Candida albicans aspartic proteinase cleaves and inactivates human epidermal cysteine proteinase inhibitor, cystatin A

It is known that the cysteine proteinase inhibitor, cystatin, has a defence function against exogenous pathogens. Human epidermal cysteine proteinase inhibitor, cystatin A, which is a member of the cystatin family, is localized in the upper epidermal layer. In this study, the relationship between cystatin A and Candida aspartic proteinase (CAP), a putative Candida virulence factor, was studied. CAP activity was not affected by human epidermal cystatin A, while 90% of cystatin A activity was lost after incubation with CAP for 12 h at 37°C. Human epidermal cystatin A was cleaved into small peptides by CAP, and the released peptides had no cystatin activity. These results suggest that CAP may induce an imbalance between cysteine proteinase and its inhibitor in cutaneous Candida infectious lesions through the degradation and inactivation of epidermal cystatin A.