Intracellular aspartic proteinase Apr1p of Candida albicans is required for morphological transition under nitrogen-limited conditions but not for macrophage killing

摘要

Vacuolar hydrolases have been thoroughly characterized in Saccharomyces cerevisiae, but their homologues in the fungal pathogen Candida albicans have received less attention. The genes APR1 and CPY1 of C. albicans encode putative vacuolar aspartic proteinase and serine carboxypeptidase, respectively. We examined properties of apr1 Delta and cpy1 Delta mutants, showing that Cpy1p molecular species detected in cell lysates of apr1 Delta and its parental strain did not differ in molar mass. Processing of Cpy1p precursor is apparently independent of Apr1p. This is in contrast to S. cerevisiae, where vacuolar aspartic proteinase Pep4p is known to participate in the activation of other vacuolar hydrolases including serine carboxypeptidase. We also found that both apr1 Delta and cpy1 Delta strains are able to form hyphae in nutrient-rich filamentation media. However, proline as a sole nitrogen source induced filamentation only in cpy1 Delta and its parental strain, but not in apr1 Delta. This indicates the importance of Apr1p for the morphological transition under nitrogen-limited conditions. Despite that, the ability of apr1 Delta to kill murine macrophages was not reduced under the conditions tested.