PUMA dependent mitophagy by Abrus agglutinin contributes to apoptosis through ceramide generation

Area of Science:

• Cell Biology
• Molecular Oncology
• Cancer Therapeutics

Background:

• PUMA (protein upregulated in mdm2 null apoptosis) is a pro-apoptotic BH3-only protein.
• PUMA translocation to mitochondria induces apoptosis, playing a key role in DNA damage response.
• U87MG glioblastoma cells are a relevant model for studying cell death pathways.

Purpose of the Study:

• To investigate the mitophagy-inducing potential of phytolectin Abrus agglutinin (AGG) in U87MG glioblastoma cells.
• To elucidate the molecular mechanisms underlying AGG-induced mitophagy, focusing on PUMA's role.
• To explore the therapeutic implications of AGG-induced mitophagy in cancer treatment.

Main Methods:

• Cell culture of U87MG glioblastoma cells.
• Analysis of PUMA expression and localization.
• Assessment of mitophagy using LC3 and p62 markers.
• Measurement of reactive oxygen species (ROS) and endoplasmic reticulum (ER) stress.
• Gain and loss of function studies for PUMA.
• Inhibition of DRP1 using Mdivi-1.

Main Results:

• AGG upregulates PUMA expression in U87MG cells, leading to mitochondrial dysfunction and mitophagy.
• AGG-induced ceramide is a key mediator, activating mitochondrial ROS and ER stress.
• PUMA interacts with LC3 via its LIR motif and with p62, promoting mitophagy in both p62-dependent and -independent manners.
• AGG-triggered ceramide production activates ceramide synthase-1, inducing ER stress and ROS accumulation.
• Inhibition of DRP1 suppresses AGG-induced apoptosis, suggesting a switch from mitophagy to apoptosis.

Conclusions:

• AGG activates PUMA-mediated mitophagy in U87MG glioblastoma cells.
• Ceramide, ER stress, and ROS are crucial mediators of AGG-induced mitophagy and cell death.
• PUMA's interaction with LC3 and p62 is essential for mitophagy induction.
• Targeting AGG-induced mitophagy presents a potential therapeutic strategy for glioblastoma.