Abstract
Necroptosis is a type of programmed cell death with great significance in many pathological processes. Tumour necrosis factor-α(TNF), a proinflammatory cytokine, is a prototypic trigger of necroptosis. It is known that mitochondrial reactive oxygen species (ROS) promote necroptosis, and that kinase activity of receptor interacting protein 1 (RIP1) is required for TNF-induced necroptosis. However, how ROS function and what RIP1 phosphorylates to promote necroptosis are largely unknown. Here we show that three crucial cysteines in RIP1 are required for sensing ROS, and ROS subsequently activates RIP1 autophosphorylation on serine residue 161 (S161). The major function of RIP1 kinase activity in TNF-induced necroptosis is to autophosphorylate S161. This specific phosphorylation then enables RIP1 to recruit RIP3 and form a functional necrosome, a central controller of necroptosis. Since ROS induction is known to require necrosomal RIP3, ROS therefore function in a positive feedback circuit that ensures effective induction of necroptosis.
Highlights
Necroptosis is a type of programmed cell death with great significance in many pathological processes
We found that butylated hydroxyanisole (BHA) and amytal can no longer inhibit cell death when autophosphorylation of serine residue 161 (S161) in receptor interacting protein 1 (RIP1) was prevented by E or N mutation in both Tumour necrosis factor (TNF)- and RIP1 oligomerization-induced cell death (Fig. 4e–g,i,j), indicating that reactive oxygen species (ROS) function to enhance RIP1 kinase activity and the subsequent S161 autophosphorylation
It was known that TNF-induced ROS production is RIP3 dependent[8], and ROS function in a positive feedback loop to enhance necrosome formation[22]
Summary
Necroptosis is a type of programmed cell death with great significance in many pathological processes. It is known that mitochondrial reactive oxygen species (ROS) promote necroptosis, and that kinase activity of receptor interacting protein 1 (RIP1) is required for TNF-induced necroptosis. The major function of RIP1 kinase activity in TNF-induced necroptosis is to autophosphorylate S161. This specific phosphorylation enables RIP1 to recruit RIP3 and form a functional necrosome, a central controller of necroptosis. During the process of necroptosis, RIP3 recruits and phosphorylates mixed lineage kinase domain-like protein (MLKL)[9,10]. We discovered that RIP1 can sense ROS via modification of three crucial cysteine residues and its autophosphorylation on S161 is induced subsequently This phosphorylation event allows efficient recruitment of RIP3 to RIP1 to form a functional necrosome. Our data uncovered RIP1 as the primary target of mitochondrial ROS in necroptosis, and solved a longstanding question of why RIP1 kinase activity is required for necroptosis
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