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Measuring Phagosome pH by Ratiometric Fluorescence Microscopy
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Measuring Phagosome pH by Ratiometric Fluorescence Microscopy

Published on: December 7, 2015

V-ATPase-mediated phagosomal acidification is impaired by Streptococcus pyogenes through Mga-regulated surface

Pontus Nordenfelt1, Sergio Grinstein, Lars Björck

  • 1Division of Infection Medicine, Department of Clinical Sciences, BMC, B14, Lund University, SE-221 84 Lund, Sweden. pontus.nordenfelt@med.lu.se

Microbes and Infection
|September 18, 2012
PubMed

Insights

Streptococcus pyogenes inhibits phagosomal acidification by preventing vacuolar-type adenosine triphosphatase (V-ATPase) delivery. Mga regulon surface proteins are responsible for this mechanism, allowing bacterial survival within human neutrophils.

Area of Science:

  • Microbiology
  • Immunology
  • Cell Biology

Background:

  • Streptococcus pyogenes is a human pathogen that survives phagocytosis by neutrophils.
  • The mechanism of S. pyogenes survival, particularly its interaction with phagosomal trafficking, remains unclear.
  • Mutants lacking Mga-regulated virulence factors are phagocytosed and killed, suggesting Mga's role in survival.

Purpose of the Study:

  • To investigate if differences in phagosomal acidification contribute to S. pyogenes survival.
  • To determine the role of Mga-regulated factors in S. pyogenes's interaction with phagosomal pH.
  • To elucidate the mechanism by which S. pyogenes evades neutrophil killing.

Main Methods:

  • Utilized fluorescence ratio imaging to measure phagosomal pH in neutrophil-differentiated HL-60 cells.
  • Employed folimycin, a V-ATPase inhibitor, to assess proton delivery to phagosomes.
  • Analyzed isolated bacteria-containing phagosomes to confirm V-ATPase localization and function.

Main Results:

  • Wild-type S. pyogenes were found in non-acidified phagosomes, while Mga mutants were in acidic phagosomes.
  • Folimycin inhibited proton delivery to Mga mutant phagosomes but not wild-type phagosomes.
  • S. pyogenes actively removes or inactivates V-ATPases, with Mga-regulated proteins mediating this effect.

Conclusions:

  • S. pyogenes impairs phagosomal acidification by preventing V-ATPase-mediated proton delivery.
  • Mga-regulated surface proteins are crucial for inhibiting V-ATPase function and phagosomal acidification.
  • This mechanism contributes to S. pyogenes survival within human neutrophils.

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