The water channel protein aquaporin 1 regulates cellular metabolism and competitive fitness in a global fungal pathogen Cryptococcus neoformans.

In this study, an aquaporin protein, Aqp1, in Cryptococcus neoformans, which can lead either saprobic or parasitic lifestyles and causes life-threatening fungal meningitis was identified and characterized. AQP1 expression was rapidly induced (via the HOG pathway) by osmotic or oxidative stress. In spite of such transcriptional regulation, Aqp1 was found to be largely unnecessary for adaptation to diverse environmental stressors, regardless of the presence of the polysaccharide capsule. The latter is shown here to be a key environmental-stress protectant for C. neoformans. Furthermore, Aqp1 was not required for the development and virulence of C. neoformans. Deletion of AQP1 increased hydrophobicity of the cell surface. The comparative metabolic profiling analysis of the aqp1Δ mutant and AQP1-overexpressing strains revealed that deletion of AQP1 significantly increased cellular accumulation of primary and secondary metabolites, whereas overexpression of AQP1 depleted such metabolites, suggesting that this water channel protein performs a critical function in metabolic homeostasis. In line with this result, it was found that the aqp1Δ mutant (which is enriched with diverse metabolites) survived better than the wild type and a complemented strain, indicating that Aqp1 is likely to be involved in competitive fitness of this fungal pathogen.