Publications

• Functional association of cell death suppressor, Arabidopsis Bax inhibitor-1, with fatty acid 2-hydroxylation through cytochrome b(5).

  Nagano M., Ihara-Ohori Y., Imai H., Inada N., Fujimoto M., Tsutsumi N., Uchimiya H., Kawai-Yamada M.

  Bax inhibitor-1 (BI-1) is a widely conserved cytoprotective protein localized in the endoplasmic reticulum (ER) membrane. We identified Arabidopsis cytochrome b(5) (AtCb5) as an interactor of Arabidopsis BI-1 (AtBI-1) by screening the Arabidopsis cDNA library with the split-ubiquitin yeast two-hy ... >> More

  Bax inhibitor-1 (BI-1) is a widely conserved cytoprotective protein localized in the endoplasmic reticulum (ER) membrane. We identified Arabidopsis cytochrome b(5) (AtCb5) as an interactor of Arabidopsis BI-1 (AtBI-1) by screening the Arabidopsis cDNA library with the split-ubiquitin yeast two-hybrid (suY2H) system. Cb5 is an electron transfer protein localized mainly in the ER membrane. In addition, a bimolecular fluorescence complementation (BiFC) assay and fluorescence resonance energy transfer (FRET) analysis confirmed that AtBI-1 interacted with AtCb5 in plants. On the other hand, we found that the AtBI-1-mediated suppression of cell death in yeast requires Saccharomyces cerevisiae fatty acid hydroxylase 1 (ScFAH1), which had a Cb5-like domain at the N terminus and interacted with AtBI-1. ScFAH1 is a sphingolipid fatty acid 2-hydroxylase localized in the ER membrane. In contrast, AtFAH1 and AtFAH2, which are functional ScFAH1 homologues in Arabidopsis, had no Cb5-like domain, and instead interacted with AtCb5 in plants. These results suggest that AtBI-1 interacts with AtFAHs via AtCb5 in plant cells. Furthermore, the overexpression of AtBI-1 increased the level of 2-hydroxy fatty acids in Arabidopsis, indicating that AtBI-1 is involved in fatty acid 2-hydroxylation. << Less

  Plant J. 58:122-134(2009) [PubMed] [EuropePMC]

• Arabidopsis sphingolipid fatty acid 2-hydroxylases (AtFAH1 and AtFAH2) are functionally differentiated in fatty acid 2-hydroxylation and stress responses.

  Nagano M., Takahara K., Fujimoto M., Tsutsumi N., Uchimiya H., Kawai-Yamada M.

  2-Hydroxy fatty acids (2-HFAs) are predominantly present in sphingolipids and have important physicochemical and physiological functions in eukaryotic cells. Recent studies from our group demonstrated that sphingolipid fatty acid 2-hydroxylase (FAH) is required for the function of Arabidopsis (Ara ... >> More

  2-Hydroxy fatty acids (2-HFAs) are predominantly present in sphingolipids and have important physicochemical and physiological functions in eukaryotic cells. Recent studies from our group demonstrated that sphingolipid fatty acid 2-hydroxylase (FAH) is required for the function of Arabidopsis (Arabidopsis thaliana) Bax inhibitor-1 (AtBI-1), which is an endoplasmic reticulum membrane-localized cell death suppressor. However, little is known about the function of two Arabidopsis FAH homologs (AtFAH1 and AtFAH2), and it remains unclear whether 2-HFAs participate in cell death regulation. In this study, we found that both AtFAH1 and AtFAH2 had FAH activity, and the interaction with Arabidopsis cytochrome b₅ was needed for the sufficient activity. 2-HFA analysis of AtFAH1 knockdown lines and atfah2 mutant showed that AtFAH1 mainly 2-hydroxylated very-long-chain fatty acid (VLCFA), whereas AtFAH2 selectively 2-hydroxylated palmitic acid in Arabidopsis. In addition, 2-HFAs were related to resistance to oxidative stress, and AtFAH1 or 2-hydroxy VLCFA showed particularly strong responses to oxidative stress. Furthermore, AtFAH1 interacted with AtBI-1 via cytochrome b₅ more preferentially than AtFAH2. Our results suggest that AtFAH1 and AtFAH2 are functionally different FAHs, and that AtFAH1 or 2-hydroxy VLCFA is a key factor in AtBI-1-mediated cell death suppression. << Less

  Plant Physiol. 159:1138-1148(2012) [PubMed] [EuropePMC]

• Plant sphingolipid fatty acid 2-hydroxylases have unique characters unlike their animal and fungus counterparts.

  Nagano M., Uchimiya H., Kawai-Yamada M.

  2-Hydroxy fatty acids mainly contained in sphingolipids are synthesized by a sphingolipid fatty acid 2-hydroxylase (FAH). Recently, two FAH homologs in Arabidopsis thaliana (AtFAH1 and AtFAH2), without any cytochrome b₅(Cb5)-like domains, which are essential for the function of Saccharomyces cerev ... >> More

  2-Hydroxy fatty acids mainly contained in sphingolipids are synthesized by a sphingolipid fatty acid 2-hydroxylase (FAH). Recently, two FAH homologs in Arabidopsis thaliana (AtFAH1 and AtFAH2), without any cytochrome b₅(Cb5)-like domains, which are essential for the function of Saccharomyces cerevisiae and mammalian FAH, were identified and both AtFAHs were shown to be activated by the interaction with Cb5. In this study, we compared FAHs of various plants, animals and fungi. Interestingly, only plants had two FAH homologs and none of plant FAHs had any Cb5-like domains. In addition, we showed from the interaction and expression analyses that AtFAHs interacted with multiple Cb5s probably in various tissues. Thus, plant FAHs may have evolved unlike animal and fungus FAHs. << Less

  Plant Signal. Behav. 7:1388-1392(2012) [PubMed] [EuropePMC]