The matricellular protein CYR61 inhibits osteoclastogenesis by a mechanism independent of alphavbeta3 and alphavbeta5

Endocrinology. 2007 Dec;148(12):5761-8. doi: 10.1210/en.2007-0473. Epub 2007 Sep 6.

Abstract

Cysteine-rich protein 61 (CYR61/CCN1) belongs to the family of CCN matricellular proteins. Most of the known effects of CCN proteins appear to be due to binding to extracellular growth factors or integrins, including alpha(v)beta(3) and alpha(v)beta(5). Although CYR61 can stimulate osteoblast differentiation, until now the effect of CYR61 on osteoclasts was unknown. We demonstrate that recombinant human CYR61 inhibits the formation of multinucleated, alpha(v)beta(3)-positive, or tartrate-resistant acid phosphatase-positive human, mouse, and rabbit osteoclasts in vitro. CYR61 markedly reduced the expression of the osteoclast phenotypic markers tartrate-resistant acid phosphatase, matrix metalloproteinase-9, calcitonin receptor, and cathepsin K. However, CYR61 did not affect the formation of multinucleated osteoclasts when added to osteoclast precursors prior to fusion or affect the number or resorptive activity of osteoclasts cultured on dentine discs, indicating that CYR61 affects early osteoclast precursors but not mature osteoclasts. CYR61 did not affect receptor activator of nuclear factor-kappaB (RANK) ligand-induced phosphorylation of p38 or ERK1/2 in human macrophages and did not affect RANK ligand-induced activation of nuclear factor-kappaB, indicating that CYR61 does not appear to inhibit osteoclastogenesis by affecting RANK signaling. Furthermore, a mutant form of CYR61 defective in binding to alpha(v)beta(3) also inhibited osteoclastogenesis, and CYR61 inhibited osteoclastogenesis similarly in cultures of mouse wild-type or beta(5)(-/-) macrophages. Thus, CYR61 does not appear to inhibit osteoclast formation by interacting with alpha(v)beta(3) or alpha(v)beta(5). These observations demonstrate that CYR61 is a hitherto unrecognized inhibitor of osteoclast formation, although the exact mechanism of inhibition remains to be determined. Given that CYR61 also stimulates osteoblasts, CYR61 could represent an important bifunctional local regulator of bone remodeling.

MeSH terms

  • Animals
  • Bone Resorption / metabolism
  • Cell Differentiation / drug effects
  • Cell Line
  • Cells, Cultured
  • Cysteine-Rich Protein 61
  • Humans
  • Immediate-Early Proteins / genetics
  • Immediate-Early Proteins / metabolism
  • Immediate-Early Proteins / pharmacology*
  • Integrin alphaVbeta3 / genetics
  • Integrin alphaVbeta3 / metabolism*
  • Integrins / genetics
  • Integrins / metabolism*
  • Intercellular Signaling Peptides and Proteins / genetics
  • Intercellular Signaling Peptides and Proteins / metabolism
  • Intercellular Signaling Peptides and Proteins / pharmacology*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Inbred Strains
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3 / metabolism
  • Osteoclasts / cytology
  • Osteoclasts / drug effects*
  • Osteoclasts / metabolism
  • Phosphorylation / drug effects
  • RANK Ligand / pharmacology
  • Rabbits
  • Receptors, Vitronectin / genetics
  • Receptors, Vitronectin / metabolism*
  • Recombinant Proteins / metabolism
  • Recombinant Proteins / pharmacology
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction / drug effects
  • p38 Mitogen-Activated Protein Kinases / metabolism

Substances

  • CCN1 protein, human
  • Cysteine-Rich Protein 61
  • Immediate-Early Proteins
  • Integrin alphaVbeta3
  • Integrins
  • Intercellular Signaling Peptides and Proteins
  • RANK Ligand
  • Receptors, Vitronectin
  • Recombinant Proteins
  • integrin alphaVbeta5
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • p38 Mitogen-Activated Protein Kinases