Fmp40 ampylase regulates cell survival upon oxidative stress by controlling Prx1 and Trx3 oxidation

Reactive oxygen species (ROS), play important roles in cellular signaling, nonetheless are toxic at higher concentrations. Cells have many interconnected, overlapped or backup systems to neutralize ROS, but their regulatory mechanisms remain poorly understood. Here, we reveal an essential role for mitochondrial AMPylase Fmp40 from budding yeast in regulating the redox states of mitochondrial 1-Cys peroxiredoxin, Prx1, which is the only protein shown to neutralize H ₂ O ₂ with the oxidation of the mitochondrial glutathione and Trx3, thioredoxin, directly involved in the reduction of Prx1. Deletion of FMP40 impacts a cellular response to H ₂ O ₂ treatment that leads to programmed cell death (PCD) induction and an adaptive response involving up or down regulation of genes encoding, among others the catalase Cta1, PCD inducing factor Aif1, and mitochondrial redoxins Trx3 and Grx2. This ultimately perturbs the reduced glutathione and NADPH cellular pools. We further demonstrated that Fmp40 AMPylates Prx1, Trx3, and Grx2 in vitro and interacts with Trx3 in vivo . AMPylation of the threonine residue 66 in Trx3 is essential for this protein’s proper endogenous level of and its precursor forms’ maturation under oxidative stress conditions. Additionally, we showed the Grx2 involvement in the reduction of Trx3 in vivo . Taken together, Fmp40, through control of the reduction of mitochondrial redoxins, regulates the hydrogen peroxide, GSH and NADPH signaling influencing the programmed cell death execution.