title: MicroRNA-15b modulates cellular ATP levels and degenerates mitochondria via Arl2 in neonatal rat cardiac myocytes.
abstract: MicroRNAs (miRNAs or miRs) are small, non-coding RNAs that modulate mRNA stability and post-transcriptional translation. A growing body of evidence indicates that specific miRNAs can affect the cellular function of cardiomyocytes. In the present study, miRNAs that are highly expressed in the heart were overexpressed in neonatal rat ventricular myocytes, and cellular ATP levels were assessed. As a result, miR-15b, -16, -195, and -424, which have the same seed sequence, the most critical determinant of miRNA targeting, decreased cellular ATP levels. These results suggest that these miRNAs could specifically down-regulate the same target genes and consequently decrease cellular ATP levels. Through a bioinformatics approach, ADP-ribosylation factor-like 2 (Arl2) was identified as a potential target of miR-15b. It has already been shown that Arl2 localizes to adenine nucleotide transporter 1, the exchanger of ADP/ATP in mitochondria. Overexpression of miR-15b, -16, -195, and -424 suppressed the activity of a luciferase reporter construct fused with the 3'-untranslated region of Arl2. In addition, miR-15b overexpression decreased Arl2 mRNA and protein expression levels. The effects of Arl2 siRNA on cellular ATP levels were the same as those of miR-15b, and the expression of Arl2 could restore ATP levels reduced by miR-15b. A loss-of-function study of miR-15b resulted in increased Arl2 protein and cellular ATP levels. Electron microscopic analysis revealed that mitochondria became degenerated in cardiomyocytes that had been transduced with miR-15b and Arl2 siRNA. The present results suggest that miR-15b may decrease mitochondrial integrity by targeting Arl2 in the heart.
authors.affiliation: Department of Cardiovascular Medicine, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan.
authors.forename: Hitoo
authors.initials: H
authors.lastname: Nishi
authors.forename: Koh
authors.initials: K
authors.lastname: Ono
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Iwanaga
authors.forename: Takahiro
authors.initials: T
authors.lastname: Horie
authors.forename: Kazuya
authors.initials: K
authors.lastname: Nagao
authors.forename: Genzou
authors.initials: G
authors.lastname: Takemura
authors.forename: Minako
authors.initials: M
authors.lastname: Kinoshita
authors.forename: Yasuhide
authors.initials: Y
authors.lastname: Kuwabara
authors.forename: Rieko Takanabe
authors.initials: RT
authors.lastname: Mori
authors.forename: Koji
authors.initials: K
authors.lastname: Hasegawa
authors.forename: Toru
authors.initials: T
authors.lastname: Kita
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kimura
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D002470:Cell Survival; D002478:Cells, Cultured; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D035683:MicroRNAs / Q000235:genetics / Q000502:physiology*; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D032383:Myocytes, Cardiac / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D035683:MicroRNAs; D000255:Adenosine Triphosphate; C485820:Arl2 protein, rat; D019204:GTP-Binding Proteins