Details of a Researcher - Tomita, Masaru

Papers - Tomita, Masaru

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Metabolic regulation analysis of wild-type and arcA mutant Escherichia coli under nitrate conditions using different levels of omics data

Toya, Y., Nakahigashi, K., Tomita, M., and Shimizu, K.

Molecular BioSystems (Molecular BioSystems) 8 ( 10 ) 2593-604. - 2604 2012

Research paper (scientific journal), Joint Work, Accepted, ISSN 1742206X

It is of practical interest to investigate the effect of nitrates on bacterial metabolic regulation of both fermentation and energy generation, as compared to aerobic and anaerobic growth without nitrates. Although gene level regulation has previously been studied for nitrate assimilation, it is important to understand this metabolic regulation in terms of global regulators. In the present study, therefore, we measured gene expression using DNA microarrays, intracellular metabolite concentrations using CE-TOFMS, and metabolic fluxes using the <sup>13</sup>C-labeling technique for wild-type E. coli and the ΔarcA (a global regulatory gene for anoxic response control, ArcA) mutant to compare the metabolic state under nitrate conditions to that under aerobic and anaerobic conditions without nitrates in continuous culture conditions at a dilution rate of 0.2 h<sup>-1</sup>. In wild-type, although the measured metabolite concentrations changed very little among the three culture conditions, the TCA cycle and the pentose phosphate pathway fluxes were significantly different under each condition. These results suggested that the ATP production rate was 29% higher under nitrate conditions than that under anaerobic conditions, whereas the ATP production rate was 10% lower than that under aerobic conditions. The flux changes in the TCA cycle were caused by changes in control at the gene expression level. In ΔarcA mutant, the TCA cycle flux was significantly increased (4.4 times higher than that of the wild type) under nitrate conditions. Similarly, the intracellular ATP/ADP ratio increased approximately two-fold compared to that of the wild-type strain. © 2012 The Royal Society of Chemistry.

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Temporal profiling of lapatinib-suppressed phosphorylation signals inEGFR/HER2 pathways

Imami, K., Sugiyama, N., Imamura, H., Wakabayashi, M., Tomita, M., Taniguchi, M., Ueno, T., Toi, M. and Ishihama, Y.

Mol Cell Proteomics (Molecular and Cellular Proteomics) 11 ( 12 ) [Epub ahead of print] - 1757 2012

Research paper (scientific journal), Joint Work, Accepted, ISSN 15359476

Lapatinib is a clinically potent kinase inhibitor for breast cancer patients because of its outstanding selectivity for epidermal growth factor receptor (EGFR) and EGFR2 (also known as HER2). However, there is only limited information about the in vivo effects of lapatinib on EGFR/HER2 and downstream signaling targets. Here, we profiled the lapatinib-induced time- and dose-dependent phosphorylation dynamics in SKBR3 breast cancer cells by means of quantitative phosphoproteomics. Among 4953 identified phosphopeptides from 1548 proteins, a small proportion (5-7%) was regulated at least twofold by 1-10 μM lapatinib. We obtained a comprehensive phosphorylation map of 21 sites on EGFR/HER2, including nine novel sites on HER2. Among them, serine/threonine phosphosites located in a small region of HER2 (amino acid residues 1049-1083) were up-regulated by the drug, whereas all other sites were down-regulated. We show that cAMP-dependent protein kinase is involved in phosphorylation of this particular region of HER2 and regulates HER2 tyrosine kinase activity. Computational analyses of quantitative phosphoproteome data indicated for the first time that protein-protein networks related to cytoskeletal organization and transcriptional/translational regulation, such as RNP complexes (i.e. hnRNP, snRNP, telomerase, ribosome), are linked to EGFR/HER2 signaling networks. To our knowledge, this is the first report to profile the temporal response of phosphorylation dynamics to a kinase inhibitor. The results provide new insights into EGFR/HER2 regulation through region-specific phosphorylation, as well as a global view of the cellular signaling networks associated with the anti-breast cancer action of lapatinib. © 2012 by The American Society for Biochemistry and Molecular Biology, Inc.

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Sheathless capillary electrophoresis-mass spectrometry with a high- sensitivity porous sprayer for cationic metabolome analysis

Hirayama, A., Tomita, M. and Soga, T.

