A novel histone-stimulated protein kinase in normal and psoriatic epidermis

Protein kinase C in normal human epidermal keratinocytes during proliferation and calcium-induced differentiation

Recent evidence has implicated protein kinase C (PKC) in the etiology of hyperproliferative diseases such as psoriasis and non-melanoma skin cancer. In this study, PKC activity, immunoreactive protein, and phorbol ester-binding kinetics were examined in primary cultures of normal human epidermal keratinocytes (NHEK) in order to elucidate the relationship between PKC and NHEK proliferation and differentiation. NHEK were maintained in a proliferative phase in serum-free low-calcium (0.15 mM) medium, and then were exposed to high calcium (1.6 mM) in order to stimulate growth arrest and differentiation. Staurosporine was inhibitory to Ca(++)-induced differentiation. Scatchard analysis of phorbol binding indicated that exposure to high calcium for 24 h increased the number of binding sites (Bmax) by fivefold. In correlation with the ligand-binding results, PKC activity was extremely low in proliferating (low-calcium) NHEK compared to differentiating cells (high calcium). When assayed after 24, 48, and 72 h, high calcium induced tenfold or greater increases in Ca++/phospholipid-dependent phosphotransferase activity. Immunoblot analysis of NHEK PKC using antibodies directed against the hinge region of PKC alpha/beta also indicated that exposure to high calcium resulted in higher levels of immunoreactive protein. Therefore, PKC in NHEK appears to be upregulated under conditions of Ca(++)-induced growth arrest and differentiation. In addition, NHEK and other human skin cell particulate fractions contain a protein of approximately 116 kDa that is highly immunoreactive to an antibody to PKC alpha/beta, which coelutes from DEAE-sephacel under the same buffer conditions as the 80-kDa PKC.

H1 histones contribute to candidacidal activities of human epidermal extract

In the study of the purification of candidacidal cationic proteins from human epidermis by using high performance liquid chromatography, it was found that these proteins were composed of several groups. Among them, the most active group was purified. The amino acid compositions of this protein group were almost the same as those of human splenic H1 histones. The results of immunoblotting suggested that the proteins were human epidermal H1 histones. The killing speed of the epidermal H1 histone was very rapid, 8 micrograms of the protein killed 90% of Candida tropicalis (1 x 10(5) CFU) within 10 minutes. The cidal activity increased in lower pH conditions and decreased at higher ionic strengths. Because nuclei of the epidermis disintegrate in the granular layer, it is suggested that, in this layer, nuclear histones may be released from the nuclei. My immunohistochemical results suggest that H1 histones may contribute to form a barrier which inhibits candida from invading deeper than the granular cell layer in cases of skin candidial infection.