Lipid transport by Candida albicans Dnf2 is required for hyphal growth and virulence

Abstract

Candida albicans is a common cause of human mucosal yeast infections, and invasive candidiasis can be fatal. Antifungal medications are limited, but those targeting the pathogen cell wall or plasma membrane have been effective. Therefore, virulence factors controlling membrane biogenesis are potential targets for drug development. P4-ATPases contribute to membrane biogenesis by selecting and transporting specific lipids from the extracellular leaflet to the cytoplasmic leaflet of the bilayer to generate lipid asymmetry. A subset of heterodimeric P4-ATPases, including Dnf1-Lem3 and Dnf2-Lem3 from Saccharomyces cerevisiae, transport phosphatidylcholine (PC), phosphatidylethanolamine (PE), and the sphingolipid glucosylceramide (GlcCer). GlcCer is a critical lipid for Candida albicans polarized growth and virulence, but the role of GlcCer transporters in virulence has not been explored. Here we show that the Candida albicans Dnf2 (CaDnf2) requires association with CaLem3 to form a functional transporter and flip fluorescent derivatives of GlcCer, PC and PE across the plasma membrane. Mutation of conserved substrate-selective residues in the membrane domain strongly abrogates GlcCer transport and partially disrupts PC transport by CaDnf2. Candida strains harboring dnf2 null alleles (dnf2??) or point mutations that disrupt substrate recognition exhibit defects in the yeast to hyphal growth transition, filamentous growth and virulence in systemically infected mice. The influence of CaDNF1 deletion on the morphological phenotypes is negligible although the dnf1?? dnf2?? strain was less virulent than the dnf2?? strain. These results indicate that the transport of GlcCer and/or PC by plasma membrane P4-ATPases is important for pathogenicity of Candida albicans.

Two distinct lipid transporters together regulate invasive filamentous growth in the human fungal pathogen Candida albicans

“…The average hyphal filament length at 90 min was, nonetheless, slightly reduced in dnf2 cells as well as in dnf1 dnf2 (14 ± 3 μm and 13 ± 3 μm, respectively) compared to the WT, dnf1 and dnf3 cells (20 ± 4 μm, 18 ± 4 μm and 20 ± 4 μm, respectively). These results are in agreement with very recent data, which also show that both a dnf2 and a dnf1 dnf2 mutant exhibit reduced invasive filamentous growth in response to the nutrient poor spider media, another inducer of filamentous growth [38]. These data indicate that, in contrast to the drs2 deletion mutant, dnf1, dnf2 and dnf3 deletion mutants undergo filamentous growth similar to the wild-type cells, albeit with a reduced efficiency for dnf2.…”

Two distinct lipid transporters together regulate invasive filamentous growth in the human fungal pathogen Candida albicans

“…The average hyphal filament length was, nonetheless, slightly reduced in dnf2 cells as well as in dnf1 dnf2 (14 ± 3 µm and 13 ± 3 µm, respectively) compared to the WT, dnf1 and dnf3 cells (20 ± 4 µm, 18 ± 4 µm and 20 ± 4 µm, respectively). These results are in agreement with very recent data, which also show that both a dnf2 and a dnf1 dnf2 mutant exhibit reduced invasive filamentous growth in response to the nutrient poor spider media, another inducer of filamentous growth [38]. These data indicate that, in contrast to the drs2 deletion mutant, dnf1, dnf2 and dnf3 deletion mutants undergo filamentous growth similar to the wild-type cells, albeit with a reduced efficiency for dnf2.…”