AMPK-Mediated BECN1 Phosphorylation Promotes Ferroptosis by Directly Blocking System Xc– Activity

Abstract

Ferroptosis is a form of regulated cell death triggered by lipid peroxidation after inhibition of the cystine/glutamate antiporter system X. However, key regulators of system X activity in ferroptosis remain undefined. Here, we show that BECN1 plays a hitherto unsuspected role in promoting ferroptosis through directly blocking system Xc activity via binding to its core component, SLC7A11 (solute carrier family 7 member 11). Knockdown of BECN1 by shRNA inhibits ferroptosis induced by system X inhibitors (e.g., erastin, sulfasalazine, and sorafenib), but not other ferroptosis inducers including RSL3, FIN56, and buthionine sulfoximine. Mechanistically, AMP-activated protein kinase (AMPK)-mediated phosphorylation of BECN1 at Ser90/93/96 is required for BECN1-SLC7A11 complex formation and lipid peroxidation. Inhibition of PRKAA/AMPKα by siRNA or compound C diminishes erastin-induced BECN1 phosphorylation at S93/96, BECN1-SLC7A11 complex formation, and subsequent ferroptosis. Accordingly, a BECN1 phosphorylation-defective mutant (S90,93,96A) reverses BECN1-induced lipid peroxidation and ferroptosis. Importantly, genetic and pharmacological activation of the BECN1 pathway by overexpression of the protein in tumor cells or by administration of the BECN1 activator peptide Tat-beclin 1, respectively, increases ferroptotic cancer cell death (but not apoptosis and necroptosis) in vitro and in vivo in subcutaneous and orthotopic tumor mouse models. Collectively, our work reveals that BECN1 plays a novel role in lipid peroxidation that could be exploited to improve anticancer therapy by the induction of ferroptosis.

ATM ‐ CHK 2‐Beclin 1 axis promotes autophagy to maintain ROS homeostasis under oxidative stress

“…These results are consistent with the previous observations that the phosphorylation of Beclin 1 at Ser90/93 (Fogel et al , ) or monophosphorylation of Beclin 1 at Ser90 (Wei et al , ; Fujiwara et al , ; Li et al , ) positively regulates autophagy. It should be noted that some studies found an autophagy‐independent role for Beclin 1 phosphorylation at Ser90/93/96 by AMPK, which enables Beclin 1 to interact with SLC7A11 and initiate ferroptosis, a type of programmed cell death (Song et al , ). The basis for whether Beclin 1 phosphorylation triggers autophagy or ferroptosis remains unknown, but could relate to the intensity or duration of the perturbation.…”

Branched chain amino acid aminotransferase 2 Regulates Ferroptotic Cell Death in Cancer Cells

“…Next, we would like to understand how AMPK/SREBP1 is activated by ferroptosis inducers. As AMPK is a promoter of autophagy and ferroptosis is an autophagic cell death process called ferritinophagy (Gao, Monian et al, 2016, Song, Zhu et al, 2018, we asked whether ferritinophagy is involved in AMPK activity. Nuclear receptor coactivator 4 (NCOA4) was a selective cargo receptor for the selective autophagic turnover of ferritin .…”

The Role of Beclin 1-Dependent Autophagy in Cancer

“…Thus, Beclin 1 phosphorylation by AMPK at S90, S93, S96 regulates ferroptosis, an iron-dependent cell death, upon binding to SLC7A11 (solute carrier family 7 member 11). Indeed, Beclin 1 overexpression or Tat-Beclin 1 treatment increases ferroptosis cell death and decreases tumor growth in vivo [60]. However, the direct effects of these serine phosphorylation events by AMPK require further investigation.…”