Defense Date

6-12-2023

Graduation Date

Summer 8-5-2023

Availability

One-year Embargo

Submission Type

dissertation

Degree Name

PhD

Department

Biological Sciences

Committee Chair

Jana Patton-Vogt

Committee Member

Joseph McCormick

Committee Member

Wook Kim

Committee Member

Aaron Mitchell

Keywords

lipid

Abstract

The metabolism of phosphatidylcholine (PC), a major eukaryotic membrane lipid, has been shown to be an important aspect of pathogenesis in Candida albicans. Of note, PC turnover product, glycerophosphocholine (GPC), is abundant renal metabolite available within the host. GPC is readily imported by C. albicans, and deletion of the major GPC transporter, Git3, leads to decreased virulence in a bloodstream infection model. Here I have characterized two potential metabolic fates of internalized GPC. The first metabolic fate explored is internalized GPC can be hydrolyzed to release Pi. To determine if GPC import and subsequent metabolism impact phosphate homeostasis upon Pi limitation, I monitored growth and phenotypic outputs in cells provided with either Pi or GPC as phosphate sources. A knockout strain of the high affinity Pi transporter, Pho84, exhibit phenotypes associated with Pi limitation, GPC provision rescues sensitivity to osmotic and cell wall stresses, but not to oxidative stress. Further, I show that GPC provision, like Pi provision, results in repression of the PHO regulon and activation of TORC1 signaling. Pi uptake is similar to GPC uptake when phosphate availability is low (200 µM) demonstrating that GPC can be utilized while Pi is available like in the human host. The second metabolic fate explored is GPC acylation. In Saccharomyces cerevisiae and some plant species, GPC is directly acylated by Gpc1 to form Lyso-PC via the PC deacylation/reacylation pathway (PC-DRP). Here I report that GPC can also be directly acylated in C. albicans by the protein product of orf19.988, a homolog of ScGpc1. Through lipidomic studies, I show that loss of Gpc1 leads to a decrease in overall PC levels. A gpc1∆/∆ strain exhibits a variety of increased sensitivities to antifungals that target lipid metabolism. Further, loss of Gpc1 results in a hyphal growth defect under embedded conditions, and a decrease in long term viability.

Language

English

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