Submitted to: Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/11/2011
Publication Date: 3/1/2012
Citation: Eshghi, A., Pinne, M., Haake, D.A., Zuerner, R.L., Frank, A.T., Cameron, C.E. 2012. Methylation and in vivo expression of the surface-exposed Leptospira interrogans outer-membrane protein OmpL32. Microbiology. 158(Pt. 3):622-635. Interpretive Summary: Leptospirosis is a significant disease that affects livestock production and has a direct impact on human and animal public health. Current vaccines provide limited protection, and therefore need to be improved. The current study describes discovery of a surface protein that undergoes extensive modifications that likely affects how host antibody interacts with these bacteria. This is the first report of this type of modification in Leptospira. This type of protein modification may help the pathogen evade the host immune system and therefore may be an important virulence mechanism. By identifying this type of modification system, it may be easier to design better vaccines that take into account the potential for extensive protein modification.
Technical Abstract: Recent studies have revealed that bacterial protein methylation is a widespread post-translational modification that is required for virulence in selected pathogenic bacteria. In particular, altered methylation of outer membrane proteins has been shown to modulate the effectiveness of the host immune response. In this study, two-dimensional gel electrophoresis combined with matrix-assisted laser desorption/ionization-time of flight mass spectrometry identified a Leptospira interrogans serovar Copenhageni strain Fiocruz L1-130 protein, corresponding to open reading frame (ORF) LIC11848, which undergoes extensive and differential methylation of glutamic acid residues in response to altered environmental conditions. Immunofluorescence microscopy implicated LIC11848 as a surface-exposed outer membrane protein, prompting the designation OmpL32. Indirect immunofluorescence microscopy of liver and kidney sections revealed expression of OmpL32 during colonization of these organs. Identification of methylated surface-exposed outer membrane proteins, such as OmpL32, provides a foundation for delineating the role of this post-translational modification in leptospiral virulence.