Differentiation-Associated Localization of nPKCμ, a Ca++-Independent Protein Kinase C, in Normal Human Skin and Skin Diseases

The expression of nPKCμ, a Ca++-independent isoform of protein kinase C in normal human skin, and skin from patients with psoriasis, squamous cell carcinoma, basal cell epithelioma, nevus pigmentosus, and seborrheic keratosis, were examined by immunohistochemical staining using a polyclonal antibody raised against a synthetic peptide at a diverse region of the nPKCμ molecule. In normal epidermis, the strongest staining was observed in the uppermost granular layer with no staining of the spinous or basal layers. The inner layer of the intra-epidermal eccrine duct was also strongly stained. Weak staining was observed in several layers of the outer root sheath of the follicular infundibulum. No staining was detected in the inner root sheath of the hair follicles, hair matrix, sebaceous gland, eccrine gland, intradermal eccrine duct, arrectores pilorum, melanocytes, Langerhans cells, fibroblasts, or blood vessels. In psoriatic skin, stained keratinocytes were distributed in the suprabasal layers with the most being observed in the uppermost layer and the least in layers closed to the basal layer. In squamous cell carcinoma, weak staining was observed in the keratotic cells around horny pearls. In the basal cell epithelioma and nevus pigmentosus, the cells were not stained, whereas in seborrheic keratosis, cells that stained were located in the granular layer. We conclude from the evidence presented above that nPKCμ is expressed in close association with epidermal differentiation in normal skin and skin diseases