Graduate School of Media and Governance (Shonan Fujisawa)


Project Professor (Non-tenured)


Papers 【 Display / hide

  • IMPDH inhibition activates TLR-VCAM1 pathway and suppresses the development of MLL-fusion leukemia

    Liu X., Sato N., Yabushita T., Li J., Jia Y., Tamura M., Asada S., Fujino T., Fukushima T., Yonezawa T., Tanaka Y., Fukuyama T., Tsuchiya A., Shikata S., Iwamura H., Kinouchi C., Komatsu K., Yamasaki S., Shibata T., Sasaki A.T., Schibler J., Wunderlich M., O'Brien E., Mizukawa B., Mulloy J.C., Sugiura Y., Takizawa H., Shibata T., Miyake K., Kitamura T., Goyama S.

    EMBO Molecular Medicine (EMBO Molecular Medicine)  15 ( 1 )  2023.01

    ISSN  17574676

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    Inosine monophosphate dehydrogenase (IMPDH) is a rate-limiting enzyme in de novo guanine nucleotide synthesis pathway. Although IMPDH inhibitors are widely used as effective immunosuppressants, their antitumor effects have not been proven in the clinical setting. Here, we found that acute myeloid leukemias (AMLs) with MLL-fusions are susceptible to IMPDH inhibitors in vitro. We also showed that alternate-day administration of IMPDH inhibitors suppressed the development of MLL-AF9-driven AML in vivo without having a devastating effect on immune function. Mechanistically, IMPDH inhibition induced overactivation of Toll-like receptor (TLR)-TRAF6-NF-κB signaling and upregulation of an adhesion molecule VCAM1, which contribute to the antileukemia effect of IMPDH inhibitors. Consequently, combined treatment with IMPDH inhibitors and the TLR1/2 agonist effectively inhibited the development of MLL-fusion AML. These findings provide a rational basis for clinical testing of IMPDH inhibitors against MLL-fusion AMLs and potentially other aggressive tumors with active TLR signaling.

  • Functional molecular evolution of a GTP sensing kinase: PI5P4Kβ

    Takeuchi K., Senda M., Ikeda Y., Okuwaki K., Fukuzawa K., Nakagawa S., Sasaki M., Sasaki A.T., Senda T.

    FEBS Journal (FEBS Journal)   2023

    ISSN  1742464X

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    Over 4 billion years of evolution, multiple mutations, including nucleotide substitutions, gene and genome duplications and recombination, have established de novo genes that translate into proteins with novel properties essential for high-order cellular functions. However, molecular processes through which a protein evolutionarily acquires a novel function are mostly speculative. Recently, we have provided evidence for a potential evolutionary mechanism underlying how, in mammalian cells, phosphatidylinositol 5-phosphate 4-kinase β (PI5P4Kβ) evolved into a GTP sensor from ATP-utilizing kinase. Mechanistically, PI5P4Kβ has acquired the guanine efficient association (GEA) motif by mutating its nucleotide base recognition sequence, enabling the evolutionary transition from an ATP-dependent kinase to a distinct GTP/ATP dual kinase with its KM for GTP falling into physiological GTP concentrations—the genesis of GTP sensing activity. Importantly, the GTP sensing activity of PI5P4Kβ is critical for the manifestation of cellular metabolism and tumourigenic activity in the multicellular organism. The combination of structural, biochemical and biophysical analyses used in our study provides a novel framework for analysing how a protein can evolutionarily acquire a novel activity, which potentially introduces a critical function to the cell.

  • Beyond Warburg: LDHA activates RAC for tumour growth

    Osaka N., Sasaki A.T.

    Nature Metabolism (Nature Metabolism)  4 ( 12 ) 1623 - 1625 2022.12

  • The GTP responsiveness of PI5P4Kβ evolved from a compromised trade-off between activity and specificity

    Takeuchi K., Ikeda Y., Senda M., Harada A., Okuwaki K., Fukuzawa K., Nakagawa S., Yu H.Y., Nagase L., Imai M., Sasaki M., Lo Y.H., Ito D., Osaka N., Fujii Y., Sasaki A.T., Senda T.

    Structure (Structure)  30 ( 6 ) 886 - 899.e4 2022.06

    ISSN  09692126

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    Unlike most kinases, phosphatidylinositol 5-phosphate 4-kinase β (PI5P4Kβ) utilizes GTP as a physiological phosphate donor and regulates cell growth under stress (i.e., GTP-dependent stress resilience). However, the genesis and evolution of its GTP responsiveness remain unknown. Here, we reveal that PI5P4Kβ has acquired GTP preference by generating a short dual-nucleotide-recognizing motif called the guanine efficient association (GEA) motif. Comparison of nucleobase recognition with 660 kinases and 128 G proteins has uncovered that most kinases and PI5P4Kβ use their main-chain atoms for adenine recognition, while the side-chain atoms are required for guanine recognition. Mutational analysis of the GEA motif revealed that the acquisition of GTP reactivity is accompanied by an extended activity toward inosine triphosphate (ITP) and xanthosine triphosphate (XTP). Along with the evolutionary analysis data that point to strong negative selection of the GEA motif, these results suggest that the GTP responsiveness of PI5P4Kβ has evolved from a compromised trade-off between activity and specificity, underpinning the development of the GTP-dependent stress resilience.

  • SI-MOIRAI: A new method to identify and quantify the metabolic fate of nucleotides

    Ikeda Y., Hirayama A., Kofuji S., Hirota Y., Kamata R., Osaka N., Fujii Y., Sasaki M., Ikeda S., Smith E.P., Bachoo R., Soga T., Sasaki A.T.

    Journal of Biochemistry (Journal of Biochemistry)  170 ( 6 ) 699 - 711 2021.12

    ISSN  0021924X

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    Since the discovery of nucleotides over 100 years ago, extensive studies have revealed the importance of nucleotides for homeostasis, health and disease. However, there remains no established method to investigate quantitatively and accurately intact nucleotide incorporation into RNA and DNA. Herein, we report a new method, Stable-Isotope Measure Of Influxed Ribonucleic Acid Index (SI-MOIRAI), for the identification and quantification of the metabolic fate of ribonucleotides and their precursors. SI-MOIRAI, named after Greek goddesses of fate, combines a stable isotope-labelling flux assay with mass spectrometry to enable quantification of the newly synthesized ribonucleotides into r/m/tRNA under a metabolic stationary state. Using glioblastoma (GBM) U87MG cells and a patient-derived xenograft (PDX) GBM mouse model, SI-MOIRAI analyses showed that newly synthesized GTP was particularly and disproportionally highly utilized for rRNA and tRNA synthesis but not for mRNA synthesis in GBM in vitro and in vivo. Furthermore, newly synthesized pyrimidine nucleotides exhibited a significantly lower utilization rate for RNA synthesis than newly synthesized purine nucleotides. The results reveal the existence of discrete pathways and compartmentalization of purine and pyrimidine metabolism designated for RNA synthesis, demonstrating the capacity of SI-MOIRAI to reveal previously unknown aspects of nucleotide biology.

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Research Projects of Competitive Funds, etc. 【 Display / hide

  • GTPの駆動する増殖ストレス緩和システムの分子基盤の解明


    MEXT,JSPS, Grant-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), Principal investigator