Abstract 2257 Exploring transcription factor regulation by Cdc14 phosphatase in response to cell wall stress in the opportunistic pathogen Candida albicans

Human fungal pathogens result in over 6 million cases of invasive infections and more than 3 million deaths each year.Despite this, research to better understand these pathogens and develop new antifungal drugs lags behind that of other infectious disease classes.Candida albicans is designated a critical priority pathogen by the World Health Organization, as it accounts for the majority of all fungal infections and is associated with a high mortality rate for bloodstream infections.We recently identified a novel cell wall integrity (CWI) role for the protein phosphatase Cdc14 in Candida albicans.When CDC14 is deleted, C. albicans is more susceptible to treatment with echinocandin antifungal drugs that inhibit cell wall synthesis, and virulence is also greatly reduced.However, the role that Cdc14 plays in the CWI pathway, including its substrates, are not well understood.In cells lacking Cdc14, the CWI MAP kinase pathway is still activated normally in response to cell wall stress, but expression of downstream CWI target genes, such as ECM331 and PGA31, fails to induce.This implies that Cdc14 functions downstream of the MAP kinase activation step in the CWI signaling pathway, but upstream of target gene transcription.We hypothesize that Cdc14 is activated by cell wall stress to dephosphorylate the transcription factors (TFs) responsible for the CWI response, leading to their nuclear import.In the model fungus S. cerevisiae, Cdc14 de-phosphorylates several TFs during the cell cycle to activate their nuclear import, including Swi6, which also plays a role in the CWI response.Using a bioinformatic search algorithm I identified a small set of TFs with candidate Cdc14-regulated nuclear localization signals, and I predict one or more will localize to the nucleus in response to cell wall stress in a Cdc14-dependent manner.To test this, I designed strains expressing each candidate substrate tagged with GFP from its natural promoter, as well as phosphosite mutants predicted to bypass the requirement for Cdc14 de-phosphorylation.I am comparing localization of the wild-type and mutant proteins with and without 1) Cdc14 and 2) echinocandin drug treatment.I expect this work will provide mechanistic insight into how Cdc14 controls the response to cell wall stress in Candida albicans.