The differential role of protein kinase C isozymes in the rapid induction of neurofilament phosphorylation by nerve growth factor and phorbol esters in PC12 cells.
We examined the short-term regulation of the phosphorylation of the mid-sized neurofilament subunit (NF-M) by kinases which were activated in rat pheochromocytoma (PC12) cells by nerve growth factor (NGF) and/or 12-O-tetradecanoylphorbol 13-acetate (TPA). We found that NGF and TPA, alone or in combination, increased (a) the incorporation of [32P]Pi into NF-M and (b) the rate of conversion of NF-M from a poorly phosphorylated to a more highly phosphorylated form. This was not due to increased synthesis of NF-M, because NGF alone did not increase NF-M synthesis and TPA alone or TPA and NGF together inhibited the synthesis of NF-M. Further, an increase in calcium/phospholipid-dependent kinase (PKC) activity resulting from the treatment of PC12 cells with NGF and TPA was observed concomitant with the increased phosphorylation of NF-M. This PKC activity was determined to be derived from the PKC alpha and PKC beta isozymes. Finally, when PC12 cells were rendered PKC-deficient by treatment with 1 muM TPA for 24 h, NGF maintained the ability to induce an increase in NF-M phosphorylation, though not to the level attained in cells which were not PKC-deficient. These data suggest that NGF with or without TPA stimulates NF-M phosphorylation as a result of a complex series of events which include PKC-independent and PKC-dependent pathways.
Clark
E A
EA
Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia 19104-4283.
Lee
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VM
D000310:Adrenal Gland Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D000818:Animals; D002478:Cells, Cultured; D015536:Down-Regulation / Q000502:physiology; D007382:Intermediate Filaments / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D007527:Isoenzymes / Q000378:metabolism / Q000502:physiology*; D009414:Nerve Growth Factors / Q000494:pharmacology*; D010673:Pheochromocytoma / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D010703:Phorbol Esters / Q000494:pharmacology*; D010710:Phosphates / Q000378:metabolism; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D013564:Sympathetic Nervous System / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure
D007527:Isoenzymes; D009414:Nerve Growth Factors; D010703:Phorbol Esters; D010710:Phosphates; D010761:Phosphorus Radioisotopes; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate