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Updated: May 30, 2025
Study of Phagolysosome Biogenesis in Live Macrophages
Published on: March 10, 2014
VPS18 contributes to phagosome membrane integrity in Mycobacterium tuberculosis-infected macrophages
Charul Jani1, Neha Jain1, Amanda K Marsh1
1The Ragon Institute of MGH, MIT and Harvard, Cambridge, MA 02139, USA.
Abstract:
Mycobacterium tuberculosis (Mtb) has evolved to be exquisitely adapted to survive within host macrophages. The capacity to damage the phagosomal membrane has emerged as central to Mtb virulence. While Mtb factors driving membrane damage have been described, host factors that maintain phagosomal integrity or repair Mtb-induced damage to contain the pathogen remain largely unknown. We used a genome-wide CRISPR screen to identify host factors required to repair Mtb-damaged phagosomal membranes. Vacuolar protein sorting-associated protein 18 (VPS18), a member of the HOPS and CORVET trafficking complexes, was among the top hits. VPS18 colocalized with Mtb in macrophages beginning shortly after infection, and VPS18-knockout macrophages demonstrated increased damage of Mtb-containing phagosomes without impaired autophagy. Mtb grew more robustly in VPS18-knockout cells, and the first-line antituberculosis antibiotic pyrazinamide was less effective. Our results identify VPS18 as required for phagosomal membrane integrity in Mtb-infected cells and suggest that modulating phagosome integrity may hold promise for improving the efficacy of antibiotic treatment for TB.
Insights
Host protein VPS18 is crucial for maintaining phagosome integrity against Mycobacterium tuberculosis (Mtb) infection. Its absence impairs bacterial containment and reduces antibiotic effectiveness, offering new therapeutic targets for tuberculosis.
Area of Science:
- Host-pathogen interactions
- Cell biology
- Immunology
Background:
- Mycobacterium tuberculosis (Mtb) thrives within macrophages by damaging phagosomal membranes.
- Host factors maintaining phagosome integrity against Mtb are largely unknown.
- Understanding these host factors is key to controlling Mtb infection.
Purpose of the Study:
- To identify host factors essential for repairing Mtb-induced phagosomal membrane damage.
- To investigate the role of identified factors in Mtb containment and antibiotic efficacy.
Main Methods:
- Genome-wide CRISPR screen in macrophages to identify host genes involved in phagosome repair.
- Confocal microscopy to assess VPS18 localization and phagosome integrity.
- Macrophage infection assays to evaluate Mtb growth and antibiotic response in VPS18-deficient cells.
Main Results:
- Vacuolar protein sorting-associated protein 18 (VPS18) was identified as a critical host factor for phagosomal membrane integrity.
- VPS18-deficient macrophages showed increased phagosome damage and impaired Mtb containment.
- Mtb grew more robustly in VPS18-knockout cells, and pyrazinamide efficacy was reduced.
Conclusions:
- VPS18 is required for maintaining phagosomal membrane integrity during Mtb infection.
- Targeting phagosome integrity could enhance the effectiveness of tuberculosis treatments.
- VPS18 represents a potential therapeutic target for improving anti-TB strategies.
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