Protein kinase C activation by 12-0-tetradecanoylphorbol 13-acetate in CG-4 line oligodendrocytes stimulates turnover of choline and ethanolamine phospholipids by phospholipase D and induces rapid process contraction

Treatment of [H-3]-choline- or [C-14]-ethanolamine-labelled undifferentiate d bipolar and differentiated multipolar CG-4 line oligodendrocytes with 12- O-tetradecanoylphorbol 13-acetate (TPA) to activate protein kinase C stimul ated the release of choline or ethanolamine metabolites to the medium over controls. Ro31-8220, a PKC inhibitor, reduced TPA-stimulated release of cho line- and ethanolamine-metabolites to basal levels. TPA treatment of both b ipolar and multipolar cells caused rapid contraction of processes leaving r ounded up cells: this effect was blocked by Ro31-8220. After 12-15 h exposu re to TPA, bipolar undifferentiated CG-4 line cells extended short processe s again and the cells became multipolar. Nocodozole, an agent which disrupt s microtubules and caused CG-4 line cells to round up, caused increased cho line or ethanolamine-metabolite release to the medium over basal levels sug gesting that some release during TPA-treatment might occur due to process f ragmentation. However, the transphosphatidylation reaction confirmed that p hospholipase D was active in these cells. Exposure of bipolar undifferentia ted CG-4 line cells to TPA resulted in down-regulatation of PKC-alpha and P KC-beta which could not be detected by Western blotting after a few hours; PKC-epsilon was down-regulated much more slowly but PKCs delta, zeta and io ta were not influenced by 48 h exposure of cells to TPA. Formation of phosp hatidylethanol in the transphosphatidylation reaction was markedly reduced in TPA down-regulated cells indicating a role for PKCs alpha and beta in ph ospholipase D activation in CG-4 line oligodendrocytes.