Cdc14 phosphatase - novel roles in drug resistance, virulence, and the response to cell wall stress in fungal pathogens - PROJECT SUMMARY Opportunistic fungal infection of immune-compromised individuals is an escalating world health problem. Recent lethal outbreaks of multi drug-resistant Candida auris in hospitals and the rise of drug resistance in normally benign commensal fungi like C. glabrata highlight the severity of the problem. Current treatment options for fungal infections are limited to a few antifungal drug classes that are becoming increasingly ineffective. There is a pressing need for new molecular targets for antifungal development to deal with drug- resistant pathogens. This project will characterize a newly identified C. albicans virulence and drug resistance factor, the Cdc14 protein phosphatase. Our recent work has uncovered novel roles for C. albicans Cdc14 in regulating cell wall integrity, septation, echinocandin sensitivity, and hyphal development, all processes tied to virulence. Importantly, even modest reduction in Cdc14 activity level severely compromises virulence in a mouse model of invasive candidiasis. In contrast, Cdc14 is dispensable for normal development, growth, and cell division in animals. Cdc14 is highly conserved in fungi and its unique and strict active site specificity implies that development of potent and highly selective inhibitors should be achievable, something that has been challenging with other protein phosphatases. Our overall objective is to characterize the mechanisms by which Cdc14 regulates virulence-associated biological processes in C. albicans. In Aim 1 we will characterize Cdc14 regulation of cell wall integrity and septation. In Aim 2 we will characterize Cdc14 regulation of hyphal initiation and maintenance. In Aim 3 we will characterize the mechanisms by which Cdc14 itself is regulated by cell wall stress and hypha-inducing signals. In Aims 1 and 2 we will employ unbiased omics approaches to identify the relevant substrates of Cdc14 and the transcriptional circuits under Cdc14 control. In Aim 1 we will directly characterize the cell wall defects arising from Cdc14-deficiency. We will also test specific models for Cdc14 function in promoting cell wall integrity and hyphal initiation in Aims 1 and 2, respectively. In Aim 3 we will focus on phosphoregulation of the disordered Cdc14 C-terminal tail, which is a hub for integration of regulatory signals in model fungi. We will use quantitative phosphoproteomics to understand the dynamic phosphorylation of C. albicans Cdc14 during cell wall stress, cytokinesis/septation, and initiation of hyphal differentiation. All three aims will conclude with structure-function analyses using biochemical, cell biological, and waxworm and mouse infection assays to characterize the physiological significance of Cdc14 function and phosphoregulation, including the importance for pathogenesis. Collectively, the results will define the molecular mechanisms by which Cdc14 promotes several virulence-related biological processes that will be useful in assessing its future potential as an antifungal target. The identification of Cdc14 substrates and effectors may provide additional candidate antifungal targets. The high conservation of Cdc14 structure, activity, and specificity across the fungal kingdom implies the results will be relevant to many other fungal pathogens.
