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Effects of lysosomal membrane protein depletion on the Salmonella-containing vacuole

Everett A Roark1, Kasturi Haldar

  • 1Department of Microbiology-Immunology, Northwestern University, Chicago, Illinois, USA.

Plos One
|October 30, 2008
PubMed

Insights

Salmonella bacteria use host cell vacuoles for replication. While lysosomal membrane protein 1 (LAMP-1) is abundant, lysosomal membrane protein 2 (LAMP-2) appears partially important for the Salmonella-containing vacuole.

Area of Science:

  • Microbiology
  • Cell Biology
  • Pathogen-Host Interactions

Background:

  • Salmonella Typhimurium is an intracellular pathogen that resides within a vacuole in host cells.
  • Lysosomal membrane proteins 1 and 2 (LAMP-1 and LAMP-2) are recruited to the Salmonella-containing vacuole and associated filaments (Sifs).
  • LAMP-1 is a primary marker for the vacuole and Sifs, with its localization dependent on the bacterial virulence protein SifA.

Purpose of the Study:

  • To investigate the role of SifA in the recruitment of LAMP-2 to the Salmonella-containing vacuole.
  • To evaluate LAMP-2 as an independent marker for the Salmonella-containing vacuole and Sifs.
  • To determine the essentiality of LAMP-1 and LAMP-2 for maintaining the integrity of the Salmonella-containing vacuole.

Main Methods:

  • Immunofluorescence microscopy to visualize LAMP-1 and LAMP-2 localization.
  • RNA interference (RNAi) to deplete LAMP-1 and LAMP-2 levels in host cells.
  • Bacterial association assays to quantify membrane-bound Salmonella.

Main Results:

  • SifA is essential for LAMP-2 recruitment to the Salmonella-containing vacuole and Sifs.
  • LAMP-2 can serve as an independent marker for the vacuolar membrane and Sifs.
  • Depletion of LAMP-1 did not prevent Salmonella from remaining membrane-bound (marked by LAMP-2).
  • Depletion of LAMP-2 led to an increase in LAMP-1-free Salmonella, suggesting partial importance.

Conclusions:

  • LAMP-1, despite its abundance, is not essential for the Salmonella-containing vacuolar membrane.
  • LAMP-2 plays a partially important role in maintaining the Salmonella-containing vacuolar membrane.
  • SifA's role extends to the recruitment of LAMP-2, highlighting its significance in Salmonella vacuole biogenesis.

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