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Biomedical subjects

N Taniguchi

Publications and source records attributed to N Taniguchi.

At least 109 records · Page 6Linked to original sources
PubMed1999

Implication of N-acetylglucosaminyltransferases III and V in cancer: gene regulation and signaling mechanism.

N-acetylglucosaminyltransferases III (GnT-III) and V (GnT-V) play a pivotal role in the processing of N-linked glycoproteins, and are highly involved in cancer progression and metastasis. Expression of GnT-III and GnT-V in the liver is enhanced during hepatocarcinogenesis, although they are not expressed in the normal liver. Gene expression of GnT-V is regulated by a transcriptional factor, ets-1, which is involved in angiogenesis and invasion of tumor cells. When the formation of the product of GnT-V, GlcNAc-beta1-6 branches, is inhibited by overexpression of GnT-III, lung metastasis of melanoma cells is suppressed. Modification of glycoprotein receptors such as the receptors for epidermal growth factor and nerve growth factor by GnT-III sense transfection changes an intracellular signaling pathway, which may lead to a variety of biological alterations in tumor cells. In this review, we focus on cancer progression and metastasis in relation to GnT-III and GnT-V.

Animals↗
PubMed1999

Upregulation of endogenous heparin-binding EGF-like growth factor and its role as a survival factor in skeletal myotubes.

To investigate the role of heparin-binding EGF-like growth factor (HB-EGF) in skeletal muscle, we studied its function in skeletal myotubes in vitro using mouse C2C12 cells. Expression levels of membrane-anchored HB-EGF (proHB-EGF) protein were increased specifically during their differentiation among epidermal growth factor receptor (EGFR) ligands. Production levels of EGFR on the cell surface were constant. Tyrosine phosphorylation of EGFR, however, was constitutively increased during differentiation. Quenching of endogenous HB-EGF significantly rendered myotubes sensitive to apoptotic cell death induced by hypoxic stress, suggesting that proHB-EGF in the skeletal muscle is specifically upregulated to function as a survival factor.

Animals↗
PubMed1999

Glutathione peroxidase-like activity of caeruloplasmin as an important lung antioxidant.

The copper-containing plasma protein caeruloplasmin (Cp) has been shown to possess several oxidase activities, but with the exception of its ferrous ion oxidising (ferroxidase) activity which so far appear to be of minor biological relevance. Recently, Kim and colleagues (Kim et al. (1998) FEBS Lett. 431, pp. 473-475) observed that Cp can catalytically remove hydrogen peroxide in the presence of thiols. Here, we show that Cp can remove both hydrogen peroxide and lipid hydroperoxides at physiologically relevant concentrations of reduced glutathione known to be present in lung and lung lining fluid. The glutathione peroxidase-like activity of Cp together with its ferroxidase activity would completely remove the primary reactants required for both Fenton chemistry and lipid peroxidation.

Antioxidants↗
PubMed1999

Glycation of apolipoprotein E impairs its binding to heparin: identification of the major glycation site.

The increased glycation of plasma apolipoproteins represents a possible major factor for lipid disturbances and accelerated atherogenesis in diabetic patients. The glycation of apolipoprotein E (apoE), a key lipid-transport protein in plasma, was studied both in vivo and in vitro. ApoE was shown to be glycated in plasma very low density lipoproteins of both normal subjects and hyperglycemic, diabetic patients. However, diabetic patients with hyperglycemia showed a 2-3-fold increased level of apoE glycation. ApoE from diabetic plasma showed decreased binding to heparin compared to normal plasma apoE. The rate of Amadori product formation in apoE in vitro was similar to that for albumin and apolipoproteins A-I and A-II. The glycation of apoE in vitro significantly decreased its ability to bind to heparin, a critical process in the sequestration and uptake of apoE-containing lipoproteins by cells. Diethylenetriaminepentaacetic acid, a transition metal chelator, had no effect on the loss of apoE heparin-binding activity, suggesting that glycation rather than glycoxidation is responsible for this effect. In contrast, glycation had no effect on the interaction of apoE with amyloid beta-peptide. ApoE glycation was demonstrated to be isoform-specific. ApoE(2) showed a higher glycation rate and the following order was observed: apoE(2)>apoE(4)>apoE(3). The major glycated site of apoE was found to be Lys-75. These findings suggest that apoE is glycated in an isoform-specific manner and that the glycation, in turn, significantly decreases apoE heparin-binding activity. We propose that apoE glycation impairs lipoprotein-cell interactions, which are mediated via heparan sulfate proteoglycans and may result in the enhancement of lipid abnormalities in hyperglycemic, diabetic patients.

