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Articles by H Nakanishi
Total Records ( 4 ) for H Nakanishi
  J Endo , M Sano , T Katayama , T Hishiki , K Shinmura , S Morizane , T Matsuhashi , Y Katsumata , Y Zhang , H Ito , Y Nagahata , S Marchitti , K Nishimaki , A. M Wolf , H Nakanishi , F Hattori , V Vasiliou , T Adachi , I Ohsawa , R Taguchi , Y Hirabayashi , S Ohta , M Suematsu , S Ogawa and K. Fukuda

Rationale: Aldehyde accumulation is regarded as a pathognomonic feature of oxidative stress–associated cardiovascular disease.

Objective: We investigated how the heart compensates for the accelerated accumulation of aldehydes.

Methods and Results: Aldehyde dehydrogenase 2 (ALDH2) has a major role in aldehyde detoxification in the mitochondria, a major source of aldehydes. Transgenic (Tg) mice carrying an Aldh2 gene with a single nucleotide polymorphism (Aldh2*2) were developed. This polymorphism has a dominant-negative effect and the Tg mice exhibited impaired ALDH activity against a broad range of aldehydes. Despite a shift toward the oxidative state in mitochondrial matrices, Aldh2*2 Tg hearts displayed normal left ventricular function by echocardiography and, because of metabolic remodeling, an unexpected tolerance to oxidative stress induced by ischemia/reperfusion injury. Mitochondrial aldehyde stress stimulated eukaryotic translation initiation factor 2 phosphorylation. Subsequent translational and transcriptional activation of activating transcription factor-4 promoted the expression of enzymes involved in amino acid biosynthesis and transport, ultimately providing precursor amino acids for glutathione biosynthesis. Intracellular glutathione levels were increased 1.37-fold in Aldh2*2 Tg hearts compared with wild-type controls. Heterozygous knockout of Atf4 blunted the increase in intracellular glutathione levels in Aldh2*2 Tg hearts, thereby attenuating the oxidative stress–resistant phenotype. Furthermore, glycolysis and NADPH generation via the pentose phosphate pathway were activated in Aldh2*2 Tg hearts. (NADPH is required for the recycling of oxidized glutathione.)

Conclusions: The findings of the present study indicate that mitochondrial aldehyde stress in the heart induces metabolic remodeling, leading to activation of the glutathione–redox cycle, which confers resistance against acute oxidative stress induced by ischemia/reperfusion.

  D Yamazaki , S Komazaki , H Nakanishi , A Mishima , M Nishi , M Yazawa , T Yamazaki , R Taguchi and H. Takeshima
  Daiju Yamazaki, Shinji Komazaki, Hiroki Nakanishi, Aya Mishima, Miyuki Nishi, Masayuki Yazawa, Tetsuo Yamazaki, Ryo Taguchi, and Hiroshi Takeshima

TRIC channels function as monovalent cation-specific channels that mediate counter ion movements coupled with ryanodine receptor-mediated Ca2+ release from intracellular stores in muscle cells. Mammalian tissues differentially contain two TRIC channel subtypes: TRIC-A is abundantly expressed in excitable cells, whereas TRIC-B is ubiquitously expressed throughout tissues. Here, we report the physiological role of TRIC-B channels in mouse perinatal development. TRIC-B-knockout neonates were cyanotic owing to respiratory failure and died shortly after birth. In the mutant neonates, the deflated lungs exhibited severe histological defects, and alveolar type II epithelial cells displayed ultrastructural abnormalities. The metabolic conversion of glycogen into phospholipids was severely interrupted in the mutant type II cells, and surfactant phospholipids secreted into the alveolar space were insufficient in the mutant neonates. Moreover, the mutant type II cells were compromised for Ca2+ release mediated by inositol-trisphosphate receptors, despite Ca2+ overloading in intracellular stores. Our results indicate that TRIC-B channels take an active part in Ca2+ signalling to establish specialised functions in type II cells and are thus...

  Y Ishimaru , K Bashir , M Fujimoto , G An , R. N Itai , N Tsutsumi , H Nakanishi and N. K Nishizawa

Mitochondria utilize iron (Fe), but the proteins involved in mitochondrial Fe regulation are not characterized in plants. We cloned and characterized a mitochondrial iron-regulated (MIR) gene in rice involved in Fe homeostasis. MIR, when expressed in tobacco BY-2 cells, was localized to the mitochondria. MIR transcripts were greatly increased in response to Fe deficiency in roots and shoot tissue. MIR is not homologous to any known protein, as homologs were not found in the rice or Arabidopsis genome databases, or in the EST database for other organisms. Growth in the MIR T-DNA knockout rice mutant (mir) was significantly impaired compared to wild-type (WT) plants when grown under Fe-deficient or -sufficient conditions. Furthermore, mir plants accumulated more than twice the amount of Fe in shoot and root tissue compared to WT plants when grown under either Fe-sufficient or -deficient conditions. Despite the high accumulation of Fe in roots and shoots, mir plants triggered the expression of Fe-deficiency-inducible genes, indicating that mir may not be able to utilize Fe for physiological functions. These results clearly suggest that MIR is a rice-specific mitochondrial protein, recently evolved, and plays a significant role in Fe homeostasis.

  K Yanagida , K Masago , H Nakanishi , Y Kihara , F Hamano , Y Tajima , R Taguchi , T Shimizu and S. Ishii

p2y5 is an orphan G protein-coupled receptor that is closely related to the fourth lysophosphatidic acid (LPA) receptor, LPA4. Here we report that p2y5 is a novel LPA receptor coupling to the G13-Rho signaling pathway. "LPA receptor-null" RH7777 and B103 cells exogenously expressing p2y5 showed [3H]LPA binding, LPA-induced [35S]guanosine 5'-3-O-(thio)triphosphate binding, Rho-dependent alternation of cellular morphology, and Gs/13 chimeric protein-mediated cAMP accumulation. LPA-induced contraction of human umbilical vein endothelial cells was suppressed by small interfering RNA knockdown of endogenously expressed p2y5. We also found that 2-acyl-LPA had higher activity to p2y5 than 1-acyl-LPA. A recent study has suggested that p2y5 is an LPA receptor essential for human hair growth. We confirmed that p2y5 is a functional LPA receptor and propose to designate this receptor LPA6.

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