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Masaki Ito

Publications and source records attributed to Masaki Ito.

At least 19 recordsLinked to original sources
PubMed2006

Elicitor-induced down-regulation of cell cycle-related genes in tobacco cells.

The fungal elicitors, a xylanase from Trichoderma viride and an extract from the cell wall of Phytophthora infestans, are shown to cause a rapid reduction of the mRNA levels of various cell cycle-related genes, including MAP kinase genes and cyclin genes, in cultured tobacco cells (Nicotiana tabacum cv. Xanthi, line XD6S). Pharmacological analyses suggest that the elicitor-induced decrease in Bi-type cyclin (Nicta;CycB1;3) and A1-type cyclin (Nicta;CycA1;1) mRNAs may be due to transcriptional repression, and that in D3-type cyclin (Nicta;CycD3;2) mRNA due to destabilization of the mRNA molecule itself. The activity of protein kinases is required for both the activation of defence genes and the repression of cyclin genes. The transcriptional activity of the promoter of the B1-class cyclin gene decreases upon elicitor treatment. The transactivation activity of NtmybA2, a tobacco Myb transcription activator for the M phase-specific cis-acting elements in the promoter of the B-type cyclin gene, is inhibited by elicitor treatment. In addition, the mRNA levels of NtmybA2 and two other related genes, NtmybA1 and NtmybB, decrease in response to the elicitor. Finally, we discuss a negative cross-talk between signal transduction pathways for growth and defence responses, which might be important for adaptation to environmental stress by potential pathogens.

Biological Factors↗
PubMed2006

[Motor cortex stimulation for post-stroke pain using neuronavigation and evoked potentials: report of 3 cases].

Although motor cortex stimulation (MCS) has been accepted as an effective therapeutic option for central pain, the efficacy of MCS widely varies among previous reports. In this report, we describe our recent trial for successful MCS in 3 patients with central pain due to cerebral stroke. Medical treatments were transiently effective, but gradually became ineffective in all of the cases. During surgery, the appropriate cortical target was determined by using neuronavigation, somatosensory evoked potential (SEP), and motor evoked potential (MEP). A flat, four-plate electrode was positioned on the dura mater parallel to the motor cortex. After surgery, pain almost resolved in 2 of 3 patients and markedly improved in another. The pain relief depended on their motor function. These findings strongly suggest that both patient selection and intraoperative monitoring for targeting the motor cortex are quite important for successful MCS, although further studies were essential.

Aged↗
PubMed2005

Response to darkness of late-responsive dark-inducible genes is positively regulated by leaf age and negatively regulated by calmodulin-antagonist-sensitive signalling in Arabidopsis thaliana.

Induction after prolonged darkness distinguishes the late-responsive genes din2 and din9 from the early-responsive gene din3 in Arabidopsis. The former genes were coincidently induced with the senescence marker gene YLS4 in rosette leaves of different ages and in the early-senescence mutant hys1. The calmodulin antagonists W-7, trifluoperazine, and fluphenazine accelerated the expression of the former genes in darkness but not in light, and had little effect on the latter gene. Our results suggest that Ca(2+)/calmodulin signalling conveys a negative signal that suppresses the responses of late-responsive din genes to prolonged darkness. The results are discussed in relation to natural senescence.

Arabidopsis↗
PubMed2005

Conservation and diversification of three-repeat Myb transcription factors in plants.

The Myb family of transcription factors is characterized by the presence of a conserved DNA-binding domain called the Myb domain, which typically contains two or three imperfect repeat sequences. Within this family, Myb proteins containing three repeat motifs are evolutionarily conserved and have important roles in the cell cycle. Vertebrates have three Myb proteins, c-Myb, A-Myb, and B-Myb, all of which contain three repeats and are proposed to have a role at the G1/S transition. In plants, Myb proteins with three repeats are encoded by genes in a small subfamily within the large Myb gene family, most of which encode for Myb proteins with only two repeats. We have shown that Myb proteins with three repeats have an important role at the G2/M in tobacco, by regulating transcription of cyclin B genes and many other genes that are expressed at a similar time in the cell cycle. In this review, we summarize current knowledge on structure, function, and regulation of the plant Myb factors with three repeats, and discuss their conserved and divergent features in comparison with animal counterparts.

Amino Acid Motifs↗
PubMed2005

Transcriptional activation of tobacco E2F is repressed by co-transfection with the retinoblastoma-related protein: cyclin D expression overcomes this repressor activity.

