Decoy peptides inhibiting protein phosphatase 1-medicated dephosphorylation of phospholamban

A method for treating a disease associated with phospholamban (PLB) selected from the group consisting of heart failure, congestive heart failure, and ischemia, the method comprising administering to a subject in need thereof,

• (a) a pharmaceutically effective amount of a decoy peptide consisting of the peptide sequence represented by the following Formula I:
• X1-Ala-X2-X3-Ile-Glu-X4 (1)
• wherein X1 represents 0-1 amino acid residue(s), X2 represents Ser, Glu, or Asp, X3 represents Thr, Glu, or Asp and X4 represents 0-3 amino acid residue(s), with the proviso that X2 is not Ser when X3 is Thr;
• wherein the decoy peptide inhibits protein phosphatase 1 (PP1)-mediated dephosphorylation of PLB by competitive inhibition, wherein neither X1 nor X4 comprise membrane-spanning domains and X1 is not Tyr, and wherein the decoy peptide is linked to a cell membrane-permeable peptide;
• and (b) a pharmaceutically acceptable carrier.