EASTBIO the role of the Ubiquitylation machinery in stress response in Candida albicans

Fungal pathogens kill over a million people every year. The most common human fungal pathogen is Candida albicans, a WHO-priority target. With only three classes of antifungal drugs available and increasing drug-resistant infections in clinical settings, understanding the mechanisms of resistance is a priority.

Candida's survival in the complex and dynamic host environment depends on the ability to efficiently control its metabolism, which involves the production and breakdown of numerous different small biological chemicals collectively called "metabolites". Candida is known to assimilate glucose and alternative carbon sources simultaneously, thereby providing growth advantages. However, how this

remarkable metabolic flexibility is regulated during infection, remains largely unknown. The Ubiquitin-Proteasome-System, UPS for short, is known to be responsible for eliminating unwanted, superfluous or toxic proteins that would otherwise damage Candida cells. Molecular machines, called E3 ubiquitin ligases, ensure that the UPS destroys only those proteins whose functions should be

terminated, and spares the majority of those required for ongoing cellular functions. One of the first UPS-dependent mechanisms identified in metabolic regulation is mediated by the budding yeast GID E3 ubiquitin ligase complex, which targets unnecessary metabolic enzymes for proteasomal degradation

upon changes in carbon sources. Evidence from the Makrantoni lab suggests that Candida employs the GID E3 complex during host infection to rewire metabolic pathways in order to enhance its virulence. This project aims to: (1) Uncover the molecular mechanism by which GID E3 ligase regulates metabolic flexibility in Candida.

a. Identify and characterize GID-dependent ubiquitylation substrate(s) that are targeted by the UPS using combined approaches of genetics, proteomics and biochemistry/crystallography. b. Investigate how GID and GID-dependent substrates regulate metabolite flux using metabolomics and live-cell imaging (microfluidics).

(2) Test how GID-mediated metabolic flexibility affects virulence and antifungal drug efficacy. Determine the role of GID in Candida's virulence and antifungal drug resistance using in vitro intestinalorganoid infection model systems under diverse metabolic conditions. Training outcomes: This interdisciplinary PhD project is supported by cross-institutional collaborations

between the Institute for Regeneration and Repair and the Institute of Cell Biology in Edinburgh, and the Institute of Medical Sciences in Aberdeen, providing state-of-the-art technologies. Skills that will be developed include sophisticated yeast genetics (CRISPR-Cas9 editing), structural analysis/biochemistry,

proteomics/metabolomics, microscopy, and 3D-cell culture systems. The student will be well supported by a supervisory team with complementary expertise and competencies, and a friendly and collaborative environment. The successful candidate is expected to train hands-on in all three labs. Most importantly, at the end of this project the student will have all of the necessary skills to

seamlessly transition between biological and clinical elements of biomedical science.