Analyst (Analyst) 137 ( 21 ) 5026-5033 - 5033 2012

Research paper (scientific journal), Joint Work, Accepted, ISSN 00032654

Sheath-flow capillary electrophoresis-mass spectrometry (CE-MS) has emerged as a new tool for comprehensive analysis of charged metabolites. However, it needs to be more sensitive. Here, we report a sheathless capillary electrophoresis-electrospray ionization-mass spectrometry method for cationic metabolome analysis. This system used a high-sensitivity porous sprayer interface and 10% (v/v) acetic acid as the background electrolyte (BGE). Under optimized conditions, 53 cationic metabolites, including amino acids and their derivatives, amines, nucleic acids and small peptides, were successfully separated and selectively detected with a time-of-flight mass spectrometer. At a signal-to-noise ratio of three, the concentration detection limits for these compounds were between 0.004 and 0.8 μmol L-1 (amount detection limit, 0.01 to 2 fmol) with pressure injection at 20.7 kPa for 5 s (2.6 nL). Compared with conventional sheath-flow CE-MS, the detection limit of the present method was increased more than 5-fold for 21 (40%) of the compounds detected. When the method was applied to the analysis of cationic metabolites obtained from human urine, there was a 10-fold increase in the number of detected peaks compared with conventional methods. More than 180 successive runs could be conducted without any problems, and only the BGE needed to be changed. © 2012 The Royal Society of Chemistry.

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Pilot Study of Changes in Salivary Metabolic Profiles Induced by Template Therapy

Tanaka, S., Taga, H., Maehara, K., Kaneshima, A., Machino, M., Onuma, H., Kaneko, M., Sakagami, H., Sugimoto, M., Soga, T. and Tomita, M.

InVivo. (In Vivo) 26 ( 6 ) 1015-1020 - 1020 2012

Research paper (scientific journal), Joint Work, Accepted, ISSN 0258851X

Background: Occlusal raising method (so-called 'Template therapy') has been reported to alleviate various diseases and symptoms, but the underlying mechanism is not clear. We searched the low-molecular weight metabolite(s) in the saliva, the concentration of which is significantly changed by the template therapy. Materials and Methods: One female patient with headache underwent the template therapy for 12 days, and her total saliva was subjected to non-targeted analysis using capillary electrophoresis time-of-flight mass spectrometry (CE-TOF-MS). Results: One hundred and thirteen substances were identified in the saliva. Glycine was the most abundant amino acid in the saliva, followed by alanine, serine and proline. After the start of the template therapy, her headache was alleviated, accompanied by a significant (p=0.042) increase of salivary concentration of glycine, as compared with total amino acids whereas that of other amino acids was not significantly changed. In the metabolomics profile, salivary concentration of large number of metabolites as compared with total metabolite concentration decreased, including N-acetylneuraminate (p=0.025) and p-hydroxyphenylacetate (p=0.039). Conclusion: This pilot study demonstrated, to our knowledge for the first time, that only glycine exhibited unique changes among total metabolites, suggesting its significant role in template therapy.

Is central dogma a global property of cellular information flow?

Piras, V., Tomita, M. and Selvarajoo, K

Front. Physiol. (Frontiers in Physiology) 3 439 2012

Research paper (scientific journal), Joint Work, Accepted

The central dogma of molecular biology has come under scrutiny in recent years. Here, we reviewed high-throughput mRNA and protein expression data of Escherichia coli, Saccharomyces cerevisiae, and several mammalian cells. At both single cell and population scales, the statistical comparisons between the entire transcriptomes and proteomes show clear correlation structures. In contrast, the pair-wise correlations of single transcripts to proteins show nullity. These data suggest that the organizing structure guiding cellular processes is observed at omics-wide scale, and not at single molecule level. The central dogma, thus, globally emerges as an average integrated flow of cellular information. © 2012 Piras, Tomita and Selvarajoo.

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Metabolomics: A New Omics Technology for Traditional Herbal Medicine Analysis

Iino, K., Sugimoto, M., Soga, T. and Tomita, M.

Chinese Medicine: Acupuncture, Herbal Medicine and Therapies 45-55 2012

Research paper (scientific journal), Joint Work, Accepted

Metabolic profiling reveals new serum biomarkers for differentiating diabetic nephropathy

Hirayama, A., Nakashima, E., Sugimotoa, M., Akiyama, S., Sato, W., Maruyama, S., Matsuo, S., Tomita, M., Yuzawa, Y. and Soga, T.

