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Noriyuki Koibuchi

Publications and source records attributed to Noriyuki Koibuchi.

At least 19 recordsLinked to original sources
PubMed2007

Alteration of cerebellar neurotropin messenger ribonucleic acids and the lack of thyroid hormone receptor augmentation by staggerer-type retinoic acid receptor-related orphan receptor-alpha mutation.

The mutant mouse staggerer (sg) harbors a deletion within the gene encoding the retinoic acid receptor-related orphan receptor-alpha (RORalpha). Homozygotes show aberrant cerebellar development. However, the mechanisms responsible for the cerebellar defect are still poorly understood. In the present study, the involvement of neurotropins (NTs), including nerve growth factor, brain-derived neurotropic factor, NT-3 and NT-4/5, and their receptors, which play a crucial role in brain development, on the cerebellar defects of sg mice was studied by semiquantitative RT-PCR and in situ hybridization histochemistry. An evident alteration of these mRNA levels was observed in both heterozygotes and homozygotes. Such difference was most evident in the internal granule cell layer. Because the changes in NT expression as well as morphological alterations in sg cerebellum are similar to those in hypothyroid animals, the effect of mutant RORalpha (RORsg) on transcriptional regulation through the thyroid hormone (TH) response element or the ROR response element (RORE) was then studied. RORsg neither activated the transcription through RORE nor suppressed RORalpha-induced transcription, indicating that it does not function as a dominant negative inhibitor. On the other hand, although wild-type RORalpha augmented TH receptor (TR)alpha1/beta1-mediated transcription through various TH response elements, RORsg was not effective in augmenting TR action. These results suggest that the cerebellar defect of the sg mouse is partly caused by the altered expression of NTs and the lack of augmentation of TR-mediated transcription by RORalpha as well as the absence of RORalpha action through RORE.

Animals↗
PubMed2006

The endocrine disrupting chemical, diethylhexyl phthalate, activates MDR1 gene expression in human colon cancer LS174T cells.

Resistance to anticancer drugs is often mediated by the overexpression of P-glycoprotein encoded by the multi-drug resistance (MDR1) gene. The nuclear receptor, steroid and xenobiotic receptor (SXR), is one of the key transcriptional regulators of MDR1 gene expression. A variety of xenobiotics bind to SXR, and stimulate transcription on xenobiotic-response elements (XREs), located in the MDR1 gene promoter. Diethylhexyl phthalate (DEHP) is widely used as a plasticizer for polyvinyl chloride (PVC) medical devices. Previous studies have shown that a significant amount of DEHP leaches from PVC infusion bags and lines during interventions, such as total parenteral nutrition, blood transfusion, and cancer chemotherapy. Thus, the leaching of DEHP during parenteral chemotherapy for cancer patients may facilitate MDR1 expression in various tissues, including cancer cells, which may promote drug resistance. To examine such a hypothesis, the effect of DEHP on SXR-mediated transcription of the MDR1 gene was studied in the human colon adenocarcinoma-derived cell line, LS174T cells, which endogenously express SXR. DEHP increased the SXR-mediated transcription of the MDR1 gene in luciferase-reporter assays. The induction by DEHP was abrogated when a reporter plasmid containing mutated DR+4 motif in the XRE was used. In a mammalian two-hybrid assay, DEHP recruited steroid receptor co-activator-1 to the ligand-binding domain of SXR. Finally, using real-time reverse transcriptase-PCR, we showed that DEHP increased MDR1 gene expression in a dose-dependent manner. We conclude that DEHP is an inducer of the MDR1 gene in this cell line. As such, the leaching of DEHP from the PVC medical devices may influence the MDR1 expression, which may induce resistance to drugs in certain populations of cancer cells.

Blotting, Western↗
PubMed2005

The adrenal gland is a source of stress-induced circulating IL-18.

The present study compared plasma IL-18 levels between sham-operated and adrenalectomized mice following stress to investigate whether the adrenal gland contributes to the elevation of circulating IL-18 during stress. Two hours of stress provoked a robust, stressor-dependent, elevation of IL-18 mRNA and peptide in the adrenal gland in sham-operated mice. Consistently, levels of circulating mature IL-18 increased during stress and remained elevated for up to 6 h after stress. The stress-induced increase in circulating IL-18 was abolished by adrenalectomy. These findings demonstrate that the adrenal gland is required to achieve elevation of circulating IL-18 during stress.

