CRM1 protein-mediated regulation of nuclear clusterin (nCLU), an ionizing radiation-stimulated, bax-dependent pro-death factor

Konstantin S. Leskov, Shinako Araki, John Paul Lavik, Jose A. Gomez, Vivian Gama, Efstathios S. Gonos, Ioannis P. Trougakos, Shigemi Matsuyama, David A. Boothman

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Abstract

Expression of the clusterin (CLU) gene results in the synthesis of a conventional secretory isoform set (pre- and mature secretory clusterin proteins, psCLU/sCLU), as well as another set of intracellular isoforms, appearing in the cytoplasm (pre-nuclear CLU, pnCLU) and in the nucleus as an ∼55-kDa mature nuclear clusterin (nCLU) form. These two isoform sets have opposing cell functions: pro-survival and pro-death, respectively. Although much is known about the regulation and function of sCLU as a pro-survival factor, the regulation and function of endogenous nCLU in cell death are relatively unexplored. Here, we show that depletion of endogenous nCLU protein using siRNA specific to its truncatedmRNAincreased clonogenic survival of ionizing radiation (IR)-exposed cells. nCLU-mediated apoptosis was Bax-dependent, and lethality correlated with accumulation of maturenCLUprotein.nCLUaccumulation was regulated by CRM1 because binding between CRM1 and nCLU proteins was significantly diminished by leptomycin B (LMB), and nuclear levels of nCLU protein were significantly enhanced by LMB and IR co-treatment. Moreover, LMB treatment significantly enhanced IR-induced nCLU-mediated cell death responses. Importantly, bax -/- and bax -/-/bak -/- double knock-out cells were resistant to nCLU-mediated cell death, whereas bak -/- or wild-type bax +/+/bak +/+ cells were hypersensitive. The regulation of nCLU by CRM1 nuclear export/import may explain recent clinical results showing that highly malignant tumors have lost the ability to accumulate nCLU levels, thereby avoiding growth inhibition and cell death.

Original languageEnglish (US)
Pages (from-to)40083-40090
Number of pages8
JournalJournal of Biological Chemistry
Volume286
Issue number46
DOIs
StatePublished - Nov 18 2011

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Leskov, K. S., Araki, S., Lavik, J. P., Gomez, J. A., Gama, V., Gonos, E. S., Trougakos, I. P., Matsuyama, S., & Boothman, D. A. (2011). CRM1 protein-mediated regulation of nuclear clusterin (nCLU), an ionizing radiation-stimulated, bax-dependent pro-death factor. Journal of Biological Chemistry, 286(46), 40083-40090. https://doi.org/10.1074/jbc.M111.252957