Anal Bioanal Chem (Analytical and Bioanalytical Chemistry) 404 ( 10 ) 3101-9 - 3109 2012

Research paper (scientific journal), Joint Work, Accepted, ISSN 16182642

Capillary electrophoresis coupled with time-offlight mass spectrometry was used to explore new serum biomarkers with high sensitivity and specificity for diabetic nephropathy (DN) diagnosis, through comprehensive analysis of serum metabolites with 78 diabetic patients. Multivariate analyses were used for identification of marker candidates and development of discriminative models. Of the 289 profiled metabolites, orthogonal partial leastsquares discriminant analysis identified 19 metabolites that could distinguish between DN with macroalbuminuria and diabetic patients without albuminuria. These identified metabolites included creatinine, aspartic acid, γ-butyrobetaine, citrulline, symmetric dimethylarginine (SDMA), kynurenine, azelaic acid, and galactaric acid. Significant correlations between all these metabolites and urinary albumin-to-creatinine ratios (p<0.009, Spearman's rank test) were observed. When five metabolites (including γ-butyrobetaine, SDMA, azelaic acid and two unknowns) were selected from 19 metabolites and applied for multiple logistic regressionmodel, AUC value for diagnosing DN was 0.927 using the whole dataset, and 0.880 in a cross-validation test. In addition, when four known metabolites (aspartic acid, SDMA, azelaic acid and galactaric acid) were applied, the resulting AUC was still high at 0.844 with the whole dataset and 0.792 with cross-validation. Combination of serum metabolomics with multivariate analyses enabled accurate discrimination of DN patients. The results suggest that capillary electrophoresis-mass spectrometry based metabolome analysis could be used for DN diagnosis. © Springer-Verlag 2012.

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A simple method to provide a shuttling plasmid for delivery to other host ascertained by prolonged stability of extracellular plasmid DNA released from Escherichia coli K12 endA mutant, deficient in major endonuclease

Itaya, M.,　Kawata, Y., Sato, M., Tomita, M. and Nakahigashi, K.

J. Biochem. (Journal of Biochemistry) 152 ( 6 ) 501–504 - 504 2012

Research paper (scientific journal), Joint Work, Accepted, ISSN 0021924X

Escherichia coli lyses by lambda phage propagation. Circular plasmid DNA was present during E. coli lysis as an extracellular plasmid DNA (excpDNA) that was stable enough to transform coexisting competent Bacillus subtilis cells. Detailed investigations unveiled that excpDNA is transient in both quality and quantity, with stability lasting no more than several hours. A survey using E. coli lambda lysogens with various genetic backgrounds demonstrated that the loss of Endonuclease I (ΔendA::kan) conferred extraordinary stability upon excpDNA for as long as 48 h. Studies on endA mutants suggested that excpDNA remained localized in cell debris, in contrast to E. coli genome DNA, which diffused into medium at an early point in lysis. Lambda lysogens constructed on endA recA mutants are presented for potential pipelines in delivery to other competent proficient microbes. © 2012 The Authors.

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A medium-chain fatty acid as an alternative energy source in mouse preimplantation development

Yamada, M., Takanashi, K., Hamatani, T., Hirayama, A., Akutsu, H., Fukunaga, T., Ogawa, S., Sugawara, K., Shinoda, K., Soga, T., Umezawa, A., Kuji, N., Yoshimura, Y. and Tomita, M.

Sci Rep. (Scientific Reports) 2 930 2012

Research paper (scientific journal), Joint Work, Accepted

To further optimize the culturing of preimplantation embryos, we undertook metabolomic analysis of relevant culture media using capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS). We detected 28 metabolites: 23 embryo-excreted metabolites including 16 amino acids and 5 media-derived metabolites (e.g., octanoate, a medium-chain fatty acid (MCFA)). Due to the lack of information on MCFAs in mammalian preimplantation development, this study examined octanoate as a potential alternative energy source for preimplantation embryo cultures. No embryos survived in culture media lacking FAs, pyruvate, and glucose, but supplementation of octanoate rescued the embryonic development. Immunoblotting showed significant expression of acyl-CoA dehydrogenase and hydroxyacyl-CoA dehydrogenase, important enzymes for β-oxidation of MCFAs, in preimplantation embryo. Furthermore, CE-TOFMS traced [1-13 C 8[ octanoate added to the culture media into intermediate metabolites of the TCA cycle via β-oxidation in mitochondria. These results are the first demonstration that octanoate could provide an efficient alternative energy source throughout preimplantation development.

