Proteolytic processing of the Yersinia pestis YapG autotransporter by the omptin protease Pla and the contribution of YapG to murine plague pathogenesis

Abstract

Autotransporter protein secretion represents one of the simplest forms of secretion across Gramnegative bacterial membranes. Once secreted, autotransporter proteins either remain tethered to the bacterial surface or are released following proteolytic cleavage. Autotransporters possess a diverse array of virulence-associated functions such as motility, cytotoxicity, adherence and autoaggregation. To better understand the role of autotransporters in disease, our research focused on the autotransporters of Yersinia pestis, the aetiological agent of plague. Y. pestis strain CO92 has nine functional conventional autotransporters, referred to as Yaps for Yersinia autotransporter proteins. Three Yaps have been directly implicated in virulence using established mouse models of plague infection (YapE, YapJ and YapK). Whilst previous studies from our laboratory have shown that most of the CO92 Yaps are cell associated, YapE and YapG are processed and released by the omptin protease Pla. In this study, we identified the Pla cleavage sites in YapG that result in many released forms of YapG in Y. pestis, but not in the evolutionarily related gastrointestinal pathogen, Yersinia pseudotuberculosis, which lacks Pla. Furthermore, we showed that YapG does not contribute to Y. pestis virulence in established mouse models of bubonic and pneumonic infection. As Y. pestis has a complex life cycle involving a wide range of mammalian hosts and a flea vector for transmission, it remains to be elucidated whether YapG has a measurable role in any other stage of plague disease.

Fibrinolytic and procoagulant activities of Yersinia pestis and Salmonella enterica

“…FasL initiates extrinsic apoptosis pathway by activating caspases, and the loss of FasL in lungs of infected animals resulted in reduced pulmonary apoptosis and aberrant pro-inflammatory cytokine levels that enabled optimal growth of Y. pestis in the lungs [34]. YapG and YapE are surface-bound autotransporters of the genus Yersinia with an array of putative virulence-associated functions, and they are proteolytically processed by Pla and thus released from bacterial surface [35,36]. Pla also cleaves and promotes translocation to eukaryotic cells of Yops (Yersinia outer membrane proteins) encoded on the 70-kb low-calcium-response plasmid present in Y. pestis, Y. pseudotuberculosis, and Y. eneterocolitica [37,38].…”

Inhibition of Outer Membrane Proteases of the Omptin Family by Aprotinin

“…In addition to host protein degradation, omptins are involved in the processing and secretion of the passenger domains of some bacterial autotransporters. Secretion of the S. flexneri IcsA and Y. pestis YapA, YapE, and YapG autotransporters depends on the proteolytic activity of omptins IcsP and Pla, respectively (4,5,36,37).…”

Adhesive Properties of YapV and Paralogous Autotransporter Proteins of Yersinia pestis

“…Based on the deciphered Y. pestis KIM genome (32), 10 different ORFs for predicted autotransporter proteins, designated YapA, YapC, YapE to YapH, and YapK to YapN, were originally described. Several of these proteins were investigated in more detail in the same strain (14) and in strain CO92 (16,17,24,26,37). An originally unrecognized ORF for a predicted autotransporter protein present in KIM5 but absent in strain CO92 was later designated yapV (y3429) (27).…”

“…More recent work indicates that the Bam proteins and possibly TAM (translocation assembly module) proteins participate in this process (21)(22)(23). Even though the translocated pas-senger domain of some autotransporter proteins is cleaved off (17,24), a defining characteristic of the type V protein secretion system (T5SS), a number of them remain surface associated by noncovalent bonds (25). Passenger domains typically endow the bacteria with new virulence properties by serving as adhesins, invasins, proteases, or toxins.…”