Abstract Background The EF-hand Ca 2+ sensor protein S100A1 has been identified as a molecular regulator and enhancer of cardiac performance. S100A1’s ability to recognize and modulate the activity of targets such as SERCA2a and RyR2 in cardiomyocytes has mostly been ascribed to its hydrophobic C-terminal α -helix (residues 75-94). Objective: We therefore hypothesized that a synthetic peptide consisting of residues 75-94 of S100A1 and an N-terminal solubilization tag (S100A1ct) could mimic the performance enhancing effects of S100A1 and may be suitable as a peptide therapeutic to improve the function of diseased hearts. Methods and Results: Applying an integrative translational research pipeline, ranging from computational molecular modeling to large animal cardiac disease models, we characterize S100A1ct as a cell-penetrating peptide with positive inotropic and antiarrhythmic properties in normal and failing myocardium in vitro and in vivo . This activity translates into improved contractile performance and survival in pre-clinical heart failure models with reduced ejection fraction after S100A1ct systemic administration. Mechanistically, S100A1ct exerts a fast and sustained dose-dependent enhancement of cardiomyocyte Ca 2+ cycling and prevents ß-adrenergic receptor triggered Ca 2+ imbalances by targeting SERCA2a and RyR2 activity. Modeling suggests that S100A1ct may stimulate SERCA2a by interacting with the sarcoplasmic transmembrane segments of the multi-span integral membrane Ca 2+ pump. Incorporation of a cardiomyocyte targeting peptide tag into S100A1ct (cor-S100A1ct) further enhanced its biological and therapeutic potency in vitro and in vivo . Conclusion: S100A1ct peptide is a promising lead for the development of a novel peptide-based therapeutic against heart failure with reduced ejection fraction.

S100A1ct: a synthetic peptide derived from human S100A1 protein improves cardiac contractile performance and survival in pre-clinical heart failure models