Glutathione peroxidase-1 regulates ASK1-dependent apoptosis via interaction with TRAF2 in RIPK3-negative cancer cells

Area of Science:

• Biochemistry
• Cell Biology
• Cancer Research

Background:

• Glutathione peroxidase (GPx) enzymes, containing selenocysteine, protect cells from oxidative stress.
• The specific signaling roles of GPx family members, particularly GPx1, in apoptosis remain largely uncharacterized.

Purpose of the Study:

• To elucidate the regulatory role of GPx type 1 (GPx1) in the apoptosis signaling pathway.
• To investigate the molecular mechanisms by which GPx1 influences TNF-α-induced apoptosis and cancer cell proliferation.

Main Methods:

• Utilized various RIPK3-negative cancer cell lines to assess apoptosis.
• Quantified cytosolic hydrogen peroxide (H₂O₂) levels and analyzed the activation of JNK and caspase-8 signaling.
• Examined GPx1 interactions with thioredoxin 1 and TRAF2, and assessed ASK1 complex formation.
• Investigated the effect of inducible GPx1 knockdown on MDA-MB-231 tumor xenografts in mice.

Main Results:

• Absence of GPx1 significantly augmented TNF-α-induced apoptosis in cancer cells, linked to elevated mitochondrial-derived cytosolic H₂O₂.
• GPx1 deficiency resulted in sustained activation of JNK and caspase-8 signaling.
• GPx1 was found to regulate cytosolic H₂O₂ levels, affecting thioredoxin 1 oxidation and ASK1 activation, and to interact with TRAF2, inhibiting ASK1 complex formation.
• Inducible knockdown of GPx1 markedly impaired MDA-MB-231 tumor growth in vivo by promoting apoptosis.

Conclusions:

• GPx1 plays a critical role in regulating apoptosis signaling, acting as a negative regulator of TNF-α-induced cell death.
• GPx1 influences apoptosis through dual mechanisms involving H₂O₂ homeostasis and direct interaction with key signaling proteins like TRAF2.
• GPx1 deficiency promotes cancer cell apoptosis and inhibits tumor growth, highlighting its potential as a therapeutic target.