Increased Neprilysin (NEP) in Failing Hearts Cleaves Phospholamban (PLB), Dysregulating SERCA and Cardiac Function
Background
Current heart failure therapies often target Neprilysin (NEP) to prevent the degradation of circulating cardioprotective peptides. However, a direct role for NEP in ventricular muscle pathophysiology has been unclear. This enzyme is known to cleave sarcolipin (SLN), a micropeptide regulator of the sarcoplasmic reticulum Ca2+-ATPase (SERCA). Understanding NEP's direct impact on cardiac calcium handling and SERCA regulation within cardiomyocytes could reveal novel mechanisms of disease progression and therapeutic targets, addressing a critical gap in our understanding of heart failure at the cellular level.
Study Design
Researchers quantified NEP abundance in failing and non-failing human myocardial specimens using proteomics and immunoblot analysis. They then used heterologous protein expression and biochemical binding assays to assess NEP-mediated cleavage of phospholamban (PLB) and its effect on PLB-SERCA interactions. Functional consequences of NEP expression or inhibition were investigated in neonatal rat ventricular myocytes (NRVMs) and a human induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM) model of heart failure. The study examined Ca2+ transient kinetics and SR Ca2+ load.
Results
The study observed increased NEP abundance in failing human myocardium compared to non-failing controls. Crucially, they demonstrated that NEP cleaves phospholamban (PLB), which directly disrupts PLB-SERCA interactions. Mutation of PLB at V49A prevented NEP cleavage and preserved PLB-SERCA binding, indicating that V49 is critical for NEP substrate recognition. In neonatal rat ventricular myocytes, NEP expression was associated with faster Ca2+ transient decay kinetics and increased SR Ca2+ load, consistent with reduced SERCA inhibition. This suggests that NEP activity can directly impact cardiac Ca2+ handling. > Inhibition of NEP in a hiPSC-CM heart failure model attenuated the hypertrophic transcriptional responses and reversed Ca2+-transport dysregulation, highlighting a direct therapeutic potential. These findings implicate increased NEP expression in the sarcoplasmic reticulum of cardiomyocytes as a previously unrecognized maladaptive consequence of heart failure.
Key Findings
- Neprilysin (NEP) abundance is increased in failing human myocardium compared to non-failing controls.
- NEP directly cleaves phospholamban (PLB), disrupting
PLB-SERCAinteractions. - A V49A mutation in PLB prevents NEP cleavage, preserving
PLB-SERCAbinding. - NEP expression in rat myocytes leads to faster Ca2+ transient decay and increased SR Ca2+ load.
- NEP inhibition in hiPSC-CMs attenuates hypertrophic responses and reverses
Ca2+-transport dysregulation.
Why It Matters
This research uncovers a novel, direct mechanism by which Neprilysin (NEP) contributes to heart failure pathophysiology, moving beyond its established role in degrading circulating vasoactive peptides. Targeting NEP directly within cardiomyocytes could offer a new therapeutic avenue for heart failure, potentially by preserving PLB-SERCA interactions and improving Ca2+ handling. For peptide users and clinicians, this suggests that existing NEP inhibitors might have additional, previously unrecognized benefits at the cellular level, or that new, more targeted NEP inhibitors could be developed to specifically address this intracellular mechanism. This finding provides a deeper understanding of cardiac dysfunction, potentially refining future treatment strategies for heart failure patients.
neprilysin
heart-failure
phospholamban
serca
calcium-handling
cardiac-dysfunction