Apoptotic cell death induced by intracellular proteolysis

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Cytotoxic lymphocytes induce target cell death via granzyme injection.
• Programmed cell death involves endogenous protease activation.
• Understanding protease roles in cell death is crucial for therapeutic development.

Purpose of the Study:

• To investigate the effects of introducing exogenous proteases into cell cytoplasm.
• To determine if exogenous proteases can induce cell lysis and apoptotic morphology.
• To assess the role of intracellular proteases in DNA fragmentation and cell death.

Main Methods:

• Osmotic lysis of pinosomes was used to introduce chymotrypsin, proteinase K, or trypsin into various cell types.
• Nuclear damage was quantified by measuring DNA release.
• Apoptotic features were assessed through DNA fragmentation, chromatin condensation, nuclear fragmentation, and membrane blebbing.
• Staphylococcal nuclease was introduced to induce DNA fragmentation.

Main Results:

• Intracellular proteases induced cell lysis and nuclear damage, including DNA fragmentation into nucleosomal ladders.
• Protease-induced cell death displayed features of apoptosis, such as chromatin condensation and membrane blebbing.
• Programmed cell death inhibitors did not prevent protease-induced cell death, though some affected nuclear damage.
• Staphylococcal nuclease induced extensive DNA fragmentation with a lag in membrane integrity loss.

Conclusions:

• Intracellular protease activation can trigger apoptotic morphology and DNA fragmentation, regardless of the initial molecular pathway.
• Exogenous proteases can effectively mimic granzyme-mediated cell killing.
• The findings highlight the central role of proteases in executing programmed cell death.