Epidermal Protein Kinase C-β2 Is Highly Sensitive to Downregulation and Is Exclusively Expressed in Langerhans Cells: Downregulation Is Associated with Attenuated Contact Hypersensitivity

Treatment of mice with multiple topical applications of 12-O-tetradecanoylphorbol-13-acetate (TPA) or diacylglycerol resulted in a preferential decrease in epidermal protein kinase C-β2 (PKC-β2) compared with PKC-α as determined by western analysis. When PKC-α was decreased by 40%, PKC-β2 could no longer be detected, suggesting that PKC-β2 is more sensitive to downregulation, and/or specific epidermal cell types that contain PKC-β2 are more sensitive to TPA/diacylglycerol. To address this issue, we isolated Langerhans cells (LCs) from epidermal cell suspensions with immunomagnetic beads and an antibody to the class II major histocompatibility complex. Northern blot analysis revealed a PKC-β2 signal in isolated LCs that was 40-fold greater than that observed in unfractionated epidermal cells, and no PKC-β2 signal was detected in epidermal cells depleted of LCs, indicating that PKC-β2 is expressed exclusively in LCs within the epidermis. Western blot analysis confirmed the presence of PKC-β2 in LCs, PKC-β2 was highly sensitive to downregulation, because a single application of TPA resulted in a 90% loss of PKC-β2 within 6h without a decrease in the number of LCs. To determine whether the decreased level of PKC-β2 within LCs was associated with an alteration in contact hypersensitivity, we treated mice with only a single application of TPA, and 6hours later mice were sensitized with 2,4-dinitrofluorobenzene on the same dorsal area. Subsequent challenge revealed a 60% decrease in contact hypersensitivity in TPA-treated mice. These data indicate that (i) within the epidermis, PKC-β2 is associated with impaired LC functions with respect to contact hypersensitivity