Vacuolar H+-ATPase regulates cell size through Rim101 mediated mitochondrial function in Cryptococcus neoformans

Cell size control is a fundamental aspect of cell biology. The pathogenic fungus Cryptococcus neoformans increases in cell size by several orders of magnitude during infection, making it an excellent model system for studying cell size regulation. A single large vacuole occupies a substantial proportion of the cell volume in enlarged C. neoformans cells. Here, we demonstrate that vacuolar H+-ATPase (V-ATPase) is critical for cell enlargement. Disruption of genes encoding individual V-ATPase subunits impairs vacuolar enlargement and nearly abolishes titan cell formation. Titan cell production is associated with acidification of both the extracellular environment and the vacuole. Changes in cellular pH regulate the expression and localization of Rim101, which in turn upregulates the expression of V-ATPase subunits and the transcription factor Mig1. Nuclear accumulation of Mig1 may contribute to reactive oxygen species production and promote cell enlargement in both wild-type and rim101Δ mutant strains. Overall, our study provides insights into a vacuole-dependent mechanism of cell size regulation. Vacuolar H+-ATPase is critical for cell enlargement in Cryptococcus neoformans. The pH-Rim101 pathway and mitochondrial respiratory chain activity may be involved in vacuole-mediated cell size regulation.