Overexpression of myristoylated methionine sulfoxide reductase A in the mouse protects the heart against ischemia‐reperfusion injury

Abstract

Methionine sulfoxide reductase A (MsrA) has been reported to function as an antioxidant protein, either by scavenging reactive oxygen species via cyclic interconversion of the reduced and oxidized forms of methionine residues or by protecting critical protein residues from oxidation. However, the mechanisms and requirements for providing an effective oxidative defense in vivo are not known. In mammalian cells, ~75% of MsrA is located in the cytosol and is myristoylated while ~25% is in the mitochondria and not myristoylated. We created several strains of transgenic mice overexpressing MsrA directed to the cytosol or mitochondria or both. Quantitative Western blotting and activity measurements demonstrated a high level of functional MsrA in most tissues tested, with the highest in the heart. We tested whether the increased MsrA in heart protected against ischemia‐reperfusion injury in a Langendorff model. We found that MsrA overexpression in the cytosol but not in the mitochondria protected. We then examined whether myristoylation affected this protection. We created another transgenic mouse overexpressing MsrA only in the cytosol, but in this strain glycine at position 2 was mutated to alanine to prevent myristoylation. Analysis of heart tissue confirmed that the overexpressed MsrA was active but not myristoylated. However, this non‐myristoylated MsrA heart experienced no protection. These experimental results indicate that myristoylation of cytosolic MsrA is key to its ability to provide cardioprotection.This research was supported by the Intramural Research Program of the NIH, NHLBI.