Expression and secretion of Salmonella pathogenicity island-2 virulence genes in response to acidification exhibit differential requirements of a functional type III secretion apparatus and SsaL

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Title Expression and secretion of Salmonella pathogenicity island-2 virulence genes in response to acidification exhibit differential requirements of a functional type III secretion apparatus and SsaL
Author Coombes, Brian K.; Brown, Nathaniel Francis; Vandez, Yanet; Brumell, John H.; Finlay, B. Brett
Journal Name Journal of Biological Chemistry
Year Published 2004
Place of publication USA
Publisher American Society for Biochemistry and Molecular Biology
Abstract Salmonella pathogenicity island (SPI)-2 is pivotal to the intracellular survival of Salmonella and for virulence in mammals. SPI-2 encodes virulence factors (called effectors) that are translocated into the host cell, a type III secretion apparatus and a two-component regulatory system that regulates intracellular expression of SPI-2. Salmonella SPI-2 secretion activity appears to be induced in response to acidification of the vacuole in which it replicates. Here we show that the expression of the SPI-2 proteins, SseB and SseD (filament and pore forming components of the secretion apparatus, respectively) in response to acidification requires an intact secretion system and SsaL, a Salmonella homologue of SepL, a regulator required for type III-dependent secretion of translocators but not effectors in attaching and effacing gastrointestinal pathogens. We show that the expression of SPI-2-encoded effectors is acid-regulated but can be uncoupled from the expression of filament and translocon components, thus showing a differential requirement of SsaL for expression. The secretion and translocation of SPI-2-encoded effectors requires SsaL, but SsaL is dispensable for the secretion of SPI-2 effectors encoded in other pathogenicity loci, suggesting a secretion regulation function for SsaL. Further, we demonstrate that the differential expression of adjacent genes within the sseA operon (sseD and sseE) occurs at the transcriptional level. These data indicate that a Salmonella SPI-2 activation state is achieved by an acidregulated response that requires SsaL. These data also suggest the existence of a previously unrecognized regulatory element within SPI-2 for the “effector operon” region downstream of sseD that might demarcate the expression of translocators and effectors.
Peer Reviewed Yes
Published Yes
Publisher URI http://www.jbc.org/
Alternative URI http://dx.doi.org/10.1074/jbc.M404299200
Volume 279
Issue Number 48
Page from 49804
Page to 49815
ISSN 0021-9258
Date Accessioned 2007-06-27
Language en_AU
Faculty Institute for Glycomics
Subject Infectious Agents; Protein Targeting and Signal Transduction
URI http://hdl.handle.net/10072/15338
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1x

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