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Distinct Mycobacterium marinum phosphatases determine pathogen vacuole phosphoinositide pattern, phagosome

Hendrik Koliwer-Brandl1, Paulina Knobloch1, Caroline Barisch2

  • 1Faculty of Medicine, Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.

Cellular Microbiology
|January 19, 2019
PubMed

Insights

Mycobacterium marinum phosphatases PtpA, PtpB, and SapM control the phosphoinositide (PI) landscape within the Mycobacterium-containing vacuole (MCV). Deleting these phosphatases impairs bacterial replication and alters vacuole maturation.

Area of Science:

  • Microbiology
  • Cell Biology
  • Host-Pathogen Interactions

Background:

  • Mycobacterium tuberculosis and Mycobacterium marinum create specialized vacuoles (MCVs) for replication within host cells.
  • The phosphoinositide (PI) lipid composition of the MCV is critical for its formation and is modulated by mycobacterial PI phosphatases.

Purpose of the Study:

  • To investigate the roles of M. marinum PI phosphatases (PtpA, PtpB, SapM) in MCV biogenesis and intracellular survival.
  • To establish a method for generating defined M. marinum deletion mutants for functional analysis.

Main Methods:

  • Construction of M. marinum deletion mutants lacking PtpA, PtpB, and/or SapM using phage transduction.
  • Assessment of intracellular replication in macrophages and amoebae (Dictyostelium discoideum).
  • Fluorescence microscopy to analyze MCV phosphoinositide content and V-ATPase recruitment.

Main Results:

  • Deletion mutants showed impaired intracellular replication.
  • MCVs lacking PtpA, SapM, or all three phosphatases exhibited increased phosphatidylinositol-3-phosphate (PtdIns3P) accumulation.
  • PtpA inhibited MCV acidification by blocking V-ATPase recruitment.
  • All three phosphatases facilitated bacterial escape from the vacuole to the cytoplasm.

Conclusions:

  • Secreted M. marinum phosphatases PtpA, PtpB, and SapM are key regulators of the MCV PI pattern.
  • These phosphatases influence MCV acidification and promote phagosomal escape, crucial for mycobacterial survival and pathogenesis.
Keywords:
AcanthamoebaDictyosteliumMycobacteriumamoebabacterial pathogenesismacrophagepathogen vacuolephagosomephosphoinositide lipidtuberculosis

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