ROS signaling-induced mitochondrial Sgk1 regulates epithelial cell plasticity

Many types of differentiated cells can reenter the cell cycle upon injury or stress. The mechanisms underlying this cell plasticity are still poorly understood. Here we investigated cell plasticity regulation using a zebrafish model, in which a population of differentiated epithelial cells are reactivated under a physiological context. We observed a robust and sustained increase in mitochondrial membrane potential in reactivated cells. Genetic and pharmacological perturbations show that elevated mitochondrial metabolism and ATP synthesis are critical for cell reactivation. Elevated mitochondrial metabolism increases mitochondrial ROS levels, which induces Sgk1 expression in the mitochondria. Deletion and inhibition of Sgk1 in zebrafish abolished cell reactivation. Similarly, ROS-dependent mitochondrial expression of SGK1 promotes S phase entry in human breast cancer cells. Mechanistically, Sgk1 coordinates mitochondrial activity with ATP synthesis by modulating F1Fo-ATP synthase phosphorylation. These findings suggest a conserved intramitochondrial signaling loop regulating epithelial cell renewal. One sentence highlightThis study reports a new intramitochondrial signaling loop regulating epithelial cell renewal.