Aged↗
PubMed1999

Regulation of the GnT-V promoter by transcription factor Ets-1 in various cancer cell lines.

Although the precise role of oligosaccharides in metastasis is presently unknown, numerous studies suggest that the beta1-6 branching structure of N-linked oligosaccharides plays a role in tumor metastasis. N-Acetylglucosaminyltransferase V (GnT-V), which catalyzes the formation of the beta1-6 branch, therefore appears to play a crucial role in tumor metastasis. Recently, we demonstrated that the expression of the GnT-V gene is regulated by a transcriptional factor, Ets-1 (Kang, R., Saito, H., Ihara, Y., Miyoshi, E., Koyama, N., Sheng, Y., and Taniguchi, N. (1996) J. Biol. Chem. 271, 26706-26712). In this study, we report an investigation of the general requirement for Ets-1 in the expression of GnT-V in cancer cell lines. In 16 cancer cell lines, the levels of GnT-V mRNA were closely correlated with ets-1 expression (r = 0.97; p < 0.0001). An increase in ets-1 levels by transfection of its cDNA led to an enhancement in GnT-V expression in cells that normally expressed low levels of ets-1. In contrast, the transfection of dominant negative ets-1 into cells that express high levels of ets-1 resulted in a decrease in GnT-V expression. Although Ets-1 cooperates with c-Jun in certain gene expressions, this was not the case in the regulation of the GnT-V gene. These results suggest that Ets-1 plays a significant role in regulating the expression of GnT-V in a variety of cancers and might be involved in the potential for malignancy via the action of GnT-V.

Base Sequence↗
PubMed1999

Effects of exogenous human heparin-binding epidermal growth factor-like growth factor on DNA synthesis of hepatocytes in normal mouse liver.

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) has been reported to stimulate DNA synthesis of the hepatocytes in culture and highly express in regenerating rat liver after partial hepatectomy. We examined mitogenic effects and activation of transcription factors caused by exogenous human HB-EGF (hHB-EGF) in mouse liver. The mean labeling index in hepatocytes of hHB-EGF-injected mice was 2.6%, a significant increase over that in saline-injected controls (under 0.01%). By exogenous hHB-EGF injection, activation of transcription factors such as nuclear factor (NF)-kappaB and activator factor (AP)-1 was observed in the liver. By Northern blot analysis, hepatocyte growth factor (HGF) gene expression in the liver was found to be induced in the hHB-EGF-injected mice. In conclusion, intravenously injected hHB-EGF showed a limited but definite effect on the DNA synthesis of hepatocytes in the mice liver. HB-EGF may serve as a hepatotrophic factor in vivo.

Animals↗
PubMed1999

Functional expression of rat thioredoxin reductase: selenocysteine insertion sequence element is essential for the active enzyme.

Mammalian thioredoxin reductase (TR) is a flavoprotein catalysing reduction of oxidized thioredoxin in an NADPH-dependent manner, and contains a selenocysteine (Sec) residue near the C-terminus. We observed that TR activity was decreased in A549 cells by the lowering of the fetal bovine serum content in the culture medium and was recovered by the addition of selenium. To study the role of Sec in TR activity, we have isolated a full-length clone of the rat TR cDNA (3.3 kb) and have expressed it in COS-1 cells in a transient-expression system. TR activities in COS-1 cells expressing rat TR were increased in accordance with supplemented sodium selenite concentrations, whereas levels of TR protein, examined by Western blotting, were not affected by sodium selenite concentrations. We introduced various deletions into the 3'-untranslated region of the TR cDNA to localize and examine the role of a Sec insertion-sequence (SECIS) element in the functional expression of TR. TR activities were observed only in COS-1 cells transfected with the TR cDNAs containing the putative SECIS element located between 1856 and 1915 bp in the correct orientation. We also carried out radiolabelling of proteins by incubation of the cDNA-transfected cells with sodium [75Se]selenite. 75Se was incorporated into the expressed TR protein of the cells transfected with the SECIS element-containing cDNAs, but not into those without the SECIS element or with an inverted SECIS element. These data clearly showed a requirement of selenium for the formation of functional TR protein.

