title: Expression of cyclin D1 and CDK4 causes hypertrophic growth of cardiomyocytes in culture: a possible implication for cardiac hypertrophy.
abstract: Differentiated cardiomyocytes have little capacity to proliferate and show the hypertrophic growth in response to alpha1-adrenergic stimuli via the Ras/MEK pathway. In this study, we investigated a role of cyclin D1 and CDK4, a positive regulator of cell cycle, in cultured neonatal rat cardiomyocyte hypertrophy. D-type cyclins including cyclin D1 were induced in cells stimulated by phenylephrine. This induction was inhibited by MEK inhibitor PD98059 and the dominant negative RasN17, but mimicked by expression of the constitutive active Ras61L. Over-expression of cyclin D1 and CDK4 using adenovirus gene transfer caused the hypertrophic growth of cardiomyocytes, as evidenced by an increase of the cell size as well as the amount of cellular protein and its rate of synthesis. However, the cyclin D1/CDK4 kinase activity was not up-regulated in cells treated by hypertrophic stimuli or in cells over-expressing the cyclin D1 and CDK4. Furthermore, a CDK inhibitor, p16, did not inhibit the hypertrophic growth of cardiomyocytes. These results clearly indicated that cyclin D1 and CDK4 have a role in hypertrophic growth of cardiomyocytes through a novel mechanism(s) which appears not to be related to its activity required for cell cycle progression.
authors.affiliation: Department of Biochemical Genetics, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, Japan. mtam.bgen@mri.tmd.ac.jp
authors.forename: Mimi
authors.initials: M
authors.lastname: Tamamori-Adachi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ito
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Nobori
authors.forename: Kentaro
authors.initials: K
authors.lastname: Hayashida
authors.forename: Junya
authors.initials: J
authors.lastname: Kawauchi
authors.forename: Susumu
authors.initials: S
authors.lastname: Adachi
authors.forename: Masa-Aki
authors.initials: MA
authors.lastname: Ikeda
authors.forename: Shigetaka
authors.initials: S
authors.lastname: Kitajima
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism; D000256:Adenoviridae / Q000235:genetics / Q000378:metabolism; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D009320:Atrial Natriuretic Factor / Q000235:genetics / Q000378:metabolism; D006332:Cardiomegaly / Q000209:etiology / Q000378:metabolism*; D048429:Cell Size; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D019938:Cyclin D1 / Q000378:metabolism*; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D006321:Heart / Q000187:drug effects; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D010656:Phenylephrine / Q000494:pharmacology; D011518:Proto-Oncogene Proteins; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000199:Actins; D000316:Adrenergic alpha-Agonists; D016895:Culture Media, Serum-Free; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D019938:Cyclin D1; D010656:Phenylephrine; D009320:Atrial Natriuretic Factor; C495903:Cdk4 protein, rat; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases; D018631:ras Proteins