Evidence is emerging that the E2F family of transcription factors plays an important role in the regulation of gene expression at the G1/S transition in plants. Here, we show that in the tobacco proliferating cell nuclear antigen (PCNA), whose transcript is specifically expressed at G1/S phase, the two E2F binding sites are synergistically responsible for transcriptional activation at G1/S phase in synchronized tobacco BY-2 cells transformed with promoter constructs fused to a reporter gene. In addition, we have isolated the tobacco DP cDNA (NtDP) and showed that significant activation of the reporter gene was observed in transient expression assays by concomitantly transfecting with plasmids expressing NtE2F and NtDP. This transcriptional activation was repressed by co-transfection with a plasmid expressing NtRBR1; in vitro pull-down assays also revealed that NtRBR1 binds directly to NtE2F, thereby potentially blocking the transcriptional activation of NtE2F. Importantly, this repressor activity was cancelled when NtRBR1 was further co-transfected with a plasmid expressing cyclin D but not with cyclin A or cyclin B. These results are discussed with respect to the repression activity of NtRBR1 on the NtE2F/NtDP complex.

Amino Acid Sequence↗
PubMed2005

Identification of Pex5pM, and retarded maturation of 3-ketoacyl-CoA thiolase and acyl-CoA oxidase in CHO cells expressing mutant Pex5p isoforms.

Recently, we isolated CHO cells, termed SK32 cells, that express mutant Pex5p (G432R), and showed mislocalization of catalase in the cytosol, but peroxisomal localization of 3-ketoacyl-CoA thiolase (thiolase) in the mutant cells [Ito, R. et al. (2001) Biochem. Biophys. Res. Commun. 288, 321-327]. While analyzing the mutant cells, we found a novel Pex5p isoform (Pex5pM), which was shorter by seven amino acids than Pex5pL and longer by 30 amino acids than Pex5pS. Similar levels of mRNA syntheses for the PEX5 gene were observed in both the wild type and mutant cells, but the protein levels of Pex5p isoforms were markedly reduced in the mutant cells cultured at 37 degrees C and only slightly discernible at 30 degrees C, suggesting that they could be rapidly degraded. Furthermore, we characterized the peroxisomal localization of thiolase and acyl-CoA oxidase (Aox) in SK32 cells. The proteins in the organelle fraction were protected from proteinase K-digestion in the mutant cells, indicating that they were translocated inside peroxisomes. However, the conversion of Aox from component A to components B and C was completely prevented at both 30 and 37 degrees C, and the precursor form of thiolase was partially processed to the mature one in a temperature-sensitive manner. Transformed SK32 cells stably expressing one of the wild type Pex5p isoforms were isolated, and then the maturation steps for thiolase and Aox were examined. Pex5pM and S restored the processing of the two enzymes, but Pex5pL did not. In addition, Pex5pL prevented the maturation of thiolase observed at 30 degrees C. These results indicate that (i) the novel Pex5pM is functional and (ii) a seven amino acids-insertion, which is present in the L isoform but absent in the M isoform, plays some role in the process of maturation of thiolase and Aox.

Acetyl-CoA C-Acyltransferase↗
PubMed2005

The expression of NOV and WT1 in renal cell carcinoma: a quantitative reverse transcriptase-polymerase chain reaction analysis.

PURPOSE: The NOV gene was first identified as an aberrantly expressed gene in avian nephroblastomas induced by myeloblastosis-associated virus. Its expression has been shown to be altered in avian and human nephroblastomas, and to be a target of WT1 regulation. We analyzed the mRNA level of human NOV together with the mRNA level of WT1 in sporadic renal cell carcinoma (RCC). MATERIALS AND METHODS: We quantified NOV and WT1 mRNA levels in surgical specimens from 57 patients with RCC using quantitative real-time polymerase chain reaction analysis. RESULTS: NOV mRNA levels decreased significantly in RCC compared with normal kidney tissue (p <0.001). The NOV mRNA level was higher in papillary than in clear cell RCCs (p = 0.040) and higher in G1 than G2 and 3 tumors (p = 0.01). WT1 was down-regulated in RCCs. No significant relationship was found for NOV and WT1 mRNA levels in our study. CONCLUSIONS: To our knowledge this is the first study to investigate the expression level of the NOV gene in a panel of human RCC tissues together with paired normal renal tissue. Our data indicate that NOV is associated with carcinogenesis and the progression of RCC, and the NOV expression level is different in papillary-type and clear cell-type RCC. There is a possibility that the regulation of NOV expression is different from the pathway regulated by WT1.

