title: Okadaic acid induces phosphorylation of p65NF-kappaB on serine 536 and activates NF-kappaB transcriptional activity in human osteoblastic MG63 cells.
abstract: Nuclear factor-kappa B (NF-kappaB) is an essential transcription factor in the control of expression of genes involved in cell growth, differentiation, inflammation, and neoplastic transformation. Previously, we reported that okadaic acid (OA), which is a specific inhibitor of serine/threonine protein phosphatases, induced apoptosis in cells of human osteosarcoma cell line MG63. However, to date, it is not clear whether the phosphorylation status of NF-kappaB could be affected by the treatment with OA. In this report, we demonstrate that treatment of MG63 cells with OA enhanced the phosphorylation level of NF-kappaB, as judged from the results of Western blot analysis and a lambda protein phosphatase dephosphorylation assay. The phosphorylation level of NF-kappaB was enhanced in both time- and dose-dependent manners. In the cells treated with 100 nM OA for 3 h, consequential translocation of NF-kappaB from the cytosol to the nucleus occurred. Western blotting experiments with an anti-phospho-p65NF-kappaB antibody disclosed that the NF-kappaB was phosphorylated on serine 536. Furthermore, OA stimulated the transcriptional activity of NF-kappaB in MG63 cells, as judged from the results of a luciferase assay. Our findings indicate that OA elicit phosphorylation of NF-kappaB on serine 536 in MG63 cells, resulting in the translocation of phospho-NF-kappaB to the nucleus, thereby promoting transcriptional activity of genes.
authors.affiliation: Department of Histology and Oral Histology, Institute of Health Biosciences, The University of Tokushima Graduate School, Kuramoto, Tokushima 770-8504, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Ozaki
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Morimoto
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Tanaka
authors.forename: Hirohiko
authors.initials: H
authors.lastname: Okamura
authors.forename: Kaya
authors.initials: K
authors.lastname: Yoshida
authors.forename: Bruna Rabelo
authors.initials: BR
authors.lastname: Amorim
authors.forename: Tatsuji
authors.initials: T
authors.lastname: Haneji
mesh_terms: D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D019319:Okadaic Acid / Q000494:pharmacology*; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D012694:Serine / Q000378:metabolism*; D051996:Transcription Factor RelA / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D004791:Enzyme Inhibitors; D051996:Transcription Factor RelA; D019319:Okadaic Acid; D012694:Serine