The emerging roles of serine protease cascades in the epidermis.

It has become clear in recent years that serine proteases have an important role in epidermal homeostasis, and the signaling cascades are gradually being identified. For example, matriptase, prostasin and furin are implicated in a cascade that could activate ENaC, leading to epidermal barrier formation and hydration, probably in part through their involvement in filaggrin processing. Kallikreins can form a signaling cascade to coordinate corneocyte desquamation.

Caspase-14 reveals its secrets.

Caspase-14 is a unique member of the evolutionarily conserved family of cysteinyl aspartate-specific proteinases, which are mainly involved in inflammation and apoptosis. However, recent evidence also implicates these proteases in proliferation and differentiation. Although most caspases are ubiquitously expressed, caspase-14 expression is confined mainly to cornifying epithelia, such as the skin.

Caspase-14 protects against epidermal UVB photodamage and water loss.

Caspase-14 belongs to a conserved family of aspartate-specific proteinases. Its expression is restricted almost exclusively to the suprabasal layers of the epidermis and the hair follicles. Moreover, the proteolytic activation of caspase-14 is associated with stratum corneum formation, implicating caspase-14 in terminal keratinocyte differentiation and cornification.