title: Btg2 is a Negative Regulator of Cardiomyocyte Hypertrophy through a Decrease in Cytosolic RNA.
abstract: Under hypertrophic stimulation, cardiomyocytes enter a hypermetabolic state and accelerate biomass accumulation. Although the molecular pathways that regulate protein levels are well-studied, the functional implications of RNA accumulation and its regulatory mechanisms in cardiomyocytes remain elusive. Here, we have elucidated the quantitative kinetics of RNA in cardiomyocytes through single cell imaging and c-Myc (Myc)-mediated hypermetabolic analytical model using cultured cardiomyocytes. Nascent RNA labeling combined with single cell imaging demonstrated that Myc protein significantly increased the amount of global RNA production per cardiomyocyte. Chromatin immunoprecipitation with high-throughput sequencing clarified that overexpressed Myc bound to a specific set of genes and recruits RNA polymerase II. Among these genes, we identified Btg2 as a novel target of Myc. Btg2 overexpression significantly reduced cardiomyocyte surface area. Conversely, shRNA-mediated knockdown of Btg2 accelerated adrenergic stimulus-induced hypertrophy. Using mass spectrometry analysis, we determined that Btg2 binds a series of proteins that comprise mRNA deadenylation complexes. Intriguingly, Btg2 specifically suppresses cytosolic, but not nuclear, RNA levels. Btg2 knockdown further enhances cytosolic RNA accumulation in cardiomyocytes under adrenergic stimulation, suggesting that Btg2 negatively regulates reactive hypertrophy by negatively regulating RNA accumulation. Our findings provide insight into the functional significance of the mechanisms regulating RNA levels in cardiomyocytes.
authors.affiliation: Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Masumura
authors.affiliation: Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Shuichiro
authors.initials: S
authors.lastname: Higo
authors.affiliation: Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Asano
authors.affiliation: Department of Medical Biochemistry, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Hisakazu
authors.initials: H
authors.lastname: Kato
authors.affiliation: Department of Medical Biochemistry, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Yi
authors.initials: Y
authors.lastname: Yan
authors.affiliation: Center of Medical Innovation and Translational Research, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Saki
authors.initials: S
authors.lastname: Ishino
authors.affiliation: Department of Medical Biochemistry, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Tsukamoto
authors.affiliation: Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Kioka
authors.affiliation: Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Takaharu
authors.initials: T
authors.lastname: Hayashi
authors.affiliation: Department of Medical Biochemistry, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Shintani
authors.affiliation: Department of Cell Biology, National Cerebral and Cardiovascular Center, Suita, Osaka 565-8565, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Yamazaki
authors.affiliation: Department of Cardiorenal and Cerebrovascular Medicine, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho, Kita-gun, Kagawa 761-0793, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Minamino
authors.affiliation: Department of Clinical Medicine and Development, National Cerebral and Cardiovascular Center, Suita, Osaka 565-8565, Japan.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Kitakaze
authors.affiliation: Department of Cardiovascular Medicine, Graduate School of Medicine, The University of Tokyo, Hongo, Bunkyo, Tokyo 113-8655, Japan.
authors.forename: Issei
authors.initials: I
authors.lastname: Komuro
authors.affiliation: Department of Medical Biochemistry, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Takashima
authors.affiliation: Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Sakata
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism*; D006984:Hypertrophy / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D032383:Myocytes, Cardiac / Q000378:metabolism*; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism*; D051381:Rats; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
chemical_list: D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D025521:Tumor Suppressor Proteins