GCLC desuccinylation regulated by oxidative stress protects human cancer cells from ferroptosis

Tumor cells evolve strong antioxidant capacities to counteract the abnormal high level of reactive oxygen species (ROS) in the tumor microenvironment. Glutamate-cysteine ligase catalyzing subunit (GCLC) for synthesis of antioxidant glutathione (GSH) represents the key enzyme to maintain redox homeostasis of tumor cells, however, whether its activity is regulated by posttranslational modifications, such as succinylation, remains to be clarified. Here, we demonstrate the existence of succinylation modification on GCLC by in vitro and in vivo assays. NAD-dependent deacetylase Sirtuin-2 (SIRT2) serves as the desuccinylase and catalyzes GCLC desuccinylation at sites of K38, K126, and K326. Specifically, GCLC directly interacts with SIRT2, which can be substantially enhanced upon ROS treatment. This strengthened association results in GCLC desuccinylation and activation, consequently promoting GSH synthesis and rendering cancer cells resistant to ferroptosis induction. Depletion of SIRT2 decreases total GSH level and meanwhile increases the cellular susceptibility to ferroptosis, which can mostly be rescued by introducing wild-type GCLC, but not its 3K-E mutant. We further demonstrated that histone acetyltransferase P300 serves as the succinyltransferase of GCLC, and their association is remarkably decreased after ROS treatment. Thus, SIRT2-regulated GCLC succinylation represents an essential signaling axis for cancer cells to maintain their redox balance in coping with oxidative stress-induced ferroptosis.