A Glycolysis-Calcineurin Regulatory Axis Orchestrates Titan Cell Formation in Cryptococcus neoformans

Transcriptomic analyses revealed significant downregulation of a large subset of calcineurin-responsive genes in the hxk2Δ mutant, many of which were restored upon cAMP supplementation. Consistent with these findings, pharmacological inhibition of calcineurin using FK506 or cyclosporin A markedly reduced titan cell formation, establishing an essential role for calcineurin signaling in this morphological transition. Furthermore, supplementation with calcium chloride rescued the titanization defect of the hxk2Δ mutant, whereas chelation of extracellular calcium with EGTA significantly inhibited titanization in wild-type cells.

Using the calcium-sensitive dye, we found that intracellular calcium levels were substantially reduced in the hxk2Δ mutant and were restored by calcium chloride or cAMP supplementation. Collectively, our findings uncover a previously unrecognized glycolysis–calcineurin regulatory axis that governs titan cell formation and establishes a direct mechanistic link between central carbon metabolism, calcium homeostasis and fungal morphogenesis.