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MxiD, an outer membrane protein necessary for the secretion of the Shigella flexneri lpa invasins

A Allaoui1, P J Sansonetti, C Parsot

  • 1Unité de Pathogénie Microbienne Moléculaire, Unité INSERM 199, Institut Pasteur, Paris, France.

Molecular Microbiology
|January 1, 1993
PubMed

Insights

Shigella flexneri invasion relies on the MxiD protein, essential for secreting invasion proteins (Ipa). MxiD inactivation prevents bacterial entry into host cells and disease development.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Molecular Biology

Background:

  • The invasive phenotype of Shigella flexneri is mediated by the virulence plasmid pWR100.
  • pWR100 encodes invasion plasmid (Ipa) proteins and factors for their secretion and localization.

Purpose of the Study:

  • To characterize the mxiD gene and its role in Shigella flexneri virulence.
  • To investigate the function of MxiD in the secretion of invasion plasmid proteins.

Main Methods:

  • Gene inactivation of mxiD in Shigella flexneri.
  • Invasion assays using HeLa cells.
  • Keratoconjunctivitis assays in guinea-pigs.
  • Analysis of secreted and membrane proteins via culture supernatants and protein examination.
  • Amino acid sequence comparison of MxiD with homologous proteins.

Main Results:

  • mxiD inactivation abolished Shigella flexneri invasion of HeLa cells and keratoconjunctivitis in guinea-pigs.
  • Secretion of key invasion plasmid proteins (IpaA, IpaB, IpaC) was abolished in the mxiD mutant.
  • MxiD was identified as an outer membrane protein homologous to known protein secretion components (YscC, PulD).

Conclusions:

  • MxiD is an essential component of the invasion plasmid (Ipa) secretion apparatus in Shigella flexneri.
  • MxiD plays a critical role in bacterial invasion and pathogenesis.
  • MxiD represents a potential target for anti-virulence strategies against Shigella infections.

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