Adult↗
PubMed2005

The alc-GR system: a modified alc gene switch designed for use in plant tissue culture.

The ALCR/alcA (alc) two-component, ethanol-inducible gene expression system provides stringent control of transgene expression in genetically modified plants. ALCR is an ethanol-activated transcription factor that can drive expression from the ALCR-responsive promoter (alcA). However, the alc system has been shown to have constitutive expression when used in plant callus or cell suspension cultures, possibly resulting from endogenous inducer produced in response to lowered oxygen availability. To widen the use of the alc system in plant cell culture conditions, the receptor domain of the rat glucocorticoid receptor (GR) was translationally fused to the C terminus of ALCR to produce ALCR-GR, which forms the basis of a glucocorticoid-inducible system (alc-GR). The alc-GR switch system was tested in tobacco (Nicotiana tabacum) Bright Yellow-2 suspension cells using a constitutively expressed ALCR-GR with four alternative alcA promoter-driven reporter genes: beta-glucuronidase, endoplasmic reticulum-targeted green fluorescent protein, haemagglutinin, and green fluorescent protein-tagged Arabidopsis (Arabidopsis thaliana) Arath;CDKA;1 cyclin-dependent kinase. Gene expression was shown to be stringently dependent on the synthetic glucocorticoid dexamethasone and, in cell suspensions, no longer required ethanol for induction. Thus, the alc-GR system allows tight control of alcA-driven genes in cell culture and complements the conventional ethanol switch used in whole plants.

Animals↗
PubMed2005

[Management of asymptomatic newborns with periportal hypodensity and high serum IgM who were born from untreated tuberculosis mothers].

OBJECTIVES: We previously reported the presence of periportal hypodensity on CT image in two newborns and an early infant with congenital tuberculosis as an adjunct diagnostic option. The aim of this study was to determine the degree of treatment based on both periportal hypodensity and serum IgM presented in asymptomatic newborns born from tuberculosis mothers. SUBJECTS AND METHODS: Eight newborns born from mothers with untreated tuberculosis between 1996 and 2002 were retrospectively studied. Newborns who presented periportal hypodensity and high serum IgM were treated with anti-tuberculosis medicines, combination of isoniazid and rifampicin for nine to 12 months with streptomycin in the initial two months, and the outcomes of the treatment were followed for at least two years. RESULTS: All eight newborns had gastric aspirates negative for Mycobacterium tuberculosis. Three of eight newborns (38%) demonstrated periportal hypodensity, and they also demonstrate a tendency of high serum IgM. None of these three newborns treated with combination of isoniazid, rifampin, and streptomycin for 9 to 12 months developed tuberculosis during the observation period. CONCLUSIONS: These results suggest that presence of both periportal hypodensity and high serum IgM in asymptomatic newborns born from mothers with untreated tuberculosis may be one of risk factors of developing congenital tuberculosis, and that anti-tuberculosis treatment for nine to 12 months may prevent them from the disease development despite possible criticism of overdiagnosis and overtreatment.

Female↗
PubMed2004

A novel mechanism for the inhibition of hyaluronan biosynthesis by 4-methylumbelliferone.

Specific inhibitors of hyaluronan (HA) biosynthesis can be valuable therapeutic agents to prevent cancer invasion and metastasis. We have found previously that 4-methylumbelliferone (MU) inhibits HA synthesis in human skin fibroblasts and in group C Streptococcus. In this paper, the inhibition mechanism in mammalian cells was investigated using rat 3Y1 fibroblasts stably expressing HA synthase (HAS) 2. Exposure of the transfectants to the inhibitor resulted in significant reduction of HA biosynthesis and matrix formation. The evaluation of HAS transcripts and analysis of cell-free HA synthesis demonstrated the post-transcriptional suppression of HAS activity by MU. Most interesting, the post-transcriptional suppression of HAS activity was also observed using p-nitrophenol, a well known substrate for UDP-glucuronyltransferases (UGT). We investigated whether the inhibition was exerted by the glucuronidation of MU using both high pressure liquid chromatography and TLC analyses. The production of MU-glucuronic acid (GlcUA) was consistent with the inhibition of HA synthesis in HAS transfectants. MU-GlcUA was also detected at a similar level in control cells, suggesting that the glucuronidation was mediated by an endogenous UGT. Elevated levels of UGT significantly enhanced the inhibitory effects of MU. In contrast, the inhibition by MU was diminished to the control level when an excess of UDP-GlcUA was added to the cell-free HA synthesis system. We propose a novel mechanism for the MU-mediated inhibition of HA synthesis involving the glucuronidation of MU by endogenous UGT resulting in a depletion of UDP-GlcUA.

