Abstract Body: Myocardial infarction (MI), which caused 110,000 deaths in America in 2020, occurs following a complete blockage (ischemia) in one or more of the coronary arteries. Additionally, clearing the blockage (reperfusion) causes massive cell death, resulting in permanent tissue damage in the heart. Preventing cell death in IR injury is key to improving patient outcome in this disease. Molecular chaperones have emerged as promising targets in IR injury due to their pro-survival functions. However, the role of Hsp90β, the most abundant and constitutively active chaperone, in IR injury has not been fully elucidated. Therefore, we generated a cardiac-specific Hsp90β conditional knockout (cKO) mouse model to address it. To our surprise, current preliminary results suggest that cardiac-specific Hsp90β ablation reduces myocardial damage during IR injury, as Hsp90β cKO mice showed reduced infarct size compared to control. Opening of the mitochondrial permeability transition pore (mPTP) is the major driver of necrotic cell death during early reperfusion. Isolated mitochondria from the hearts of Hsp90β cKO mice show decreased sensitivity to mPTP opening during calcium overload, suggesting that it may be one of the cardioprotective mechanisms mediated by Hsp90β ablation. The Hsp90β cKO hearts also display an anti-apoptotic shift of the BAX/BCL2 apoptotic rheostat, suggesting the heart will be more resistant to apoptotic cell death during late reperfusion phase as well. Findings from this study will help us understand the role of Hsp90β in cell death activation during IR injury. In the future, we plan to investigate the underlying protective mechanisms mediated by Hsp90β ablation.