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Light Microscopy and Phylogenetic Analyses of Chlamydomonas Species (Volvocales, Chlorophyceae). : I. Chlamydomonas pseudomacrostigma and Chlamydomonas media

Nakada, T., Nozaki, H. and Tomita, M.

Acta phytotaxonomica et geobotanica 62:69-78 62 69 - 78 2012

Joint Work

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Serial assembly of Thermus megaplasmid DNA in the genome of Bacillus subtilis 168: a BAC-based domino method applied to DNA with a high GC content

Ohtani, N., Hasegawa, M., Sato, M., Tomita, M., Kaneko, S. and Itaya, M.

Biotechnol J. (Biotechnology Journal) 7 ( 7 ) 867 - 76 2012

Joint Work, Accepted, ISSN 18606768

Bacillus subtilis is the only bacterium-based host able to clone giant DNA above 1000 kbp. DNA previously handled by this host was limited to that with GC content similar to or lower than that of the B. subtilis genome. To expand the target DNA range to higher GC content, we tried to clone a pTT27 megaplasmid (257 kbp, 69% of G+C) from Thermus thermophilus. To facilitate the reconstruction process, we subcloned pTT27 in a bacterial artificial chromosome (BAC) vector of Escherichia coli. Owing to the ability of BAC to carry around 100 kbp DNA, only 4 clones were needed to cover the pTT27 and conduct step-by-step assembly in the B. subtilis genome. The full length of 257 kbp was reconstructed through 3 intermediary lengths (108, 153, and 226 kbp), despite an unexpected difficulty in the maintenance of DNA >200 kbp. Retrieval of these four pTT27 segments from the B. subtilis genome by genetic transfer to a plasmid pLS20 was attempted. A stable plasmid clone was obtained only for the 108 and 153 kbp intermediates. The B. subtilis genome was demonstrated to accommodate large DNA with a high GC content, but may be restricted to less than 200 kbp by unidentified mechanisms. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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Metabolomic profiling rationalized pyruvate efficacy in cybrid cells harboring MELAS mitochondrial DNA mutations.

Kami, K., Fujita, Y., Igarashi, S., Koike, S., Sugawara, S., Ikeda, S., Sato, N., Ito, M., Tanaka, M., Tomita, M. and Soga, T.

Mitochondrion. (Mitochondrion) 12 ( 6 ) 644 - 653 2012

Accepted, ISSN 15677249

Pyruvate treatment was found to alleviate clinical symptoms of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome and is highly promising therapeutic. Using capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS), we measured time-changes of 161 intracellular and 85 medium metabolites to elucidate metabolic effects of pyruvate treatment on cybrid human 143B osteosarcoma cells harboring normal (2SA) and MELAS mutant (2SD) mitochondria. The results demonstrated dramatic and sustainable effects of pyruvate administration on the energy metabolism of 2SD cells, corroborating pyruvate as a metabolically rational treatment regimen for improving symptoms associated with MELAS and possibly other mitochondrial diseases. © 2012 Elsevier B.V. and Mitochondria Research Society.

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Computational assessment of insulin secretion and insulin sensitivity from 2-h oral glucose tolerance tests for clinical use for type 2 diabetes

Seike, Masayoshi; Saitou, Takeo; Kouchi, Yasuhiro; Ohara, Takeshi; Matsuhisa, Munehide; Sakaguchi, Kazuhiko; Tomita, Koji; Kosugi, Keisuke; Kashiwagi, Atsunori; Kasuga, Masato; Tomita, Masaru; Naito, Yasuhiro; Nakajima, Hiromu

Journal of Physiological Sciences (Journal of Physiological Sciences) 61 ( 4 ) 321-330 - 330 2011.07