3' Untranslated Regions↗
PubMed1999

The requirement of both intracellular reactive oxygen species and intracellular calcium elevation for the induction of heparin-binding EGF-like growth factor in vascular endothelial cells and smooth muscle cells.

Heparin-binding EGF-like growth factor (HB-EGF), which is a potent mitogen for vascular smooth muscle cells (SMC) and fibroblasts, has been reported to be strongly implicated in atherosclerosis and wound healing. HB-EGF mRNA is known to be induced by thrombin, angiotensin-II, basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF), and HB-EGF itself in SMC. In vascular endothelial cells (EC), its mRNA is induced by tumor necrosis factor-alpha and interleukin-1beta. Only phorbol 12-myristate 13-acetate is a common inducer for HB-EGF mRNA. The present study shows that calcium ionophore A23187 also induced HB-EGF mRNA in both SMC and in EC and that both intracellular reactive oxygen species (ROS) and an increase in calcium levels were essential for the induction of this growth factor mRNA. While HB-EGF caused an increase in both intracellular ROS and calcium in SMC, it increased only calcium, but not the intracellular ROS in EC. When the intracellular ROS was elevated by treatment with hydrogen peroxide (H2O2) or by depletion of glutathione by buthionine sulfoxamine, both HB-EGF and thrombin were observed to upregulate HB-EGF mRNA in EC. These data suggest that H2O2, produced by activated leukocytes in inflammatory lesions, upregulates HB-EGF mRNA by cooperating with thrombin, angiotensin-II, and the above growth factors. Since activated macrophages under the EC are thought to elevate the ROS in neighboring EC, this mechanism might play a major role in the progression of atherosclerosis and for wound healing.

Buthionine Sulfoximine↗
PubMed1999

Overexpression of alpha1-6 fucosyltransferase in hepatoma cells suppresses intrahepatic metastasis after splenic injection in athymic mice.

Changes in oligosaccharide structures alter the biological functions of cancer cells. Alpha1-6 fucosyltransferase (alpha1-6FucT) catalyzes the transfer of fucose to the innermost GlcNAc in N-glycans. Although alpha1-6FucT is barely detected in normal liver, it is enhanced during rat hepatocarcinogenesis and in human hepatoma. To understand the biological meaning of the alpha1-6FucT in hepatoma, especially in terms of metastasis, we established human hepatoma cell lines, which express high levels of alpha1-6FucT by transfection of the alpha1-6FucT gene and investigated intrahepatic metastasis after splenic injection to athymic mice. Tumor formation in the liver was dramatically suppressed in the alpha1-6FucT transfectants (1 of 9 and 1 of 10 in alpha1-6FucT transfectants versus 6 of 9 and 6 of 9 in controls). Although there were no differences in terms of cell invasiveness to a Matrigel or in terms of cytotoxicity to interleukin 2-treated lymphocytes between alpha1-6FucT transfectants and control cells, cell adhesion to mice hepatocytes and nonparenchymal liver cells in culture was significantly inhibited in alpha1-6FucT transfectants, compared to the controls. Attachment of alpha1-6FucT transfectants to a fibronectin-coated dish was decreased compared to controls because alpha5beta1 integrin was more strongly alpha1-6 fucosylated in the alpha1-6FucT transfectants. Two-dimensional electrophoresis followed by lectin blot showed that certain glycoproteins (Mr 50,000-150,000, pI 4.8-5.5) were alpha1-6 fucosylated and might be linked to suppression of intrahepatic metastasis. This is the first demonstration of the biological significance of alpha1-6 fucosylation on N-glycans in hepatoma cells under in vivo conditions.

