Date of Award

1-1-2016

Embargo Period

1-1-2019

Document Type

Thesis - MUSC Only

Degree Name

Master of Science (MS)

Department

Microbiology and Immunology

College

College of Graduate Studies

First Advisor

Caroline Westwater

Second Advisor

Carl Atkinson

Third Advisor

David Schofield

Fourth Advisor

Adam Smolka

Abstract

Candida glabrata is a human opportunistic pathogen which causes superficial and life-threatening systemic infections. Over the last three decades, the number of candidiasis cases attributed to C. glabrata has risen at an alarming rate. This trend is of particular concern due to the propensity of C. glabrata to develop resistance to commonly used antifungal agents, and its innate resistance to many host-derived peptides with antimicrobial activity. Our laboratory has discovered that complement-derived peptide C3a exhibits antifungal activity against Candida species. The cellular target and antifungal mechanism of action of C3a is currently unknown. In the present study, we demonstrate that C3a induces a dramatic decrease in intracellular ATP in C. glabrata cells coupled with an increase in ATP release into the extracellular space. Intracellular ATP efflux following C3a treatment was shown to be concentration-dependent and time-dependent, with efflux observed as early as 10 min post-exposure to C3a. The rapid release of cellular ATP and subsequent cell death did not result in concurrent intracellular uptake of the DNA-binding dye propidium iodide or the release of the fluorescent dye calcein. However, C3a-induced ATP efflux and cell death were abrogated when cells were pre-incubated with the anion channel inhibitor, DIDS. Additionally, C3a treatment induced depolarization of the fungal plasma membrane at 20 min post-exposure to C3a, suggesting a role for ATP loss in the destabilization of the electrochemical gradient and proton motive force. It is likely that the mechanism of C3a fungal toxicity does not rely on calcium-dependent stress signaling, which is evident in the lack of changes in intracellular calcium levels following C3a treatment. Taken together, our findings indicate that C3a induces non-cytolytic efflux of intracellular ATP in C. glabrata, resulting in depolarization of the plasma membrane; and that a key feature of this mechanism is the opening of a functional anion channel.

Rights

All rights reserved. Copyright is held by the author.

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