Bacterial-associated oncogenesis: Investigating the typhoid toxin of the persistent intracellular pathogen Salmonella Typhi in oncogenesis
- Dr Daniel Humphreys (Department of Biomedical Science)
- Dr Stephen Brown (Department of Biomedical Science)
The human intracellular bacterial pathogen Salmonella enterica serovar Typhi (S.Typhi) causes systemic typhoid fever resulting in 27 million cases of disease and 200,000 deaths each year. S.Typhi is a stealth pathogen and a hallmark feature is its ability to also establish persistent chronic infections in the gall bladder where the pathogen is associated with causing cancer.
Oncogenesis is exacerbated in humans carrying gene mutations that predispose individuals to gall bladder cancer. This is relevant to public health, as a link between infection and tumour development may result in personalised therapeutic protocols.
How S.Typhi persists in host cells and promotes oncogenesis is not known. S.Typhi initiates infections by injecting virulence proteins into mammalian host cells to direct uptake and replication within intracellular Salmonella-containing vacuoles (SCVs). From its intracellular niche, S.Typhi secretes the typhoid toxin into the extracellular milieu where it enters target host cells. Once inside the cell the toxin traffics to the nucleus where it reprogrammes cell cycle progression, causes DNA damage and manipulates cellular signalling through nuclease and ADP-ribosylase activities. Recent evidence shows that typhoid toxin mediates establishment of persistent infections in animal hosts, and persistence underlies S.Typhi-associated tumour development.
The mechanisms by which typhoid toxin manipulates cells to drive persistent infections are not understood, and the significance of the toxin to S.Typhi’s stealth virulence strategy and bacterial-associated oncogenesis has not been addressed. The PhD project will investigate these research questions using purified toxin derivatives and infection models in combination with the latest advances in molecular cell biology, fluorescence microscopy, and automated high-throughput screening technologies.
The student will join the laboratory of Dr. Daniel Humphreys (first supervisor) at the Department of Biomedical Science (BMS), University of Sheffield. The project will establish assays to study mammalian cells intoxicated with typhoid toxin using molecular, biochemical, genetic and fluorescence imaging approaches. In particular, how the toxin perturbs nuclear functions in cells predisposed to oncogenesis during S.Typhi infection will be examined using high resolution using structural resolution microscopy at the Wolfson Light Microscopy Suite at the BMS.
Having established the project foundations an RNAi screen will be developed with Dr. Steve Brown (third supervisor) at the RNAi Screening Facility, University of Sheffield.
The PhD student will be trained to use robotics and automated microscope systems to perform high-throughput RNAi screens aimed at identifying host genes required for cellular manipulation by the typhoid toxin.
Finally, the student will use Salmonella infection models, intoxication and cell transformation assays to investigate the significance of genes identified in the screen on pathogen persistence and the generation of bacterial-associated oncogenic phenotypes. These project components will be developed in the laboratories of the first supervisor and the second supervisor, Dr. Anjam Kahn, at the University of Newcastle.
To combat typhoid fever we need to understand the hijack mechanisms employed by S.Typhi to cause disease. By bringing together researchers from the University of Sheffield and the University of Newcastle, three areas of expertise will be combined to provide excellent scientific training and exposure to a broad range of techniques in a project of enormous biomedical significance.
- Humphreys D*. Singh V, Koronakis V*. (2016). Inhibition of WAVE Regulatory Complex activation by a bacterial virulence effector counteracts pathogen phagocytosis. Cell Reports. 17(3):697-707. PMID: 27732847.
- Humphreys D, Davidson AC, Hume PJ, Makin LE, Koronakis V. (2013) Arf6 coordinates actin assembly through the WAVE complex, a mechanism usurped by Salmonella to invade host cells. Proceedings of the National Academy of Sciences of the United States of America. 110(42):16880-16885. PMID: 24085844
- Humphreys D, Davidson AC, Hume PJ, Koronakis V. (2012) Salmonella SopE and host GEF ARNO cooperate to recruit and activate WAVE to trigger bacterial invasion. Cell Host & Microbe 11, 129-39. PMID: 22341462
- Smith, K., Humphreys, D., Hume, P.J., and Koronakis, V. (2010) Enteropathogenic Escherichia coli recruits the cellular inositol phosphatase SHIP2 to regulate actin-pedestal formation.
Cell Host & Microbe 7, 13-24. PMID: 20114025
Keywords: Biochemistry, Cancer / Oncology, Cell Biology / Development, Genetics, Microbiology, Molecular Biology, Pathology
For informal enquiries about this project, please contact:
- Dr Daniel Humphreys
- Email: D.Humphreys@sheffield.ac.uk
- Dr Stephen Brown
- Email: Stephen.Brown@sheffield.ac.uk
Application deadline: 2 December 2016
For more information about this project see the department's PhD Opportunities page: