title: Mitochondrial Inhibitory Factor Protein 1 Functions as an Endogenous Inhibitor for Coupling Factor 6.
abstract: Coupling factor 6 (CF6) forces a counter-clockwise rotation of plasma membrane F1 Fo complex unlike a proton-mediated clockwise rotation in the mitochondria, resulting in ATP hydrolysis, proton import, and apoptosis. Inhibitory peptide 1 (IF1) inhibits a unidirectional counter-clockwise rotation of F1 Fo complex without affecting ATP synthesis by a clockwise rotation. We tested the hypothesis that IF1 may antagonize the biological action of CF6 in human embryonic kidney 293 cells. We generated mature and immature IF1 expression vectors and those labeled with GFP at the C-terminus. In the immature IF1-GFP overexpressing cells, the mitochondrial network of IF1-GFP was newly found at the plasma membrane after peripheral translocation, whereas in mature IF1-GFP transfected cells, a less punctuate rather homogenous pattern was found in the cytoplasm. IF1 protein was detected in the exosome fraction of culture media, and it was enhanced by mature or immature IF1 transfection. Extracellular ATP hydrolysis was enhanced by CF6, whereas immature or mature IF1 transfection suppressed ATP hydrolysis in response to CF6. Intracellular pH was decreased by CF6 but was unchanged after immature IF1 transfection. CF6-induced increase in apoptotic cells was blocked by immature or mature IF1, being accompanied by protein kinase B (PKB) phosphorylation. IF1 antagonizes the pro-apoptotic action of CF6 by relief of intracellular acidification and resultant phosphorylation of PKB. Given the widespread biological actions of CF6, the physiological and pathological functions of IF1 may be expected to be complex. J. Cell. Biochem. 117: 1680-1687, 2016. © 2015 Wiley Periodicals, Inc.
authors.affiliation: Department of Cardiology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.
authors.forename: Misato
authors.initials: M
authors.lastname: Kawai
authors.affiliation: Department of Health Promotion, Hirosaki University Graduate School of Health Science, Hirosaki, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Osanai
authors.affiliation: Department of Hypertension and Stroke Internal Medicine, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Tanaka
authors.affiliation: Faculty of Discovery and Biotechnology II, Asubio Pharma Co., Ltd., 6-4-3 Minatojima-Minamimachi, Chuo-ku, Kobe, 650-0047, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Magota
authors.affiliation: Department of Cardiology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Tomita
authors.affiliation: Department of Cardiology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Okumura
mesh_terms: D017209:Apoptosis; D055354:Exosomes / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D025261:Mitochondrial Proton-Translocating ATPases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D010086:Oxidative Phosphorylation Coupling Factors / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000235:genetics; D021381:Protein Transport / Q000235:genetics; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D000097795:ATPase Inhibitory Protein
chemical_list: D025261:Mitochondrial Proton-Translocating ATPases; D010086:Oxidative Phosphorylation Coupling Factors; D011506:Proteins; D051057:Proto-Oncogene Proteins c-akt; D006180:Proton-Translocating ATPases; D000097795:ATPase Inhibitory Protein; C000628217:F(6) ATPase
keywords: APOPTOSIS; ATP; COUPLING FACTOR 6; ECTO-F1FO COMPLEX; INHIBITORY PEPTIDE 1; INTRACELLULAR ACIDOSIS