The Role of Core Virulence Kinase Bud32 in Iron Homeostasis Regulation in Cryptococcus neoformans

The core virulence kinase Bud32, which is critical for lung and brain infections, influences the production of major virulence factors in Cryptococcus neoformans, including capsule formation, melanin production, and growth at 37°C. This study explores the role of Bud32 in regulation of iron homeostasis in C. neoformans. Bud32 was required for growth under iron limiting condition. Loss of Bud32 resulted in significant alterations in the expression of proteins related to iron binding and iron-sulfur cluster assembly. Moreover, metabolic profiling identified 696 metabolites that were up-regulated and 480 that were down-regulated in the bud32 deletion mutant, highlighting the significant impact of Bud32 loss on intracellular metabolite levels. In particular, the levels of biliverdin, which is primarily derived from heme, showed a significant decrease in the absence of Bud32. Furthermore, Bud32 has been demonstrated to modulate iron-sulfur cluster assembly, likely influencing the interaction between the iron-sulfur binding protein Grx4 and the iron regulatory factors Cir1 and HapX. Phosphorylation analysis revealed that the deletion of Bud32 caused widespread changes in the phosphorylation status of various proteins, including the iron regulatory factors Cir1 and Rim101. These findings indicate that the Bud32 kinase plays a vital role in regulating iron homeostasis in C. neoformans.