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.
