequence, a 585-bp deletion, and a 1-bp insertion. All of these characteristic structures are essential for the leukemogenic potential of gp55 of polycythemia-inducing isolates of F-SFFV (F-SFFVp). The 1-bp insertion causes changes of six amino acids and truncation by 34 amino acids at the C terminus. In this study, we constructed 12 mutant F-SFFV genomes starting from the wild-type F-SFFVp and examined the effect of the C-terminal truncation and the six altered amino acids on the pathogenic activity of gp55. The results indicated that at least 18 to 24 amino acids must be deleted from the C terminus for the env product to be pathogenically active. We also found that the six altered amino acids contributed significantly to the pathogenic activity of gp55. Analyses of the cellular processing of these mutant gp55s supported a correlation between the pathogenic activity of gp55 and its efficiency in overall cellular processing.

3T3 Cells↗
PubMed1992

Tumor-associated M(r) 34,000 and M(r) 32,000 membrane glycoproteins that are serine phosphorylated specifically in bovine leukemia virus-induced lymphosarcoma cells.

Tumor-associated antigens that are expressed in tumor cells of cattle with enzootic bovine leukosis (EBL) were analyzed previously by use of 13 monoclonal antibodies. We biochemically identified one of the tumor-associated antigens, which is recognized by the c143 monoclonal antibody, as two glycoproteins, each having an apparent molecular weight of 32,000 or 34,000. These glycoproteins were found in the plasma membrane of peripheral blood lymphocytes of both bovine leukemia virus (BLV)-free normal and BLV-infected cattle. With the progression of EBL, the proportion and the absolute number of cells positive for the tumor-associated antigen increased. Moreover, the level of the M(r) 34,000 component, which was susceptible to cell-surface labeling, increased over the level of the M(r) 32,000 component. Partial proteolytic peptide mapping with V8 protease and deglycosylation analysis revealed that the two glycoproteins most likely have an identical M(r) 30,000 polypeptide portion but have different N-linked oligosaccharide portions. Both glycoproteins were found to be phosphorylated at serine residue(s) in EBL-derived B-lymphoid cell lines and in tumor cells and peripheral blood lymphocytes from cattle with EBL, but not in peripheral blood lymphocytes from BLV-free normal cattle and BLV-infected cattle without any evidence of tumor, suggesting that the phosphorylation of these glycoproteins is related to the transformed state of the BLV-infected B-lymphoid cells.

Animals↗
PubMed1992

A POU-domain gene of zebrafish, ZFPOU1, specifically expressed in the developing neural tissues.

We have isolated a POU domain-containing cDNA (ZFPOU1) from a cDNA library of zebrafish (Brachydanio rerio). The ZFPOU1 cDNA contained an open reading frame encoding a 425 amino acid peptide. The conserved POU domain was located near the carboxy terminus. The deduced amino acid sequence of the reading frame was most similar to that of the mouse class III POU-domain gene, Brain-1. Northern blot analysis revealed that the ZFPOU1 transcripts first appeared at the early neurula stage of embryogenesis and transiently increased thereafter. A significant level of expression, however, was not found in adult tissues except in the brain. In situ hybridization analysis demonstrated that the ZFPOU1 transcripts were localized in the neural tissues of embryos, but not in mesodermal, endodermal or ectodermal tissues. In adult zebrafish, the ZFPOU1 transcripts were detected in the restricted regions of the brain. Spatial and temporal expression patterns suggest that ZFPOU1 has distinct roles in the early neural development of zebrafish.

Amino Acid Sequence↗
PubMed1992

Functionally essential cytoplasmic domain of the erythropoietin receptor.

The cytoplasmic domains of the erythropoietin receptor essential for signal transduction were identified by assessing a series of truncated and deletional mutant receptors. A 91-amino acid region proximal to the transmembrane domain was required for growth signaling. In this region, residues between 353Pro and 362His and between 278Gln and 308Leu appeared to constitute the essential cytoplasmic domains. These two domains contain the conserved amino acids common in the cytokine receptor superfamily, which indicates that these domains in the cytoplasmic regions of the erythropoietin receptor may be important for interaction with common signal transducers or protein tyrosine kinases.

