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N Taniguchi

Publications and source records attributed to N Taniguchi.

At least 19 recordsLinked to original sources
PubMed2001

Elevated expression of UDP-N-acetylglucosamine: alphamannoside beta1,6 N-acetylglucosaminyltransferase is an early event in hepatocarcinogenesis.

Previous reports have suggested that changes in oligosaccharide structures, especially beta1-6 branching in N-glycans, which are biosynthesized by UDP-N-acetylglucosamine:alpha mannoside beta1,6 N-acetylglucosaminyltransferase (GnT-V), are linked to tumor metastasis and invasion. In the present study, we investigated GnT-V expression in human hepatocellular carcinoma (HCC) tissues. High expression of GnT-V mRNA was observed in both HCC and the surrounding tissues but not in normal liver. Immunohistochemical study using a newly established monoclonal antibody against GnT-V revealed that positive staining of GnT-V was observed in 75% of HCC tissues and 60% of surrounding tissues and that liver cirrhosis showed much stronger staining of GnT-V than chronic hepatitis without liver cirrhosis (p = 0.0035). In contrast, all of 12 cases of atypical adenomatous hyperplasia diffusely expressed GnT-V. beta1-6 branching in N-glycans, products of GnT-V, was increased in HCC tissues with high expression of GnT-V, as judged by lectin blotting. Levels of GnT-V expression in HCC tissues were positively correlated with a low Ki-67 labeling index (p = 0.0009), small size (p < 0.0001), poor differentiation (p < 0.0001) and absence of portal invasion (p = 0.018). Furthermore, HCC cases with low or no expression of GnT-V were more likely to show recurrence than cases with high expression (p = 0.0373). These findings strongly suggest that GnT-V expression is concerned mainly with an early phase of hepatocarcinogenesis.

Aged↗
PubMed2001

Domain-specific mutations of a transforming growth factor (TGF)-beta 1 latency-associated peptide cause Camurati-Engelmann disease because of the formation of a constitutively active form of TGF-beta 1.

Transforming growth factor (TGF)-beta1 is secreted as a latent form, which consists of its mature form and a latency-associated peptide (beta1-LAP) in either the presence or the absence of additional latent TGF-beta1-binding protein. We recently reported that three different missense mutations (R218H, R218C, and C225R) of beta1-LAP cause the Camurati-Engelmann disease (CED), an autosomal dominant disorder characterized by hyperosteosis and sclerosis of the diaphysis of the long bones. Pulse-chase experiments using fibroblasts from CED patients and expression experiments of the mutant genes in an insect cell system suggest that these mutations disrupt the association of beta1-LAP and TGF-beta1 and the subsequent release of the mature TGF-beta1. Furthermore, the cell growth of fibroblasts from a CED patient and mutant gene-transfected fibroblasts was suppressed via TGF-beta1. The growth suppression observed was attenuated by neutralizing antibody to TGF-beta1 or by treatment of dexamethasone. On the other hand, the proliferation of human osteoblastic MG-63 cells was accelerated by coculture with CED fibroblasts. These data suggest that the domain-specific mutations of beta1-LAP result in a more facile activation of TGF-beta1, thus causing CED.

Camurati-Engelmann Syndrome↗
PubMed2001

Glycoxidation and lipid peroxidation of low-density lipoprotein can synergistically enhance atherogenesis.

OBJECTIVE: The purpose of this study was to clarify the role of glycoxidation and lipid peroxidation of low-density lipoprotein (LDL) in atherogenesis. METHODS AND RESULTS: We examined the formation of N(epsilon)-(carboxymethyl) lysine (CML), a glycoxidation product, and malondialdehyde (MDA), a lipid peroxidation product, in vitro and their co-localization in human atherosclerotic lesions. Immunochemical analysis revealed that CML was formed in a time-dependent manner by human LDL incubated with copper ions and glucose, i.e. an in vitro model of glycoxidation of LDL. When LDL was exposed to copper ions alone, a small amount of CML was formed, however this was significantly less in oxidized LDL than glycoxidative LDL. In contrast, MDA formation was observed in both oxidation and glycoxidation of LDL, but not in glycation of LDL. Hexitol-lysine (HL), an Amadori product, was formed by both glycation and glycoxidation of LDL, but not by oxidation of LDL. Immunohistochemical analysis showed that CML and MDA accumulated mainly in macrophage/foam cells, while pyrraline, a non-oxidative product of glycation, and apolipoprotein B were localized in the extracellular matrix in atherosclerotic lesions. Atheromas were positive for CML and MDA, but negative for pyrraline. Macrophage/foam cells in atherosclerotic lesions exhibited co-localization of macrophage scavenger receptor-A with CML and MDA, but not with pyrraline. CONCLUSION: Our results suggest that glycoxidation and lipid peroxidation of LDL synergistically promote the development of atherosclerotic lesions through interaction with macrophage scavenger receptor-A.

