A synthetic lethal screen identifies FAT1 as an antagonist of caspase-8 in extrinsic apoptosis

Area of Science:

• Cell Biology
• Molecular Biology
• Cancer Research

Background:

• The extrinsic apoptosis pathway is crucial for programmed cell death, initiated by death ligands binding to death receptors.
• Formation of the death-inducing signaling complex (DISC) and activation of caspase-8 are key steps in this pathway.
• Dysregulation of apoptosis is implicated in diseases like cancer, particularly glioblastoma.

Purpose of the Study:

• To identify novel regulators of the extrinsic apoptosis pathway.
• To investigate the role of the atypical cadherin FAT1 in controlling caspase-8-dependent cell death.
• To explore FAT1 as a potential therapeutic target in glioblastoma.

Main Methods:

• Genome-wide siRNA screen to identify synthetic lethal interactions with death receptor-mediated apoptosis.
• Utilized established and patient-derived glioblastoma cell lines.
• Employed CRISPR/Cas9 gene editing to generate FAT1 knockout cell lines.
• Assessed apoptosis induction via cell death ligands and analyzed caspase-8 recruitment to the DISC.

Main Results:

• The atypical cadherin FAT1 was identified as an interactor of caspase-8, inhibiting its association with the DISC.
• Knockdown or knockout of FAT1 significantly sensitized glioblastoma cells to death ligand-induced apoptosis.
• Depletion of FAT1 led to enhanced procaspase-8 recruitment to the DISC and increased secondary signaling complex formation.

Conclusions:

• FAT1 acts as a negative regulator of the extrinsic apoptosis pathway by controlling caspase-8 activation.
• Targeting FAT1 enhances susceptibility to apoptosis in glioblastoma, suggesting its potential as a therapeutic strategy.
• These findings elucidate a novel mechanism for effector caspase regulation in physiological and pathological contexts.