title: Up-regulation of micro-RNA765 in human failing hearts is associated with post-transcriptional regulation of protein phosphatase inhibitor-1 and depressed contractility.
abstract: OBJECTIVE
  Impaired sarcoplasmic reticulum (SR) Ca(2+) cycling and depressed contractility, a hallmark of human and experimental heart failure, has been partially attributed to increased protein phosphatase 1 (PP-1) activity, associated with down-regulation of its endogenous inhibitor-1. The levels and activity of inhibitor-1 are reduced in failing hearts, contributing to dephosphorylation and inactivation of key calcium cycling proteins. Therefore, we investigated the mechanisms that mediate decreases in inhibitor-1 by post-transcriptional modification.
  
  
  RESULTS
  Bioinformatics revealed that 17 human microRNAs may serve as modulators of inhibitor-1. However, real-time PCR analysis identified only one of these microRNAs, miR-765, as being increased in human failing hearts concomitant with decreased inhibitor-1 levels. Expression of miR-765 in HEK293 cells or mouse ventricular myocytes confirmed suppression of inhibitor-1 levels through binding of this miR-765 to the 3'-untranslated region of inhibitor-1 mRNA. To determine the functional significance of miR-765 in Ca(2+) cycling, pri-miR-765 as well as a non-translated nucleotide sequence (miR-Ctrl) were expressed in adult mouse ventricular myocytes. The inhibitor-1 expression levels were decreased, accompanied by enhanced PP-1 activity in the miR-765 cardiomyocytes, and these reflected depressed contractile mechanics and Ca(2+) transients, compared with the miR-Ctrl group. The depressive effects were associated with decreases in the phosphorylation of phospholamban and SR Ca(2+) load. These miR-765 negative inotropic effects were abrogated in inhibitor-1-deficient cardiomyocytes, suggesting its apparent specificity for inhibitor-1.
  
  
  CONCLUSIONS
  miR-765 levels are increased in human failing hearts. Such increases may contribute to depressed cardiac function through reduced inhibitor-1 expression and enhanced PP-1 activity, associated with reduced SR Ca(2+) load.
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
authors.forename: Wen-Feng
authors.initials: WF
authors.lastname: Cai
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
authors.forename: Guan-Sheng
authors.initials: GS
authors.lastname: Liu
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
authors.forename: Chi Keung
authors.initials: CK
authors.lastname: Lam
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
authors.forename: Stela
authors.initials: S
authors.lastname: Florea
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
authors.forename: Jiang
authors.initials: J
authors.lastname: Qian
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
authors.forename: Wen
authors.initials: W
authors.lastname: Zhao
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
authors.forename: Tracy
authors.initials: T
authors.lastname: Pritchard
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
authors.forename: Kobra
authors.initials: K
authors.lastname: Haghighi
authors.affiliation: Cardiovascular Research Center, Mount Sinai School of Medicine, New York, NY, USA.
authors.forename: Djamel
authors.initials: D
authors.lastname: Lebeche
authors.affiliation: Division of Biomedical Informatics, Cincinnati Children's Hospital Research Foundation, Cincinnati, OH, USA.
authors.forename: Long Jason
authors.initials: LJ
authors.lastname: Lu
authors.affiliation: Division of Biomedical Informatics, Cincinnati Children's Hospital Research Foundation, Cincinnati, OH, USA.
authors.forename: Jingyuan
authors.initials: J
authors.lastname: Deng
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
authors.forename: Guo-Chang
authors.initials: GC
authors.lastname: Fan
authors.affiliation: Cardiovascular Research Center, Mount Sinai School of Medicine, New York, NY, USA.
authors.forename: Roger J
authors.initials: RJ
authors.lastname: Hajjar
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH, USA.|Molecular Biology Division, Center for Basic Research, Foundation for Biomedical Research of the Academy of Athens, Athens, Greece.
authors.forename: Evangelia G
authors.initials: EG
authors.lastname: Kranias
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D006333:Heart Failure / Q000503:physiopathology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D051379:Mice; D035683:MicroRNAs / Q000502:physiology*; D009200:Myocardial Contraction / Q000502:physiology*; D060888:Real-Time Polymerase Chain Reaction; D015854:Up-Regulation / Q000502:physiology*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; C000600151:MIRN765 microRNA, human; D035683:MicroRNAs; C021042:protein phosphatase inhibitor-1; D002118:Calcium
keywords: Calcium cycling; Cardiomyocyte contractility; Heart failure; Inhibitor-1; MicroRNA-765; Protein phosphatase 1