An emerging concept in recent biomedical research establishes that intrinsic membrane repair/regeneration is a fundamental aspect of normal human physiology and that disruption of this repair function underlies the progression of several pathologies, including cardiovascular diseases. We recently discovered that MG53, a muscle-specific TRIM-family protein, is an essential component of the acute membrane repair machinery in striated muscle. While genetic ablation of MG53 does not induce significant abnormality in young adult mice under non-stress conditions, increased susceptibility to ischemia and strenuous exercise-induced damage is evident in the MG53-/- hearts. Similar to skeletal muscle, damage to the cardiac membrane by mechanical, electrical or chemical insults leads to rapid translocation of MG53 toward the injury sites. The mg53-/- mice display arrhythmias even under normal physiological conditions, which may contribute to the elevated injury associated with stress. This stress-dependent cardiac phenotype raises the question how MG53 and other membrane repair molecules stand ready to rescue the cell from stress-induced membrane disruption as an emergency repair response. Aim 1 of our proposed studies will explore the mechanism underlying MG53-mediated repair of membrane damage to cardiomyocytes under conditions of ischemia, arrhythmias or acute injury, and establish that MG53 functions as an emergency response component for cardioprotection. MG53 contains the signature RING and B-Box motifs that constitute potential zinc (Zn) binding sites. Zn is one of the most abundant transition metals in the human body, and it is responsible for a wide range of biological functions including wound-healing. Several studies have linked Zn deficiency to cardiac dysfunction in conditions of ischemia-reperfusion and heart failure. Published studies from our group demonstrate that Zn has significant protective effect on acute myocardial infarction and arrhythmias, whereas the molecular mechanism underling cardioprotection by Zn is largely unknown. We have preliminary data to show that Zn-binding to MG53 plays a crucial role in MG53-mediated cell membrane repair. Aim 2 of our proposed studies will elucidate the molecular mechanism underlying the interaction of Zn with the RING/B-Box motifs of MG53 in regulating the nucleation process for MG53-mediated cell membrane repair in cardiac muscle. We anticipate that completion of the proposed studies will provide insights into the cardioprotective role of MG53 and its interaction with Zn in preventing damage to the cardiac membrane. Our studies will have broader impact on the basic biology of cell membrane repair and tissue regeneration, and have potential translational value for treatment of cardiovascular diseases.