EAP1, a Candida albicans gene involved in binding human epithelial cells

Candida albicans adhesion to host tissues contributes to its virulence and adhesion to medical devices permits biofilm formation, but we know relatively little about the molecular mechanisms governing C. albicans adhesion to materials or mammalian cells. Saccharomyces cerevisiae provides an attractive model system for studying adhesion in yeast because of its well-characterized genetics and gene expression systems and the conservation of signal transduction pathways among the yeasts. In this study, we used a parallel plate flow chamber to screen and characterize attachment of a flo8Delta S. cerevisiae strain expressing a C. albicans genomic library to a polystyrene surface. The gene EAP1 was isolated as a putative cell wall adhesin. Sequence analysis of EAP1 shows that it contains a signal peptide, a glycosylphosphatidylinositol anchor site, and possesses homology to many other yeast genes encoding cell wall proteins. In addition to increasing adhesion to polystyrene, heterologous expression of EAP1 in S. cerevisiae and autonomous expression of EAP1 in a C. albicans efg1 homozygous null mutant significantly enhanced attachment to HEK293 kidney epithelial cells. EAP1 expression also restored invasive growth to haploid flo8Delta and flo11Delta strains as well as filamentous growth to diploid flo8/flo8 and flo11/flo11 strains. Transcription of EAP1 in C. albicans is regulated by the transcription factor Efg1p, suggesting that EAP1 expression is activated by the cyclic AMP-dependent protein kinase pathway.