Animals↗
PubMed2004

Mitotic cyclins stimulate the activity of c-Myb-like factors for transactivation of G2/M phase-specific genes in tobacco.

Myb transcription factors, which contain three imperfect repeats in the Myb domain, are evolutionarily conserved members of the Myb superfamily. Vertebrate Myb proteins with three repeats, c-Myb, A-Myb, and BMyb, play important roles at the G(1)/S transition in the cell cycle. In plants, this type of Myb protein controls the G(2)/M phase by activating or repressing the transcription of cyclin B genes and a variety of other G(2)/M phase-specific genes. In tobacco, two genes for Myb activators, NtmybA1 and NtmybA2, are transcriptionally controlled and are expressed specifically at the G(2)/M phase. As we showed here, in addition to the control at the transcriptional level, activity of NtmybA2 is also controlled at the post-translational level. We found that the transactivation potential of NtmybA2 is repressed by a regulatory domain located at its carboxyl terminus and that specific classes of cyclins A and B enhanced NtmybA2 activity possibly by relieving this inhibitory effect. Mutations at the 20 potential sites of phosphorylation by cyclin-dependent kinase (CDK) in NtmybA2 blocked the enhancing effects of the cyclins on NtmybA2 activity. Recombinant NtmybA2 was phosphorylated in vitro by a CDK fraction prepared from tobacco BY2 cells. The kinase activity for NtmybA2 in the CDK fraction was cell cycle-regulated in BY2 cells, peaking at the G(2)/M phase when the level of transcripts of cyclin B is maximal. Taken together, our data suggest that NtmybA2 is phosphorylated by a specific cyclin/CDK complex(es) at G(2)/M and that this phosphorylation removes the inhibitory effect of its C-terminal region, thereby activating NtmybA2 specifically at G(2)/M.

Binding Sites↗
PubMed2004

Six novel UDP-glucuronosyltransferase (UGT1A3) polymorphisms with varying activity.

Human UDP-glucuronosyltransferase (UGT) is a part of a major excretion pathway for endobiotics and xenobiotics. The UGT family of genes is highly polymorphic, and our aim is to describe novel polymorphisms at the UGT1A3 locus and determine how they alter substrate metabolism and drug reactions. One hundred healthy Japanese adults volunteered for the present study. We sequenced PCR-amplified fragments of the gene directly, and calculated the frequency of the genetic variations detected. To measure variant enzyme activity, we constructed five expression models and used estrone as the substrate in the assays. We identified six novel single nucleotide polymorphisms (SNPs). Of these, four caused amino acid substitutions (17A-->G: Q6R, 31T-->C: W11R, 133C-->T: R45W, and 140T-->C: V47A) and the remaining two were silent (81G-->A: E27E and 447A-->G: A159A). We found five types of alleles having differing SNP combinations: wild type (frequency=0.61), W11R-E27E-A159A (0.10), Q6A-W11R-E27E-A159A (0.055), W11R-E27E-V47A-A159A (0.125), and R45W (0.11). Expression studies found that the variants changed the enzyme efficiencies ( Km/ Vmax) to 121% of the wild type for W11R, 86% for Q6R-W11R, 369% for W11R-V47A, and 70% for R45W. Several UGT 1A3 polymorphisms exist in the Japanese population, having different levels of activity. These polymorphisms are capable of affecting the steady state levels of estrogens, and may increase sensitivity to adverse drug effects.

Alleles↗
PubMed2004

The effects of cholesterol-3-sulfate (CH-3S) on the phosphorylation of human C3a (hC3a) in vitro and on the ability of hC3a to induce vascular permeability in rats.

The phosphorylation of human C3a (hC3a, anaphylatoxin) by two distinct protein kinases (PKA and CK-I) and the effect of cholesterol-3-sulfate (CH-3S) on this phosphorylation were biochemically investigated in vitro. It was found that (i) hC3a functions as a phosphate acceptor for PKA and CK-I, but not for CK-II; (ii) the CK-I-mediated phosphorylation of hC3a requires the presence of 3 microM CH-3S in a manner similar to the phosphorylation of HMG1 (CH-3S-binding protein) by CK-I; and (iii) CH-3S inhibits the PKA-mediated phosphorylation of hC3a in a dose-dependent manner (ID50=approximately 2 microM). As expected, hC3a containing high levels of Arg- and Lys-residues stimulated approx. 3-fold CK-II activity (phosphorylation of alpha-casein) in vitro. However, no significant effect of hC3a on CK-II activity was observed when hC3a was preincubated with CH-3S or fully phosphorylated by PKA in vitro. Furthermore, preincubation of hC3a with CH-3S diminished the ability of hC3a to induce vascular permeability in rats. The results provided here suggest that (i) hC3a is a CH-3S-binding protein; and (ii) CH-3S functions as a potent inhibitor for its physiological activities, including phosphorylation by PKA and CK-I, in vitro.

