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Articles by H Shibata
Total Records ( 2 ) for H Shibata
  Y Mukai , T Nakamura , Y Yoshioka , H Shibata , Y Abe , T Nomura , M Taniai , T Ohta , S Nakagawa , S. i Tsunoda , H Kamada , Y Yamagata and Y. Tsutsumi

Tumour necrosis factor (TNF) is an important cytokine that induces an inflammatory response predominantly through the TNF receptor-1 (TNFR1). A crucial strategy for the treatment of many autoimmune diseases, therefore, is to block the binding of TNF to TNFR1. We previously identified a TNFR1-selective antagonistic mutant TNF (R1antTNF) from a phage library containing six randomized amino acid residues at the receptor-binding site (amino acids 84–89). Two R1antTNFs, R1antTNF-T2 (A84S, V85T, S86T, Y87H, Q88N and T89Q) and R1antTNF-T8 (A84T, V85P, S86A, Y87I, Q88N and T89R), were successfully isolated from this library. Here, we analysed R1antTNF-T8 using surface plasmon resonance spectroscopy and X-ray crystallography to determine the mechanism underlying the antagonistic activity of R1antTNF. The kinetic association/dissociation parameters of R1antTNF-T8 were higher than those of wild-type TNF, indicating more rapid bond dissociation. X-ray crystallographic analysis suggested that the binding mode of the T89R mutation changed from a hydrophobic to an electrostatic interaction, which may be responsible for the antagonistic behaviour of R1antTNF. Knowledge of these structure–function relationships will facilitate the design of novel TNF inhibitors based on the cytokine structure.

  T Kita , H Nishida , H Shibata , S Niimi , T Higuti and N. Arakaki

Mitochondrial fusion and fission processes play a role in a variety of cell functions, including energy metabolism, cell differentiation and programmed cell death. Still, it is not clear how these processes contribute to the cell functions. Here, we investigated the role of mitochondrial remodelling on lipid metabolism in adipocytes. In 3T3-L1 pre-adipocytes, the morphology of mitochondria is organized as a continuous reticulum. Upon differentiation of adipocytes manifested by cellular triacylglycerol (TG) accumulation, mitochondrial morphology altered from filamentous to fragmented and/or punctate structures. When the mitochondrial fusion was induced in adipocytes by silencing of mitochondrial fission proteins including Fis1 and Drp1, the cellular TG content was decreased. In contrast, the silencing of mitochondrial fusion proteins including mitofusin 2 and Opa1 increased the cellular TG content followed by fragmentation of mitochondria. It also appears that polyphenolic phytochemicals, negative regulators of lipid accumulation, have mitochondrial fusion activity and that there is a good correlation between mitochondrial fusion activity and the cellular TG accumulation-reducing activity of the phytochemicals. These results suggest that cellular TG accumulation is regulated, at least in part, via mitochondrial fusion and fission processes.

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