Interaction of protein phosphatase 1 delta with nucleolin in human osteoblastic cells.
We examined the expression and cytolocalization of the protein phosphatase type 1 delta (PP1delta) isoform and nucleolin in human osteoblastic MG63 and Saos-2 cells. Cellular fractionation of MG63 cells was done and protein was prepared from each fraction. Anti-nucleolin antibody interacted with the 100- and 95-kD proteins present in the whole-cell lysate. The 100-kD protein was detected in nuclear and nucleolar fractions. The 95-kD protein was detected in cytosolic and nucleoplasmic fractions. PP1delta and nucleolin were co-localized in the nucleolus in MG63 and Saos-2 cells revealed by an immunofluorescence method. PP1delta and nucleolin were also co-immunoprecipitated with anti-nucleolin and anti-PP1delta antibodies. In the actinomycin D-treated cells, the subcellular localization of PP1delta and nucleolin was changed. Expression of PP1delta was upregulated with actinomycin D treatment. The level of 100-kD protein did not change in the actinomycin D-treated cells. However, the level of the 95-kD band increased with actinomycin D treatment. These results indicate that PP1delta was associated with nucleolin in the nucleolus of MG63 and Saos-2 cells and that nucleolin is a possible candidate substrate for PP1delta.
Department of Histology and Oral Histology, School of Dentistry, The University of Tokushima, Tokushima, Japan.
Hiroyuki
H
Morimoto
Hirohiko
H
Okamura
Tatsuji
T
Haneji
D002460:Cell Line; D003609:Dactinomycin / Q000494:pharmacology; D006801:Humans; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism*; D010006:Osteoblasts / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D011233:Precipitin Tests; D054645:Protein Phosphatase 1; D016601:RNA-Binding Proteins / Q000378:metabolism*; D000097796:Nucleolin
D003609:Dactinomycin; D007527:Isoenzymes; D009687:Nuclear Proteins; D010749:Phosphoprotein Phosphatases; D010750:Phosphoproteins; D054645:Protein Phosphatase 1; D016601:RNA-Binding Proteins; D000097796:Nucleolin