Snf7p, a component of the ESCRT-III protein complex, is an upstream member of the RIM101 pathway in Candida albicans

The success of Candida albicans as an opportunistic pathogen is based in part on its ability to adapt to diverse environments. The RIM101 pathway governs adaptation to neutral-alkaline environments and is required for virulence. Analysis of a genomic two-hybrid study conducted with Saccharomyces cerevisiae revealed that components involved in multivesicular bodies (MVB) transport may interact with RIM101 pathway members. Thus, we hypothesized that these proteins may function in the RIM101 pathway in C. albicans. We identified C. albicans homologs to S. cerevisiae Snf7p, Vps4p, and Bro1p and generated mutants in the cognate gene. We found that snf7Delta/Delta mutants, but not vps4Delta/Delta nor bro1Delta/Delta mutants, had phenotypes similar to, but more severe than, those of RIM101 pathway mutants. We found that the constitutively active RIM101-405 allele partially rescued snf7Delta/Delta mutant phenotypes. The vps4Delta/Delta mutant had subtle phenotypes, but these were not rescued by the RIM101-405 allele. Further, we found that the snf7Delta/Delta, vps4Delta/Delta, and bro1Delta/Delta mutants did not efficiently localize the vital dye FM4-64 to the vacuole and that it was often accumulated in an MVB-like compartment. This phenotype was not rescued by RIM101-405 or observed in RIM101 pathway mutants. These results suggest that Snf7p may serve two functions in the cell: one as a RIM101 pathway member and one for MVB transport to the vacuole.