PLEKHO2 inhibits TNFα-induced cell death by suppressing RIPK1 activation

Area of Science:

• Cellular signaling pathways
• Molecular mechanisms of cell death
• Immunology and inflammation

Background:

• Receptor interaction protein kinase 1 (RIPK1) is a key regulator in TNFα signaling, influencing both NF-κB activation and programmed cell death.
• The precise mechanisms governing RIPK1's dual role in ubiquitination-dependent NF-κB activation and kinase-dependent apoptosis/necroptosis remain incompletely understood.

Purpose of the Study:

• To investigate the role of PH domain-containing family O member 2 (PLEKHO2) in regulating RIPK1-mediated signaling pathways.
• To elucidate PLEKHO2's function in TNFα-induced cell death, NF-κB activation, and inflammatory responses.

Main Methods:

• Utilized cell culture models with PLEKHO2 deficiency to assess susceptibility to TNFα-induced apoptosis and necroptosis.
• Employed RIPK1 kinase inhibitors to evaluate the contribution of RIPK1 activity to cell death.
• Analyzed RIPK1 ubiquitination and NF-κB activation in PLEKHO2-deficient cells.
• Investigated the in vivo effects of PLEKHO2 deficiency in a mouse model of TNFα-induced hepatitis.

Main Results:

• PLEKHO2 deficiency renders cells more vulnerable to TNFα-induced apoptosis and necroptosis, correlating with enhanced RIPK1 activation.
• The heightened cell death in PLEKHO2-deficient cells is mitigated by RIPK1 kinase inhibition.
• PLEKHO2 deficiency impairs RIPK1 ubiquitination and subsequent NF-κB activation following TNFα stimulation.
• PLEKHO2-deficient mice exhibit exacerbated hepatotoxicity and mortality in response to TNFα-induced hepatitis.

Conclusions:

• PLEKHO2 acts as a novel inhibitor of RIPK1-dependent apoptosis and necroptosis.
• PLEKHO2 plays a critical role in modulating RIPK1 ubiquitination and activation, thereby influencing NF-κB pathway signaling.
• PLEKHO2 is essential for preventing excessive cell death and hepatotoxicity in TNFα-mediated inflammatory conditions.