Neisseria gonorrhoeae PIII has a role on NG1873 outer membrane localization and is involved in bacterial adhesion to human cervical and urethral epithelial cells

Abstract

BackgroundProtein PIII is one of the major outer membrane proteins of Neisseria gonorrhoeae, 95% identical to RmpM (reduction modifiable protein M) or class 4 protein of Neisseria meningitidis. RmpM is known to be a membrane protein associated by non-covalent bonds to the peptidoglycan layer and interacting with PorA/PorB porin complexes resulting in the stabilization of the bacterial membrane. The C-terminal domain of PIII (and RmpM) is highly homologous to members of the OmpA family, known to have a role in adhesion/invasion in many bacterial species. The contribution of PIII in the membrane architecture and its role in the interaction with epithelial cells has never been investigated.ResultsWe generated a ΔpIII knock-out mutant strain and evaluated the effects of the loss of PIII expression on bacterial morphology and on outer membrane composition. Deletion of the pIII gene does not cause any alteration in bacterial morphology or sensitivity to detergents. Moreover, the expression profile of the main membrane proteins remains the same for the wild-type and knock-out strains, with the exception of the NG1873 which is not exported to the outer membrane and accumulates in the inner membrane in the ΔpIII knock-out mutant strain.We also show that purified PIII protein is able to bind human cervical and urethral cells and that the ΔpIII knock-out mutant strain has a lower ability to adhere to human cervical and urethral cells.ConclusionHere we demonstrated that the PIII protein does not play a key structural role in the membrane organization of gonococcus and does not induce major effects on the expression of the main outer membrane proteins. However, in the PIII knock-out strain, the NG1873 protein is not localized in the outer membrane as it is in the wild-type strain suggesting a possible interaction of PIII with NG1873. The evidence that PIII binds to human epithelial cells derived from the female and male genital tract highlights a possible role of PIII in the virulence of gonococcus and suggests that the structural homology to OmpA is conserved also at functional level.

The Pathogenic Neisseria Use a Streamlined Set of Peptidoglycan Degradation Proteins for Peptidoglycan Remodeling, Recycling, and Toxic Fragment Release

“…It has been shown to crystalize with outer membrane porin PorB from GC (Zeth et al, 2013). It was also shown to be necessary for localizing the LysM-domain containing protein NGO1873 to the outer membrane, and binds to epithelial cells of the male and female genital tracts (Leuzzi et al, 2013). These proteins could function in alternative pathways to compensate for those absent in Neisseria (e.g., Tol-Pal, Lpp) or they may have other unknown influences on cell wall synthesis, PG remodeling, protein localization, or host attachment.…”

An immunoproteomics study of antisera from patients with gonorrhea identifies novel Neisseria gonorrhoeae proteins

“…MtrC (NGO1365, Supplementary Table 14, number 18) is a periplasmic membrane fusion lipoprotein, part of the gonococcal efflux pump that contributes to the survival of gonococci exposed to human neutrophils and their antimicrobial components (Handing et al, 2018). In our study, NGO1873 (Supplementary Table 14, number 22), the peptidoglycan-binding protein LysM, was predicted to be in the periplasm, but Leuzzi et al (2013) speculated that NGO1873 is able to reach the OM when the Rmp protein acts as a bridge between the OM and peptidoglycan layer. There was also the protein NGO2104 (Supplementary Table 14, number 24), identified as Fic (filamentation induced by cyclic AMP) toxin, whose cellular location was unknown.…”

Markerless gene editing in Neisseria gonorrhoeae

“…RmpM is a periplasmic protein that binds to the peptidoglycan layer and stabilizes membrane oligomeric complexes [22]. An rmpM knock-out strain has been successfully generated previously and did not have adverse effects on bacterial morphology [34]. rmpM is constitutively expressed in N.…”