The vacuolar protein 8 (Vac8) homolog inCryptococcus neoformansplays conserved and unique roles in vacuolar and cellular morphology, impacting important stress responses and virulence traits

Functionally similar to a plant vacuole or a mammalian lysosome, the fungal vacuole plays a vital role in many cellular processes. Most studies of the vacuole have been performed in the nonpathogenic yeastSaccharomyces cerevisiae; however, recently in pathogenic fungi, the vacuole has been implicated in host invasion in both plants and mammals highlighting an important role for the vacuole in pathogenesis. Here, we report that deletion ofCryptococcus neoformansvacuolar protein 8 (VAC8) results in a fragmented vacuole morphology, impairment of vacuolar fusion, and inability to form titan cells. Additionally, absence of Vac8 results in defective growth at high temperature and in the presence of caffeine, suggesting a defect in cell wall signaling. Interestingly, despite aberrant vacuole morphology,vac8Δis slightly more resistant to fluconazole treatment, and displays increased resistance to hydrogen peroxide, suggesting the irregular vacuole morphology does not impair vacuole function. LikeS. cerevisiaeVac8,C. neoformansVac8 is comprised of armadillo repeat regions which form alpha helices that fold to form a superhelix allowing for increased protein-protein interaction. Many of the known binding partners ofS. cerevisiaeVac8 are not present in theC. neoformansgenome, suggesting novel functions for Vac8 in this fungus. Notably, deletion ofVAC8affected some virulence traits, providing support to targeting the fungal vacuole as a potential therapeutic intervention.