Mechanistic insights and cardiac targeting via tracheal delivery of a protein phosphatase 1 inhibitory peptide Taewon Kook College of Life Sciences and Medial Engineering Gwangju Institute of Science and Technology

Abstract

Heart failure (HF) remains a major cause of mortality worldwide. Despite advancements in medical treatments, current therapies primarily focus on symptom management rather than addressing the underlying molecular mechanisms of cardiac dysfunction, particularly impaired calcium handling. The sarcoplasmic reticulum Ca2+-ATPase (SERCA2a) plays a critical role in calcium regulation within cardiomyocytes, and its activity is tightly regulated by phospholamban (PLN), an endogenous inhibitor. Dephosphorylation of PLN at serine 16 (S16) by protein phosphatase 1 (PP1) exacerbates SERCA2a inhibition, contributing to calcium dysregulation and cardiac dysfunction in failing hearts. To counteract this, I utilized the therapeutic potential of a 9-mer peptide (RAE16TIEMPQ), referred to as SE, which is derived from the PLN protein sequence with a serine-to-glutamate substitution at S16. To enhance the delivery efficiency of SE to cardiac tissue, three strategies were explored: TANNylation, intratracheal (IT) injection, and optimization of the cell-penetrating peptide (CPP). TANNylation, achieved by conjugating SE with tannic acid (TA), was employed to enhance tissue-specific targeting and stability. IT injection, leveraging the lung-to-heart circulation, was investigated as a minimally invasive route that bypasses systemic dilution, improving cardiac delivery. Furthermore, the conventional TAT peptide was replaced with dNP2, a human-derived CPP known for superior translocation capabilities and reduced immunogenicity compared to TAT. These optimizations would not only enhance SE delivery efficiency but also prove its cardioprotective effects in vivo. Additionally, mechanistic investigations focused on the PP1c /PPP1R3A/PLN complex to elucidate how SE preserves PLN phosphorylation and mitigates cardiac dysfunction under myocardial infarction. Collectively, this research aims to establish the physiological consequence of peptide-mediated inhibition of PP1, providing a novel therapeutic approach for treating HF.