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Mitsuru Nakamura

Publications and source records attributed to Mitsuru Nakamura.

13 recordsLinked to original sources
PubMed2006

Strategy for simulation of CID spectra of N-linked oligosaccharides toward glycomics.

To develop a novel glycomics tool that can enable anyone to identify oligosaccharides very easily and quickly, we have recently constructed a library of observed multistage tandem mass (MS(n)) spectra for oligosaccharides. However, this approach requires the preparation of a large variety of structurally defined oligosaccharides. Therefore, simulation of the tandem mass spectrum for any given structure would be another powerful approach with which to improve the above method. By performing collision-induced dissociation (CID) experiments of sets of oligosaccharides complementarily labeled with (13)C(6)-D-galactose, we identified characteristic fragment patterns for each branch type of N-linked oligosaccharides. On the basis of these characteristic fragment patterns, we could simulate CID spectra for three isomeric oligosaccharides. In addition, we successfully demonstrated the identification of an oligosaccharide by matching its CID spectrum against the library of simulated tandem mass spectra. This strategy will be a useful tool for glycomics, as well as for approaches based on the library of observed MS(n) spectra.

Carbohydrate Conformation↗
PubMed2006

Discovery of Siglec-14, a novel sialic acid receptor undergoing concerted evolution with Siglec-5 in primates.

Immune receptors that show high mutual sequence similarity and have antagonizing signaling properties are called paired receptors, and are believed to fine-tune immune responses. Siglecs are sialic acid-recognizing receptors of the immunoglobulin (Ig) superfamily expressed on immune cells. Human Siglec-5, encoded by SIGLEC5 gene, has four extracellular Ig-like domains and a cytosolic inhibitory motif. We discovered human Siglec-14 with three Ig-like domains, encoded by the SIGLEC14 gene, adjacent to SIGLEC5. Human Siglec-14 has almost complete sequence identity with human Siglec-5 at the first two Ig-like domains, shows a glycan binding preference similar to that of human Siglec-5, and associates with the activating adapter protein DAP12. Thus, Siglec-14 and Siglec-5 appear to be the first glycan binding paired receptors. Near-complete sequence identity of the amino-terminal part of human Siglec-14 and Siglec-5 indicates partial gene conversion between SIGLEC14 and SIGLEC5. Remarkably, SIGLEC14 and SIGLEC5 in other primates also show evidence of gene conversions within each lineage. Evidently, balancing the interactions between Siglec-14, Siglec-5 and their common ligand(s) had selective advantage during the course of evolution. The "essential arginine" critical for sialic acid recognition in both Siglec-14 and Siglec-5 is present in humans but mutated in almost all great ape alleles.

Adaptor Proteins, Signal Transducing↗
PubMed2005

[Asystole during electroconvulsive therapy].

BACKGROUND: Asystole during electroconvulsive therapy (ECT) has been reported as an uncommon but fatal complication. But cardiac movement during electrical stimulation has not been well known. METHODS: The cardiac movements during electrical stimulation of fifty psychiatric patients treated by ECT under general anesthesia were observed utilizing thoracic echocardiography. Observations of 117 times were performed. Rate pressure products (RPP) immediately before stimulation and during 10 minutes after stimulation were calculated. Asystole was defined as absence of heartbeat for over 2 seconds. RESULTS: Asystoles were observed 57 times (48.7%). The heartbeat recovered immediately after stimulation in all asystole cases. RPP increased just after stimulation in all cases. Asystole cases had significantly greater variation of RPP than cases without aystole. (P = 0.0082). CONCLUSIONS: Electrical stimulation by ECT activates parasympathetic nervous system and convulsion by the stimulation activates sympathetic nervous system. As asystole case had good reactive automatic nervous system, asystole might have been provoked by the stimulation with a greater increase in RPP after the stimulation.

Anesthesia, General↗
PubMed2004

Not core 2 beta 1,6-N-acetylglucosaminyltransferase-2 or -3 but -1 regulates sialyl-Lewis x expression in human precursor B cells.

