title: Involvement of nPKC-MAPK pathway in the decrease of nucleophosmin/B23 during megakaryocytic differentiation of human myelogenous leukemia K562 cells.
abstract: Human myelogenous leukemia K562 cells were induced to undergo megakaryocytic differentiation by long-term treatment with phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA). The protein level of nucleophosmin/B23 (NPM/B23), a nucleolar protein, was substantially decreased upon TPA treatment. In this study, we found that the proteasome inhibitors blocked the decrease of NPM/B23 protein in response to TPA, suggesting the proteasomes were involved in the downregulation of NPM/B23 upon megakaryocytic differentiation. To investigate the signaling pathway in the downregulation of NPM/B23 during early TPA-induced megakaryocytic differentiation of K562 cells, K562 cells were treated with TPA in the presence of the PKC isozyme-selective inhibitors, GF109203X and Gö 6976, or MEK1 inhibitor, PD98059. The decrease of NPM/B23 protein in the TPA-treated K562 cells was blocked by GF109203X but not by Gö 6976, suggesting the involvement of novel PKCs in the downregulation of NPM/B23 during TPA-induced megakaryocytic differentiation of K562 cells. The application of MEK1 inhibitor PD98059 upon TPA treatment blocked the TPA-induced decrease of NPM/B23 protein and aborted the megakaryocytic differentiation but not to break through the cell growth arrest. Unlike NPM/B23, the degradation of nucleolin in the TPA-treated K562 cells could not be blocked by PD98059 while the TPA-induced megakaryocytic differentiation was abrogated. The decrease of NPM/B23 protein seems to be more correlated with the novel PKC-MAPK-induced megakaryocytic differentiation than another nucleolar protein, nucleolin. Taken together, our results indicated that novel PKC-MAPK pathway was required for the decrease of NPM/B23 during TPA-induced megakaryocytic differentiation.
authors: Department and Graduate School of Biotechnology, Fooyin University, 151 Chin-Hsueh, Rd., Ta-Liao Hsiang, Kaohsiung Hsien, 831 Taiwan, ROC.
authors: Chih-Chung
authors: CC
authors: Chou
authors: Benjamin Yat-Ming
authors: BY
authors: Yung
authors: Chen-Ya
authors: CY
authors: Hsu
mesh_terms: D002227:Carbazoles / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects*; D045744:Cell Line, Tumor; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D020014:K562 Cells / Q000166:cytology* / Q000378:metabolism; D007951:Leukemia, Myeloid / Q000201:enzymology / Q000473:pathology; D008301:Maleimides / Q000494:pharmacology; D008533:Megakaryocytes / Q000166:cytology* / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D000090243:Nucleophosmin; D010750:Phosphoproteins / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D000097796:Nucleolin
chemical_list: D002227:Carbazoles; D007211:Indoles; D008301:Maleimides; D020928:Mitogen-Activated Protein Kinases; D009687:Nuclear Proteins; D000090243:Nucleophosmin; D010750:Phosphoproteins; D046988:Proteasome Endopeptidase Complex; D061988:Proteasome Inhibitors; D011493:Protein Kinase C; D016601:RNA-Binding Proteins; D013755:Tetradecanoylphorbol Acetate; D000097796:Nucleolin; C000716967:NPM1 protein, human; C081021:Go 6976; C070515:bisindolylmaleimide I