Abstract 19852: PDE3A Binds Directly to and Inhibits SERCA2 Activity Independently of its Catalytic Activity

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Introduction: SERCA2 controls cardiac contractility, and its activity is negatively regulated by the cAMP phosphodiesterase PDE3A through an unknown mechanism. Several preclinical trials have shown upregulation of SERCA2 gene therapy as beneficial in heart failure, but no specific SERCA2 activating agents have been reported.

Hypothesis: We propose that PDE3A is physically associated with SERCA, and that this interaction regulates SERCA2 activity independent of the cAMP-degrading properties of PDE3A.We also wanted to evaluate whether this protein-protein interaction represent a novel drug target to increase SERCA2 activity in heart failure.

Methods and Results: SERCA2 activity in PDE3A-transefected HEK293 vesicles was reduced compared to control. PDE3A also reduced SERCA2 activity in the presence of the PDE3A inhibitor Cilostamide, showing that PDE3A inhibits SERCA2 independently of its catalytic effect. A combination of immunoprecipitation and peptide interaction experiments revealed interaction between specific cytosolic regions on PDE3A and SERCA2. Active PDE3A co-purified and precipitated with SERCA2 from left ventricular myocardium, and proximity ligation assay demonstrated co-localization of PDE3A and SERCA2 in intact cardiomyocytes. SERCA2 activity assays in adult cardiomyocytes revealed increased SERCA2 activity by intracellular and extracellular administration of disruptor peptides of the SERCA2-PDE3A interaction, independent of protein kinas A and phospholamban. PDE3A-SERCA2 disruptor peptides were able to increase SERCA2 activity and prevent spontaneous contractions in ventricular myocytes from mice with chronic heart failure.

Conclusion: PDE3A is physically associated to SERCA2, and this direct interaction inhibits SERCA2 activity. Cell permeable disruptor peptides of the PDE3A-SERCA2 protein-protein interaction are able to increase SERCA2 activity in both normal and failing adult cardiomyocytes. Specific disruption of PDE3A from SERCA2 may potentially offer a new therapeutic approach against arrhythmias and in chronic heart disease.

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