The Role of Melanin-Transporting Extracellular Vesicles in Cryptococcus neoformans Oxidative Stress Tolerance

• Grant number: 25/08681-4
• Support Opportunities: Scholarships abroad - Research Internship - Scientific Initiation
• Start date: July 01, 2025
• End date: October 31, 2025
• Field of knowledge: Biological Sciences - Microbiology - Biology and Physiology of Microorganisms
• Principal Investigator: Fausto Bruno dos Reis Almeida
• Grantee: Henrique Trevisam de Oliveira
• Supervisor: Liliane Mukaremera
• Host Institution: Faculdade de Medicina de Ribeirão Preto (FMRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil
• Institution abroad: University of Exeter, Exeter, England
• Associated to the scholarship: 24/15805-9 - Role of extracellular vesicles from Cryptococcus neoformans in the cellular communication, BP.IC

Abstract

Cell-to-cell communication is essential for pathogenic fungi to adapt to environmental stressors such as pH changes, temperature shifts, radiation, and inhibitors. Cryptococcus neoformans, the pathogen responsible for cryptococcosis -a serious and potentially fatal disease- uses extracellular vesicles (EVs) for cellular signaling. These EVs, identified in fungi like Candida, Aspergillus, Paracoccidioides, and Cryptococcus, transport bioactive molecules including proteins, enzymes, and nucleic acids. In Cryptococcus, EVs carry important virulence factors such as urease, laccase, superoxide dismutase (SOD), and melanin. Melanin serves multiple protective roles: shielding cells from radiation, enhancing antifungal resistance, supporting cell wall integrity, and acting as an antioxidant. Melanin synthesis can be induced in vitro using L-DOPA, which is oxidized into melanin by laccase, an enzyme encoded by the LAC1 gene. SOD enzymes, encoded by SOD genes, are key mitochondrial components that detoxify reactive oxygen (ROS) and nitrogen species (RNS), contributing to the fungal pathogenicity. This study aims to assess how melanization affects oxidative stress tolerance in melanized C. neoformans H99 and in SOD-deficient mutant strains (sod1¿ and sod2¿). Additionally, EVs will be isolated from melanized wild-type (Mel+) strains and introduced into non-melanized (Mel¿) mutant strains. After that, mitochondrial membrane potential of these fungal strains will be evaluated using JC-1 staining in flow cytometry and fluorescence microscopy. By comparing responses across melanized, non-melanized, wild-type, and mutant strains -before and after EV exposure- we seek to uncover how EVs influence oxidative stress tolerance and mitochondrial function. This research will contribute valuable insights into fungal stress adaptation and the role of EV-mediated communication in pathogenesis. (AU)