Research paper (scientific journal), Joint Work, ISSN 18806546

In type 2 diabetes mellitus, glucose homeostasis is tightly maintained through insulin secretion and insulin sensitivity. Therefore, finding an accurate method to assess insulin secretion and sensitivity using clinically available data would enhance the quality of diabetic medical care. In an effort to find such a method, we developed a computational approach to derive indices of these factors using a 2-h oral glucose tolerance test (OGTT). To evaluate our method, clinical data from subjects who received an OGTT and a glucose clamp test were examined. Our insulin secretion index was significantly correlated with an analogous index obtained from a hyperglycemic clamp test (r = 0.90, n = 46, p < 0.001). Our insulin sensitivity index sensitivity was also significantly correlated with an analogous index obtained from a hyperinsulinemic-euglycemic clamp test (r = 0.56, n = 79, p < 0.001). These results suggest that our method can potentially provide an accurate and convenient tool toward improving the management of diabetes in clinical practice by assessing insulin secretion and insulin sensitivity. © 2011 The Author(s).

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A novel mechanism regulates H2S and SO2 production in Saccharomyces cerevisiae

Yoshida S., Imoto J., Minato T., Oouchi R., Kamada Y., Tomita M., Soga T., Yoshimoto H.

Yeast 28 ( 2 ) 109 - 121 2011.02

ISSN 0749503X

Sulfite (SO2) plays an important role in flavour stability in alcoholic beverages, whereas hydrogen sulfide (H2S) has an undesirable aroma. To discover the cellular processes that control SO2 and H2S production, we screened a library of Saccharomyces cerevisiae deletion mutants. Deletion of 12 genes led to increased H2S productivity. Ten of these genes are known to be involved in sulfur-containing amino acid metabolism, whereas UBI4 functions in the ubiquitin-proteasome system and SKP2 encodes an F-box-containing protein whose function is unknown. We found that the skp2 mutant accumulated H2S and SO2, because the adenosylphophosulfate kinase Met14p is a substrate of SCFSkp2 and more stable in the skp2 mutant than in the wild-type strain. Furthermore, the skp2 mutant grew more slowly than the wild-type strain under nutrient-limited conditions. Metabolome analysis showed that the concentration of intracellular cysteine is lower in the skp2 mutant than in the wild-type strain. The slow growth of the skp2 mutant was due to a lower concentration of intracellular cysteine, because the addition of cysteine suppressed the slow growth. In the skp2 mutant, the cysteine biosynthesis proteins Str2p, Str3p and Str4p are more stable than in the wild-type strain. Moreover, supplementation with methionine, S-adenosylmethionine, S-adenosylhomocysteine and homocysteine also suppressed the slow growth. Overexpression of STR1 or STR4 caused a more severe defect in the skp2 mutant. These results suggest that the balance of methionine and cysteine biosynthesis is important for yeast cell growth. Thus, Skp2p is one of the key components regulating this balance and H2S/SO2 production. © 2010 John Wiley & Sons, Ltd.

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A novel three-unit tRNA splicing endonuclease found in ultrasmall Archaea possesses broad substrate specificity

Fujishima K., Sugahara J., Miller C.S., Baker B.J., Di Giulio M., Takesue K., Sato A., Tomita M., Banfield J.F., Kanai A.

Nucleic Acids Research (Nucleic Acids Research) 39 ( 22 ) 9695-9704 - 9704 2011

Research paper (scientific journal), Joint Work, ISSN 03051048

tRNA splicing endonucleases, essential enzymes found in Archaea and Eukaryotes, are involved in the processing of pre-tRNA molecules. In Archaea, three types of splicing endonuclease [homotetrameric: α4, homodimeric: α2, and heterotetrameric: (αβ)2] have been identified, each representing different substrate specificity during the tRNA intron cleavage. Here, we discovered a fourth type of archaeal tRNA splicing endonuclease (2) in the genome of the acidophilic archaeon Candidatus Micrarchaeum acidiphilum, referred to as ARMAN-2 and its closely related species, ARMAN-1. The enzyme consists of two duplicated catalytic units and one structural unit encoded on a single gene, representing a novel three-unit architecture. Homodimeric formation was confirmed by cross-linking assay, and site-directed mutagenesis determined that the conserved L10-pocket interaction between catalytic and structural unit is necessary for the assembly. A tRNA splicing assay reveal that 2 endonuclease cleaves both canonical and non-canonical bulge-helix-bulge motifs, similar to that of (αβ)2 endonuclease. Unlike other ARMAN and Euryarchaeota, tRNAs found in ARMAN-2 are highly disrupted by introns at various positions, which again resemble the properties of archaeal species with (αβ)2 endonuclease. Thus, the discovery of 2 endonuclease in an archaeon deeply branched within Euryarchaeota represents a new example of the coevolution of tRNA and their processing enzymes. © The Author(s) 2011. Published by Oxford University Press.

