title: Posttranscriptional regulation of GAP-43 gene expression in PC12 cells through protein kinase C-dependent stabilization of the mRNA.
abstract: We have previously shown that nerve growth factor (NGF) selectively stabilizes the GAP-43 mRNA in PC12 cells. To study the cellular mechanisms for this post-transcriptional control and to determine the contribution of mRNA stability to GAP-43 gene expression, we examined the effects of several agents that affect PC12 cell differentiation on the level of induction and rate of degradation of the GAP-43 mRNA. The NGF-mediated increase in GAP-43 mRNA levels and neurite outgrowth was mimicked by the phorbol ester TPA, but not by dibutyryl cAMP or the calcium ionophore A12783. Downregulation of protein kinase C (PKC) by high doses of phorbol esters or selective PKC inhibitors prevented the induction of this mRNA by NGF, suggesting that NGF and TPA act through a common PKC-dependent pathway. In mRNA decay studies, phorbol esters caused a selective 6-fold increase in the half-life of the GAP-43 mRNA, which accounts for most of the induction of this mRNA by TPA. The phorbol ester-induced stabilization of GAP-43 mRNA was blocked by the protein kinase inhibitor polymyxin B and was partially inhibited by dexamethasone, an agent that blocks GAP-43 expression and neuronal differentiation in PC12 cells. In contrast, the rates of degradation and the levels of the GAP-43 mRNA in control and TPA-treated cells were not affected by cycloheximide treatment. Thus, changes in GAP-43 mRNA turnover do not appear to require continuous protein synthesis. In conclusion, these data suggest that PKC activity regulates the levels of the GAP-43 mRNA in PC12 cells through a novel, translation-independent mRNA stabilization mechanism.
authors.affiliation: Department of Biochemistry, University of New Mexico School of Medicine, Albuquerque 87131-5221.
authors.forename: N I
authors.initials: NI
authors.lastname: Perrone-Bizzozero
authors.forename: V V
authors.initials: VV
authors.lastname: Cansino
authors.forename: D T
authors.initials: DT
authors.lastname: Kohn
mesh_terms: D000818:Animals; D003907:Dexamethasone / Q000494:pharmacology; D004789:Enzyme Activation; D019922:GAP-43 Protein; D005786:Gene Expression Regulation / Q000187:drug effects*; D006133:Growth Substances / Q000502:physiology; D066298:In Vitro Techniques; D008562:Membrane Glycoproteins / Q000235:genetics*; D009419:Nerve Tissue Proteins / Q000235:genetics*; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D016716:PC12 Cells; D010750:Phosphoproteins / Q000378:metabolism; D011112:Polymyxin B / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D019922:GAP-43 Protein; D006133:Growth Substances; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; D003907:Dexamethasone; D011493:Protein Kinase C; D011112:Polymyxin B; D013755:Tetradecanoylphorbol Acetate