Oxidative Stress Causes Vacuolar Fragmentation in the Human Fungal Pathogen <i>Cryptococcus neoformans</i>

• Main Authors: Donghyeun Kim, Moonyong Song, Eunsoo Do, Yoojeong Choi, James W. Kronstad, Won Hee Jung
• Format: Article
• Language: English
• Published: MDPI AG 2021-06-01
• Series: Journal of Fungi
• Subjects: <i>Cryptococcus neoformans</i>; fragmentation; oxidative stress; superoxide dismutase; vacuole
• Online Access: https://www.mdpi.com/2309-608X/7/7/523

Vacuoles are dynamic cellular organelles, and their morphology is altered by various stimuli or stresses. Vacuoles play an important role in the physiology and virulence of many fungal pathogens. For example, a <i>Cryptococcus neoformans</i> mutant deficient in vacuolar functions showed significantly reduced expression of virulence factors such as capsule and melanin synthesis and was avirulent in a mouse model of cryptococcosis. In the current study, we found significantly increased vacuolar fragmentation in the <i>C. neoformans</i> mutants lacking <i>SOD1</i> or <i>SOD2</i>, which respectively encode Zn, Cu-superoxide dismutase and Mn-superoxide dismutase. The <i>sod2</i> mutant showed a greater level of vacuole fragmentation than the <i>sod1</i> mutant. We also observed that the vacuoles were highly fragmented when wild-type cells were grown in a medium containing high concentrations of iron, copper, or zinc. Moreover, elevated temperature and treatment with the antifungal drug fluconazole caused increased vacuolar fragmentation. These conditions also commonly cause an increase in the levels of intracellular reactive oxygen species in the fungus, suggesting that vacuoles are fragmented in response to oxidative stress. Furthermore, we observed that Sod2 is not only localized in mitochondria but also in the cytoplasm within phagocytosed <i>C. neoformans</i> cells, possibly due to copper or iron limitation.