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Redox Regulation in Respiring Saccharomyces cerevisiae

Murray, D.B., Haynes, K. and Tomita, M.

Biochim Biophys Acta. (Biochimica et Biophysica Acta - General Subjects) 1810 ( 10 ) 945-58 - 958 2011

Research paper (scientific journal), Joint Work, Accepted, ISSN 03044165

Background: In biological systems, redox reactions are central to most cellular processes and the redox potential of the intracellular compartment dictates whether a particular reaction can or cannot occur. Indeed the widespread use of redox reactions in biological systems makes their detailed description outside the scope of one review. Scope of the Review: Here we will focus on how system-wide redox changes can alter the reaction and transcriptional landscape of Saccharomyces cerevisiae. To understand this we explore the major determinants of cellular redox potential, how these are sensed by the cell and the dynamic responses elicited. Major Conclusions: Redox regulation is a large and complex system that has the potential to rapidly and globally alter both the reaction and transcription landscapes. Although we have a basic understanding of many of the sub-systems and a partial understanding of the transcriptional control, we are far from understanding how these systems integrate to produce coherent responses. We argue that this non-linear system self-organises, and that the output in many cases is temperature-compensated oscillations that may temporally partition incompatible reactions in vivo. General Significance: Redox biochemistry impinges on most of cellular processes and has been shown to underpin ageing and many human diseases. Integrating the complexity of redox signalling and regulation is perhaps one of the most challenging areas of biology. This article is part of a Special Issue entitled Systems Biology of Microorganisms. © 2011 Elsevier B.V. All rights reserved.

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Serum Metabolomics Reveals γ-glutamyl dipeptides as biomarkers for discrimination among different forms of liver disease

Soga, T., Sugimoto, M., Honma, M., Mori, M., Igarashi, K., Kashikura, K., Ikeda, S., Hirayama, A., Yamamoto, T., Yoshida, H., Otsuka, M., Tsuji, S., Yatomi, Y., Sakuragawa, T., Watanabe, H., Nihei, K., Saito, T., Kawata, S., Suzuki

J Hepatology (Journal of Hepatology) 55 ( 4 ) 896-905 - 905 2011

Research paper (scientific journal), Joint Work, Accepted, ISSN 01688278

Background & Aims: We applied a metabolome profiling approach to serum samples obtained from patients with different liver diseases, to discover noninvasive and reliable biomarkers for rapid-screening diagnosis of liver diseases. Methods: Using capillary electrophoresis and liquid chromatography mass spectrometry, we analyzed low molecular weight metabolites in a total of 248 serum samples obtained from patients with nine types of liver disease and healthy controls. Results: We found that γ-glutamyl dipeptides, which were biosynthesized through a reaction with γ-glutamylcysteine synthetase, were indicative of the production of reduced glutathione, and that measurement of their levels could distinguish among different liver diseases. Multiple logistic regression models facilitated the discrimination between specific and other liver diseases and yielded high areas under receiver-operating characteristic curves. The area under the curve values in training and independent validation data were 0.952 and 0.967 in healthy controls, 0.817 and 0.849 in drug-induced liver injury, 0.754 and 0.763 in asymptomatic hepatitis B virus infection, 0.820 and 0.762 in chronic hepatitis B, 0.972 and 0.895 in hepatitis C with persistently normal alanine transaminase, 0.917 and 0.707 in chronic hepatitis C, 0.803 and 0.993 in cirrhosis type C, and 0.762 and 0.803 in hepatocellular carcinoma, respectively. Several γ-glutamyl dipeptides also manifested potential for differentiating between nonalcoholic steatohepatitis and simple steatosis. Conclusions: γ-Glutamyl dipeptides are novel biomarkers for liver diseases, and varying levels of individual or groups of these peptides have the power to discriminate among different forms of hepatic disease. © 2011 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

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Predicting the Kinetic Properties Associated with Redox Imbalance after Oxidative Crisis in G6PD-Deficient Erythrocytes: A Simulation Study.

