The outer layer of the
epidermis is called the
stratum corneum. In the stratum corneum terminally differentiated corneocytes are held together by corneodesmosomes. In order for
desquamation to occur, corneodesmosomes need to be fully degraded.
KLK5 and
KLK7 are two serine proteases that degrade corneodesmosomes. LEKTI-2 regulates corneodesmosome degradation by inhibiting KLK5. In acral (palm and sole) skin, where desquamation needs to be delayed,
SPINK9 expression is strongly upregulated. The resulting high level of LEKTI-2 delays corneodesmosome degradation, thereby allowing the epidermis to form a thick protective stratum corneum layer. ==Clinical Significance==