title: Activation of Polo-like kinase 3 by hypoxic stresses.
abstract: Hypoxia/reoxygenation stress induces the activation of specific signaling proteins and activator protein 1 (AP-1) to regulate cell cycle regression and apoptosis. In the present study, we report that hypoxia/reoxygenation stress activates AP-1 by increasing c-Jun phosphorylation and DNA binding activity through activation of Polo-like-kinase 3 (Plk3) resulting in apoptosis. The specific effect of hypoxia/reoxygenation stress on Plk3 activation resulting in c-Jun phosphorylation was the opposite of UV irradiation-induced responses that are meanly independent on activation of the stress-induced JNK signaling pathway in human corneal epithelial (HCE) cells. The effect of hypoxia/reoxygenation stress-induced Plk3 activation on increased c-Jun phosphorylation and apoptosis was also mimicked by exposure of cells to CoCl(2). Hypoxia/reoxygenation activated Plk3 in HCE cells to directly phosphorylate c-Jun proteins at phosphorylation sites Ser-63 and Ser-73, and to increase DNA binding activity of c-Jun, detected by EMSA. Further evidence demonstrated that Plk3 and phospho-c-Jun were immunocolocalized in the nuclear compartment of hypoxia/reoxygenation stress-induced cells. Increased Plk3 activity by overexpression of wild-type and dominantly positive Plk3 enhanced the effect of hypoxia/reoxygenation on c-Jun phosphorylation and cell death. In contrast, knocking-down Plk3 mRNA suppressed hypoxia-induced c-Jun phosphorylation. Our results provide a new mechanism indicating that hypoxia/reoxygenation induces Plk3 activation instead of the JNK effect to directly phosphorylate and activate c-Jun, subsequently contributing to apoptosis in HCE cells.
authors.affiliation: Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Torrance, California 90502, USA.
authors.forename: Ling
authors.initials: L
authors.lastname: Wang
authors.forename: Jie
authors.initials: J
authors.lastname: Gao
authors.forename: Wei
authors.initials: W
authors.lastname: Dai
authors.forename: Luo
authors.initials: L
authors.lastname: Lu
mesh_terms: D001692:Biological Transport; D003315:Cornea / Q000378:metabolism*; D004705:Endocytosis; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D000860:Hypoxia; D007700:Kinetics; D008954:Models, Biological; D009496:Neurotensin / Q000737:chemistry; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism*; D015398:Signal Transduction; D025521:Tumor Suppressor Proteins; D000097868:Polo-like Kinases
chemical_list: D009496:Neurotensin; D017346:Protein Serine-Threonine Kinases; D016755:Proto-Oncogene Proteins c-jun; D025521:Tumor Suppressor Proteins; C486256:PLK3 protein, human; D000097868:Polo-like Kinases