Expression of filaggrin-2 protein in the epidermis of human skin diseases: a comparative analysis with filaggrin.

Filaggrin-2 is a member of the S100 fused-type protein family, and the structural features and expression of filaggrin-2 are similar to those of profilaggrin, a protein essential for keratinization. In the present study, we investigated the expression profile of filaggrin-2 in patients with skin diseases using antibodies against the repetitive region of filaggrin-2. In tissue samples from patients with skin diseases which are associated with a decrease in filaggrin, including ichthyosis vulgaris, atopic dermatitis and psoriasis vulgaris, the expression level of filaggrin-2 was markedly decreased compared to that in normal skin samples. In contrast, the expression of filaggrin-2 increased in parallel with that of filaggrin in samples of tissue from patients with skin diseases associated with hyperkeratosis, such as lichen planus and epidermolytic ichthyosis. Interestingly, filaggrin-2 signals were observed in slightly higher layers of the epidermis in comparison to those of filaggrin. Similarly, the expression of filaggrin-2 proteins was induced slightly later than filaggrin in the cultured keratinocytes. These findings suggest that filaggrin-2 may play an overlapping role with filaggrin in epithelial cornification; however, it may also have a partially distinct role in the molecular processes of cornification.