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    Ser70 phosphorylation of Bcl-2 by selective tyrosine nitration of PP2A-B56 d stabilizes its antiapoptotic activity

    Access Status
    Open access via publisher
    Authors
    Low, I.
    Loh, T.
    Huang, Y.
    Virshup, D.
    Pervaiz, Shazib
    Date
    2014
    Type
    Journal Article
    
    Metadata
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    Citation
    Low, I. and Loh, T. and Huang, Y. and Virshup, D. and Pervaiz, S. 2014. Ser70 phosphorylation of Bcl-2 by selective tyrosine nitration of PP2A-B56 d stabilizes its antiapoptotic activity. Blood. 124 (14): pp. 2223-2234.
    Source Title
    Blood
    DOI
    10.1182/blood-2014-03-563296
    ISSN
    0006-4971
    School
    School of Biomedical Sciences
    URI
    http://hdl.handle.net/20.500.11937/51027
    Collection
    • Curtin Research Publications
    Abstract

    Bcl-2 is frequently overexpressed in hematopoietic malignancies, and selective phosphorylation at ser70 enhances its antiapoptotic activity. Phospho-ser70 is dephosphorylated by specific heterotrimers of protein phosphatase 2A (PP2A). We report here that a mild pro-oxidant intracellular milieu induced by either pharmacological inhibition or geneticknockdownof superoxide dismutase 1 (SOD1) inhibits the functional holoenzyme assembly of PP2A and prevents Bcl-2 ser70 dephosphorylation. This redox-dependent regulation of Bcl-2 phosphorylation is due to nitrosative modification of B56d, which we identify as the regulatory subunit mediating PP2A-dependent Bcl-2 dephosphorylation. Redox inhibition of PP2A results from peroxynitrite-mediated nitration of a conserved tyrosine residue within B56d (B56dY289). Although nitrated B56dY289 binds efficiently to ser70-phosphorylated Bcl-2, this specific modification inhibits the recruitment of the PP2Acatalytic core (A andCsubunits). Furthermore, inhibitionofB56dY289 nitration restores PP2A holoenzyme assembly, thereby permitting S70 dephosphorylation of Bcl-2 and inhibiting its antiapoptotic activity. More important, in primary cells derived from clinical lymphomas, Bcl-2 phosphorylation at S70 directly correlates with B56d nitration and repression of SOD1, but inversely correlates with B56d interaction with the PP2A-C catalytic subunit. These data underscore the role of a pro-oxidant milieu in chemoresistance of hematopoietic and other cancers via selective targeting of tumor suppressors such as PP2A. (Blood. 2014;124(14):2223-2234).

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