title: Synergistic effects between protein kinase C and cAMP on activator protein-1 activity and differentiation of PC-12 pheochromocytoma cells.
abstract: In rat pheochromocytoma cells (PC-12) cells, we have studied the effect of protein kinase C (PKC) and cAMP on the activity of the nuclear transcription factor activator protein-1 (AP-1) and on differentiation of the cells into sympathetic nerve-like phenotype. By using mobility gel-shift assays, we found that both PKC and cAMP activation led to an increase in the binding of AP-1 to its consensus nucleotide sequence (TRE). When the PKC and cAMP pathways were activated simultaneously, a clear-cut synergistic effect was seen on the binding of AP-1 to TRE. Both PKC and cAMP activation were furthermore able to increase the AP-1 transcriptional activity in PC-12 cells transiently transfected with TRE-expressing plasmids. In agreement with the mobility gel-shift results, simultaneous activation of PKC and cAMP synergistically increased the AP-1 transcriptional activity. We next analyzed the effect of PKC and cAMP stimulation on differentiation and proliferation of PC-12 cells. Whereas PKC activation had no effect on the morphology of PC-12 cells, elevation of the intracellular cAMP level resulted in a marked increase in the number of neurite-bearing cells. This effect was paralleled by a strong inhibition of PC-12 cell proliferation. Interestingly, when PKC and cAMP activation were combined, the differentiation was further pronounced and growth further inhibited. These results show that both PKC and cAMP increase the AP-1 activity in PC-12 cells, and that these effects are synergistic. Moreover, we show that cAMP induces differentiation and inhibits growth of PC-12 cells, and that PKC activation acts synergistically with cAMP on these effects. The possible role of AP-1 in PC-12 cell differentiation is discussed.
authors.forename: A
authors.initials: A
authors.lastname: Kvanta
authors.forename: B B
authors.initials: BB
authors.lastname: Fredholm
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D005576:Colforsin / Q000494:pharmacology*; D000242:Cyclic AMP / Q000502:physiology*; D004357:Drug Synergism; D009363:Neoplasm Proteins / Q000378:metabolism; D016501:Neurites / Q000187:drug effects; D016716:PC12 Cells / Q000187:drug effects* / Q000473:pathology; D010673:Pheochromocytoma / Q000473:pathology*; D011485:Protein Binding; D011493:Protein Kinase C / Q000502:physiology*; D051381:Rats; D012045:Regulatory Sequences, Nucleic Acid; D015398:Signal Transduction / Q000187:drug effects*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D018808:Transcription Factor AP-1 / Q000378:metabolism*
chemical_list: D009363:Neoplasm Proteins; D018808:Transcription Factor AP-1; D005576:Colforsin; D000242:Cyclic AMP; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate