Lipid droplets restrict phagosome formation in antifungal immunity

Area of Science:

• Immunology
• Cell Biology
• Infectious Diseases

Background:

• Lipid droplets (LDs) are intracellular organelles involved in cellular lipid metabolism.
• LDs interact with phagosomes during pathogen uptake by macrophages, but their functional role is unclear.
• Understanding LDs' role in phagocytosis is crucial for developing new anti-infective strategies.

Purpose of the Study:

• To investigate the function of lipid droplets (LDs) in modulating phagosome formation during fungal infection.
• To elucidate the molecular mechanisms by which LDs influence macrophage response to pathogens.
• To evaluate the therapeutic potential of targeting LDs in systemic fungal infections.

Main Methods:

• Utilized a fungal infection model (Candida albicans) in macrophages to study LDs and phagosome dynamics.
• Investigated the impact of LD accumulation on phagosome maturation and macrophage viability.
• Analyzed endoplasmic reticulum membrane dynamics, RAC1 translocation, and GTPase activity in response to LD formation.
• Assessed host susceptibility in mice with deficient macrophages and evaluated the efficacy of an ATGL inhibitor (atglistatin).

Main Results:

• LD accumulation was found to restrict phagosome formation and protect macrophages from cell death during fungal engulfment.
• Mechanistically, LD formation competed for endoplasmic reticulum membrane and altered RAC1 signaling, limiting phagosome development.
• Mice with Hilpda-deficient macrophages exhibited increased susceptibility to lethal Candida albicans infections.
• Treatment with the ATGL inhibitor atglistatin improved host survival in disseminated fungal infections.

Conclusions:

• Lipid droplets play a critical role in regulating phagosome formation and preventing immune cell death during fungal infections.
• The study reveals a novel mechanism involving LDs, endoplasmic reticulum, and RAC1 in controlling macrophage antifungal responses.
• Targeting LD metabolism, specifically via ATGL inhibition, presents a promising therapeutic strategy for treating systemic Candida albicans infections.