Adrenal Glands↗
PubMed2005

The interaction of TRbeta1-N terminus with steroid receptor coactivator-1 (SRC-1) serves a full transcriptional activation function of SRC-1.

Steroid receptor coactivator-1 (SRC-1) plays a crucial role in nuclear receptor-mediated transcription including thyroid hormone receptor (TR)-dependent gene expression. Interaction of the TR-ligand binding domain and SRC-1 through LXXLL motifs is required for this action. However, potential interactions between the TRbeta1-N terminus (N) and SRC-1 have not been explored and thus are examined in this manuscript. Far-Western studies showed that protein construct containing TRbeta1-N + DNA binding domain (DBD) bound to nuclear receptor binding domain (NBD)-1 (amino acid residue, aa 595-780) of SRC-1 without ligand. Mammalian two-hybrid studies showed that NBD-1, as well as SRC-1 (aa 595-1440), bound to TRbeta1-N+DBD in the absence of ligand in CV-1 cells. However, NBD-2 (aa 1237-1440) did not bind to this protein. Glutathione-S-transferase pull-down studies showed that TRbeta1-N (aa 1-105) bound to the broad region of SRC-1-C terminus. Expression vectors encoding a series of truncations and/or point mutations of TRbeta1 were used in transient transfection-based reporter assays in CV-1 cells. N-terminal truncated TRbeta1 (DeltaN-TRbeta1) showed lower activity than that of wild-type in both artificial F2-thyroid hormone response element and native malic enzyme response element. These results suggest that there is the interaction between N terminus of TRbeta1 and SRC-1, which may serve a full activation of SRC-1, together with activation function-2 on TRbeta1-mediated transcription.

Animals↗
PubMed2005

Low dose hydroxylated PCB induces c-Jun expression in PC12 cells.

Polychlorinated biphenyls (PCBs) are known as environmental pollutants that may cause adverse health problems. Recently, accumulating evidence shows that PCBs express neurotoxicity through alteration of gene expression and signal transduction. On the other hand, c-Jun, a component of AP-1, is likely to coordinate transcription programs in response to various extracellular signals. However, little is known about the effects of PCBs on c-Jun expression. Here we investigated the expression of c-Jun in response to PCB. PC12 cells were incubated with hydroxylated PCB (4(OH)-2',3,3',4',5'-penta chlorobiphenyl, OH-PCB) at a final concentration from 10(-8) to 10(-5)M. The level of c-Jun expression was increased by OH-PCB at relatively low-dose; concentration of OH-PCB at 10(-8)M and 10(-7)M produced a 2.4- and 3.5-fold increase of c-Jun expression in respectively, compared with the values without OH-PCB treatment. Thyroid hormone (T3) did not induce such c-Jun expression, indicating that the effect of OH-PCB is not mediated through thyroid hormone signaling pathway. OH-PCB also enhanced phosphorylation of c-Jun NH2-terminal kinases. To determine whether the activation of Ca2+ channel is involved in the OH-PCB-induced c-Jun expression, we examined it using a L-type voltage-gated Ca2+ channel blocker nimodipine. Nimodipine partially inhibited OH-PCB-induced c-Jun expression by 50%. Moreover, Na+ channel antagonist tetrodotoxin inhibited OH-PCB-induced c-Jun expression completely. Taken together, our results indicate that exposure to OH-PCB induces c-Jun expression, and the response may be triggered by depolarization of a plasma membrane via Na+ influx, followed by Ca2+ influx partially through voltage-gated Ca2+ channels.

Animals↗
PubMed2005

Neuronal expression of nuclear transcription factor MafG in the rat medulla oblongata after baroreceptor stimulation.

The medulla oblongata is the site of central baroreceptive neurons in mammals. These neurons express specific basic-leucine zipper transcription factors (bZIP) after baroreceptor stimulation. Previously we showed that activation of baroreceptors induced expression of nuclear transcription factors c-Fos and FosB in central baroreceptive neurons. Here we studied the effects of baroreceptor stimulation on induction of MafG, a member of small Maf protein family that functions as dimeric partners for various bZIP transcription factors by forming transcription-regulating complexes, in the rat medulla oblongata. To determine whether gene expression of MafG is induced by stimulation of arterial baroreceptors, we examined the expression of its mRNA by semi-quantitative reverse transcription-PCR method and its gene product by immunohistochemistry. We found that the number of MafG transcripts increased significantly in the medulla oblongata after baroreceptor stimulation. MafG-immunoreactive neurons were distributed in the nucleus tractus solitarii, the dorsal motor nucleus of the vagus nerve, the ambiguous nucleus and the ventrolateral medulla. The numbers of MafG-immunoreactive neurons in these nuclei were significantly greater in test rats than in saline-injected control rats. We also found approximately 20% of MafG-immunoreactive neurons coexpress FosB after baroreceptor stimulation. Our results suggest that MafG cooperates with FosB to play critical roles as an immediate early gene in the signal transduction of cardiovascular regulation mediated by baroreceptive signals in the medulla oblongata.

Animals↗
PubMed2005

Monitoring synaptogenesis in the developing mouse cerebellum with an original oligonucleotide microarray.

Use of DNA microarrays in neuroscience have been limited to rough screening purposes, mainly because the reliability and sensitivity of available arrays are not high enough. Because only a few hundred to one thousand genes are usually found to change expression levels in most experiments, we attempted to develop a more quantitative array by the following strategies: 1) limit the genes to those relevant to the experimental system, 2) design oligonucleotide probes of specified molecular properties so that more stringent hybridization conditions can be employed, 3) place six spots per probe on one slide and use multiple normalization genes, and 4) use a new type of gold-coated slide with higher S/N ratio. Genes involved in the construction and functioning of the synapse were selected from the literature as well as experimentally by comparing cerebella from hypothyroid and control mice at postnatal day 15 (P15). Although the number of genes covered was not yet large (172 genes), the custom array "Synaptoarray" thus constructed was capable of detecting +/-20% difference in gene expression ratios. Analysis of the postnatal development of the mouse cerebellum by using Synaptoarray demonstrated a general expression pattern with a peak at P7, followed by a decline at P15 and a partial recovery after P21. P10 clearly marked the end of the initial growth stage and a major transcriptional turning point in this system. This result suggests that such a custom array should be useful in monitoring perturbations to the normal developmental program.

Animals↗
PubMed2005

Functional characterization of JMJD2A, a histone deacetylase- and retinoblastoma-binding protein.

To effectively direct targeted repression, the class I histone deacetylases (HDACs) associate with many important regulatory proteins. In this paper we describe the molecular characterization of a member of the Jumonji domain 2 (JMJD2) family of proteins, and demonstrate its binding to both class I HDACs and the retinoblastoma protein (pRb). JMJD2 proteins are characterized by the presence of two leukemia-associated protein/plant homeodomain (LAP/PHD) zinc fingers, one JmjN, one JmjC (containing an internal retinoblastoma-binding protein 2 (RBBP2)-like sequence), and two Tudor domains. The first member of this group, JMJD2A, is widely expressed in human tissues and cell lines, and high endogenous expression of JMJD2A mRNA was found in several cell types, including human T-cell lymphotropic virus 1 (HTLV-1)-infected cell lines. JMJD2A and JMJD2B exhibit cell type-specific responses to the HDAC inhibitor trichostatin A. We show that the JMJD2A protein associates in vivo with pRb and class I HDACs, and mediates repression of E2F-regulated promoters. In HTLV-1 virus-infected cells, we find that JMJD2A binds to the viral Tax protein. Antibodies to JMJD2A recognize the native protein but also a half-sized protein fragment, the latter up-regulated in THP-1 cells during the G(2)/M phase of the cell cycle. The ability of JMJD2A to associate with pRb and HDACs and potentiate pRb-mediated repression of E2F-regulated promoters implies an important role for this protein in cell proliferation and oncogenesis.

Amino Acid Sequence↗
PubMed2005

Synovial sarcoma translocation (SYT) encodes a nuclear receptor coactivator.

We previously cloned and characterized a novel RNA-binding motif-containing coactivator, named coactivator activator (CoAA), as a thyroid hormone receptor-binding protein-interacting protein using a Sos-Ras yeast two-hybrid screening system. A database search revealed that CoAA is identical with synovial sarcoma translocation (SYT)-interacting protein. Thus, we hypothesized that SYT could also function as a coactivator. Subsequently, we isolated a cDNA encoding a larger isoform of SYT, SYT-long (SYT-L), from the brain and liver total RNA using RT-PCR. SYT-L possesses an additional 31 amino acids in its C terminus compared with SYT, suggesting that these two SYT isoforms may be expressed from two mRNAs produced by alternative splicing of a transcript from a single gene. By Northern blot analysis, we found that SYT-L mRNA is expressed in several human embryonic tissues, such as the brain, liver, and kidney. However, we could not detect SYT-L in adult tissues. Glutathione-S-transferase pull-down studies showed that SYT binds to the C-terminus of CoAA, but not to the coactivator modulator. Both isoforms of SYT function as transcriptional coactivators of nuclear hormone receptors in a ligand- and dose-dependent manner in CV-1, COS-1, and JEG-3 cells. However, the pattern of transactivation was different between SYT and SYT-L among these cells. SYT synergistically activates transcription with CoAA. In addition, SYT activates transcription through activator protein-1, suggesting that SYT may function as a general coactivator. These results indicate that SYT activates transcription, possibly through CoAA, to interact with the histone acetyltransferase complex.

Age Factors↗
PubMed2005

Extracellular acidification enhances DNA binding activity of MafG-FosB heterodimer.

Cells are quite sensitive to a change of the extracellular pH and respond to it through detection of the H+/HCO3- level in extracellular fluid. However, little is known about molecular details induced by acidosis, such as intracellular pathways and gene expression. Here we describe properties of gene expression, protein interaction, and DNA binding activity of basic region leucine zipper (bZIP) transcription factor Maf and FosB during extracellular acidification. When cells were incubated with low pH medium, the expressions of small Maf proteins (MafG, MafK, and MafF) and FosB were clearly increased in an extracellular pH-dependent manner and expressed transiently with a peak after 1-2 h after stimulation. Immunofluorescence and protein binding studies indicated that MafG was partially co-localized with FosB in the nucleus and MafG can form heterodimers with FosB at extracellular pH 7.40. Moreover, we found that MafG-FosB complexes are able to bind to AP-1 consensus sequence, TGACTCA. To investigate whether extracellular acidification influences to dimerization and DNA binding activity of MafG and FosB, extracellular pH of cultured cells was decreased from 7.40 to 6.80. The decrease in extracellular pH led to enhanced dimerization of MafG with FosB leading to augmentation of the DNA binding activity of the heterodimer to AP-1 consensus sequence. Moreover, extracellular acidification induces mRNA expression of matrix metalloproteinase-1, one of the genes that are regulated by AP-1. These results suggest that MafG-FosB complexes are involved in transcriptional regulation in response to extracellular acidification.

Acids↗
PubMed2005

Polychlorinated biphenyl (PCB) alters acid-sensitivity of cultured neurons derived from the medulla oblongata.

Polychlorinated biphenyls (PCBs) are known as environmental pollutants that may cause adverse health problems. However, little is known about the effects of PCBs on acid-sensitive neurons of the medulla oblongata, which regulate respiration. Therefore, the present study was designed to examine whether PCB alters acid-sensitivity of cultured neurons derived from the rat medulla oblongata. When extracellular pH was shifted from 7.4 to 7.0, acid-sensitive neurons showed depolarization, which was measured by voltage-sensitive fluorescent dye. Exposure to PCB (Aroclor 1254) decreased the amplitude of depolarization in low pH and increased the resting membrane potential in a dose-dependent manner. Taken together, our results indicate that PCB potentially influences acid-sensitivity through alteration of the membrane potential of acid-sensitive neurons, which could affect the regulation of respiration.

Animals↗
PubMed2005

Molecular responses to acidosis of central chemosensitive neurons in brain.

Significant advances have been made in understanding how neurons sense and respond to acidosis at the cellular level. Decrease in pH of the cerebrospinal fluid followed by hypercapnia (increased arterial CO2) is monitored by the chemosensory neurons of the medulla oblongata. Then the intracellular signalling pathways are activated to regulate specific gene expression, which leads to a hyperventilatory response. However, little is known about molecular details of such cellular responses. Recent studies have identified several transcription factors such as c-Jun, Fos and small Maf proteins that may play critical roles in the brain adaptation to hypercapnia. Hypercapnic stimulation also activates c-Jun NH2-terminal kinase (JNK) cascade via influx of extracellular Ca2+ through voltage-gated Ca2+ channels. In addition, several transmembrane proteins including Rhombex-29 (rhombencephalic expression protein-29 kDa) and Past-A (proton-associated sugar transporter-A) have been implicated in regulation of H+ sensitivity and brain acidosis-mediated energy metabolism, respectively. This review discusses current knowledge on the signalling mechanisms and molecular basis of neuronal adaptation during acidosis.

Acidosis↗
PubMed2005

Postnatal changes of steroid receptor coactivator-1 immunoreactivity in rat cerebellar cortex.

