Noncanonical feedback loop between "RIP3-MLKL" and "4EBP1-eIF4E" promotes neuronal necroptosis

Stroke is a leading risk factor for disability and death. Necroptosis is involved in stroke pathogenesis. However, the molecular mechanisms underlying necroptosis in stroke remain unclear. The mammalian target of rapamycin complex 1 (mTORC1) modulates necroptosis in the gut epithelium. Eukaryotic translation initiation factor 4E (eIF4E)-binding protein-1 (4EPB1) is one of the main downstream molecules of mTORC1. This study addresses the role of the 4EBP1-eIF4E pathway in necroptosis. The 4EBP1-eIF4E pathway was found to be activated in both necroptotic HT-22 and mouse middle cerebral artery occlusion (MCAO) models. Functionally, 4EBP1 overexpression, eIF4E knockdown, and eIF4E inhibition suppressed necroptosis, respectively. Furthermore, a positive feedback circuit was observed between the 4EBP1-eIF4E and receptor-interacting protein-3 (RIP3)-mixed lineage kinase domain-like protein (MLKL) pathways, in which RIP3-MLKL activates the 4EBP1-eIF4E pathway by degrading 4EBP1 and activating eIF4E. This in turn enhanced RIP3-MLKL pathway activation. The eIF4E activation derived from this loop may stimulate cytokine production, which is a key factor associated with necroptosis. Finally, using a mouse MCAO model, the application of eIF4E, RIP3, and MLKL inhibitors was found to have a regulatory mechanism similar to that in the in vitro study, reducing the infarct volume and improving neurological function in MCAO mice.