IMMUNOCYTOCHEMICAL LOCALIZATION OF LYSOSOMAL CYSTEINE AND ASPARTIC PROTEINASES, AND UBIQUITIN IN RAT EPIDERMIS

To analyze the degradation system in epidermal cells during their gene ration, differentiation, and cell death, immunocytochemical localizati on of lysosomal cysteine and aspartic proteinases, an endogenous cyste ine proteinase inhibitor, cystatin beta, and ubiquitin were examined u sing rat sole skin. By confocal laser microscopy, granular immunodepos its for lysosomal proteinases were well demonstrated in epidermal cell s; immunoreactivity for cathepsins B and C was prominent in the lower spinous and basal layers, while that for cathepsins L and D was intens e in the upper spinous and granular layers, although immunoreactivity for cathepsin D was also detected in the lower epidermal layers. Immun oreactivity for cathepsin H was weakly detected only in the spinous la yer, where there were some intensely immunopositive cells with process es which were also immunopositive for S-100 alpha, indicating that the se cells were Langerhans cells, Diffuse immunoreactivity for cystatin beta was intense in the spinous and granular layers and weak in the ba sal layer, In addition, we also examined the localization of ubiquitin , which is a signal peptide for cytosolic proteolysis; clear-cut granu lar immunodeposits for ubiquitin were detected in spinous and granular cells, and some were eo-localized with cathepsin B immunoreactivity. In the basal layer, mitotic cells were strongly immunopositive for ubi quitin. These results suggest that cysteine and aspartic proteinases a re involved in the lysosomal system of the epidermis, showing differen t distributions in the epidermal layers depending on the enzymes exami ned, Moreover, ubiquitin may be associated with the cell cycle-depende nt degradation in basal cells while it also participates in the non-ly sosomal proteolysis and probably, lysosomal proteolysis in the spinous and granular cells.