Τίτλος:
CRM1 protein-mediated regulation of nuclear clusterin (nCLU), an ionizing radiation-stimulated, bax-dependent pro-death factor
Γλώσσες Τεκμηρίου:
Αγγλικά
Περίληψη:
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. © 2011 by The American Society for Biochemistry and Molecular Biology, Inc.
Συγγραφείς:
Leskov, K.S.
Araki, S.
Lavik, J.-P.
Gomez, J.A.
Gama, V.
Gonos, E.S.
Trougakos, I.P.
Matsuyama, S.
Boothman, D.A.
Περιοδικό:
Journal of Biological Chemistry
Λέξεις-κλειδιά:
Cell functions; Clonogenic survival; Clusterin; Growth inhibition; Isoforms; Knock outs; Leptomycin; Malignant tumors; Nuclear export; Nuclear levels; Wild types, Biosynthesis; Cell death; Gene expression; Glycoproteins; Ionizing radiation; Proteins; Radiation shielding, Gene expression regulation, clusterin; exportin 1; leptomycin B; messenger RNA; nuclear clusterin; protein Bax; small interfering RNA; unclassified drug, apoptosis; article; carboxy terminal sequence; cell strain MCF 7; cell survival; controlled study; human; human cell; ionizing radiation; osteosarcoma cell; priority journal; protein binding; protein depletion; radiation exposure; regulatory mechanism; wild type, Active Transport, Cell Nucleus; Animals; Antibiotics, Antineoplastic; Apoptosis; bcl-2 Homologous Antagonist-Killer Protein; bcl-2-Associated X Protein; Cell Nucleus; Clusterin; Fatty Acids, Unsaturated; Gamma Rays; Humans; Karyopherins; Mice; Mice, Knockout; Protein Isoforms; Radiation Tolerance; Receptors, Cytoplasmic and Nuclear
DOI:
10.1074/jbc.M111.252957
