The Type III Secretion System Effector SptP of Salmonella enterica Serovar Typhi.

Content Provider	Europe PMC
Author	Johnson, Rebecca Byrne, Alexander Berger, Cedric N. Klemm, Elizabeth Crepin, Valerie F. Dougan, Gordon Frankel, Gad
Editor	Silhavy, Thomas J.
Copyright Year	2017
Abstract	ABSTRACTStrains of the various Salmonella enterica serovars cause gastroenteritis or typhoid fever in humans, with virulence depending on the action of two type III secretion systems (Salmonella pathogenicity island 1 [SPI-1] and SPI-2). SptP is a Salmonella SPI-1 effector, involved in mediating recovery of the host cytoskeleton postinfection. SptP requires a chaperone, SicP, for stability and secretion. SptP has 94% identity between S. enterica serovar Typhimurium and S. Typhi; direct comparison of the protein sequences revealed that S. Typhi SptP has numerous amino acid changes within its chaperone-binding domain. Subsequent comparison of ΔsptP S. Typhi and S. Typhimurium strains demonstrated that, unlike SptP in S. Typhimurium, SptP in S. Typhi was not involved in invasion or cytoskeletal recovery postinfection. Investigation of whether the observed amino acid changes within SptP of S. Typhi affected its function revealed that S. Typhi SptP was unable to complement S. Typhimurium ΔsptP due to an absence of secretion. We further demonstrated that while S. Typhimurium SptP is stable intracellularly within S. Typhi, S. Typhi SptP is unstable, although stability could be recovered following replacement of the chaperone-binding domain with that of S. Typhimurium. Direct assessment of the strength of the interaction between SptP and SicP of both serovars via bacterial two-hybrid analysis demonstrated that S. Typhi SptP has a significantly weaker interaction with SicP than the equivalent proteins in S. Typhimurium. Taken together, our results suggest that changes within the chaperone-binding domain of SptP in S. Typhi hinder binding to its chaperone, resulting in instability, preventing translocation, and therefore restricting the intracellular activity of this effector.IMPORTANCE Studies investigating Salmonella pathogenesis typically rely on Salmonella Typhimurium, even though Salmonella Typhi causes the more severe disease in humans. As such, an understanding of S. Typhi pathogenesis is lacking. Differences within the type III secretion system effector SptP between typhoidal and nontyphoidal serovars led us to characterize this effector within S. Typhi. Our results suggest that SptP is not translocated from typhoidal serovars, even though the loss of sptP results in virulence defects in S. Typhimurium. Although SptP is just one effector, our results exemplify that the behavior of these serovars is significantly different and genes identified to be important for S. Typhimurium virulence may not translate to S. Typhi.
Related Links	https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC5287405&blobtype=pdf
Page Count	18
ISSN	00219193
Journal	Journal of Bacteriology [J Bacteriol]
Volume Number	199
PubMed Central reference number	PMC5287405
Issue Number	4
PubMed reference number	27920299
e-ISSN	10985530
DOI	10.1128/jb.00647-16
Language	English
Publisher	American Society for Microbiology
Publisher Date	2017-01-30
Publisher Place	N.W., Washington, DC
Access Restriction	Open
Rights License	This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license. Copyright © 2017 Johnson et al.
Subject Keyword	Salmonella enterica serovar Typhi SptP type III secretion system
Content Type	Text
Resource Type	Article
Subject	Molecular Biology Microbiology