Melanosome degradation in epidermal keratinocytes related to lysosomal protease cathepsin V

In this study, we focused on a lysosomal protease cathepsin V (CTSV) to clarify the mechanism underlying melanosome degradation in the keratinocytes. Using immunohistochemical observation, we found that CTSV was highly expressed across the entire epidermis in normal skin; however, CTSV expression levels were lower in the basal layer than those in the stratum corneum side in the hyperpigmented region. Moreover, we found that melanosome degradation was suppressed in CTSV knockdown cells. These results indicated that CTSV is involved in melanosome degradation.