MitoNEET dimerization uncouples mitochondria and reduces oxidative stress

Abstract

MitoNEET is a novel mitochondrial membrane protein that contains a 2Fe‐2S center and may be involved in regulating redox reactions. The goal of these studies was to determine if mitoNEET dimerization uncouples mitochondrial respiration and thereby reduces oxidative stress (ROS). A cell line, Swiss 3T3 cells, that does not express mitoNEET was transfected with mitoNEET cDNA and clonal lines established. In the absence of oxidative stress mitoNEET is a monomer, mitochondrial ROSs were low, and oxidative capacity was low. In the presence of exogenous oxidative stress such as hydrogen peroxide and peroxynitrate, mitoNEET dimerized, mitochondrial ROSs were high, and oxidative capacity was increased. Endogenously induced oxidative stress was generated by incubating the cells in high glucose (20 mM) or high fatty acids (0.5 mM). The cells responded similarly to endogenous oxidative stress as they did with exogenous oxidative stress. In contrast, cells that were not expressing mitoNEET underwent apoptosis when identical levels of oxidative stress were employed. Time course studies demonstrated that mitoNEET dimerized as ROS levels increased. This correlated with an increase in oxidative capacity and mitochondrial uncoupling. MitoNEET returned to a monomer as ROS levels decreased. These data suggest that the dimerization of mitoNEET plays a role in limiting mitochondrial ROS levels and cell apoptosis.