title: Cell death suppressor Arabidopsis bax inhibitor-1 is associated with calmodulin binding and ion homeostasis.
abstract: Cell death suppressor Bax inhibitor-1 (BI-1), an endoplasmic reticulum membrane protein, exists in a wide range of organisms. The split-ubiquitin system, overlay assay, and bimolecular fluorescence complementation analysis demonstrated that Arabidopsis (Arabidopsis thaliana) BI-1 (AtBI-1) interacted with calmodulin in yeast (Saccharomyces cerevisiae) and in plant cells. Furthermore, AtBI-1 failed to rescue yeast mutants lacking Ca2+ ATPase (Pmr1 or Spf1) from Bax-induced cell death. Pmr1 and Spf1, p-type ATPases localized at the inner membrane, are believed to be involved in transmembrane movement of calcium ions in yeast. Thus, the presence of intact Ca2+ ATPases was essential for AtBI-1-mediated cell death suppression in yeast. To investigate the effect of AtBI-1 on calcium homeostasis, we evaluated sensitivity against cyclopiazonic acid (CPA), an inhibitor of sarcoplasmic/endoplasmic reticulum Ca2+ ATPase in AtBI-1-overexpressing or knock-down transgenic Arabidopsis plants. These plants demonstrated altered CPA or ion stress sensitivity. Furthermore, AtBI-1-overexpressing cells demonstrated an attenuated rise in cytosolic calcium following CPA or H2O2 treatment, suggesting that AtBI-1 affects ion homeostasis in plant cell death regulation.
authors.affiliation: Institute of Molecular and Cellular Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Ihara-Ohori
authors.forename: Minoru
authors.initials: M
authors.lastname: Nagano
authors.forename: Shoshi
authors.initials: S
authors.lastname: Muto
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Uchimiya
authors.forename: Maki
authors.initials: M
authors.lastname: Kawai-Yamada
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism*; D016923:Cell Death / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant; D006706:Homeostasis; D001467:Hordeum / Q000235:genetics / Q000378:metabolism; D007211:Indoles / Q000494:pharmacology; D007477:Ions / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011485:Protein Binding
chemical_list: C491862:ATBI-1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D002147:Calmodulin; D004791:Enzyme Inhibitors; D007211:Indoles; D007477:Ions; C104922:MLO protein, Hordeum vulgare; D008565:Membrane Proteins; D010940:Plant Proteins; D002118:Calcium; C000543:cyclopiazonic acid