p38MAPK guards the integrity of endosomal compartments through regulating necrotic death

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• The innate immune system detects pathogens via specific receptors recognizing pathogen-associated molecular patterns (PAMPs).
• Mechanisms by which immune cells sense functional disruptions caused by pathogens are less understood.
• Cell death pathways are crucial for host defense against infection.

Purpose of the Study:

• To investigate how host cells sense pathogen-induced functional perturbations.
• To identify the molecular pathways involved in sensing endosomal damage.
• To explore the role of cell death in response to endosomal disruption.

Main Methods:

• Utilized macrophages challenged with bacteria and synthetic nanoparticles.
• Investigated the activation of p38MAPK kinase signaling.
• Examined cell death phenotypes in cells lacking key cell death mediators (caspases-1, -11, caspase-8, RIPK3).
• Assessed the role of Receptor-Interacting Protein Kinase 1 (RIPK1) in the observed cell death.

Main Results:

• Endosomal disruption by bacteria or nanoparticles activates p38MAPK kinase.
• p38MAPK activation leads to necrotic cell death, independent of pyroptosis, apoptosis, or necroptosis mediators.
• Receptor-Interacting Protein Kinase 1 (RIPK1) suppresses this p38MAPK-mediated necrosis.
• RIPK1 degradation sensitizes macrophages to necrotic death upon endosomal rupture.

Conclusions:

• Host cells possess a mechanism to sense functional perturbations, such as endosomal damage, as part of the innate immune response.
• p38MAPK-mediated necrosis represents a distinct cell death pathway activated by endosomal damage.
• RIPK1 plays a regulatory role in controlling necrotic cell death downstream of p38MAPK activation.