Shimo, H., Nishino, T. and Tomita, M.

Adv Hematol. (Advances in Hematology) 2011 398945 2011

Research paper (scientific journal), Joint Work, Accepted, ISSN 16879104

It is well known that G6PD-deficient individuals are highly susceptible to oxidative stress. However, the differences in the degree of metabolic alterations among patients during an oxidative crisis have not been extensively studied. In this study, we applied mathematical modeling to assess the metabolic changes in erythrocytes of various G6PD-deficient patients during hydrogen peroxide- (H2O2-) induced perturbation and predict the kinetic properties that elicit redox imbalance after exposure to an oxidative agent. Simulation results showed a discrepancy in the ability to restore regular metabolite levels and redox homeostasis among patients. Two trends were observed in the response of redox status (GSH/GSSG) to oxidative stress, a mild decrease associated with slow recovery and a drastic decline associated with rapid recovery. The former was concluded to apply to patients with severe clinical symptoms. Low Vmax and high KmG6P of G6PD were shown to be kinetic properties that enhance consequent redox imbalance. Copyright © 2011 Hanae Shimo et al.

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Enhancing apoptosis in TRAIL-resistant cancer cells using fundamental response rules

Piras, V., Hayashi, K., Tomita, M. and Selvarajoo, K

Scientific Reports (Scientific Reports) 1 144 2011

Research paper (scientific journal), Joint Work, Accepted

The tumor necrosis factor related apoptosis-inducing ligand (TRAIL) induces apoptosis in malignant cells, while leaving other cells mostly unharmed. However, several carcinomas remain resistant to TRAIL. To investigate the resistance mechanisms in TRAIL-stimulated human fibrosarcoma (HT1080) cells, we developed a computational model to analyze the temporal activation profiles of cell survival (IkB, JNK, p38) and apoptotic (caspase-8 and-3) molecules in wildtype and several (FADD, RIP1, TRAF2 and caspase-8) knock-down conditions. Based on perturbation-response approach utilizing the law of information (signaling flux) conservation, we derived response rules for population-level average cell response. From this approach, i) a FADD-independent pathway to activate p38 and JNK, ii) a crosstalk between RIP1 and p38, and iii) a crosstalk between p62 and JNK are predicted. Notably, subsequent simulations suggest that targeting a novel molecule at p62/sequestosome-1 junction will optimize apoptosis through signaling flux redistribution. This study offers a valuable prospective to sensitive TRAIL-based therapy.

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GTP-dependent RNA 3'-terminal phosphate cyclase from the hyperthermophilic archaeon Pyrococcus furiosus

Sato, A., Soga, T., Igarashi, K., Takesue, K., Tomita, M. and Kanai, A.

Genes to Cells (Genes to Cells) 16 ( 12 ) 1190-1199 - 1199 2011

Research paper (scientific journal), Joint Work, Accepted, ISSN 13569597

We discovered that the PF1549 gene in Pyrococcus furiosus encodes a very heat-stable RNA 3'-terminal phosphate cyclase (Pf-Rtc). Although all previously reported Rtc proteins are ATP-dependent enzymes, we found that Pf-Rtc requires GTP for its cyclase activity at 95°C. Low-level activation of the enzyme was also observed in the presence of dGTP but not other dNTPs, indicating that the guanine base is very important for Pf-Rtc activity. We analyzed a series of GTP analogues and found that the conversion from GTP to GMP is important for Pf-Rtc activity and that an excess of GMP inhibits this activity. Gel-shift analysis clearly showed that the RNA-binding activity of Pf-Rtc is totally dependent on the linear form of the 3'-terminal phosphate, with an apparent K d value of 20nm at 95°C. Furthermore, we found that Pf-Rtc may contribute to GTP-dependent RNA ligation activity through the PF0027 protein (a 2'-5' RNA ligase-like protein in P. furiosus). The possible roles of Pf-Rtc and the importance of terminal phosphate structures in RNA are discussed. © 2011 The Authors. Journal compilation © 2011 by the Molecular Biology Society of Japan/Blackwell Publishing Ltd.

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