Two Isoforms of Yersinia pestis Plasminogen Activator Pla: Intraspecies Distribution, Intrinsic Disorder Propensity, and Contribution to Virulence

Abstract

It has been shown previously that several endemic Y. pestis isolates with limited virulence contained the I259 isoform of the outer membrane protease Pla, while the epidemic highly virulent strains possessed only the T259 Pla isoform. Our sequence analysis of the pla gene from 118 Y. pestis subsp. microtus strains revealed that the I259 isoform was present exclusively in the endemic strains providing a convictive evidence of more ancestral origin of this isoform. Analysis of the effects of the I259T polymorphism on the intrinsic disorder propensity of Pla revealed that the I259T mutation slightly increases the intrinsic disorder propensity of the C-terminal tail of Pla and makes this protein slightly more prone for disorder-based protein-protein interactions, suggesting that the T259 Pla could be functionally more active than the I259 Pla. This assumption was proven experimentally by assessing the coagulase and fibrinolytic activities of the two Pla isoforms in human plasma, as well as in a direct fluorometric assay with the Pla peptide substrate. The virulence testing of Pla-negative or expressing the I259 and T259 Pla isoforms Y. pestis subsp. microtus and subsp. pestis strains did not reveal any significant difference in LD50 values and dose-dependent survival assays between them by using a subcutaneous route of challenge of mice and guinea pigs or intradermal challenge of mice. However, a significant decrease in time-to-death was observed in animals infected with the epidemic T259 Pla-producing strains as compared to the parent Pla-negative variants. Survival curves of the endemic I259 Pla+ strains fit between them, but significant difference in mean time to death post infection between the Pla−strains and their I259 Pla+ variants could be seen only in the isogenic set of subsp. pestis strains. These findings suggest an essential role for the outer membrane protease Pla evolution in Y. pestis bubonic infection exacerbation that is necessary for intensification of epidemic process from endemic natural focality with sporadic cases in men to rapidly expanding epizootics followed by human epidemic outbreaks, local epidemics or even pandemics.

Humoral and cellular immune responses to Yersinia pestis Pla antigen in humans immunized with live plague vaccine

“…Nevertheless, only Pla can convert plasminogen to plasmin by limited proteolysis, and this activity was likely crucial for the increased lethality of Y . pestis that developed during the course of evolution [ 7 – 9 ].…”

Phylogenetically Defined Isoforms of Listeria monocytogenes Invasion Factor InlB Differently Activate Intracellular Signaling Pathways and Interact with the Receptor gC1q-R

“…The molecular model was suggested that H-R substitution might have functional implications that result in better fitness for the R variant, thus contributing to the successful spread and high virulence of the USA300 strain [58]. The epidemic highly virulent Yersinia pestis strains possessed only the Pla T259 isoform of the plasminogen activator Pla while Pla I259 isoform is spread among Y. pestis isolates with limited virulence [60,61]. Computational and experimental analysis demonstrated that the Pla isoform found in Y .…”

“…Computational and experimental analysis demonstrated that the Pla isoform found in Y . pestis epidemic strains is more functionally efficient than that of the low virulent strains [61,62],…”

New Promising Targets for Synthetic Omptin-Based Peptide Vaccine against Gram-Negative Pathogens

“…Here, we explored omptins representing a family of outer membrane proteases that have been identified in all major enterobacterial species pathogenic to humans [24] for the presence of similar immuno-reactive epitopes. The model pro-omptin antigen, Y. pestis Pla, was chosen for the following reasons: (i) the antigen is a surface-located outer-membrane integral protease with high similarity in 3D structure to other omptin family members [24]; (ii) Pla can convert plasminogen to plasmin by limited proteolysis, and this activity was likely crucial for the increased lethality of Y. pestis during the course of evolution [37,38,39]; (iii) Pla pro-omptin is involved in the dissemination of Y. pestis into circulation and is known as one of the major virulence determinants of this pathogen [40,41,42]; (iv) this protein has both species-specific and genus-specific epitopes that were detected using a panel of monoclonal antibodies [43]; (v) Pla pro-omptin activation occurs at 37 °C, coinciding with the formation of truncated less-toxic tetra-acylated LPS, which is produced instead of highly toxic hexa-acylated LPS made by Y. pestis at 26 °C [44]. Importantly, the Pla pro-omptin is apparently involved in pathogen–host interaction following the induction of host immune response: a detectable level of the relevant antibodies to this antigen was found in the convalescent sera of human survivors of plague infection [45], in mice that survived experimental plague [46], and in the sera of animals and humans vaccinated with live plague vaccine (LPV, EV line NIIEG) [11,28,29,30].…”