Amino Acid Sequence↗
PubMed1992

Tryptophan residue of Trp-Ser-X-Trp-Ser motif in extracellular domains of erythropoietin receptor is essential for signal transduction.

The Trp-Ser-X-Trp-Ser motif commonly exists just outside the transmembrane domains of all cytokine receptors so far isolated. The role of this conserved motif in erythropoietin receptor was examined by assessing a series of mutant receptors on erythropoietin-induced signal transduction. Replacement of one of the two conserved Trp residues in the motif to Gly was found to completely abolish the binding of erythropoietin to the receptor and also to lose the ability to transduce the factor-dependent growth signal. While the mutants with one Ser residue converted to Gly or Ala retained full biological activities, the replacement of both conserved Ser residues diminished the functions of the receptor. Furthermore, the receptors lacking a part or all of the Trp-Ser-X-Trp-Ser motif did not respond to erythropoietin. The Trp-Ser-X-Trp-Ser motif, especially Trp residue, located in extracellular domains of the erythropoietin receptor thus appears to play a critical role in receptor-mediated signal transduction.

Amino Acid Sequence↗
PubMed1992

Expression of c-kit, a proto-oncogene of the murine W locus, in cerebella of normal and neurological mutant mice: immunohistochemical and in situ hybridization analysis.

The c-kit proto-oncogene encodes a receptor tyrosine kinase and is allelic with the murine white-spoting (W) locus. Although no apparent defects in the brain have been reported in W mutant mice, brain tissue, especially cerebellum, shows a high level of c-kit transcription. In the present study, sites of c-kit expression in the cerebellum were exained by immunohistochemical and in situ hybridization techniques. Immunohistochemistry with a monoclonal antibody against c-Kit protein revealed that the c-Kit protein was localized close to the Purkinje cell soma in the region facing the granular cell layer. Similar distribution of the c-Kit protein was observed in cerebella of mutant mice in which the Purkinje cell (pcd) or the granular cell layer (weaver) is missing. These data suggest that the c-Kit protein is produced not by the Purkinje cell nor by the granular cell but by the cells present in the molecular layer and that the protein is then transported to the region around the Purkinje cell soma. This interpretation was supported by in situ hybridization analysis: cells containing the c-kit transcripts were found only in the molecular layer, while the granular and Purkinje cells were negative.

Alleles↗
PubMed1992

Cross-reactivity between a monoclonal antibody that recognizes a tumor-associated antigen on bovine lymphosarcoma cells and blood lymphocytes from various mammalian species.

Tumor-associated antigens that are expressed in lymphosarcoma B cells of cattle with enzootic bovine leukosis had been analyzed in terms of their reactivity with 13 monoclonal antibodies (MAB). By use of flow cytometry and radioimmunoprecipitation, 1 of the MAB (c143) that recognized a tumor-associated antigen cross-reacted with blood lymphocytes (BL) from various mammalian species. By use of flow cytometry, the c143 MAB reacted with 10 to 49% of BL derived from human beings, mice, dogs, horses, pigs, llamas, sheep, goats, and cattle. Titer of the c143 MAB with BL from horses, pigs, human beings, and llamas ranged between 1:6.0 x 10(4) and 1:5.3 x 10(5); titer associated with BL of goats and sheep was 1:1.6 x 10(6); and that associated with BL of cattle was 1:4.3 x 10(7). The c143 MAB specifically immunoprecipitated 3 homologous proteins from cell extracts of caprine, ovine, and bovine BL (32-, 34-, and 36- to 37-kDa bovine proteins; 31-, 32-, and 36- to 37-kDa caprine proteins; and 31.5-, 33-, and 36- to 37-kDa ovine proteins), but none was immunoprecipitated from human, murine, canine, porcine, and llama BL. These results indicate that the avidity of the c143 MAB in binding to BL from ruminants (eg, goats, sheep, and cattle) is higher than that to BL from human beings, mice, dogs, horses, pigs, and llamas. In sheep, the c143 MAB could immunoprecipitate the aforementioned proteins from BL of the Suffolk breed, but not BL from the Corriedale breed, whereas the c143 MAB immunoprecipitated apparently identical proteins from BL of 4 breeds of cattle.

