Protein kinase C pathway activation by a newly-discovered fungal toxin

This 4-year PhD studentship is offered in Prof Peter Parker’s Group based at the Francis Crick Institute (the Crick) and Dr Julian Naglik’s Group based at King’s College London.

Candidalysin is a newly-discovered cytolytic peptide toxin secreted by Candida albicans [1], the causative agent of thrush which causes millions of mucosal infections annually. Candidalysin is the first toxin identified in any human fungal pathogen, which represents a landmark discovery in Microbiology and a seminal advance in our understanding of fungal pathogenesis. Candidalysin possesses multiple functions. At low doses, Candidalysin activates cell signalling mechanisms and innate immune responses [2, 3]. At high doses, Candidalysin intercalates and forms pores in epithelial membranes, inducing calcium influx, reactive oxygen species, cell damage and ultimately cell death [1-3, and unpublished]. Our data shows that Candidalysin is the key virulence factor required for C. albicans mucosal pathogenicity in vivo [1].
The key epithelial signalling pathways activated by Candidalysin are the MAPK pathway, leading to activation of the c-Fos transcription factor [2], and the PI3K pathway, leading to AKT/PDK/mTor activation [3]. Candidalysin can also bind phosphaditylserine, induces the release of EGFR (epidermal growth factor receptor) ligands, and activates EGFR signalling, all of which are targets of protein kinase C (PKC) signalling. We now have evidence that Candidalysin also activates the PKC pathway in epithelial cells. The PKC family comprises up to 12 distinct serine/threonine protein kinases that are implicated in a multitude of physiological functions, including proliferation, cell death and modulation of ion channels [4]. Given that many of these cell functions are induced by Candidalysin, this project will build on these breakthrough discoveries to determine the role of the PKC pathway in mediating epithelial activation by Candidalysin.
First, we will determine which PKC family members are activated by Candidalysin using a combination of PKC phosphorylation arrays, targeted proteomics and imaging [5]. Activation of upstream components that feed into the PKC pathway will also be assessed, including the PKC-cofactor phosphaditylserine, phospholipase C (PLC), diacylglycerol (DAG), PI3K and calcium signalling. Once the key PKC family members are identified, we will determine their functional role in mediating downstream cell activation events, including EGFR ligand release, MAPK activation, MARCKs phosphorylation, cytokine induction and cell stress/death. Concomitantly, the role of upstream components on PKC activation will also be assessed, including phosphaditylserine, PLC and PI3K signalling, calcium influx and DAG generation. These functional studies will be undertaken using a combination of RNA interference, monoclonal blocking antibodies (ligand release), drug inhibition, dominant negatives/mutant expression and reporter imaging. Finally, the role of the PKC pathway in protective responses to Candidalysin and C. albicans during mucosal infections will be determined using murine and zebrafish models, for which specific (conditional) knockout strains in the PKC pathway are available.
This project will combine the expertise of two internationally leading laboratories; the Naglik laboratory, which discovered Candidalysin, and the Parker laboratory, a world-leading group in PKC signalling. Together with additional preliminary data (below), this robust Crick-KCL collaboration has high potential for success and provides a unique opportunity to significantly advance our understanding of Candidalysin function and to characterise, for the first time, the role of the PKC pathway in the epithelial response to this fungal pathogen.

Talented and motivated students passionate about doing research are invited to apply for this PhD position. The successful applicant will join the Crick PhD Programme in September 2017 and will register for their PhD at King’s College London.

Applicants should hold or expect to gain a first/upper second-class honours degree or equivalent in a relevant subject and have appropriate research experience as part of, or outside of, a university degree course and/or a Masters degree in a relevant subject.

APPLICATIONS MUST BE MADE ONLINE VIA OUR WEBSITE BY 12NOON GMT NOVEMBER 14TH 2016. APPLICATIONS WILL NOT BE ACCEPTED IN ANY OTHER FORMAT.
https://www.crick.ac.uk/about-us/jobs-and-study/phd-programme/