Steroid receptor coactivator-1 (SRC-1) interacts with nuclear hormone receptors (NRs) to mediate their action in a ligand-dependent manner. Among such ligands, thyroid hormone (TH) is particularly crucial for brain development. The expression of many TH target genes is regulated by TH only for a limited critical period, although TH receptor (TR) expression is not greatly altered after such period. To alter TH sensitivity, other factors may be involved. We thus examined the changes in SRC-1 expression during postnatal development in the rat cerebellum by immunohistochemistry and Western blotting. Strong SRC-1 immunoreactivity (IR) was constantly seen in Purkinje cell from postnatal days (P) 2 to P30. SRC-1 IR was also constantly observed in the internal granule cell layer. However, it was negative in the external granule cell layer at P2 and P7, whereas a weak IR was detected in the premigratory zone at P15. SRC-1 IR was detected in the molecular layer after P15. These results indicate that although TR is almost ubiquitously expressed in the developing cerebellum, the TH sensitivity could vary in each subset of cells. By Western blotting, SRC-1 protein level was greatest at P15, at which time TH action may be obvious. Taken together, the differential expression of SRC-1 may be crucial in mediating TH action during cerebellar development.

Animals↗
PubMed2005

Retinoid-related receptor (ROR) alpha mRNA expression is altered in the brain of male mice lacking all ligand-binding thyroid hormone receptor (TR) isoforms.

In the vertebrate brain, the thalamus serves as a relay and integration station for diverse neuronal information en route from the periphery to the cortex. Deficiency of TH during development results in severe cerebral abnormalities similar to those seen in the mouse when the retinoic acid receptor (ROR)alpha gene is disrupted. To investigate the effect of the thyroid hormone receptors (TRs) on RORalpha gene expression, we used intact male mice, in which the genes encoding the alpha and beta TRs have been deleted. In situ hybridization for RORalpha mRNA revealed that this gene is expressed in specific areas of the brain including the thalamus, pons, cerebellum, cortex, and hippocampus. Our quantitative data showed differences in RORalpha mRNA expression in different subthalamic nuclei between wild-type and knock-out mice. For example, the centromedial nucleus of the thalamus, which plays a role in mediating nociceptive and visceral information from the brainstem to the basal ganglia and cortical regions, has less expression of RORalpha mRNA in the knockout mice (-37%) compared to the wild-type controls. Also, in the dorsal geniculate (+72%) and lateral posterior nuclei (+58%) we found more RORalpha mRNA in dKO as compared to dWT animals. Such differences in RORalpha mRNA expression may play a role in the behavioral alterations resulting from congenital hypothyroidism.

Animals↗
PubMed2005

Differential expression of p160 steroid receptor coactivators in the rat testis and epididymis.

OBJECTIVE: Androgens are critical for the development and maintenance of male sexual characteristics. Their action is mediated through the androgen receptor (AR). Ligand-bound AR interacts with coactivator proteins that mediate transcriptional activation. Such coactivators include three members of the 160 kDa proteins (p160s): SRC-1, TIF2/GRIP1, and p/CIP/RAC3/ACTR/AIB1/TRAM-1. The aim of this study was to investigate the expression of the three p160 coactivators and their association with AR in testis and epididymis. METHODS: We determined the localization of these three p160 coactivators in immature and mature rat testis, and epididymis by immunohistochemistry using the specific monoclonal antibodies. We also performed double immunofluorescence staining to examine whether p160s are colocalized with AR in these tissues. RESULTS: In seminiferous tubules of mature rat testis, SRC-1 and TRAM-1 immunoreactivity was found predominantly in spermatogonia and spermatocytes. In contrast, TIF2 was expressed predominantly in Sertoli cells. AR was coexpressed with TIF2 in this cell type. In immature rat testis, however, all three coactivators were expressed in both germ cells and Sertoli cells. In the epididymis, SRC-1 and TIF2 immunoreactivities were localized in nuclei of epithelial cells. However, TRAM-1 immunostaining was observed in the luminal portion of the cytoplasm with greater intensity than in the nucleus, especially in the caput epididymidis. CONCLUSIONS: The cell-type-specific expression of p160 coactivators suggests specific roles in male reproductive organs. Further, the strong cytoplasmic localization of TRAM-1 protein in epithelial cells of epididymis suggests that TRAM-1 may have additional role(s) in transcriptional regulation.

Aging↗