Animals↗
PubMed2004

[CT imaging findings in congenital tuberculosis, Part I: Usefulness of periportal hypodensity in the diagnosis of congenital tuberculosis].

We treated three newborns and early infants with congenital tuberculosis between 1996 and 2001. We reported imaging presentations of the three cases born in and after 1996 when new CT equipment (CT-HAS-SGS, GE-Yokokawa, Tokyo) was introduced in our institute. These three cases of congenital tuberculosis showed periportal hypodensity, in addition to pulmonary infiltrate, mediastinal and abdominal lymphadenopathy on CT images. Early diagnosis of congenital tuberculosis is urgently needed, however, it is very difficult. Our findings suggested that clinical suspicion supplemented by careful imaging examinations may facilitate the early diagnosis of congenital tuberculosis, and the detection of periportal hypodensity may offer a new additive diagnostic option to congenital tuberculosis.

Adult↗
PubMed2003

Isoproterenol produces a rapid increase in sialidase activity in rat heart tissue and cardiomyocyte-derived H9c2 cells in culture.

The effects of isoproterenol on sialidase activity in rat cardiomyocytes were examined. Administration of isoproterenol to rats (0.2 or 2 mg/kg body weight) produced an increase in sialidase activity in total membrane fraction of heart tissue within 120 min (121+/-13% of the control at 120 min after administration of 0.2 mg isoproterenol/kg, n=5, P<0.05). Sialidase activity in cardiomyocyte-derived H9c2 cells was also increased by treatment with isoproterenol (10 microM) for 60 min. The effect of isoproterenol on sialidase activity was amplified by the addition of 3-isobutyl-1-methylxanthine (IBMX). Sialidase activity in H9c2 cells was elevated by treatment with dibutyryl cAMP plus IBMX without isoproterenol. The content of N-acetylneuraminic acid in cells decreased by 22% after treatment with isoproterenol plus IBMX. These results suggest that sialidase activity in rat cardiomyocytes is regulated by beta-adrenergic stimulators via a cAMP-dependent process. The increased activity of sialidase may account for the reduction of sialic acid content of cells.

1-Methyl-3-isobutylxanthine↗
PubMed2003

Altered antigenic disposition of peroxisomal urate oxidase in PEX5-defective Chinese hamster ovary cells.

Since Chinese hamster ovary (CHO) cells never express urate oxidase (UO), we tried to establish cell lines stably producing UO in order to elucidate the peroxisomal import process. The enzyme is a peroxisome targeting signal 1 (PTS1) protein harboring SKL motif at the carboxy-terminus [Biochem. Biophys. Res. Commun. 158 (1989) 991] and PEX5 protein (Pex5p) is supposed to be involved in the import process [Nat. Genet. 9 (1995) 115; J. Cell Biol. 130 (1995) 51]. We transfected a cDNA encoding rat UO into both wild type and PEX5-defective CHO cells to isolate each cell line stably producing the enzyme. While we examined the import process of UO in mutant cells, we noticed an interesting observation by using polyclonal antibody U1 or U2, which separately recognizes epitopes of UO. U1 antibody mainly interacts with epitopes in the amino-terminal region of UO. On the other hand, U2 antibody reacts with many epitopes distributed in the broad region of UO molecule. When UO produced in cultured cells was stained with U2 antibody, the enzyme was detected in peroxisomes of both wild type and PEX5-mutant cells. Whereas, U1 antibody stained the peroxisomal UO in wild type cells, but not in PEX5-mutant cells. These immunocytochemical observations suggest that the epitopes at the amino-terminal region of UO will be concealed in mutant cells. When the mutant cells were transfected with wild type PEX5 cDNA, U1 antibody came to react with UO in peroxisomes of mutant cells. The restoration indicates that the exposure of N-terminal epitopes of UO will depend upon the functional Pex5p. Immunoelectron microscopic observation showed that the peroxisomal import of UO was partially retarded in PEX5 mutant cells. The observation also supported the fact that UO was mainly localized in the peroxisomal matrix of wild type cells but in the membrane of mutant cells.

Animals↗