Identification and characterization of anti-osteoclastogenic peptides derived from the cytoplasmic tail of receptor activator of nuclear factor kappa B

J Bone Miner Metab. 2012 Sep;30(5):543-53. doi: 10.1007/s00774-012-0353-5. Epub 2012 Apr 28.

Abstract

Pathological bone resorption by osteoclasts is primarily treated with bisphosphonates. Because the administration of bisphosphonates is associated with a risk for multiple adverse symptoms, a precise understanding of the mechanisms underlying osteoclastogenesis is required to develop drugs with minimal side-effects. Osteoclastogenesis depends on receptor activator of nuclear factor kappa B (RANK) signaling mediated by TRAF6. We previously identified a highly conserved domain in the cytoplasmic tail of RANK (HCR), which did not share any significant homology with other proteins and was essential for osteoclastogenesis. HCR acts as a platform for the formation of Gab2- and Vav3-containing signal complexes, and ectopic expression of the HCR peptide inhibits osteoclastogenesis. Here, we uncover the mechanisms of HCR peptide-mediated inhibition of osteoclastogenesis. Expression of either the amino- or carboxyl-terminal half of the HCR peptide (N- or C-peptide) independently inhibited RANK signaling prior to cell-cell fusion. In contrast, expression of the GY-peptide, which is a part of the C-peptide, did not significantly affect prefusion RANK signaling, but did inhibit cell-cell fusion to prevent formation of multinucleated mature osteoclasts. Moreover, Gab2, which is involved in RANK signaling by binding TRAF6, bound the C-peptide but not the N-peptide, suggesting that the C- and the N-peptides sequester TRAF6 in a Gab2-dependent and Gab2-independent manner, respectively. In contrast, the GY-peptide did not bind Gab2 but could bind Vav3, which mediates signaling for cell-cell fusion. Collectively, we propose that the HCR peptide inhibits osteoclastogenesis through two modes of action-inhibition of (1) prefusion RANK signaling and (2) cell-cell fusion by blocking TRAF6- and Vav3-mediated signaling, respectively.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Amino Acid Sequence
  • Animals
  • Bone Marrow Cells / metabolism
  • C-Peptide / genetics
  • C-Peptide / metabolism
  • Cell Fusion
  • Cytoplasm / genetics
  • Cytoplasm / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Molecular Sequence Data
  • Osteoclasts / metabolism*
  • Peptides / genetics
  • Peptides / metabolism*
  • Phosphoproteins / genetics
  • Phosphoproteins / metabolism
  • Protein Binding / genetics
  • Protein Structure, Tertiary / genetics
  • Proto-Oncogene Proteins c-vav / genetics
  • Proto-Oncogene Proteins c-vav / metabolism
  • Receptor Activator of Nuclear Factor-kappa B / genetics
  • Receptor Activator of Nuclear Factor-kappa B / metabolism*
  • Signal Transduction / genetics
  • TNF Receptor-Associated Factor 6 / genetics
  • TNF Receptor-Associated Factor 6 / metabolism

Substances

  • Adaptor Proteins, Signal Transducing
  • C-Peptide
  • Gab2 protein, mouse
  • Peptides
  • Phosphoproteins
  • Proto-Oncogene Proteins c-vav
  • Receptor Activator of Nuclear Factor-kappa B
  • TNF Receptor-Associated Factor 6
  • Tnfrsf11a protein, mouse
  • Vav3 protein, mouse