Investigation of Cryptococcus neoformans magnesium transporters reveals important role of vacuolar magnesium transporter in regulating fungal virulence factors.

Cryptococcus neoformans is an important opportunistic fungal pathogen in humans. Recent studies have demonstrated that metals are critical factors for the regulation of fungal virulence in hosts. In this study, we systemically investigated the function of C. neoformans magnesium transporters in controlling the intracellular Mg balance and virulence-associated factors. We identified three Mg transporters in C. neoformans: Mgt1, Mgt2, and Mgt3. While we could not detect a Mg2+ -related growth phenotype in mgt1 and mgt3 knockout strains, a GAL7p-Mgt2 strain showed significant Mg-dependent growth defects in the presence of glucose. Further analysis demonstrated that MGT2 is a homolog of MNR2 in Saccharomyces cerevisiae, which is localized to the vacuolar membrane and participates in intracellular Mg transport. Interestingly, a transcriptome analysis showed that Mgt2 influenced the expression of 19 genes, which were independent of Mg2+ . We showed that melanin synthesis in C. neoformans required Mg2+ and Mgt2, and that capsule production was negatively regulated by Mg2+ and Mgt2. Repressing the expression of MGT2-induced capsule, which resulted in an increased fungal burden in the lungs. Cumulatively, this study sets the stage for further evaluation of the important role of Mg homeostasis in the regulation of melanin and capsule in C. neoformans.