Phenotypic and proteomic characterization of Dbr48, a candida albicans cell wall protein. (c2018)

Abstract

The fungus Candida albicans is an opportunistic pathogen that possesses multiple factors and mechanisms that control virulence. The most important virulence factors and antigenic determinants are the cell wall proteins as they are the first elements contacting the host. Ddr48 is a cell wall protein consisting of 212 amino acids. This protein had been previously studied where it was found to be required for tolerance to hydrogen peroxide oxidative stress, drug resistance, filamentation and virulence. DDR48 was found to be haploid insufficient and essential as only a heterozygous strain was generated and not a homozygous null strain. In this study, we aimed to further elucidate the role of Ddr48 by subjecting our DDR48 heterozygous strain to a battery of assays in order to achieve additional phenotypic characterization. In addition, a proteomic approach was utilized to determine differentially expressed cell wall proteins detected exclusively in the wild type strain. Our results showed that the heterozygous mutant strain exhibited a 10% decrease in adhesion mirrored by a 20% decrease in biofilm formation, and a slight sensitivity to oxidative stress agents and SDS. Both strains showed similar hyphae formation ability, temperature tolerance, calcofluor white and Congo red sensitivities, chitin content, and virulence. For proteomic characterization, a total of 8 and 10 proteins were identified exclusively in the wild type strain grown under filamentous and non-filamentous conditions respectively. These proteins included members of the superoxide dismutase family required for resisting superoxide stress such as Sod4 and Sod6. Additionally, proteins responsible for adhesion (Als3, Hyr4, Pmt1, and Utr2), biofilm formation (Hsp90, Ece1, Rim9, Ipp1, and Pra1) and cell wall integrity (Utr2 and Pga4) were found. The lack of detection of these proteins in the heterozygous mutant strain go a long way in explaining the observed phenotypes.