Reduced expression of the regulatory A subunit of serine/threonine protein phosphatase 2A in human breast cancer MCF-7 cells

  • Authors:
    • Katsuo Suzuki
    • Kazuhide Takahashi
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  • Published online on: November 1, 2003     https://doi.org/10.3892/ijo.23.5.1263
  • Pages: 1263-1268
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Abstract

The β1 subunit of integrin is serine/threonine phosphorylated in growth arrested human breast cancer MCF-7 cells, while it is not in quiescent normal human breast epithelial (HBE) cells. Using the affinity-purified antibodies PB788-9 against the synthetic oligopeptide that contained phosphothreonines corresponding to threonines 788 and 789 on β1 integrin, β1 integrin in MCF-7 cells, but not in HBE cells, was found to react with PB788-9. The β1 integrin immunoprecipitates from HBE cells co-immunoprecipitated the core enzyme of serine/threonine protein phosphatase (PP) 2A, consisting of the regulatory A (PP2A-A) and the catalytic C (PP2A-C) subunits, with the protein phosphatase activity susceptible to okadaic acid (OA), an inhibitor of PP2A and PP1, but not to a PP1 inhibitor. In contrast, β1 integrin from MCF-7 cells co-immunoprecipitated PP2A-C, but not PP2A-A, with no protein phosphatase activity. Immunoblotting of whole cell lysates revealed that a comparable amount of PP2A-C was present in either HBE or MCF-7 cells, but the amount of PP2A-A was significantly reduced in MCF-7 cells compared to that in HBE cells. The results suggest that the failure of β1 integrin dephosphorylation at threonines 788 and 789 may be due to a significant reduction in the PP2A-A expression in MCF-7 cells.

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November 2003
Volume 23 Issue 5

Print ISSN: 1019-6439
Online ISSN:1791-2423

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Spandidos Publications style
Suzuki K and Suzuki K: Reduced expression of the regulatory A subunit of serine/threonine protein phosphatase 2A in human breast cancer MCF-7 cells. Int J Oncol 23: 1263-1268, 2003
APA
Suzuki, K., & Suzuki, K. (2003). Reduced expression of the regulatory A subunit of serine/threonine protein phosphatase 2A in human breast cancer MCF-7 cells. International Journal of Oncology, 23, 1263-1268. https://doi.org/10.3892/ijo.23.5.1263
MLA
Suzuki, K., Takahashi, K."Reduced expression of the regulatory A subunit of serine/threonine protein phosphatase 2A in human breast cancer MCF-7 cells". International Journal of Oncology 23.5 (2003): 1263-1268.
Chicago
Suzuki, K., Takahashi, K."Reduced expression of the regulatory A subunit of serine/threonine protein phosphatase 2A in human breast cancer MCF-7 cells". International Journal of Oncology 23, no. 5 (2003): 1263-1268. https://doi.org/10.3892/ijo.23.5.1263