Posttranscriptional Regulation of the Yersinia pestis Cyclic AMP Receptor Protein Crp and Impact on Virulence

Abstract

The cyclic AMP receptor protein (Crp) is a transcriptional regulator that controls the expression of numerous bacterial genes, usually in response to environmental conditions and particularly by sensing the availability of carbon. In the plague pathogen Yersinia pestis, Crp regulates the expression of multiple virulence factors, including components of the type III secretion system and the plasminogen activator protease Pla. The regulation of Crp itself, however, is distinctly different from that found in the well-studied Escherichia coli system. Here, we show that at physiological temperatures, the synthesis of Crp in Y. pestis is positively regulated at the posttranscriptional level. The loss of the small RNA chaperone Hfq results in decreased Crp protein levels but not in steady-state Crp transcript levels, and this regulatory effect occurs within the 5′ untranslated region (UTR) of the Crp mRNA. The posttranscriptional activation of Crp synthesis is required for the expression of pla, and decoupling crp from Hfq through the use of an exogenously controlled promoter and 5′ UTR increases Pla protein levels as well as partially rescues the growth defect associated with the loss of Hfq. Finally, we show that both Hfq and the posttranscriptional regulation of Crp contribute to the virulence of Y. pestis during pneumonic plague. The Hfq-dependent, posttranscriptional regulation of Crp may be specific to Yersinia species, and thus our data help explain the dramatic growth and virulence defects associated with the loss of Hfq in Y. pestis.

The Pla Protease of Yersinia pestis Degrades Fas Ligand to Manipulate Host Cell Death and Inflammation

“…Indeed, Pla is required for the full virulence of Y. pestis during both bubonic and pneumonic plague (Lathem et al, 2007; Sodeinde et al, 1992). Pla activates host fibrinolysis during bubonic plague to enable dissemination from the skin to distal sites (Degen et al, 2007), and during pneumonic plague, Pla is required for the massive outgrowth of bacteria observed in the lower airways and is maximally expressed during the pro-inflammatory phase of disease (Lathem et al, 2007; Lathem et al, 2014). The mechanisms by which Pla contributes to bubonic vs. pneumonic plague may be distinct, however, and the host proteins cleaved by Pla in the lungs to alter inflammation and enhance disease during pneumonic plague are not yet known.…”

Genome-Wide Analysis of Small RNAs Expressed by Yersinia pestis Identifies a Regulator of the Yop-Ysc Type III Secretion System

“…Previously, we demonstrated that Hfq is required for the production of multiple T3SS effector proteins by Y. pseudotuberculosis (20 (1,18,19,32). Therefore, to eliminate the effects of Pla on the T3SS, we deleted the CDS of pla from the pgm-negative strain of Y. pestis.…”

“…For instance, Hfq and sRNAs participate in the regulation of biofilms produced by uropathogenic E. coli, V. cholerae, and Y. pestis, as well as in the regulation of alpha-toxin synthesis in Staphylococcus aureus (23,(25)(26)(27)(28)(29). Indeed, Hfq and sRNAs have been shown to contribute to the virulence of a number of pathogens, including both Y. pestis and Y. pseudotuberculosis (20,(30)(31)(32).…”

Inactivation of Peroxiredoxin 6 by the Pla Protease of Yersinia pestis

“…While it is possible that the host response to a high dose of the ⌬pla mutant delivered to the lungs may differ from that of wild-type Y. pestis given at lower doses, our results are consistent with a Pla-dependent cleavage of Prdx6 in vivo at 48 h, while pla is maximally expressed. Indeed, the snapshot of the infection at 48 h allows us to make the best examination and comparison of Pla-dependent processes within the lungs, as this is when pla is upregulated by Y. pestis during pneumonic plague and when the proinflammatory response is fully induced in response to the infection (35,55). While there is a Pla-dependent decrease in extracellular Prdx6 protein levels in the lungs after 48 h, we were unable to detect Prdx6 cleavage products in vivo, as is observed following cleavage of Prdx6 by Pla in vitro.…”