Alterations in Type-1 Serine/Threonine Protein Phosphatase PP1aaa in Response to B-Cell Receptor Stimulation
| Autor: | Naoyuki Inagaki, Shu-ichi Matsuzawa, Norio Takizawa, Kunimi Kikuchi, Yusuke Mizuno, Masaki Inagaki, Masakazu Komatsu, Takeshi Kawamura |
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| Rok vydání: | 1997 |
| Předmět: |
Blotting
Western Molecular Sequence Data Phosphatase Down-Regulation Receptors Antigen B-Cell AKT2 macromolecular substances Biochemistry Catalysis Substrate Specificity Serine Phosphoprotein Phosphatases Electrophoresis Gel Two-Dimensional Amino Acid Sequence Phosphorylation Molecular Biology Protein Kinase C Protein kinase C Serine/threonine-specific protein kinase B-Lymphocytes Chemistry Protein phosphatase 1 General Medicine Protein phosphatase 2 Molecular biology Immunoglobulin M Tetradecanoylphorbol Acetate Subcellular Fractions |
| Zdroj: | Journal of Biochemistry. 122:730-737 |
| ISSN: | 0021-924X |
| Popis: | In response to stimulation of B-cells through cell surface IgM, the activity of the serine/threonine protein phosphatase PP1, but not PP2A, was transiently decreased and reached a minimum 10-20 min after the stimulation. The decrease was more profound in the immature B-cell line WEHI-231, than in the mature B-cell line BAL-17. Under these conditions, PP1alpha, an isoform of PP1, showed unique alterations in the patterns of several spots with distinct isoelectic points in the Western blot after two-dimensional electrophoresis, whereas another isoform, PP1delta, did not show any alteration. PP1gamma1 and PP1gamma2 were not detected in B-cells. Similar alterations in these spots were observed in B-cells stimulated by PMA. When partially purified PP1 consisting of PP1alpha and PP1delta was incubated with [gamma-32P]ATP and PKC, radioactive spots of PP1alpha could be detected, but no spot of PP1delta was detected. Because differences in sequence among PP1 isoforms are mostly restricted to their C-terminals, phosphorylation rates of the C-terminal peptides containing the PKC-phosphorylation motif were compared. The C-terminal peptide of PP1alpha is a better substrate for PKC than those of PP1gamma1 and PP1gamma2, and is phosphorylated at the serine residue corresponding to Ser-325 of PP1alpha. The corresponding C-terminal region of PP1delta does not contain the phosphorylation site. On the other hand, there was a large difference in subcellular distribution of PP1delta, but not PP1alpha, between immature and mature B-cells. From these results, it was strongly suggested that PP1alpha is involved, via phosphorylation by PKC, in the regulation of signal transduction in response to the stimulation of B-cells through cell surface IgM. |
| Databáze: | OpenAIRE |
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