Protein kinase C-alpha but not protein kinase C-epsilon is differentially down-regulated by bryostatin 1 and tetradecanoyl phorbol 13-acetate in SH-SY5Y human neuroblastoma cells.
SH-SY5Y human neuroblastoma cells can be induced to differentiate by phorbol esters but not by bryostatins although both agents increase protein kinase C (PKC) activity in these cells to a similar extent. We examined whether this difference could be explained by differences in the responses of specific PKC isoenzymes. Both TPA and bryostatin 1 at 10 nM induced a rapid increase in membrane-associated PKC-alpha immunoreactivity which was sustained for 72 hours in TPA-treated cells, but was down-regulated within 24 hours in bryostatin-treated cells. TPA likewise induced a sustained phosphorylation of an 80 kDa PKC substrate whereas in bryostatin-treated cells the 80 kDa substrate was rapidly phosphorylated reaching a maximum at 6 hours followed by a decline to basal level within 48 hours. A higher concentration of TPA (300 nM), which results in a less differentiated phenotype, induced down-regulation of PKC-alpha within 24 hours. In contrast, both TPA and bryostatin 1 stimulated translocation and a partial down-regulation of PKC-epsilon with similar kinetics. These results suggest that the divergent actions of bryostatin 1 and TPA in SH-SY5Y cells are at least partially due to differential modulation of PKC-alpha but not PKC-epsilon by these two agents.
Jalava
A
A
Department of Biochemistry and Pharmacy, Abo Akademi University, Turku, Finland.
Lintunen
M
M
Heikkilä
J
J
D001692:Biological Transport; D054713:Bryostatins; D002454:Cell Differentiation / Q000187:drug effects; D003600:Cytosol / Q000201:enzymology; D015536:Down-Regulation; D004789:Enzyme Activation; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D007783:Lactones / Q000494:pharmacology*; D018942:Macrolides; D009447:Neuroblastoma; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D013379:Substrate Specificity; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D054713:Bryostatins; D007527:Isoenzymes; D007783:Lactones; D018942:Macrolides; C046785:bryostatin 1; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate