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Runx2 regulates G protein-coupled signaling pathways to control growth of osteoblast progenitors

Nadiya M Teplyuk1, Mario Galindo1, Viktor I Teplyuk2

  • 1Department of Cell Biology and Cancer Center, Worcester, Massachusetts 01655.

The Journal of Biological Chemistry
|July 16, 2008
PubMed

Insights

Runt-related transcription factor 2 (Runx2) controls osteoblast growth by regulating G protein-coupled receptor signaling. Runx2 activates Gpr30 and represses Rgs2, enhancing responsiveness to mitogenic signals.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Bone Biology

Background:

  • Runt-related transcription factor 2 (Runx2) is crucial for osteoblast differentiation and function.
  • Runx2 levels fluctuate during the osteoblast cell cycle, peaking in G1.
  • Runx2 acts as a subnuclear effector for multiple signaling pathways.

Purpose of the Study:

  • To investigate the specific functions and target genes of Runx2 that regulate osteoblast proliferation.
  • To determine the role of Runx2's signaling interactions and DNA-binding in growth control.
  • To elucidate how Runx2 influences G protein-coupled receptor signaling in osteoblasts.

Main Methods:

  • Forced expression of wild-type and mutant Runx2 in Runx2(-/-) osteoprogenitors.
  • Analysis of Runx2 mutants defective in protein binding, nuclear matrix interaction, DNA binding, or transcriptional regulation.
  • Affymetrix expression profiling to identify Runx2 target genes.
  • RNA interference and gene overexpression to study the function of Gpr30 and Rgs2.

Main Results:

  • Forced expression of wild-type Runx2 suppressed osteoblast growth, while mutants defective in DNA binding or C-terminal functions did not.
  • Runx2 regulates genes involved in G protein-coupled receptor signaling, including Gpr30 and Rgs2.
  • Runx2 activates Gpr30 expression and represses Rgs2 expression, impacting cAMP signaling.
  • Gpr30 knockdown or Rgs2 overexpression inhibited osteoblast proliferation.

Conclusions:

  • Runx2's growth regulatory functions are dependent on its DNA-binding and C-terminal activities.
  • Runx2 modulates osteoblast proliferation by influencing cAMP-related G protein-coupled receptor signaling.
  • Runx2 sensitizes osteoblasts to mitogenic signals by activating Gpr30 and repressing Rgs2.

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