Adult↗
PubMed2001

The critical role of the stem region as a functional domain responsible for the oligomerization and Golgi localization of N-acetylglucosaminyltransferase V. The involvement of a domain homophilic interaction.

We demonstrated that a region in the stem of N-acetylglucosaminyltransferase V (GnT-V), a Golgi resident protein, is not required for enzyme activity but serves as functional domain, responsible for intracellular localization. Deletion of the domain led to complete retention of the kinetic properties but resulted in the cell surface localization of the enzyme as well as its efficient secretion into the medium. The lack of this domain concomitantly abolished the disulfide-mediated oligomerization of GnT-V, which appears to confer the Golgi retention. When the domain was inserted into the stem region of a cell surface-localized type II membrane protein, the resulting chimeric protein was substantially oligomerized and predominantly localized in the intracellular organelle. Furthermore, it was found that the presence of this domain is exclusively responsible for homo-oligomer formation. This homophilic interaction appears to involve a hydrophobic cluster of residues in the alpha-helix of the domain, as indicated by secondary structure predictions. These findings suggest that the domain specifically participates in the Golgi retention of GnT-V, probably via inducing homo-oligomer formation, and would also provide a possible mechanism for the oligomerization, which is critical for localization in the Golgi.

Animals↗
PubMed2001

Molecular cloning and characterization of a human beta-Gal-3'-sulfotransferase that acts on both type 1 and type 2 (Gal beta 1-3/1-4GlcNAc-R) oligosaccharides.

A novel sulfotransferase gene (designated GP3ST) was identified on human chromosome 2q37.3 based on its similarity to the cerebroside 3'-sulfotransferase (CST) cDNA (Honke, K., Tsuda, M., Hirahara, Y., Ishii, A., Makita, A., and Wada, Y. (1997) J. Biol. Chem. 272, 4864-4868). A full-length cDNA was obtained by reverse transcription-polymerase chain reaction and 5'- and 3'-rapid amplification of cDNA ends analyses of human colon mRNA. The isolated cDNA clone predicts that the protein is a type II transmembrane protein composed of 398 amino acid residues. The amino acid sequence indicates 33% identity to the human CST sequence. A recombinant protein that is expressed in COS-1 cells showed no CST activity, but did show sulfotransferase activities toward oligosaccharides containing nonreducing beta-galactosides such as N-acetyllactosamine, lactose, lacto-N-tetraose (Lc4), lacto-N-neotetraose (nLc4), and Gal beta 1-3GalNAc alpha-benzyl (O-glycan core 1 oligosaccharide). To characterize the cloned sulfotransferase, a sulfotransferase assay method was developed that uses pyridylaminated (PA) Lc4 and nLc4 as enzyme substrates. The enzyme product using PA-Lc4 as an acceptor was identified as HSO(3)-3Gal beta 1-3GlcNAc beta 1-3Gal beta 1- 4Glc-PA by two-dimensional (1)H NMR. Kinetics studies suggested that GP3ST is able to act on both type 1 (Gal beta 1-3GlcNAc-R) and type 2 (Gal beta 1-4GlcNAc-R) chains with a similar efficiency. In situ hybridization demonstrated that the GP3ST gene is expressed in epithelial cells lining the lower to middle layer of the crypts in colonic mucosa, hepatocytes surrounding the central vein of the liver, extravillous cytotrophoblasts in the basal plate and septum of the placenta, renal tubules of the kidney, and neuronal cells of the cerebral cortex. The results of this study indicate the existence of a novel beta-Gal-3'-sulfotransferase gene family.

Amino Acid Sequence↗
PubMed2001

The addition of bisecting N-acetylglucosamine residues to E-cadherin down-regulates the tyrosine phosphorylation of beta-catenin.

The enzyme GnT-III (beta 1,4-N-acetylglucosaminyltransferase III) catalyzes the addition of a bisecting N-acetylglucosamine (GlcNAc) residue on glycoproteins. Our previous study described that the transfection of GnT-lll into mouse melanoma cells results in the enhanced expression of E-cadherin, which in turn leads to the suppression of lung metastasis. It has recently been proposed that the phosphorylation of a tyrosine residue of beta-catenin is associated with cell migration. The present study reports on the importance of bisecting GlcNAc residues by GnT-lll on tyrosine phosphorylation of beta-catenin using three types of cancer cell lines. An addition of bisecting GlcNAc residues to E-cadherin leads to an alteration in cell morphology and the localization of beta-catenin after epidermal growth factor stimulation. These changes are the result of a down-regulation in the tyrosine phosphorylation of beta-catenin. In addition, tyrosine phosphorylation of beta-catenin by transfection of constitutively active c-src was suppressed in GnT-III transfectants as well as in the case of epidermal growth factor stimulation. Treatment with tunicamycin abolished any differences in beta-catenin phosphorylation for the mock vis à vis the GnT-lll transfectants. Thus, the addition of a specific N-glycan structure, the bisecting GlcNAc to E-cadherin-beta-catenin complex, down-regulates the intracellular signaling pathway, suggesting its implication in cell motility and the suppression of cancer metastasis.

Acetylglucosamine↗
PubMed2001

Sonographic findings in Shigella colitis.

We present a case of colitis caused by Shigella sonnei in which abdominal sonography helped in the early diagnosis, leading to successful conservative management. Sonography showed diffuse wall thickening and layer stratification in the descending and sigmoid colon. Although Shigella colitis is relatively rare, the possibility must be considered when patients have diffuse wall thickening with distinct layer stratification in the left colon.

Aged↗
PubMed2001

Temporal changes in allele frequency, genetic variation and inbreeding depression in small populations of the guppy, Poecilia reticulata.

We established three closed lines of N = 10 for the guppy Poecilia reticulata, to evaluate the relationships among temporal changes in allele frequency, genetic variation and inbreeding depression for a fitness-related trait in small populations. Genetic variation at the allozyme loci, expressed by the proportion of polymorphic loci, number of alleles per locus and heterozygosity, decreased somewhat in two closed lines but it increased in one closed line over six generations. Effective population size (Ne) at each generation was estimated from the standardized variance in the allele frequencies. The average Ne was 24.4, 10.3 and 10.0 in the three closed lines. The inbreeding coefficient calculated from the Ne increased to 0.186, 0.321 and 0.414, respectively. As an index of the amount of inbreeding depression, changes in salinity tolerance were examined, because this trait is strongly sensitive to inbreeding depression and decreases linearly with an increase in inbreeding coefficient. The mean value of the salinity tolerance significantly decreased to 82.5%, 71.7% and 67.6% in the three closed lines during the six generations, suggesting inbreeding depression for salinity tolerance. Although a significant correlation was not observed between the amount of inbreeding depression and the genetic variation, the amount of inbreeding depression correlated with the inbreeding coefficient calculated from Ne. The regression line indicated an 8.4% decrease in the mean per 10% increase in the inbreeding coefficient and was similar to that obtained directly from full-sib matings. These results indicate that the temporal changes in the allele frequencies can provide an estimation of the amount of inbreeding depression during successive generations in small populations.

Adaptation, Physiological↗
PubMed2001

Augmented expression of peroxiredoxin VI in rat lung and kidney after birth implies an antioxidative role.

A family of proteins with thioredoxin (TRx)-dependent peroxidase activity, referred to as peroxiredoxins (PRx), has been identified in many species. The sixth member of this family, PRxVI, contains only one conserved cysteine residue, while other members contain additional cysteines. We have isolated a cDNA for rat PRxVI and constructed a large scale baculovirus system to produce the recombinant protein. The protein was purified by a simple two-step procedure utilizing ion-exchange and gel-filtration chromatography. The purified PRxVI exhibited a low level of glutathione-dependent peroxidase but not TRx-dependent activity. PRxVI expression was the highest in lung, followed by brain, kidney, heart, testis, etc. as judged by Northern and Western blot analyses using a rabbit antibody to the purified PRxVI. Immunohistochemical analyses showed strong staining in the epithelium of the bronchus and bronchioles in lung and in the epithelial cells of kidney tubules. In addition, Sertoli cells in testis and islet of Langerhans cells in pancreas were strongly stained. The developmental changes of PRxVI expression in lung and kidney were low in the prenatal stage but induced postnatally. Moreover, intraperitoneal administration of chloroform induced PRxVI mRNA in kidney. When the distribution and the induced expression of PRxVI under conditions of oxidative stress are considered, a physiological role of it as an antioxidative enzyme is indicated.

Amino Acid Sequence↗
PubMed2001

Alteration of antioxidants during the progression of heart disease in streptozotocin-induced diabetic rats.

Involvement of oxidative stress is implicated in the progression of complication of diabetes mellitus. With respect to heart diseases, we have studied role of oxidative stress/antioxidants using rats treated with streptozotocin to induce diabetes (DM). Hemodynamic and echocardiographic measurements showed thickening of the wall and an increase in the internal dimension of the left ventricle (LV) in DM rats at 8th week. Decrease in diastolic posterior wall velocity and rate of LV pressure change, and increase in LV end diastolic pressures also proved cardiac dysfunction. These changes were further developed in DM rats after 12 weeks. Utilizing rat hearts at 8th and 12th weeks, the following estimations were performed. There was a decrease in the activity of Mn-superoxide dismutase (SOD), suggesting abnormal mitochondrial metabolism of reactive oxygen species. The level of glutathione (GSH) decreased concomitant with a decrease in the expression of gamma-glutamylcysteine synthetase (gamma-GCS). The expression of transforming growth factor-beta1 (TGF-beta1), known as a growth factor and a suppressor of GSH synthesis, elevated in DM rat hearts. Immunohistochemical estimation showed an increase in type IV collagen in DM hearts. Collectively, it was suggested a linkage between mitochondrial damage to generate reactive oxygen species and inactivation of Mn-SOD and elevation of the expression of TGF-beta1 to lead suppression of GSH synthesis and induction of fibrous change for the consequent cardiac dysfunction in DM.

Animals↗
PubMed2001

Ectopic expression of alpha1,6 fucosyltransferase in mice causes steatosis in the liver and kidney accompanied by a modification of lysosomal acid lipase.

The alpha1,6 fucosyltransferase (alpha1,6 FucT) catalyzes the transfer of a fucose from GDP-fucose to the innermost GlcNAc residue of N-linked glycans via an alpha1,6 linkage. alpha1,6 FucT was overexpressed in transgenic mice under the control of a combined cytomegalovirus and chicken beta-actin promoter. Histologically numerous small vacuoles, in which lipid droplets had accumulated, were observed in hepatocytes and proximal renal tubular cells. Electron microscopic studies showed that the lipid droplets were membrane-bound and apparently localized within the lysosomes. Cholesterol esters and triglycerides were significantly increased in liver and kidney of the transgenic mice. Liver lysosomal acid lipase (LAL) activity was significantly lower in the transgenic mice compared to the wild mice, whereas LAL protein level, which was detected immunochemically, was increased, indicating that the specific activity of LAL was much lower in the transgenic mice. In all of the transgenic and nontransgenic mice examined, the activity of liver LAL was negatively correlated with the level of alpha1,6 FucT activity. As evidenced by lectin and immunoblot analysis, LAL was found to be more fucosylated in the transgenic mice, suggesting that the aberrant fucosylation of LAL causes an accumulation of inactive LAL in the lysosomes. Such an accumulation of inactive LAL could be a likely cause for a steatosis in the lysosomes of the liver and kidney in the case of the alpha1,6 FucT transgenic mice.

Animals↗
PubMed2001

Roles of N-terminal active cysteines and C-terminal cysteine-selenocysteine in the catalytic mechanism of mammalian thioredoxin reductase.

Mammalian thioredoxin reductase [EC 1.6.4.5], a homodimeric flavoprotein, has a marked similarity to glutathione reductase. The two cysteines in the N-terminal FAD domain (-Cys59-x-x-x-x-Cys64-) and histidine (His472) are conserved between them at corresponding positions, but the mammalian thioredoxin reductase contains a C-terminal extension of selenocysteine (Sec or U) at the penultimate position and a preceding cysteine (-Gly-Cys497-Sec498-Gly). Introduction of mutations into the cloned rat thioredoxin reductase gene revealed that residues Cys59, Cys64, His472, Cys497, and Sec498, as well as the sequence of Cys497 and Sec498 were essential for thioredoxin-reducing activity. To analyze the catalytic mechanism of the mammalian thioredoxin reductase, the wild-type, U498C, U498S, C59S, and C64S were overproduced in a baculovirus/insect cell system and purified. The wild-type thioredoxin reductase produced in this system, designated as WT, was found to lack the Sec residue and to terminate at Cys497. A Sec-containing thioredoxin reductase, which was purified from COS-1 cells transfected with the wild-type cDNA, was designated as SecWT and was used as an authentic enzyme. Among mutant enzymes, only U498C retained a slight thioredoxin-reducing activity at about three orders magnitude lower than SecWT. WT, U498C, and U498S showed some 5,5'-dithiobis(2-nitrobenzoic acid)-reducing activity and transhydrogenase activity, and C59S and C64S had substantially no such activities. These data and spectral analyses of these enzymes suggest that Cys59 and Cys64 at the N-terminus, in conjunction with His472, function as primary acceptors for electrons from NADPH via FAD, and that the electrons are then transferred to Cys497-Sec498 at the C-terminus for the reduction of oxidized thioredoxin in the mammalian thioredoxin reductase.

Animals↗
PubMed2001

The property of a novel v2 receptor mutant in a patient with nephrogenic diabetes insipidus.

Nephrogenic diabetes insipidus (NDI) is characterized by resistance of the kidneys to the action of arginine vasopressin (AVP); X-linked recessive NDI is caused by an inactivating mutation of the vasopressin type-2 (V2) receptor. Several missense mutations in the first or second extracellular loop of the V2 receptor have been reported, and some of these mutant receptors were confirmed to have reduced affinities for ligand binding. We detected a novel V2 receptor gene mutation, a substitution of cysteine for arginine-104 (R104C) located in the first extracellular loop of the V2 receptor, in a patient with congenital NDI. Functional analysis by transient expression studies with COS-7 cells showed binding capacity of R104C mutant diminished as 10% of wild type, but binding affinity was strong rather than wild type. In the result of AVP stimulation studies, maximum cAMP accumulation of R104C decreased as 50% of wild type. On the other hand, a designed mutant receptor, substituted serine for arginine-104 as a model of modified R104C mutant receptor removed the influence of the sulfhydryl group in cysteine-104, recovered binding capacity up to 50% of wild type and maximum cAMP accumulation as 82% of wild type. Our study demonstrated that the R104C mutation of the V2 receptor was a cause of NDI. The mechanism of renal resistance to AVP was the reduction of ligand binding, and adenylyl cyclase activation depended on the V2 receptor. In addition, we confirmed that the sulfhydryl group of the cysteine-104 caused most part of R104C mutant receptor dysfunction.

Amino Acid Sequence↗
PubMed2001

A high dose of vitamin E inhibits adrenal corticosterone synthesis in chickens treated with ACTH.

The present experiment was conducted to study the effects of dietary vitamin E on plasma corticosterone (CTC) concentration and adrenal steroid syntheses in chickens treated with adrenocorticotropic hormone (ACTH). Chickens were divided into ACTH(-) and ACTH(+) groups, and each group was further divided into three subgroups administered with vitamin E (500 or 5,000 mg/kg diet) and without the vitamin. Vitamin E (DL-alpha-tocopheryl acetate) was mixed with the basal diet at levels of 500 and 5,000 mg/kg and fed for 6 d. ACTH (20 IU/kg body weight) was given daily by intraperitoneal injection for 5 d. alpha-Tocopherol levels in the plasma and adrenal gland were markedly elevated by vitamin E feeding, and the level of adrenal free cholesterol (CHOL), which is used for steroid synthesis, was significantly decreased by vitamin E feeding in a dose-dependent manner. However, the level of adrenal CHOL ester was unchanged by any treatment. The elevations of pregnenolone, progesterone and CTC levels in the adrenal gland of chickens with ACTH treatment were decreased by vitamin E administration. The elevation of plasma CTC concentration in the ACTH(+) group was dramatically decreased by vitamin E administration, while that concentration was not influenced by the vitamin administration in the ACTH(-) group. These findings indicate that vitamin E suppresses the elevation of the plasma CTC concentration due to ACTH in chickens, possibly by inhibiting the conversion of CHOL ester to free CHOL in the adrenal gland.

