EVIDENCE THAT STRATUM-CORNEUM CHYMOTRYPTIC ENZYME IS TRANSPORTED TO THE STRATUM-CORNEUM EXTRACELLULAR-SPACE VIA LAMELLAR BODIES

Stratum corneum chymotryptic enzyme (SCCE) is a recently discovered hu man serine proteinase that may be specific for keratinizing squamous e pithelia. SCCE has properties compatible with a function in the degrad ation of intercellular cohesive structures during stratum corneum turn over and desquamation. SCCE is expressed in suprabasal keratinocytes. In this study, we demonstrate the subcellular localization of SCCE in the upper granular layer, in the stratum corneum of normal non-palmopl antar skin, and in cohesive parts of hypertrophic plantar stratum corn eum, using immunoelectron microscopy of ultrathin cryosections labeled with SCCE-specific monoclonal antibodies detected with gold-labeled s econdary antibodies. A narrow zone close to the transition between the granular and cornified layers showed positive SCCE staining after fix ation. By means of immunoelectron microscopy, SCCE was found in associ ation with structures resembling in tracellular lamellar bodies in the uppermost granular cells and in similar structures undergoing extrusi on to the extracellular space between the uppermost granular cells and the lowermost cornified cells. In the stratum corneum, the detected S CCE was confined to the extracellular space and was found in associati on with intact and partially degraded desmosomes, as well as in the pa rts of the extracellular space devoid of desmosomes. We conclude that SCCE may be stored in lamellar bodies in the stratum granulosum and tr ansported via these structures to the stratum corneum extracellular sp ace. The results further support the idea that the physiologic functio n of SCCE may be to catalyze the degradation of desmosomes in the stra tum corneum during remodeling of the deeper layers of this tissue, and at a later stage serve as a prerequisite for desquamation.