Fixed-term

Details This project will investigate the role of ZDHHC5, a cell surface-localised protein S-acyltransferase, in regulating cell adhesion and bacterial adherence to human cells. ZDHHC5 is one of 23 human DHHC enzymes responsible for attaching fatty acids to proteins, a process known as S-acylation (or palmitoylation). This modification is reversible and dynamically regulates protein trafficking, stability, and function. We hypothesise that ZDHHC5-mediated S-acylation of key adhesion proteins is a crucial regulatory mechanism for bacterial adherence to human cells. The project aims to identify and quantify the specific protein substrates of ZDHHC5 that are involved in cell-cell adhesion, as cell adhesion pathways are often commandeered for bacterial adherence to host cells. The project will also determine if these protein substrates are utilised in cell-bacterial adhesion and investigate how ZDHHC5-mediated S-acylation affects bacterial binding to human cells. This project will utilise a combination of molecular and cell biology approaches, microbiology and advanced quantitative proteomic methods. ZDHHC5 knockout cells will be used to study the perturbed cell surface proteome and how this leads to a bacterial adherence phenotype. Direct S-acylation substrates of ZHHC5 will be identified using a mass spectrometry-based proteomics method that we have developed. Specific proteins identified from this screen will be validated using siRNA-mediated knockdown and CRISPR knockout in bacterial adherence assays to determine which specific cell surface proteins mediate interactions with bacteria. Understanding the mechanism by which ZDHHC5 regulates interactions between cells and how it controls bacterial adherence and traversal will help to develop new strategies to combat infectious diseases, especially in the face of growing antibiotic resistance. It would enable the creation of novel therapeutic and preventative measures that target the initial, critical step of infection. Funding Notes Self-Funded students only, you will need to have your own funding. First class or upper second 2(i) in a relevant subject. To formally apply for a PhD, you must complete the University’s application form using the following link: https://www.sheffield.ac.uk/postgraduate/phd/apply/applying All applicants should ensure that both references are uploaded onto their application as a decision will be unable to be made without this information. References Wolverson PA, Fernandes Parreira I, Thompson RH, Collins MO, Shaw JG, Green LR. Dynamics of the CD9 interactome during bacterial infection of epithelial cells by proximity labelling proteomics. FEBS J. 2025 Oct 17. doi: 10.1111/febs.70291. Woodley KT, Collins MO. S-acylated Golga7b stabilises DHHC5 at the plasma membrane to regulate cell adhesion. EMBO Rep. 2019 Oct 4;20(10):e47472. doi: 10.15252/embr.201847472 https://sheffield.ac.uk/biosciences/people/academic-staff/mark-collins Apply Now

Details Antimicrobial-resistant typhoid fever The world faces epidemics of antimicrobial-resistant (AMR) typhoid fever caused by Salmonella Typhi that underlies 12 million cases / 129 000 deaths each year. Understanding how infection develops and how human host cells combat Salmonella will improve control strategies that are vital to typhoid elimination efforts. Typhoid toxin a tumour suppressor mechanism called senescence. A major virulence factor implicated in typhoid is the typhoid toxin of Salmonella Typhi. We discovered that the toxin induces DNA damage responses in human cells that accelerates an ageing-like process called senescence (Ibler et 2019, Nature Communications). Senescence is an innate defence against cancer marked by cell-cycle arrest but we recently showed that p53-dependent senescence attacks Salmonella and suppresses the activities of typhoid toxin via the senescence-associated secretory phenotype (SASP) (Srour et al 2025, EMBO Mol Med; ElGhazaly et al 2023, Cell Reports). The findings indicate that DNA damage responses have co-evolved to not only protect mammalian cells from cancer but infections by bacterial pathogens. However, we do not understand how these host defences or how they are regulated. Thus, we seek an enthusiastic PhD researcher to study the mechanisms by which DNA damage responses activate innate defences against major pathogens such as Salmonella Typhi and related toxigenic Salmonella. Objectives Determine metabolic and proteomic senescence responses to DNA damage induced by typhoid toxin Identify and resolve the senescence-associated antimicrobial mechanisms restricting Salmonella infection The project combines molecular cell biology, infection, mass spectrometry (metabolic, proteomics) and immunological approaches. By challenging cultured human cells with Salmonella Typhi in a containment level 3 laboratory, the project will replicate infection mechanisms underlying typhoid. Typhoid toxin activation of senescence and its manipulation by intracellular Salmonella will be studied using fluorescent microscopes. Mass spectrometry will be exploited to identify DNA damage-associated antimicrobial pathways and provide a springboard for resolving how the host senses and combats Salmonella during infection. The mechanisms aim to be validated and further investigated using clinical samples from patients with typhoid fever. Contact Dr. Daniel Humphreys (d.humphreys@sheffield.ac.uk) for more information and assistance with your application. Funding Notes Self-Funded Students only – You must have your own funding. References Supervisor references Srour et al. 2025, EMBO Mol Med (https://doi.org/10.1038/s44321-025-00347-8) ElGhazaly et al., 2023, Cell Reports (https://doi.org/10.1016/j.celrep.2023.113181) Ibler et al. 2023, Nat Commun (https://doi.org/10.1038/s41467-019-12064-1) Apply Now

Details Clostridial neurotoxins are produced by anaerobic bacteria such as Clostridium botulinum. Each toxin molecule has a highly conserved zinc-dependent protease domain that cleaves SNARE proteins, a family of molecules required for intracellular trafficking and vesicle fusion. Due to their potency, specificity and length of action they have become widely used in the cosmetic industry and have also proven very effective in the treatment of medical disorders associated with neuronal hyperactivity. In 2017 a new botulinum toxin was discovered and named BoNT/X. BoNT/X cleaves a larger number of SNARE proteins than conventional botulinum toxins, opening up the possibility of targeting new biological processes and medical conditions. The aim of this project is to characterise the biology of BoNT/X and determine how it intoxicates cells so gaining an insight into its therapeutic potential. The student will be trained in a range of state of the art techniques including recombinant protein engineering, super resolution microscopy and intracellular transport assays. In addition, the student will also gain experience in generic approaches such as molecular biology, cell culture and viral transductions. Funding Notes Self-Funded Students only References https://sites.google.com/sheffield.ac.uk/peden-lab https://etheses.whiterose.ac.uk/28686/ Apply Now

Details Background Typhoid toxin is a DNase-like virulence factor of the human pathogen Salmonella Javiana, which intoxicates cells throughout the microenvironment. We discovered that the toxin induces DNA damage responses in cultured cells that activates a senescence tumour suppressor mechanism (https://doi.org/10.1038/s41467-019-12064-1). Cells undergoing toxin-induced senescence undergo permanent cell-cycle arrest and release a secretome (https://doi.org/10.1016/j.celrep.2023.113181), which causes paracrine senescence and attracts immune cells to eliminate senescent cells. Despite these advances, toxin-induced senescence by Salmonella has not been investigated in an animal infection model. Senescence is a major defence against cancer, which causes 10 million deaths annually. Bacterial cancer therapy (BCT) shows promise for treatment of solid tumours, of which, attenuated Salmonella Typhimurium is the best studied. Salmonella is extremely tumour tropic, selectively colonising tumour-tissue over healthy tissue, and activates innate immune responses. However, Salmonella Typhimurium does not encode typhoid toxin and, thus, we hypothesise that treating cancerous tissue with attenuated Salmonella Javiana instead would enhance BCT through the typhoid toxin that would cause senescence and further inhibit tumour development. Objectives Thus, we seek an enthusiastic PhD student to: (i) Study toxin-induced senescence in a human cell and mouse infection models, and (ii) investigate whether toxin-induced senescence can be exploited to improve BCT. Novelty and Timeliness The project will advance understanding of Salmonella-induced senescence by revealing the mechanism in vivo and how this can be exploited to improve health. This aligns with MRC Research Priorities in securing better health, ageing, wellbeing, and combatting infections. Chemotherapy and radiotherapy are life savers following cancer diagnosis but they damage healthy tissues – novel treatment strategies are required. The project is timely given the phase-1 trials using Salmonella to treat bladder cancer and the rise in cancer diagnoses. For example, the colon is the natural host tissue of Salmonella, and colon cancer is the fourth most common cause of cancer death in the UK with over 40,000 new cases diagnosed in 2024. Experimental approach Biochemical and molecular approaches will purify typhoid toxin and engineer attenuated Salmonella Javiana, which will induce senescence in mouse cancer cells in vitro prior to injection into a mouse before assessing effects on metastasis. AOM/DSS model of Colitis-Associated Cancer will be used to determine whether Salmonella infection reduces the number of tumours in a toxin-dependent manner. The effect of senescence on metastasis and tumour development will be quantified and imaged using IVIS Imaging, and senescence analysed using microbiology, immunoblotting, RNA sequencing and fluorescence microscopy. Funding Notes Self-funded applicants desired References Supervisor references Srour et al. 2025, EMBO Mol Med (https://doi.org/10.1038/s44321-025-00347-8) ElGhazaly et al., 2023, Cell Reports (https://doi.org/10.1016/j.celrep.2023.113181) Ibler et al. 2023, Nat Commun (https://doi.org/10.1038/s41467-019-12064-1) Relevant review on BCT Badie et al 2021, Frontiers in Oncology, (10.3389/fonc.2021.624759) Apply Now