Mitochondrial MsrB2 serves as a switch and transducer for mitophagy

Mitophagy can selectively remove damaged toxic mitochondria, protecting a cell from apoptosis. The molecular spatial-temporal mechanisms governing autophagosomal selection of reactive oxygen species (ROS)-damaged mitochondria, particularly in a platelet (no genomic DNA for transcriptional regulation), remain unclear. We now report that the mitochondrial matrix protein MsrB2 plays an important role in switching on mitophagy by reducing Parkin methionine oxidation (MetO), and transducing mitophagy through ubiquitination by Parkin and interacting with LC3. This biochemical signaling only occurs at damaged mitochondria where MsrB2 is released from the mitochondrial matrix. MsrB2 platelet-specific knockout and in vivo peptide inhibition of the MsrB2/LC3 interaction lead to reduced mitophagy and increased platelet apoptosis. Pathophysiological importance is highlighted in human subjects, where increased MsrB2 expression in diabetes mellitus leads to increased platelet mitophagy, and in platelets from Parkinson's disease patients, where reduced MsrB2 expression is associated with reduced mitophagy. Moreover, Parkin mutations at Met192 are associated with Parkinson's disease, highlighting the structural sensitivity at the Met192 position. Release of the enzyme MsrB2 from damaged mitochondria, initiating autophagosome formation, represents a novel regulatory mechanism for oxidative stress-induced mitophagy.