Phorbol ester stimulation of protein kinase C activity and ribosomal DNA transcription. Role in hypertrophic growth of cultured cardiomyocytes.
The mechanism by which phorbol esters induce hypertrophic growth of cardiomyocytes was investigated. Control and 4 alpha-phorbol 12,13-didecanoate-treated myocytes demonstrated a slow rate of growth as measured by the protein/DNA ratio and cell area. In contrast, treatment with phorbol 12-myristate 13-acetate (PMA) stimulated protein accumulation by 34%, while cell area was increased by 68% over control myocytes after 72 h. RNA content in PMA-treated myocytes was 33% higher than in control cells and 4 alpha-phorbol 12,13-didecanoate-treated cells after 72 h. Membrane-associated protein kinase C activity was transiently increased after PMA treatment but returned to normal by 48 h. Cytosolic protein kinase C activity was not significantly altered by PMA. Membrane-associated and cytosolic protein kinase C activities were not altered by 4 alpha-phorbol 12,13-didecanoate. Protein kinase C activity, RNA polymerase I activity, and the transcriptional rate of ribosomal DNA (rDNA) were increased in nuclei isolated from PMA-treated cells. However, consistent with a high rate of processing of pre-ribosomal RNA (pre-rRNA), the pool size of pre-rRNA relative to the 28 S rRNA was unaltered by PMA treatment. These data demonstrated that PMA-induced hypertrophic growth of cardiomyocytes was due to an increase in the capacity for protein synthesis (rRNA), and suggest that this results from protein kinase C mediated increase in the rate of transcription of rDNA.
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Sigfried and Janet Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania 17822.
McDermott
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PJ
Carl
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Morgan
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HE
D000818:Animals; D000831:Animals, Newborn; D002273:Carcinogens / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D004275:DNA, Ribosomal / Q000187:drug effects / Q000235:genetics*; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D009206:Myocardium / Q000166:cytology*; D010703:Phorbol Esters / Q000494:pharmacology*; D011493:Protein Kinase C / Q000378:metabolism*; D012322:RNA Precursors / Q000187:drug effects / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects*
D002273:Carcinogens; D004275:DNA, Ribosomal; D010703:Phorbol Esters; D012322:RNA Precursors; C008876:phorbol-12,13-didecanoate; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate