Characterisation of Hsp90 and its interaction networks in the fungal pathogen of humans, Candida glabrata

Abstract

Fungal infections kill over 1.6 million people worldwide annually and are an underappreciated burden on health services. The most common life-threatening fungal infection in the UK is invasive candidiasis. 75% of invasive candidiasis is caused by two species, Candida albicans and Candida glabrata. Mortality rates of candidiasis are unacceptably high and treatments remain limited due to a paucity of drug targets and growing antifungal drug resistance.
Drug resistance is regulated by the chaperone, heat shock protein 90 (Hsp90) in C. glabrata and C. albicans. In C. albicans, several other virulence traits are also modulated by Hsp90, but little was known about Hsp90’s role in C. glabrata virulence. Therefore, C. glabrata Hsp90’s (CgHsp90) influence on key virulence traits was phenotypically explored, and CgHsp90’s proteomic and genetic interaction networks investigated.
A Hsp90 genetic network was produced by a synthetic-lethality screen on a C. glabrata gene-deletion library covering 16% of the genome. This network spans 68 genes across three temperatures. In a complementary study, quantitative proteomics of Hsp90-inhibited cells yielded a network of 2298 proteins that interact with CgHsp90. In both networks, most genes presented at only one temperature, emphasising the environmental contingency of Hsp90 interactomes. A meta-analysis of Hsp90 networks between C. glabrata and its relatives, C. albicans and S. cerevisiae, identified a conserved core interactome. However, regulation of conserved interactors appears to be species-specific. Further differences in Hsp90’s functions between species were highlighted by Hsp90’s influence on specific virulence traits. Inhibition or repression of CgHsp90 revealed that the chaperone governs resistance to amphotericin B but not cell adhesion, gel invasion or colony morphology. These data suggest rewiring of Hsp90 networks across evolutionary time and offer important insights for further research.
Presented here is the first combined multi-‘omic interaction network, and characterisation of Hsp90’s role in key virulence traits in the important pathogen of humans, C. glabrata.

Date of Award	28 Sept 2021
Original language	English
Awarding Institution	University of Bristol
Supervisor	Stephanie Diezmann (Supervisor), Christiane H Berger-Schaffitzel (Supervisor), Andrew Preston (Supervisor) & Ken Haynes (Supervisor)