YaxAB, a Yersinia enterocolitica Pore-Forming Toxin Regulated by RovA

Abstract

The transcriptional regulator RovA positively regulates transcription of the Yersinia enterocolitica virulence gene inv. Invasin, encoded by inv, is important for establishment of Y. enterocolitica infection. However, a rovA mutant is more attenuated for virulence than an inv mutant, implying that RovA regulates additional virulence genes. When the Y. enterocolitica RovA regulon was defined by microarray analysis, YE1984 and YE1985 were among the genes identified as being upregulated by RovA. Since these genes are homologous to Xenorhabdus nematophila cytotoxin genes xaxA and xaxB, we named them yaxA and yaxB, respectively. In this work, we demonstrate the effects of YaxAB on the course of infection in the murine model. While a yaxAB mutant (⌬yaxAB) is capable of colonizing mice at the same level as the wild type, it slightly delays the course of infection and results in differing pathology in the spleen. Further, we found that yaxAB encode a probable cytotoxin capable of lysing mammalian cells, that both YaxA and YaxB are required for cytotoxic activity, and that the two proteins associate. YaxAB-mediated cell death occurs via osmotic lysis through the formation of distinct membrane pores. In silico tertiary structural analysis identified predicted structural homology between YaxA and proteins in pore-forming toxin complexes from Bacillus cereus (HBL-B) and Escherichia coli (HlyE). Thus, it appears that YaxAB function as virulence factors by inducing cell lysis through the formation of pores in the host cell membrane. This characterization of YaxAB supports the hypothesis that RovA regulates expression of multiple virulence factors in Y. enterocolitica.

Structure and mechanism of the two-component α-helical pore-forming toxin YaxAB

“…6a ). In line with previous studies 27 , 28 , which used bacterial lysates, YaxAB added sequentially to liposomes bound membranes (which is not the case once YaxAB is premixed).

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“…Expressed toward later stages of the bacteria’s life cycle within the insect host, XaxAB is thought to be required for the breakdown of the larval cadaver 31 . Recently, the possible involvement of a XaxAB orthologue during course of infection within a mammalian host was reported 28 . Moreover, a strain of the human pathogen Y. enterocolitica , in which the toxin orthologue YaxAB was knocked out, showed altered colonization behavior and tissue pathology in a murine infection model.…”

Thermal control of virulence factors in bacteria: A hot topic

“…49 The 5 0 -UTR of the lcrF mRNA harbours a RNA thermosensor similar to prfA. Furthermore, transcription of lcrF is also repressed by the nucleoid-associated protein YmoA, which is selectively degraded at 37 C. 48 Yersinia spp also possess RovA which represses the expression of several virulence factors, [50][51][52][53] and is required for colonisation and adaptation to host-associated stress. 54 A shift from external to host physiological temperatures (i.e.…”

A Combined YopB and LcrV Subunit Vaccine Elicits Protective Immunity against Yersinia Infection in Adult and Infant Mice

“…Blood samples were collected from age-matched pups on day 7 or 14 (prior to vaccination) and from vaccinated mice every week thereafter until day 28 and every 2 wk until day 63 after birth. Twentyeight days after the last immunization, mice were challenged via oral gavage with 100 ml containing 9.7-10.3 3 10 7 CFU (15-16-wk-old adult mice) and 10.9-12.0 3 10 7 CFU (8-9-wk-old young mice) of Y. enterocolitica strain Ye8081 (provided by Dr. V. Miller, University of North Carolina School of Medicine); organisms were grown as previously described (32). The challenge dose corresponded to ∼10 times the dose at which 50% death was achieved (LD 50 ) for both age groups.…”