Animals↗
PubMed1999

Acceleration of adhesion of cancer cells and neutrophils to endothelial cells in the absence of de novo protein synthesis: possible implication for involvement of hydroxyl radicals.

The adhesion of colon cancer cells (colo201) and neutrophils to endothelial cells which had been briefly exposed to either hypoxanthine/xanthine oxidase, or hydrogen peroxide, or peroxynitrite was analyzed in the absence of de novo protein synthesis. Such treatments accelerated the adhesions of both colo201 cells and neutrophils to endothelial cells. These effects were blocked by SOD/catalase or EDTA. The results provided evidence that hydroxyl radicals affect the cell surface of endothelial cells and accelerate cell adhesion.

Catalase↗
PubMed1999

cDNA cloning and expression of rat homeobox gene, Hex, and functional characterization of the protein.

We isolated two cDNA clones of rat Hex, a homeobox protein, studied its expression in rat liver and various cells, and characterized the protein. The levels of Hex mRNA were only slightly increased in liver of rats refed with a high-carbohydrate diet or after partial hepatectomy. Whereas the expression of Hex mRNA was detected in hepatocytes isolated from adult rat liver and also in highly differentiated hepatoma cells, no Hex mRNA was detected in poorly differentiated hepatoma cells. Hex mRNA was also detected in liver from embryo aged 15 days. Expression of Hex was increased in F9 cells during differentiation into visceral endoderm cells by treatment with retinoic acid. This stimulation occurred prior to an increase in the level of alpha-fetoprotein mRNA. When fusion-protein expression vectors of GAL4 DNA-binding domain and Hex were co-transfected with luciferase reporter plasmid, with or without five copies of the GAL4-binding site, into HepG2 cells, the luciferase activities were decreased in concentration- and GAL4-binding site-dependent manners. This repression did not require the presence of the homeodomain, which is located between the amino acid residues 137 and 196. Its repression domain was mapped between the residues 45 and 136 in the proline-rich N-terminal region. In addition, the homeodomain was responsible for DNA-binding of Hex. These results indicate that Hex functions as a transcriptional repressor and may be involved in the differentiation and/or maintenance of the differentiated state in hepatocytes.

Amino Acid Sequence↗
PubMed1999

Brain-derived neurotrophic factor prevents low-frequency inputs from inducing long-term depression in the developing visual cortex.

Brain-derived neurotrophic factor (BDNF) is reported to enhance synaptic transmission and to play a role in long-term potentiation in hippocampus and neocortex. If so, a shortage or blockade of BDNF might lead to another form of synaptic plasticity, long-term depression (LTD). To test this possibility and to elucidate mechanisms if it is the case, EPSCs evoked by test stimulation of layer IV were recorded from layer II/III neurons in visual cortical slices of young rats in the whole-cell voltage-clamp mode. LTD was induced by low-frequency stimulation (LFS) at 1 Hz for 10-15 min if each pulse of the LFS was paired with depolarization of neurons to -30 mV but was not induced if their membrane potentials were kept at -70 mV. Such an LTD was blocked by exogenously applied BDNF, probably through presynaptic mechanisms. Suppression of endogenous BDNF activity by the anti-BDNF antibody or an inhibitor for BDNF receptors made otherwise ineffective stimuli (LFS without postsynaptic depolarization) effective for LTD induction, suggesting that endogenous BDNF may prevent low-frequency inputs from inducing LTD in the developing visual cortex.

Aging↗
PubMed1999

Cloning of the peroxiredoxin gene family in rats and characterization of the fourth member.

Peroxiredoxin (PRx) exhibits thioredoxin-dependent peroxidase activity and constitutes a family of proteins. Four members of genes from rat tissues were isolated by PCR using degenerated primers based on the sequences which encode a pair of highly conserved Cys-containing domains, and were then cloned to full-length cDNAs. These included two genes which have previously been isolated in rats, PRx I and PRx II, and two rat homologues of PRx III and PRx IV. We showed, for the first time, the simultaneous expression of all four genes in various rat tissues by Northern blotting. Since a discrepancy exists regarding cellular distribution, we further characterized PRx IV by expressing it in COS-1 cells. This clearly demonstrates that PRx IV is a secretory form and functions within the extracellular space.

