Amino Acid Permeases and Virulence in Cryptococcus neoformans

Abstract

Fungal opportunistic pathogens colonize various environments, from plants and wood to human and animal tissue. Regarding human pathogens, one great challenge during contrasting niche occupation is the adaptation to different conditions, such as temperature, osmolarity, salinity, pressure, oxidative stress and nutritional availability, which may constitute sources of stress that need to be tolerated and overcome. As an opportunistic pathogen, C. neoformans faces exactly these situations during the transition from the environment to the human host, encountering nutritional constraints. Our previous and current research on amino acid biosynthetic pathways indicates that amino acid permeases are regulated by the presence of the amino acids, nitrogen and temperature. Saccharomyces cerevisiae and Candida albicans have twenty-four and twenty-seven genes encoding amino acid permeases, respectively; conversely, they are scarce in number in Basidiomycetes (C. neoformans, Coprinopsis cinerea and Ustilago maydis), where nine to ten permease genes can be found depending on the species. In this study, we have demonstrated that two amino acid permeases are essential for virulence in C. neoformans. Our data showed that C. neoformans uses two global and redundant amino acid permeases, Aap4 and Aap5 to respond correctly to thermal and oxidative stress. Double deletion of these permeases causes growth arrest in C. neoformans at 37°C and in the presence of hydrogen peroxide. The inability to uptake amino acid at a higher temperature and under oxidative stress also led to virulence attenuation in vivo. Our data showed that thermosensitivity caused by the lack of permeases Aap4 and Aap5 can be remedied by alkaline conditions (higher pH) and salinity. Permeases Aap4 and Aap5 are also required during fluconazole stress and they are the target of the plant secondary metabolite eugenol, a potent antifungal inhibitor that targets amino acid permeases. In summary, our work unravels (i) interesting physiological property of C. neoformans regarding its amino acid uptake system; (ii) an important aspect of virulence, which is the need for amino acid permeases during thermal and oxidative stress resistance and, hence, host invasion and colonization; and (iii) provides a convenient prototype for antifungal development, which are the amino acid permeases Aap4/Aap5 and their inhibitor.

Role of Amino Acid Metabolism in the Virulence of Human Pathogenic Fungi

“…CaGap1-6 -CnAap1-8 oap4△/oap5△, oap1△/aap2△ and oap8△ strains are attenuated in G. melonella model, aap4△/aap5△ in murine inhalation model [34,35] AfGap1 -CaTor1 has not been studied in detail, it is assumed that it likewise influences the expression of NCR-associated genes and amino acid permeases (AAPs) [43], while Aftor was shown to be involved in amino acid metabolism [44]. The nitrogen or amino acid metabolism-related functions of CnTor1 have not been defined.…”

ATGGenes Influence the Virulence of Cryptococcus neoformans through Contributions beyond Core Autophagy Functions

“…Amino acids and the acquisition of nitrogen are important for virulence in C. neoformans (21,(37)(38)(39)(40), and amino acids differed in their support of growth as sole nitrogen sources. We found that the WT strain and the atgΔ mutants of C. neoformans were able to grow equally well when transferred from a rich medium (YPD) to media with preferred amino acids, presumably because the cells were induced for uptake and use of the amino acids.…”

Cryptococcus neoformanssecretes small molecules that inhibit IL-1β inflammasome-dependent secretion

“…Notably, amino acid permeases are important for the protection of the yeast when challenged by environmental or host promoted stress conditions. C. neoformans mutants with defect in these enzymes are less virulence, highlighting the importance of amino acid uptake during infection [85]. Yeast cells deficient in a small protein allegedly involved in the citric acid cycle had a higher expression of amino acids (i.e.…”