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Clade-1 Vap virulence proteins of Rhodococcus equi are associated with the cell surface and support intracellular

Zeynep Yerlikaya1,2, Raúl Miranda-CasoLuengo1, Yuting Yin1

  • 1UCD School of Biomolecular and Biomedical Science and UCD Conway Institute, University College Dublin, Dublin, Ireland.

Plos One
|January 6, 2025
PubMed

Insights

Certain Rhodococcus equi virulence proteins, specifically VapK1, VapK2, and VapN, enable intracellular growth in macrophages. These clade-1 proteins, including VapA, are located on the bacterial cell surface, with their N-termini crucial for this localization.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Molecular Biology

Background:

  • Rhodococcus equi is an intracellular pathogen that infects macrophages, evading phagolysosome maturation to survive and replicate.
  • Virulent R. equi strains possess host-specific virulence plasmids encoding a family of 17 Vap proteins across seven clades.
  • The function and localization of these Vap proteins are critical for understanding R. equi pathogenesis.

Purpose of the Study:

  • To investigate the role of the 17 Vap proteins in supporting intracellular growth of R. equi within macrophages.
  • To determine the cellular localization of Vap proteins and identify key domains involved in surface association.
  • To elucidate the functional and structural diversity of Vap proteins in relation to their pathogenic mechanisms.

Main Methods:

  • Complementation assays using a R. equi ΔvapA mutant strain to assess intracellular growth.
  • Cell surface localization studies using techniques to detect protein presence on the bacterial exterior.
  • Sequence analysis of Vap protein N-termini to identify conserved regions and their correlation with localization.

Main Results:

  • Only VapK1, VapK2, and VapN proteins restored intracellular growth of the R. equi ΔvapA strain in murine macrophages.
  • VapA, VapK1, VapK2, and VapN were identified as clade-1 proteins located on the R. equi cell surface.
  • The N-terminal regions of Vap proteins, although variable, are conserved within clades and play a role in cell surface localization, particularly for clade-1 proteins.

Conclusions:

  • VapK1, VapK2, and VapN are key virulence factors contributing to intracellular survival of R. equi.
  • Cell surface localization of specific Vap proteins, mediated by their N-termini, is essential for R. equi pathogenesis.
  • Understanding Vap protein function and localization provides insights into host-pathogen interactions and potential therapeutic targets.

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