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Sp proteins and Runx2 mediate regulation of matrix gla protein (MGP) expression by parathyroid hormone

Authors

  • Supaporn Suttamanatwong,

    1. Department of Diagnostic and Biological Sciences, University of Minnesota School of Dentistry, Minneapolis, Minnesota 55455
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  • Eric D. Jensen,

    1. Department of Diagnostic and Biological Sciences, University of Minnesota School of Dentistry, Minneapolis, Minnesota 55455
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  • Jody Schilling,

    1. Department of Developmental and Surgical Sciences, University of Minnesota School of Dentistry, Minneapolis, MN 55455
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  • Renny T. Franceschi,

    1. Periodontics and Oral Medicine, School of Dentistry, University of Michigan, Ann Arbor, Michigan 48109
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  • Ann E. Carlson,

    1. Department of Diagnostic and Biological Sciences, University of Minnesota School of Dentistry, Minneapolis, Minnesota 55455
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  • Kim C. Mansky,

    1. Department of Developmental and Surgical Sciences, University of Minnesota School of Dentistry, Minneapolis, MN 55455
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  • Rajaram Gopalakrishnan

    Corresponding author
    1. Department of Diagnostic and Biological Sciences, University of Minnesota School of Dentistry, Minneapolis, Minnesota 55455
    • Diagnostic and Biological Sciences, 16-108B Moos Tower, 515 Delaware St SE, University of Minnesota School of Dentistry, Minneapolis, MN 55455.
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  • Supaporn Suttamanatwong and Eric D. Jensen contributed equally to the work.

Abstract

As part of its catabolic action in bone, parathyroid hormone (PTH) inhibits extracellular matrix mineralization. We previously showed that PTH dose-dependently induces matrix gla protein (MGP) expression in osteoblasts and this induction is at least partially responsible for PTH-mediated inhibition of mineralization. Recently, we identified PKA and ERK/MAPK as the key signaling pathways involved in PTH regulation of MGP expression. The goal of this study was to further characterize the mechanism by which PTH stimulates expression of MGP. Deletion analysis of the murine Mgp gene promoter identified a PTH-responsive region between −173 bp and−49 bp. Using gel-mobility shift assays we found that Sp1/Sp3, and Runx2 bind to distinct sites within this region. Mutation of either the Sp or the Runx2 site reduced MGP induction by PTH, while mutation of both sites completely abolished PTH responsiveness. Overexpression of Runx2 or Sp1 activated the Mgp reporter, while Sp3 was a dose-dependent repressor of Sp1 and PTH-induced MGP expression. Collectively, these data show that PTH regulates MGP gene transcription in osteoblasts through altered activities of Sp and Runx2 transcription factors. J. Cell. Biochem. 107: 284–292, 2009. © 2009 Wiley-Liss, Inc.

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