Farnesol-induced apoptosis in Candida albicans is mediated by Cdr1-p extrusion and depletion of intracellular glutathione.
Farnesol is a key derivative in the sterol biosynthesis pathway in eukaryotic cells previously identified as a quorum sensing molecule in the human fungal pathogen Candida albicans. Recently, we demonstrated that above threshold concentrations, farnesol is capable of triggering apoptosis in C. albicans. However, the exact mechanism of farnesol cytotoxicity is not fully elucidated. Lipophilic compounds such as farnesol are known to conjugate with glutathione, an antioxidant crucial for cellular detoxification against damaging compounds. Glutathione conjugates act as substrates for ATP-dependent ABC transporters and are extruded from the cell. To that end, this current study was undertaken to validate the hypothesis that farnesol conjugation with intracellular glutathione coupled with Cdr1p-mediated extrusion of glutathione conjugates, results in total glutathione depletion, oxidative stress and ultimately fungal cell death. The combined findings demonstrated a significant decrease in intracellular glutathione levels concomitant with up-regulation of CDR1 and decreased cell viability. However, addition of exogenous reduced glutathione maintained intracellular glutathione levels and enhanced viability. In contrast, farnesol toxicity was decreased in a mutant lacking CDR1, whereas it was increased in a CDR1-overexpressing strain. Further, gene expression studies demonstrated significant up-regulation of the SOD genes, primary enzymes responsible for defense against oxidative stress, with no changes in expression in CDR1. This is the first study describing the involvement of Cdr1p-mediated glutathione efflux as a mechanism preceding the farnesol-induced apoptotic process in C. albicans. Understanding of the mechanisms underlying farnesol-cytotoxicity in C. albicans may lead to the development of this redox-cycling agent as an alternative antifungal agent.
Department of Oncology and Diagnostic Sciences, University of Maryland, Baltimore, Maryland, United States of America.
Jingsong
J
Zhu
Bastiaan P
BP
Krom
Dominique
D
Sanglard
Chaidan
C
Intapa
Clinton C
CC
Dawson
Brian M
BM
Peters
Mark E
ME
Shirtliff
Mary Ann
MA
Jabra-Rizk
D000935:Antifungal Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D002176:Candida albicans / Q000166:cytology* / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005204:Farnesol / Q000494:pharmacology*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D005978:Glutathione / Q000378:metabolism*; D019803:Glutathione Disulfide / Q000378:metabolism; D006706:Homeostasis / Q000187:drug effects; D042541:Intracellular Space / Q000187:drug effects* / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D015203:Reproducibility of Results; D013482:Superoxide Dismutase / Q000235:genetics
D000935:Antifungal Agents; C094693:CDR1 protein, Candida albicans; D005656:Fungal Proteins; D026901:Membrane Transport Proteins; D017382:Reactive Oxygen Species; D005204:Farnesol; D013482:Superoxide Dismutase; D020169:Caspases; D005978:Glutathione; D019803:Glutathione Disulfide