Abstract 17721: Loss of p22 phox Exacerbates Heart Failure Through Increased Oxidation and Proteasomal Degradation of SERCA2a

Abstract

Introduction: Downregulation of sarcoplasmic/endoplasmic reticulum (SR/ER) Ca2+ ATPase 2a (SERCA2a) accentuated by oxidative stress is a major driver of heart failure. NADPH oxidase (NOX) complexes are the key sources of reactive oxygen species (ROS) in cardiomyocytes. p22 phox , a transmembrane partner of NOX1-4, plays an essential role in mediating ROS production in multiple NOX complexes. We investigated the role of p22 phox in oxidative stress and SERCA2a levels during pressure overload (PO). Question: Does loss of p22 phox alleviate heart failure through reduction of oxidative stress and stabilization of SERCA2a levels during PO? Methods: Cardiac-specific p22 phox knockout ( p22 phox -cKO) mice were subjected to sham operation or transverse aortic constriction (TAC). The p22 phox interactome was analyzed by co-immunoprecipitation and mass spectrometry. Protein cysteine oxidation was probed by biotinylated iodoacetamide labelling. Results: The p22 phox -cKO mouse heart showed a 50% reduction in H 2 O 2 levels compared to WT after 1-week TAC (p<0.01). Unexpectedly, p22 phox -cKO mice had 20% higher mortality (p<0.05), lung congestion (2-fold, p<0.05), and fibrosis (>40%, p<0.01) and a lower (40%, p<0.01) left ventricle ejection fraction than WT after TAC. p22 phox directly interacted with SERCA2a. Lack of p22 phox led to oxidation of SERCA2a at cysteine 498 and promoted degradation of SERCA2a. SERCA2a C498S knock-in mice have better cardiac function and stable SERCA2a protein levels after TAC compared to WT mice. Further, p22 phox aided thioredoxin 1 (TRX-1) interaction with SERCA2a and prevented cysteine oxidation. SERCA2a was co-immunoprecipitated with Smad ubiquitination regulatory factor 1 (Smurf1) and HMG-CoA reductase degradation protein 1 (Hrd1) E3 ubiquitin ligases in the absence of p22 phox or TRX-1. Conclusion: p22 phox recruits TRX-1 to SERCA2a, prevents SERCA2a cysteine 498 oxidation, promotes its stability, and maintains cardiac function.