BAR Domain Proteins Rvs161 and Rvs167 Contribute to Candida albicans Endocytosis, Morphogenesis, and Virulence

The Candida albicans plasma membrane plays critical roles in growth and virulence and as a target for antifungal drugs. Three C. albicans genes that encode Bin-Amphiphysin-Rvs homology domain proteins were mutated to define their roles in plasma membrane function. The deletion of RVS161 and RVS167, but not RVS162, caused strong defects. The rvs161 Delta mutant was more defective in endocytosis and morphogenesis than rvs167 Delta, but both were strongly defective in polarizing actin patches. Other plasma membrane constituents were still properly localized, including a filipin-stained domain at the hyphal tips. An analysis of growth under different in vitro conditions showed that the rvs161 Delta and rvs167 Delta mutants grew less invasively in agar and also suggested that they have defects in cell wall synthesis and Rim101 pathway signaling. These mutants were also more resistant to the antimicrobial peptide histatin 5 but showed essentially normal responses to the drugs caspofungin and amphotericin. Surprisingly, the rvs161 Delta mutant was more sensitive to fluconazole, whereas the rvs167 Delta mutant was more resistant, indicating that these mutations cause overlapping but distinct effects on cells. The rvs161 Delta and rvs167 Delta mutants both showed greatly reduced virulence in mice. However, the mutants were capable of growing to high levels in kidneys. Histological analyses of infected kidneys revealed that these rvs Delta mutants grew in a large fungal mass that was walled off by leukocytes, rather than forming disseminated microabscesses as seen for the wild type. The diminished virulence is likely due to a combination of the morphogenesis defects that reduce invasive growth and altered cell wall construction that exposes proinflammatory components to the host immune system.