title: Involvement of p21(Waf1/Cip1) in protein kinase C alpha-induced cell cycle progression.
abstract: Protein kinase C (PKC) plays an important role in the regulation of glioma growth; however, the identity of the specific isoform and mechanism by which PKC fulfills this function remain unknown. In this study, we demonstrate that PKC activation in glioma cells increased their progression through the cell cycle. Of the six PKC isoforms that were present in glioma cells, PKC alpha was both necessary and sufficient to promote cell cycle progression when stimulated with phorbol 12-myristate 13-acetate. Also, decreased PKC alpha expression resulted in a marked decrease in cell proliferation. The only cell cycle-regulatory molecule whose expression was rapidly altered and increased by PKC alpha activity was the cyclin-cyclin-dependent kinase (CDK) inhibitor p21(Waf1/Cip1). Coimmunoprecipitation studies revealed that p21(Waf1/Cip1) upregulation was accompanied by an incorporation of p21(Waf1/Cip1) into various cyclin-CDK complexes and that the kinase activity of these complexes was increased, thus resulting in cell cycle progression. Furthermore, depletion of p21(Waf1/Cip1) by antisense strategy attenuated the PKC-induced cell cycle progression. These results suggest that PKC alpha activity controls glioma cell cycle progression through the upregulation of p21(Waf1/Cip1), which facilitates active cyclin-CDK complex formation.
authors.affiliation: Departments of Oncology and Clinical Neurosciences, University of Calgary, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Besson
authors.forename: V W
authors.initials: VW
authors.lastname: Yong
mesh_terms: D002453:Cell Cycle / Q000502:physiology*; D002455:Cell Division; D016543:Central Nervous System Neoplasms / Q000378:metabolism / Q000473:pathology; D019925:Cyclin A / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism; D019938:Cyclin D1 / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D005910:Glioma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D016376:Oligonucleotides, Antisense; D010703:Phorbol Esters / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D051745:Protein Kinase C-delta; D051744:Protein Kinase C-epsilon; D000074121:Protein Kinase C-theta; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
chemical_list: C493956:CDKN1A protein, human; D019925:Cyclin A; D019926:Cyclin B; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D007527:Isoenzymes; D016376:Oligonucleotides, Antisense; D010703:Phorbol Esters; D019938:Cyclin D1; C080287:thymeleatoxin; C497258:PRKCD protein, human; C497255:PRKCE protein, human; C076233:PRKCQ protein, human; D011493:Protein Kinase C; D051745:Protein Kinase C-delta; D051744:Protein Kinase C-epsilon; D000074121:Protein Kinase C-theta; D018844:Cyclin-Dependent Kinases; D013755:Tetradecanoylphorbol Acetate