The Monoterpene Carvacrol Generates Endoplasmic Reticulum Stress in the Pathogenic Fungus Candida albicans

• Published in: Antimicrobial agents and chemotherapy Vol. 59; no. 8; pp. 4584 - 4592
• Main Authors: Chaillot, Julien, Tebbji, Faiza, Remmal, Adnane, Boone, Charlie, Brown, Grant W., Bellaoui, Mohammed, Sellam, Adnane
• Format: Journal Article
• Language: English
• Published: United States American Society for Microbiology 01.08.2015
• Subjects: Basic-Leucine Zipper Transcription Factors - genetics; Candida albicans; Candida albicans - drug effects; Candida albicans - genetics; Endoplasmic Reticulum; Endoplasmic Reticulum - drug effects; Endoplasmic Reticulum - genetics; Endoplasmic Reticulum Stress; Endoplasmic Reticulum Stress - drug effects; Endoplasmic Reticulum Stress - genetics; Endoribonucleases - genetics; Gene Expression Regulation, Fungal - drug effects; Gene Expression Regulation, Fungal - genetics; Mechanisms of Action: Physiological Effects; Monoterpenes; Monoterpenes - pharmacology; Origanum; Protein-Serine-Threonine Kinases - genetics; RNA, Messenger - genetics; Saccharomyces cerevisiae; Saccharomyces cerevisiae - drug effects; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae Proteins - genetics; Signal Transduction - drug effects; Signal Transduction - genetics; Thymus; Transcription, Genetic - drug effects; Transcription, Genetic - genetics; Unfolded Protein Response - drug effects; Unfolded Protein Response - genetics
• ISSN: 0066-4804; 1098-6596; 1098-6596
• DOI: 10.1128/AAC.00551-15

The monoterpene carvacrol, the major component of oregano and thyme oils, is known to exert potent antifungal activity against the pathogenic yeast Candida albicans . This monoterpene has been the subject of a considerable number of investigations that uncovered extensive pharmacological properties, including antifungal and antibacterial effects. However, its mechanism of action remains elusive. Here, we used integrative chemogenomic approaches, including genome-scale chemical-genetic and transcriptional profiling, to uncover the mechanism of action of carvacrol associated with its antifungal property. Our results clearly demonstrated that fungal cells require the unfolded protein response (UPR) signaling pathway to resist carvacrol. The mutants most sensitive to carvacrol in our genome-wide competitive fitness assay in the yeast Saccharomyces cerevisiae expressed mutations of the transcription factor Hac1 and the endonuclease Ire1, which is required for Hac1 activation by removing a nonconventional intron from the 3′ region of HAC1 mRNA. Confocal fluorescence live-cell imaging revealed that carvacrol affects the morphology and the integrity of the endoplasmic reticulum (ER). Transcriptional profiling of pathogenic yeast C. albicans cells treated with carvacrol demonstrated a bona fide UPR transcriptional signature. Ire1 activity detected by the splicing of HAC1 mRNA in C. albicans was activated by carvacrol. Furthermore, carvacrol was found to potentiate antifungal activity of the echinocandin antifungal caspofungin and UPR inducers dithiothreitol and tunicamycin against C. albicans . This comprehensive chemogenomic investigation demonstrated that carvacrol exerts its antifungal activity by altering ER integrity, leading to ER stress and the activation of the UPR to restore protein-folding homeostasis.