Amino Acid Sequence↗
PubMed1999

Expression and prognostic roles of the G1-S modulators in hepatocellular carcinoma: p27 independently predicts the recurrence.

Expression of cell-cycle modulators at the G1-S boundary, retinoblastoma gene product (pRb), p21, p16, p27, p53, cyclin D1, and cyclin E was investigated with 104 hepatocellular carcinomas (HCC), as well as 90 of their adjacent noncancerous lesions and 9 normal liver control specimens. The labeling indices (LI) of pRb, p21, p16, and p27 were higher in HCC lesions than in the adjacent noncancerous lesions and normal controls. Especially, p27 LI in noncancerous lesions was significantly higher than that in normal livers (P =.011). Aberrant p53 expression and cyclin D1 and E overexpression were observed exclusively in HCC lesions. pRb was positive in 85.6% of the HCC cases and was not related to any clinicopathological parameters. The p21 LI was generally low (average, 5.5 +/- 9.8). Although a negative regulator, p21 LI was higher in cases with intrahepatic metastasis (P =.0359). The p16 LI was significantly decreased (P =.0121) in cases with advanced stage. p27 LI was significantly decreased in cases with portal invasion (P =.0409), poor differentiation (P <.0001), larger size (P =.0421), and intrahepatic metastasis (P =.0878, borderline significance). On the other hand, aberrant p53 expression showed positive relationships with poor differentiation (P =.0004) and Ki-67 LI (P =. 0047). Cyclin D1 overexpression was found in 32.6% of the cases and occurred more frequently in those with high Ki-67 LI (P =.0032), pRb expression (P =.0202), poor differentiation (P =.0612, borderline significance), and intrahepatic metastasis (P =.0675, borderline significance). Cyclin E was overexpressed in 35.5% and had positive relationships with Ki-67 LI (P =.0269) and stage (P =.0125). In univariate analysis, cases with p27 LI < 50 (P =.0004), cyclin D1 overexpression (P =.0041), and cyclin E overexpression (P =.0572, borderline significance) showed poorer outcomes for disease-free survival (DFS). In multivariate analysis, p27 expression could be recognized as an independent prognostic marker for DFS. These findings suggest that in HCC: 1) p27 is active against HCC progression in early phases and, possibly, hepatocarcinogenesis as a negative regulator and can be a novel prognostic marker for DFS; and 2) cyclin D1 predominantly works for cell-cycle progression at the G1-S boundary.

Adult↗
PubMed1999

Expression and characterization of the extracellular domain of guanylyl cyclase C from a baculovirus and Sf21 insect cells.

Guanylyl cyclase (GC)-C, a single-transmembrane receptor protein for heat-stable enterotoxin, guanylin, and uroguanylin, and its N-terminal extracellular domain were prepared at a high level of expression from a system constructed of Sf21 insect cells and recombinant baculovirus. The recombinant GC-C, containing the complete sequence, retained its binding affinity to heat-stable enterotoxin with a KD value (6.2 x 10(-10) M) and cyclase catalytic activity at a level similar to those of GC-C expressed in mammalian cell lines, such as COS-7. The N-terminal extracellular domain was prepared in a form which contained the hexahistidine tail at its C-terminus and was purified as a homogenous protein by Con A and Ni-chelating affinity chromatography from the culture medium of the insect cells. The purified N-terminal extracellular domain of GC-C exhibited the high (KD = 4 x 10(-10) M) and low (KD = 7 x 10(-8) M) affinity sites in binding to heat-stable enterotoxin. These results clearly indicate that the N-terminal extracellular domain of GC-C possesses the same biochemical characteristics as the complete GC-C protein even in the membrane-free form. Moreover, the extracellular domain is able to form an oligomer in a ligand-dependent manner, suggesting that the N-terminal extracellular domains interact with one another in binding to ligands.

Animals↗