Adrenal Glands↗
PubMed2001

[A case of bilateral renal cell carcinoma showing a rapid course of death in a long-term hemodialysis patient due to polycystic kidney].

A case of bilateral renal cell carcinoma in a 42-year-old polycystic kidney male is reported. He had been treated with hemodialysis for 22 years. An abnormal small mass was found in one of the left renal cystic lesions by screening ultrasonography and CT scan at the 19th year of the hemodialysis. Left radical nephrectomy was performed and the histological diagnosis was a renal cell carcinoma (RCC). There was no evidence of recurrence and metastasis, however, he presented with asymptomatic macrohematuria two years after the operation. CT scan demonstrated the rapidly progressing right renal tumor and multiple para-aortic lymph node swelling. Right nephrectomy and lymphadenectomy were performed and pathological examination showed the advanced RCC with multiple lymph node metastasis. Eleven months after the second operation followed by interferon therapy. he died of multiorgan metastasis of the RCC. This is the first bilateral RCC case in polycystic kidney patient treated with hemodialysis in Japan.

Adult↗
PubMed2000

Overexpression of N-acetylglucosaminyltransferase III enhances the epidermal growth factor-induced phosphorylation of ERK in HeLaS3 cells by up-regulation of the internalization rate of the receptors.

N-Acetylglucosaminyltransferase III (GnT-III) is a key enzyme that inhibits the extension of N-glycans by introducing a bisecting N-acetylglucosamine residue. In this study we investigated the effect of GnT-III on epidermal growth factor (EGF) signaling in HeLaS3 cells. Although the binding of EGF to the epidermal growth factor receptor (EGFR) was decreased in GnT-III transfectants to a level of about 60% of control cells, the EGF-induced activation of extracellular signal-regulated kinase (ERK) in GnT-III transfectants was enhanced to approximately 1.4-fold that of the control cells. A binding analysis revealed that only low affinity binding of EGF was decreased in the GnT-III transfectants, whereas high affinity binding, which is considered to be responsible for the downstream signaling, was not altered. EGF-induced autophosphorylation and dimerization of the EGFR in the GnT-III transfectants were the same levels as found in the controls. The internalization rate of EGFR was, however, enhanced in the GnT-III transfectants as judged by the uptake of (125)I-EGF and Oregon Green-labeled EGF. When the EGFR internalization was delayed by dansylcadaverine, the up-regulation of ERK phosphorylation in GnT-III transfectants was completely suppressed to the same level as control cells. These results suggest that GnT-III overexpression in HeLaS3 cells resulted in an enhancement of EGF-induced ERK phosphorylation at least in part by the up-regulation of the endocytosis of EGFR.

Endocytosis↗
PubMed2000

alpha1,6fucosyltransferase is highly and specifically expressed in human ovarian serous adenocarcinomas.

An elevated level of alpha1,6fucosylation in N-glycans represents one of the cancer-related alterations of oligosaccharides and is associated with the metastatic potential of hepatoma cells. However, expression of alpha1,6fucosyltransferase (alpha1,6FucT), which is involved in this aberrant glycosylation, has not been intensively explored in other malignant tumors. We report on a study of the expression of alpha1,6FucT in various types of epithelial ovarian carcinoma tissue, as well as normal ovary, benign and borderline ovarian tumors. The activity assay showed that alpha1,6FucT is highly and specifically elevated in serous adenocarcinomas but not in normal and other ovarian tumor tissues. This elevation was due to enhancement of mRNA expression, as evidenced by Northern blot analysis. Furthermore, we have shown immunohistochemically that alpha1,6FucT expression is localized predominantly in cancer cells. Lectin blot analysis using Lens culinaris agglutinin, which preferentially recognizes alpha1,6fucose residue, suggested that several glycoproteins were likely targets for modification by alpha1, 6fucosylation in serous adenocarcinoma tissues. These findings suggest that the elevated expression of alpha1,6FucT and the resulting modification of N-glycans are distinctive features of this type of ovarian cancer and may be related to the progression of this malignancy.

Adult↗