eIF2α Confers Cellular Tolerance to S. aureus α-Toxin

Area of Science:

• Cellular Biology
• Microbiology
• Immunology

Background:

• Pore-forming toxins, such as Staphylococcus aureus α-toxin, pose a significant threat to cellular integrity.
• Cellular stress-response pathways are crucial for maintaining homeostasis under adverse conditions.
• The receptor mediating α-toxin entry into cells is still under investigation, with ADAM10 being a proposed candidate.

Purpose of the Study:

• To investigate the role of conserved stress-response pathways in conferring cellular tolerance to pore-forming toxins.
• To elucidate the specific mechanisms and pathways involved in α-toxin resistance.
• To determine the cell-type specificity and toxin selectivity of these stress-induced tolerance mechanisms.

Main Methods:

• Utilized mouse embryonal fibroblasts (MEFs) with wild-type and mutated eukaryotic translation initiation factor 2α (eIF2α) (S51A/S51A).
• Employed small molecular weight inhibitors targeting eIF2α-phosphatase, jun-N-terminal kinase (JNK), and PI3-kinase.
• Assessed cellular sensitivity to Staphylococcus aureus α-toxin and Vibrio cholerae cytolysin.
• Quantified ADAM10 expression and toxin binding in different cell lines.
• Investigated the role of GCN2 kinase in basal eIF2α phosphorylation and stress tolerance.

Main Results:

• Inhibitors of eIF2α-phosphatase, JNK, and PI3-kinase sensitized normal MEFs to S. aureus α-toxin, dependent on ADAM10 expression.
• eIF2α (S51A/S51A) MEFs, lacking eIF2α phosphorylation, were hyper-sensitive to α-toxin but not to Vibrio cholerae cytolysin, indicating toxin selectivity.
• Mutant cells exhibited enhanced α-toxin binding and toxicity, with increased ADAM10 levels.
• Basal eIF2α phosphorylation, mediated by GCN2 kinase, conferred tolerance to α-toxin in MEFs.
• Macrophages displayed robust α-toxin tolerance independent of GCN2, but JNKs played a role, suggesting cell-type specific responses.

Conclusions:

• Conserved stress-response pathways, particularly involving eIF2α phosphorylation via GCN2, are critical for mediating cellular tolerance to S. aureus α-toxin.
• ADAM10 modulation is implicated in this α-toxin tolerance mechanism.
• The observed tolerance is selective for α-toxin and not other pore-forming toxins like V. cholerae cytolysin.
• Stress responses exhibit differential cell-type and toxin selectivity, impacting anti-bacterial immune responses.