The KEX2 gene of Candida glabrata is required for cell surface integrity

Candida glabrata has emerged as one of the most common causes of candidosis . In order to identify factors that are necessary for viability and pathoge nicity of this fungal pathogen, we analysed the role of the KEX2 gene, whic h codes for a regulatory endoproteinase that is known to process certain vi rulence factors in Candida albicans. The KEX2 gene from C. glabrata was clo ned and found to have 51% and 62% identity and high structural similarities to the homologous counterparts in C. albicans and Saccharomyces cerevisiae . KEX2 was expressed at all time points investigated during growth in compl ex medium. In order to investigate the role of this putative regulatory pro teinase, Kex2-deficient mutants were produced. In addition to known kex2 ph enotypes, such as pH and calcium hypersensitivity, the mutants grew in cell ular aggregates and were found to be hypersensitive to several antifungal d rugs that target the cell membrane, including azoles, amorolfine and amphot ericin B. Ultrastructural investigation after exposure to low doses of itra conazole showed azole-specific alterations such as enlarged vacuoles and pr oliferation of the cytoplasmatic membrane in the kex2 mutants, but not in t he control strains. In contrast, antifungals such as 5-flucytosine and hydr oxypyridones inhibited growth of the kex2 mutants and the control strains t o the same extent. In an in vitro model of oral candidosis, kex2 mutants sh owed reduced tissue damage in the presence of itraconazole compared with th e control infections. These data suggest that Kex2 is involved in the proce ssing of proteins that are essential for cell surface integrity of C. glabr ata.