Metabolic plasticity and virulence of Cryptococcus neoformans are regulated by mitochondrial homeostasis

Abstract

The mitochondrion is a versatile organelle involved in diverse processes, such as cell death, metal homeostasis, plasma membrane and cell wall integrity, stress response, oxygen concentration, temperature, and metabolic adaptation, in addition to its role in generating energy. Consequently, mitochondrial fitness is essential for the pathogenicity of various organisms, including fungi. Cryptococcus neoformans is a fungal pathogen responsible for over 180,000 HIV-related deaths each year. In this study, we analyzed C. neoformans metabolic plasticity when grown with non-fermentable carbon sources and their impact on virulence and mitochondrial homeostasis. Growth on non-fermentable carbon sources increased thermotolerance, glucuronoxylomannan (GMX) content in the capsule, melanization rate, urease activity, biofilm formation, and virulence. Moreover, cells grown on non-fermentable carbon sources manifested increased mitochondrial number and activity. Conversely, mutants of the master regulator of mitochondrial biogenesis, the Hap complex, the catalytic subunit 1 of protein kinase A, or media supplementation with antioxidants, decreased the use of alternative carbon sources, capsule formation, melanin synthesis, urease activity, mitochondrial number, and resistance to both fluconazole and macrophage killing. Our results implicate mitochondrial homeostasis in virulence regulation via the PKA pathway, suggesting that targeting fungal mitochondrial homeostasis could be a therapeutic approach for cryptococcosis.