Protein kinase C alpha, delta, epsilon and zeta in C6 glioma cells. TPA induces translocation and down-regulation of conventional and new PKC isoforms but not atypical PKC zeta.

Both the cytosol and membrane in C6 glioma cells express abundance of PKC alpha, delta, zeta and trace amount of PKC epsilon by Western blot analysis with isozyme-specific antibodies. These characteristics make this cell line a good model to study the properties of different classes of PKC isoforms in one cell type. Exposure of the cells to 100 nM TPA for 10 min resulted in the translocation of conventional PKC alpha (cPKC alpha) and new PKC delta (nPKC delta) and -epsilon from the cytosolic to the membrane fraction, while left atypical PKC zeta (aPKC zeta) unaffected. The extent of translocation of cPKC alpha induced by TPA was more prominent than that of nPKC delta and nPKC epsilon. alpha-TPA, the inactive phorbol ester, did not induce translocation of these isozymes. After treatment of the cells with 1 microM TPA for 17 h, cPKC alpha, nPKC delta and nPKC epsilon were almost completely down-regulated, whereas aPKC zeta was still unaffected. The natural activators of this cell line, endothelin-1 and ATP also translocated cPKC alpha and nPKC delta. However, the extent of translocation induced by these two agonists was much less than that of TPA.