Differential correlation between translocation and down-regulation of conventional and new protein kinase C isozymes in C6 glioma cells.

Correlation between translocation and down-regulation of conventional protein kinase C alpha (cPKC alpha) and new PKC delta (nPKC delta) induced by 12-O-tetradecanoylphorbol 13-acetate (TPA) at different time courses (5 min, 30 min, 1 h, 3 h, 6 h, 10 h, 17 h, and 24 h) was studied in C6 glioma cells. From the dose-dependent translocations of these two isoforms by 10-min treatment with TPA (1, 3, 10, 30, 100, 300, and 1,000 nM), we found that cPKC alpha was translocated by 3-1,000 nM and nPKC delta was translocated by 10-1,000 nM TPA. Both isoforms were maximally translocated by 100-1,000 nM TPA, whereas 1 nM did not translocate these two isoforms. When the cells were treated with 1,000 nM TPA for 5 min to 17 h, the translocation of these two isoforms occurred rapidly after 5-min treatment and could be sustained for 1 h, whereas down-regulation occurred after 3-h treatment and almost complete down-regulation was observed after 17-h treatment. However, the extent of down-regulation of nPKC delta was greater than that of cPKC alpha at 3-, 6-, and 10-h treatment. Further studies by using different doses of TPA (100, 10, 3, and 1 nM) and extending the time to 24 h showed that cPKC alpha was more resistant to down-regulation. This conventional isoform was maintained at a translocation state even after long-term treatment with 3-100 nM TPA, and complete down-regulation was only shown after 1,000 nM treatment.(ABSTRACT TRUNCATED AT 250 WORDS)