SUMO1 Modification Regulates SR Calcium ATPase Pump, SERCA2a in Heart Failure

Abstract

Background: The cardiac calcium ATPase, SERCA2a, is a critical pump responsible for Ca2+ re-uptake during excitation-contraction coupling. Impaired Ca2+ uptake resulting from decreased expression and reduced activity of SERCA2a is a hallmark of heart failure. Accordingly, restoration of SERCA2a expression by gene transfer has proved to be effective in improving cardiac function in heart-failure patients, as well as in animal models. However, the underlying mechanisms of SERCA2a’s dysfunction remain incompletely understood. Methods and Results: In this study, we show that SERCA2a is modified by SUMO1 at lysine sites 480 and 585 and that this SUMOylation is essential for preserving SERCA2a ATPase activity and stability in mouse and human cells. SUMO1 and SERCA2a SUMOylation levels were both decreased in mouse and pig models of heart failure and failing human left ventricles. To determine whether reduced SUMO1 levels are responsible for reduced SERCA2a protein levels and reduced cardiac function, we used an adenovirus associated virus-mediated gene delivery approach to up-regulate SUMO1 in trans aortic constriction-induced mouse model of heart failure. We found that increasing SUMO1 levels led to a restoration of SERCA2a levels, improved hemodynamic performance, and reduced mouse mortality. By contrast, down-regulation of SUMO1 using small hairpin RNA accelerated cardiac functional deterioration and was accompanied by decreased SERCA2a function. Conclusion: In this study, we study a new mechanism for modulation of SERCA2a activity and beneficial effects of SUMO1 in the setting of heart failure. It suggests that changes in post-translational modifications of SERCA2a could negatively affect cardiac function in heart failure. Our data may provide a new platform for the design of therapeutic strategies for heart failure.