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Okadaic acid induces phosphorylation of p65NF‐κB on serine 536 and activates NF‐κB transcriptional activity in human osteoblastic MG63 cells
Author(s) -
Ozaki Akiko,
Morimoto Hiroyuki,
Tanaka Hiroaki,
Okamura Hirohiko,
Yoshida Kaya,
Amorim Bruna Rabelo,
Haneji Tatsuji
Publication year - 2006
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.20873
Subject(s) - okadaic acid , phosphorylation , serine , microbiology and biotechnology , chemistry , nf κb , signal transduction , phosphatase , biology
Nuclear factor‐kappa B (NF‐κB) 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‐κB 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‐κB, as judged from the results of Western blot analysis and a λ protein phosphatase dephosphorylation assay. The phosphorylation level of NF‐κB was enhanced in both time‐ and dose‐dependent manners. In the cells treated with 100 nM OA for 3 h, consequential translocation of NF‐κB from the cytosol to the nucleus occurred. Western blotting experiments with an anti‐phospho‐p65NF‐κB antibody disclosed that the NF‐κB was phosphorylated on serine 536. Furthermore, OA stimulated the transcriptional activity of NF‐κB in MG63 cells, as judged from the results of a luciferase assay. Our findings indicate that OA elicit phosphorylation of NF‐κB on serine 536 in MG63 cells, resulting in the translocation of phospho‐NF‐κB to the nucleus, thereby promoting transcriptional activity of genes. J. Cell. Biochem. 99: 1275–1284, 2006. © 2006 Wiley‐Liss, Inc.