Animals↗
PubMed1991

Growth signal erythropoietin activates the same tyrosine kinases as interleukin 3, but activates only one tyrosine kinase as differentiation signal.

By Western blotting with anti-phosphotyrosine-specific antibody, we demonstrated that both erythropoietin (Epo) and interleukin 3 (IL3) induce rapid and transient tyrosine phosphorylation of a common set of proteins of 45, 55, 69, 87, 90, 95 and 160 KDa as a growth signal in Epo- and IL3-dependent FD-M6 cells. In contrast, only two proteins of 87 and 90 KDa were transiently phosphorylated in Epo-induced erythroid differentiation of SKT6 cells. Furthermore, no tyrosine phosphorylation was observed in dimethyl sulfoxide-induced differentiation of SKT6 cells. Taken together with other observations, these results indicate that Epo, IL3 and GM-CSF activate the same tyrosine protein kinases as growth signal and that Epo-induced differentiation signal uses only a part of the tyrosine kinase pathway.

Animals↗
PubMed1991

Conversion of Friend mink cell focus-forming virus to Friend spleen focus-forming virus by modification of the 3' half of the env gene.

The 3' half of the env gene of the dualtropic Friend mink cell focus-forming virus was modified by replacing the restriction enzyme fragment of the genome DNA with the corresponding fragment of the acutely leukemogenic, polycythemia-inducing strain of Friend spleen focus-forming virus (F-SFFVP) genome DNA. Replacement with the fragment of F-SFFVP env containing the 585-bp deletion, the 6-bp duplication, and the single-base insertion converted the resulting chimeric genome so that the mutant had a pathogenic activity like that of F-SFFVP. Replacement with the fragment containing only the 585-bp deletion did not result in a pathogenic virus. However, when this virus pseudotyped by Friend murine leukemia virus was passaged in newborn DBA/2 mice, we could recover weakly pathogenic viruses with a high frequency. Molecular analysis of the genome of the recovered virus revealed the presence of a single-base insertion in the same T5 stretch where the wild-type F-SFFV env has the single-base insertion. These results provided evidence that the unique genomic structures present in the 3' half of F-SFFV env are the sole determinants that distinguish the pathogenicity of F-SFFV from that of Friend mink cell focus-forming virus. The importance of the dualtropic env-specific sequence present in the 5' half of F-SFFV env for the pathogenic activity was evaluated by constructing a mutant F-SFFV genome in which this sequence was replaced by the ecotropic env sequence of Friend murine leukemia virus and by examining its pathogenicity. The results indicated that the dualtropic env-specific sequence was essential to pathogenic activity.

Animals↗
PubMed1990

Oligomerization of Friend spleen focus-forming virus (SFFV) env glycoproteins.

The glycoprotein gp55 and its processed form gp65, which are encoded by the env gene of Friend spleen focus-forming virus (SFFV), have been implicated in the initiation of the murine acute erythroleukemia induced by Friend virus (FV). Analyses of these glycoproteins by chemical crosslinking and nonreducing/reducing two-dimensional electrophoresis showed that both gp55 and gp65 exist as monomer and disulfide-bonded dimer and trimer. These oligomers could be detected in various FV-infected erythroleukemia cell lines, as well as in the spleen cells of FV-induced erythroleukemic mice, suggesting that oligomerization is an intrinsic feature of SFFV env glycoproteins.

Animals↗
PubMed1990

A deletion in the Friend spleen focus-forming virus env gene is necessary for its product (gp55) to be leukemogenic.

