Comparative proteomic analysis of the PhoP regulon in Salmonella enterica Serovar Typhi versus Typhimurium

  • Richelle C. Charles
  • , Jason B. Harris
  • , Michael R. Chase
  • , Lauren M. Lebrun
  • , Alaullah Sheikh
  • , Regina C. LaRocque
  • , Tanya Logvinenko
  • , Sean M. Rollins
  • , Abdullah Tarique
  • , Elizabeth L. Hohmann
  • , Ian Rosenberg
  • , Bryan Krastins
  • , David A. Sarracino
  • , Firdausi Qadri
  • , Stephen B. Calderwood
  • , Edward T. Ryan

Research output: Contribution to journalArticlepeer-review

54 Scopus citations

Abstract

Background: S. Typhi, a human-restricted Salmonella enterica serovar, causes a systemic intracellular infection in humans (typhoid fever). In comparison, S. Typhimurium causes gastroenteritis in humans, but causes a systemic typhoidal illness in mice. The PhoP regulon is a well studied two component (PhoP/Q) coordinately regulated network of genes whose expression is required for intracellular survival of S. enterica. Methodology/Principal Findings: Using high performance liquid chromatography mass spectrometry (HPLC-MS/MS), we examined the protein expression profiles of three sequenced S. enterica strains: S. Typhimurium LT2, S. Typhi CT18, and S. Typhi Ty2 in PhoP-inducing and non-inducing conditions in vitro and compared these results to profiles of phoP-/Q- mutants derived from S. Typhimurium LT2 and S. Typhi Ty2. Our analysis identified 53 proteins in S. Typhimurium LT2 and 56 proteins in S. Typhi that were regulated in a PhoP-dependent manner. As expected, many proteins identified in S. Typhi demonstrated concordant differential expression with a homologous protein in S. Typhimurium. However, three proteins (HlyE, STY1499, and CdtB) had no homolog in S. Typhimurium. HlyE is a pore-forming toxin. STY1499 encodes a stably expressed protein of unknown function transcribed in the same operon as HlyE. CdtB is a cytolethal distending toxin associated with DNA damage, cell cycle arrest, and cellular distension. Gene expression studies confirmed up-regulation of mRNA of HlyE, STY1499, and CdtB in S. Typhi in PhoP-inducing conditions. Conclusions/Significance: This study is the first protein expression study of the PhoP virulence associated regulon using strains of Salmonella mutant in PhoP, has identified three Typhi-unique proteins (CdtB, HlyE and STY1499) that are not present in the genome of the wide host-range Typhimurium, and includes the first protein expression profiling of a live attenuated bacterial vaccine studied in humans (Ty800).

Original languageEnglish
Article numbere6994
JournalPloS one
Volume4
Issue number9
DOIs
StatePublished - Sep 10 2009

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