Proteasome inhibition blocks necroptosis by attenuating death complex aggregation

Area of Science:

• Cellular Biology
• Oncology
• Immunology

Background:

• Proteasome inhibitors are clinically successful cancer therapeutics that induce cell death.
• The ubiquitin-proteasome system regulates apoptosis and necroptosis signaling pathways.
• Cellular inhibitor of apoptosis proteins (cIAPs) are key regulators in TNF-mediated cell death.

Purpose of the Study:

• To investigate the role of necroptosis in cell death induced by the proteasome inhibitor Carfilzomib (Cf).
• To determine if Cf treatment affects necroptosis signaling components and their interactions.

Main Methods:

• Treatment of multiple myeloma cell lines and HT-29 cells with Carfilzomib.
• Analysis of cell death markers (apoptosis and necroptosis).
• Assessment of RIPK1-TNFR1 interactions and translocation of death signaling components.

Main Results:

• Carfilzomib induced apoptosis and serine protease-dependent death, but not RIPK3-dependent necroptosis.
• Cf treatment led to increased apoptotic markers (caspase-3) and decreased necroptotic markers (phosphorylated-MLKL).
• Cf impaired TNF-induced necroptosis by attenuating RIPK1 interaction with TNFR1 and decreasing the translocation of key signaling proteins.

Conclusions:

• Proteasome inhibition with Carfilzomib favors apoptosis over necroptosis, even in cells with intact necroptotic machinery.
• Proteasome activity is crucial for the stabilization and activation of necrosome complexes during TNFR1-mediated necroptosis.