To determine the biological significance of the 585-base-pair deletion in the env gene of Friend spleen focus-forming virus (SFFV) encoding a leukemogenic glycoprotein (gp55), we examined the pathogenicity of a constructed mutant SFFV (SFFVDF). In the SFFVDF genome, the env deletion was filled in with the corresponding env sequence of Friend mink cell focus-forming virus, whereas the 6-base-pair duplication and the single base insertion near the 3' terminus of SFFV env remained intact. SFFVDF was nonpathogenic in adult mice. During passage of SFFVDF through newborn mice, we recovered various pathogenic variant SFFVs. Molecular analyses of variant SFFV genome DNAs revealed the presence of a distinct deletion in each env gene, which was similar but not identical to that in the wild-type SFFV env. Starting with the SFFVDF genome DNA, other mutant SFFV genome DNAs were constructed in which the sequence coding for the gp70/p15E proteolytic cleavage site present in the SFFVDF genome was modified by oligonucleotide-directed site-specific mutagenesis to prevent the cleavage. These mutant SFFVs were also nonpathogenic. These results indicate that for the pathogenic activity of gp55, a certain env deletion is necessary which causes production of a gp70-p15E fusion protein with an absence of at least the N-terminal one-third of the p15E-coding region.

Animals↗
PubMed1989

Integration and expression of murine retrovirus-related sequences in schistosomes.

Antibodies against the retrovirus envelope glycoprotein (gp70) of mouse xenotropic retrovirus, BALB virus 2 (Bv2) reacted with the adult worms of Schistosoma japonicum and S. mansoni. This reaction was completely inhibited after adsorption of the antibodies with virions of retrovirus. The reactive schistosome antigen was located in the subtegumental layer of the adult male fluke and in the vitelline gland of the adult female of S. japonicum and S. mansoni. Proteins extracted from both parasites were examined by immunoblot analysis. Anti-Bv2 gp70 antiserum reacted with those proteins from both schistosomes and the band patterns were different among sexes and species. Southern hybridization of the DNA extracted from adults of S. japonicum and S. mansoni demonstrated the presence of sequences homologous to the env gene of mouse ecotropic and xenotropic retroviruses. DNA sequences homologous to the gag and pol regions of the ecotropic murine leukaemia virus were also detected in the DNAs of schistosomes.

Animals↗
PubMed1989

Requirement of the single base insertion at the 3' end of the env-related gene of Friend spleen focus-forming virus for pathogenic activity and its effect on localization of the glycoprotein product (gp55).

In order to obtain evidence for the essential role of the single base insertion occurring at the 3' end of the env-related gene of Friend spleen focus-forming virus (SFFV) encoding the leukemogenic glycoprotein (gp55) a mutant SFFV genome was constructed in which the segment of the gp55 gene of the polycythemia-inducing strain of SFFV containing the single base insertion and the 6-base-pair duplication was replaced by the corresponding sequence of the Friend murine leukemia virus env gene. The mutant SFFV-Friend murine leukemia virus complex did not induce symptoms of the erythroproliferative disease in adult DBA/2 mice. During passage through newborn DBA/2 mice, the mutant virus complex invariably gave rise to weakly pathogenic variant SFFVs. All of the variant SFFVs induced in adult DBA/2 mice a transient mild splenomegaly associated with normal or slightly low hematocrit value, and they produced gp55 with a molecular weight similar to that of gp55 of the wild-type SFFV. For the two isolates of variant SFFV, the 3' portion of the viral DNA intermediate containing the 3' portion of the gp55 gene was molecularly cloned. Nucleotide sequences of these biologically active cloned DNAs were determined and showed that the variant SFFV genomes arose from the mutant SFFV genome by regaining the single base insertion, indicating that the single base insertion is essential for the biological activity of gp55. Evidence is presented indicating that the single base insertion which causes a loss of the cytoplasmic domain of the env-related protein is not related to the localization of the further-glycosylated form of gp55 in the plasma membrane but is involved with the release of gp55 from cells.

Amino Acid Sequence↗
PubMed1988

Characterization of erythropoietin receptor on erythropoietin-unresponsive mouse erythroleukemia cells.

