Exploring the Molecular Architecture of FADD:Caspase-8 Signalling Platforms and how this determines cell life/death decisions

Applications are invited for a 4 year PhD studentship to be held within the MacFarlane lab at the MRC Toxicology Unit, University of Cambridge.

Project Outline:

Following exposure to drugs or environmental agents, several large multi-protein signalling platforms play a key role in determining cell death or survival. Caspase-8, a key regulator of cell fate, is recruited/activated within these complexes; for example, the Death-Inducing Signalling Complex (DISC), Necrosome and Ripoptosome. Despite these signalling platforms playing a role in determining the tissue response to toxic insult (e.g. drug-induced liver injury), the mechanisms underlying their assembly and regulation is still poorly understood.

Recruitment of Procaspase-8 to the adaptor molecule FADD is mediated via Death Effector Domain (DED) interactions. Subsequently, multiple Procaspase-8 molecules are required to interact via their tandem DEDs to form a helical Caspase-8-activating chain. c-FLIP isoforms, which are key regulators of procaspase-8 activation, are recruited to the complex via a co-operative/hierarchical binding mechanism involving Procaspase-8 (Hughes et al. 2016 Mol. Cell; Horn et al. 2017 Cell Rep). The ratio of c-FLIPL/S to Procaspase-8 is a critical regulator of Caspase-8 dimerization/catalytic activation within tDED oligomers and crucially defines how c-FLIP isoforms differentially control cell fate, predicting that c-FLIPS blocks Caspase-8 activation by somehow disrupting tDED triple helix assembly. Using negative-stain Electron Microscopy (EM) and Cryo-EM, we have recently visualized the 3D structural architecture of the core FADD:Caspase-8 complex (Fox et al. 2021 Nat Commun). However, the mechanisms whereby other tDED proteins such as cFLIP L/S or Caspase-10 interact with/regulate this core FADD:Caspase-8 complex remains to be determined. 

This project will explore the molecular assembly and regulation of FADD:Caspase-8 signalling platforms by other key tDED regulators (e.g. c-FLIP and Caspase-10). By co-expression of recombinant full-length proteins to form key protein-protein interactions, together with negative-stain transmission electron microscopy (TEM), new information on the molecular architecture of FADD:Caspase-8 containing complexes will be obtained. Moreover, we will employ the FEI TALOS Cryo-EM within the MRC Toxicology Unit to solve the structure of these complexes and validate key interactions using structure-guided mutagenesis linked to signalling output. Overall, this project will provide novel insights into the co-ordinated control of life/death decisions by FADD:Caspase-8 signalling platforms including the DISC, Necrosome and Ripoptosome thereby increasing our understanding the cellular response to toxic injury. 

The Medical Research Council (MRC) Toxicology Unit is a leading International Research Institute within the School of Biological Sciences, University of Cambridge. The Unit delivers mechanistic toxicology research, pursuing hypothesis-driven toxicological questions with a particular focus on the study of the causal links between exposure to endogenous and exogenous toxicants, molecular initiating events and adverse outcome pathways. The Unit's overall aims are to carry out pioneering research which leads to improved health and to train and mentor the next generation of toxicologists.

The Unit provides a supportive learning environment designed to meet the scientific and transferable skills required for an internationally competitive career. Our PhD Programme aims to train the scientific leaders of the future, giving them rewarding research projects with access to world-class facilities and expertise. Students receive toxicology-specific training in the Unit and through the ITTP | MRC Toxicology Unit (cam.ac.uk)

Application Process

Applicants should have or shortly expect to obtain a first or good upper second-class degree from a UK university, or an equivalent standard from an overseas university, in a relevant subject with a strong interest in cell death regulation, protein biochemistry and the application of multi-disciplinary approaches to uncover novel biology.  In addition creativity, curiosity, enthusiasm, and the ability to work in a team are essential.

You are strongly recommended to contact the project supervisor prior to submitting your formal application to find out more about the project and eligibility: Marion MacFarlane [Email Address Removed]

Information regarding the application process can be found at: PhD Programme | MRC Toxicology Unit (cam.ac.uk)

All formal applications will need to be made through the University Application Portal:

PhD in Biological Science (MRC Toxicology Unit) | Postgraduate Admissions (cam.ac.uk)

Your online application must include:

• A CV, including full details of all University course grades to date -

• Contact details for two academic or professional referees

• A personal statement of interest

Closing date: Friday 31^st March 2023 or until a suitable candidate is found. Early applications are recommended.