Integrated stress response restricts macrophage necroptosis

Area of Science:

• Cellular Biology
• Immunology
• Molecular Biology

Background:

• The integrated stress response (ISR) is crucial for maintaining cellular homeostasis and survival under stress.
• While the ISR modulates apoptosis and pyroptosis, its role in necroptosis remains unclear.
• Necroptosis is a pro-inflammatory programmed cell death pathway regulated by the RIPK3-MLKL signaling cascade.

Purpose of the Study:

• To investigate the role of the integrated stress response (ISR) in regulating necroptosis in macrophages.
• To elucidate the molecular mechanisms by which the ISR influences necroptosis susceptibility.

Main Methods:

• Macrophages were treated with ISR-inducing agents followed by necroptosis-inducing stimuli.
• Western blotting was used to assess the phosphorylation levels of key necroptosis pathway components (RIPK1, RIPK3, MLKL).
• Genetic manipulation, including stress granule disruption and gene knockdown (Perk), was employed to study ISR involvement.

Main Results:

• Macrophages pre-conditioned with ISR-inducing agents exhibited significant protection against necroptosis.
• Pre-treatment with ISR activators led to decreased phosphorylation of RIPK1, RIPK3, and MLKL upon necroptotic challenge.
• The stress granule protein DDX3X was not essential for ISR-mediated necroptosis protection, but disruption of stress granules or Perk knockdown restored necroptosis.

Conclusions:

• The integrated stress response (ISR) plays a critical role in limiting necroptosis in macrophages.
• ISR activation confers resistance to necroptosis, mediated in part by the regulation of the RIPK3-MLKL pathway.
• These findings highlight a novel regulatory mechanism of programmed cell death by the ISR, with implications for inflammatory diseases.