IGF binding protein-3 mediates stress-induced apoptosis in non-transformed mammary epithelial cells

Authors

  • Brian J. Leibowitz,

    1. Graduate Program in Endocrinology and Animal Biosciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey
    Current affiliation:
    1. University of Pittsburgh Cancer Institute, Hillman Cancer Center Research Pavilion, Suite 2.43, 5117 Centre Avenue, Pittsburgh, PA 15213.
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  • Allyson Agostini-Dreyer,

    1. Graduate Program in Nutritional Sciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey
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  • Amanda E. Jetzt,

    1. Department of Animal Sciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey
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  • Christopher S. Krumm,

    1. Department of Animal Sciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey
    Current affiliation:
    1. Department of Animal Science, Cornell University, 149 Morrison Hall, Ithaca, NY 14853.
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  • Wendie S. Cohick

    Corresponding author
    1. Graduate Program in Endocrinology and Animal Biosciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey
    2. Graduate Program in Nutritional Sciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey
    3. Department of Animal Sciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey
    • Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, NJ 08901-8520.
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  • Conflict of interest: none to declare.

  • Brian J. Leibowitz and Allyson Agostini-Dreyer contributed equally to this study.

Abstract

Mammary epithelial cell (MEC) number is an important determinant of milk production in lactating dairy cows. IGF-I increases IGF binding protein-3 (IGFBP-3) production in these cells, which plays a role in its ability to enhance proliferation. In the present study, we show that the apoptotic factor anisomycin (ANS) also increases IGFBP-3 mRNA and protein in a dose- and concentration-dependent manner that mirrors activation of caspase-3 and -7, with significant increases in both IGFBP-3 protein and caspase activation observed by 3 h. Knock-down of IGFBP-3 with small interfering (si) RNA attenuated the ability of ANS to induce apoptosis, while knock-down of IGFBP-2, the other major IGFBP made by bovine MEC, had no effect. Reducing IGFBP-3 also decreased the ability of ANS to induce mitochondrial cytochrome c release, indicating its involvement in the intrinsic apoptotic pathway. In contrast, transfection with IGFBP-3 in the absence of ANS failed to induce apoptosis. Since both the mitogen IGF-I and the apoptotic inducer ANS increase IGFBP-3 production in MEC, we proposed that cellular localization might determine IGFBP-3 action. While both IGF-I and ANS stimulated the release of IGFBP-3 into conditioned media, only ANS induced nuclear localization of IGFBP-3. A pan-caspase inhibitor had no effect on ANS-induced nuclear localization of IGFBP-3, indicating that nuclear entry of IGFBP-3 precedes caspase activation. Treatment with IGF-I had no effect on ANS-induced nuclear localization, but did block ANS-induced apoptosis. In summary, our data indicate that IGFBP-3 plays a role in stress-induced apoptosis that may require nuclear localization in non-transformed MEC. J. Cell. Physiol. 228: 734–742, 2013. © 2012 Wiley Periodicals, Inc.

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