RESUMO
A balanced proteolytic activity in the epidermis is vital to maintain epidermal homoeostasis and barrier function. Distinct protease-inhibitor systems are operating in different epidermal layers. In the uppermost layer, the stratum corneum, kallikrein-like proteases and their inhibitors are responsible for desquamation of the cornified keratinocytes, thus regulating the integrity of the epidermal barrier. Following discovery and characterisation of the human multidomain inhibitor LEKTI (lympho-epithelial Kazal-type-related inhibitor, encoded by hspink5), several new members of the Kazal-type inhibitor family have been identified. Here we describe expression and regulation of murine SPINK12, a potential orthologue of human LEKTI2. Its expression was analysed by RT-PCR and immunohistochemistry revealing organ-specific pattern with high level of expression in the epidermis and several epithelia including the stomach, kidney and uterus. In addition, mSPINK12 expression in the epidermis of skin at footpads, where stratification is markedly pronounced, was several folds higher than in the abdominal epidermis. mSPINK12 mRNA levels were not affected by any cytokines tested while treatment of primary murine keratinocytes with the combination of calcium and sorbitol resulted in a strong increase in its mRNA. It appears that mspink12 is especially expressed in the epidermal areas with thick skin and that its regulation generally responds to differentiation signals. mrSPINK12 shows an inhibitory activity against murine keratinocyte-derived trypsin-like proteolytic activity, thus, the protein does appear orthologous to human LEKTI2 and may play an role in the regulation of epithelial cell functions.
Assuntos
Proteínas Secretadas Inibidoras de Proteinases/genética , Proteínas Secretadas Inibidoras de Proteinases/metabolismo , Pele/metabolismo , Sequência de Aminoácidos , Animais , Sequência de Bases , Células Cultivadas , DNA Complementar/genética , Feminino , Regulação da Expressão Gênica , Humanos , Imuno-Histoquímica , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Dados de Sequência Molecular , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Inibidores de Serinopeptidase do Tipo Kazal , Especificidade da EspécieRESUMO
The proteolytic regulation of the desquamation process by kallikrein-related peptidases (KLKs) is crucial for epidermal barrier function, and elevated KLK levels have been reported in atopic dermatitis. KLKs are controlled by specific inhibitors of the serine protease inhibitor of Kazal-type (Spink) family. Recently, SPINK6 was shown to be present in human stratum corneum. In order to investigate its role in epidermal barrier function, we studied mouse Spink6. Sequence alignment revealed that the Kazal domain of Spink6 is highly conserved in animals. Recombinant Spink6 efficiently inhibited mouse Klk5 and human KLK2, KLK4, KLK5, KLK6, KLK7, KLK12, KLK13, and KLK14, whereas human KLK1 and KLK8 were not inhibited. Spink6 was expressed in mouse epidermis mainly in the stratum granulosum, and the inner root sheath of hair follicles. Stimulation with flagellin, EGF, and IL-1ß did not alter Spink6 expression, whereas stimulation with tumor necrosis factor-α (TNFα)/IFNγ and all-trans retinoic acid resulted in a significant downregulation of Spink6 expression in cultured primary mouse keratinocytes. Mechanically and metabolically induced skin barrier dysfunction resulted both in a downregulation of Spink6 expression. Our study indicates that Spink6 is a potent inhibitor of KLKs and involved in skin barrier function.