Abstract 17053: Cardiac AKAP12 Signalosome Overexpression Exacerbation of Heart Failure and Cardiac Calcium Handling

Abstract

Introduction: Heart failure (HF) is responsible for 1 out of 8 deaths per year in the U.S.A. and is the major cause of death globally. Calcium cycling is crucial for proper signaling processes and efficient cardiac contraction. In failing hearts, remodeled calcium handling contributes to cardiac dysfunction. Previously we reported enhanced cardiac function in mice lacking a functional A-Kinase Anchoring Protein 12 (AKAP12). In this study, we aim to investigate the role of AKAP12 overexpression (oxAKAP12) on heart failure progression through assessing Sarco/Endoplasmic Reticulum Ca2+-ATPase (SERCA2) and its regulatory protein Phospholamban (PLN). Hypothesis: Cardiac AKAP12 overexpression potentiates HF development through its action on SERCA2. Methods: HF was developed in WT and oxAKAP12-Tg mice of 8-10 weeks old males and females, through chronic Isoproterenol (ISO) administration (60 mg/kg/day for 14-days). Left ventricular homogenates were used for gene expression analysis. Furthermore, AKAP12 was transiently overexpressed in AC16 cells (human cardiomyocytes cell line), to assess protein expression levels upon treatment with 100 nM of ISO for 12-hrs. Results: Cardiac oxAKAP12 in both males and females reduced left ventricular ejection fraction (EF) by 14.5±2.5% and fractional shortening (FS) by 22.7±2.0% after 14-days of chronic ISO treatment when compared to control groups. Both RNA sequencing and RTqPCR analysis showed a significant reduction of SERCA2 and PLN mRNA levels, respectively, in left ventricular homogenates of male (53.5±2.0%, 39.0±2.5%) and female (50.0±2.5%, 45.0±2.0%) groups overexpressing AKAP12 treated with ISO (14-days) compared to control groups (p<0.005). In AC16 cells overexpressing AKAP12 and treated with ISO, SERCA2 protein expression was reduced by 37% (p=0.0413) while PLN protein expression was not significantly reduced compared to control groups. Conclusions: Cardiac oxAKAP12 negatively influences systolic function in both male and female mice, potentially through affecting calcium handling, which will be assessed in future experiments by evaluating calcium transients and sarcomere shortening in isolated primary cardiomyocytes from oxAKAP12 and control mice.