Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2018

Dsb enzymes: promising anti-virulence drug targets for Gram-negative pathogens (#228)

Rabeb Dhouib 1 , Dimitrios Vagenas 1 , Jason Paxman 2 , Tony Wang 2 , Pooja Sharma 3 4 , Jennifer Martin 5 6 , Martin Scanlon 4 , Begoña Heras 2 , Makrina Totsika 1
  1. Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Brisbane, QLD, Australia
  2. Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, Australia
  3. Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA
  4. Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, VIC, Australia
  5. Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD, Australia
  6. Griffith Institute for Drug Discovery, Griffith University, Brisbane, Queensland, Australia

The resistance of various bacterial pathogens to different antibiotics constitutes a public health crisis worldwide. Due to the paucity in new antibiotic discovery and development, the need for new antimicrobials with new mechanisms of action is urgent. Developing compounds that block bacterial virulence (antivirulence) is a promising approach currently under intensive research. In Gram negative pathogens, the disulfide bond (Dsb) proteins are major facilitators of virulence; therefore, they play a key role in bacterial pathogenesis and constitute attractive targets for antivirulence drug development. Here we investigated whether our recently identified inhibitors of Escherichia coli K-12 DsbA can inhibit the diverse DsbA enzymes found in an important human pathogen, Salmonella enterica serovar Typhimurium, and attenuate its virulence. This pathogen encodes in addition to the prototypical E. coli K-12 DsbAB system an accessory DsbL/DsbI enzyme pair and a plasmid encoded DsbA homologue termed SrgA. Our DsbA inhibitors from two chemical classes (phenylthiophene and phenoxyphenyl derivatives) were able to block the virulence of dsbA null mutants complemented with structurally diverse DsbL and SrgA, suggesting that those compounds were not selective for prototypical DsbA. The ability of all compounds to inhibit DsbL was also confirmed as the activity of the native substrate of this enzyme (AssT) has decreased in the presence of the inhibitors. Modelling of DsbL- and SrgA-inhibitor interactions showed that these accessory enzymes could accommodate the inhibitors in their different hydrophobic grooves, supporting our in vivo findings. Further, we investigated growth of S. Typhimurium in the presence of DsbA inhibitors in a minimal medium. Our findings showed that some DsbA homologues are involved in growth under physiologically relevant conditions. This was confirmed by growth of isogenic S. Typhimurium dsb deletion mutants. Taken together, this work demonstrates that DsbA inhibitors can be developed to target diverse homologues found in pathogenic bacteria and this might have a fitness cost to the pathogen during infection.