Structural and functional insights into sclerostin-glycosaminoglycan interactions in bone

Biomaterials. 2015 Oct;67:335-45. doi: 10.1016/j.biomaterials.2015.07.021. Epub 2015 Jul 15.

Abstract

In order to improve bone defect regeneration, the development of new adaptive biomaterials and their functional and biological validation is warranted. Glycosaminoglycans (GAGs) are important extracellular matrix (ECM) components in bone and may display osteogenic properties that are potentially useful for biomaterial coatings. Using hyaluronan (HA), chondroitin sulfate (CS) and chemically modified highly sulfated HA and CS derivatives (sHA3 and sCS3; degree of sulfation ∼3), we evaluated how GAG sulfation modulates Wnt signaling, a major regulator of osteoblast, osteoclast and osteocyte biology. GAGs were tested for their capability to bind to sclerostin, an inhibitor of Wnt signaling, using surface plasmon resonance and molecular modeling to characterize their interactions. GAGs bound sclerostin in a concentration- and sulfate-dependent manner at a common binding region. These findings were confirmed in an LRP5/sclerostin interaction study and an in vitro model of Wnt activation. Here, pre-incubation of sclerostin with different GAGs led to a sulfate- and dose-dependent loss of its bioactivity. Using GAG-biotin derivatives in a competitive ELISA approach sclerostin was shown to be the preferred binding partner over Wnt3a. In conclusion, highly sulfated GAGs might control bone homeostasis via interference with sclerostin/LRP5/6 complex formation. Whether these properties can be utilized to improve bone regeneration needs to be validated in vivo.

Keywords: Chondroitin sulfate (CS); Hyaluronic acid/hyaluronan (HA) sulfate; Low-density lipoprotein receptor-related protein 5/6 (LRP5/6); Molecular docking; Sclerostin; Surface plasmon resonance (SPR).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Animals
  • Bone Morphogenetic Proteins / chemistry*
  • Bone Morphogenetic Proteins / metabolism*
  • Bone and Bones / metabolism*
  • Cell Line
  • Genetic Markers
  • Glycosaminoglycans / chemistry*
  • Glycosaminoglycans / metabolism*
  • Humans
  • Hyaluronic Acid / metabolism
  • Low Density Lipoprotein Receptor-Related Protein-5 / metabolism
  • Low Density Lipoprotein Receptor-Related Protein-6 / metabolism
  • Models, Biological
  • Molecular Docking Simulation
  • Molecular Dynamics Simulation
  • Promoter Regions, Genetic / genetics
  • Protein Binding
  • Rats
  • Signal Transduction
  • Sulfates / metabolism
  • Sus scrofa
  • Thermodynamics
  • Wnt Proteins / genetics

Substances

  • Adaptor Proteins, Signal Transducing
  • Bone Morphogenetic Proteins
  • Genetic Markers
  • Glycosaminoglycans
  • Low Density Lipoprotein Receptor-Related Protein-5
  • Low Density Lipoprotein Receptor-Related Protein-6
  • SOST protein, human
  • Sulfates
  • Wnt Proteins
  • Hyaluronic Acid