A Conserved Metabolic Network Regulates Titan Cell Formation in Cryptococcus neoformans

Cryptococcus neoformans is an opportunistic fungal pathogen that primarily causes pulmonary infections, with the potential to cause life-threatening infections including meningoencephalitis in immunocompromised individuals. Key virulence factors including polysaccharide capsule and melanin, facilitate immune evasion and tissue invasion in the host. Recently, Titan cell formation, has been defined as another important virulence factor of C. neoformans and plays a pivotal role in disease progression. Titan cells are defined as enlarged cells with a diameter of ≥10 µm and are highly polyploid with a significantly thicker capsule compared to the yeast morphotype. Despite the established role of Titan cells in C. neoformans pathogenesis, the mechanistic details governing their formation remain largely unresolved. The cyclic AMP–protein kinase A (cAMP-PKA) pathway has been shown to be an important regulator of virulence-associated processes, including capsule formation, melanin biosynthesis and Titan cell formation. However, the upstream signals, critical for the activation of cAMP-PKA pathway in the context of Titan cell formation remain poorly understood. In this study, for the first time, we demonstrate that the central carbon metabolic pathway, glycolysis, is critical for cAMP-dependent Titan cell formation in C. neoformans . Pharmacological and genetic perturbation of glycolysis significantly attenuated Titan cell formation. Remarkably, exogenous addition of cAMP completely reversed the Titan cell defects observed during glycolysis perturbation. These findings establish a novel regulatory axis wherein central carbon metabolism orchestrates morphogenetic switching in C. neoformans by regulating the activity of the well conserved cAMP-PKA pathway, providing new insights into the metabolic control of C. neoformans dimorphism.