BREFELDIN-A BLOCKS AN EARLY STAGE OF PROTEIN-TRANSPORT IN CANDIDA-ALBICANS

Brefeldin A (BFA) inhibited in a dose-dependent manner secretion of the cell-surface enzyme acid phosphatase (APase) into the periplasm of Candida albicans and caused intracellular accumulation of enzyme protein. Cells grown in the presence of BFA became more dense, implying that cell-surface growth was also blocked by BFA treatment. The APase that was accumulated intracellularly migrated faster on SDS-PAGE, suggesting less N-linked glycosylation compared with the mature, periplasmic APase produced in the absence of BFA. Pulse-chase experiments and gel-filtration of oligosaccharides released by Endo H treatment suggested that the core-glycosylated precursor form of APase accumulated in the presence of BFA. These results strongly suggested that endoplasmic reticulum (ER)-to-Golgi transport in C. albicans was inhibited by BFA. Aberrant membrane structures were observed in BFA-treated cells. Within 1 h of BFA removal these structures were replaced with rough ER membranes, suggesting that the accumulated membranes were derived from the ER.