| The Candida glabrata genome encodes at least twenty-three members of the epithelial adhesin (Epa) family of proteins, a subset of which have been functionally demonstrated to be responsible for mediating adherence to host cells. To better understand the mechanism by which the Epa proteins contribute to pathogenesis, glycan microarray analysis was used to characterize their carbohydrate binding specificities. The three major adhesins in Candida glabrata (Epa1, Epa6, and Epa7) were found to bind to ligands containing a terminal galactose residue, and within this broad class of ligands specific binding determinants recognized by each of the three proteins were identified. Overall, Epa6 has a much broader ligand specificity range than Epa7, an intriguing result given that these two proteins are 92% identical at the amino acid level. The sugar specificity region of Epa6 and Epa7 was mapped to a five-amino-acid region within the N-terminal ligand-binding domain.;To identify additional Epa family members involved in mediating adherence of C. glabrata to host cells, a method to analyze the functions of all known Epa proteins in parallel was developed. Using this method, three additional Epa proteins responsible for mediating adherence to physiologically relevant cell types---Epa12, Epa15, and Epa23---were identified. Glycan microarray results indicate that Epa12 and Epa23 bind specifically to sulfated lactose derivatives. Finally, Epa12 was found to mediate adherence to mitral valve tissue in a manner inhibited by the glycosaminoglycan chondroitin sulfate B. Taken together, the work presented in this thesis expands our knowledge of the Epa family by characterizing the ligand binding properties of both previously and newly identified Epa adhesins. |
