Arginine methylation of caspase-8 controls life/death decisions in extrinsic apoptotic networks

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Procaspase-8 is central to death receptor-mediated apoptosis.
• Post-translational modifications (PTMs) of procaspase-8 are increasingly recognized for their role in regulating cell death.
• Understanding procaspase-8 regulation is crucial for cancer research.

Purpose of the Study:

• To investigate the role of post-translational modifications in procaspase-8 activation.
• To identify specific enzymes and sites involved in procaspase-8 modification.
• To explore the functional consequences of these modifications on apoptosis and cancer.

Main Methods:

• Mass spectrometry screening to identify potential modifications.
• Pharmacological inhibition of key enzymes.
• Biochemical assays to assess enzyme activity and protein interactions.
• In silico identification of potential methylation sites.
• Site-directed mutagenesis to study the effects of specific mutations.

Main Results:

• Procaspase-8 is targeted by the PRMT5/RIOK1/WD45 methylosome complex.
• Two key arginine residues (R233 and R435) on procaspase-8 were identified as potential PRMT5 methylation sites.
• Mutations at R233 and R435 inhibited CD95L-induced caspase-8 activity, effector caspase activation, and apoptosis.
• Procaspase-8 can undergo symmetric di-methylation.
• Pharmacological inhibition of PRMT5 reduced caspase activity and apoptotic cell death.

Conclusions:

• Arginine methylation by the PRMT5 complex represents a novel regulatory checkpoint for procaspase-8 activation.
• The identified methylation sites are conserved and their mutations are relevant to cancer.
• This work elucidates an arginine methylation network in extrinsic apoptosis, offering potential therapeutic targets.