WASH-driven actin polymerization is required for efficient mycobacterial phagosome maturation arrest

Area of Science:

• Cell Biology
• Microbiology
• Immunology

Background:

• Pathogenic mycobacteria reside within host phagocytic cells, evading bactericidal mechanisms.
• The molecular basis for mycobacterial vacuole maintenance and survival remains incompletely understood.

Purpose of the Study:

• To elucidate the molecular mechanisms by which pathogenic mycobacteria establish and maintain their replicative niche within host cells.
• To investigate the role of actin dynamics in regulating the phagosomal environment for mycobacteria.

Main Methods:

• Combined molecular biology techniques and microscopy.
• Investigated the association of the WASH protein and F-actin with mycobacterial vacuoles.
• Assessed the impact of WASH disruption and F-actin depolymerization on vacuole acidification and bacterial viability.

Main Results:

• The actin nucleation-promoting factor WASH associates with the mycobacterial vacuole, promoting F-actin generation.
• Disruption of WASH or F-actin leads to V-ATPase accumulation, vacuole acidification, and reduced mycobacterial viability.
• This mechanism is conserved across different mycobacterial species (M. marinum, M. tuberculosis) and host cells (Dictyostelium, mammalian phagocytes).

Conclusions:

• Pathogenic mycobacteria subvert the host's WASH-mediated actin polymerization to prevent phagosome acidification.
• This evasion strategy is essential for creating and maintaining a replicative niche, promoting intracellular survival.
• The findings reveal an evolutionarily conserved mechanism of host-pathogen interaction crucial for mycobacterial pathogenesis.