Abstract P1055: Co-chaperone Bag5 Protects Cardiomyocytes From Oxidative Stress

Introduction: Cardiovascular disease is one of the leading causes of death globally. Cardiac ischemic can alter cellular homeostasis and potentially lead to heart failure. Ischemic cells modulate the expression of molecular chaperones, which assist with the folding/refolding of cellular proteins. Specifically, the heat-shock protein 70 (Hsp70) chaperone, and its co-chaperones in the Bcl-2-associated athanogene (BAG) protein family, help maintain protein homeostasis by protein folding and degradation. This project serves to explore the role of BAG5 in cardiac ischemia. Methods: Expression of BAG5 was determined in left ventricular tissue isolated from cardiomyopathy patients and in ischemic cardiomyocytes. Co-immunoprecipitation (IP) and mass spectrometry analysis were utilized to determine potential interacting partners of BAG5. For the generation of ischemic conditions, neonatal rat cardiomyocytes were incubated in a hypoxia chamber for 12 hours in DMEM media with no glucose, 0% serum, and 0.1% O2. The role of BAG5 in cellular viability, reactive oxygen species (ROS) production, and proteostasis during ischemia was determined through gain-in and knock-down approaches using adenoviruses. In addition, mitochondrial membrane potential and ROS production were determined by the TMRE and MitoSOX red staining, respectively. Mitochondrial function was determined by a Seahorse XF assay. Results: Co-immunoprecipitation and mass spectrometry analysis revealed that BAG5 interacts with Myosin and Hsp70. Expression of BAG5 in cardiomyocytes was significantly decreased during ischemia. Further, overexpression of BAG5 protects cardiomyocytes by inhibiting excessive autophagy and reducing ROS production. Moreover, BAG5 expression improves mitochondrial function during ischemia. Conclusion: Understanding the role of BAG5 within the cell may help establish the protein as a potential therapeutic molecule for the protection of the ischemic heart.