Heat shock protein 70 enhances vascular bone morphogenetic protein-4 signaling by binding matrix Gla protein

Circ Res. 2009 Sep 11;105(6):575-84. doi: 10.1161/CIRCRESAHA.109.202333. Epub 2009 Aug 6.

Abstract

Rationale: Matrix Gla protein (MGP) is a calcification inhibitor, which binds and inhibits bone morphogenetic protein (BMP)-2 and -4.

Objective: The objective was to determine whether MGP also binds other proteins, which could interfere with its function.

Methods and results: We transfected bovine aortic endothelial cells with N-terminally FLAG-tagged MGP and used immunoprecipitation and liquid chromatographic-tandem mass spectrometric analysis to identify MGP-binding proteins. Heat shock protein (HSP)70, a stress-induced protein expressed in atherosclerotic lesions and soluble in serum, was identified as a novel MGP-binding protein. The interaction between MGP and HSP70 was confirmed by coimmunoprecipitation and chemical crosslinking, and blocked the interaction between MGP and BMP-4. In endothelial cells, HSP70 enhanced BMP-4-induced proliferation and tube formation, and in calcifying vascular cells, HSP70 enhanced BMP-induced calcium deposition. In addition, HSP70 mediated the procalcific effect of interleukin-6 on calcifying vascular cells. In apolipoprotein E-null mice, a model for atherosclerosis, levels of BMP-4, HSP70, MGP, and interleukin-6 were elevated in the aortic wall. Levels of BMP-4, HSP70, and interleukin-6 were also elevated in serum, and anti-HSP70 antibodies diminished its procalcific effect on calcifying vascular cells.

Conclusion: HSP70 binds MGP and enhances BMP activity, thereby functioning as a potential link between cellular stress, inflammation, and BMP signaling.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Aorta / metabolism*
  • Aorta / pathology
  • Apolipoproteins E / genetics
  • Apolipoproteins E / metabolism
  • Atherosclerosis / genetics
  • Atherosclerosis / metabolism*
  • Bone Morphogenetic Protein 2 / genetics
  • Bone Morphogenetic Protein 2 / metabolism
  • Bone Morphogenetic Protein 4 / genetics
  • Bone Morphogenetic Protein 4 / metabolism*
  • Calcinosis / genetics
  • Calcinosis / metabolism*
  • Calcinosis / pathology
  • Calcium-Binding Proteins / genetics
  • Calcium-Binding Proteins / metabolism*
  • Cattle
  • Cell Line
  • Extracellular Matrix Proteins / genetics
  • Extracellular Matrix Proteins / metabolism*
  • HSP70 Heat-Shock Proteins
  • Humans
  • Matrix Gla Protein
  • Mice
  • Mice, Knockout
  • Protein Binding / genetics

Substances

  • Apolipoproteins E
  • BMP2 protein, human
  • BMP4 protein, human
  • Bmp2 protein, mouse
  • Bmp4 protein, mouse
  • Bone Morphogenetic Protein 2
  • Bone Morphogenetic Protein 4
  • Calcium-Binding Proteins
  • Extracellular Matrix Proteins
  • HSP70 Heat-Shock Proteins