A membrane receptor for erythropoietin was identified in various erythropoietin-unresponsive mouse erythroleukemia cells. Scatchard analyses of the binding of human 125I-labeled erythropoietin to T3C1-2-0, K-1, GM86 and 707 cells showed the presence of a single class of binding sites with apparent Kd values of 0.27-0.78 nM, which are slightly higher than those of erythropoietin-responsive cells. The number of binding sites varied from 110 to 930 per cell. Crosslinking of 125I-erythropoietin to its binding sites with disuccinimidyl suberate revealed the existence of a single binding protein with molecular mass of 63 kDa. No binding sites with higher molecular mass, as observed in erythropoietin-responsive cells, were detected, nor was any specific binding observed to the non-erythroid hematopoietic cell or to the human erythroleukemia cells examined.

Animals↗
PubMed1988

Identification of putative endogenous proviral templates for progenitor mink cell focus-forming (MCF) MuLV-related RNAs.

Murine leukemia virus (MuLV)-related RNAs exhibiting different env deletions are believed to participate in the generation of leukemogenic mink cell focus-forming (MCF) viruses. We have cloned an endogenous MuLV provirus from AKR/J mouse DNA, designated as A-2, which may serve as template for the env-deleted E2 MuLV RNA, expressed in GIX+ mice (D.E. Levy et al., J. Virol. 56, 691-700 (1985]. We have also isolated an endogenous MCF-related DNA, A-1, which shared close sequence homology with the 7.2-kb RNA expressed in AKR mice (F. Laigret et al., J. Virol. 62, 376-386 (1988] and sustained an identical env deletion. The data indicate that putative precursor MCF-related RNAs are transcribed from a heterogenous family of env-deleted endogenous MuLV DNAs.

Base Sequence↗
PubMed1988

Down-regulation of c-myb gene expression is a prerequisite for erythropoietin-induced erythroid differentiation.

The role of nuclear protooncogenes during erythroid cell differentiation was examined by transfecting exogenous c-fos and c-myb genes into mouse erythroleukemia cells, which can be induced to differentiate either with erythropoietin (Epo) or dimethyl sulfoxide. Expression of exogenous c-myb or c-fos oncogene completely inhibited Epo-induced erythroid differentiation but only partially inhibited dimethyl sulfoxide-induced differentiation. Normally Epo-induced differentiation leads to a drastic decline of c-myb mRNA levels and an increase of c-myc transcripts in the early stage of differentiation. Cells expressing exogenous c-fos gene, however, maintained high levels of c-myb mRNA after Epo treatment. This high level of c-myb transcripts was found to be due to block of transcription shutoff (or transcriptional activation) rather than to mRNA stabilization. It is concluded that the down-regulation of endogenous c-myb gene expression is a prerequisite for commitment of Epo-induced erythroid differentiation and that expression of c-myb gene may be indirectly regulated by c-fos gene product. We also concluded that early down-regulation of c-myc gene expression is not essential for erythroid differentiation and that gene regulation of chemically induced erythroid differentiation may differ from that of Epo-induced differentiation.

Animals↗
PubMed1987

Specific binding of erythropoietin to its receptor on responsive mouse erythroleukemia cells.

Erythropoietin (Epo) is a glycoprotein factor that specifically regulates the proliferation and differentiation of erythroid progenitor cells. Here we describe the isolation of Epo-responsive mouse erythroleukemia cell line SKT6, the characterization of the specific binding of biologically active 125I-labeled human Epo (125I-Epo) to its membrane receptor, and, finally, report information concerning the molecular structure of the receptor. About 75% of erythroid colony-forming precursor cell-like colonies derived from SKT6 cells were hemoglobin-positive after 3- to 4-day exposure to Epo in methylcellulose culture. Radioiodinated Epo bound specifically to SKT6 cells, and Scatchard analysis of the data showed a high affinity for 125I-Epo (Kd = 0.15 nM) but displayed only a small number of specific receptors (approximately equal to 470 per cell). Membrane components that specifically interact with 125I-Epo were identified by covalent crosslinking with disuccinimidyl suberate, and three receptor species with apparent Mr 63,000, 94,000, and 119,000 were found in membrane from SKT6 cells, suggesting the complex structure of the receptor molecules. Specific bindings were also detected in all of the Epo-unresponsive Friend erythroleukemia cells examined, and cross-linking study revealed the presence of only the 63,000 species as a binding site.

Animals↗