Yersinia pestis is probably the best-characterized example of a pathogen

that exploits the host fibrinolytic system to penetrate host Akt inhibitor tissues. Yersinia expresses a surface serine protease (designated Pla) whose substrates include several complement components, PLG, and alpha2-antiplasmin (the primary circulating inhibitor of plasmin). Pla also has adhesin activity and binds to laminin (a glycoprotein of mammalian basement membranes). Because Pla upregulates plasmin activity, and because laminin is a substrate of plasmin, Yersinia can very efficiently penetrate basement membranes of host tissues [for review, see Suomalainen et. al. [44]]. Clearly, interaction with plasma components is a strategy that is used by many bacterial pathogens to gain a survival advantage within their hosts. The goal of the studies described here was to determine whether FT has the potential to use the host fibrinolytic system (specifically PLG) to enhance its ability to penetrate/disseminate following infection of a mammalian host. Our results indicate that both FTLVS and FTSchuS4 are able to acquire surface bound PLG in vitro and that this zymogen can be converted

selleck chemicals by a host-derived PLG activator into its active serine protease form (plasmin) while bound to FTLVS. The ability of PLG to bind its ligands typically involves its lysine-binding kringle domains. This specific interaction between PLG and exposed lysine residues can be inhibited with the lysine-analogue εACA and, to a lesser extent, with free lysine. Our check details findings revealed that binding of PLG to the surface Thymidylate synthase of FTLVS could be inhibited by εACA in a dose-dependent fashion. Moreover, we showed

that plasmin bound to the surface of FT could degrade fibronectin. This finding supports our hypothesis that the ability of FT to bind to serum plasmin may enhance its ability to penetrate extracellular matrices, enhancing its ability to disseminate in vivo. Using a ligand-blotting technique coupled with proteomic methodologies we identified five FTLVS proteins that were able to bind to PLG, each of which are highly conserved among the various FT type A and B strains. Three of these proteins are lipoproteins (gene products of FTL_0336, FTL_0421, and FTL_0645). Two of the lipoproteins are unique to FT, while the third, peptidoglycan-associated lipoprotein (PAL), is highly conserved among gram-negative bacteria. The specific use of surface-exposed lipoproteins as receptors for host PLG is not unusual and has been well documented in other human bacterial pathogens, such as some members of the genus Borrelia and Treponema. Several members of the genus Borrelia use complement regulator-acquiring surface proteins (CRASP) to bind both PLG and complement factor H to aid in the ability of the organism to both disseminate and to resist innate immunity [45–50].