FIG 1.

APT1 deletion does not affect the global flippase activity of C. neoformans. (A) Determination of phosphatidylserine (PS) exposure after treatment of fungal cells with FITC-annexin V reveals similar profiles of partial staining in wild-type (WT), mutant (apt1Δ), and complemented (apt1Δ::APT1) strains. Scale bar, 10 μm. (B) Analysis of the uptake of NBD-PS, a fluorescent analog of PS, by WT and mutant cells reveals that both strains were similarly efficient in incorporating the phospholipid derivative (red histograms) in comparison to unstained cells (black histograms). Treatment of C. neoformans cells with PBS-BSA for sequestration of NBD-PS molecules distributed into the external phospholipid layer of the plasma membrane resulted in cells with similar levels of fluorescence (blue histograms). (C and D) Accordingly, the levels of PS translocation were similar in WT and apt1Δ cells (C), as were the residual amounts of NBD-PS in the supernatants of cells that were washed with PBS alone or with PBS-BSA (D). P values resulting from the statistical comparison between WT and apt1Δ cells were higher than 0.5 in all cases.