Sialyl-Lewis x (sLeX), one of the major selectin ligands, is expressed on T and B cells in a differentiation or activation stage-specific manner. We have demonstrated before that sLeX expression and core 2 beta 1,6-N-acetylglucosaminyltransferase (C2GnT) were simultaneously regulated during precursor B (pre-B) cell differentiation. Three C2GnT family genes, designated C2GnT-1, -2, and -3, were previously identified, but their roles have not been fully examined. In this study, we have investigated the roles of C2GnTs in the regulation of sLeX expression level during pre-B cell differentiation comparing with alpha 1,3fucosyltransferase-VII (FucT-VII) and alpha 2,3sialyltransferase-IV (ST3Gal-IV). Overexpression of not FucT-VII and ST3Gal-IV but C2GnT-1 blocked the down-regulation of sLeX expression by differentiation induction. Neither C2GnT-2 nor -3 but C2GnT-1 transcript was mainly expressed in B lineage cell lines and bone marrow-derived B lineage cells. Significant down-regulation of C2GnT-1 of the three C2GnTs was observed in KM3 cells during differentiation. The expression of C2GnT-1 correlated well to sLeX expression and differentiation stage. Furthermore, introduction of short interfering RNA against C2GnT-1 markedly reduced C2GnT-1 expression and resulted in down-regulation of sLeX expression. These results suggest that not the other glycosyltransferases but C2GnT-1 regulates sLeX expression level during differentiation of pre-B cells, providing the cells with substrate of sLeX structure biosynthesis.

Antibodies↗
PubMed2004

Approach for functional analysis of glycan using RNA interference.

The elucidation of the biological role of glycan is one of the most important issues to be resolved following the genome project. RNA interference is becoming an efficient reverse genetic tool for studying gene function in model organisms, including C.elegans and Drosophila melanogaster. Our molecular evolutionary study has shown that a prototype of glycosyltransferases, which synthesize a variety of glycan structures in the Golgi apparatus, was conserved between mammals and Drosophila. For analyses of the basic physiological functions of glycans, we established the Drosophila inducible RNAi knockdown system and applied it to one glycosyltransferase and one transporter, proteoglycan UDP-galactose: beta-xylose beta1,4galactosyltransferase I and the PAPS-transporter, respectively. If on the silencing of each gene induced ubiquitously under the control of a cytoplasmic actin promoter, the RNAi knockdown fly died, then the protein was indispensable for life. The expression of the target gene was disrupted specifically and the degree of interference was well correlated with the phenotype. The inducible RNAi knockdown fly obtained using the GAL4-UAS system will pave the way for the functional analysis of glycans.

Actins↗
PubMed2003

Suppression of ARG kinase activity by STI571 induces cell cycle arrest through up-regulation of CDK inhibitor p18/INK4c.

ARG is a tyrosine kinase closely related to ABL, which is oncogenic when fused to the transcriptional repressor ETV6 (ETS translocation variant 6). In this study, we investigated the growth-inhibitory effect of STI571 (signal transduction inhibitor number 571) on ETV6/ARG-expressing cells and its molecular mechanisms using HT93A, a cell line derived from a patient with AML-M3 carrying t(1;12). STI571 effectively suppressed overall tyrosyl phosphorylation of intracellular proteins including ETV6/ARG fusion protein, as well as the growth of HT93A cells with an IC(50) of 200 nM. The growth inhibition was primarily because of cell cycle arrest at G1 phase when cells were treated with 100 nM STI571 for 48 h, and apoptosis was induced after longer exposure (72 h) or by a higher dose (1000 nM). STI571 increased the amount of p18/INK4c after 2 h of culture, when the cell cycle pattern was not yet affected, but not that of other CDK inhibitors (CKI). p18/INK4c was more abundant in G1-enriched fractions than in S- and G2/M-enriched fractions of STI571-treated HT93A cells, suggesting that the upregulation of p18/INK4c expression correlates with the cell cycle arrest. Treatment of HT93A cells with antisense oligonucleotides against the Ink4c gene abrogated the growth inhibition by STI571. These results suggest that leukemogenesis by an aberrant ARG kinase involves the suppression of p18/INK4c, which is ubiquitously expressed and considered the major CKI in hematopoietic stem cells. STI571 can be an effective drug for the treatment of leukemias with deregulated ARG kinase activity.

Antineoplastic Agents↗
PubMed2003

Relationship between attention and arousal level in schizophrenia.

The purpose of the present paper was to clarify the link between the attention and arousal level that supports the basis of the cognitive dysfunction in schizophrenia, by investigating the relationship between the simple reaction time and the closed-eye eye movements in 30 patients with schizophrenia and 20 healthy controls. In terms of closed-eye eye movements during the simple reaction time test, healthy controls showed an increase of s-type (small and slow) eye movements after the end of the preparatory interval (PI) in both regular and irregular series, while the patients with schizophrenia, particularly those in whom the cross-over phenomenon was observed, showed no changes and maintained a hyperarousal level during the regular PI test. These results indicate that the patients with schizophrenia could not maintain appropriate attention during the burden tasks and their hyperarousal level persisted. It is therefore suggested that there is a close relationship between attentional deficit and hyperarousal among patients with schizophrenia.

Adult↗
PubMed2002

A novel I-branching beta-1,6-N-acetylglucosaminyltransferase involved in human blood group I antigen expression.

The human blood group i and I antigens are determined by linear and branched poly-N-acetyllactosamine structures, respectively. In erythrocytes, the fetal i antigen is converted to the adult I antigen by I-branching beta-1,6-N-acetylglucosaminyltransferase (IGnT) during development. Dysfunction of the I-branching enzyme may result in the adult i phenotype in erythrocytes. However, the I gene responsible for blood group I antigen has not been fully confirmed. We report here a novel human I-branching enzyme, designated IGnT3. The genes for IGnT1 (reported in 1993), IGnT2 (also presented in this study), and IGnT3 consist of 3 exons and share the second and third exons. Bone marrow cells preferentially expressed IGnT3 transcript. During erythroid differentiation using CD34(+) cells, IGnT3 was markedly up-regulated with concomitant decrease in IGnT1/2. Moreover, reticulocytes expressed the IGnT3 transcript, but IGnT1/2 was below detectable levels. By molecular genetic analyses of an adult i pedigree, individuals with the adult i phenotype were revealed to have heterozygous alleles with mutations in exon 2 (1006G>A; Gly336Arg) and exon 3 (1049G>A; Gly350Glu), respectively, of the IGnT3 gene. Chinese hamster ovary (CHO) cells transfected with each mutated IGnT3 cDNA failed to express I antigen. These findings indicate that the expression of the blood group I antigen in erythrocytes is determined by a novel IGnT3, not by IGnT1 or IGnT2.

Adult↗
PubMed2002

Cloning and characterization of a new human UDP-N-acetyl-alpha-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase, designated pp-GalNAc-T13, that is specifically expressed in neurons and synthesizes GalNAc alpha-serine/threonine antigen.

To date, 10 members of the UDP-N-acetyl-alpha-d-galactosamine:polypeptide N-acetylgalactosaminyltransferase (pp-GalNAc-T) family have been cloned and analyzed in human. In this study, we cloned and analyzed a novel human pp-GalNAc-T from an NT2 cell cDNA library, and we named it pp-GalNAc-T13. In amino acid sequences, pp-GalNAc-T13 was highly homologous, showing 84.3% identity, to pp-GalNAc-T1. Real time PCR analysis revealed pp-GalNAc-T13 to be highly and restrictively expressed in the brain and present at very low or undetectable levels in other tissues, in contrast to the ubiquitous expression of pp-GalNAc-T1. pp-GalNAc-T13 was abundantly expressed in all neuroblastoma cells examined and primary cultured neurons but not in glioblastoma cells and primary cultured astrocytes. pp-GalNAc-T13 exhibited much stronger activity to transfer GalNAc to mucin peptides, such as Muc5Ac and MUC7, than did pp-GalNAc-T1. In addition, pp-GalNAc-T13 differed in substrate specificity to pp-GalNAc-T1. pp-GalNAc-T13 was able to form a triplet Tn epitope, three consecutive GalNAc-Ser/Thr structures, on peptides encoded in syndecan-3, a proteoglycan expressed in neurons. pp-GalNAc-T13-deficient mice have been established in a previous work. Immunohistochemical study showed a remarkable decrease in Tn antigen expression in the cerebellum of the pp-GalNAc-T13 knockout mouse. pp-GalNAc-T13 would be a major enzyme responsible for the synthesis of O-glycan and specifically the Tn antigen epitope in neurons.

Amino Acid Sequence↗
PubMed2002

Apaf-1 is a mediator of E2F-1-induced apoptosis.

E2F-1 is capable of promoting both cell cycle progression and apoptosis. The latter is important for suppressing untoward expansion of proliferating cells. In this study, we investigated its underlying mechanisms. E2F-1-induced apoptosis was accompanied by caspase-9 activation and inhibited by a specific inhibitor of caspase-9 in K562 sublines overexpressing E2F-1. E2F-1 enhanced the expression of Apaf-1 without the cytosolic accumulation of cytochrome c. Apaf-1-deficient melanoma cell lines were resistant to E2F-1, indicating that Apaf-1 is an essential element of E2F-1-mediated apoptosis. Finally, we isolated the promoter region of the Apaf-1 gene and found a putative binding site for E2F. A chromatin immunoprecipitation assay revealed that E2F-1 bound to Apaf-1 promoter upon E2F-1 overexpression, suggesting that Apaf-1 is under transcriptional regulation of E2F-1. These data demonstrate a novel mechanism of apoptosis in which an increase in Apaf-1 levels results in direct activation of caspase-9 without mitochondrial damage, leading to the initiation of a caspase cascade.

Apoptosis↗