title: Decoy peptides targeted to protein phosphatase 1 inhibit dephosphorylation of phospholamban in cardiomyocytes.
abstract: Cardiac sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2a) plays a crucial role in Ca(2+) handling in cardiomyocytes. Phospholamban (PLB) is an endogenous inhibitor of SERCA2a and its inhibitory activity is enhanced via dephosphorylation by protein phosphatase 1 (PP1). Therefore, the inhibition of PP1-mediated dephosphorylation of PLB might be an efficient strategy for the restoration of reduced SERCA2a activity in failing hearts. We sought to develop decoy peptides that would mimic phosphorylated PLB and thus competitively inhibit the PP1-mediated dephosphorylation of endogenous PLB. The phosphorylation sites Ser16 and Thr17 are located within the flexible loop region (amino acids 14-22) of PLB. We therefore synthesized a 9-mer peptide derived from this region (ΨPLB-wt) and two pseudo-phosphorylated peptides where Ser16 was replaced with Glu (ΨPLB-SE) or Thr17 was replaced with Glu (ΨPLB-TE). These peptides were coupled to the cell-permeable peptide TAT to facilitate cellular uptake. Treatment of adult rat cardiomyocytes with ΨPLB-SE or ΨPLB-TE, but not with ΨPLB-wt, significantly elevated the phosphorylation levels of PLB at Ser16 and Thr17. This increased phosphorylation of PLB correlated with an increase in contractile parameters in vitro. Furthermore, the perfusion of isolated rat hearts with ΨPLB-SE or ΨPLB-TE, but not with ΨPLB-wt, significantly improved left ventricular developed pressure that had been previously impaired by ischemia. These data indicate that ΨPLB-SE and ΨPLB-TE efficiently prevented dephosphorylation of PLB by serving as decoys for PP1. Therefore, these peptides may provide an effective modality to regulate SERCA2a activity in failing hearts.
authors.affiliation: Global Research Laboratory, Gwangju Institute of Science and Technology, Gwangju, South Korea.
authors.forename: Jae Gyun
authors.initials: JG
authors.lastname: Oh
authors.forename: Jihwa
authors.initials: J
authors.lastname: Kim
authors.forename: Seung Pil
authors.initials: SP
authors.lastname: Jang
authors.forename: Mai
authors.initials: M
authors.lastname: Nguen
authors.forename: Dong Kwon
authors.initials: DK
authors.lastname: Yang
authors.forename: Dongtak
authors.initials: D
authors.lastname: Jeong
authors.forename: Zee Yong
authors.initials: ZY
authors.lastname: Park
authors.forename: Sung-Gyoo
authors.initials: SG
authors.lastname: Park
authors.forename: Roger J
authors.initials: RJ
authors.lastname: Hajjar
authors.forename: Woo Jin
authors.initials: WJ
authors.lastname: Park
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D002316:Cardiotonic Agents / Q000737:chemistry / Q000494:pharmacology*; D002478:Cells, Cultured; D006333:Heart Failure / Q000188:drug therapy / Q000378:metabolism / Q000503:physiopathology; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008969:Molecular Sequence Data; D009200:Myocardial Contraction / Q000187:drug effects; D015428:Myocardial Reperfusion Injury / Q000188:drug therapy / Q000503:physiopathology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology*; D010766:Phosphorylation; D054645:Protein Phosphatase 1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D051381:Rats; D017207:Rats, Sprague-Dawley; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism; D000099211:Phospholamban
chemical_list: D002118:Calcium; D002135:Calcium-Binding Proteins; D002316:Cardiotonic Agents; D010446:Peptide Fragments; D054645:Protein Phosphatase 1; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000099211:Phospholamban; C582330:psiPLB-SE peptide; C582331:psiPLB-TE peptide