Protein kinase C zeta and eta in murine epidermis. TPA induces down-regulation of PKC eta but not PKC zeta.

Murine epidermis contains PKC zeta and eta as evidenced by the application of specific antisera. PKC zeta predominates in the cytosol and PKC eta in the particulate fraction. PKC zeta is shown to be present also in other murine tissues, with large amounts found in lung. Whereas epidermal PKC eta is completely down-regulated by treatment of mouse skin with TPA or bryostatin 1 for 18 h, PKC zeta is neither translocated by treatment with TPA for 20 min, nor down-regulated by treatment with TPA or bryostatin 1 for 18 h. PKC zeta is activated by phosphatidyl serine alone and does neither respond to Ca2+ nor to TPA. It is inhibited by staurosporine with an IC50 of 16 nM, which is within the same range of other PKC isoenzymes. The sensitivity of PKC zeta towards the staurosporine derivative K252a is similar to that of PKC alpha,beta,gamma but much higher than that of PKC delta and epsilon.