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

TheCandida albicans plasma membrane plays critical roles in growth and virulence and as a target for antifungal drugs. ThreeC. albicans genes that encode Bin-Amphiphysin-Rvs homology domain proteins were mutated to define their roles in plasma membrane function. The deletion ofRVS161 andRVS167 , but notRVS162 , caused strong defects. Thervs161 Δ mutant was more defective in endocytosis and morphogenesis thanrvs167 Δ, 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 thervs161 Δ andrvs167 Δ 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, thervs161 Δ mutant was more sensitive to fluconazole, whereas thervs167 Δ mutant was more resistant, indicating that these mutations cause overlapping but distinct effects on cells. Thervs161 Δ andrvs167 Δ 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 theservs Δ 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.